Linear Movement innacurate

  • I just finished wiring and calibrating my duet wifi and linear movement is inaccurate. I have GT2 belts with 16 tooth gears and pulleys. Z axis is an M8x8 lead screw. With 32 Microstepping I have it set at X200, Y200. Z800 Step/mm. However when I rapid move the X and Y-axis 100mm it grossly overshoots that by about 15-20mm. I havent't tried pringint anything yet since this is so far off. Does anyone have a clue as to why this is so inaccurate? I've triple checked all my mechanical components and everything is entered correctly, belts are tight etc. Please help.


  • In my opinion 160 steps / mm is the correct value

  • @printermakerdude We might be better able to advise if you supply a little more information. It sounds like a configuration issue so posting your configuration files (config.g) would be a good start. Also, let us know a little bit about the motors - specifically if they are 1.8 degree/200 steps per revolution or 0.9 degree, 400 steps per revolution.

  • Well, now I screwed up and hit the erase button meaning to hit the Reset. So while I figure that out and how to get connected again here is my config file.

    Motors are 1.8 degree/200 steps per revolution


  • administrators

    @printermakerdude said in Linear Movement innacurate:

    Well, now I screwed up and hit the erase button meaning to hit the Reset.

    Sounds like you are running an older version of the Duet (the current version doesn't have an Erase button). Is it a clone? Or acquired second hand?

    Motors are 1.8 degree/200 steps per revolution


    M350 X256 Y256 Z256 E16 I0 ; configure microstepping without interpolation
    M92 X1600.00 Y1600.00 Z6400.00 E93.00 ; set steps per mm

    Using native x256 microstepping rarely makes sense, because the required step pulse rate is to high to get good speeds. Start with x16 microstepping with interpolation, and set your steps/mm to 200. When you have that working, experiment with higher non-interpolated microstepping if you wish.

  • @printermakerdude 16 tooth pulleys at 2mm pitch means 32mm movement in 1 revolution. 200 steps per revolution divided by 32mm means 6.25 full steps per revolution. Using 16x micro-stepping as David suggested means that you should use 100 (micro) steps per mm (6.25 full steps x 16). The 1600 you had for 256x was correct (but not recommended).

    Are you sure that you have 16 tooth pulleys? A more common size is 20 tooth and the difference between 16 teeth and 20 teeth is exactly the same as the overshoot in linear distance you measured.

  • administrators

    I've also seen 18-tooth pulleys.

  • @dc42 For sure. Our oriental friends use all sorts of different sizes. ☺

  • The config I had sent I now realize was the latest I tried with micro-stepping to experiment with noise. I prefer a little slower prints.

    It is absolutely 16 teeth. As I counted to make sure. but I'll try it at 20 teeth anyway.

    This is a refurbished controller board I got directly from Duet. The problem I am now having is it won't connect in YAT to get my wifi up and running. Any suggestions there?

  • administrators

    If you pressed the Erase button then you will need to reinstall the firmware using Bossa. See the wiki page on installing firmware.

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