A CNC lathe uses the FANUC 0 TB system. The fault phenomenon is: when the tool change command is input, the turret tool change rotates continuously without any alarm.
The rotation command has the following functions:
- ① can judge the turn of the shortest path,
- ② the calculation of the number of steps between the current position and the target position,
- ③ the calculation of the position before the target or the calculation of the number of steps before the target. Through the analysis of the ladder diagram in PMV, we know that the rotation command of the turret is excited by the start signal of the turret to start the operation, and the start signal of the turret is generated by transmitting the F153 tool code to R0567 for comparison. Since the machine tool turret has only8 tool positions, it is necessary to compare whether the tool number is greater than 0 and less than9. After comparison, use the coincidence command to determine whether the current tool number is consistent with the target tool. If they are not consistent, the turret start signal The output makes the rotation command work, and calculates the number of steps of the previous digit and then outputs. If the output is 0, the rotation is forward, and the output is 1 is reversed. After the rotation, the compliance command is executed to determine whether the current tool number is consistent with the target tool number. If they match, the rotation stops and a tool change completion signal is issued. Only then has the entire tool change process been completed.
After conducting the above analysis, start the inspection. Call up the ladder diagram, first check what signal the turret rotation always outputs. It is related to it; then check the working state of the rotation command, normal; then check the working state of the command, and find that there is no output, then you can judge the problem.
Here, continue to check whether the entered tool number is consistent with the tool number given by the encoder, and it is found that one bit of the encoder is not output.
When the tool is changed to this number, the compliant command is not output because the editor is not drawn, that is to say The NC did not find this tool number and caused the turret to rotate all the time. Therefore, it was determined that the problem of the encoder caused the machine tool to malfunction, and a new encoder was used for troubleshooting.