Ramping Spindle Speed?

[EricSchimel]

I just setup and installed a spindle speed controller on my ShopBot. It works great. It's nice to drop the speed down for drilling and then ramp it up for long cuts.

Has anyone ever figured out how to link spindle speed to cutting speed?

For example, if I have a long straight cut at 5 IPS, that's 100% speed. For easy math let's say I'm cutting at 10k RPM. When I get into a corner my ramp values may drop that cutting speed 50%. Can I setup my ShopBot to drop my spindle speed 50% when in a corner like that?

Basically, I want to link my spindle speed to my cutting speed....

[EricSchimel]

Bumping it up!

[bleeth]

No. Would be nice though.

[bill.young]

There's not a way that I know of, but if you knew the ramping values you could probably write a post-postprocessor that modified the original file with added speed changes.

That said, I'm not convinced that it would be a good idea. I'd worry that with the bit in the material and cutting, that the tool would be back at full move speed before the rpm's caught up. I can imagine either broken bits or little wiggles from bit deflection at each one of those points. I've got no science to back this up, but know how long it takes for a spindle to come up to speed when it's just spinning in air.

[EricSchimel]

That's a good point, I didn't think about spindle acceleration...

Maybe it could work if he speed reductions weren't so drastic... So lets say your tool slows down to 50% speed in a corner, maybe the spindle only drops a little...

I wonder if any post processors do this. I'm so used to VCarve and Aspire I haven't really looked into anything else...

[coryatjohn]

You could easily edit the file to add those speed changes and test it out. As for acceleration, mine changes speed very quickly, even with a large and heavy bit. Perhaps 1/10th to 1/5th of a second per 1,000 RPM's. Perhaps longer on deacceleration though.