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  1. #1
    Junior Member
    Join Date
    Jul 2017
    Posts
    56

    Need help with motion problems

    I built a cnc that has an ESS motion controller run on Mach 4. My motors do not run smoothly (shuddering, staggering movement) when running a cut around curves. I've tried switching from exact stop to constant velocity mode, I've expanded my look ahead lines from 20 to 190 as well as removing anything on my computer that might interfere with the cut. I've also tried adjusting the motor tuning velocity and acceleration. I've also tried adjusting the current on my stepper motors. Still I haven't been able to get the motors to run smoothly. Does anyone know what else could be causing the issue? Should I try adjusting the micro stepping on the drivers?

  2. #2
    Member
    Join Date
    Jul 2018
    Posts
    1028

    Re: Need help with motion problems

    Hi 66 -
    Yes microstep settings can help but also check what you are actually cutting. Are you cutting true arcs or a polyline? If you are cutting a polyline then the length of the separate lines affect the motion. If the line is long enough that the motion controller thinks it can accelerate then it will try but it will then have to slow down for the next one. So if you are using dxf for your imports into CAM set them at say 1mm long so it will slow the machine down or export as true arcs and see if it is different. Do a large square so the polyline does not matter then move onto true arcs then polylines. If this all fails then its a motion setting or a mechanical setting. Cheers Peter

  3. #3
    Junior Member
    Join Date
    Jul 2017
    Posts
    56

    Re: Need help with motion problems

    Thanks so much for your assistance Peter. I'm not an engineer...and I don't even play one on TV! I think that the issue is simpler than that of arcs vs poly lines. The shuddering occurs greater (on the X axis) when the machine is moving from one side (the left when I am facing it) of table to the right than from the right to the left. I did try adjusting the micro steps and that didn't affect the shuddering issue. Because I am neither a mechanical or electrical engineer, I fear that I may have built or wired my machine to make it prone to this. I mostly wired everything using 18 gage wire, I have three standard switching power supplies (one five volt, to power the Ethernet smooth stepper/one 24 volt and one 48 volt that power the drivers-four DM542T stepper drivers driving two 425 Oz*in NEMA 23 for the Y axis, a smaller NEMA 23 for the X axis, and a NEMA 34 (or 32, I forget) for the Z axis. All are driven by precision ball screws and linear guide rails on a frame made of 80/20 aluminum extrusion profile 3030. The size is approximately 1400mm on the Y axis and 1200mm on the X axis and 500 on the Z axis. My ESS is also connected to a PMDX-126 BOB. I initially tried to wire up the end stops (using some proximity sensors that I had) and though I got them to function, they became cumbersome and unreliable due (I believe to electrical noise) so I just removed them until a later time. One thing I am wondering is if I may have a grounding issue. What kind of problems occur if your machine isn't properly grounded?

  4. #4
    Junior Member
    Join Date
    Jul 2017
    Posts
    56

    Re: Need help with motion problems

    BTW, the cuts that I was trying to make were from files that were out of Fusion 360. I tried just cutting a square (or actually cutting the contour of a box from Fusion) as well as the contour of an ellipse, and finally a 3D parallel cut of half of a revolved ellipse. The same shuddering occurs during all the cuts, but especially ones that have curves. BTW I have repeatedly checked the status of the problem by "air cutting" a contour of a circle from Fusion.

  5. #5
    Junior Member
    Join Date
    Jul 2017
    Posts
    56

    Re: Need help with motion problems

    I attempted to cut the trial v-carve cut "Bullshead" with my machine today and this was the result:


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