Extrusion Design Manual
A world of opportunities
On creativity Decision by democratic vote is a fine form of government, but it’s a stinking way to create. Lillian Hellman
Success is not the result of spontaneous combustion. You must set yourself on fire. Reggie Leach
Lack of money is no obstacle. Lack of an idea is an obstacle. Ken Hakuta
Ah good taste! What a dreadful thing! Taste is the enemy of creativeness! Pablo Picasso
A good traveler has no fixed plans, and is not intent on arriving. Lau Tzu (570-490 B.C.)
Nothing Nothing encourages encourages creativity like the chance to fall flat on one’s face. James T. T. Finley
An invasion of armies can be resisted, but not an idea whose time has come. Victor Hugo
There is a fine line between genius and insanity. I have erased this line. Oscar Levant
Kites rise against the wind – not with it. Sir Winston Churchill
There is a saying among prospectors: Go out looking for one thing, and that’s all you will ever find. Robert Flaherty
Published by Hydro Aluminum — 3 rd North America Edition, 2009 Feel free to quote this manual, but please state your source! The technical information and instructions in this manual are general in nature. Hydro Aluminum does not imply or give any guarantees or accept any responsibility for the use of this information in any applied circumstance. It is incumbent on the reader to verify if the information is correct and useable and to consult with Hydro Aluminum, or other experts, before using the information in any real application.
Printed on paper containing 50% recycled content, 10% post-consumer waste
Contents click topic to go to page
Extrusion basics
Technical data
Introduct Introduction ion . . . . . . . . . . . . . . . . . . . . . . . 2
Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Commonl Commonlyy used alloys alloys . . . . . . . . . . . . . 22
From the obvious to the remark remarkable able . . . . . . . . . . . . . . . . . . . . 3 Aluminum extrusion applications applications . . . . . . 4
Corrosio Corrosion n resistan resistance ce . . . . . . . . . . . . . . . . 23 Corrosion resistance in different environments environments . . . . . . . . . . . . . 25
Aluminum Aluminum — from from bauxite bauxite to recycl recycling ing . . 6
Types of extrus extrusions ions . . . . . . . . . . . . . . . . . 26
Aluminum — the green metal . . . . . . . . . . 8
Extrusio Extrusion n design design . . . . . . . . . . . . . . . . . . . 28
Recyclin Recyclingg . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Tolerances olerances . . . . . . . . . . . . . . . . . . . . . . . . 31 Semi-hollow Semi-hollow and hollow extrusions extrusions . . . . 31 Solid Solid extrusion extrusion profile profiless . . . . . . . . . . . . . 32 Length Length tolerance tolerancess . . . . . . . . . . . . . . . . . 33 Fabrica Fabrication tion tolera tolerances nces . . . . . . . . . . . . . . 33 Precision Precision tolerance standards . . . . . . . . . 33 Useful links . . . . . . . . . . . . . . . . . . . . . . 33
The propertie propertiess of aluminum aluminum . . . . . . . . . . 10 Extrusion solutions solutions . . . . . . . . . . . . . . . . . 11 Design Design and construct construction ion . . . . . . . . . . . . 11 Extrusion Extrusion proces processs . . . . . . . . . . . . . . . . . 11 Drawn Drawn tubing tubing . . . . . . . . . . . . . . . . . . . . . 14 Surface treatment treatment . . . . . . . . . . . . . . . . . . . 15 Fabrication & contract manufact manufacturing uring . . . . . . . . . . . . . . . . . . . 16 Partner Partnering ing with with Hydro Hydro . . . . . . . . . . . . . . 17 Things to remember when ordering extrusions extrusions . . . . . . . . . . 18
Welding Welding . . . . . . . . . . . . . . . . . . . . . . . . . 46 Common aluminum welding methods methods . . . . . . . . . . . . . . . . . . . . . . 46 Friction Stir Welding Welding (FSW) . . . . . . . . 48 Machining and forming Sawing . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Deburring Deburring . . . . . . . . . . . . . . . . . . . . . . . 49 Milling Milling . . . . . . . . . . . . . . . . . . . . . . . . . 50 Drilling Drilling . . . . . . . . . . . . . . . . . . . . . . . . . 50 Turning . . . . . . . . . . . . . . . . . . . . . . . . . 50 Tapping . . . . . . . . . . . . . . . . . . . . . . . . . 51 High-perfo High-performanc rmancee machining machining stock stock . . . 51 Shearing/pressing Shearing/pressing . . . . . . . . . . . . . . . . . . 52 Thermal break . . . . . . . . . . . . . . . . . . . . 52 Bending . . . . . . . . . . . . . . . . . . . . . . . . . 53 Bending Bending methods methods . . . . . . . . . . . . . . . . . 53 CNC machining . . . . . . . . . . . . . . . . . 54 Robotic handling . . . . . . . . . . . . . . . . . 54 Contract Contract manufa manufacturi cturing ng . . . . . . . . . . . . . 55
Fabrication Joining . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Screw Screw grooves grooves . . . . . . . . . . . . . . . . . . . . 36 Bolting Bolting . . . . . . . . . . . . . . . . . . . . . . . . . 38 Snap Snap joints joints . . . . . . . . . . . . . . . . . . . . . . 39 Creating enclosures enclosures . . . . . . . . . . . . . . . . 39 Hinges . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Formed joint . . . . . . . . . . . . . . . . . . . . . 40 Butt joint joint . . . . . . . . . . . . . . . . . . . . . . . 41 Connecte Connected d extrusions extrusions . . . . . . . . . . . . . . 41 Corner joints . . . . . . . . . . . . . . . . . . . . . 41 Sleeve Sleeve joint joint . . . . . . . . . . . . . . . . . . . . . . 41 Riveting . . . . . . . . . . . . . . . . . . . . . . . . . 42 Swaging Swaging and teles telescopin copingg . . . . . . . . . . . . 42 Joining to other materials materials . . . . . . . . . . . 42 Adhesive bonding . . . . . . . . . . . . . . . . . 43
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Surface treatment treatment . . . . . . . . . . . . . . . . . . . 56 Methods Methods of surface surface treat treatment ment . . . . . . . . 56 Mechanic Mechanical al surface surface treatme treatment nt . . . . . . . . 57 Chemical surface treatment treatment . . . . . . . . . . 58 Anodizing . . . . . . . . . . . . . . . . . . . . . . . 59 Electrostatic Electrostatic painting . . . . . . . . . . . . . . . 60 Screen Screen printing printing . . . . . . . . . . . . . . . . . . . 61 AAMA finishing specifications . . . . . . . 61 Surface criteria . . . . . . . . . . . . . . . . . . . . 62 Surface Surface qualities qualities,, painted painted extrusion extrusionss . . . 62 Product Product specifica specification tion checkl checklist ist . . . . . . . . 63 Hydro Hydro plant capabilities capabilities . . . . . . . . . . . . . 64 North North American American extrusio extrusion n facilities facilities . . . . 65
Introduction O
ur Extrusion Design Manual has been written for you, the product developer, designer, design engineer, inventor, architect, buyer and anyone else involved in the design and production of products that could utilize aluminum extrusions.
The guide is divided into three parts: 1. Extrusion basics gives a broad overview of aluminum extrusion and how best to incorporate it into your product design. Hydro’s extrusion capabilities are also highlighted. 2. The Technical data section provides detailed information on aluminum alloys, types of extrusions, extrusion design issues, and tolerances. 3. The Fabrication section covers joining and other fabrication techniques, contract manufacturing, finishing,
and surface treatments. This information should help facilitate and support the development of new uses for aluminum extrusions. The Extrusion Design Manual should be a source of information and inspiration. It is the culmination of knowledge gained from over 50 years of experience in aluminum extrusion and our continued commitment to aluminum extrusion research. Here you will find practically all there is to know about aluminum
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extrusions and the design and production solutions they offer. Once you are ready to implement your design ideas, we are available to assist in getting your project off the ground. Together we can realize functional, cost-effective and profitable products! Contact any of our North American facilities directly (see inside back cover for plant toll-free numbers) or visit our website www .hydro.com/northamerica .
From the obvious to the
remarkable
A
luminum has been correctly described as “the material of opportunity” and, after steel, is the most widely used metal today. Few other materials have such a unique combination of properties — high strength and low weight, good electrical and thermal conductivity, excellent formability, good resistance to corrosion, attractive surface finish — and can be used in practically all design contexts and product applications. Furthermore, aluminum can be recycled with minimal energy consumption.
Creative design The extrusion process provides virtually unlimited design flexibility and can adapt to meet almost any design and production requirement. Functionality can be designed into the extrusion to reduce cost by using fewer components, simplifying assembly, or eliminating finishing steps. Aluminum extrusion should be considered for inspired
designs and creative technical solutions. Furthermore, the price of dies is relatively low and enhancements and modifications to dies can be quickly and easily made, facilitating prototyping.
components are increasingly being used in new applications. As a design and production material, aluminum can often provide the opportunity for designers to think along completely new lines and to extend the limits of what is possible. Aluminum extrusions are a part of everyday life. From automobiles to baseball bats, copiers to circuit-board platforms, truck cabs to cylinder blocks, aluminum extrusions can be found in a wide range of everyday products. And their uses are increasing wherever the product design can benefit from better operation, longer life, and reduced energy requirements.
Think freely! Aluminum extrusions will continue to revolutionize the way new designs and product solutions are developed. We hope that our Extrusion Design Manual will inspire new products ideas and our assistance can help get them off the ground.
Extend the limits The use of aluminum extrusions is expanding rapidly throughout the world and extruded
Think freely – think aluminum extrusions!
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Aluminum extrusion
applications
A
luminum extrusions are used in practically all businesses, products, and environments and touch people’s lives every day.
Cars, buses, trucks, trains, planes, boats Aluminum extrusions help create strong and light assemblies which are durable and provide excellent corrosion resistance. The weight reduction which results from the use of aluminum can increase load capacity and cut fuel consumption. Computers, printers, security cameras, electronics, medical equipment Fascias, frames and heatsinks are often made of aluminum extrusions. Optimal extrusion design can reduce the number of components, simplify assembly and component connections, and provide good thermal conductivity with an attractive finish.
Industrial containers, display fixtures, ramps and handrails, material handling systems Aluminum extrusions are used to develop safe and innovative designs which are strong, durable, light, corrosion-resistant, and cost-effective. Refrigerators, electrical appliances For frames, handles, trim and heatsinks, aluminum extrusions provide an attractive and easy-to-clean finish, durability, low weight and high strength. Goalposts, treadmills, baseball bats, golf carts Resilience and strength combined with low weight, formability, and surface finish are critical for performance in these applications.
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Windows, doors, storefront systems Strength, minimal maintenance, low weight, high stability, and long service life are the deciding factors when choosing aluminum building components. The building industry is one of the largest consumers of aluminum extrusions. Office equipment, furniture, lighting Modular office furniture, table frames and legs, lighting assemblies, and copier drums are examples used in the office. Strength, low weight, formability and attractive surface finishes are the most important characteristics for the choice of aluminum extrusions. Solar rooftop panels, solar arrays, mounting structures, photovoltaic (PV) panel frames Lightweight, durable, and recyclable aluminum extrusions are the ideal solution for renewable energy applications. Maybe your product will soon be on our list!
Photo courtesy of Ford Motor Company
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Aluminum from bauxite to recycling Most abundant Aluminum is the most abundant metal in nature and the third most common element in the Earth's crust after oxygen and silicon. The principle raw material in the production of aluminum is the clay soil bauxite named after the French region of Les Baux where it was first discovered. The largest bauxite deposits today are in Australia, West Africa, Brazil and Jamaica. While 8% of the Earth's crust is aluminum on average, bauxite contains 50 to 60 percent aluminum. The bauxite is converted to aluminum oxide through a cleaning process, often in plants close to bauxite mines.
Explore our value chain Primary Aluminum Production At our smelters we produce pure aluminum from alumina in electrolytic cells. Carbon cathodes at the bottom of the cells act as electrodes. The anodes, which also consist of carbon, are consumed when the anode reacts with the oxygen in the alumina and forms CO2. Liquid aluminum is tapped from the cells and cast into standard sheet or extrusion ingot, depending on how it is to be processed further. Hydro’s primary aluminum production from its 10 wholly or partly owned primary plants amounted to 3.6 billion lbs in 2008. Our own technology, developed in-house, represents an important competitive advantage.
Electrolysis Aluminum is extracted from the aluminum oxide by electrolysis (reduction). This involves dissolving the aluminum oxide in cryolite at a high temperature to form aluminum and oxygen ions. The application of a DC current in the electrolysis furnace deposits aluminum on the cathode while carbon dioxide is released at the anode. Liquid aluminum sinks to the bottom of the electrolysis cell where it is then collected for transport to a casthouse. Aluminum made from aluminum oxide via electrolysis is called primary aluminum. Extrusion billets Liquid aluminum is cleaned at a casthouse and alloying elements are added. The starting materials for future production are then made as required — extrusion billet, foundry alloys, wire rod or sheet ingots. Extrusion billet is the raw material used in the extrusion process. Logs are first cast in varying lengths and diameters prior to being cut into billets. Logs are made in a wide range of alloys and qualities to meet various product mechanical property requirements.
a
Alumina
Bauxite
b a Alumina
c
Electrical Power
The electrolytic process requires significant amounts of electrical power - 13 kWh per kg of aluminum in our most modern reduction plants. 68% of the electrical power we use comes from renewable hydroelectric power. The energy consumed in anode production is around 5 kWh per kg of aluminum.
c Efficient use of resources
Aluminum oxide, or alumina, is produced by refining bauxite and is the most important raw material in the production of aluminum. We have ownership stakes in alumina refineries in Jamaica (35 % of Alpart) and Brazil (34 % of Alunorte). Alumina from these plants covers the majority of our requirements. We purchase the remainder on long-term contracts.
b Bauxite Aluminum is the third most common element in the earth’s surface and is found in different minerals, including bauxite. Deposits are mainly located in a broad belt around the equator.
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Hydro is making determined efforts to reduce the effect that primary aluminum production has on the environment, and has achieved good results. Consumption of resources and energy has decreased, as have emissions from production.
