3D part offset error


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    Default 3D part offset error

    I haven’t used my homemade machine in a while but I’m about to get back work on a the project that I had trouble with in the past. Does anyone know what wi cause offset error when cutting a 3D part using the part flip method. I used 2 dowel pins and reference holes in my part stock material. I think it may be lost steps or acne backlash error but I’m not sure. My part cuts perfect on each side as far as I can tell but is offset by roughly 3/16” in each side only in one axis, the longest dimension of the part.

    I’m using 4 start acme screws, plastic backlash nuts, stepper motors, Mach 4. The machine structure is metal and pretty solid but something is going on and I’m kind of stuck. The part I’m cutting takes a long time to cut and is a long g code program. Also, the offset error does vary from part to part but is always present.

    Any ideas? Thanks

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    Default Re: 3D part offset error

    The error is most likely in the setup or layout in your CAM program. Specifically, the location of your dowel holes.

    Gerry

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    Quote Originally Posted by ger21 View Post
    The error is most likely in the setup or layout in your CAM program. Specifically, the location of your dowel holes.

    If I can cut the same part twice with the same error it should be a CAD issue. If I don’t get the same results twice or if the machine loses it squareness, machine issue.

    Sound good for a test?

    I may just run an air cut program to check squareness first.



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    Default Re: 3D part offset error

    Have you tried reducing the feed and rapid speeds? That should help to indicate if it's missed steps.
    If you've got 3/16" of backlash, you would have other severe issues..
    You could try putting marks on your couplers and shafts and see if the marks still line up the same way when you flip the part and when you're done.
    How much variation in the offset are you seeing? If it's minor compared to the 3/16" or so total error, it may be you've got a CAD/CAM issue as well as a mechanical issue.



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3D part offset error

3D part offset error