To make the sleeve of the punch wheel, the small factory burns the outer ring red, allows the ring to expand thermally, and then installs it on the shaft. On the other hand, large factories freeze that shaft, let it shrink, and then put a ring on the frozen shaft at room temperature. There was nothing but a sledgehammer.

Large factories usually soak in liquid nitrogen, or freeze in industrial freezer, and then assemble the shaft after a little freezing. After returning to normal temperature, it is an interference fit.

A punch is a punch. In national production, stamping technology has been more and more widely used because of its advantages of saving materials and energy, high efficiency, low technical requirements for operators and products that cannot be machined through various molds.

Stamping production is mainly aimed at sheet metal. Blanking, punching, forming, stretching, trimming, fine punching, shaping, riveting and extruding parts can be made through the die, which is widely used in various fields. For example, we use switch sockets, cups, cabinets, plates, computer cases, and even missile planes ... there are many accessories that can be produced by punching machines through molds.

The design principle of punching machine is to convert circular motion into linear motion, and the flywheel is driven by the main motor, and the gear, crankshaft (or eccentric gear) and connecting rod are driven by the clutch to realize the linear motion of the slider. The motion from the main motor to the connecting rod is circular.

For circular motion and linear motion, there must be a connection point between the connecting rod and the slider. There are two kinds of mechanisms in its design, one is ball type, and the other is pin type (cylindrical type). Through these two mechanisms, the circular motion is transformed into the linear motion of the slider.

The punch presses the material to plastically deform it, thus obtaining the required shape and accuracy. Therefore, it is necessary to cooperate with a set of molds (divided into an upper mold and a lower mold) to put the material between them, and the machine exerts pressure to deform it. The reaction force caused by the force applied to the material during machining is absorbed by the main body of the punching machine.