Using Load Detection for Belt Tension Testing

  • I was wondering if it would be possible to use the motor load detection in some way to run a quick test to determine if any belt is worn out or loose, if a drive gear is spinning on it's shaft a little and overall slop in an axis prior to printing, especially really long prints?

    The idea is that if you ran an axis at a set speed over a given distance and stopped it suddenly, a loose belt would dissipate more energy than a tighter one requiring less from the stepper to hold a stopped position and not cog over. My big assumption is that the steppers only use as much as they need to hold a position so if that's not the case maybe this wouldn't do much.

    If it could work, once you are getting excellent quality prints, you could set values for starting position, distance, speed, "out of spec" tolerance, etc. for each axis and run the test but have it remember that value for that axis. When run after that, it would compare the results against set "good" value and if it is out of spec, it tells you that something requires your attention, otherwise it's business as usual. There may be a more elegant way to accomplish this, but this is the best I could come up with lol

    Anyways, hopefully this could work and provide an easier way to test our printer hardware to know if maintenance is required. Could be a test that is performed at startup and display a message about which, if any axis are out of spec. I'm not an engineer so I look forward to hearing from people who actually know what they are doing 😛

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    It sounds to me that it might be possible, but I think it would depend a lot on the machine, and likely need a lot of experiments to test it. Bear in mind that load sensing only happens at a rate of once per full step.

  • @dc42 As far as I know Prusa does this on their MK3 model. They implemented a self-test for this purpose. The controller displays a decimal value and the manual provides a range in between the "tension is considered good". Of course that exact value depends on a specific machine, plus there still is the issue that all mechanical components are influencing each other on each axis. So either a bad bearing or a stuck linear guide should show up.