Production Process

Manufacturing is the term which refers the transformation of raw materials into finished products by using labor, machines, chemical processing. These finished products are used for producing more complex products.

The economics of the manufacturing process is a vital matter. Nowadays the market is very competitive. So we have to think competitive price of products besides their functional and aesthetic appeal. Therefore, production process is an essential subject for engineer, especially for industrial and production engineer. Because this will enrich his capability and also reduce his limitations in the field of manufacturing process.

Role of an Industrial engineer in manufacturing process:

  • Participate in design review to ensure manufacturability of the product
  • Define proper work methods for tasks
  • Determine appropriate methods and for production
  • Mange resources and maintain schedule
  • Process optimization
  • Facilitate and Lead process improvement team

There are a large number of processes available for manufacturing. These processes can be broadly classified into four categories

(1) Casting process

(2) Forming process

(3) Fabrication process

(4)Material removal process

(1) Casting processes:

Casting is the process in where molten metal are poured into a refractory mould cavity and is allowed to solidify. After solidification, objects are removed from mould. Casting processes are used world widely. This is called mother of manufacturing process.

OLYMPUS DIGITAL CAMERA

Figure 1: casting process in the foundry industry

There are many types of casting process. Some of them are

  • Sand mould casting
  • Shell mould casting
  • Plaster mould casting
  • Die casting

Sand mould casting:

Sand casting is the universal casting process. Complex metal parts can be made by this process. This process involves furnace, metal, sand mould and pattern. The metal is melted in the furnace then poured in the cavity of sand mould which is made by pattern. After solidification, object is removed.

Engine block, cylinder head and transmission cases etc are made by this process.

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Figure 2: pouring molten metal in to cavity.

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Figure 3: sand mould.

Shell mould casting:

Shell mould casting is a metal casting process in which the mould is thin hardened shell of sand and thermosetting resin binder, backed up by some other material. This is particularly suitable for steel casting under 20 lbs.

Cylinder heads, gears, bushings, connecting rods and valve bodies are made by this process.

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Figure 4: shell mould casting.

Plaster mould casting:

Plaster mould casting is a metal casting process in which plaster or paris is used as moulding material. This process is similar to sand casting. It can be applied to non-ferrous materials. It is used for casting as small as 30 g. Normally, the form take less than 7 days to prepare.

Lock components, gears, valves and ornaments are made by this process.

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Figure 5: plaster mould casting

Die casting process:

Die casting process is permanent mould manufacture process. It is characteristic in that it uses large amounts of pressure to force molten metal through the mould. Since so much pressure is used to ensure the flow of metal through the mould, metal casting with great surface detail, dimensional accuracy and extremely thin walls can be produced. The size of industrial castings creating using this process vary from extremely small to around 50 lbs.

Carburetors, machine components, various housings, and motors are made by this process.

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Figure 6: die casting diagram

(2) Forming processes:

Forming process is a manufacturing process in where metal are heated and forced to flow through some set of tools for giving desired shape. In this process the amount of metal wastage is at minimum level. Moreover, it is a faster production process. These are generally economical and in many cases improve the mechanical properties too.

Some of metal forming process processes are

  • Metal drawing
  • Metal rolling
  • Extrusion

Metal drawing:

Metal drawing is a manufacturing process that form metal work stock by reducing its cross section. This accomplished by forcing the work through a mould, of smaller cross sectional area than the work. Friction and its effects on flow have to be controlled. For this reason some lubricants are used. Lubricants reduce friction and extend the life of the mould.

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Figure 7: metal drawing

Metal rolling:

Metal rolling is the most important manufacturing process in the modern world. Huge amount of

metal products are produced by this process. The principle of this operation is that the work material is plastically deformed by compressive force between two constantly spinning rolls. These force act to reduce the thickness of the work and affect its grain structure.

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Figure 8: Metal rolling

Extrusion:

Metal extrusion is a metal forming process in which a work piece, of a certain length and cross section, is forced to flow through a die of a smaller cross sectional area thus forming the work to the new cross section. This operation can be performed either hot or cold.

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Figure 9: Extrusion process

(3)Fabrication processes:

Fabrication processes are the secondary manufacturing process. By these processes, many components which are processed by previous operations are joined together to make a complete metal structure. To fabricate the components both heat and pressure or joining material are used.

Some of the fabrications processes are:

  • Gas welding
  • Electric arc welding
  • brazing

Gas welding:

Oxyacetylene gas welding is commonly used for permanent join into mild steel. A mixture of oxygen and acetylene, burns as an intense flame, at about 3,500 degree centigrade. When the flame comes in contact with steel, it melts the surface forming a molten pool, allowing welding to take place. Oxyacetylene can also be used for brazing, bronze welding, shaping metal and cutting.

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Figure 10: gas welding

Electric arc welding:

Arc welding a type of welding that uses a welding power supply to create an electric arc between an electrode and base material to melt the metals at the welding point. DC or AC current can be used. Arc welding process may be manual, semi-automatic, or fully automated. Its plays an important role for the fabrication of steel structures.

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Figure 11:Electric arc welding

Brazing:

Brazing is a metal joining process whereby a filler metal is heated above melting point and distributed between two or more close-fitting parts by capilary action.

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Figure 12: copper-brazing

The filler metal is brought slightly above its melting liquidus temperature while protected by a suitable atmosphere, usually a  flux.It then flows over the base metal and it then cooled to join the workpiece togethere.

(4)Material removal processes:

These are the manufacturing processes whereby additional unwanted materials are removed in the form of the chips from the blank material by a harder tool to obtain a desired shape.These processes are very expensive because  more energy is consumed by these processes.But these give good dimensional accuracy. That’s why these are used widely.

Some material removal processes are:

  • Turning
  • Drilling
  • Milling

Turning:

Turning is the process by which metal is removed from the outer diameter of a rotating cylindrical workpiece.

This is used to reduce the diameter of the work-piece, usually to specified dimension, and to produce a smooth finish on the metal.

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Figure 13: Turning operation

Drilling:

Drilling is a cutting process that uses a drill bit to cut or enlarge a hole of circular cross-section in solid materials. The drill bit is a rotary cutting-tool, often multi-point. The bit is pressed against the workpiece and rotated at rates from hundreds to thousands of revolutions per minute. This forces the cutting edge against the workpiece, cutting off chips from the hole as it is drilled.

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Figure 14: Drilling operation

Milling:

Milling is the most common form of material removal process.

It can create a variety of features on a part by cutting away the unwanted material. The milling process involves a milling machine, work-piece, fixture, and cutter. The work-piece is a piece of pre-shaped material that is secured to the fixture, which itself is attached to a platform inside the milling machine. The cutter is a cutting tool with sharp teeth that is also secured in the milling machine and rotates at high speeds. By feeding the work-piece into the rotating cutter, material is cut away from this work-piece in the form of small chips to create the desired shape.

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Figure 15: Milling operation

   All these manufacturing processes are being upgraded day by day in order to manufacture better products at minimum possible cost. So the necessity of acquiring knowledge on manufacturing process is increasing also.