Re: spindle counterweights

> Hello,
>
> I have a CNC machine that I have retrofitted to a more modern
> control.
> It is a bed mill with a 42"x20" bed and a 5 HP spindle motor.
> It was previously only capable of 2 axis simultaneous motion. It
> had a dec pdp control. We have are now running a windows
> based control with a galil servo card.
>
> Anyway, there is a counterbalance on the spindle that consists of
> a chain that goes up and over the top of the machine (via some
> pulleys) to some weights that hang on the back of the machine.
> We experience some problems when there are rapid
> accelerations away from the bed and it also tends to overshoot
> when moving toward the bed. It will sometimes gouge when it is
> move down and has to stop rapidly.
>
> I have been planning on writing some software to preprocess
> the G-Code and look for rapid accelerations in the Z and add
> acceleration and deceleration for those lines but I was
> wondering how other machines tend to handle the
> counterbalance issue since I think some of our problems are
> due to that. You can hear the counterbalance bouncing around a
> little under rapid acceleration.
>
> Does anybody have any ideas?
>
> Thanks,
> -Jeremy