CASTING REPORT OBJECTIVES 1. To show how the casting process have done. 2. To more know about knowledge of manufacturing process 3. To more understand every step to make sand casting process. 4. To exposes the student about environment in the workshop. 5. To apply a theory that lerned in the class into practical at the workshop. 6. To develop self-learning process among the student. 7. Student will able to learn how to use u se equipment of casting and machines that t hat are used in the casting process.
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INTRODUCTION Sand casting the most old method in metal casting family. It is produce large component typically, iron, ore, and etc. usually product of expandable mold is the most roughest surfaces amongst all. Instead, the material that used for the mold can be used repeatedly. repe atedly. Basically, sand casting consist of placing a pattern in sand to make an imprint, incorporating a gating system. Removing the pattern and filing the mold the mold cavity with molten metal, allowing the metal to cool until it solidifies, breaking away the sand mold and finally removing the casting. This casting process is one of the popular casting method because it have many advantage such as save cost, quick results, high temperature resistance and high melting point resistance.
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THEORY The casting process basically involves pouring molten into a mold patterned after part to be manufactured, allowing it to solidify, and removing the part from the mold. Important considerations in casting operations are as follows : Flow of molten metal into the mold cavity Solidification and cooling of the metal in the mold Influence of the type of mold material
Casting is a process by fluid melt into a mold, it need to cool in the shape of the form, and then ejected to make a casting. There are four main elements are required in this process, it is pattern, mold, cores, and the part. The pattern is original from the mold have been prepared, so the corresponding cavity in casting in material have been creates. Cores are used to produce tunnels or holes in the finished mold, and the part is the final output of the process. A pattern is a replica of the object to be made by the casting process with some modifications. Some of the modifications that we consider in patt ern making process are shrinkage allowance, parting line, draft, machining allowance and distortion.
Schematic illustration of a typical riser – gated casting. Risers serve as reservoirs, supplying molten to the casting as it shrinks during solidification. The casting process is subdivided into two distinct subgroups: Expandable mold casting Nonexpendable mold casting CASTING REPORT
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Expandable mold casting Expandable mold casting is classification include sand, plastic, shell and investment of lost-wax technique moldings. All of these involve the use of temporary and need gravity to help force molten fluid into casting cavities. In this process the mould is used only once. Expandable mold casting can be divided into: Sand casting Plaster casting (of metals) Plaster casting (of plastic or concrete) Shell molding Investment casting
Permanent mold casting Its also know as hard-mold casting. Consists of two halves of mold-made from materials with high resistance to erosion and thermal fatigue such as cast iron, steel, bronze, graphite, refactory metal alloys. Vacuum casting Die casting Centrifugal casting Continuous casting.
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Sand Casting The traditional method of casting is in sand molds has been used for millennia. Typical applications of sand casting include machine b ases, large turbine impellers, propellers, plumbing fixtures, and a wide variety of other products and components. Basically, sand casting consist of placing a pattern (having the shape of the desired casting) in sand to make an imprint, incorporating a gating system, removing the pattern and filling the mold cavity with molten metal, allowing the metal c ool until it solidifies, breaking away the sand mold, and removing the casting. Show the outline of production steps in typical sand casting operation.
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Sands There are two general types of sand: -
Naturally bonded (bank sand)
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Synthetic (lake sand)
Types of sand molds Green sand
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Which is a mixture of sand, clay, and water. The term “green” refers to the fact that the sand in the mold is moist or damp while the metal is being poured into it. Greensand molding is the least expensive method of making molds, and the sand is recycled easily for subsequent reuse.
Cold-box sand
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In the cold-box process, various organic and inorganic binders are blended into the sand to bond the grain chemically for greater strength. These molds are dimensionally accurate than green-sand mold, but more expensive.
No-bake sand
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A synthetic liquid resin is mixed with the sand and the mixture hardens at room temperature.
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Patterns Used to mold the sand mixture into the shape of the casting. It can be in a form of wood, plastic or metal. The selection of a pattern material depends on : -
Size of the casting
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Shape of the casting
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Dimensional accuracy
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Quantity of casting required
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Molding process
Type of patterns One-piece pattern (loose or solid patterns) Split patterns Match-plate patterns
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Cores
Sand cores showing core prints and chaplets to support cores. Cores are placed in the mold cavity to form the interior surface of the casting and the removed from the finished part during shakeout and further processing. The cores must strength, permeability, ability to withstand heat, and collapsibility. Casting with internal cavities or passages, such as those found in an automotive engine block or valve body, cores are utilized. The core is anchored by core prints, which are recesses added to the pattern to support the core and to provide vents for the escape of gases. “Chaplet” is an additional supports to prevent core from shifting.
