In CNC machine tools, most of the faults are available for investigation, but there are also some faults. The alarm information provided is vague or even no alarm at all, or the period of occurrence is long, irregular, and irregular, which brings to the search and analysis Many difficulties. For such machine tool failures, it is necessary to analyze the specific conditions and perform patient search. In addition, comprehensive knowledge of machinery, electricity, hydraulics, etc. is particularly required during the inspection, otherwise it is difficult to quickly and correctly find the real cause of the failure.
Abnormal machining accuracy failures: system parameters change or change, mechanical failures, machine tool electrical parameters are not optimized, abnormal motor operation, abnormal machine tool position loops or incorrect control logic are common causes of abnormal machining accuracy failures of CNC machine tools in production. Find out the relevant If the fault point is dealt with, the machine tool can be restored to normal. In production, we often encounter faults with abnormal machining accuracy of CNC machine tools. Such faults are highly concealed and difficult to diagnose.
There are five main reasons for this type of failure:
1. The feed unit of the machine tool is changed or changed;
2. The zero offset (NULLOFFSET) of each axis of the machine tool is abnormal;
3. The axial backlash (BACKLASH) is abnormal;
4. The motor running status is abnormal, that is, the electrical and control parts are faulty;
5. Mechanical failure, such as screw rod, bearing, shaft coupling and other parts.
In addition, the preparation of the processing program, the selection of tools and human factors may also cause abnormal processing accuracy.
If the machining accuracy is abnormal due to mechanical failure, the following aspects should be checked one by one.
1. Check the machining program segment that is running when the accuracy of the machine tool is abnormal, especially the tool length compensation, the proofreading and calculation of the machining coordinate system (G54～G59).
2. In the jog mode, move the Z axis repeatedly, and diagnose the motion state by sight, touch, and listen. It is found that the sound of Z-direction movement is abnormal, especially when the jog is fast, the noise is more obvious. Judging from this, there may be hidden dangers in machinery [1].
