Problem Arc endpoint issue


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Thread: Arc endpoint issue

  1. #1

    Default Arc endpoint issue

    I'm trying to modify the Heidenhain ISO G-code post-processor in Aspire 8.0 to work with an old TNC151. So far I've had a lot of luck, except I'm having problems with arcs. None of them seem to work.

    Here's an example that Aspire generated which blew up:

    N114 X+1.8966 Y+1.7487
    N115 X+1.9215 Y+1.7386
    N116 G02 X+1.9375 Y+1.7309 I-0.0187 J-0.0596

    It gave me an error: CIRCLE END POS. INCORRECT

    Doing some math:

    The arc radius from the endpoint of N115 (the start of the following arc) and the center I,J is 2.64535428251
    The radius from the endpoint of N116 (the end of the arc) and I,J is 2.65190661412

    So the radius error is 0.00655" between the two. This doesn't make sense to me. Given that Aspire outputs positions readable to 0.0001" for both G01 and G02, I'm very surprised to see that the arc endpoints would have such a different radius relative to the circle's center. Is the TNC 151 being unreasonable in its expectations of accuracy? Or is Aspire just being very sloppy?

    I know I can set up a no-arcs post-processor, but I'd really rather get the arcs working. Any thoughts?

    Thanks,
    Ryan

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  2. #2
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    Default Re: Arc endpoint issue

    I think Vectric sets their toolpath tolerance to .004" by default, you may want to try change that....



  3. #3
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    Default Re: Arc endpoint issue

    Check the CNC programming manual
    - our Heidenhain, for the arcs, the IJK is the absolute center of radius

    ie 2" semi-circle at X0Y0

    G1 X+1 Y+0
    G2 X-1 Y+0. I+0. J+0.



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Arc endpoint issue

Arc endpoint issue