Cooling rate Cooling rate is the rate which casting cools affects its microstructure, quality and
properties. The cooling rate is largely controlled by molding media used for making the mold. When the molten metal is poured into the mold, the cooling down begins. This happens
because the heat within the molten metal flows into the relatively cooler parts of the mold. Molding materials transfer heat from the casting into the mold at different rates. For example, some molds made of plaster may transfer heat very slowly, while a mold
made entirely of steel would transfer the heat very fast. This cooling down ends with solidification where the liquid metal turns to solid metal. CASTING REPORT
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Shrinkage Like nearly all materials, metal is less dense as a l iquid than a solid and so a casting shrinks as it cools, mostly as it solidifies, but also as the temperature of the solid material drops. Compensation for this natural phenomenon must be considered in two way : Volumetric shrinkage
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The shrinkage caused by solidification of molten metal can leave cavities in a casting and weakening it. Risers provide additional material to the casting as it solidifies.
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The riser (sometimes called a "feeder") is designed to solidify later than the part of the casting to which it is attached. Thus the liquid metal in the riser will flow into the solidifying casting and feed it until the casting is completely solid.
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In the riser itself there will be a cavity showing the metal which was fed. They are often necessary to produce parts which are free of internal shrinkage voids
Linear shrinkage
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Shrinkage after solidification can be dealt with by using an oversized pattern designed for the relevant alloy.
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Pattern makers use special "shrink rulers" to make the patterns used by the foundry to make castings to the design size required. Using such a ruler during pattern making will ensure an oversize pattern.
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Thus, the mold is larger also, and when the molten metal solidifies it will shrink and the casting will be the size required by the design.
Draft The amount of draft is determined by the size and the shape of the pattern, the depth of
cavity, the method used to withdraw the pattern, the pattern material, the mold material and the molding procedure. Since draft allowance tend to increase the size of a pattern and thus the size of a pattern and thus the size and weight of a casting, it is generally desirable to keep them to the minimum that will permit satisfactory pattern removal.
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Machining Allowance When machined surfaces must be provided on castings, it is often necessary to provide
machining allowance on the pattern. This allowance depends to a great extend on the casting process and the mold material. Ordinary sand castings have rougher surfaces than those of shell mold castings. We should relate the finishing allowance to the casting process and also remember that draft may provide or all of the extra metal needed for machining. If a core is used to form interior cavity, it too must be oversized to compensate for shrinkage .However if a machining allowance is included, it should be subtracted from the core dimensions because mac hining will increase the size of the hole. If the casting is made directly into metal m old, all of the pattern allowances should be incorporated into the mold cavity.
Distortion Some casting shapes still require an additional allowance for distortion. Fro example,
the arms of the U- shaped section may be restrained by the mold, while the base of the U is free to shrink. This restraint will result the final casting with outwardly sloping arms. Long, horizontal sections tend to sag in the center unless adequate support is provided by suitable ribbing. Distortion greatly depends on the particular configuration of the casting, and we must provide required distortion allowance.
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M olding box and materi als
A multi-part molding box (known as a casting flask, or referred to as the cope and drag) is prepared to receive the pattern. For a simple product, flat on the one side, closed at the bottom and filled with the casting sand. The pattern is placed on the sand and another molding box segment is added. Additional sand is rammed ove r and around the pattern. Finally a cover is placed on the box and it is turned and unlatched, so that the halves of the mold may be parted and the pattern with its sprue and vent patterns removed. Chills
If it is desired to have most of the iron or steel casting in a tough, ductile, state but with a few surfaces hard, it is possible to introduce into the mold, metal plates chills where the metal is to be hardened. The associated rapid local cooling will form a finer-grained and harder m etal at these locations. The inner diameter of an engine cylinder is made hard by a chilling core.
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APPARATUS 1) Wooden block 2) Paper 3) Pencil 4) Compass 5) Eraser 6) Ruler 7) Ø 0.3 mm drill 8) Wood chisel 9) Handsaw 10)Sand papers 11)Cope and drag 12)Small and big rammer 13)Small and big downgate 14)Cleaner 15)Casting ladle 16)Shovel 17) Separating agent 18)Sand 19)Casting ladle 20)Variety grades of sand paper or grinder tools 21)Oxyfuel-gas cutting tools or handsaw
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PROCEDURES Making the pattern 1.
Each group was given a piece of soft wood, a set of chisel, mallet, files, meter rule and a
small saw
2.
On the soft wood, students have to draw a layout for the pattern. A layout was drawn on a
piece of paper
3.
The sketch was transferred to the soft wood and was cut carefully using small saw as the
wood is soft and might cracked if don’t handle properly
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4.
The pattern then, was shaped by it into desired figure
5.
The pattern was smoothen using sand paper and files
6.
