Milling with a 1.8 Deg stepper motor driven spindle...

[CNCModeller]

Hi,
I'm considering options for a small clean up milling spindle on my printer. One very cost effective option that occurred to me is rather than buying a separate RC brushless motor and esc, I was considering using a small stepper motor on a spare duet driver to spin the spindle.

I guess there are a few open questions on that approach.

• Firstly can I set a fixed rpm to continuously spin a stepper from RRF
• Secondly what is the maximum rpm I could run a 1.8 deg/step motor if that's a practical thing to do?

I'm not expecting to be doing anything but very light cleanup with a very small cutter so I'm not sure the drop in torque at high speed would be much of an issue. But I'd need to do some testing.

Any constructive thoughts would be much appreciated.

Many thanks
Barry M

[TLAS]

@cncmodeller
I would normally never entertain the idea of using a small stepper as a spindle driver... but if your just in plastic, might be worth crunching the numbers:

https://www.custompartnet.com/calculator/milling-horsepower

I’m having a hard time finding the hp/in^3 figure for plastic. If you come across it, you can complete the material removal rate calculations to see the speed you can run it at. FYI, a typical nema 17 motor has about 0.0000007 HP at -900 RPM.

[CNCModeller]

Thanks @tlas, I'll look into this...

Edit:
First pass suggests that "the power requirements for plastics are negligible compared to metals and hence little research has been done".

Also after going through the gcode settings I can't see a way to set a duet stepper output to a fixed speed so it might be immaterial anyway.