Aluminum products last longer, weigh less and require less maintenance. Energy gains are easy to see with the use of aluminum in transportation. Vehicles with lower weights — cars, trucks, buses, trains, boats, etc. — require less fuel and can increase payloads. Aluminum and the extrusion production process are an especially powerful combination. It is possible to produce aluminum extrusions with integrated, labor-saving functions that cut costs by reducing fabrication steps and simplifying assembly.
Aluminum makes good economic sense The production of primary aluminum is an energy demanding process. But the energy used to produce aluminum’s raw material is more than compensated for by energy savings at a later stage. Aluminum can be recycled and used over and over again; the remelting process requires only 5% of the energy needed to produce primary aluminum, with no degradation in metal properties.
London Metal Exchange (LME) d High recovery rate
Enhancing The Metal’s Properties
The remelting of aluminum requires little energy, and less than 3% of the metal is lost during the remelt process. Only 5% of the energy required to produce primary metal is needed to recycle aluminum.
The inherent properties of the metal are adapted for processing and future use by the addition of small amounts of other metals to form alloys. One of Hydro’s competitive advantages is its metallurgical expertise in the interface between metal production and metal processing. In our casthouses, new and remelted aluminum is transformed into extrusion ingot, primary foundry alloys, sheet ingot, and standard ingot. The tremendous formability of aluminum, coupled with its low melting point, means that aluminum products can be shaped to match the design requirements of the end products.
d
Extruded Profiles
Remelting
Rolled Products
Our extrusion plants processed over 1 billion pounds of aluminum in 2008. Extruded aluminum has a wide range of uses in various markets including automotive, transport, and construction. Hydro’s production of profiles takes place in major plants in Europe, the US, South America, and Asia. Among other products, we supply door and window systems, as well as special products for liquid transfer and bumper beam systems for the automotive market.
In 2008, 2.2 billion pounds of aluminum were processed in our own rolling mills in Europe and Asia. Aluminum can be rolled to form super-thin, 0.007mm, gauge foil and still remain impermeable. Used as packaging material, it does not permit light to penetrate and is both odor and taste free. Other rolled-products from Hydro are lithographic plates and sheet metal for vehicles, buildings, and other applications.
Fabrication & Finishing d
Recycling Customer
7
End User
Aluminum
the green metal
A
luminum is often called the green metal because of its inherent characteristics and the ease with which it can be recycled.
Aluminum’s light weight and overall excellent in-use performance ensures that the life-cycle of many products are enhanced. The low density of aluminum benefits the transportation, aviation, and aerospace industries because lighter structural systems result in lower fuel consumption. Aluminum's low density advantage is proven in its use in power lines, in place of copper. Even though the electrical conductivity of aluminum is only about 65 percent that of copper, it is still used because of its lower weight and low cost.
Manufacturing advantages Aluminum is attractive from a manufacturing perspective, as well. It is safe to handle, will not spark and is non-magnetic. Additionally,
aluminum is one of the most cost-effective production materials. It can be extruded into a vast array of complex shapes to precise tolerances, uniform in quality, even during extended production runs. Easy-to-use, easyto-customize, with tremendous strength yet lightweight and recyclable, aluminum is the perfect material choice for product designers.
Hydro’s ecological approach Our operations, and the operations of our parent company, revolve around aluminum’s complete life cycle; from the mining of bauxite to recycling. Our approach is to take responsibility for careful raw material production, reduced emissions, and efficient use of energy.
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The systems we have in place ensure that all process waste products are sorted, recycled and re-used. All scrap metal is remelted and re-used in the extrusion process. By continually improving and increasing efficiency in production processes, minimizing emission and focusing clearly and consistently on environmental questions, Hydro supports a good, safe environment while it produces metal and extrusions. We were among the first in the industry to be certified according to ISO 14001. Additionally, we cooperate with our customers to produce better products that minimize the consumption of resources, are more economical, and environmentallyfriendly.
Recycling A
luminum is easy to recycle and can be remelted using only a fraction of the energy required to make primary aluminum.
A mere 5% of the original energy used in primary aluminum production is needed to remelt aluminum products. Recycling aluminum saves nearly 95% of the greenhouse gas emissions associated with primary aluminum production. And, aluminum can be recycled time and time again. In contrast to many other materials, aluminum's properties never change. Aluminum is, therefore, a valuable raw material regardless of where it is to be found. As society’s demand for “green” products increases, recycled aluminum will become an even more important material source. Today, aluminum is the most commonly recycled post-consumer metal in the world. Recycling aluminum makes environmental sense and it also makes good economic sense.
Hydro has the expertise and proprietary remelt technology to produce primary-grade billet with a high recycled content. Hydro has taken steps to enhance scrap conversion from its extrusion operations and has developed new methods to use difficult-to-recycle metals, such as painted aluminum.
North American activities In North America, Hydro operates the largest remelt network and is committed to recycling. We have made major investments with the construction of two standalone greenfield remelt operations (Commerce, TX and Henderson, KY) and have made significant upgrades to existing North American casthouses (Monett, MO, Phoenix, AZ, and St. Augustine, FL). In total, Hydro has more
Recycling changes the picture Emissions per metric ton of product Primary based
Recycling based
CO2 /mt
CO2 /mt aluminum product equivalent
aluminum product equivalent
11.4 Energy savings with aluminum recycling
4 1.4 - 1.6
0.7 Aluminum global average
Steel
Aluminum global average
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Steel
than 750 million pounds of remelt casting capacity in the U.S. In 2008 Hydro used more than 200 million pounds of recycled aluminum in the production of primary-grade billet which, on average, contained at least 70% recycled material. The recycled aluminum came from both internal and external sources including special arrangements with our extrusion customers. This helps our customers achieve their recycling goals and allows us to procure scrap with known alloy compositions.
The properties of
aluminum
A
luminum has a unique and unbeatable combination of properties that make it versatile, highly effective and attractive for a vast array of applications.
Weight - Aluminum is light with a density one third that of steel (0.097 lbs/in 3). Strength - Aluminum is strong with a tensile strength of 10 to 100 KSI, depending on the alloy and manufacturing process. Extrusions of the right alloy and design are as strong as structural steel. Elasticity - The Young's modulus for aluminum is a third that of steel (10,008 KSI). This means that the moment of inertia has to be three times as great for an aluminum extrusion to achieve the same deflection as a steel profile. Formability - Aluminum has good formability, a characteristic that is used to the fullest extent in extruding and facilitates shaping and bending of extruded parts. Aluminum can also be cast, drawn, and milled.
Machining - Aluminum is very easy to machine. Ordinary machining equipment such as saws and drills can be used along with more sophisticated CNC equipment. Joining - Aluminum can be joined using normal methods such as welding, soldering, adhesive bonding, and riveting. Additionally, Friction Stir Welding (FSW) is an alternative in certain applications. Corrosion resistance - A thin layer of oxide is formed in contact with air, which provides very good protection against corrosion even in extremely corrosive environments. This layer can be further strengthened by surface treatments such as anodizing or powder coating. And corrosion resistance can be enhanced through alloy selection.
Thermal conductivity - Thermal conductivity is very good even when compared with copper. Furthermore, an aluminum conductor has only half the weight of an equivalent copper conductor. Electrical conductivity - When compared to copper, aluminum has good electrical conductivity and yet weighs half as much as copper. Linear expansion - Aluminum has a relatively high coefficient of linear expansion compared to other metals. This should be taken in account at the design stage to compensate for differences in expansion. Non-toxic - Aluminum is not poisonous and is therefore highly suitable for food preparation and storage applications.
Reflectivity - Aluminum is a good reflector of light and heat.
Aluminum’s physical properties compared to other materials Steel
Aluminum
Copper
36/40
36/40
42/57
7/10
15
25
36
25
Elasticity E, Young’s module (KSI)
10008
18130
30000
435
3
Density (lbs/inch )
0.097
0.32
0.28
0.05
Melting point ( °F)
1220
1980
2750
180
-400 to +300
-300 to +550
-60 to +950
-300 to +180
Electrical conductivity (m/Ohm-mm )
29
55
7
—
Heat conductivity (W/m °K)
200
400
76
0,15
Coefficient of linear expansion (x10 / °F)
10.9
7.7
6.3
27 - 45
Non-magnetic
Yes
Yes
No
Yes
Weldable
Yes
Yes
Yes
Yes
Strength/Fracture strength (KSI) Ductility/Elongation (%)
Working temperature range ( °F ) 2
-6
10
(AISI 1020)
Plastic
Extrusion
solutions
Design and construction The whole manufacturing and production process starts with extrusion design. It is here that the extrusion takes shape and features are built in for easier connection, minimal finishing work, and simpler assembly. We can also take advantage of all the benefits of aluminum and the extrusion process and make products with optimal function and an attractive appearance which are also cost effective.
We have the resources to help you at the design and development stages. Our plant engineers, along with the available assistance from Hydro’s Technology Center in Holland, Michigan or our European competence centers, can help achieve an optimal extrusion design for your product. We can create the exact solution you require, testing ideas by using advanced 3-D CAD systems. All without the need to produce a single die or prototype extrusion.
Extrusion process Raw material The starting material for making an aluminum extrusion is an aluminum log that is cast either from primary aluminum or recycled aluminum. Logs are cast in lengths of up to 24 feet and are available in a wide variety of alloys and dimensions to suit specific needs and requirements. The most common extrusion log is 7" to 12" in diameter and billets are typically cut into 18" to 40" lengths, depending on the capacity of the press and the required length of the finished extrusion.
Extrusion Extrusion involves pressing a preheated aluminum billet (850°F - 950°F) under high pressure (1600 - 6500 tons, depending on the
size of the press) through a die, the opening of which corresponds to the cross-section of the extrusion. The extrusion press speed (normally 15 - 150 ft/min) depends on the alloy and the complexity of the shape.
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Extrusion process employs large forces, 1600 – 6500 tons, depending on the size of the press
Cooling and stretching The main parts of the press are the container, where the extrusion billet is placed under pressure, and the main cylinder with piston that presses the material from the container through the die and die holder. The extrusion process is shown in the photo illustration below. When the extrusion leaves the press it moves onto a table where it is cooled with air or water depending on its size, shape, the alloy, and properties required. To get straight extrusions and eliminate any residual stress in the material, they are usually stretched approximately 1%.
Cut-to-length and heat treating After cooling and stretching, the extrusions are cut into suitable lengths and artificially aged to achieve the right strength. Aging generally takes place in ovens at about 375°F for 4 to 8 hours. This is followed by a final check and the extrusion is ready for machining or delivery to the customer.
A heated aluminum billet is pressed through a die, the opening of which corresponds to the cross-section of the extrusion
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Hollow dies or solid dies Dies are divided into two groups; those for solid extrusions and those for hollow extrusions. The dies for solid extrusions consist of a flat plate which forms the external shape of the extrusion. The dies for hollow extrusions consist of two parts: a port through which aluminum flows and a mandrel over which the aluminum re welds to form the extrusion's outside surface. As many as ten or more extrusions, depending on size, can be extruded in multicavity dies.
The dies are made of high temperature resistant tool steel and the die's opening is made by wire erosion in CNC controlled machines. Occasionally, open extrusions have a design that makes the use of a flat die inappropriate. A die with a deep tongue and a narrow gap will not withstand the extrusion pressure. Therefore, the die will be designed with a mandrel to support the tongue even though the extrusion is open. Sometimes this die design is called a "semi-hollow".
Low costs Dies for aluminum extrusions typically cost significantly less than the tooling required to make components from other materials like steel and plastic. Low die costs and rapid die development times make aluminum extrusion all the more viable for the production of prototypes.
Solid, single-cavity, die
Dies for hollow extrusions
Four-cavity die for simultaneous extrusion of four profiles
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Dra wn
tubing
T
he drawn tube process provides exceptional dimensional control and superior surface finish. Drawing enhances bending, flaring, and formability. Typical product applications include photocopier tubing, tent poles, antennas, extension poles, golf ball retrievers, etc. Drawn tube process
A drawn tube is a tube which is brought to final dimension by drawing through a die. It is produced from extruded bloom ( seamless or porthole) or welded tube bloom stock. Drawn tubing increases mechanical properties and further refines grain structure and can be produced in thin gauges, below what can be done using only the extrusion process. In addition to adding strength, the drawing process provides exceptional dimensional control and a superior surface finish that would not be attainable in an extruded product of the same alloy and size. Drawing also enhances bending, flaring, and formability. Ovality can be controlled more precisely in the drawing process than in the extrusion process. Because the process involves cold work, drawn tubing is suitable for non-heat-treatable as well as heat-treatable material. Shaped drawn tubing (non-circular) is made by first reducing a bloom in the round to the necessary diameter and thickness, and then drawing it through a shaping die to form the final profile.
Typically, a drawn tube starts out either as a seamless or porthole extruded tube (bloom). Seamless tube is produced using hollow billet and an internal mandrel to form the inside diameter (ID) surface. Or, using solid billet, a hole is pierced in center to form the ID surface. There are no internal weld seams. Porthole tube is produced using porthole, bridge, or spider type dies. An internal mandrel is used to form the ID surface which is supported by a die steel bridge network. Internal weld seams (hot fusion welds) are present. Pointing All drawn tube requires a point on one end which is used during the drawing process as the portion which is grasped and pulled through the die by the draw bench carriage jaws. These points are proportionately smaller that the outside diameter of the tube and sized according to the draw bench assigned and are discarded as process scrap.
Drawing Drawn tube obtains its mechanical properties, characteristics, and dimensions by drawing an extruded tube, or bloom, through a die over a mandrel. This is then reduced by a series of passes on a draw bench. The reduction process consists of gripping the tube by its “tagged” end and drawing it through a die. The outside diameter (OD) is defined by the die, and the ID by a plug carried on a long rod passing back through the tube.The process is relatively labor intensive as it has to be done length by length. For some applications, it is possible to draw coiled tube in long lengths using a floating plug. Straightening Depending upon the end use and/or customer requirements, the material is then placed through a series of rolls and straightened. This process essentially corrects for tube bow over the length of tube. Some tube manufacturers use stretching in place of, or to complement, roll straightening.
Cold drawn process Pointed Tube Reducing Die
Hot Rolled Tube Hook
Stationary Mandrel Reducing Die
Cold Draw Bench
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Reduced Diameter and Wall Reduction
Tube Gripped at End and Pulled Through Die
Surface
treatment
I
n its natural state, aluminum has a clean and attractive surface with good corrosion resistance. There are a number of surface treatments that can additionally improve resistance to corrosion and mechanical wear. They also provide a decorative appearance or, in other ways, alter the surface properties.
Anodizing Anodizing is an electrochemical process that thickens the oxide film on the aluminum surface. The process involves connecting DC current to an extrusion, which acts as an anode (hence the name), and placing the extrusion in an electrolyte bath. While the natural oxide film is only .00008 of an inch thick, anodizing increases the oxide layer to between .0002 and .001 inches, depending on the product characteristics required. With the anodizing process, aluminum's natural color (naturally anodized) can be retained or a color from a wide range of options can be chosen. Special techniques include clear "no-burn" anodizing for components that need to be welded after anodizing such as those used in marine applications.
Powder coating Powder coating offers a virtually unlimited choice of colors and is very durable.
Liquid paint High-solid polyester, as well as textured and skid-resistant paints, can also be applied.
Mechanical surface treatments Grinding, polishing, knurling and barrel processing are examples of mechanical surface treatments which can improve both material performance and appearance.
Other surface treatments These include screen printing and the use of protective foils. For more information, see the Surface Treatment discussion in the Fabrication section, page 56.
15
Fabrication &
contract manufacturing
A
luminum extrusions can be designed to minimize the need for further processing, making assembly and final production easier and more efficient. Nevertheless, extrusions often require some type of subsequent fabrication. Surface treatments and simple fabrication operations, like cutting and punching, are common. Even complex machining, fabrication and contract manufacturing services are frequently required. Fabrication
Fabrication processes range from the simple to the complex. Basic fabrication can include cutting, drilling, punching, bending, stamping, and the like. Multi-stage fabrication procedures can feature robotic welding as well as mechanical fastening. At all North America locations (see inside back cover), Hydro offers a full array of fabrication services for small- and large-scale assemblies. These are further supported by value-added services such as process engineering, warehousing, and JIT delivery to meet today’s stringent requirements for inventory management.
Contract manufacturing Companies may outsource a portion of their own manufacturing processes to free up resources, time and capital and focus on core
competencies. In doing so, they look for partners who can manage everything including raw materials sourcing, production, warehousing, and delivery. Hydro’s own contract manufacturing services include process development, sourcing of components, assembly services, and completion of Production Part Approval Processes (PPAP) and Advanced Product Quality Planning (APQP). Further, we will develop new technology, expand plant capacity, or make additional investments, as required, to advance the process.
Additional services Additional services offered by Hydro, and some other companies, include metals sourcing, engineering design, prototype development and testing, component sub- and full-assembly, warehousing, and JIT delivery.
16
Fabrication services Hydro offers basic fabrication services and multi-stage fabrication for components and assemblies including the following: Machining • Cut-to-length • Mitering • Deburring
• Drilling • Turning • Milling
Forming & bending • Stretch forming • Roller bending • Press bending • Punching • Stamping Joining • Adhesive bonding • Bolting • Riveting • TIG welding • MIG welding • Robotic welding • Friction stir welding CNC (tight-tolerance) machining • Drilling • Milling • Notching • Tapping • Lathing • Countersinking Surface treatments • Anodizing • Painting • Mechanical surface treatments
Partnering with
Hydro
W
e are here to help you realize the perfect extrusion solution which meets your need for performance, quality, precision, and economy. The earlier we get involved in the development process, the sooner you will be able to access our experience, skills, know-how, and resources. Here is a short guide to make your extrusion planning and your first contact with us easier.
Draw up a specification of requirements The more prepared you are when you contact us, the better. We will then be able to give you more relevant advice quickly. It’s a good idea to go through the different sections of this Extrusion Design Manual and draw up preliminary specification requirements or a "shopping list" for your project. Review the Product specifications checklist on page 63 for a list of sample questions to consider.
Attend an Extrusion Academy Hydro offers this educational program which includes formal presentations, open discussion, and group workshops whose goal is to instill a deeper understanding of aluminum extrusion design issues and manufacturing techniques.
Good relationships
Can my product be made of aluminum? This is a fundamental question. For instance, can a boat hook be extruded or is drawn tubing a better option? We are happy to
answer your questions about aluminum and aluminum extrusion options and put you on the right track from the very beginning.
Need help with drawings, product development, design, production? You've got an idea! Maybe preliminary drawings. Or you have a drawing that needs to be optimized, but you're not quite sure how to go forward? Contact us and we'll get things moving!
What does it cost? We can give you a good idea of the costs involved for dies and extrusion, fabrication and surface treatments, even at the concept stage.
17
Good and lasting relationships with our customers are the very foundation of our business. By getting to know your business and your products well, we increase the possibilities of achieving mutual success.
Contacting us Our sales staff is ready to serve you. Contact your local plant (see inside back cover of this manual for contact information).
Things to remember when
ordering extrusions
O
ur Extrusion Design Manual provides a range of issues and variables to take into account when designing products using aluminum extrusions. All should be considered in order to achieve better product performance and economy.
Surface requirements
Technical cooperation
Fabrication
We can act as both your extrusion supplier and your product development partner. Contact us at the product design stage so that we can develop an extrusion, fabrication, and finishing solution that offers the best performance and economy.
One-stop-shop Take advantage of Hydro's special skills and free up internal resources for other tasks. With Hydro, you gain access to a partner that takes total responsibility for solving your extrusion, processing, and surface treatment requirements. This can be both a time saving and economical alternative to in-house production.
Alloys
Not all extrusion surfaces need to be of the highest quality. There is no doubt that the surface demands for an extrusion used in a truck frame assembly are different from those that are part of modular office furniture panels. The right finish for the right application saves money!
Choose the right alloy to meet the required characteristics and performance of the product. There is no need to use a more expensive and difficult-to-extrude alloy if your product does not require it.
An increasing number of extrusions are machined into finished components. Fabrication tasks can be minimized if fabrication needs are considered in the early design stages.
Optimal design
Correct quantity
Study the advice and tips in this Design Manual. Creative extrusion design with builtin functionality can simplify the next stage of production and reduce cost.
Optimize your order quantities and extrusion deliveries. Small volumes usually mean higher costs.
Optimizing materials
Aluminum is a valuable raw material which can easily be recycled. We recycle all waste from production and can also take your production waste and recycle it effectively.
Materials can be optimized using creative design even in extrusions with high-strength requirements. Put the material where it is needed and avoid making the extrusion heavier and more expensive than is necessary!
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Recycling
Technical data
Alloys
The choice of material is a critical decision in all
opportunities and forms the basis for product
product development. Aluminum can give a product suitable physical and mechanical properties and, at the
improvement. Pure aluminum is only used in a limited way
same time, help achieve an aesthetically attractive appearance. Furthermore, the extrusion process,
commercially. The majority of extrusions are made from aluminum alloyed with other elements. The most
combined with the right alloy and proper thermal
common elements used are magnesium (Mg), silicon
treatment, offers an infinite number of application
(Si), manganese (Mn), zinc (Zn) and copper (Cu).
Most aluminum extrusions are made from the alloy series listed below: 1000 series 3000 series 5000 series 6000 series 7000 series
AI
Al Al + Mn Al + Mg Al + Mg + Si Al + Zn + Mg
+
Zn Zinc
Cu Copper
The 1000 series is non-heat-treatable. These alloys are often selected for products where high thermal and electrical conductivity are desired. They have low strength. The 3000 and 5000 series are non-heat-treatable. 3000 series is often used in drawn tubing for highly ductile applications and printer components. The 5000 series is mostly used in extremely corrosive environments such as marine. The 6000 and 7000 series are heat-treatable. They are the most commonly used extrusion alloys and have a wide range of applications.
Mg Magnesium Increased strength and hardness. Good corrosion resistance, increased weldability.
Si Silicon Gives heat treatable alloys when combined with Mg. Good corrosion resistance.
Increased strength and hardness. Possibility for stress corrosion. Gives heat treatable alloys when combined with Mg.
Gives heat treatable alloys. Gives increased strength and hardness. Reduced resistance to corrosion.
Mn Manganese Increased yield and tensile strength. Good resistance to corrosion.
Properties that can be achieved when alloying with other metals
6000 series
and at sea — is made from this series. Among the 6000 series, the 6060 alloy offers low to medium strength and is easy to extrude even for complicated cross-sections. It has good formability during bending in the T4 condition. This material is highly suitable for anodizing, both for decorative and protective reasons. The 6063 alloy has slightly higher strength than 6060, but is also marginally more difficult to extrude, especially if the cross-section is complicated. This material is also well suited for anodizing, both for decorative and protective purposes. For bright surface finish applications, 6063 is substituted by 6463.
The 6000 series has good extrudability and can be solution heat-treated during hot working at the extrusion temperature. Solution heat treatment enables some of the alloying elements, such as Mg and Si, to go into solid solution and maintained in a supersaturated state on quenching. This homogenous material is subsequently age hardened to obtain the required mechanical properties. The 6000 series alloys are termed “soft alloys”. They are easy to weld and offer good resistance to corrosion, even in marine environments. The bulk of extruded materials for load bearing applications — both on land
20
Hydro recently developed a new alloy that falls into the 6060 category. This new alloy improves manufacturability while delivering the same performance as other 6060 and 6063 alloys. It is perfect for complex extrusions, allows for better surface finishes, and is an excellent alternative to some 6063 solutions. The 6005A alloy has higher strength than 6063 but is slightly harder to extrude. 6005A is relatively less ductile than 6060/6063 alloys in the heat-treated condition. It is suitable for anodizing for protective purposes but the quality of the surface makes decorative finishing more difficult. 6105 is an alloy of similar chemical composition to 6005A but is considered less robust for demanding medium-strength applications. 6061 and 6082 alloys provide high strength and are suitable for extrusion of cross-sections that are not too complicated. With its superior material performance characteristics, 6082 can often replace 6061. The material is suitable for anodizing for protective purposes.
Alloys/Typical Applications 1000 Series
Applications which require formability and high thermal conductivity
3000 Series
Printer drums, automotive heat transfer components
5000 Series
Marine, extremely corrosive environments
6000 Series 6060/6063
Windows and doors, lighting, awnings, handrails, furniture Structural components in transportation, boat masts Load bearing structures: platforms, bridges, stairs, scaffolds, handrails Electrical conductor (bus bar, etc.)
6005A/6105 6061/6082 6101
Load bearing automotive parts, aircraft containers, bicycle frames, high-speed boats
7000 Series
3000 and 7000 series Of the non-heat treatable alloys, 3003 is extensively used in the tubing industry. 3003 alloys have moderate strength (less than 6000 series), high ductility, and excellent corrosion resistance. The 7000 series has the highest strength of the most-used alloys. It has good weldability and provides lower reduction of strength in heataffected zones than the 6000 series. Its corrosion resistance and formability are, however, not as good as those in the 6000 series. But by adding small amounts of Zr, Cr, or Mn, this can be improved.
In general, the 6060, 6063, 6005, 6061 and 6082 alloys should not be used in structural applications which experience temperatures above 250°F. The tensile strength decreases as the temperature increases while elongation before fracture usually increases. If the designer is unfamiliar with the exact temperature characteristics for a given alloy, it can be assumed as a starting point that properties such as shear, and fatigue strength vary in proportion to the tensile strength.
Temperature – mechanical properties Care should be taken when using aluminum at high temperatures. Mechanical properties can be significantly reduced at temperatures above 250°F, especially if the material has been thermally hardened or cold worked. Fortunately, extended exposure above 250°F is rare in general extrusion applications. When such exposure is anticipated, ensure that the component is not structural or load bearing. For such applications, specialty alloys in the 3000 or 7000 series should be considered.
Low temperature properties In contrast to steel, aluminum alloys do not become brittle at low temperatures. In fact aluminum alloys increase in strength and ductility while impact strength remains unchanged. As the temperature decreases below 32°F, the yield strength and tensile strength of aluminum alloys increase.
Typical conditions on delivery* F
Extruded and air cooled
O
Softened, annealed at 660-930ºF, for 1-5 hours
T4
Solution quenched and naturally aged at 70 ºF, for 5-10 days
T6
Solution quenched, artificially aged
6105 6005A 6061
*Contact your extruder or the Aluminum Association for a complete list of temper designations and condition standards
As seen above, some alloy groups overlap. Although different in name, chemical composition and properties can be the same or similar. 6060 and 6063 are lower strength alloys of comparable performance. 6105 and 6005 are similar, medium-strength alloys. 6061 and 6082 are high-strength structural alloys.
21
Commonly used alloys 3003
6060
6063
6105
6005A
6061
6082
Condition Yield strength, KSI
Tensile strength, KSI
O
5
F
10
16 max
T4
10
14
T6
28
32
O
14
F
17
15
10
14
18
35
35
42
22 max
T4
22
28
T6
31
36
T4
23
24
T6
10
10
T4
43
47
T6
67
81
.098
.098
.098
10,000
10,000
12.9E -6
13.0E-6
Thermal conductivity 20 F (W/mK)
193
200
200
218
200
180
180
Electrical conductivity % IACS
43
52
52
57
52
46
46
1180-1210
1112
1211
1148
1139
1076
1202
6060/63
6063 A
6105
6005A
6061
6082
Elongation, A5 % Brinell hardness, HB Density (lbs/inch3 ) Young’s modulus (KSI) Coefficient of expansion 70-200 F (inches/inch/ F) °
°
°
Melting point ( F) °
EN-AW
25
16 47
23
26
32
38
38
45
22
16
20
8
8
10
47
65
92
100
100
.098
.098
.098
.098
10,000
10,000
10,000
10,000
10,000
13.0E-6
13.0E-6
13.0E-6
13.1E-6
All values from Aluminum Association (AA) Standards & Data 2006.Values for the mechanical properties can vary for different process parameters. Higher property levels can be achieved in most areas and can be guaranteed provided a special agreement is reached.
Brinell
Vickers
Rockwell ’F’
Rockwell ’E’
Rockwell ’B’
Rockwell ’K’
Webster Hardness number
The relationship between some accepted methods for measuring hardness
22
12.8E-6
Corrosion resistance
One of the principal reasons for choosing aluminum
surface. Generally, this film is stable in aqueous
for structural applications is aluminum’s high
solutions with pH 4.5-8.5. Further considerations
corrosion resistance. Although aluminum is a
need to be made if the pH exceeds these limits or if
chemically-active metal, its behavior is stabilized by the formation of a protective oxide film on the
the environment contains chloride.
