1、 Causes of abnormal machining accuracy faults

The causes of abnormal machining accuracy faults are highly hidden and difficult to diagnose. Five main reasons can be summarized: the feed unit of the machine tool has been modified or changed; Abnormal zero offset of each axis of the machine tool; Abnormal axial reverse clearance; Abnormal motor operation status, i.e. abnormal electrical and control parts; Mechanical failures, such as screws, bearings, couplings, and other components. In addition, the programming of machining programs, the selection of cutting tools, and human factors may also lead to abnormal machining accuracy.

2、 Principles for Fault Diagnosis of CNC Machine Tools

1. The external and internal CNC machine tool is a mechanical, hydraulic, and electrical integrated machine tool, so the occurrence of its faults will also be reflected comprehensively by these three factors. Maintenance personnel should first conduct inspections one by one from the outside to the inside, and try to avoid randomly opening and disassembling, otherwise it will expand the fault, cause the machine tool to lose accuracy, and reduce performance.

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

3. Before moving, the machine tool can be powered on only after it is confirmed to be a non-destructive fault through understanding, observation, testing, and analysis in the static state of the machine tool when it is powered off; Conduct dynamic observation, inspection, and testing under operating conditions to identify faults. For destructive faults, the danger must be eliminated before power can be applied.

4. When multiple faults are intertwined and covered up, and there is no way to start at the moment, easy problems should be solved first, and then difficult problems should be solved. Often, after solving simple problems, difficult problems may also become easier.

3、 Fault Diagnosis Method for CNC Machine Tools

1. Intuitive method: (observing, listening, inquiring, and cutting) Ask about the fault phenomenon and processing status of the machine tool; Check the CRT alarm information, alarm indicator light, deformation of components such as capacitors, smoke burning, and tripping of protectors; Abnormal sound; Smell - Electrical components smell burnt and other odors; Touch heating, vibration, poor contact, etc.

2. Parameter inspection method: Parameters are usually stored in RAM. Sometimes, insufficient battery voltage, long-term power failure of the system, or external interference can cause parameter loss or confusion. Relevant parameters should be checked and calibrated based on fault characteristics.

3. Isolation method: For some faults that are difficult to distinguish between CNC parts, servo systems, or mechanical parts, isolation method is often used.

4. Using the same type of swapping method, replace the suspected faulty template with a backup board with the same function, or exchange templates or units with each other with the same function.

5. Functional program testing method: Write some small programs for all instructions of G, M, S, T, and other functions. When diagnosing faults, run these programs to determine the lack of functionality.