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Nema 23's making very loud noise after T8 screw upgrade

Discussion in 'Motors' started by ScottKruer, May 12, 2019.

  1. ScottKruer

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    Hi All,

    I purchased an X-carve back in December 2016. I eventually upgraded the Z axis to an 8" screw drive. After which, I upgraded the belts to larger. During all of this, I never had any issue with the stepper motors making any noise.

    I recently upgraded the X and Y axis to screw drives (replacing the belts) using the kit from MFXWORKSHOP. I decided to try and ask my question here since the screw drives actually came from OpenBuilds.

    After following the setup directions for the hardware, I started on the electronics. While using the belts on the original configuration of the X-carve, it was set at 1/8 micro-stepping for the X & Y axis. The screw drive setup said to go with full step. I opted to go with 1/2 step (hoping for a comfortable balance between speed and accuracy. All 3 axis' set the same. I powered it on and homed.... I noticed a loud noise as the steppers started to move and then just a harmonic whine as they were spinning. I then heard the same noise when they came to a stop. So, I jogged each axis out 800mm and back. Same thing, noise while starting and stopping and just a whine while moving. I then went out to X=800mm and Y=800mm and set G30... I went back to home and set G28. Going back and forth between each of the locations at rapid speed, I still experienced the same thing. I probably wouldn't have given this too much thought except that the noise while starting and stopping was very loud.

    I created a project in Easel that would utilize an 800mm x 800mm workspace. I then added some various shapes that would normally be carved (I only wanted to move the machine around so I didn't lower the spindle to the surface or turn it on). When I sent the gcode to the machine using UGS and it started moving around, rapidly changing direction, I thought the machine was going to fly apart. The steppers were making all kinds of noise and shaking.

    The next thing I tried was to change the step to full as suggested in the setup guide. It was even worse!!!

    I've come across various suggestions for increasing the steps which, after changing from 1/2 to full and it getting worse, kinda makes sense to try 1/8. But, I thought I might ask here first, hoping someone knows the ends and outs of the steppers (Nema 23's), the g-shield that the X-controller uses and using the T8 screws.

    Thanks in advance,
    Scott
     
  2. Christian James

    Christian James Well-Known
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    I would have started with 1/8 steps.
     
  3. Alex Chambers

    Alex Chambers Master
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    Welcome to the forum @ScotKruer. I am not very familiar with your setup, but do have a leadscrew machine. Have you eliminated mechanical issues? - especially adjustments of anti backlash nuts? On a new setup the anti backlash nuts will be tight on the leadscrew and need little adjustment. They also need lubrication with a DRY lubricant - PTFE or silicone - don't use oil (dust sticks to it - and WD40 is not a lubricant - they do a dry spray which is).
    May not solve your problems but worth checking (you may have already done this).
    I'll leave advice on the electronics and control issues to someone familiar with your setup.
    Good luck! Alex.
     
  4. ScottKruer

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    Thanks for the reply Alex. I do have an anti-backlash on my cncnewbies Z axis linear slide but, it has been operating perfectly for over a year. The X & Y axis' utilize an anti-backlash nut block (as shown here Transmission - Lead Screws & Nut Blocks - OpenBuilds Part Store). All screws have been coated with 3-in-one all-temp silicone. As per Christian's suggestion, I changed the micro-stepping to 1/8 and the "end of the world" noise I was experiencing all but went away.

    I guess I'm just not really clear on the micro-stepping. I thought I had a pretty good handle on it. As I understood it, the Nema 23's will step 200 times for a single revolution... moving 1.8 degrees for each step. And my understanding of the T8 screw is that, with a 2mm pitch, it would move the nut-block 2mm for every rotation of the screw. So, using FULL steps:

    1000 steps = 5 revolutions of the T8 screw = 10mm of nut-block movement <--- correct??

    And using 1/2 steps:

    1000 steps times 1/2 micro-stepping = 2.5 revolutions of the T8 screw = 5mm of nut-block movement <--- still correct??


    So, why is it that the stepper motors make so much noise when spinning less times?

    Scott
     
  5. Gary Caruso

    Gary Caruso OpenBuilds Team
    Staff Member Moderator Builder

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    The TR8*8 is 2mm pitch but moves 8mm each turn.. it's 8mm lead (the ones Openbuilds sells).
    With half step it will be quite rough sounding, typically 1/8 steps are used for smoothness, that will get you 1600 steps per turn or about 200 steps per mm.
    Cheers
    Gary
     
    Nick Jones likes this.
  6. ScottKruer

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    That’s a heck of a lightbulb that just flipped on... so, using my original FULL step scenario, the 1000 steps would still rotate the screw 5 times but, instead of moving a 10mm distance, it would move it 40mm’s... Sounds like all the noise the stepper motors are making is them screaming “I ain’t no **** servo”... Thanks very much for educating me on this!!!
     

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