PM935 Max Spindle Speed

[kb58]

I was checking features on the PM site for their PM935 and saw this:

This requires operating the motor on nearly 120Hz. It's a bit surprising though since someone (maybe even Matt) said that PM doesn't recommend operating the motor above its normal speed. I guess if I were them, I'd say the same thing, but having it listed under the unit's Description implies that it can be run that way. Has anyone actually done so? It would be nice to know in case there's a need to mill hardwoods.

 

[wrmiller]

I have the stock 3-phase motor and don't typically run it above about 80-90Hz when needed. I usually run lower than that.

Except that one time I had to mill a slot with a .075" end mill. I think I was at or just over 100Hz that time.

 

[ddickey]

I believe the general rule is 2 pole motors are safe to run at 75 Hz and 4 pole at 120 Hz. If there is a restriction it might be mechanical more than anything,

 

[Bob Korves]

It is not just the motor. The mill was designed to be safe and have a long life at a maximum design speed. There may be problems with spindle bearings, speed control parts, and other components that were never engineered or tested to higher speeds than specified in the design and prototype stages. Obviously, the machine can run somewhat faster than in ex factory trim, but the bottom line is that you are the test pilot...

 

[kb58]

True, but if your "flight manual" says that it's good to 5000 rpm...

 

[Bob Korves]

True, but if your "flight manual" says that it's good to 5000 rpm...

What could possibly go wrong???