Why did the accuracy of CNC Lathe suddenly decrease?

First, causes of abnormal machining accuracy faults

Five main reasons:

1. The feed unit of the machine tool is changed or changed;

2. The zero offset of each axis of the machine tool is abnormal;

3. The axial backlash is abnormal;

4. The motor running state is abnormal, that is, the electrical and control parts are abnormal ;

5. Mechanical failure, such as screw, bearing, shaft coupling and other components.

In addition, the preparation of machining programs, the selection of cutting tools and human factors may also lead to abnormal machining accuracy.

Second, the principle of fault diagnosis of CNC Lathe

1. First external and then internal CNC machine tools are machine tools that integrate machinery, hydraulic pressure and electricity, so the occurrence of failures will also be comprehensively reflected by these three. Maintenance personnel should check one by one from the outside to the inside, and try to avoid random unpacking and disassembly, otherwise it will expand the fault, cause the machine tool to lose precision and reduce performance.

2. Mechanical first, then electrical Generally speaking, mechanical faults are easier to detect, while the diagnosis of CNC system faults is more difficult. Before troubleshooting, first pay attention to eliminating mechanical failures, which can often achieve twice the result with half the effort.

3. Static first and then moving. First, in the static state of the machine tool power off, through understanding, observation, testing, analysis, and confirming that it is a non-destructive fault, the machine tool can be powered on; Inspection and testing to find faults. For destructive faults, the danger must be eliminated before powering on.

4. Simple first and then complex When multiple faults are intertwined and covered up, and it is impossible to start for a while, the easy problems should be solved first, and the more difficult problems should be solved later. Often after the simple problems are solved, the difficult problems may also become easy.

Three, CNC machine tool fault diagnosis method

1. Intuitive method: ask - the fault phenomenon of the machine tool, processing status, etc.; look - CRT alarm information, alarm indicator light, capacitor and other components are deformed, smoked and burnt, and the protector trips, etc.; listen - abnormal sound; smell - electrical components Burnt smell and other peculiar smells; touch-heat, vibration, poor contact, etc.

2. Parameter inspection method: The parameters are usually stored in RAM. Sometimes the battery voltage is insufficient, the system is not powered on for a long time or external interference will cause the parameters to be lost or confused. The relevant parameters should be checked and corrected according to the fault characteristics.

3. Isolation method: For some faults, it is difficult to distinguish whether it is caused by the CNC part, the servo system or the mechanical part, and the isolation method is often used.

4. The same-kind swapping method replaces the suspected faulty template with a spare board with the same function, or exchanges the templates or units with the same function.

5. Functional program test method Write some small programs for all the instructions of G, M, S, T, functions, and run these programs when diagnosing faults to judge the lack of functions.