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IndustryArena Forum > MetalWorking Machines > CNC Swiss Screw Machines > LinuxCNC retrofit of a CNC swiss screw machine
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  1. #1
    Join Date
    Apr 2012

    LinuxCNC retrofit of a CNC swiss screw machine

    Hi All,

    Does anyone have any recommendations for which CNC swiss screw machines are easiest to self-service, modify, repair, and retrofit? I'm considering purchasing a used machine and retrofitting it with a LinuxCNC controller for better integration with our otherwise linux-only shop. (I would likely be doing this as an open-source project and publishing the results on github.) My background includes electronics and software engineering, aerospace hardware, and motor controls, but the only CNC machines I've hacked on so far are Sherlines, laser cutters, and 3d printers, so I do expect I may need to make two passes on this -- one machine to learn, then a second after I know what features I actually needed. Primarily I'm looking for manufacturer recommendations right now -- which machines have a good aftermarket for parts, modifications, and documentation?

    If I had to make a choice right now, I'd likely pick a CItizen L20, but that is pretty subjective -- Citizen simply because there's a subforum here focused on them, and L20 because I see them mentioned a bunch -- no idea if that's a reasonable indicator or not. I haven't, for instance, yet been able to grok the difference between an L20 and an A20 -- is it primarily the controller?

    We would be using the machine for small electrical connector parts ranging in size from sub mm up to about .5 inch diameter, in brass and stainless, though I'd also like to try machining PTFE. I'm concerned about my lack of knowledge around the bewildering array of features and options available on screw machines. I do know that we'd need to be able to chuck the part for additional machining after parting off, would be doing milling as well as knurling and threading, and would likely not need to automatically feed new bars for now but may want to add the feature later. For some examples of the sort of parts I'm talking about, see https://www.google.com/search?q=coaxial+connectors

    I do expect to need to mess with LinuxCNC kinematics to drive a screw machine, and I have no illusions about how hard it will be to generate the g-code, particularly since our upstream CAD is all open source (primarly OpenSCAD, FreeCAD, and custom stuff based on https://github.com/deadsy/sdfx) so CAM is always an adventure. These are all things I've dealt with before, but only for 4-axis milling.

  2. #2
    Community Moderator Jim Dawson's Avatar
    Join Date
    Dec 2013

    Re: LinuxCNC retrofit of a CNC swiss screw machine

    An ambitious project. I have done several 3 and 4 axis mills and routers and find those to be pretty simple. I have also done one lathe with a C-axis and live tooling, no Y axis or sub-spindle. It was an order of magnitude more complex than any mill I have done. I think a 7 axis screw machine would be challenging, but not impossible.

    Depending on your budget constraints, I would be looking for a machine that uses servo motors/drives that do not use a proprietary communication protocol to be compatible with LinuxCNC. In other words, simple analog control with the loop closed at the controller. This eliminates the need to replace the servos. Above all, look for a mechanically good machine.

    A Citizen L20 might be a good choice. Good parts availability, and there are a lot of those machine out there.

    Given your background, I don't think you'll have any problem accomplishing your goal. But it certainly will require some tweaking of the LinuxCNC software to make it all work.

    I'll be interested in seeing your progress.
    Jim Dawson
    Sandy, Oregon, USA

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