Although generally very stable, aluminum alloys can experience certain types of corrosion as summarized below:
Uniform attack Corrosion proceeds homogeneously over the whole surface of the metal. With aluminum alloys this type of corrosion is mainly seen in very alkaline or acid environments where the solubility of the natural oxide film is high.
Pitting corrosion Pitting corrosion is the most common type of corrosive phenomena with aluminum alloys and is characterized by local discontinuities in the oxide film (i.e. locally reduced film thickness, rupture, localized concentrations of impurities/alloying elements, etc.) Aluminum is sensitive to pitting when chloride ions are present (e.g. sea water). Pits develop at weak spots in the surface films and at places where the oxide film is mechanically damaged. Pitting can penetrate several millimeters during a short period of time if the conditions are extremely poor. The pits can be of different shapes, wide or narrow. Narrow pits are undesirable since the pits could be deep and difficult to detect. Choosing the right alloy and proper surface treatment (e.g. anodizing, powder coating or electrostatic painting) are two ways to limit or prevent pitting corrosion. Frequent cleaning, as well as ventilation of tight assemblies and a profile design which reduces the accumulation of stagnant water, are also recommended.
This situation may, for example, develop as a result of slow cooling after extrusion. In this case, the grains will be larger and the inter-metallic particles will precipitate on the grain boundaries, thus increasing the difference in corrosion potential between the grain boundaries and the interior of the grain. Due to low metal consumption, inter-crystalline corrosion is difficult to detect visually and even more difficult by measuring weight loss. However, if the corrosion is permitted to propagate into the metal, the mechanical properties of the material will severely deteriorate. Alloys in the 6000-series are normally resistant against IGC, although this is dependent on the chemical composition. Recrystallized structures which already have a high content of Si or Cu, may allow corrosion of this type. Addition of Mn or Cr will prevent or minimize recrystallization. One way to prevent IGC is to choose the right alloy. Other preventative actions are mentioned under "Pitting corrosion."
InterGranular Corrosion (IGC)
Crevice corrosion
IGC is selective corrosion around the grains and in the adjacent zones without any appreciable attack on the grain itself. The reason for IGC is a difference in corrosion potential between grain boundaries and the bulk of the immediately adjacent grains. The difference in potential may be caused by the difference in chemical composition between the two zones.
Crevice corrosion may occur in narrow crevices filled with liquids like water. Use of a sealant prior to joining may prevent moisture penetration. A good extrusion profile design will minimize the risk of crevice corrosion.
23
insulated. It is very important to use insulation material of proper electrical resistance and to avoid metallic contact in the entire construction. This can be checked with resistance measurement instruments such as a multimeter. Aluminum may also be protected by means of sacrificial anodes. The most cathodic material can be surface treated with a metallic coating (Al/Zn), organic coating (lacquer, paint, plastic, rubber) or a special coating for screws and bolts. Surface treatment has to be carried out correctly and not done only on the anodic material. As a consequence, a defect in the surface coating may generate a very unfavorable cathode/anode ratio (a big cathode area in relation to a small anode area gives considerable corrosion). Galvanic corrosion in combination with crevice corrosion may be especially damaging. Avoid entrapment of liquids in crevices between materials of various galvanic potentials. Also avoid the transfer of ions of galvanic materials on aluminum surfaces. For instance, droplets from a copper tube on an aluminum surface will generate precipitation of copper metal. The result is corrosion of aluminum (deposition corrosion). The next step will be microgalvanic corrosion between aluminum and the copper particles in the aluminum surface. Severe pitting may occur within a few weeks.
Water staining Water staining is a type of crevice corrosion and is caused by water or moisture trapped between, for example, dense stacked profiles. Water staining is a very common corrosion type. Appearance varies from iridescent in mild cases, to white, grey or black in more severe instances. Water staining is normally removed by grinding or painting. Because of the risk of condensation, profiles without any surface treatment should never be stored outdoors, even though plastic wrapping is used. Store extrusions in places with a relative humidity of 45% maximum, and a maximum temperature variation of +/-40°F. During transportation from a cold to a warm area, the temperature should be increased gradually to avoid condensation.
FiliForm Corrosion (FFC) Filiform corrosion on passivated surfaces shows itself as thin, threadlike and shallow attacks progressing below surface layers like paint. The corrosion normally starts in coating defects (e.g. on miters) and follows certain directions, such as the extrusion direction. The initial attack is facilitated by moisture which penetrates the surface layer and becomes depleted of oxygen making the area anodic. FFC is mainly an aesthetic problem, but it may cause deformation in narrow crevices or delamination of surface treatments. An extensive FFC attack seen during corrosion testing can be attributed to a reactive uppermost surface region showing an unpredictable chemical composition, which may be formed during thermo-mechanical transformation of the alloy. It has been shown that sufficient metal removal of aluminum 2 g/m 2 by chemical etching prior to properly performed chromating is needed to reduce FFC potential. Providing this is done properly, aluminum extrusions in 6060/6063 will exhibit high FFC resistance.
Galvanic corrosion Galvanic corrosion occurs when two metallic materials are in contact in the presence of an electrolyte forming a galvanic cell. The least noble material (the anode) preferentially corrodes while the more noble material (cathode) is protected. Since aluminum is more anodic than most commonly used construction materials, with the exception of zinc, magnesium and cadmium, this can be a serious form of corrosion with aluminum. Coupling aluminum with a more noble material can seriously deteriorate the protective effect from the oxide layer. This is especially dangerous in atmospheres or water with high concentrations of chlorides or other aggressive corrosives. Most types of aluminum corrosion are the result of some kind of galvanic coupling with a dissimilar material. Galvanic corrosion can be avoided or minimized by taking the following actions: Avoid using materials with large galvanic potential differences in a particular environment (stainless steel not included). If that is not practical, different materials have to be properly electrically
24
Corrosion resistance in different environments
The atmosphere
Acids
Corrosion is insignificant in fresh, unpolluted air. Aluminum does not corrode where there are high levels of sulphur dioxide but can, under certain circumstances, become dark or matte in appearance.
The majority of inorganic acids have a very corrosive effect on aluminum, except nitric acid. High temperature, high acid concentrations and high levels of impurities in the aluminum increase the rate of corrosion significantly.
Water
Alkalis
Pitting can occur in stagnant water. The composition of the water is the important factor as the presence of copper, calcium, chloride and bicarbonate ions increase the risk significantly. This can be prevented by regular cleaning and drying.
Strong alkalis are very corrosive. Sodium hydroxide reacts violently with aluminum. The rate of corrosion can be reduced in environments where the pH is between 9 and 11 by using silicates. Wet cement has a high pH and therefore corrodes aluminum alloys.
Seawater
Organic compounds
Alloys containing silicon, magnesium and manganese show good resistance to corrosion in seawater. Copper alloys, on the other hand, should be avoided.
Aluminum is highly resistant to the majority of organic compounds. Corrosion can occur, however, with certain anhydrous liquids.
Soil
Other materials
The resistance to corrosion is, to a great degree, dependent on the moisture in the soil and its pH level. Aluminum surfaces which may come into contact with soil are best treated with a thick layer of bitumen or a powder coating.
In practice, the corrosion problem caused by contact with other materials is, for the most part, small. The natural oxide layer usually provides sufficient protection.
25
Types of extrusions
There are three types of extrusions:
The relationship between the cross-sectional area of
• Solid extrusions without cavities
the opening and the square of the opening in the
• Hollow extrusions with cavities
extrusion hole determines whether the extrusion is
• Semi-hollow extrusions
semi-hollow or not.
Extrusion dimensions The Diameter of the Circumscribing Circle (DCC) is a measure of the extrusion's size and therefore determines the material thickness, tolerances and cost to produce. Below are the measurement limits within which Hydro’s North American operations can supply aluminum extrusions based on the DCC.
11"
2"
8"
Solid extrusions The diagram shows the range of maximum dimensions for a solid extrusion.
Hollow extrusions According to the diagram the following applies for open extrusions: Square tube maximum: 8" x 8" Rectangular tube maximum: 11" x 2" Round tube max diameter: 8"
The maximum sizes can vary depending on the alloy, material thickness, complexity and tolerances. Please contact us for shape and size limits. In North America, Hydro makes extrusions weighing from 0.1 lb/ft up to 14 lbs/ft., with the maximum weight of most extrusions below 7-8 lbs/ft.
26
Hollow extrusions A shape is described as a hollow if a completely enclosed void exists anywhere in its cross-section.
Steering column electronics bracket for full-size pick-up trucks and SUV’s
Nine-void extrusion used to form lightweight weblike truss system
Multiple extrusions snap together to form escalator and elevator treads
Semi-hollow extrusions A shape is described as a semi-hollow if a partially enclosed void exists anywhere in its cross-section. The area of the void must be substantially greater than the square of the gap’s width.
One of four extrusions which, joined together using friction stir welding, create an AC motor cover
Extrusion used for side frame of commercial-grade treadmill
Aluminum extrusion track nailed to bottom of wood planking to hold water heating pipes
Solid extrusions The shape is described as a solid if it does not have voids and is neither a hollow nor semi-hollow.
Supercharger design for automotive engines that features twin four-lobe rotors, twisted 160 degrees
Engine fan shroud formed from a solid lineal extrusion using a unique roll bender
27
Two curved gearlike extrusions interweave within a third extruded housing to form unique hinge
Extrusion design
If you are involved with the development of new
concepts will help you achieve extrusions with better
products and improvement of existing products, aluminum extrusion provides virtually unlimited
functionality and extrudability and, consequently, lower production costs and improved all-around
design opportunities.
economy.
To achieve a successful product design, an
The following pages provide information to help
understanding of some basic extrusion design
with your design process. Contact us if you need
concepts could be very useful. Applying these
additional assistance.
Uniform wall thickness
Symmetry
Uniform wall thickness within a section reduces the load on the die and minimizes the risk of damage to the die. Major differences in wall thicknesses within a section should also be avoided in order to minimize differences in surface appearance after anodizing. Uniform wall thickness can be obtained by changing the shape of the extrusion and putting material where it is needed most.
With symmetrical extrusion designs, a balanced flow of material through the die is achieved. At the same time, the load on the die is evenly distributed. The extrusion shape is, therefore, more accurate while the risk of damaged dies is significantly reduced.
Rounded shapes
The Diameter of the Circumscribing Circle (DCC)
As a rule, all corners should be rounded. Normal radii are .016" to .040". If the design requires sharper edges and corners, a radius of .008" is the smallest that can be effectively produced.
Always try to reduce the circle circumscribed around the extrusion. Apart from making the profile easier to extrude, this also helps keep die and production costs down.
28
Simplify and facilitate Here are some examples of design changes that have no impact on the function of the extrusion, but which simplify and facilitate production thereby lowering production costs and improving cost efficiencies.
Fewer cavities cut costs
For certain applications, converting to a hollow extrusion can increase strength and provide better dimensional control
Increased size can cut weight and increase rigidity
Heatsinks
Decorative lines
Incorporating flanges in the design increases the surface area of the extrusion and improves thermal conductivity.
Decorative lines in an extrusion can conceal irregularities as well as protect against damage during handling and fabrication.
29
Minimum material thickness Wall thickness
.200 .190 .180 .170 .160 .150 .140 .130 .120 .110 .100 .090 .080 .070 .060 .050 .040
6063 alloy, hollow extrusion 6061 alloy, hollow extrusion
6063 alloy, solid extrusion 6061 alloy, solid extrusion
0
0.8
1.6
2.4
3.2
4.0
4.8
5.6
6.4
7.2
8.0
8.8
9.6
10.4 11.2 12.0 12.8 13.6
Circumscribing circle
Recommended minimum material thickness (in inches) in relation to the circumscribing circle diameter (in inches)
Gap depth – gap width
Maximum ratio between the gap height (h) and the gap width (b) in solid extrusions Gap width (in) "b"
Ratio "h:b"
< .040 .040 - .080 .080 - .120 .120 - .160 .160 - .200 .200 - .600 .600 - 1.200 1.200 - 2.00 2.00 - 3.20 3.20 - 4.80 > 4.80
1.0 2.0 2.5 3.0 3.5 4.0 3.5 3.0 2.5 2.0 1.5
Maximum ratio between the gap height (h) and the gap width (b) in solid extrusions.
Surface – gap width
Maximum ratio surface-gap width Gap width (in) "b" .080 - .120 .120 - .200 .200 - 2.00 2.00 - 3.20 3.20 - 4.80 > 4.80
Surface ratio "A:b 2 " 2.0 3.0 3.5 3.0 2.0 1.5
The maximum ratio surface – gap width.
30
Height – width
Height-width ratio for hollow extrusions
Gap width (in) Ratio "b" "h:b" 2.40 - 4.00 4.00 - 8.00 8.00 - 12.00
3 max. 5 max. 6 max.
Height – width ratio for hollow extrusions
Tolerances
The tolerances provided here are a sampling of those
Standards, apply unless otherwise stated. For more
that apply to the most common types of extrusions.
information, please see The Aluminum Association’s
Lower or tighter tolerances can often be achieved.
reference manual, Aluminum Standards and Data, or go
Tolerances according to Aluminum Association
to their website: www.aluminum.org .
Semi-hollow and hollow extrusions
Nominal Tol erances material B and H dimensions ± inches for B, H and T (inches) from - to
Material thickness
0-.06 .06-.12 .12-.24 .24-.4 .4-.6 .6-1.2 1.2-1.6 1.6-2.0 2.0-2.4 2.4-3.2 3.2-4.0 4.0-4.8 4.8-6.0 6.0-7.2 7.2-8.4 8.4-9.6 9.6-10.8 10.8+
Gap dimension
.006 .006 .008 .008 .010 .012 .014 .016 .020 .024 .028 .032 .036 .044 .050 .056 .060
Nominal dimension for G, inches from - to
0-.24 .24-.6 .6-1.2 1.2-1.6 1.6-2.0 2.0-2.4 2.4-3.2 3.2-4.0 4.0-4.8 4.8-6.0 6.0-7.2 7.2-8.4 8.4-9.6 9.6-10.8 10.8+
Tolerances for dimension g: Use the dimension G and distance A
Tolerances of material thickness T (dependent on the extrusion width B and H) ±
0-1.2 .006 .006 .008 .010 .012 .014 .016
>1.2-2.4 .006 .008 .010 .012 .014 .016 .018
inches
>2.4-4.0 .008 .010 .012 .014 .016 .018 .020
>4.0-6.0
>6.0-8.0
>8.0
.012 .014 .016 .018 .020 .022
.014 .016 .018 .020 .022 .024
.016 .018 .020 .022 .024 .026
Definitions: CCD = Circumscribing circle diameter T min. = Minimum material thickness
Factor =
CCD T min.
