Fault Analysis of QZK Type Programmable Cutter

Our factory has a QZK920 program-controlled paper cutting machine that has experienced such a failure: After the power-on and paper-cut work for about 4 hours, the cutting force of the cutting blade gradually attenuates, and finally the cutting blade is unable to cut. After shutting down for several hours, the system can be restored to normal operation after a few hours of operation, but similar malfunctions have occurred after a few more hours of operation. Check the electrical loss and electrical circuit related to the hydraulic system, there is no exception, but can not find the root cause of the fault. This has been running intermittently for more than a month. In the end, normal cutting can only last for half an hour. There is no way to cut a knife. At this time, the hand angle checks the oil circulating from the hydraulic circuit and has a clear feeling of fatness, indicating that the oil temperature in the operation is high. The fearless pressure on the paper press cylinder and the cutting pressure were measured. The result was that the pressure on the paper press was only 4.5 MPa, which was lower than the normal working pressure of 10.5 MPa by 6 MPa; the cutting pressure was only 2 MPa, which was higher than normal. The required working pressure is 7-8Mpa and low about 6Mpa.

Although the pressure of the paper presser is 6 Mpa lower than the required working pressure, it can still hold down the paper. Therefore, the problem of the paper presser's failure is not obvious. If the cutting pressure of the knife is only 2Mpa, it cannot be cut. Obviously, the machine is not just cutting the pressure failure, the pressure of the platen is not normal. However, in the case of a hydraulic system that operates these two actions, in the case of no abnormality in the operation status of the DC valve electromagnets and the electrical appliances, the main cause of the failure can be judged to be that the main fuel supply is insufficient. According to the judgment, we will check the disassembly of the main oil pump (double vane pump) and find that there are signs of wear on the working surface of the pump cylinder, and the pump body also has a 4 cm long crack. Because of the wear of the pump cylinder working surface, it will inevitably affect the pressure of the pump oil; while the partial crack of the pump body will also leak from the crack of the pump body when the oil oil temperature rises and the viscosity decreases, further reducing the oil pump. Work pressure. This is the reason why the oil temperature rises after the power is turned on for a few hours and the fault starts to be clearly exposed. After we replaced the double vane pump, the fault was also eliminated.