Re: [CAD_CAM_EDM_DRO] spindle counterweights

Hello Jeremy,
The counter balance is important for most machines
and I recommend that you keep it. But you might wrap
the weight with rubber and add a spring between the chain
and the weight in order to limit the acceleration - deceleration hits.
And try to lower the a/deceleration rates.
Hard hits always hurt the ball screws by the time.
On several machines you find pneumatic or hydraulic counter weight
pistons but they can cause even more trouble.

Check the bearings of the pulleys!

Good Luck
Sven Peter
jag@... wrote:

>
> 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
>
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