Tolerances for gap dimension G dependent on the distance A ±
inches
>.2-.6
>.6-1.2
>1.2-2.4
>2.4-4.0
>4.0
.012 .014 .016 .018 .020 .022 .024 .028 .032 .036 .040 .044 .048 .056 .064
.020 .022 .024 .026 .028 .032 .036 .040 .044 .048 .056 .060 .068 .072
.038 .040 .042 .044 .048 .052 .056 .060 .064 .072 .076 .084 .088
.068 .070 .074 .078 .080 .084 .088 .092 .100 .108 .112 .116
.104 .108 .112 .116 .120 .124 .132 .140 .144 .148
* The Aluminum Association periodically updates standards. Contact the Association for the latest standards ( www.aluminum.org ).
31
Round tubes
Diameter D: Wall thickness T: Ovality: Eccentricity:
Box
±1% of D, min ±.012" ±10% of T, min ±.008" Included in diameter tolerance Included in tolerance for wall thickness
H and B: Wall thickness T:
Same tolerances as for solid extrusions ±10% of T, min ±.010"
Solid extrusion profiles Straightness
h Profiles except “0” and Tx510*
≤
.094 inch thick
> .095 inch thick
Max H deviation in inches for length L in feet
6
10
13
16
20
L
.050 inch per ft
.300
.500
.650
.800
1.00
H
.0125 inch per ft
.075
.125
.163
.200
.250
H
Twist Circumscribed circle
Circumscribed circle
Tolerance V°
0 – 1.499
1° per ft, max 7°
1.500 – 2.999
1 / 2° per ft, max 5°
> 3.000
1 / 4° per ft, max 3°
All except “0” and Tx510*
Length < 120": h max = 0.0175 x B x L in feet
Flatness
Length > 120": h max = 0.0524 x B
Max F deviation in inches for width B (max) in inches Width B
4.0
5.2
6.4
7.6
8.4
9.6
10.8
12.0
Tolerance/inch width
.004
.004
.006
.006
.010
.010
.014
.014
F max. (tolerance) (inch x B)
.016
.021
.038
.046
.084
.096
.151
.168
Angle
Tolerance for V Leg thickness (inch) All except “0” and Tx510*
H/a ≤ 1
0 – .187
±
1°
±
2°
.188 – .749
±
1°
±
1 / 1 2°
+ 1°
±
1°
> .750
Corner radii Inside Radii
Outside Radii
Tol. =
Tol. =
±
10% of R
±
10% of R
Sharp corner:
Sharp corner:
.015" min.
.015" min.
* Tolerances for T3510, T4510, T6510, T73510, T76510, T8510 tempers
32
H/a > 1
Length tolerances Cutting at the press
Secondary precision cutting
Circumscribing circle from - to
120 - 200
200 - 320
0" - 2"
+ .120
+ .140
2" - 4"
+ .140
4" - 10" 10"
Length tolerance for length L (inches)
Circumscribing circle from - to
Length tolerance for length L (inches) 0-8
8 - 20
20 - 40
40 - 120
0" - 2"
+ .010
+ .020
+ .030
+ .040
+ .160
2" - 4"
+ .020
+ .030
+ .040
+ .050
+ .160
+ .200
4" - 6"
+ .030
+ .040
+ .050
+ .060
+ .200
+ .240
6" - 8"
+ .040
+ .050
+ .060
+ .070
> 8"
+ .050
+ .060
+ .070
+ .080
Cutting angle: 90° ± 1°
Sawing angle: 90° ± 0.5°
Fabrication tolerances
Precision tolerance standards
Fabrication tolerances are typically in accordance with specifications agreed upon with customers.
Leading extruders regularly produce extrusions and fabricate components to tolerances tighter than Aluminum Association standards. The Aluminum Association recently developed a set of “precision” tolerance standards which more accurately reflect good practice. Please contact the Aluminum Association for the latest tolerance standards and discuss specific tolerance requirements with your extrusion supplier.
Useful links Aluminum Association www.aluminum.org
Aluminum Extruders Council (AEC) www.aec.org
American Architectural Manufacturer's Association (AAMA) www .aamanet.org
In Hydro’s extrusion and fabrication processes, we utilize Coordinate Measurement Machines (CMM) to ensure manufacture to the appropriate quality and tolerance specifications.
33
Fabrication
Generally, extrusions made of aluminum can be
fabricating aluminum. These allow for faster, more cost-
fabricated using all methods available for other metals.
effective production.
During the last few years, however, a series of special
Throughout our plant network, we use cutting-edge
machines (including CNC multi-operation and long-
technology and processes to provide quality fabrication
length machines) have been developed specifically for
with high precision and tight tolerances.
35
Joining
The extrusion process allows for creative product design
extrusion to another or for joining an extrusion to
including joint design. Strong, stable, quick-to-
another material.
assemble and effective joints are used for joining one
There are many advantages to be obtained by joining several smaller extrusions to create a larger unit. Handling is easier. Extruding, surface treatment, and a large amount of the machining can be more easily managed. Smaller extrusions can be produced using less material, with greater accuracy and, in many cases, lower die costs. The following examples show a wide range of joining methods. We hope that this will inspire the extrusion designer to create better product solutions using joining.
Screw grooves With edge joints, assembly of covers, and other applications in mind, aluminum extrusions can be designed with screw grooves for selftapping screws or plastic screws. The material consumption of the screw grooves is insignificant, but fabrication costs are significantly lower compared to conventional methods of drilling and threading screw holes. If needed, screw grooves for machine screws can be threaded in the normal way.
36
Longitudinal screw slots Thread diameter “D” mm (in)
For additional information, the article “Pull-Out Strength of Self Tapping Fasteners in Aluminum Screw Slots” (Light Metal Age, October 2008) is available as a free download in the Online Exclusives section of the Light Metal Age website: www.lightmetalage.com
Core diameter “d” mm (in)
Screw pitch “S” mm (in)
Length “L” mm (in)
2.2 (0.09) 1.6 (0.06) 0.79 (0.031) 5 (0.20) 2.9 (0.11) 2.0 (0.08) 1.06 (0.042) 6 (0.24) 3.5 (0.14) 2.6 (0.10) 1.27 (0.050) 7 (0.28) 3.9 (0.15) 2.9 (0.11) 1.34 (0.053) 9 (0.35) 4.3 (0.169) 3.1 (0.12) 1.69 (0.067) 9 (0.35) 4.2 (0.165)* 3.1 (0.12)* 1.41 (0.056)* 9 (0.35)* 4.9 (0.193) 3.4 (0.134) 2.12 (0.083) 13 (0.51) 4.8 (0.189)* 3.6 (0.142)* 1.59 (0.063)* 13 (0.51)* 5.6 (0.220) 4.1 (0.161) 2.31 (0.091) 16 (0.63) 5.5 (0.217)* 4.2 (0.165)* 1.81 (0.071)* 16 (0.63)* 6.5 (0.256) 4.7 (0.185) 2.54 (0.100) 16 (0.63) 6.3 (0.248)* 4.9 (0.193)* 1.81 (0.071)* 16 (0.63)* 8.0 (0.31) 6.2 (0.24) 2.12 (0.083) 9.6 (0.38) 7.8 (0.31) 2.12 (0.083)
D d
S L
*screws with a narrow head
Hole diameter for self-tapping screws Nominal Hole Thread screw diameter diameter size mm (in) mm (in)
2 4 6 7 8 10 12 14 5/16" 3/8"
1.8 (0.07) 2.5 (0.10) 3.0 (0.12) 3.5 (0.14) 3.8 (0.15) 4.3 (0.17) 4.8 (0.19) 5.5 (0.22) 7.0 (0.28) 8.5 (0.33)
2.2 (0.09) 2.9 (0.11) 3.5 (0.14) 3.9 (0.15) 4.2 (0.17) 4.8 (0.19) 5.5 (0.22) 6.3 (0.25) 8.0 (0.31) 9.6 (0.38)
Tolerance (±) mm (in)
0.15 (0.006) 0.15 (0.006) 0.15 (0.006) 0.15 (0.006) 0.15 (0.006) 0.15 (0.006) 0.15 (0.006) 0.15 (0.006) 0.15 (0.006) 0.15 (0.006)
60º
Channel dimensions for bolt heads/nuts Size
Length
Height
“L” mm (in)
“H” mm (in)
Gap dimension “G” mm (in)
M4
7.4 (0.29) 4.0 (0.16)
4.5 (0.18)
M5
8.4 (0.33) 4.5 (0.18)
5.5 (0.22)
M6
10.5 (0.41) 5.0 (0.20)
6.5 (0.26)
M7
11.5 (0.45) 6.0 (0.24)
7.5 (0.30)
M8
13.5 (0.53) 7.0 (0.28)
8.5 (0.33)
M10
17.5 (0.69) 8.5 (0.33) 11.0 (0.43)
M12
19.5 (0.77) 9.5 (0.37) 13.0 (0.51)
M14
22.6 (0.89) 10.5 (0.41) 15.0 (0.59)
M16
24.6 (0.97) 11.5 (0.45) 17.0 (0.67)
1/4"
11.8 (0.46) 5.0 (0.20)
7.0 (0.28)
5/16"
13.2 (0.52) 6.0 (0.24)
8.5 (0.33)
3/8"
15.0 (0.59) 7.0 (0.28) 10.2 (0.40)
7/16"
16.5 (0.65) 8.0 (0.31) 12.0 (0.47)
1/2"
19.7 (0.78) 9.5 (0.37) 13.5 (0.53)
9/16"
21.3 (0.84) 10.5 (0.41) 15.2 (0.60)
5/8"
24.5 (0.96) 11.5 (0.45) 17.0 (0.67)
37
L G
H
Bolting If design specifications call for the ability to easily assemble and disassemble components, a bolt with a washer and nut may be the best joining option. Normally, galvanized or stainless steel bolts are used. Painting contact surfaces with zinc chromate and a sealing compound can be a good way of stopping corrosion. To assemble a corner joint correctly, drill and ream the hole and then use a bolt with a close fit. The difference in diameter between the bolt and the hole can be up to .040". In simpler joints, reaming the edges is not necessary but the bearing stress in the hole and the shear stress of the bolt should be lower than the recommended maximum. For bolted joints with heavy loads, the hole should be reamed and the difference in diameter between the hole and the bolt should be .006", at most. If hot-dip galvanized bolts are used, the difference in diameter should be about .012" based on the diameter of the bolt before galvanizing. The length of the bolt should be long enough so that the cylindrical unthreaded section passes completely through the reamed hole. Steel bolts should be insulated from aluminum components in strongly corrosive environments. The most common insulation materials are nylon and e-coded washers. For additional information on fastener pull-over failure, the article “Hex Washer-Head Fastener Pull-Over in Moderately Thin Aluminum” (Light Metal Age, April 2009) is available as a free download in the Online Exclusives section of the Light Metal Age website: www .lightmetalage.com
The table below gives the measures that should be taken when stainless steel and hot-dip galvanized bolts are used in aluminum structures in various environments Stainless steel Environment
Insulation necessary
Immersed in seawater
No
Immersed in soft freshwater
No
Immersed in hard freshwater
Hot-dip galvanized steel
Alternative methods
Insulation necessary
1)
Paint contact faces Sealing compound Cathodic protection
No
1) 2)
Cathodic protection
1)
Spacer
No
1) 2)
Spacer
No
Paint contact faces Sealing compound Spacer
No
2)
Spacer (insulation)
Inland climate
No
None
No
Moderate marine environments
No 1)
Paint contact faces Sealing compound Spacer
No
1) 2)
Aggressive marine environments
Yes
Paint contact faces Sealing compound Spacer
Yes
2)
1) Without insulation, use one of the alternative corrosion inhibiting methods 2) Zinc coating has a limited life even if insulation is used
38
Alternative methods
None Spacer (insulation)
Spacer
Snap joints The elasticity of aluminum makes it ideal for snapped joints. Snap joints are highly effective at joining two or more extrusions, allowing for easy separation to give access to internal components. Designed properly, this joining technique is ideal for many applications. For example, many extrusions can be snapped together to create a whole panel. Large extrusions that cannot be produced as a single unit can be made as two parts and then snapped together. When designing snap connections, be sure to consider the risk of permanent shape change when the material loses its elasticity. This applies especially to connections that are frequently joined, separated and rejoined. In such cases, plastic clips, steel springs or similar connections should be used.
Creating enclosures When joining one extrusion to another, they can either be slid together longitudinally in specially designed tracks or snapped together. Locking options include specially designed deformations, screws, or cylindrical plugs. Cabinets and other enclosures are often built by sawing an extrusion and then joining the two halves together. They are locked together by fitting a cover. This technique makes for easier assembly of electronic components. It also reduces die costs since solid aluminum extrusions can be used, which are easier to produce than hollow extrusions.
39
Hinges Aluminum extrusions provide many opportunities for designing integrated joints and hinges. Correct design can give a movement of 90° without any need for machining. Screw grooves can also be designed into the extrusion for later assembly and connection of other parts. One very practical solution is a geared hinge assembly where two curved gearlike extrusions interweave within a protective third extruded housing to form a unique hinge.
The geared hinge assembly
This extruded truck door hinge is lightweight and can be made to practically any length. The design also eliminates the need for expensive stamping die tooling.
Formed joint A formed joint can be a good solution if a permanent joint between two extrusions or an extrusion and another material is required. Long sections that are too wide to be extruded can be produced by rolling two extrusions together to the required dimension. Aluminum is excellent for this application as it can be easily manipulated without detriment to form or function.
40
Butt joint Butt joints can be made by using guide pins or screws along the length of the extrusions.
Connected extrusions Dividing a large extrusion into several smaller ones can often be economically advantageous. Aluminum extrusions can also be designed so that, together, they create a larger structure with sufficient strength to cope with even heavier loads.
Corner joints
Simple joining of two extrusions that are screwed, riveted or bonded
Extruded corner cleat
Corner joint using a steel cleat
Sleeve joint A sleeve joint gives a more durable and permanent joint.
