Causes of “collision” in the process of CNC machine tool processing

cnc machined part

cnc machined part


With the continuous development and improvement of the equipment cnc manufacturing industry, the market demand for high-speed, high-efficiency, and high-precision CNC machine tools continues to increase. However, in cnc machining parts, due to various reasons, there are still many problems in the processing process, so that the processing dimensions are inaccurate, and even problems that seriously affect product quality such as crashes occur, causing unnecessary economic losses.

I 、 Setting of machine coordinate origin

The machine coordinate origin is the datum reference point for the machining movement of the machine tool. The correct origin of the machine tool is the prerequisite for reliable machining of the machine tool. The drive shaft of the CNC machine tool is equipped with an AC servo motor, which has two types: relative position encoder and absolute position encoder. The following explains the importance and precautions of the machine reference point to the machining process under these two configurations.


  1. Relative position encoder. When the AC servo motor of the cnc machining services is a relative position encoder, the deceleration block, the travel switch and the one-turn signal of the servo motor are generally used to complete the machine's return to origin operation. It should be noted that after confirming that the overtravel limit switch is valid, Only then can the machine tool return to the origin operation. Before the machining operation, if the machine tool does not return to the machine origin or the position of the machine origin is incorrect, the machine coordinate will be offset. When the program is running, it is easy to cause inaccurate machining dimensions or cause a collision.

  2. Absolute position encoder. When the servo motor system with absolute encoder is powered off, the servo motor or servo drive is equipped with a battery to keep the machine position in memory. Therefore, after the machine is powered off and on, there is no need to return to the machine origin operation, which is more convenient to use. But it should be noted that when the battery power of the absolute encoder is low, the battery should be replaced correctly in time to avoid the loss of the machine position. For example, FANUC β series servo motors, battery replacement needs to be performed when the machine tool is powered on, otherwise the machine coordinates will be lost. After the coordinate position is lost, the corresponding relationship between the mechanical position and the absolute encoder must be re-established. After re-establishing the coordinates, when using the machine tool, you must check whether the programmed coordinates and various compensation data of the called program are correct. Generally, when the machine tool leaves the factory, the machine tool manufacturer has established the reference point position.

 II 、Misoperation during processing

 During the normal processing of the program, the program is stopped due to misoperation. If the operator presses "RESET" to reset, the cycle starts immediately, and it is easy to crash at this time. Because the default value of the operation and the program's'set value have changed, press "RESET" to reset, the CNC system will be reset to the initial state, the pre-reading program information stored in the DRAM will be cleared, and the tool movement command may also be changed.

Avoidance method: If the program stops running due to misoperation during the automatic running of the program, change the mode to edit mode at this time, press "RESET" to reset the program, and then run the program again. Even if you switch from MDI (manual data input mode) to MEM (memory memory mode), you must check each modal code (G, M, S, F, T) and confirm that it is correct before starting the automatic loop (ST) , Otherwise it may cause serious consequences.


 During the cnc metal machining , a servo alarm is caused by a malfunction or other reasons. At this time, the cause must be found out, the fault must be eliminated, and the machine origin must be re-executed, and the tool compensation must be checked for changes. For example, because the positioning speed of the X axis of the machine tool exceeds the maximum speed of the motor or the axis load is too large, the X axis servo drive alarms. After the alarm is released only by the reset button, the original processing program continues to run, and the X axis position will deviate.

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