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variable speed motor

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Derek Mackenzie27/02/2021 20:11:10
5 forum posts

Does anyone have a recommendation for a 250W (or thereabouts) variable speed motor for a small lathe & mill? Preferably a reasonable price, quiet, small with speed controllable through Gcode?

Emgee27/02/2021 20:41:54
1988 forum posts
250 photos

Hi Derek

A 3 phase delta connected motor operating at 230v will do what you require if controlled by a VFD.
Power supply is single phase 230v and the VFD will output 3 phase 230v, so you can run on a normal domestic power supply.
Motors are available with 1450 or 2800 rpm on 50Hz supply and as the VFD will provide a variable frequency output the motor speed can be reducer or increased to suit your machine.

If buying a new motor best to get one that is suited to VFD operation so full benefit at low speeds can be achieved.
Nearly all VFD's can be controlled by a 0-10v signal so your cnc program will need to have the facility to output the voltage to suit rpm called for in the cnc program. Mach and Linux both have that option.


Edited By Emgee on 27/02/2021 20:51:42

not done it yet27/02/2021 22:52:11
5790 forum posts
20 photos


As Emgee, but in addition a motor that is a little too powerful could be run in star configuration with the VFD. A half horse power motor (a common size) would be reduced to around 220W.

Steviegtr27/02/2021 23:24:29
1976 forum posts
268 photos

With most vfd's i have worked on. You can use 0-10volts for speed control or 4-20mA & some have rs232 input too.


Derek Mackenzie28/02/2021 23:32:26
5 forum posts

Thanks for the replies, but those types of motors appear to be too big for the space I have available. I am planning on fitting a Taig micro lathe (with 5C headstock) in front of the table of my Taig CNC mill so the mill drives a rear toolpost in the X & Y axes (now Z & X respectively for the lathe) for turning mainly brass up to 1" maximum diameter by 3" length. This all has to fit into the current mill enclosure which gives a maximum of around 4" diameter for the motor. This is to replace my current old East German HobbyMAT lathe that I converted to CNC over a decade ago. The problem with the latter is both backlash and being a bit too stiff for the Z axis stepper. I have given up trying to improve both of those and am now looking for alternatives - real CNC lathes are too expensive & too big.


Edited By Derek Mackenzie on 28/02/2021 23:33:13

Emgee28/02/2021 23:38:31
1988 forum posts
250 photos

You could go for 1 of the PM DC motors being sold on eBay now that can be speed controlled manually, you could still start/stop via a cnc controlled relay and manually adjust the speed as required.

These motors will be noisier than any AC motor.


Steviegtr28/02/2021 23:53:23
1976 forum posts
268 photos

Or you could if finances are short. Buy a sewing machine motor with foot pedal . They are quite powerful.


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