Calibration tips


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Thread: Calibration tips

  1. #1
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    Default Calibration tips

    HI im looking for advice on trouble shooting my y axis calibration. I have a year 2000 4x8 warthog style cnc router with ball screws on all axis. the y axis is belt driven on a center screw. it has a new control box containing geko drivers. I am running a windows 10 pc with uccnc. The X and Z will give me repeatable results, but the y axis will give me varied results. mostly undersized. I have calibrated using the software about 7-10 times and I still get a varied result. Is there possibly something else at play here that im not recognizing. Am I possibly loosing steps somehow? Can I loose steps if the machine is underpowered or has a drop in power during a run?



  2. #2
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    Default Re: Calibration tips

    Hi,
    I would guess from your description that you are indeed losing steps on that axis.

    Steppers miss steps when thy are overloaded, and gets very much worse the faster you go.

    There are basically two broad scenarios you need to consider:
    1) The stepper is too small/underpowered for the job you want to do
    2) There is a fault with either the mechanical travel delivery or the stepper and/or driver has a fault that means that its much less
    powerful than it should be.

    May I suggest that you make a series of tests to determine which of these two scenarios applies.

    For instance if you disconnect the ballscrew coupler such that the stepper has no load, and then run the stepper backwards and forwards....does it lose steps?
    If it does try the same thing but at very much reduced accelerations and max velocities as determined by UCCNC settings. If without load the stepper misses steps
    even at very slow speeds suggests that either the stepper is very much undersized or faulty. If the other steppers on the machine are the same size you might
    substitute the stepper out, or the driver, or both. You may then determine that one driver is faulty for instance. You need to pay attention to logic if you proceed
    with 'trial by substitution', try to have ONLY ONE changed component at each test cycle.

    With the ballscrew uncoupled rotate it by hand throughout its range of travel...does it travel smoothly or bind up?. Is it plain stiff or is it cyclic?

    With the ballscrew coupled, and assuming no mechanical binding etc, try running the axis at slow or even very slow speeds. If that is OK then try gradually upping
    the speed until the missing steps problem recurs. Then you need to decide/asses whether the result is because of an undersized motor or a fault with motor or drive.

    Craig



  3. #3
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    Default Re: Calibration tips

    Thanks Craig. I can run the y axis pretty fast(450-500ipm) before the motor stalls. I do notice that there are a couple of sticky spots when im jogging in the long direction, but I didnt think they were considerable enough to make the motor or motion malfunction. But maybe they are, I dont really know anything... I do also wonder about my power supply. I was running a part the other day and my dad turned on another machine in the room, when this happened the router took a dive inward of the cut. Should I be running the machine on some sort of power conditioner being that my shop electrical is not the greatest? Also the drivers are brand new geko g201x drivers that automation technologies set up for me. The motors are 21 years old however, maybe they are getting tired?



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