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  1. #1
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    Dec 2015
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    Z Axis Plunge during Curve

    Hey. I'm new here so not sure where to post my question. Thanks to all who help.

    Here's the problem. While profiling (using Mach 3) the Z Axis on my Machine progressively goes deeper at certain points. I'm watched the Z Axis move very slightly and stopped to check the code for error. Here's the Code that's causing the problem:

    N204160G1X4.7125Y0.6326
    N204170G1X4.6763Y0.6509
    N204180G1X4.6390Y0.6685
    N204190G1X4.6008Y0.6855
    N204200G1X4.5621Y0.7016
    N204210G1X4.5232Y0.7171
    N204220G1X4.4842Y0.7317
    N204230G1X4.4454Y0.7456
    N204240G1X4.4071Y0.7587
    N204250G1X4.3337Y0.7822
    N204260G1X4.2661Y0.8020
    N204270G3X4.2158Y0.7671I-0.0111J-0.0378
    N204280G1X4.1690Y0.1229
    N204290G3X4.1774Y0.0957I0.0393J-0.0028
    N204300G1X4.1806Y0.0916
    N204310G1X4.1821Y0.0893
    N204320G1X4.1831Y0.0873
    N204330G1X4.1838Y0.0855
    N204340G1X4.1842Y0.0840
    N204350G1X4.1844Y0.0825
    N204360G1X4.1844Y0.0811

    My guess is it's happening on the J- Commands. There's are dog-bone fillets at the 2 J commands, and it looks like the Z Axis starts dropping just after the first fillet up to the second fillet. Just past that code is the point where the next cut in starts, so the Z Axis goes deeper, but then it goes to deep because it already dropped off before. Oh I should also mention that the area between the 2 fillets are curved.

    I've also noticed this progressive deepening of the Z Axis on another job profiling circles. It seems like curves cause the Z Axis to drop slowly, so next time a plunge comes around, it plunges way to deep. I hope all this makes sense?

  2. #2
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    Re: Z Axis Plunge during Curve

    Attachment 301682

    This were on a pocket toolpath. See the difference in depth from where the Z axis started and where it ended. It's pocketing a circle, with no Z Axis movement in the code.

  3. #3
    Community Moderator ger21's Avatar
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    Re: Z Axis Plunge during Curve

    Is the Z axis DRO showing the position change?
    Gerry

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

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

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    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)

  4. #4
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    Re: Z Axis Plunge during Curve

    I'm a complete noob so not sure what DRO is

    But it's not specified in the GCode to move the Z-Axis, and it doesn't show in mach 3 when looking at the units. If I zero the Z axis from there it's out by 0.1 units, sometimes more, depending on how big the circle is. (whatever a unit is in mach 3, haven't manged to set it up so a unit shows in mm).

  5. #5
    Gold Member
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    Re: Z Axis Plunge during Curve

    Quote Originally Posted by SMull View Post
    I'm a complete noob so not sure what DRO is

    But it's not specified in the GCode to move the Z-Axis, and it doesn't show in mach 3 when looking at the units. If I zero the Z axis from there it's out by 0.1 units, sometimes more, depending on how big the circle is. (whatever a unit is in mach 3, haven't manged to set it up so a unit shows in mm).
    Sometimes it happens because of "spring", if your machine is not rigid enough. As you start, the axes are moving faster than the tool can cut so it springs. Then as it ends a profile or has to go around a sharp turn it slows down, which increases the amount of "cuts" if you will of the spindle over a certain distance, which allows it to dig deeper into the material.

    You can try running the program slower, or set the accel a little slower, or raise the spindle speed to see if that helps. You can run the program, then re-run it to see if it removes any depth change. Then you'd know you have to beef up one or more of the axes.

  6. #6
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    Feb 2021
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    Re: Z Axis Plunge during Curve

    resolved my issue blogger at : https://ptclbill.net/ptcl-speed-test/

  7. #7
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    Re: Z Axis Plunge during Curve

    I also have the issue someone please take a look. https://fescobill.pk/fesco-duplicate-bill/

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