Spindle Motor Advice

Hi, I just called DMM and asked them about using the DST 1.8kv servo to do the same thing with my PM833 mill and they advised that running the motor continuously at 3000 rpm would put it outside it's peak torque range and reduce the torque by the drive ratio.

I wanted to do the same as what you have done and reach 5000-6000 rpm with potential for rigid tapping. My current 2hp motor is spun to 7000+ rpm and reduced by around 2.3:1 pulleys and leaves me with 3200 rpm max.

How has this servo motor worked out for you? Have you been able to take good size cuts with a 3/8" end mill in aluminum and have you machined steel with it?

I had also considered changing my pulleys closer to a 1:1 ratio, but the fan and motor noise are insane. A different fan could be an option and an encoder could be used.

My machine is similar in size to a tormach 1100, so I don't know how that compares to what you are working with.

Any advice or updates would be appreciated as I have only heard of a few people doing what you have done.

Definitely check the torque curve on whatever motor you want to use, DMM or otherwise. Also: inertia mismatch between the spindle and motor is a thing. I think I ran into that when I initially tried to use a smaller motor, but hard to tell amongst my other tuning issues.

I've got the 1 KW 86mm motor (86M-DHT-A6MK1) on my baby BT30 machine (~14x8x10 XYZ travels and ~500 lbs, IIRC). It's geared ~1:1.5 (motor:spindle), so I can go up to ~7500 RPM at the spindle. After finally getting the tuning right (see below), I'm still finding where the limits actually are, but:

Aluminum: Have gone up to ~3 cubic inches/minute, with 1/4" and 3/8" tools. Haven't had issues.

Mild steel: No issues. I don't remember hard numbers for anything aside from drilling a couple holes in 1018 steel with a 6mm carbide drill. 5000 RPM, ~20 IPM, no problem.

Stainless: I've cut 304 and 17-4 H925. Both cut without issue. I don't remember MRRs for either.

Hardened steel: I modified a screwless vise body, which is probably ~60HRC. Mix of 1/4 and 3/8 tools IIRC, cut fine, albeit with light cuts.

All of the cutting I've done has been within the motor's "continuous" operation power range, per HSMAdvisor (well worth the price, IMO). Just about all of my non-finishing operations are HSM toolpaths, so I can't really comment on slotting.

This may also be of interest for tuning a DMM DYN4: www.forum.linuxcnc.org/38-general-linuxc...dle-servo-tuning-tip