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  1. #1
    Join Date
    Jul 2008
    Posts
    12

    Trouble making smooth contours

    I have been trying to solve this issue for many months. I have a DIY cnc. I am using it to make guitars. It works quite well except for when it come to cut the contour shape of the guitar. It seems that when it's cutting straight lines it's fine. Curved shapes seem to produce a scalloped shape while making the curve.

    I have included a pic of a problem curve as well as the g code for 1 pass around the contour.
    I have tried so many settings in master cam and mach3 i can no longer count them. I have tried to reduce the gcode to use radius cutes instead of point to point. Perhaps i gone too far.
    Attached Files Attached Files

  2. #2
    Join Date
    Mar 2003
    Posts
    35538

    Re: Trouble making smooth contours

    Is the long axis ballscrew as well, or is it driven differently?

    It could just be flex in your machine. Those thin fiberglass plates are not very rigid.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  3. #3
    Join Date
    Jul 2008
    Posts
    12

    Re: Trouble making smooth contours

    This is possible. I used g10 garolite because i could make them with my old cnc. It seems rigid. I have been thinking about having them cut in aluminium. 1/4" or 3/8". Thoughts?

  4. #4
    Join Date
    Mar 2003
    Posts
    35538

    Re: Trouble making smooth contours

    Take the tool out of the spindle, then grab the collet, and push in pull in all directions. If it moves any amount, it's not rigid enough.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  5. #5
    Join Date
    Dec 2003
    Posts
    1206

    Re: Trouble making smooth contours

    The scallops look very evenly spaced and appear to go all round the instrument at fairly regular intervals.Mastercam used to have a menu option for cutting a curve using all straight line moves and you could select the maximum deviation from the original curve that would be acceptable.Have you found this item and activated it?

    As for your sideplates,have you considered bolting a length of steel angle to the outside face to add stiffness?

  6. #6
    Join Date
    Apr 2016
    Posts
    16

    Re: Trouble making smooth contours

    Hi,

    The Facets could be in the model, so the CAM just outputs them.
    Make sure that the CAD system has the Curves/Facet resolution set to the finest possible, then re-generate the model (A lot of people forget this small step) and save.
    Now post process the new model (again with any curve fitting etc set to it's finest level) to see if that solves the problem.

    Nick.

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