G00 Rapid on CNC Mill - question
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  1. #1
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    Default G00 Rapid on CNC Mill - question

    Hi fellow members.

    On a Matsuura MAM72-VS (Vertical machine with B axis tilt / C axis rotation) I'm running into a situation with simultaneous 5-axis rapid motion. That is, the axis are completing their commanded motions interdependently, and I get a "dog leg" effect.

    I would like the Fanuc 16i-M control to manage the rapid moves to arrive at destination simultaneously. Unfortunately, I don't know the parameter setting, if there's even one.

    Thank you for your help.

    Mark S.

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    What are you programming with? Most CAM that I'm familiar with have a "Rapid Feed" option, so it will "FEED" using G1, but at a faster rate (user defined). This eliminates the dreaded dogleg.

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    From the parameter manual, it appears it may be 1401 bit 1 LRP:

    LRP Positioning (G00)
    0: Positioning is performed with non–linear type positioning so that the
    tool moves along each axis independently at rapid traverse.
    1: Positioning is performed with linear interpolation so that the tool
    moves in a straight line.

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    https://jamet.com/Fanuc_Web_Manuals/...nt/63530EN.pdf

    Parameter 1401 Bit 1(second from the right), labeled LRP. Set it to 1 for linear rapids, set to 0 for dogleg.

    You may want to call Matsuura to make sure that won't break anything and there's nothing else you need to change, considering it's a 5 axis. I saw a handful of other parameters that change behavior based on the state of that one.

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    One should keep in mind that the linear rapid G00 function is not the same as linear interpolation G01 function. The linear rapid is "approximately" linear, not as tightly controlled as G01 linear interpolation. On smaller machines the error is typically very small as to be unnoticeable. On large machines (1.5 meter + travels), I have seen deviations of at least an inch when comparing rapids at 25% versus 100%.

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    Or you could just do G1 at maximum feed rate.

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    I think this explains the behavior I am seeing on a program on our MX-520! It goes into G00 to transition along a shortest path and does very slow, jerky moves?

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    Quote Originally Posted by Tichy View Post
    Or you could just do G1 at maximum feed rate.
    That's a good point. Have you tried setting your CAM post to output high feed moves instead?


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