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24000mm/min speed with 1000m length V Slot Actuator problem

Discussion in 'Other Builds' started by Anlu, Feb 22, 2022.

  1. Anlu

    Anlu New
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    Hi there,

    I have built a few actuators and came recently across a problem i am trying to solve, maybe some of you has some valuable input:

    I can drive up to 500mm vslot with both mini gantry or normal gantry plate up to 24000mm/min (40cm/s) without any problem. I also use 10mm GT2 Belt and 36 tooth pulleys.
    Now i need the same speed for 1000mm lengths actuators and there a strange / unusual behaviour appears: Appr. after the 2/3 of the way the plate begins to rumor, and only when its over 50% of full speed, below everything is still fine. I checked all possibilites (motor is not stalling, all other mechanical parts are ok etc.) before, but my conclusion is for now that the wheels of the gantry plates are not made for this speed and length. Because when i loosen the fix of the wheels everything works fine again, but of course the plate runs now loosely which isnt a good solution.

    So i wonder if some of you already had this bevahiour and / or an idea how to solve this?
    I am trying now the different variations of the wheel to see if this work, but any other hint is greatly appreciated.

    Thanks,
    Andreas
     
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    What does Rumor mean? Stepper motors can stall at high RPM, do you mean its stalling? Set you Max Rate appropriately: For example, for Grbl: Grbl v1.1 Configuration · gnea/grbl Wiki


    Are you sure? Acceleration taken into account you may think its already at 24000, but perhaps its still on the bottom curve of the acceleration curve, and then starts decelerating. That would hide your stalling issue until it has more space to run-up to a speed fast enough to cause a stall.
    Punch you acceleration and feedrates into RepRap Calculator - Prusa Printers and see if it would reach the commanded speed in the space available.
     
  3. Anlu

    Anlu New
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    Hi Peter,

    thanks for your fast reply!

    No its definitely not a stall, its more a mechanical noise, a short vibration or such and as i said it´s not anymore when the wheels are more loose and not so tightened. Also for the distance between 0 and 500mm everything works fine. You have experience if the solution with the wheels are not perfect for this high speeds and length but linear glides or else would be better?
    To me it sounds it´s also partly for this speeds and lengths the rails need to be more mechanically precise, since little deviations will have a bigger effect. I have in total 10 actuators and they all behave a bit differently with this behaviour, so i think its also a bit how they are set up.

    No Acceleration curve is pretty short, the ramp is over after appr. 40mm, so unfortunately its not that.

    Thanks,
    Andreas
     
  4. Anlu

    Anlu New
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    Here is also a video which documents the behaviour:



    First 100% speed with the sound after 2/3 of the lenght, than 50% of the speed with no noise
     
  5. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    If you move your ear around can you locate the source of the noise? Sounds less like the carriage and more like resonance in the frame and something loose rattling?
     
  6. Anlu

    Anlu New
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    Yes it comes from the gantry plate, i think it starts to vibrate the more it gets to the endpoint. I thought so too with the frame but i removed the actuator and its still the same.

    Do you have experience with lubricating? Tried to lubricate the wheels with silicone grease but didnt improve. I think it has to do with resonance since its always a bit different with different speeds over the 50% max.
     
  7. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    The wheels should never be lubricated (certain oils can even damage the plastics).

    We've never seen the carriage itself have vibration noise though, so not to sure on that one. A little more elimination/inspection may be helpful. Check your wheels were all properly assembled with the precision shim inside, check wheels for damage/flat spots formed from overly tight eccentrics/etc, check eccentric adjustment, etc. A little more auditory investigation too - there is nothing "loose" on a carriage assembly that could cause the vibration noises
     
  8. Anlu

    Anlu New
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    Thanks, thats what i also thought but needed to try to exclude this :)

    And also thanks for your suggestions, in fact the precision shim inside was missing but it also didn´t bring the effect.

    But, I think i might have found the issue and it´s not mechanical after all it seems: I am using the TMC5160 to drive the actuators and after disabling the stealthChop mode the behaviour doesn´t appear anymore. Of course now the motor is louder again but you can clearly hear that it moves correctly through all speeds and no mechanical noises anymore.

    I will investigate there since there seem to be automatic adjustments of the current while speeding, we'll see..

    Anyway, thank you very much for your fast and very helpful reply, greatly appreciated!

    Best,
    Andreas
     
    Peter Van Der Walt likes this.

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