41
Extruded 3-D corner cleat
Riveting Joints using blind nuts or nutserts are often used when it is impractical to thread thin-wall extrusions or for joints that will be frequently assembled and disassembled.
Swaging and telescoping Swaging is a forming technique where the diameter of the end of a tube is reduced (or increased) using dies. This allows the swaged tube end to fit into a non-swaged end of the same diameter tube. Product examples include aluminum bats, tent poles, furniture legs, flag poles, and bicycle tubular parts. Telescoping employs sequentially smaller diameter tubes, which slide out from one another, to lengthen an object. Product examples include golf ball retrievers, painting poles, and camera tripods.
Swaging
Joining to other materials When joining to other materials, extrusions should be designed to accommodate the other material's properties in elasticity, strength, corrosiveness, etc. By devising innovative extrusion solutions, strong, functional joints can be achieved with most materials.
42
Telescoping
Adhesive bonding
risk. In order to apply a load, the distance between the molecules in the material to be bonded and those in the adhesive should be no more than 0.5 nm (a half a millionth of a mm). To achieve this closeness, the adhesive must have a lower surface tension than the material to be bonded otherwise the adhesive will form a drop rather than flow evenly over the surface. Additionally, the presence of impurities and oxides will prevent the proper interaction between the adhesive and the aluminum. The surfaces to be joined should be clean and reproducible in order to achieve an even bonding result.
Adhesive bonding is an important complement to conventional joining techniques. Adhesive bonding is used more with aluminum than with any other metal. Examples include adhesive bonded joints in aircraft, which have been used since the 1940s, and brake linings for cars bonded to aluminum brake shoes. There are a number of different adhesives for surface pre-treatments and bonding which can be used. It is not always easy to select the right combination, nor is bonding without the required know-how free from
Adhesive types To make the right choice of adhesive, detailed information should be available on: • Which materials are to be bonded as well as any surface treatment • The environment to which the bonded joint is to be exposed (indoors, outdoors, industrial, marine)
• Loads, load frequency and load type • The size and shape of the bonded area, preferably defined with a drawing • Production conditions (batch size, productivity requirements, possibility of heat curing)
• Normal, maximum and minimum temperatures
• Any other requirements for the joint (aesthetic, easy disassembly)
Type of adhesives
Properties
Strength
Temperature range
Anaerobic adhesives
Cure in contact with metal in the absence of oxygen. Longer curing times on aluminum than on steel. Maximum slit opening .024". Used as sealing compound and locking compound for screws.
17-30 MPa 2.5-4.4 ksi
-60 to 350°F
Cyanoacrylates
Super adhesives, rapid curing in damp conditions require at least 40% relative humidity to cure. Maximum slit opening .010".
12-16 MPa 1.7-2.3 ksi
-60 to 175°F
Little known Variable
Modified acrylates (High performance)
1- or 2-component adhesives that also cure rapidly at room temperature. Good impact resistance and peel strength.
25-35 MPa 3.6-5.1 ksi
-95 to 250°F
Good after sufficient surface pre-treatment
Epoxy resins
The most common adhesives used in structural bonding. 1- or 2-component adhesives. Normally require heat curing for high strength. Additives make the adhesives stronger, more flexible and give a better peeling strength but poorer high temperature properties.
25-45 MPa 3.6-6.5 ksi
-67 to 392°F
Good after sufficient surface pre-treatment
Polyurethanes
1- or 2-component adhesives, rapid curing with good flexibility. Strength lies in the thickness of the bonded joints. The adhesives are very water resistant but do not bond all surfaces equally well, something that can give poor longterm bonding properties for the joints. This problem can be solved by using a primer. The adhesives are used in the vehicle industry for bonding metal to fiberglass.
17-25 MPa 2.5-3.6 ksi
-256 to 195°F
Good after sufficient surface pre-treatment (primer)
Phenolics
The first type of adhesives to be used for metals. Require pressure (0.3-0.7 MPa) and heat (<300°F) to cure.
30 MPa 4.4 ksi
-60 to 350°F
Polyimides
Expensive, high-temperature adhesives that are relatively complicated to use. Withstands over 510°F temperatures for hundreds of hours.
20 MPa 2.9 ksi
Hot-melt adhesives
Offer possibilities for high productivity and are therefore used in industrial mass production of structures with small loads.
Rubber adhesives
Cure through evaporation of a solvent. Many types and qualities. Mainly used for bonding other materials (wood, rubber, plastics, glass) to aluminum. Not normally used str ucturally.
Silicone adhesives
Adhesives with relatively low strength but good high temperature properties and flexibility.
Pressure-sensitive adhesives
Often used in tape form. Does not cure and therefore has relatively low strength. Used for things like fastening décor strips to aluminum on cars, anodized or painted outer plating of aluminum on trucks, RV's, and cars.
43
3-6 MPa 0.4-0.9 ksi
+140 to 480°F
Chemical resistance
Good aft er correct surface pre-treatment and with high quality adhesives
Advantages and limitations An adhesive bonded joint has many good properties. To make the most of these properties, it is important to think about adhesive bonding at the design stage.
Advantages with bonding • • • • • • • • • •
Limitations with bonding
Various materials can be joined Galvanic corrosion can be avoided Joint is permanent Makes structures stronger and more rigid Distributes load and stress more evenly in the joints Stress concentrations can be avoided. The adhesive seals and bonds and prevents crevice corrosion Low costs for finishing Good fatigue characteristics Dampens vibration Reduces weight and number of required components
• • • •
Should not be handled directly after bonding High temperature results in reduced strength A bonded component is difficult to disassemble for repair and service Pre-treatment of the surface before bonding is essential for structural bonding and to obtain satisfactory quality in corrosive environments • It is necessary to ensure that the adhesive completely covers the surface • Potential health, environmental, and safety issues
Construction of joints It is important to know the types of loads the joint will be exposed to. When bonding a joint, it is essential to: • Maximize tension, shearing, and compression • Minimize peeling and cleavage • Maximize the area over which the load is spread
Shearing
Peeling
Tension/Compression
Cleavage
44
Basic adhesive bonded joints The majority of joints can be grouped into four basic types. (For examples below, the arrows show in which directions the bond best absorbs loads):
1. Angle or corner joint
2. T-joint
3. Butt joint
4. Lap joint
Surface treatment prior to adhesive bonding While pre-treatments can significantly improve bonding strength, they can be expensive and may be hard on the environment. Design considerations should analyze the cost/benefit of the desired bond quality and its impact on both monetary cost and possible harm to the environment.
A bonded joint is like a chain with links where the weakest link determines the strength and overall service life of the joint. Pre-treatment can improve the strength of these links and, therefore, improve the overall strength and life of a bonded joint. One or more of the following processes can be used for pre-treatment before bonding: • Cleaning and degreasing (acidic, alkaline or solvent based) • Grinding or blasting with subsequent cleaning • Chemical etching, conversion coating, anodizing • Primer
45
Welding Welding is a powerful joining technique, if done properly, and the majority of aluminum alloys can be welded using conventional methods.
MIG welding
Special welding methods have also been developed specifically for aluminum. Welding has the following advantages for joining: • Welding is the safest and easiest method of making airtight and watertight joints • It is possible to weld materials of thicknesses from .040" up to 2". Using special equipment, it is possible to weld foils. • Welding is faster and more economical compared to other joining methods • Welding can save material when joining
MIG welding evolved from TIG welding in an effort to speed up the welding process. MIG uses a welding electrode whereas TIG uses tungsten. A filler is introduced automatically as a wire in the electric arc. This method can be used for all types of joints and welding positions and gives good results. MIG is used for material thicknesses of .120" and up, but with special equipment, materials as thin as .028" can be welded. Welding speed is around 15 to 30 inches/minute for .160" to .800" thick materials. To optimize the welding parameters, “super clean” argon (Ar 99.9) should be used as a protective atmosphere. The main advantages of MIG welding are its high welding speed and good penetration. The area affected by heat is less than with any other welding method because of the speed of the process. MIG welding equipment requires thorough maintenance and cleaning and costs more than other welding equipment.
Common aluminum welding methods The most common fusion welding methods are Tungsten Inert Gas (TIG) welding and Metal Inert Gas (MIG) welding. In general, both these methods give good results. Gas welding is used on a limited scale and metal arc welding is used even less.
Fillers The thickness of the parts to be welded determines the amount of filler. Fillers are standardized and are available in wire or rod form with diameters from .080" to .240". For materials .040" to .080" thick, .080" wire is used. For material thickness of .320" to .400", .200" to .240" wire is used. Choosing the proper filler metal is very important. The molten alloy in the weld puddle is a mixture of the filler metal and base alloy. In this dilution, the welding alloy should provide strength, ductility, resistance to cracking, and corrosion resistance. If welded assemblies are to be anodized, filler alloys containing silicon (e.g. 4043) will discolor to a gray hue in the
TIG welding The TIG method does not require flux, which makes it highly suitable for aluminum. TIG is ideal for materials from .028" to .040" thick and where shorter joints are required. TIG welding can be used on all alloys that can be welded and, if correctly applied, gives the most fault-free welding of the conventional methods.
46
Other welding methods
anodizing process. To minimize discoloration, an appropriate aluminummagnesium alloy filler should be used. Also, it is important that the filler be clean and dry. If the surface is contaminated, it can be cleaned by passivation or brushing.
Other welding methods include spot and seam welding, flash welding, and cold and hot pressure welding. Methods such as explosion, high frequency laser, ultrasound and electron beam welding are used under special circumstances.
Robotic welding
Extrusion design for simplified welding
Robotic welding is the use of mechanized programmable tools to automate the welding process by performing the weld and handling the part. While robotic welding is commonly used for high production applications such as spot welding in the automotive industry, its use is expanding quickly for a number of applications in other industries. Robotic welding can help increase productivity and reduce the overall manufacturing costs for medium- to high-volume production. Typically, a robotic welding process can replace the manual processes of 6 to 8 people, hence driving labor costs down. What’s more, with an optimized part design, robotic welding can also improve manufacturing flexibility and throughput, allowing different parts of different designs, but similar welding requirements, to be processed through the same robotic welding line.
Welding can be simplified and a joint's strength increased through proper design. And with the proper design, an extrusion can be optimized by taking into account joint preparation and material compensation, the use of backing bars, and minimizing the number of welds.
Aluminum alloy
Suggested filler metal for specific requirement Color matching Lowest crack potential after anodizing
Strength
Ductility
3003
4043
1100
1100
4043
6061
5356
5356
5654
4043
6063
5356
5356
5356
4043
7005
5356
5356
5356
5356
7039
5356
5356
5356
5356
Information provided by J.W. Harris Co.
Fusion welding Flux
Minimum thickness of the material
Preheating 1 Minimum thickness of material, etc.
Temp. °F
Spread 2 of heat affected area (inches)
Welding speed 2
Cost 2 Investment
Manual
Automatic
Investment
0.5
5
10 - 20
1.2
1
5-10
20 - 30
1
Variable costs
TIG welding
No
.028"
.400"
302 - 392 .047 - .051
MIG welding
No
Spray arc: .120" Short arc: .063" Pulse arc: .028"
.600"
302 - 392
Gas welding
Yes
.040"
.120"
572 - 752 .140 - .160
0.2
–
1
1.6
Arc welding
Yes
.140"
.140"
302 - 482 .060 - .063
0.4
–
10
1.4
1. Caution: cold worked and age-hardened material softens at temperatures above 300°F
47
.040
2. Relative values
Friction Stir Welding is a method suitable for joining aluminum extrusions between .080" and .320" (2 and 8 mm) thick, up to 49 ft. (15 m) long and with a welding speed of approx. 3 ft. (1m) per minute
Friction Stir Welding (FSW)
The method, patented by the Welding Institute in Cambridge, Britain in 1992, has been developed by several international industrial partners. Hydro has taken an active part through its research center in Karmoy, Norway. This method is believed to have great potential for many applications.
FSW is a relatively new method for joining. Two aluminum extrusions are held together while a rotating tool presses down and runs along the joint. The rotating tool generates a temperature in the metal of between 200°F and 300°F below aluminum's melting point and mixes the materials from both extrusions together in a plastic state without melting, yet forming a weld. The method requires neither filler nor a protective atmosphere and generates a weld virtually free from heat deformations. The method is suitable for joining aluminum extrusions between .080" and .320" thick. Welding speed is about 3 ft./min.
FSW does not require filler or a protective atmosphere and creates a weld that is virtually free from heat deformations
A rotating tool is pressed down in the metal and run along the joint
48
Machining and forming Sawing Higher sawing speeds can be achieved with aluminum than with steel. And the greater the sawing speed, the more economical the solution. The good sawing properties of aluminum do not just depend on the alloy and its condition but also the relationship between the tool and its design, the lubricant, and the metal. Generally, the most efficient and economical sawing is achieved using tools with a large cutting angle where chips are effectively removed. Aluminum extrusions can be cut accurately without the formation of burrs. The appearance of the cut, the alloy used, and the extrusion's strength determine the size of the teeth, number of revolutions per minute, number of teeth, diameter of the blade, and the feed rate. The number of teeth should be sufficiently large to give a clean cut. When sawing thin extrusions, a fine-tooth blade and cutting lubricant should always be used.
Deburring Deburring is a process for removing small chips and any remaining burrs on the extrusion cut. The most common method is mechanical, using a brush or a grinding machine. Abrasive tumbling, where fragments are removed by friction using circulating stones, is suitable for deburring small to medium sized parts.
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Milling Milling machines for fabrication of aluminum have larger teeth pitches than equivalent tools for steel and more spacious grooves for chip removal. As with sawing, a high cutting speed is required for good results. A high quality surface demands high power and stability in the tool and feed mechanism. There is a difference between end and peripheral milling machines. Which one is used depends on where the surface to be milled is situated in relation to the milling spindle's center line. For end milling, product diameter should be at least 20% larger than the width of the surface being treated. The axis of rotation of the end mill may be either perpendicular or parallel to the finished surface, often with 2/3 of the surface moving against the cutting direction and 1/3 moving with the cutting direction during milling. For peripheral milling, the milling teeth move in the line of feed (down-feed milling); the peripheral cutting edges generate a finished surface parallel to the axis of rotation. Examples include a slab milling cutter, a shank-end mill, a side-milling cutter, or a spindle moulding cutter.
