Optimum Layer Height(s)

Discussion in 'Calibration, Help, and Troubleshooting' started by Jasons_BigBox, Jan 20, 2019.

  1. Jasons_BigBox

    Jasons_BigBox Well-Known Member

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    Happy New Year Everyone!

    (and long time no see!)


    I'm sure I've read somewhere that there's an optimum layer height for your machine configuration based on z-axis screw thread pitch and stepper resolutions. The problem is, I can't seem to find the information here!

    Can anyone explain how to do it or point me in the right direction?

    Thanks


    Jason
     
  2. dc42

    dc42 Well-Known Member

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    It's often said that it's best to choose a layer height that is an exact number of full steps of the Z motor.
     
  3. Ephemeris

    Ephemeris Well-Known Member

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    Ideally you want the layer thickness to correspond to an integral number of stepper steps. If you have the original BigBox kit that came with Tr8x2 leadscrews and the Wantai 42BYGHW609 1.8 degree steppers you can calculate it this way:

    Steps per revolution 200 (i.e.1.8 degree steps)
    Z mm per revolution 2 (I think the last few kits had the unfortunate Tr8x8(P2) that move 8mm / rev)

    So a single Z-stepper step moves the build platform 2mm/(200 steps) = 0.01 mm/step
    That means pretty much any round number layer height (i.e., 0.4, 0.3, 0.25, 0.2, 0.1, 0.05, etc) all work out perfectly


    If you have those Tr8x8(P2) leadscrews your vertical step is larger

    So a single Z-stepper step moves the build platform 8mm/(200 steps) = 0.04 mm/step
    In which case fewer round number layer heights (i.e., 0.4, 0.2, etc) work out perfectly

    How practical is this as a concern? Assuming 16x microstepping, that Tr8x8(P2) could be commanded to all the round numbers the Tr8x2 can do using full steps. The microsteps are less accurate than the full steps so layer height consistency would be slightly effected. Worst case would be if you picked a layer height that doesn't even equal an integral number of microsteps. That would cause the layer thickness to dither between integral microstep numbers which might generate a visible artifact on some prints.

    Looking at the numbers for the BigBox this seems more theoretical than practical since the microsteps give pretty fine resolution. Still, I have heard of such things being an issue on other printers.
     
    mhe likes this.
  4. jfb

    jfb Well-Known Member

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    The only other factor is that the layer height needs to be less than your nozzle width. Prusa I think recommend 80% of nozzle size as the maximum layer height and I've seen that number in a few other places.
     
  5. Jasons_BigBox

    Jasons_BigBox Well-Known Member

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    Thanks everyone, good info there!

    I’m just going back to basics again on my Simplify setups. I think over time I’ve tweaked things here and there that have snowballed into, well, not quite perfect.

    I’m still getting good prints, just backtracking a bit to see if they can be better.

    Cheers!


    Jason
     

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