z axis catching on minor tension

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This topic contains 3 replies, has 2 voices, and was last updated by  Ryan 4 months, 3 weeks ago.

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  • #34381

    George
    Participant

    Hi everyone,
    First post here, been working on my mpcnc for about a year, learning and building slowly.
    first the basics of my problem:
    for the z axis( i haven’t test x or y as it hasn’t been happening there) there was this binding that would occur whenever I brought the feedrate up above around 180. it would fluctuate up and down a little but generally that was the point that I almost always had results. at first I accepted this, but it seems more and more that this will impede me. essentially what happens is there is a loud noise, and the z axis doesn’t move, despite being given a command.
    After switching out motors and drivers, I have found that for every motor it is the same. I run the command for a z movement with F522, through F180, and it works fine, but apply minor to major pressure, depending on the feedrate, and it catches and does not complete the movement. I have no idea at this point and would really appreciate some help.
    parts:
    ramps and power supply and motors from here.
    z driver is not from here, but the same thing was happening with the one from here.
    thats all I got but I must have overlooked something, so any ideas I would really love.

    #34395

    Ryan
    Keymaster

    So many things to try. The most common is build issues. Turn it off, and move it with your fingers by the pineapple coupler. It should be very easy and smooth if it is not that is the problem. I do suggest running it all the way up and down 1 full time with your fingers to check for irregularities.

    #34436

    George
    Participant

    Tried it, it moves smoothly enough, going to the store to grab some wd-40 just in case. I took out the motor and was just holding it as I ran the commands, and it had the same problem, at higher feedrates, I would simply grab the shaft and it would start to catch.
    I think it might be a problem with the drivers. would this be possible? I’ll probably order some more when my credit card comes back online.

    #34437

    Ryan
    Keymaster

    Smoothly is important but easily is more important. should feel very little resistance.

    If your driver is a drv8825 and my steppers the pot should be set to about 0.7V . I have not seen them fail and still work. Usually they just fail. You can swap any driver and see if it helps.

    So you say F522-F180 you are hand programming the gcode? It should run fine up to F510/max (8.4mm/s) it should be very strong up to F250. it should be able to rip itself out of it’s own feet if you hit the surface.

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