Here’s an idea: look for a high count thru-hole absolute encoder with an additional coarse pulse output. Use pulse for tracking speed in normal lathe mode and absolute output for tracking position in C-axis mode.
> On Nov 3, 2024, at 11:05 PM, Ralph Stirling via Emc-users > <emc-users@lists.sourceforge.net> wrote: > > I am toying with the idea of building a benchtop lathe around > a Taig 5C headstock, with a direct drive motor. Frameless motor > components are available relatively inexpensively now from > AliExpress and some other suppliers, and could make a very > clean, compact machine. The spindle tube on the Taig headstock > is 42mm diameter, so everything needs an ID larger than that. > The best component choices I've found so far are: > > Motor: RI85 model 2Nm rated, 5Nm peak, 48V 16A $178 > > https://www.robotshop.com/products/cubemars-bldc-motor-with-potting-robot-arm > > Encoder: 46mm bore 40kppr $71 > https://www.aliexpress.us/item/2255800909154622.html > > I want to be able to do C-axis positioning for mill-turn work, so want > decent resolution. The AliExpress listings for encoders leave a lot > to be desired for both mechanical and electrical specs. For example, > I have no idea what the maximum frequency is for this 40k pulse > (counts?) per rev encoder. The motor is rated for 3100 RPM, and I'd > like to be able to go that fast. That would be over 2MHz. > > I plan on designing a brake to lock the drawtube and use the motor to > open and close the 5C collet. I may make a dinky bar feeder for it. > > Questions: > - Anybody used one of these frameless motors? Anything to watch out for? > > - Any cheaper encoder options out there that would work well? Will this type > of magnetic encoder work for a 3krpm spindle? > > - Any other ideas or suggestions? > > Thanks, > -- Ralph > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
