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1500 x 1500 mm OpenBuild CNC

Discussion in 'CNC Mills/Routers' started by ACASTELLINI, Apr 2, 2016.

  1. ACASTELLINI

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  2. ACASTELLINI

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    Hello,

    I have around 1.5 mm (0,039 inch) less than the desired measurement.
    And this for a piece of 100 mm (3,94 inch) as for a piece of 1000 mm (39,37 inch) .

    Have you ever had this problem?

    Thanks in advance

    Adrien
     

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  3. Giarc

    Giarc Master
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    Sorry I can't help with your problem, but I have a question regarding your Makita router mount. Is that just a 65mm mount for the Chinese spindles? I plan to use a Makita, but I don't have easy access to 3d printer to make a shim so I thought I would order a mount designed for a water cooled spindle. Thanks.
     
  4. Giarc

    Giarc Master
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    Thanks for the information
     
  5. Steve Fox

    Steve Fox Veteran
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    If you are saying that the pieces you are cutting are 1.5mm smaller than your desired measurement, there are several things that could cause this. The first is that the but you are using is larger than the published diameter. It could also be runout in your router.

    The fix is in the software. all the software packages I use allow an adjustment of the bit diameter and/or an offset adjustment for the part.

    In any event, this isn't unusual and can be corrected quite easily.

    Steve Fox
     
  6. Ronald van Arkel

    Staff Member Resident Builder Builder

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    It's not easy to get a belt driven 1220*1220 router work as they should be. Double belts, one in the track and one for the movement, are no luxery. Leveling the bed can be tricky and I recommend to use a transparent hose with water to level all the corners, sure, first having the corners square. Also, a NEMA17 for your Z-axis probably will be underpowered when you do 2.5D carving, but that's easy to change.

    Steve Fox is probably on your problem, a 1/4" tool can be off a bit so it will be 1/4" and a little, still, 0.75mm from center is a bit much.

    -Ronald
     
  7. GrayUK

    GrayUK Master
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    Ronald. Forgot about the transparent hose and water level trick. :)
    Good one. :thumbsup:
    Thanks
    Gray
     
  8. Paruk

    Paruk Master
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    Hopelessly complicated, transparent hoses with water. ;-)

    Just take a wire (fishing stuff or so) span it from left front corner to right back corner and from left back corner to front right corner. All of course on top of the profiles. This way you will form a X of which the crossing should be exactly in the middle of your table and the wires at that crossing should only just kiss each other. Adjust the corner(s) that is (are) out of line until they just touch. Et voila! Your CNC is flat (the Y axis, that is).

    For squareness of the CNC, measure from the left front corner to the right back corner and compare that with a measurement from the right front to the left back corner. If they are the same, the frame is square. If not, adjust until both measurement are EXACT the same.

    Ronald is right about the double belts. I'm using it for about a year and have no accuracy problems (except for missing steps because of other reasons) whatsoever.

    Always measure your bits with a proper Vernier callipers (Mitutoyo is the best I think) and insert that value in your CAD and CAM programs. Do not assume the size, it will be off.

    Measure also the backlash. Videos of how to are al over Youtube.

    If you do this all correct, and some extra checking here and there, your Ox will be as accurate as can be for such a machine. I have about 0.05 to 0.1 accuracy (depending on temperature and moisture in the air, tropics you know).
     
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  9. GrayUK

    GrayUK Master
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    I like the centre crossing point! :thumbsup:
     
  10. Paruk

    Paruk Master
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    Me too, Gray!;)

    About the bits, I was not complete. Only described the first part of it. After measuring the bit size for a first cut, you then measure the real life cut of that bit in your router to get the true size of the cut. That way you will also account for runout of your router and other minor in-accuracies. The width of the cut divided by 2 is your true tool radius. Use that value in your CAD and CAM software.
     
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