I just uploaded a new video to the G-Wizard Calculator University pages that explains Spindle Power Curves:
Spindle Power Curves let you compensate for changes in your CNC machine’s spindle output at various rpms and they can also downrate the power on small machines to compensate for their lack of rigidity.
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Great feature! I set this up some time ago but didn’t really know the power curve of my spindle motor. I replaced the stock spindle motor (very anemic 3HP BLDC) with a much more capable and powerful 2HP Vector drive motor with VFD and encoder feedback. I couldn’t find any data about the power curve. Is there any resource that is good for figuring this out?
James, typically there will be some power curve information in the VFD manual. Check there first.
Thanks Bob. Unfortunately the manual doesn’t have that info. It simply says something like when in sensorless vector mode you will have constant torque up to base speed (1800rpm base) and constant horsepower up to twice base speed. I’m using encoder feedback so My guess is that it would slightly better.
The way I entered into Gwizard was:
0 rpm = 0 hp
1800 rpm = 2hp
3600 rpm = 2hp
5000 rpm = 2hp
Don’t know if that is right or even close but I have only really experience spindle bogging a the low RPM range (like below 1000, and primarily below 500rpm)
Hi Bob, Is there any way to determine curves from old machines? Manufacturer of my CNC (Leadwell) just write 7.5 HP as max power (10 Hp, for 30 minutes). Also I have slow-and fast belt gearing (30-1000 RPM low, 1001-4000 RPM High). Power curves can help me to achieve better removal rates if I can do this estimation. :´(
Alex, it’s not very easy unless you have a dynamometer for the spindle.