MANUFACTURING AUTOMATION Akshay Vijayakar 091040029
INTRODUCTION •
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One of the major developments that led to CIM was the introduction of computer control of manufacturing equipment and operations. Till the advent microprocessors personal manufacturing automation wasofmainly through theand so-called harcomputers, d automation through hydraulic, pneumatic or electric methods. Programmable logic controllers (PLC) have now become a very convenient tool for flexible automation. PLC’s are widely used in pneumatic, hydraulic, electric, and electronic automation.
CNC machine tools, robots, transfer machines, industrial drives etc. use PLC’s.
INTRODUCTION •
Automation involves not only carrying out the manufacturing process without human intervention but also many connected operations like stock feeding, proper sequencing of various steps involved in manufacturing, removal of the processed part from the machine or equipment, measurement of the completed part and the removal of lubricants.
EXAMPLE - PRESSURE DIE CASTING •
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The molding machine may be hydraulically operated while the molten metal may be automatically transferred from the melting furnace to the injection chamber. The cast part is automatically picked up after the separation the parts are cooled and trimmed.
of the dies and
Automation is employed to lubricate the dies, cool the dies after part removal etc. Sensors are employed to measure injection speed, shot rod position, hydraulic pressure and other data required to adjust process para meters to ensure castings of consistent quality , shot after shot and to collect performance for statistical analysis for quality assurance pu well as futuredata process impro vement.
rposes as
AUTOMATION IN MANUFACTURING
FLEXIBILITY AND PRODUCTIVITY
TRANSFER MECHANISMS
TRANSFER LINE
DIMENSIONING EXAMPLE
NUMERICAL CONTROL
TYPES O F AUTOMATION SYSTEMS
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Pneumatic Systems
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Hydraulic Systems
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PLC (Programmable Logic Controller) Systems
PNEUMATIC SYSTEMS In majority of the applications compressed air is used for one following functions: •
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To determine the status of processors (sensors). Information processing (processors).
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Switching of actuators by means of final control elements.
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Carrying out work (actuators).
or more of the
The technological progress made in material, design and production processes has further improved the quality and diversity of pneumatic components and thereby contributed to their widespread use in automation.
ADVANTAGES OF COMPRESSED AIR •
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Availability: Air is abundantly available hence the source of wo rking medium is not a problem. Transportation: Compressed air can easily be transported in pipe lines over large distances without any trouble. Storage: Storage of compressed air is extremely simple and least cumbersome. Temperature: Compressed air is r elatively insensitive to temperature variations.
ADVANTAGES OF COMPRESSED AIR •
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Explosion Proof: There is no risk of any explosion with regard to the use of compressed air. Cleanliness: Clean compressed air allows a very clean working system. Components: Most pneumatic components have a simple construction and are also economically cheap. Speed: Compressed air is a very fast working medium. Overload Safe: Pneumatic Systems can be loaded to the point of stopping hence they are overload safe.
DISADVANTAGES O F COMPRESSED AIR •
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Preparation: Dirt and condensate should not be present in the medium; this requires a thorough preparation of air before use. Compression: It iscompressed not always possible to achieve uniform and constant piston speeds with air. Force Required: The maximum force that a pneumatic system can provide is limited to a m aximum of 40,000 Newton at 6 bar. Noise: Pneumatic systems are generally noisy , however now with the presence of silencers and better pneumatic components the noise levels
OIL HYDRAULIC SYSTEMS •
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Hydraulic systems have a significant advantage over pneumatic systems in their ability to handle higher loads and torques. Hydraulic oil is also practically incompressible. Hydraulic systems operate at significantly higher pressures ranging from 35 Mpa to 200 or more Mpa. This reduces the size of the actuators. Hydraulic systems require a power pack to supply pressurized oil of adequate quantity.
OIL HYDRAULIC SYSTEMS •
As in pneumatic systems, the actuators are either motors or cylinders.
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The muscle power of hydraulic systems combined with the flexibility and ease of electrical andfor electronic control makes electro obvious choice even very demanding applications.
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hydraulic systems an
Industrial hydraulic systems use a wide variety of components like cylinders, rotary actuators, pumps, valves or the control of flow direction, volume, pressure etc, accumulators, filters and tubing.
PROGRAMMABLE LOGIC CONTROLLERS (PLC) Industrial control circuits are designed to serve several functions
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Switching: It is necessary to switch on control elements to operate actuators like hydraulic cylinders, electric motors, pneumatic valves etc. For example, a pneumatic or hydraulic cylinder may be used to actuate the door closing function in a CNC machine.
