Shearing Operations | Process Done in a Pressing Machine
Punching is a piercing operation. It is the operation of producing a circular hole in a sheet metal using a punch and die.
The material pushed out through the die is the scrap. The punch size will be exactly the same as the size of the hole to be pierced. The die opening is made slightly larger to get the clearance. The sheet metal is introduced between the punch and die through the stripper. The punch pierces the hole in the metal when it moves down. The pierced out metal drops down through the die opening. After piercing, the punch moves up. The sheet metal on the die may stick with the punch surface. The stripper strips off the sheet metal from the punch.
Blanking is the operation of cutting off a flat sheet of required shape. The metal blanked out through the die is the required product. The sheet metal left on the die is the scrap. The blank is further processed-bending or drawing is done on the blank. The size of the blank depends on the size of the die. So the size of the die opening is equal to the blank size. Clearance is given to the punch.
Cutting off is the operation of cutting piece from a sheet metal. The cut is made along a straight line or a curve. The lower blade is fixed to the machine frame. The upper blade is connected to the ram. It slides vertically. The workpiece is placed between the two blades. When the upper blade moves down, it cuts off the sheet metal. A slight clearance is given between the cutting edges of the blades. The clearance depends upon the thickness of the workpiece. In cutting off, there is no scrap.
Parting is the operation of cutting the sheet metal into two pieces. There are two lower blades fixed to the machine frame. A gap is provided between the cutting edges of the lower blades. This gap depends upon the thickness of sheet metal. The gap can be adjusted. The upper blade is connected to the ram. The workpiece is placed between the upper and lower blades. The upper blade moves down cuts the sheet metal. Some scarp is removed in this operation.
It is the operation of cutting small notches at the edge of the sheet metal. A notching die and punch are used.
It is the operation of cutting a sheet metal in straight line. The cut takes place along the length of the sheet metal.
Lancing is the operation of cutting a sheet metal through a small length and then bending the cut portion.
During drawing operations, the blank is held over the die by a holder. Impressions are formed on the area gripped by the pressure pad or holder. Impressions are formed on the area gripped by the pressure pad or holder. This unwanted metal surface should be cut off. Cutting off of the excess metal edge is called trimming. Dies and punches similar to blanking dies are used for trimming operation.
The edges of components produced in sheet metal operations may not be smooth. They may have burrs and irregularities. These edges are finished by a shearing operation. This operation is called shaving. The component to be finished is located over a die. A shearing punch is used to shear off the burrs.