CNC machine tool processing accuracy caused by abnormal reasons

In cnc machining the master at work often face the machining of precision abnormal of the workpiece, but don't know what went wrong, this not only caused unnecessary loss, also greatly affect the process of the follow-up work, increase the time cost.Faced with such confusion, the following is to analyze the cause of the abnormal machining accuracy.

一、 Causes of abnormal machining accuracy.

     Machining precision abnormal have strong concealment, often very difficult for diagnosis, and very hard to confirm it, usually caused the result of the following five main reasons: abnormal zero offset machine each axis;The machine feeding unit is changed; Abnormal operating condition of the motor, namely electrical and control part abnormal; Anomalous inversion of axial direction; Mechanical faults, such as screw, bearings, shaft coupler and other components.Besides, the selection of cutters, the preparation of processing procedures and human factors may also lead to abnormal machining accuracy.

二、Second, CNC machine tool diagnosis criteria

1.  First exterior, second interior

            CNC machine tool is a integration of mechanical, hydraulic, electrical machine tool, so the problems will be summarized by these three. Repair personnel should first be carried out by the outside one by one investigation, try to prevent the unseal, disassembled, otherwise it will expand the problems, the loss of precision machine, down function.

2. first mechanical, then electrical

              In general, mechanical problems easier to detect, but the diagnosis of CNC system problems are more difficult. before the troubleshooting, we must first check the mechanical problems, so often can achieve a multiplier effect.

3. first static observation, then dynamic checking

            Under the circumstance of suspension of power-off of the machine tool, the machine tool can be energized only after knowing, investigating, testing, analyzing and confirming as a non-destructive fault; under the operating conditions, carrying out dynamic investigation, examination and quizzes to find fault . As for the devastating problems, we must first remove the risk before turning on power to the machine.

4.  first sample, then, complex

              When presenting a variety of faults staggered with each other, sometimes unable to start, should deal with simple problems then more difficult problems of post-processing. After the simple problem is solved, the difficult problem can be solved.

三、CNC machine tools diagnosed method

1.       Intuitive method: (ask, watch, listen, smell and touch) ask - machine problems, processing conditions; watch - CRT alarm information, alarm lights, capacitors and other components deformed smoke charred, protector tripping; Listening - abnormal movement. Smell - smell of electrical components and other smells; touch - oscillation, heating, poor contact and so on.

2.     parameter view method:

parameters are usually stored in RAM, and sometimes the battery voltage is not enough, the system is not powered for a long time or external interference will make the parameter is lost or in disorder, according to the characteristics of the error, view and correct the parameters.

3.      Isolation Law:

Some problems, it is difficult to distinguish if it is the CNC part or the servo system or mechanical parts of the formation, often we choose the isolated method.

4.     Similar exchange method

Use the spare board of same function to replace the suspected faulty template, or function with the same template or unit exchange.

5.    Function program test method

 G, M, S, T, the full function of the preparation of a number of small instructions into a small program. in the diagnosis of these problems when running these procedures, you can determine the lack of function.