X_SpeedLimitDetect, look ahead for speed limit

This function generates a CNC status signal depending on the motion blocks and the current path feed rate. It is mainly used for plasma cutting technology to deactivate distance control of the cutting head via the PLC if the speed drops below a certain limit. This occurs when decelerating before and accelerating after a corner, for example.

Therefore, the critical positions in the motion segment (corner) are defined by a speed limit.

Speed limit detect

The status flag „speed limit detect“ to the PLC is set if the actual path velocity is below the given limit. The reduce of path velocity results of:

• Reduction of velocity at block transition because of a corner in the contour.
• Reduction of velocity because of override setting.
• Expected M-function acknowledgement at block transition.
• Look-Ahead reduces velocity because of missing path to move (to less blocks).

Zone

In addition, the signal can be set in advance, or the clearing can be delayed. This amount of advance or delay can be given in time or in distance unit.

• Advance: The prepared velocity at block end is e.g. because of a geometrical corner below the given limit. The status flag is set in advance with the given amount (distance / time).
• Backlash: The velocity at block start already is below the limit value. The status flag will be cleared delayed if the velocity crosses the limit.

Clear

I.e. the status flag will be cleared if the following conditions are reached:

• The actual path velocity is above the given limit.
• The path position is outside the given delay (time, distance).