Punching (Topic: 16210)

In punching, or stamping, the workpiece is cut by deformation (shearing), i.e. no swarf is produced. Punching is a very quick and efficient method of producing even complicated apertures and fashions. With proper design of the extruded shape, punching might replace more complicated and expensive operations such as milling or drilling.

In normal stamping the distance between die and punch should be 5ñ10% of the material thickness. The punch to die clearance is also dependent on the material hardness and the punching speed. The punching force can be essentially reduced if the die face is inclined. The inclination should not be larger than the material thickness.

Fine blanking is used when a precise and clean cut finish is required. The distance between punch and die is normally 0,3ñ0,5% of the material thickness, and the edge of the punch or die should be very sharp. The workpiece is firmly clamped against the die. Aluminium alloys in the soft condition are preferable, due to their larger ductility. Fine blanking operations are suited to large production runs, since the tooling costs are higher than conventional tooling.

Conventional punching (left) and fine blanking (right).

Punching of aluminium alloys may cause problems with build-up on punches and dies. Proper surface coating of the tools and suitable cutting fluids reduce those problems.

References: [2]