Drilling As with most machining, drilling should be carried out at a high speed. When using standard bits, they should be sharpened to reduce the pressure required and obtain better results. Special bits for aluminum are only required for deep holes or soft alloys. It is important to note that the hole will be considerably larger than the bit diameter when drilling in aluminum, especially with soft alloys. A considerable amount of heat is generated when drilling deep holes, especially if the diameter is large. Cooling is therefore essential to avoid hole contraction.
Turning Aluminum can be turned in standard, custom, and automatic lathes and should be carried out at high rotation speeds. Parts to be turned should therefore be fitted securely to avoid vibration. Spacers between the part and the mounting prevent marks on the metal and deformation.
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Tapping Internal and external threads can be made using all available machining methods as well as through plastic deformation. Heat treatable alloys (e.g. 6000 and 7000 series) give especially high quality results. Taps for steel can be used for threads under .240", but custom taps should be used for larger diameters. Internal threads can either be made with taps in series or with a single tap. The groove for chips should be large and wide, well rounded and polished, and have a large cutting edge angle. The back surface should run radially or be undercut so that the chips do not fasten between the tool and the thread when the tap is drawn out. Special threading taps are normally divided into three types: • The first is hole polished with the pitch against the cutting line so that the chips are pushed forward in front of the tap during threading • Another type is designed so that the thread is interrupted from groove to groove • Finally there is one that has a spiral chips groove for lighter cutting with better pressure during threading. External threads are made using ordinary threading tools or screw cutting dies. The threads can also be formed plastically by rolling without any chips being formed. This creates a very strong thread. The external diameter of the part to be threaded should be 0.2 to 0.3 times the size of the screw pitch compared to the nominal thread diameter. It is very important that the center lines of the metal part and the tool are aligned. Very good results are also obtained with threading down to M5.
High-performance machining stock Incorporating high-performance machining stock into your manufacturing process will reduce machining forces, cutting times, and tool wear. Due to dimensional stability and tolerance control, setup time can be minimized. Enhanced straightness provides smooth feed-thru and is well suited for automated rod and bar feeders. High-performance machining stock generates compact chips allowing machinery to operate smoothly with minimal downtime, thereby improving efficiency and lowering costs.
Conventional bar cross section (inconsistent, coarse grain)
OptiGrain MG is Hydro’s precision extruded aluminum product designed for high-speed machining operations. Hydro’s proprietary die design and advanced press control systems produce a product with improved straightness, tight tolerances, reduced twist, and elevated mechanical properties. OptiGrain MG offers improved and repeatable pieceto-piece and lot-to-lot performance over standard extruded aluminum products. And, OptiGrain MG provides good finishing characteristics, excellent corrosion resistance,
OptiGrain MG cross section (consistent, fine grain)
and responds well to anodizing. It is the right product for the most demanding jobs. OptiGrain MG bar stock achieves 1/3 commercial extruded tolerances for straightness and 1/2 commercial tolerances for twist and bow. OptiGrain MG exceeds Aluminum Association Standard Tolerances and Precision Tolerance for extruded rod. Typical applications for high-performance machining stock include: • Automotive parts • Hardware • Couplings and connectors • Fasteners • Fittings • Hinge pins • Military components
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punching holes. The angled ground part should, at the most, be equivalent to the thickness of the part of the material that is to be cut out. Regardless of the shape of the die, the punch should be left flat if the part that is cut out is to be used (i.e. rather than discarded). It is important to maintain the correct clearance between between the punch and the die during the actual cutting process. The clearance is determined by the material's composition composition and the thickness of the cut material.
Shearing/pressing Press work is normally carried out in eccentric presses with a cutting (shearing) tool. Press tools for aluminum are slightly different f rom those designed for other metals. Punches and dies made of hardened tool steel are recommended. Burrs are avoided by regularly sharpening the punch and die. The cutting force required can be reduced considerably if the punch's surface is ground at an angle(shear). This is especially especially effective when
Press tools with stripper plate
Stripper plate
Punch Die
Punch
Sprung stripper plate
Die
bridged” by dividing it into two sections held together by the polyurethane. In this way the thermal bridge is interrupted. With the other technique, called strip strip joining, two extrusions are joined using polypropylene polypropylene or polyamide strips which are mechanically mechanically rolled into position. This way of insulating makes it possible to use different colors on the inside and outside of a window. window. Hydro offers both fill and debridge and strip joining in North America.
Thermal break If untreated, aluminum's high coefficient of thermal conductivity can be problematic problematic in applications where low heat transfer is desirable such as in windows. Insulation Insulation can easily rectify this issue. Two Two commonly used techniques greatly reduce heat conduction. With the first technique, called fill and debridge, debridge, the extrusion is extruded in one piece and a cavity in the extrusion is filled with polyurethane. When the polyurethane cures, the extrusion is “de-
Limitations: feed cross section 12.5" x 11.75" (322 x 300 mm) Minimum length: 11'2" (3.4 m) Maximum length: 26'3" (8.0 m)
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Bending Bending an aluminum extrusion is the process of manipulating the material beyond its yield strength until it retains its new form. An extrusion is reformed, or bent, by holding it at both ends and shaping it using a variety of tools. Bending is a tightly controlled process that allows for high shape accuracy. accuracy. Aluminum extrusions can be bent using using the same equipment as for other metals. Bending can take place with a hardened metal for larger radii but smaller ones usually require soft-annealed or T4 (half-hardened) metal. It is possible to harden to full strength after bending. Large batches should not be produced in the T4 condition as there is a risk that the material will be left standing and will age-harden. The material in the bend can be harder than the rest in the event of high stresses, for example with very small radii. This is important if the original material is in the T4 condition and is to be hardened to T6. In such cases the bend can be annealed. Bending should be carried out before anodizing if a complete anodized layer without cracks is required.
Solid extrusion being bent using CNC stretch forming. To be used as part of a heavy truck’s side assembly and door frame.
Design considerations The need for bending should be taken into consideration at the design stage. Bending can significantly simplify a design and reduce the number of components needed for an assembly. assembly. This, in turn, can make the design more economical, reducing costs by reducing materials and labor needed to produce the product. Other points to consider when evaluating bend designs include: • Whether Whether the extrusi extrusion on will be hollo hollow w or solid solid • How wide wide or narro narrow w a radius is required required • What type of alloy, alloy, heat treatment, treatment, and aging aging will be used • What the final final geometry geometry of of the product product will will be
Bending methods Stretch bending Aluminum has limited strain distribution distribution characteristics; it does not not like to stretch. A part should be designed so that it forces even stretch distribution across the metal. Stretch forming is the process of increasing the surface area of a part by stretching the metal over a forming punch. Stretch Stretch dies force the metal to thin out and strain during tension. Internal and external supports may be employed to provide support to retain the proper geometry. The extrusion is held tightly and rotates with the stretch-forming tool. This method is suitable for small radii and can be repeatedly carried out.
Roller bending Used to bend extrusions with large radii. The extrusion is rolled between three wheels of which one is adjustable. It is possible to vary the radius on the same component using CNC-controlled machines.
Press bending Suitable for simpler operations in large batches. The parts are shaped in a two-part tool in, for example, a hydraulic press or other simple equipment.
Hollow tube bent to form a car’s fuel filler pipe
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CNC machining
Robotic handling
Computer Numerical Control Control (CNC) machining is a process where all aspects — from tool cutter path, to material feed, tool rotation speed, and the linear or circular movement of the tool path — are controlled controlled by machine. CNC machines can be programmed by either direct operator input or by CAM (Computer Assisted Manufacturing). Introduction of CNC machines has radically changed manufacturing. Curves are easy to cut, complex 3-D structures are easy to produce, and the number of machining steps that require human action has been dramatically reduced. There have also been considerable improvements in accuracy, consistency, consistency, and quality. CNC automation helps eliminate errors and provides CNC operators with time to perform additional tasks. Production volumes can increase thanks to higher "speed and feed" times. In a production environment, a series of CNC machines may be combined into one station, commonly called a "cell", to progressively machine a part requiring several operations. Diamond tooling and Poly Crystalline Diamond (PCD) can also be utilized with CNC machines, increasing production times and fabrication accuracy. And, tools used in CNC operations tend to wear better and last longer.
Robotic handling, or industrial automation, is the use of computercontrolled controlled industrial machinery to replace human operators in certain manufacturing operations. Robotic machines can be programmed to handle any fabrication requirement, from simple to complex. Welding, painting, drilling, sawing, and the like are just a few examples. Robots are particularly useful in replacing human labor for repetitive or dangerous tasks. Robotic handling can help increase productivity and reduce the overall manufacturing costs for high-volume production. Typically, a process that may take 6 or 8 people to handle manually, can be effectively designed for robotic automation with one operator.
A single operator can manage manage multiple fabrication steps with the aid of robotics
Further, Further, throughput and product quality can be improved while process errors and material waste are reduced. Robotic automation can also significantly improve manufacturing flexibility and scheduling. Using the same machines on the same production line, robotics allow for easier change in production of one part to another.
CNC manufacturing cell Today, CNC machines are typically controlled directly from files created by CAM software packages. This means that a part or assembly can go directly from design to manufacturing without the need for producing a drafted paper drawing of the manufactured component. component. This significantly speeds up production turnaround times and manufacturing efficiencies.
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Contract manufacturing
Contract manufacturing is the outsourcing, or
processes, certifications, and more. The best contract
contracting, to a third party the manufacture of a complete product or sub-assembly. Contract
manufacturers can help fine-tune their client's specifications and offer design engineering, customized
manufacturers work with their customers to determine what is needed in materials, labor, production
tooling, fabrication, finishing, full-scale production, final product assembly, warehousing, and delivery.
There are many potential benefits businesses can accrue by outsourcing their assembly and manufacturing: • Focus on core competencies: Shed non-core functions, boost internal R&D and marketing, and concentrate on internal strengths • Increase profitability: Reduce labor and overhead costs, trim supply inventories • Reduce time to market: Increase scheduling flexibility and resource availability to speed up product deployment • Leverage application expertise: Access external experts to enhance internal capabilities
When you outsource, you naturally loose some visibility as to what is happening on the f actory floor. You will want a partner whose operations are transparent and who communicates effectively and frequently.
Market knowledge A good contract manufacturer will not only analyze the product design, but will also have a good understanding of the market into which the product will be sold, how the product is meant to be used, the standards it must meet, as well as the aesthetic and functional requirements of the market.
Flexibility and OTD When you decide to outsource your products or sub-assemblies, you place your company's reputation in someone else's hands. Choosing the right partner is a critical decision. Here are some things to consider:
Your manufacturing partner should be able to respond rapidly to requested changes. Ask for examples of h ow the contract manufacturer ramped up their manufacturing facilities to launch a new program or respond to an engineering change to an existing product. Also, a contract manufacturer should be able to deliver product on time and be able to guarantee a certain level of On Time Delivery (OTD). Ask your contract manufacturer for their OTD performance.
Project management A major benefit of outsourcing is the transition of project management to a third party expert, freeing up time and internal resources. The best contract manufacturers should be able to manage everything from sourcing of components, such as aluminum billet and specialty hardware, to warehousing and Just-In-Time delivery.
Teamwork, visibility, and control The success of any outsourcing arrangement lies in the ability of all parties to effectively work together. A production team should be formed, a detailed action plan developed, and all aspects of the design and production process reviewed together to ensure that production is done in the most cost-effective way.
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Surface treatment
There are two main reasons for surface treating
organic. Some of the properties that can be changed
aluminum extrusions: for aesthetics or to give the surface special properties.
and improved by surface treatment are corrosion resistance, surface structure, hardness, wear,
The treatment methods are divided into four main
reflectivity, and electrical insulation capacity.
types: mechanical, chemical, electrochemical, and
Shaping the extrusion The extrusion process provides opportunities for improving the surface even at the design stage. For example, the structural variations of an extrusion that has uneven material distribution can be hidden by decorative grooves on its surface. Engineering drawings should indicate a product’s visible surfaces, shown here with dashed lines. By indicating its visible portions, an extrusion can be designed to address potential surface problems.
Methods of surface treatment Type
Technique
Characteristics
Mechanical
Grinding / Brushing Polishing Vibration polishing Highly polished
Fine lines in the direction of grinding. Gives a faint silky matte appearance Polish the surface and the grinding lines partly disappear Matte to shiny surface, suitable for small areas Gives a mirror finish
Chemical
Etching Bright dipping Chromating / phosphating Plating with copper, tin, nickel, silver *
Pre-treatment for various types of surface treatments, gives a clean, matte surface Gives a mirror finish Pre-treatment prior to powder coating or electrostatic painting
Electrochemical
Anodizing Electrolytic polishing
Gives a hard, clear or colored oxide layer. For decoration or increased surface protection. Gives a smooth surface with high reflectivity
Organic surface coating
Wet painting Powder coating Screen printing Coating with protective foils
Gives various degrees of protective and decorative surfaces Printing of text, décor patterns, etc. For decoration, protection or other properties
Gives good soldering, conductivity and reflectivity
* These plating processes are mainly carried out electrochemically
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Mechanical surface treatment
Grinding Grinding gives a decorative, non-reflective surface that can vary from a sandblasted to a velvety appearance. Ground surfaces should be anodized or painted to inhibit corrosion.
Special surface finishes can be achieved by mechanical treatment such as polishing and brushing. These methods remove all small faults on the surface, provide uniformity, and make further treatment possible for a reflective or decorative surface.
Polishing Polishing is a process that consists of grinding, oiling and polishing with chamois leather in several stages, as an automated or manual process. A smooth, brightly reflective and scratch-free surface with good luster can be achieved with negligible loss of material.
Bead blasting Bead blasting is ideal for creating a matte finish from a mill finish. Extrusions are placed on a linear conveyor and passed through a chamber. Sand-like grains made of aluminum oxide are passed through pneumatic or compressed air nozzles, blasting the aluminum components until the perfect finish is achieved.
Tumble deburring A very good method for smaller aluminum parts for removing burrs, smoothening sharp edges, and polishing, to some extent.
Knurling The word "knurling" applies to both the method of production and the rolled section on the part. It is usually produced by forcing a knurling die into the surface of a rotating part, displacing material from the original diameter. Some applications include decorative and "grip" surfaces, repair of undersized shafts and oversize bores, and driving serrations and splines.
