Reasons: 1, insufficient air pressure;        
2, the loose knife button is in poor contact or the line is broken;        
3, loose knife button PLC input address point burned out or no signal source (+24V);      
4, loose knife relay does not operate;        
5, the loose knife solenoid valve is damaged;        
6, the amount of cutting is insufficient;        
7, the tool cylinder oil cup is short of oil;      
8, punching cylinder failure;      

Countermeasures;        
1, check the air pressure until the air pressure reaches 6 kg plus or minus 1 kg;      
2, replace the switch or check the line;        
3, replace the PLC input port on the I/O board or check the PLC input signal source, modify the PLC program;      
4, check whether the PLC output signal is/is not, whether the PLC output outlet is burned out, modify the PLC program;      
5, solenoid valve coil burned out replacement, solenoid valve body leakage, piston does not move, then replace the valve body;        
6, adjust the cutting amount to loosen the knife smoothly;        
7, add the hydraulic oil in the tool cylinder oil cup;        
8, the internal screw of the punching cylinder is loose and leaking, then the screw should be re-tightened, replace the sealing ring in the cylinder, if it cannot be repaired, replace the punching cylinder;