I am curious if anyone has thought of using BLDC motors/controllers from the RC airplane hobby world for CNC spindle motors. There are some very healthy motors (up to 8.4kW!) in the 12V to 60V range with matching speed controllers (granted not exactly set up for Mach3 control). The more powerful motors (2kW to 8.4kW) are in roughly 3" diameter housings, and can easily be re-wound to increase RPM or Torque. The stock RPM Range is from 8k to 20k. The concept is pretty simple, the electronics a bit more complex, but the potential for driving a spindle seems pretty good. The RC airplane market is considerably larger than the CNC spindle market, and so mass production prices have less engineering baggage than narrow market products. The 8.4kW motor mentioned (6.4kW continuous) has a price tag of ~$270 w/o controller. Here is a link to one particular motor TowerHobbies.com | GPMG4805 Great Planes Rimfire 65cc Electric Motor it turns ~8.8k RPM @ ~ 55V. Obviously these motors would not be ideal for direct drive of a spindle, but with a belt they could cover the RPM range from 800 to 40k RPM with as few as two "step pulleys" (1:5 5:1). If used to drive a quality spindle the potential appears to be very good at a reasonable price. It is a bit hard for me to grasp "switching" 120A (I consider 120A to be in the "welding" range), but it appears there are existing controllers designed specifically for the task. It seems probable that for extended run times, water cooling might become important, but with the savings over CNC specific designs, this is not an insurmountable expense.

Anyway, I was just wondering if anyone else had looked at these motors wrt building a spindle.

Fish