For locating the pins ,the pattern was drilled
7.
Next, the centre of width of the pattern was marked using micrometer high gauge for a
precise centre line 8.
Again, the pattern was smoothen using sand paper for smoother surfaces
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Casting process 1.
The manual sand casting was provided to all groups.
2.
The pattern was placed at the lower part of the sand casting which is called drag to locate
the suitable position for sprue and riser 3.
The pattern was taken out to cover it with parting agent first so that the sand wo n’t stick
to pattern and process of separating pattern from sand would be easier.
4.
Then, the pattern was placed in the drag and filled with sand. The sand was compress to
make it compact and when the drag was rose up, the sand are not spilling down. CASTING REPORT
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5.
Next, the drag was turn upside down. The other part of pattern was assembled together
with the pattern in the drag and the screws at the side of cope and drag were tightened.
6.
The parting agent was added on the pattern and the sand. The sprue and riser were
located at the suitable place.
7.
Sand was added and compressed. Then, sprue and riser were removed carefully
8.
The screws at the side of the cast was loosened and the cope and drag part were separated
to removed the pattern from the sand carefully so mold remain as it shape. 9.
The runner then, was made from mold cavity to the sprue and riser.
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10.
Both cope and drag part were assembled together and the screws were tightened neatly.
11.
After that, molten metal in the furnace was poured continuously through the sprue until
the molten metal appeared at the riser.
12.
The metal was left to cool. The equipment for finishing already taken out.
13.
Then, the alloy cast was taken out and cleaned using steel brush.
14.
The gating system was cut by using saw.
15.
The alloy cast was smoothen using sand paper for finishing.
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DATA AND RESULTS
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DISCUSSION Safety Precautions
1. Students must wear proper attire when entering the workshop. Attire must be neat, tidy and protective 2. Students must wear gloves and other protective gear when carrying out projects in the workshop. 3. Students are prohibited to play around, eat, drink or smoke in the workshop. 4. Never use tools and apparatus without permission. 5. Never use any damaged or malfunctioned tools, apparatus and materials. 6. Use the proper tools for every task. 7. Students must obey instructor’s instructions. 8. It is advisable not to wear gloves while using the electric drill as student may not grip the electric drill well. 9. When using chisel and hammer, it must be done on the anvil.
When designing the shape of the project, we must avoid design the shape that has the small gap since it will causing the difficulty when removing the shape from the sand. The design of the shape should not be too thin to prevent it from broken when sawing it into two parts. When melting the metal with furnace, extra precaution must be taken since the high melting CASTING REPORT
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temperature of the molten metal can cause the injuring to the user. During the process placing the desired casting in sand, tamping the sand compact to prevent it from crush when remove the shape from the sand. Try to brush the designing shape as smooth as possible so it will not stick with the sand. The distance of the risers pouring basin cannot be too near with the shape so there are space for tamping the sand. The process of pouring the molten metal into the mold must be proceed in one shot without delaying in order to prevent molten metal solidified halfway and block the passage.
CONCLUSION Sand casting has existed for centuries. While the basic process has changed little over time, it continues to be the most popular method for metal part production. Its popularity is due, in part, to the wide range of part sizes that can be cast and the broad selection of metal alloys that can be processed. Another factor is that sand casting is a faster and less expensive process than die casting or investment casting. The process derives its name from the use of sand to create the molds into which molten metal is cast. The molds are created by packing sand around a pattern. The sand holds its shape with the addition of clay and water (green sand) or a chemical binder (dry sand). After the sand has been packed, the pattern is removed, and metal is poured into the cavity in the sand mold. Once cooled, the sand is broken away from the cast metal part. For sand casting, the most common metals are iron, steel, bronze, brass and aluminium. With these alloys, sand casting can produce small parts that weigh less than one pound or large parts that weight several tons. The process is used to make medium to large parts such as valve bodies, plumbing fixtures, locomotive components and construction machinery. Its versatility also allows sand casting to produce small parts such as buckles, handles, knobs and hinges. It is a cost effective and efficient process for small lot production, and yet, when using automated equipment, it is an effective manufacturing process for high-volume production.
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REFERENCE 1. en.wikipideia.org/wiki/Sand_casting 2. www.sandcasting.bizhosting.com 3. EN. MASJURI BIN MUSA @ OTHMAN : Lecture Notes Manufacturing Process BMFG 2323 - Metal Casting & Equipment 4. E. PAUL DEGARMO, J.T. BLACK A. KOHSER: Materials and Processing In Manufacturing, Prentice- Hall India, 8th Edition. 2002 5. Engineering.blogspot.com/search/label/Casting%20defects 6. www.custompartnet.com/wu/SandCasting 7. www.efunda.com/processes/metalprocessing/sand_casting_intro.cfm.
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