Converting A Mill To CNC


Have a mill that you’d like to automate? Perhaps you can gets some ideas from the work [James] recently finished. Using familiar NEMA 23 stepper motors (the same motors used in the RepRap), he hacked his Proxxon MF-70 mill for CNC control. Adding a Sanguino and the stepper controllers from other projects, [James] got a working machine for minimal investment. You can tell that [James] is a fan of Polymorph, because he uses it liberally for most of the project, even using it to create some Oldham couplings (Google cache).

After completing the build initially, he managed to burn out the spindle motor by milling steel too quickly. We found it interesting that he was able to use a TURNIGY 2217 860kv 22A Outrunner (for R/C airplanes) as a new spindle motor. Not only is it a low-cost solution, but pairing it with a traditional brushless ESC can give your CNC software direct control over the motor speed.

The image above is an example of what [James’] machine is capable of. Overall, it’s a very accessible project for most of us. Not every mill needs to be capable of 10 mil traces. If you’ve got the urge, you can probably put one together yourself. Of course, if you do, please let us know!

22 thoughts on “Converting A Mill To CNC

  1. I’ve got a Sieg X2 mill I got from Harbor Freight and I’ve been meaning to convert it to CNC… I’ve got all the CNC parts and electronics, and all the material I need to make the mounting parts… I just can’t work up the initiative… :S

    Anyone got some tips that might make it at least SEEM easier?

    1. I have a Sieg mill converted to CNC. The ways are doubled to get a 12″x12″x12″ cutting area. To date, I have cut lots of alumunim (for quadcopter legs on my X650), MDF for sizing, clear plexiglas for engraving, and steel (not the best idea for a small mill). Accuracy is about 2mils. My next step is to develop PCBs using Eagle – they have a nice conversion program – Eagle to Gcode. The host controller is an old Dell PC, Gecko 540 card, and an ELO Touch display which commands Mach3 screens. NEMA steppers handle the ball screws in 3-axes. Overall, I am very happy with the machine. It has it’s quirks, but it works and I learned a lot about CNC.
      There is also a lathe option allowing 4th axes.

    1. 3d printers don’t see the loads that mills and routers see. There’s nothing pushing back on the print head like the wood pushes back against the router bit. you can’t typically get away with NEMA 17 motors on a router or mill.

  2. I thought about changing my milling machine over to CNC but I use it too much manually to do that. If I was to change it over I’d replace the threaded lead screws with ball screws, then I wouldn’t be able to use the machine manually at all. I don’t think anything but the largest NEMA 23 motors would run it either. Really I think I’d need about 450 oz/in motors for it. I have an RF-32 benchtop mill/drill clone.

  3. I did my own MF70 conversion a while ago. It’s a great little mill. Before anyone shout “not a hack” I will say upfront that mine was mostly just sourcing some bits from eBay. However, if you just want a mill up and running easily and cheaply then take a look.

    I also extended the rather limited Y axis with a couple of self-milled brackets.

    I bought some Oldham couplers and have been meaning to fit them but the simple motor attachment I have seems to be working just fine for now and other project have overtaken it. Same with limit switches.

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