CNC Mill Motor replacement

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negativentropy

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Hi, Im looking for suggestions for replacing the very wimpy spindle motor on my home built cnc mill.

This converted mill was given to me a few years ago, its decently rigid and the person that built it put huge steppers on it. The spindle motor however is the original that came with the manual mill and is under powered, but worse, has a really low max RPMs. Details:

Original mill before conversion: ZAY7025FG
Spindle Motor: 370W, 1700 RPM induction motor
RPM options (H,L 1,2,3): 1700, 1120, 600 320, 220, 115

Conversion details:
C7 ballscrews on all axis
KL9082 Drivers
KL34H2120-60-4A Steppers (1200 Oz-In) on all axis

I use LinuxCNC as my controller. Ideally what I want in a replacement is spindle control (on, off, RPM), higher max RPMs (for better aluminum and plastic milling), more power for heavier cuts (I think the machine rigidity and steppers can handle it), and to completely bypass the gearbox of the spindle (it is loud and clunky and would be unnecessary if I had RPM control)

The simplest option would be to just upgrade to a higher power, 3400 rpm induction motor, it would be an easy swap and would get me at least more RPM and torque for heavier cuts.

But if im going to go to the effort, really I want full motor control, and ideally bypassing the gearbox.

What are my options. Is Odrive on a BLDC motor realistic?
 
You would be better off to go with a 1750 RPM motor (4 pole), twice the torque of a 3450 RPM (2 pole) motor at a given HP. If you can physically fit a 2 HP inverter duty motor on the machine and use a direct belt drive you would be able to reasonably have a usable spindle speed range of about 30 to 4000 RPM when using a sensorless vector VFD with a 1:1 direct drive.
 
Two questions: can a VFD drive a motor beyond its rated RPM? Can you control a VFD with gcode?
 
negativentropy said:
Two questions: can a VFD drive a motor beyond its rated RPM?
Click to expand...

Yes. Most good 3 phase motors are rated at 4000 - 6000 RPM max. I wouldn't try that with a cheap import motor.

Can you control a VFD with gcode?
Click to expand...

Yes. M3 S3000. Now having said that you need an analog output from your controller. If the controller analog output is stable enough you may not need encoder feedback.
 
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What about using a DC motor and driver? Looking at prices for a 3 phase motor and VFD, pricey!

Working on pictures
 
You haven't looked at the price of a DC motor and controller :)

This Baldor motor is rated at 6000 RPM max https://www.ebay.com/itm/Baldor-Rel...=item23a7cc3f40:g:e2YAAOSwdVZbcsO7:rk:17:pf:0

Another option would be the DMM-Tech servos. The 1.8KW (2.4hp) units are popular for spindle motors on machines like yours, and are less money than a new 3 phase motor and VFD. https://store.dmm-tech.com/

I use these for axis drives on my lathe, and just built a small punch press using those servos for the crankshaft and feed drives.
 
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