Explanation of limit design scheme of CNC milling machine

Explanation of limit design scheme of CNC milling machine


Source: www.skjgzxcj.com
In order to effectively ensure that the CNC milling machine can always be in a good running state, there will be a soft limit (parameter setting limit), a hard limit (travel switch limit), and 2 protection “lines of defense” on the linear axis.

In the case of CNC milling machines, the limit problem is always a very common fault during operation, and the analysis of related materials is also rare. Therefore, we conducted a series of analysis and explanations for the occurrence of the “limit alarm” problem of the CNC milling machine.
The limit with limit switch is called “hard limit”, and the limit set by the system limit function is called “soft limit”. For these two types of limits, when any problems occur, a “limit alarm” prompt will appear on the display of the CNC milling machine. If the CNC milling machine is in over-planned use, the system will initiate an alarm, and the CNC milling machine should be stopped at this time.
Most milling machines are equipped with an “overtravel release” contact. Once a “hard limit” alarm occurs, after confirming that the hard limit switch is pressed, close the contact and move out of the limit position in the opposite direction in manual mode To clear the alarm. Some CNC milling machines do not set this button. At this time, an equivalent short-circuit method should be adopted at the corresponding point to compulsorily meet the relevant conditions before moving the milling machine out of the limit position.
If in the actual position, the limit position is not exceeded, but the limit alarm sounds. It should be checked whether it is caused by the loss of the stroke parameter or the change of the stroke parameter.
Regarding the parameters, the classic example: when returning to the reference point, the soft limit alarm is prone to appear, and the actual position of the CNC milling machine is still a certain distance from the reference point. At this time, when the hard limit function is intact, increase the value of the soft limit parameter according to the displacement range of the stop point from the reference point mark at the time of the alarm (sometimes it needs to be set to the maximum value or canceled, depending on the situation. ), after the CNC milling machine returns to the reference point to be normal, the soft limit setting needs to be restored.

Author: Chris Na

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