PROGRAMMABLE LOGIC CONTROLLERS (PLC) •
Sequencing: Certain function s in machines should be performed in a particular order. For example, if two cylinders are to be operated in sequence, the sequence may be any one of the following: A B
B- A
A A- B B A B
B- A
B A A- B B B- A A B A B- A-
PROGRAMMABLE LOGIC CONTROLLERS (PLC) •
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Process Control: A PLC may be used to control a pr ocess on the basis of signals received from a process. The signals may be analog or digital. PLC is a microprocessor -based unit that carries out control functions of many levels and complexity .
PLC is used to monitor process parameters in industries and adjust process control parameters on the basis of a built-in logic. It is user-friendly and can be operated by even unskilled persons.
ADVANTAGES OF PLC •
Flexibility: A PLC can be used for controlling one machine or a group of machines. A PLC program can be altered easily through a keyboard sequence so that the machine functions can be modified at the w ill of the designers without incurring additional cost of hardware or scrapping e hardware.
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Low cost: Technological developments in microelectronics technology have reduced the cost of PLC’s considerably .
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Speed of operation: PLC’s operate faster than relays.
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Security: A PLC program cannot be altered without unlocking the program .
ADVANTAGES OF PLC •
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Reprogramming: In the case of transfer machines the modifications in the control circuit can be carried out by simple reprogramming so that same hardware can be used for a n ew sequence. Modularity: PLC’s can be assembled in a modular fashion. The designer can add modules depending upon his requirement of the number of inputs and outputs. Analog and digital inputs: PLC can input/output both analog and digital signals. Correction of errors: Efficient debugging procedure enables easy error correction.
ADVANTAGES OF PLC •
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Off-line programming: PLC program can be designed off-line and tested before implementation. Boolean programming: programming can be carried out using a ladder diagram by an experiencedPLC technician. Documentation: PLC programming devices can generate a printout as soon as the ladder diagram is completed. This avoids the need for separate documentation efforts. Reliability: Since PLC is a solid -state device the reliability is very high. Maintainability: The modular nature of the PLC design makes maintenance easy.
PARTS O F A PLC SYSTEM
PARTS OF A PLC SYSTEM The central processing unit (CPU): Like a computer this is the brain of a PLC. It has several sub-parts. •
(a) A micropro cessor to carry out arithmetic and logic operations.
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(b) Memory to store data and programs.
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(c) Process image memory.
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(d) Internal timers and counters.
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(e) Flags.
PARTS OF A PLC SYSTEM Input module: This acts as an interface between the field inputs and the CPU. The input module accepts voltage signals from the limit switches, sensors, transducers, proximity switches, push buttons etc. The input signals can be analog or digital. The input module performs four tasks. •
It senses the presence or absence of input signals at each of its input terminals. The input signal tells what switch, sensor , or other signal is on or off in the operation being controlled.
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It converts the input signal to a DC level useable by the PLC’s electronic circuit.
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The input module carries out electronic isolation of output from input.
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It produces an output sensed by CPU.
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A typical input module will have 4, 6, 8, 12, 16, or 32 terminals.
PARTS OF A PLC SYSTEM Output module: The output module interfaces the output devices like contactors, lamps, relays, solenoid valves etc. with the CPU. The output module acts in just opposite manner to input module. A signal from CPU is received by the output module, once for each scan. If the CPU codewill matches the assigned number of the module the module is turned on. The outputsignal modules have 4,6,8,12,16 or 32 terminals.
Power supply
Racks and chassis to mount the elements
OPERATION OF A PLC
LADDER LOGIC
RESEARCH PAPER A MODEL DRIVEN APPROACH FOR REQUIREMENTS ENGINEERING OF INDUSTRIAL AUTOMATION SYSTEMS •
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Model driven requirements enginee ring (MDRE) is proposed to deal with the everincreasing complexity of technical systems in the sense of providing requirement specifications as formal models that are correct, complete, consistent, unambiguou s and easy to read and easy to maintain This approach involves using languages like SysML (Systems Modelling Language) and UML (Unified Modelling Language) The requirements of any operation which is meant to be automated, is entered into a program called Modelica which creates a possible model for the operation Using an integration of this program and its testing facility, the Institute for Mechatronics and System Dynamics has created a new program called Model Driven Requirements Engineering for Bosch Rexroth (MDRE4B R) which aims to contribute to latest investigations in this field.
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