Mike, the brushless motors I'm looking at have metal cases. That should help with the heat dissipation I hope. As for driving them, the controllers expect a .5ms to 1.5ms width signal to vary their speed. 10 years ago, I happened to have built servo driver using a 555 timer to generate the pulsewidths. It drove a servo just fine, and should drive the hobby-type brushless ESCs. What would be really cool is to get MACH3 to output a variable voltage that I could use to drive the ESC. A simple PIC (even a puny 16F84) could handle the voltage-to-PWM conversion for me. I'll look into it and report back when I have some results.
Originally Posted by in2steam  Look into proxon, they have a brushless dc dremel like tool that many have used with succes. I don't think you will get the desired torque out of a can motor and the bearings won't handle the load.
chris |
Chris, thanks for the tip. I looked into the Proxon, first, and realized it was overkill for my needs. I'll be using the high-speed Wolfgang spindle to cut very small cavities in aluminum. No cavity is over 1/4" deep or over 1.5" in length. With an ultra-small stepover and stepdown of .00625", it should be hardly any stress on the cutter. I don't think a 1/32"
cutter could handle much stress any way. I've heard those little babies snap off and go flying across the room at the slightest abuse. I'll definitely have an enclosure around my mill when it is whirring away at 40K RPM with a tiny cutter in the collet!
As for load on the bearings, the motor drives the spindle, so I'm not expecting any undo stress on the motor bearings. If the
brushless motor shaft were the spindle, then I'd be in real trouble, wouldn't I!
Regarding torque, I wonder how I can calculate that? Does anyone know how I might determine the torque on a 1/32" 2-flute end mill running at 40K RPM, cutting .00625" into 6061-T6 aluminum at 10 IPM? I suspect it is negligible at that rate.