Stumbled on a stat about stepper motor torque curves that changed how I rough parts

Was reading through a NEMA application note last week and found out stepper motors lose like 20-30% of their rated torque above 500 RPM depending on the driver. Totally explained why I kept getting chatter on a roughing pass at higher feed rates. Anyone else run into this with their setups?

2 comments

2 Comments

dylan60423d ago

Honestly I had the exact same facepalm moment a few years back when I was trying to rough some aluminum parts on my little hobby CNC. Thought I could just crank the feed rate and let it rip but nope, the motor would just start stuttering and skipping steps like it was hungover. I spent like two weeks chasing ghosts in my settings, adjusting acceleration curves and tightening belts, before I finally stumbled across an old forum post explaining the torque dropoff. Now I always keep my roughing feeds under that RPM threshold and it's night and day difference. Still feels dumb that I didn't think to RTFM sooner though.

terry_thomas23d ago

Respectfully, I gotta push back on the "should have RTFM" thing. I mean yeah the torque curve is real and you can't ignore it, but that manual probably didn't tell you the sweet spot either. Most hobby CNC manuals are total garbage, they just give you some generic feeds and speeds that work for wood and call it a day. The real learning comes from banging your head against the wall and finding those forum posts from random guys who actually tested this stuff. You said it yourself, you had to stumble on the info. That's not a RTFM problem, that's a "nobody wrote a good manual for this" problem. Besides, half the fun of this hobby is figuring out why your machine is being a jerk and then fixing it.