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  1. #1
    Join Date
    Jul 2019

    6090 CNC experiencing friction and shakiness - noob help!

    Hey guys! Fairly new to CNC and first time posting on here so let me know if I'm missing important details at all. Been experiencing some issues with a 60x90 CNC I bought second hand. First off - I believe the problem may stem from breaking some router bits in the learning process - so I'm fairly certain its mechanical and not software based.

    Basically, I was having an issue where on the Y-Axis, the CNC would get stuck at certain points and make a loud grinding/stalling noise - which would result in that specific Y-Axis run stalling, the home being lost, and the whole rest of the cut being out of line. I thought it might be the stepper motor stalling, so I took the bed apart so I could get a closer look at the rollers as the machine runs along them.

    I noticed that the gantry arms were slightly out of line, so I went through and re-adjusted everything and lined it all up properly, and re-tightened everything, however I'm still having the same problem during runs - even without cutting and just moving through the air.

    Right now the main diagnosable problems I can see are:

    - There's a lot of grinding/friction noise as the machine travels along the Y-Axis, specifically from around y300-y400 there is a heavy grinding noise, and the left stepper motor only seems to stall/get stuck in this area. The grinding noise is most apparent when the machine slows down to stop, and stalling/getting stuck seems to happen most often when the machine slows and then tries to speed up again.

    - This grinding results in the machine shaking heavily as it moves up and down the y-axis, even without cutting, meaning any cuts will be inaccurate and choppy.

    X and Z Axis both seem to be running smoothly.

    Any help would be greatly appreciated

    Thanks very much guys!

  2. #2
    Join Date
    Sep 2005

    Re: 6090 CNC experiencing friction and shakiness - noob help!

    Disconnect the motors by removing the couplings or belt whatever apply and move the carriage by hand, or whatever is binding. Check for bad bearings or more than likely just out of alinement issues. Correct as needed. Test before committing to a real job.
    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router

  3. #3
    Gold Member
    Join Date
    Apr 2004

    Re: 6090 CNC experiencing friction and shakiness - noob help!

    If you follow wmgeorge's directions and can't find any binding or other mechanical issues, try swapping the cables feeding Y with those feeding X, then power the system back up and see if the Y axis behaves the same way or if the problem follows the cables. If the X axis starts misbehaving, it's either a bad cable, a bad driver, or a bad connection.
    Andrew Werby

  4. #4
    Join Date
    Jul 2019

    Re: 6090 CNC experiencing friction and shakiness - noob help!

    Thanks for the tips guys! I've pulled it apart to check and there seems to be 2 problems which must be causing the problem:

    1. The threads on the end brackets that connect the stepper motors are worn out as they were tapped in Alloy, causing there to be increased resonance on the stepper motors which would definitely be contributing to stalling
    2. There is a lot of resistance on the left roller as I push the gantry arms along by hand.

    I'm going to get new bracket bits made, I've tried re-tapping and using thread tape and it doesn't seem to hold tight enough to last. However, I can't seem to find the cause of the resistance on the left roller as I manually push it along. From the outside everything looks alright, but there is definitely some drag on that side as I try to roll it compared to the other side. Any tips for diagnosing specifically which component is buggered? Also, could it be something as simple as the roller arms needing to be greased or something?

    Thanks a lot guys! Really appreciate it

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