Maintenance method of electrical circuit of machine tool

In the maintenance of machine tools, the frequency of electrical failure of machine tools is relatively high. In summer, it is high temperature and rainy in the south, and the air humidity is high. Unused machine tools must be powered on frequently to drive away the moisture in the electrical box. The electrical box with water, found, can not be energized , in order to prevent a larger short-circuit fault. Wipe the water in the electric box, and use a hair dryer to blow on the electric circuit board. Contactors, relays and the like can be blown for a longer time, and when they encounter printed circuit boards , plc, and the like, the hair dryer should not stay on it for too long to prevent damage to the circuit board inside. The machine tool cannot be powered on for a test run until the moisture inside is dried.

Electrical failure , generally short-circuit, with the most leakage. When repairing, you should bring tools such as electric pens and multimeters. The electric pens are mainly used to test whether there is leakage to the ground in the machine tool. It is impossible to detect low voltages below 36V. The one I went to work last year The factory has a Shanghai-made M1430 cylindrical grinder, and the ground leakage between the bed and the ground numbs hands. I can’t detect the leakage with an electric pen. I did not feel any numbness in my hands. I followed his method, put one hand on the machine tool and the other on the work stand, and there was no numbness in my hands. At the same time, Master Wang from the workshop also touched it, and I did not feel numbness. Hands, but the worker (sycophant) who operates this machine tool said that there is electricity, and his hands are numb. So I measured the body resistance of the sycophant with a 10K multimeter, and it was only 5K. I also measured the body resistance of Mr. Wang and myself. Above 50K, it’s no wonder that flatterers say they’re grinding their hands. I measured the AC voltage between the machine tool and the station frame with a multimeter, and it was 9V, which indicated that the machine tool line was leaking. The coolant used for the machine tool is saponified oil plus water. The button board of the machine tool It is very dirty. Remove the button board and see that there is a lot of saponified oil on the reverse side. The wire connectors on the button are dirty. Wipe them clean one by one. After installing them, measure the voltage between the machine tool and the station frame to zero.

The control transformer or lighting transformer of the machine tool is burnt out. Be sure to check whether there is a short circuit in the peripheral circuit. It cannot be replaced. The most common is the short circuit of the lighting lamp head. The Bakelite lamp head on the market is not durable, and it takes at most one month to replace it in summer. It is about to be replaced, and the money on the lamp head is easy to age. The lighting circuit on the lathe is the fastest to break down. The iron filings come out and tear the insulation layer of the lighting line, and the transformer is short-circuited and burned. I repaired the CNC last week. The failure of the lathe is that the lighting transformer is burned. The reason is that the lubricating pump motor on the machine bed is burned, but the motor is so small that most electricians don’t know what it is. An old electrician repaired it before and replaced the transformer. And checked that the 24V lighting circuit is good, I don’t know the way, and there is no leakage. He didn’t fold it, thinking it was a short circuit of the 110V control voltage, so the 110V wire didn’t dare to connect it. Just plug it in. I took a multimeter to When I opened the door of the electrical box of the machine tool, I could still smell a smell of glue. I tested the DC resistance with a multimeter, but I couldn’t find any obvious short circuit. I had to ask the lathe worker to stand by the air switch and let him send power for a short time. The time is within 10 seconds, I see that the 24V lighting bulb is flickering, a serious short circuit,Quickly cut off the power and touch the coil of the newly replaced transformer, which is already very hot. For such a fault, you can’t use a multimeter to measure the voltage after power on for a long time, otherwise the newly replaced transformer will be burned again. This can only be solved according to your own experience. I looked for it, because this CNC lathe is not produced by a manufacturer of the next standard, and there is no circuit diagram at all. I looked for it one by one. The lighting transformer of this machine tool has a primary input of 380V and a secondary output of 220V, 110V, 24V, 220V. One way goes to the regular lubricating pump of the bed, the other way goes to the power supply end of the switching power supply of the CNC system, which is further processed by the switching power supply, and outputs DC +5V, +24V for the CNC system. The other way goes to the cooling fan of the machine tool electric box, and 110V goes to control the machine tool. AC contactor coil. I disconnected the 220V fuse of the machine tool, and the brightness of the Zhaoming bulb was normal, and it stopped flashing. First, it was powered on for a short time, and then a little longer. After three times, it was confirmed that there was no short circuit. Then check the 220 line, and the system switching power supply is OK, when the system is powered on, the LCD screen will light up and display system information. Pull out all the wires in the wiring slot of the electrical box and look for them one by one. Find the red wire with wire number U2 and another red wire, and connect them with the machine tool. The cooling pump is worn in a hose at the same time, all the way to the lubricating pump on the bed. Remove the connector of the lubricating sleeve motor, reconnect the 220 fuse, and the transformer will only be slightly warm for ten minutes after power on. The lubricating pump motor is short-circuited. Replace the lubricating pump assembly , the machine tool returned to normal. It was just such a small problem. The old electrician searched for it for two days…

The electrical or motor of the machine tool leaked electricity. It is easy to get an electric shock. When the machine tool smells the smell of paint when it is working, one is that the enameled wire of the motor is not good, the motor is weak, and it will burn out and smoke in a few days. The second is that the coil of the electromagnet is burned. The third is that the coil of the AC connector is burned due to the stuck position. In some serious cases, even the wires next to it are burned. This is very easy to find.

Press each contactor or the middle by hand For the relay, check whether the contacts and yan iron are flexible. It is not flexible when pressed by hand. If the elasticity is not good, it must be replaced, especially the contactor relay, which is not flexible. Generally, the contacts inside are not Well, the contact is burned, and the contact is bad.

The failure rate of the circuit controlled by PLC is relatively low, and the repair is relatively fast. Generally, the peripheral travel switch is broken, the contactor is broken, and the machine tool moves too fast. The output contacts of the PLC are easy to burn or stick and cannot be disconnected. I have encountered this several times. Generally, the PLC with the output contact is a small relay type is prone to this fault. Check that the peripheral circuit is normal, it is the PLC problem. This is not often encountered. I worked in my original factory in the summer of the previous year, and I encountered that the contacts in the PLC were stuck and could not be disconnected. It was a gear shaving machine. Once the machine was powered on, the hydraulic pressure was not turned on. The reversing electromagnet is energized. I have to cut off the power. After waiting for an hour, flick the PLC twice with my hand to pop the contacts inside. After it is done, it took nearly a year. Only the one contact is completely ineffective.

When repairing a machine tool, I must ask the worker who operates the machine tool. He works on this bed every day. If the machine tool has a little problem, they are very clear about it. I repair gear processing machine tools, and I can operate general machine tools , products that can do that process, such as rolling, inserting, shaving, plowing, etc. I don’t know how to operate, so how do I know which action of this bed is abnormal…