Need Help! Z-axis intermittenly cuts deeper than programmed to do.


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Thread: Z-axis intermittenly cuts deeper than programmed to do.

  1. #1
    Member S61TrunkMonkey's Avatar
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    Default Z-axis intermittenly cuts deeper than programmed to do.

    Hello,

    I have a home built machine that has run perfect for about 6-8 months with no issues. Within the past week, the z-axis will cut as told to do so in Mach3 or sometimes it will cut 1-3mm deeper than told to by the Gcode in Mach3.

    Why would a machine cut perfect files as the gcode is wrote half the time? the other half of the time if the gcode says 2mm, it dives in at 5.6mm and cuts the file?

    Facts of the problem.
    1. If I write a file in Aspire, it will save as a Mach2/3 ATC Arcs txt file - no problem.
    2. Mach 3 can open the file and run the file.
    3. Lets say I want the file to cut at 2mm - it's 50/50 if it will.
    4. If the CNC starts cutting the file it may start cutting at 4-5mm. If this happens I can shut down the cnc on Mach3, close the file and reload the file, restart the mill and It will cut 2mm.
    5. If the cut goes deeper than what the Gcode says too Mach3 will see it and display the true depth.

    Hardware
    NVUM V2 5 axis controler
    DM542 Microstepper drivers
    Stepperline 23HS45-4204S stepper motors

    Software
    Vetric Aspire
    Mach3

    Things that have been accomplished, checked, and rechecked during troubleshooting.

    1. The machine is grounded 7 ways from sunday - Good grounding!
    2. The machine is calibrated- Perfectly
    3. All units are in metric.
    4. Z-axis stepper driver DM542 has been replaced.
    5. All mechanical things on the Z axis are clean, tight and lubed.
    6. Homing limits checked.
    7. I slowed down my Z-axis in motor tuning.
    8. I deleted Mach3 and reloaded the software and licence.

    If anyone can help me out, it would be appreciated.

    The American stuck in Germany,
    Jeffrey

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    Last edited by S61TrunkMonkey; 04-02-2021 at 02:21 PM.


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    Default Re: Z-axis intermittenly cuts deeper than programmed to do.

    The usual cause of this is lost steps on the upstroke. The z axis tries to retract to its safe height, but something happens - it can be a lubrication failure, a gall in the slides or screws, something out of parallel, too heavy a spindle assembly, too ambitious an acceleration setting - and it doesn't get to the mark. In an open-loop stepper system, it will assume it did get there, and count the correct number of steps going down, which takes it lower than it's supposed to go.

    Other causes can be the tool pulling out of the collet - spiral flutes can catch and pull - or a set screw failure at the coupling.

    Andrew Werby
    https://computersculpture.com/


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    Community Moderator ger21's Avatar
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    Default Re: Z-axis intermittenly cuts deeper than programmed to do.

    Does the DRO in Mach3 display the actual depth? Or does it always sow 2mm? If it shows 2mm, then it's probably not Mach3.

    Gerry

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

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

    JointCAM - CNC Dovetails & Box Joints
    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)


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    Default Re: Z-axis intermittenly cuts deeper than programmed to do.

    Shows 2mm in Mach3 on the script top left side then shows 5.6mm in the DRO. But the z axis motor will always go back to zero when I tell it to go to zero, so the motor is not loosing steps.



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    Default Re: Z-axis intermittenly cuts deeper than programmed to do.

    Update: I changed out my PC, installed Mach3 and the controller .dll file from scratch, and changed the usb cord. No joy.... grrrrr!! This is now, stepper motor, wire, or the breakout board controller issue. I plan to install a new stepper motor tomorrow. If that does not work, I will change the wire. Updates tomorrow.



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    Default Re: Z-axis intermittenly cuts deeper than programmed to do.

    Update, I changed the stepper motor and wire to the stepper driver. I also changed the wire from the stepper driver to breakout board. I think at this point it’s the breakout board failing. I’ll order a new one and post updates in a few days.



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    Default Re: Z-axis intermittenly cuts deeper than programmed to do.

    Update, I almost bought a new breakout board, but I thought of a test I could perform. The problem is the VFD / Spindle. the program will always start right, and always cut at the programed Z depth when the spndle is not running and the VFD is unplugged. This puzzles me because nothing has changed in months with this machine. I also have the VFD about a foot and a half away from my conrtol cabinet running on a different circuit from what the control panel uses. Anyways, I have ordered EMI filters and a better quality sheilded wire. I will add to my control panel later when the Amazon fairy arrives. I hope my little blog here will help someone.

    When your machine is doing something weird, randonly with no patteren, run your mill with the spindle and vdf unplugged, floating over your table at a safe z height and see if you can reproduce the faults.



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    Default Re: Z-axis intermittenly cuts deeper than programmed to do.

    Quote Originally Posted by S61TrunkMonkey View Post
    Update, I almost bought a new breakout board, but I thought of a test I could perform. The problem is the VFD / Spindle. the program will always start right, and always cut at the programed Z depth when the spndle is not running and the VFD is unplugged. This puzzles me because nothing has changed in months with this machine. I also have the VFD about a foot and a half away from my conrtol cabinet running on a different circuit from what the control panel uses. Anyways, I have ordered EMI filters and a better quality sheilded wire. I will add to my control panel later when the Amazon fairy arrives. I hope my little blog here will help someone.

    When your machine is doing something weird, randonly with no patteren, run your mill with the spindle and vdf unplugged, floating over your table at a safe z height and see if you can reproduce the faults.
    Running on a different circuit is bad, as you have created a Ground loop, ( why did this not happen before ) sometimes bad Grounding practices can take a while to show up, that is why it seems like a mystery

    You said you had more than ( 1 ) Grounding Point, There can only be ( 1 ) Grounding Point ( Star Ground )

    Mactec54


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Z-axis intermittenly cuts deeper than programmed to do.

Z-axis intermittenly cuts deeper than programmed to do.

Z-axis intermittenly cuts deeper than programmed to do.