From the repair practice, we explored the causes and exclusions of the common faults of the punching machine. The following takes the J_(20)-80t and J_(23)-35t punching machines as an example. The following are introduced: 1. Q: After the slider goes down, the return journey is not smooth. What is the reason for the "bounce" phenomenon? How to eliminate it? Answer: (1) The balancer spring is broken and the expansion force is reduced. Replace the balancer spring (2) The auxiliary key in the clutch is broken and the auxiliary key is replaced.