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40186Re: [hobbicast] [off?] CNC Machine Running

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  • Jeshua Lacock
    Feb 1, 2010
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      On Feb 1, 2010, at 8:39 AM, Todd wrote:

      > Jeshua, nice work! I've been working on a Gingery Lathe for about 4
      > months w/o nearly the progress to show for it :o).

      Sounds like a great project. One of the first things I plan to do with
      my CNC machine is make the patterns I need to make a turntable and a
      lathe "attachment" for the CNC machine...

      > Q: What is the 3D visualization/CAD software that you show in the
      > first
      > part of your demo?

      It is a free application called Meshlab. It is not so much for
      modeling as it is a great 3D utility.

      I used it to reduce the complexity of the model that the CNC machine
      made and saved the model as a DXF as was required by Pycam.

      > Q: You mention in the thread that you used pycam. Could you
      > elaborate on
      > your CAD tool chain...and how well it's working for you? I've been
      > using
      > QCad...but it's a 2D only option...though somehow they have an
      > additional GCode module, too.

      I have been evaluating Vectorworks. It will create true surfaces or
      solids that can be used by high-end CAM software.

      The bonus for me is that it runs natively on the Mac.

      But for my first run, I just download a free model, reduced the
      complexity in Meshlab (on my Mac) and saved as a DXF, then copied to
      my Linux machine, opened the DXF in Pycam, saved the G-Code, and then
      opened in the EMC machine controller software.

      The cool thing is it was all done just between my Mac and my Linux
      machine from which I can control on my Mac. So I feel right at home.

      > Q: You mention using the Roton ballscrews/nuts for your z axis... have
      > you needed a brake? I ask b/c the Roton site claims that the
      > translation
      > of force to rotation is so efficient that their devices cannot be
      > counted on to self-brake.

      It is so efficient that when I got the ballscrew, just the weight of
      the ballnut would make it roll down the screw by gravity alone. It got
      up to a pretty healthy RPM too. So I wasn't sure if I would still need
      a break. I thought if nothing else, it would be much slower than a
      straight drop.

      But once I mounted it on my machine, the TDK rails with such a tight
      tolerance was just enough friction that it does not require a break. I
      think if it was using skate bearings instead of TDK bearings, it would
      like still need a break. Or if my router was any heavier....

      > Q: What linear motion system are you using, and what are it's
      > performance characteristics (flatness, deflection, etc.)?

      I am using a different linear system for each axis.

      I would have liked to use TDK everywhere - but the get very spendy
      when you need them 5 feet long.

      For my big Y carriage I am using VXB bearings:


      For my X, I am using a skate bearing carriage that I got from:


      It just used a 1/4" steel plate for the guide. If I were to do it
      again, I would use these for the Y as well. Very nice system, low
      cost, cheap and easy to replace the bearings, and the bearings are
      sealed. The VXB system, the bearings are essentially open.

      And for the Z, I picked up some used TDK linear bearings on eBay.

      As for deflection, all of the rails are mounted on very rigid
      surfaces, so I think that would be very minimal.

      > My plan is to build the Gingery series and then start on a CNC...
      > probably very similar to yours. At my current rate, I should be
      > starting
      > that project in about 2-5 years :o).

      Good luck! Sounds fun.


      Jeshua Lacock, Owner
      phone: 208.462.4171
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