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Chemical surface treatment Chromating/phosphating
Etching
Chromating or phosphating is carried out to improve the adhesion between the aluminum substrate and the powder coating. Corrosion resistance is improved as well. These two conversion coating methods are also used for the surface treatment of components that require good electrical conductivity.
Etching is a process that either takes place in acid or alkali solutions. It removes small, evenly distributed impurities on the surface such as oil, dirt and the ever-present oxide layer. A matte, greyish surface can be achieved depending on the alloy, the condition of the surface, the chemical composition, the temperature of the bath, and the immersion time. Etching is used as a pre-treatment before anodizing or painting.
Chemical brightening and polishing
Plating with copper, nickel, silver, and tin
Chemical polishing baths attack irregularities in the material to give an even surface. This treatment gives the surface a mirror finish but, at the same time, is very delicate and should be treated further by anodizing or painting.
Surface treatment methods that provide good soldering, reflective and conductivity properties for both electricity and heat. These methods are used on components for telecommunications as well as electrical and technical applications.
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Anodizing Anodizing is an electrochemical process that creates a significantly thicker layer of oxide than occurs naturally. This provides protection against mechanical wear and corrosion at the same time as electrically insulating the surface. The process involves placing the extrusion in an electrolyte bath with a DC current where the extrusion acts as the anode (hence the name). When the current is applied, a thick oxide layer is formed, which becomes an integral part of the material. The thickness of the layer is determined by a combination of the temperature and composition of the bath, applied current, and anodizing time. The oxide layer created consists of a number of open pores that enable dying or coloring. The anodic oxide layer can be colored in a wide range of shades. The process is completed by sealing with boiling water which closes the pores.
Properties The wear and corrosion resistance of the surface can be improved by increasing the thickness of the anodized layer. The table below gives recommended thicknesses for various applications. Anodized extrusions are suitable for a range of architectural and decorative applications that require a beautiful and durable surface. Anodized aluminum extrusions minimize the need for maintenance. They should, however, for aesthetic reasons, be cleaned regularly with water and a neutral or mild soap and put through a clean water rinse. Strong acids and alkalis should not be used.
The anodic oxide layer formed by anodizing provides very good resistance to corrosion. The surface is not normally affected by contact with solutions and substances with 4 to 8.5 pH. The surface can be stained and damaged by strongly alkaline substances. This is something to remember for aluminum building components, which should be protected during construction from concrete, cement, etc. Aluminum's natural oxide layer has a thickness of about 0.02 µm. By anodizing, the thickness of the oxide layer can be increased to 25 µm. The hardness of the anodized layer exceeds that of steel, nickel and chromium and is the same as corundum. At the same time, the melting point of the surface increases to around 3600°F. The oxide layer formed by anodizing has good insulation properties and a breakdown voltage of 500V - 600V at a thickness of 12 µm - 15µm.
Recommended layer thickness after anodizing Layer thickness μm
Application
25
Surfaces strongly affected by corrosion or wear, especially outdoors in corrosive environments
20
Strong or normal exposure outdoors (e.g. building materials, vehicles and boats)
20
Strong exposure indoors to chemicals, in damp air (e.g. the food industry)
15
Relatively hard wear indoors (e.g. handrails or decorative features outdoors)
10
Normal exposure indoors or outdoors in dry, clean air. For reflectors, fittings, decorative strips on vehicles, sports equipment
5
Normal indoor exposure
The Aluminum Anodizers Council (AAC) website provides layer thickness specifications for various applications and other useful information. www.anodizing.or g/Reference/reference_guide.html
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Color anodizing Before the final sealing of the pores, the anodic oxide coating can be colored. Two methods are used: Dying is carried out directly after anodizing in a separate step. Both organic or inorganic coloring agents are used. The process is completed by sealing. Many colors are available. However, organic dyes are not resistant to UV light and this method is most suitable for products that are to be used indoors. Electrolytic coloring is carried out in a separate step after anodizing using an AC current. The pigments, which consist of metallic salts, penetrate into the pores. This process is also followed by sealing. The result is very resistant to the effects of UV light and is highly suitable for products to be used outdoors. The colors range from golden bronze to black.
automated spray systems in contained rooms or machines propel liquid paint at the components to be coated. Liquid coatings must be applied to properly cleaned, pre-treated and primed materials and then oven baked.
Electrostatic painting Powder coating Powder coating is a dry finishing process, using finely ground particles of pigment and resin, electrostatically charged and sprayed onto a part to be coated. The coating process can be done manually or automatically. The parts to be coated are electrically grounded so that the charged particles projected at them adhere to the surface and are held there until melted and fused into a smooth coating in the curing oven. The result is a uniform, durable, high-quality finish.
Comparing the two While both powder coating and wet painting are effective in providing various color options, powder coating tends to be a more durable finish. And, because the powder coating contains no solvents, its impact on the environment is minimal, as compared to liquid paints. For a product with a number of visible hinges, grooves, and accessories, liquid painting is preferable. Wet paint is also preferred for products that may require repairs of blemishes, scratches, and dents.
Wet painting Wet painting, as its name suggests, is the process of applying liquid paint. Liquid paint is composed of pigment, resin, and solvent. Typically, large
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Screen printing A durable and decorative result can be achieved on aluminum extrusions using screen printing. This can be carried out on both untreated and anodized surfaces. Especially durable results can be achieved if the screen printing is carried out between the anodizing and sealing processes. The pores in the oxide layer absorb the ink and the final sealing closes the pores and therefore provides extra protection against wear.
AAMA finishing specifications American Architectural Manufacturer's Association (AAMA) Performance Standards for Organic Coatings for Architectural Aluminum Extrusions and Panels AAMA 2603-02
- No visible coating imperfections from 10 ft. away _ 20 microns - Dry-film thickness > - Minor scratches and blemishes can be repaired but be kept to a minimum*
AAMA 2604-02
- No visible coating imperfections from 10 ft. away _ 30 microns - Dry-film thickness > > 25 microns with a primer of 7.5 ±2.5 microns - Where multiple coats, topcoats shall be _ - Minor scratches and blemishes can be repaired but be kept to a minimum - 5-year performance specs*
AAMA 2605-02
- No visible coating imperfections from 10 ft. away _ 30 microns - Dry-film thickness > > 25 microns with a primer of 7.5 ±2.5 microns - Where multiple coats, topcoats shall be _ - Minor scratches and blemishes can be repaired but be kept to a minimum - 10-year performance specs*
* For more information, see AAMA's Voluntary Specification, Performance Requirements and Test Procedures for Superior Performing Organic Coatings on Aluminum Extrusion Panels or visit their website at www.aamanet.org . AAMA’s Performance Standard for Anodized Architectural Aluminum AAMA 611-98
- Anodic coatings shall be continuous, uniform, free from powdery areas, of suitable alloy and temper - Major exposed surfaces to have minimum oxide coating of 18 microns for Architectural Class I and 10 microns for Architectural Class II - Oxide coating weight, density, color uniformity, corrosion resistance and weathering requirements also apply**
** For more information, see AAMA 611-98 Voluntary Specification for Anodized Architectural Aluminum or visit their website at www.aamanet.org .
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Surface criteria Class
Definition
Production directions Typical applications
1
Extremely high surface requirements
Superior quality
No scratches, marks or noticeable structural lines on the extrusion’s visible surfaces. Inspection distance: 1-1/2 ft. Cannot be run on the visible surface. Max. delivery length: By agreement.
Handled individually at all stages.
2
Very high surface requirements No scratches, marks or noticeable structural lines on the extrusion’s visible surfaces. Inspection distance: 3 ft. On non-visible surfaces: Qual. 3. Should not be run on the visible surface.
3
4
5
Recommended alloy
6063 6060
Visible surfaces well protected during packaging. Décor strips, picture frames, radio/TV facias.
Very high paint/anodizing quality
6063 6060
Visible surfaces protected during packing. Décor strips, picture frames, radio/TV facias, exclusive furniture, kitchen, bathroom.
High surface requirements
High paint/anodizing quality
No noticeable structural lines or other damage on the extrusion’s visible surfaces. Inspection distance: 6 ft. Graphite damage and other minor damage from the run-out table permissible on visible surfaces. On non-visible surfaces: Qual. 4. Free from chips.
Visible surfaces protected during packing. Can be produced with the visible surface down towards the table. Can, with care, be laid on one another during extrusion, stretching and cutting. Damage/marks that disappear during anodizing can be accepted on visible surfaces. Furniture, lamps, kitchen, bathroom, windows, doors, shop fittings.
Normal surface requirements
Normal quality
No noticeable scratches, marks or other damage on the extrusion. Inspection distance: 12 ft.
Fine mechanical parts, internal components for radio/TV, building systems apart from windows and doors, balconies, sun-blinds, railings and steps, standard extrusions.
Small/no surface requirements
Commercial quality
Inspection distance: 24 ft. Blisters and cracks not permissible.
Commercial elements, parts for rough mechanical machining. Standard extrusions.
6063 6005
All
All
Surface qualities, painted extrusions Paint Class
Definition, paint surface
Very high
Primary surfaces: Inspection distance: 3 ft. No faults in the paint accepted. Layer thickness, average 60-100 μm
Minimum demands for extrusions prior to painting Class 3
Secondary surface: Layer thickness, average 30-60 μm High
Primary surfaces: Inspection distance: 3 ft. Minor faults in the paint accepted. Layer thickness, average 60-100 μm
Class 4
Secondary surface: Layer thickness, average 30-60 μm Normal
Primary surfaces: Inspection distance: 12 ft. Minor faults in the paint accepted. Layer thickness, average 60-100 μm
Class 4
Secondary surface: Layer thickness, average 30-60 μm
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Product specification checklist When you are ready to talk to an aluminum extruder
will help the manufacturer better understand your
or fabricator about your product, review this checklist and answer as many questions as you can. You will have
requirements. You can access our Request a Quote form from any
a better understanding of key areas of concern and this
screen on the www.hydro.com/northamerica website.
Product Specifications Checklist Application
Component requirements
For existing products:
J What surfaces, if any, will be visible?
J What features/capabilities do you like best?
J Dissipate heat? Insulate?
J What problems are you trying to solve?
J Mechanical properties: tensile strength, yield
strength, elongation?
J What enhancements would you like to make?
J Electrical conductivity?
J Can aluminum replace other materials?
J Surface requirements? Colors? Finishing?
For new product designs:
J Fabrication needs? Cut-to-length, holes,
J Do have you completed drawings?
hinges, joints, grooves, bends, etc.?
J How do you anticipate aluminum benefiting
J Assembly needs?
your product? J How is your product to be used?
Environment
J What is the expected longevity of your
J Indoors or outdoors? Temperature range?
product/program?
J Wet, dry? J Exposed to chemicals?
Alloys J Do you have a particular alloy specified? Why?
Loads
J Are you open to recommendations?
J What are the load conditions? J What kind of movements on the components
Component structure
(compression, shear stresses, etc.)?
J How many components in your product? J Will aluminum components come in contact
Delivery requirements
with other materials?
J Quantities and frequency needed?
J Can multiple functions/components be
J Packaging requirements?
merged into a single function?
J Special unloading requirements
J Will extrusions be solid or hollow?
(e.g. flat bed trucks only)?
J Dimensional requirements?
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Hydro plant capabilities
Plant
Extrusion
Fabrication
Finishing
Drawn Tubing
Contract Manufacturing
Casthouse
Belton, SC* Cassville, MO †
Fayetteville, TN *
Guaymas, Mexico* Kalamazoo, MI ** Monett, MO* North Liberty, IN Phoenix, AZ * St. Augustine, FL ** Sidney , OH * * ISO 9001:2000 ** ISO 9001:2000 and ISO 14001:2004 †
Partnered
ISO/TS 16949:2002
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www.hydro.com/northamerica
North American extrusion facilities
Kalamazoo, MI Holland, MI North Liberty, IN
Baltimore, MD Sidney, OH
Cassville, MO Monett, MO
NA Headquarters
Fayetteville, TN Phoenix, AZ
Belton, SC
Extrusion & Fabrication Drawn Tubing Contract Manufacturing
Guaymas, Mexico
St. Augustine, FL
Casthouse Technology Center
When you choose Hydro, you partner with the nation’s premier extrusion components supplier backed by the resources of a global aluminum authority. We are committed to finding new and better ways to improve our processes through research, knowledge exchange, innovation and investment to help customers transform designs and ideas into elegant, cost-effective products. We are firmly committed to sustainability and mutual benefit and believe that our work should contribute to our communities and protect our environment as it benefits our employees and customers. Our Extruded Products network consists of 10 extrusion/fabrication facilities with more than 2,000 employees and roots that go back more than 50 years. Three plants have adjacent casthouses with capacity to produce more than 150,000 metric tons of primary-grade metal with high recycled content annually. All facilities are supported by Hydro’s global network of Competency Centers, including the Holland, Michigan Technology Center, a critical resource for research, analysis, development of new technology, and knowledge sharing. We are a unit of Hydro Aluminum, a global extrusion technology leader and one of the world’s largest aluminum compan ies with more than 20,000 employees in 40 countries. To learn more about Hydro in North America, visit us at: www .hydro.com/northamerica
Belton, SC Toll-Free Phone: (888) 935-5754 Cassville/Monett, MO Toll-Free Phone: (888) 935-5755
Accreditation and memberships Aluminum Association www.aluminum.org
Fayetteville, TN Toll-Free Phone: (877) 829-8366 Kalamazoo, MI Toll-Free Phone: (888) 935-5758 North Liberty, IN Toll-Free Phone: (888) 935-5757 Phoenix, AZ/Guaymas, Mexico Toll-Free Phone: (800) 459-3030 St. Augustine, FL Toll-Free Phone: (800) 835-6502
Aluminum ExtrudersCouncil (AEC) www.aec.org
American Architectural Manufacturer’s A ssociation (AAMA) www .aamanet.org
Sidney, OH Toll-Free Phone: (888) 935-5759 Hydro Solar Solutions Phone: (602) 427-1434 Transportation Components Phone: (269) 492-1100 A complete listing of Hydro global extrusion facilities can be found at : w ww.hydro.com/en/About-Hydro/Hydro-worldwide
To request a quote, link to the Request a Quote screen on our website. 65
Solar Electric Power Association (SEPA) www.solarelectricpower.org
Aluminum Anodizers Council (AAC) www.anodizing.org
