Polar CNC?

  • I have aquired 2 Parker Daedal linear tables and a rotary table with vacuum table in an assembly with SLO-SYN KML061F03 stepper motors, SLO-SYN SS2000MD7 drives, 48V linear power supply, 24V linear power supply, and a few misc sensors and steppers that came from a prototyping rig. Crazy idea, but since I picked up this stuff for next to nothing I was thinking about using the rotary table and one linear table for polar with the other linear table for Z axis for a miniature CNC mill. Does anyone have any experience with using the polar kinematics for CNC milling or will it not work? If it will work does anyone have a suggestion between Duet 2 or 3 for controller board? I have only built printers so I have no experience with CNC milling equipment.

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  • FYI, I've done a lot with CNC machines and rigidity is your biggest problem with the setup above. If the head mounts on that frame, I'd bet you could barely do wood reliably. There's a lot of CAD/CAM software out there that can take a 4th axis to do 4-axis milling, although it's generally more expensive as 3-axis linear milling is the bread and butter unless you're doing something really complicated. If you're looking for something to do with the rotational axis, I'd highly suggest you put that on top of a 2-3 axis linear system instead of substituting it. If wood is OK, you can find small Chinese routers at about the price of a single Duet card.

    If you are interested in CNC milling, I'd recommend you strip the electronics and put it on something like a Grizzly G0704 (~$1k) or a used Bridgeport (~$1-5k). Grizzly should be able to do aluminum or mild steel. Make sure you have a Bridgeport or similar if you ever plan to do any materials that are harder to machine (stainless steel / titanium). Downside to a Bridgeport is that they typically weigh a ton (literally, >5k lbs) and operate on 3-phase power. They can't be beat on rigidity and setup tolerances though.

    Also, CNC milling is a profession - if you're interested in it, I highly suggest you take a college course on machine shop basics before diving in. It can be highly dangerous if you don't know what you're doing and there's a reason many professional machinists are missing fingers. Steppers of that size can crush fingers easily not to mention other dangers while actually cutting.

  • Sorry, should have mentioned I have no intention of using the aluminum frame it came with. Was thinking of possibly making it an add on mount for my lathe/mill or possibly building a stand alone micro for very small (less than an inch work piece) mill. I didn't know if the polar kinematics would be appropriate since I have the parts to implement that.

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  • For tax purposes before midnight I went ahead and ordered another Duet 2. If CNC mode and polar kinematics don't play well together at least I've got another board for a printer.

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