1、 Causes of abnormal machining accuracy
The causes of abnormal machining accuracy are hidden and difficult to diagnose. Based on years of practical experience, the author sums up five main reasons: the feed unit of the machine tool is changed or changed; the zero point offset of each axis of the machine tool is abnormal; the reverse clearance of the axis is abnormal; the running state of the motor is abnormal, that is, the electrical and control parts are abnormal; the mechanical fault, such as the lead screw, bearing, coupling and other parts. In addition, the programming of machining programs, the selection of cutting tools and human factors may also lead to abnormal machining accuracy. Wechat for metal processing, good content, worthy of attention.
2、 Fault diagnosis principle of CNC machine tools
1. The first external and then internal CNC machine tool is a machine tool integrating mechanical, hydraulic and electrical, so the occurrence of its fault will also be comprehensively reflected by the three. The maintenance personnel shall check one by one from the outside to the inside first, and try to avoid opening and disassembling at will, otherwise the fault will be enlarged, the machine tool will lose precision and performance.
2. Generally speaking, mechanical fault is easy to detect, while the fault diagnosis of CNC system is more difficult. Before troubleshooting, first of all, pay attention to eliminate mechanical faults, which can often achieve twice the result with half the effort.
3. The machine tool can be powered on only when it is confirmed as a non-destructive fault through understanding, observation, test, analysis under the static state of power failure of the machine tool; under the operation condition, it can be dynamically observed, inspected and tested to find the fault.
For destructive faults, the danger must be eliminated before power on.
4. Simple first, then complex. When there are many kinds of faults interwoven and covered up, and there is no way to start for a while, the easy problems shall be solved first, and then the difficult problems shall be solved. Often after simple problems are solved, difficult problems may become easy.
CNC machining
3、 Fault diagnosis method of CNC machine tools
1. Intuitionistic method (looking, hearing, asking and cutting) – machine tool fault phenomenon, processing status, etc.; look at CRT alarm information, alarm indicator light, capacitor and other components deformation, smoke burning, protector tripping, etc.; listen to abnormal sound; listen to electrical components burnt smell and other peculiar smell; touch heat, vibration, poor contact, etc. Wechat for metal processing, good content, worthy of attention.
2. Parameters of parameter inspection method are usually stored in RAM, sometimes the battery voltage is insufficient, the system is not powered for a long time or external interference will cause parameter loss or confusion, so relevant parameters shall be checked and calibrated according to fault characteristics.
3. Some faults of isolation method are difficult to distinguish whether they are caused by numerical control part, servo system or mechanical part. Isolation method is often used.
4. In the same kind of method, the spare board with the same function is used to replace the suspected faulty template, or the templates or units with the same function are exchanged with each other.
5. The function program test method compiles some small programs for all the instructions of G, m, s, t and functions, and runs these programs when diagnosing faults to judge the lack of functions.
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