
B–63523EN–1/03
1. AXIS CONTROL
253
Servo delay compensation during a chopping operation can gradually
increase the chopping speed. If the chopping speed is about to exceed the
maximum allowable chopping feedrate, it is clamped to the maximum
allowable chopping feedrate. In this case, the chopping axis may go
beyond the bottom dead point. In servo delay compensation, the distance
specified in a movement command is increased by a compensation
amount that matches the distance yet to go before the top and bottom dead
points are reached, and the chopping speed is also increased, so that the
distance yet to go can be compensated for.
If the chopping speed is clamped to the maximum allowable chopping
feedrate, a distance specified in the movement command is increased, but
the clamped speed remains unchanged. For this reason, the chopping axis
can go beyond the bottom dead point.
To solve this problem, use the CMX parameter (bit 0 of No. 8361) in order
to stop clamping the chopping speed at the maximum allowable feedrate
when the distance yet to go becomes smaller than a value specified in
parameter No. 8378 (distance yet to go before the bottom dead point is
reached), thereby allowing the speed to increase again, so that the bottom
dead point will not be passed through.
In this case, servo delay compensation is carried out as follows:
1 Until the chopping speed reaches the maximum allowable chopping
feedrate:
→ Compensation is carried out by increasing the speed and a distance
specified in the movement command.
2 Until the chopping speed becomes lower than a value specified in
parameter No. 8378 (distance yet to go) after it reaches the maximum
allowable chopping feedrate:
→ Compensation is carried out by increasing only a distance specified
in the movement command.
3 After the chopping speed reaches the maximum allowable chopping
feedrate and becomes lower than a value specified in parameter No.
8378 (distance yet to go):
→ Compensation is carried out by increasing the speed and a distance
specified in the movement command.
In this case, however, the final chopping speed can exceed the maximum
allowable chopping feedrate because it is not clamped at the maximum
allowable chopping feedrate.
[Parameter setting method]
D Parameter No. 8375 (maximum allowable chopping feedrate)
Set the parameter with a value smaller than the actual maximum
allowable feedrate just in case the final chopping speed may exceed the
maximum allowable feedrate.
D Parameter No. 8378
Set the parameter, using a value obtained with the following
expression as a guideline.
If the bottom dead point can be passed through even when the value
obtained with the following expression is set in the parameter, increase
the value little by little until the dead point is no longer passed through.
D If servo delay
compensation can cause
the chopping speed to
exceed the maximum
allowable chopping
feedrate: