The actual moving distance of the CNC machine tool is inconsistent with the displayed coordinate value

Siemens 810 CNC system, 611 drive module around 1996, 1FT5 motor. The equipment has been used for many years and is very stable. Yesterday, the processed parts were out of tolerance, and the problem was discovered: the horizontal X-axis moved in the same direction, the meter and the coordinate display were inconsistent, the movement was 50-60mm, and the difference between the coordinate value and the meter value was from 0 to 20. More or less, no rules. The feed amount of the handwheel is consistent with the coordinate display amount. There is a gap of 4 wires in the positive direction. Semi-closed loop system, motor with encoder. Ask you how to judge and solve.
Answer: In fact, it is caused by the response lag of the position loop, and the mechanical following error is also out of range.
It is necessary to check all aspects of the mechanical transmission, such as the X-axis motor and Whether the connection of the lead screw of the workbench is reliable, whether the gap is appropriate, and whether the adjustment of the inclined iron of the workbench is appropriate. In addition, if the signal status of the position detection components such as the encoder is abnormal, it will also cause the fault. The specific method is as follows:
1. First judge whether there is a problem with the mechanical transmission, disengage the motor from the lead screw, and turn the lead screw gently by hand. It should feel stable without stagnation or pause under normal conditions, otherwise , it should be determined that the screw bearing is damaged and replaced,
2. If the above is normal, to check the backlash of the X-axis of the machine tool, you need to print out the X-coordinate backlash value with a dial indicator at various positions in the X direction, such as the ends and the middle position, and the results should be consistent. Otherwise, check and adjust The straightness of the X axis,
3. If the backlash value No more than 0.04m, compensate the backlash value to the axis parameter MD32450,
4. If the backlash value is greater than 0.04mm, check the shaft screw bearing and adjust the preload of the ball screw to eliminate the backlash. After the backlash is completed, check whether it is qualified, that is, ensure that it is within the range of no more than 0.04mm If it is qualified, then compensate the backlash and continue the test run,
5. After the above adjustments are normal, if the fault persists, check whether the connection of the X-axis motor encoder is loose. After tightening, test the machine repeatedly to check whether the fault phenomenon of the machine tool has been eliminated?

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