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  1. On my concrete mill (Thor) I run CS Labs IPA with Panasonic servos. Ive always noticed that on circles and similar I get jerky movement, specifically where there are I and J type G Code involved.

    I did a test last night, took the same code, ran it on my Bridgeport, running on Centroid Acorn, same Panasonic setup but in Step / Direction (Position mode) versus Speed move as per Thor. The same code was smooth.

    Ive seen a lot of complaints about Mach 3's smoothness.

    Is my issue a limitation with Mach 3 (or badly configured), related to not having good PID on the servos or something else?

    I might try the new SimCNC software from CS Labs to see if its Mach 3 or not. A newer PC might also help.

    Thoughts?
    Last edited by Chaz; 3 Weeks Ago at 08:52 AM.

  2. #2
    Quote Originally Posted by Chaz View Post
    On my concrete mill (Thor) I run CS Labs IPA with Panasonic servos. Ive always noticed that on circles and similar I get jerky movement, specifically where there are I and J type G Code involved.

    I did a test last night, took the same code, ran it on my Bridgeport, running on Centroid Acorn, same Panasonic setup but in Step / Direction (Position mode) versus Speed move as per Thor. The same code was smooth.

    Ive seen a lot of complaints about Mach 3's smoothness.

    Is my issue a limitation with Mach 3 (or badly configured), related to not having good PID on the servos or something else?

    I might try the new SimCNC software from CS Labs to see if its Mach 3 or not. A newer PC might also help.

    Thoughts?
    I think there is a setting tick box in Mach3 to use arcs CV mode
    ..Clive
    The more you know, The better you know, How little you know

  3. Quote Originally Posted by Clive S View Post
    I think there is a setting tick box in Mach3 to use arcs CV mode
    Thanks. Ill check. I was actually surprised the code worked as standard on the Bridgeport. Suppose its feasible despite different post processors.

  4. I'm looking at a screenshot of the General settings page, I dont see it. Any idea where it is?

    https://www.machsupport.com/wp-conte...all_Config.pdf - page 5-35 is the General Settings Page.

  5. #5
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 13 Hours Ago Has been a member for 6-7 years. Has a total post count of 1,246. Received thanks 236 times, giving thanks to others 5 times.
    I use Mach3 and an IP/M on my router and have never noticed any jerkiness on curves. Don't know if that is luck or the right settings! I've been using F360 with various cutting strategies recently, some of which use a large number of short straight line segments which Mach3 seems to handle ok. So it seems ok whether or not G2/3 or straight line segments are used. I am using steppers rather than servos and it does seem possible that servo tuning would have an effect here.

  6. Quote Originally Posted by Neale View Post
    I use Mach3 and an IP/M on my router and have never noticed any jerkiness on curves. Don't know if that is luck or the right settings! I've been using F360 with various cutting strategies recently, some of which use a large number of short straight line segments which Mach3 seems to handle ok. So it seems ok whether or not G2/3 or straight line segments are used. I am using steppers rather than servos and it does seem possible that servo tuning would have an effect here.
    Thanks. I have no issues with straight lines, its when arcs / circles are involved.

  7. #7
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 13 Hours Ago Has been a member for 6-7 years. Has a total post count of 1,246. Received thanks 236 times, giving thanks to others 5 times.
    I was thinking of the case where F360 is approximating non-circular curves (e.g. adaptive clearing strategies) using many very short straight line segments so there are a lot of rapid direction changes. Mach3 is supposed to smooth these, as I understand it. This kind of tool path is bad news if Mach3 is configured to "exact stop" mode but in constant velocity mode it's fine.

    On reflection, though, probably not very relevant as you are using analogue servo controls which introduces a whole bunch of other variables. Good luck!

  8. Quote Originally Posted by Neale View Post
    I was thinking of the case where F360 is approximating non-circular curves (e.g. adaptive clearing strategies) using many very short straight line segments so there are a lot of rapid direction changes. Mach3 is supposed to smooth these, as I understand it. This kind of tool path is bad news if Mach3 is configured to "exact stop" mode but in constant velocity mode it's fine.

    On reflection, though, probably not very relevant as you are using analogue servo controls which introduces a whole bunch of other variables. Good luck!
    Yep and the same code runs without an issue on Centroid.

  9. #9
    phill05's Avatar
    Lives in Derbyshire  UK, United Kingdom. Last Activity: 23 Hours Ago Has been a member for 9-10 years. Has a total post count of 208. Received thanks 17 times, giving thanks to others 10 times.
    Quote Originally Posted by Chaz View Post
    I'm looking at a screenshot of the General settings page, I dont see it. Any idea where it is?

    https://www.machsupport.com/wp-conte...all_Config.pdf - page 5-35 is the General Settings Page.
    Have a look at 5.6.6.2, I/J Mode: You can set the interpretation to be placed on I & J in arc moves. This is provided for compatibility
    with different CAM post-processors and to emulate other machine controllers. In Inc IJ
    mode, I and J (the center point) are interpreted as relative to the starting point of a center format arc.
    This is compatible with NIST EMC. In Absolute IJ mode, I and J are the coordinates of the center in
    the current coordinate system (i.e. after application of work, tool and G92 offsets). If circles always
    fail to display or to cut properly (especially obvious by them being too big if they are far from the origin),
    then the IJ mode is not compatible with your part program. An error in this setting is the most
    frequent cause of questions from users when trying to cut circles.

    Phill

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  11. Quote Originally Posted by phill05 View Post
    Have a look at 5.6.6.2, I/J Mode: You can set the interpretation to be placed on I & J in arc moves. This is provided for compatibility
    with different CAM post-processors and to emulate other machine controllers. In Inc IJ
    mode, I and J (the center point) are interpreted as relative to the starting point of a center format arc.
    This is compatible with NIST EMC. In Absolute IJ mode, I and J are the coordinates of the center in
    the current coordinate system (i.e. after application of work, tool and G92 offsets). If circles always
    fail to display or to cut properly (especially obvious by them being too big if they are far from the origin),
    then the IJ mode is not compatible with your part program. An error in this setting is the most
    frequent cause of questions from users when trying to cut circles.

    Phill
    Thanks. Ive messed with this before. Normally when its wrong, it doesnt cut the right tool path at all. I dont think that's the issue here.

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