Classification Of Press Tools Operations related to Sheetmetal

Table of Contents

Classification Of Press Tools Operations related to Sheetmetal

1. Classification based on operations performed:

1.Shearing

Piercing
Punching
Perforating
Blanking
Cutting off
Parting off
Notching
Slitting
Lancing

2. Bending

Angle bending
Curling
Forming
Plunging

3.Drawing

Cupping

4.Squeezing

Coining
Embossing
Flattening

2. Classification based on construction:

Simple
Follow or progressive
Combination
Compound

EXPLANATION ACCORDING TO OPERATIONS:

1. Shearing operation:

The shearing operation between a punch and a die is illustrated in Fig. As the punch descends upon the workpiece, the pressure exerted by the punch causes the metal to be deformed plastically in the die.

Piercing: The piercing is the operation of production of hole in a sheet metal by the punch and the die. The materials punched out to form the hole constitute the waste.
Punching: The punching operation is similar to the piercing operation. While punching the formation of the hole is the desired result. The difference between the punching and the piercing is that in the case of punching a cylindrical hole is produced, whereas in the case of piercing the hole produced may be of any other shape.
Blanking: The blanking is the operation of cutting of flat sheet to the desired shape. The metal punched out is the required product and the plate with the hole left on the die goes as waste.
Perforating: The perforating is the operation of production of a number of holes evenly spaced in a regular pattern on a sheet metal
Parting: The parting is the operation of cutting a sheet metal in two parts. Unlike cutting off operation, some quality of scrap is removed to severe the workpiece in two parts.
Cutting off: The cutting off is the operation of severing a piece from a sheet of metal or a bar with a cut along a single line.
Notching: The notching is the operation of removal of the desired shape from the edge of a plate. The punch and the die set up are similar to the piercing or punching operation.
Slitting: The slitting is the operation of cutting a sheet metal in a straight line along the length.
Lancing: The lancing is the operation of cutting a sheet metal through part of its length and then bending the cut portion.

2. Bending operation:

The bending operation is illustrated in Fig. While bending, the metal is stressed in both tension and compression at the two sides of the neutral axis beyond the elastic limit but below the ultimate strength of the material.

Angle bending: The angle bending is the operation of bending a sheet metal to the sharp angle. The punch and the die are shaped to the desired angle. The punch and the die are shaped to the desired angle, taking into consideration the effect of spring back. The angle bending operation is illustrated in Fig.
Curling: The curling is the operation of forming the edges of a component into a roll or a curl by bending the sheet metal in order to strengthen the edges and to provide smoothness to its surface. The curling operation is illustrated in Fig.

Forming: The forming is the operation of bending a sheet of metal along a curved axis. The metal is confined between the punch and the die and is stressed in compression and tension beyond the elastic limit. The shape of the component is governed by the shape of the punch and the die.
Plunging: The plunging is the operation of bending a sheet metal to the desired shape for accommodating a screw or a rod through the plunged hole. The plate is first pierced at the required position and then the plunging punch is pressed in the hole.

3. Drawing operation:

The drawing is the operation of production of cup shaped parts from flat sheet metal blanks by bending and plastic flow of the metal. The operation is also known as cupping. The drawing operation is illustrated in Fig.

4. Squeezing operation:

The squeezing operation is the most severe of all cold press operation. Tremendous amount of pressure is required to squeeze a metal which is made to flow in a cold state within the cavity of the die and the punch to attain the desired shape. For this reason the squeezing operation is performed in a hydraulic press. The different squeezing operations are described below:

Coining: The coining is the operation of production of coins, medals or other ornamental parts by squeezing operation.
Embossing: The embossing is the operation of giving impressions of figures, letters or designs on sheet metal parts. The punch, or the die, or both of them may have the engravings which are marked on the sheet metal by squeezing and plastic flow of the metal.
Flattening or planishing: The flattening or planishing is the operation of straightening a sheet metal which is a curved one. The operation is illustrated in Fig. The pin pointed planishing tool is made to descend on the sheet metal to be straightened, and the projections on the tool exert tremendous pressure on the plate to remove all the residual bending stress present in the plate.