Types of Sheet Metal Working (Press Machine Operations)
Types of sheet metal working or Press machine operations may be grouped into two categories i.e. cutting operations and forming operations. In cutting operations, the sheet metal is stressed beyond its ultimate strength whereas, in forming operations the stresses are below the ultimate strength of the metal.
Metal Cutting Operations
- In metal cutting operations the metal gets sheared hence these operations are also called shearing operations.
- In these operations, the metal sheet is stressed beyond its ultimate strength.
- Metal cutting operations include the following operations:
1. Blanking
2. Punching (Piercing)
3. Notching
4. Perforating
5. Slitting
6. Lancing
7. Shaving
8. Shearing
1. Blanking
- Blanking is the cutting operations of a flat metal sheet and the article punched out is known as blank.
- Blank is the required product operation and the metal left behind is considered as a waste.
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Blanking
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2. Punching (Piercing)
- It is the cutting operation with the help of which holes of various shapes are produced in the sheet metal.
- It is similar to blanking, only the main difference is that, the hole is the required product and the material punched out to form a hole is considered as a waste.
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Punching (Piercing)
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Difference between Blanking and Punching (Piercing)
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Difference between Blanking and Punching (Piercing) |
3. Notching
- It is similar to blanking operation, but in this full surface of punch does not cut the metal.
- In this operation, metal pieces are cut from the edges of a sheet.
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Notching
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4. Perforating
- It is similar to piercing but the difference is that, to produce holes the punch is not of round shape.
- In this process, multiple holes which are very small and close together are cut in the sheet metal.
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Perforating
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5. Slitting
- It is the operation of making an unfinished cut through a limited length only.
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Slitting
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6. Lancing
- In this operation, there is a cutting of sheet metal through a small length and bending this small cut portion downwards.
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Lancing
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7. Shaving
- This operation is used for cutting unwanted excess material from the periphery of a previously formed workpiece.
- In this process very small amount of material is removed.
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Shaving
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8. Shearing
- It is an operation through which a metal is cut along a single line which is generally a straight line.
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Shearing
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Metal Forming Operations
- In metal forming operations, the sheet metal is stressed below the ultimate strength of the metal.
- In these operations, no material is removed hence there is no wastage.
- Metal forming operations include following operations:
1. Bending
2. Drawing
3. Embossing
4. Forming
5. Coining (Squeezing)
1. Bending
- It is a metal forming operation in which the straight metal sheet is transformed into a curved form.
- In bending operations, the sheet metal is subjected to both tensile and compressive stresses.
- During the operation, plastic deformation of material takes place beyond its elastic limit but below its ultimate strength.
- The bending methods which are commonly used are as follows:
a) U-bending
b) V-bending
c) Angle bending
d) Curling
a) U-bending
- Figure shows U-bending operation which is also called as channel bending.
- In this operation, the die cavity is in the form of U, due to which component forms the shape of U.
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U-bending
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b) V-bending
- Figure shows V-bending operation in which wedge shape punch is used.
- The angle of V may be acute, 90″ or obtuse.
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V-bending
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c) Angle bending
- In this operation, there is a bending of a sheet metal at a sharp angle.
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Angle bending
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d) Curling
- In this operation, the edge of a sheet metal is curled around.
- The punch and die both are made to contain the cavity for cutting partially.
- After the operation, punch moves up and workpiece is ejected out with the help of plunger as shown in Figure.
- This process is used in the manufacturing of drums, pots, vessels, pans, etc.
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Curling
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2. Drawing
- In this operation, punch forces a sheet metal blank to flow plastically into the clearance between the punch and die.
- Finally, the blank takes a shape of cup.
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Drawing
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3. Embossing
- With the help of this operation, specific shapes or figures are produced on sheet metal.
- It is used for decorative purposes or giving details like names, trademarks, specifications, etc. on the sheet metal.
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Embossing
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4. Forming
- In forming operation, sheet metal is stressed beyond its yield point so that it takes a permanent set and retains the new shape.
- In this process, the shape of punch and die surface is directly reproduced without any metal flow.
- This operation is used in the manufacturing of door panels, steel furniture’s, air-craft bodies, etc.
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Forming
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5. Coining (Squeezing)
- In coining operation, the metal having good plasticity and of proper size is placed within the punch and die and a tremendous pressure is applied on the blank from both ends.
- Under severe compressive loads, the metal flows in the cold state and fills up the cavity of the punch and die.
- This operation is used in the manufacturing of coins, medals, ornamental parts, etc.
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Coining (Squeezing)
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Deep Drawing
- It is a process of making the cup-shaped parts from a flat sheet-metal blank.
- To provide necessary plasticity for working, the blank is first heated and then placed in position over the die or cavity.
- The punch descends and pushes the metal through the die to form a cup; hence this process is also called as cupping.
- To obtain cup shaped pieces of the desired size and wall thickness, the process may be continued through a series of successively smaller dies and punches.
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Deep Drawing
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Wire Drawing
- Wire drawing is the process of producing the wires from the rod through the successive reduction of diameter.
- All the available wires are produced by cold drawing through the dies.
- During the process, hot drawn bar or rod is pulled through the die. The outer diameter of die is similar to the finished product size.
- Depending upon the material to be drawn and amount of reduction required, the process can be carried in a single pass or multiple passes.
- The drawing operation is started by pointing the end of the rod and Hot rolled rod pushing it through the tapered hole in the die.
- The end is gripped by tongs and sufficient wire is pulled through the die. After pulling a certain length, the end is wound on a reel or draw pulley.
- The die is made of highly wear resistant material like alloy steel, Die holder cemented tungsten carbide, etc.
- The size of produced wire varies from 6 mm to 20 mm.
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Wire Drawing
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