Machine tool positive and negative hard limit alarm

Under normal circumstances, this alarm will not appear, the operation of the machine tool before zero may appear, because the system does not fix the mechanical coordinate system before zero, but it is positioned at will, and the soft limit is invalid, so the operation of the machine tool must first return to zero.  

The reason:

（1）The stroke switch contact is pressed and stuck (over stroke);

（2）The travel switch is damaged;

（3）Open circuit, short circuit and no signal source in the travel switch line;

（4）The limit stop can not press the switch contact to the operating position;

（5）PLC input point is burned out.

Countermeasure:

（1）Manually or manually shake the wheel away from the safe position, or clean the switch contacts;

（2）Replace the travel switch;

（3）Check whether the travel switch circuit is short circuit, short circuit is processed again. Check the signal source;

（4）Adjust the installation position of the travel switch so that it can be normally pressed on the switch contact to the operating position;

（5）Replace the input point on the 1/0 board, set the parameters, and modify the PLC program.