Z Axis Motor Rattle



  • Hi guys,

    Hoping someone can help me out…...

    I'm swapping the main board on my hypercube from Ramps to Duet Wifi. Is was going pretty well until I started going through a few checks. Everything works great with the exception of the Z stepper. When I try to move the bed I get a horrendous rattle/vibration. I've tried different combinations and it is definitely something to do with the board/config, I just cant figure out what it is.

    Any help would be greatly appreciated.

    Thanks in advance!!



  • Forgot to say….. was thinking it may have something to do with interpolation/microstepping but am unsure how to change these setting.

    thanks


  • administrators

    You can set the microstepping on the M350 command in config.g. See https://duet3d.com/wiki/G-code#M350:_Set_microstepping_mode.



  • If I wanted to get better torque from my z stepper what would you recommend setting wise???



  • It could be the speed and/or acceleration settings for your Z axis. If they are set too high, you'll get missed steps at best. What do you have for speed, jerk and acceleration for Z? Also, what is the lead for your screws (or pitch x number of starts)?

    Edit. I use a single Nema 17 driving 3 screws lifting a 10mm thick aluminium 400x400 bed so motor torque is unlikely to be an issue unless you bed is a lot heavier than mine.



  • For the lead screw 1 full turn is 8mm.
    Acceleration set to 100. Jerk I’ve got on 0.4.
    400 steps per unit



  • Those course screws could be the problem as you need a lot more torque than with a finer lead. However, try 20 for your acceleration (M201) and jerk (M566) settings and 300 for your maximum speed (M203).

    BTW, with that lead on your screws don't use layer heights that are uneven numbers. Assuming you are using 16X micro stepping, then 400 steps per mm equate to 25 full steps per mm so 0.1mm would be 2.5 full steps and therefore you would be relying on micro stepping for positional accuracy. A layer height of 0.2 mm would be 5 full steps which is OK but 0.3 mm would be 7.5 full steps which is not good whilst 0.4mm would be 10 full steps which again, is OK.

    Those multi start screws that many people think area good idea are one of my pet hates. Personally I'd ditch them and replace them with 0.2 or 0.1 mm lead single start screws which would cure all your problems as well as improving the positional accuracy. I did a little write up on my blog explaining why https://somei3deas.wordpress.com/2017/01/31/z-axis-lead-screws/


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