Different lead/pitch for Z axis



  • Hi there,

    Right now I have T8*8 (8mm screw with 2mm pitch and 8mm lead). Is there any point to change it to 1mm pitch and 1mm lead? (Bought already and waiting 🙂 )

    And one more thing, right now my Z axis screw is integrated with stepper motor and if I want to change it - I will need to use another stepper + coupler.

    My point is to turn off microsteps and use full steps only. Right now each step is 0.04mm. And I am trying to make my 3D printer more precise and don't need high speeds.

    Thanks



  • @briskspirit will you be printing at less than 0.04 layer height?

    The lead screw integrated with the stepper is probably going to have less chance of z wobble than a coupled lead screw, but that's probably going to depend on the quality of it more than just what type it is.

    1mm lead and pitch will be much slower, but likely won't have as much backlash potential so will be more stable and resist wanting to autorotate when power is off.

    I wouldn't recommend using full steps. I don't think you'll gain anything noticeable and you will have much more noise and possibly run into some torque issues with such small z moves during printing.

    If you've already got some hardware on the way it can't hurt to experiment.


  • administrators

    My Ormerod has a 0.8mm pitch screw drive. It's slow but that isn't a big problem. I run it at x16 microstepping.



  • @dc42 What couplers do you use? or belt driven? Thanks



  • @briskspirit said in Different lead/pitch for Z axis:

    Hi there,

    Right now I have T8*8 (8mm screw with 2mm pitch and 8mm lead). Is there any point to change it to 1mm pitch and 1mm lead? (Bought already and waiting 🙂 )

    And one more thing, right now my Z axis screw is integrated with stepper motor and if I want to change it - I will need to use another stepper + coupler.

    My point is to turn off microsteps and use full steps only. Right now each step is 0.04mm. And I am trying to make my 3D printer more precise and don't need high speeds.

    Thanks

    My thoughts on Z axis screws are here. https://somei3deas.wordpress.com/2017/01/31/z-axis-lead-screws/
    Using micro stepping is fine but I would recommend that layer heights are multiples of full steps rather than relying on micro-stepping for positional accuracy. This can limit your options when using multi-start screws which have a course lead and you need a lot more torque to drive course screws.



  • I just bumped out my 0.8mm Z lead screws for T8x8 lead screws for my Z. the T8x8 are much quieter and allow faster movement, but the smaller pitch ones worked okay. I had them a little overdriven for the motors that I had, which did cause me some problems.

    I used printed couplers for those 0.8mm lead screws, and had some Z wobble issues with them, which was one reason for the switch, as I have several decent quality couplers for the T8x8, plus I already had all of the required hardware.



  • @supraguy Is it noticeably slower for printing 0.1-0.2 layer heights?



  • @briskspirit you'd only notice the speed difference when traveling which isn't often unless you home to z max.



  • @briskspirit If you do the maths, changing layers at say 5mm/sec^2 acceleration might take about 0.002 secs depending on layer height. If you increase the acceleration 10 fold to say 50mm/sec^2 then layer changes will take around 0.001 secs. So a 10 fold increase in Z axis acceleration will reduce print time by about 1 second for every 1,000 layers. As @Phaedrux said, it's only when homing that you might notice difference in speed.

    It's not quite as simple as that though. Because a screw with an 8mm lead will move a nut 8 times further than a screw with a 1mm lead in say 1 revolution. But the 8mm lead screw will need 8 times more torque to achieve that, so you might have to reduce the acceleration. And that is assuming that the motor is capable of producing the required torque.



  • @deckingman I have read your blog about screws and decided that I must to try to change my T8*8 to already ordered 1mm pitch/lead screw 🙂



  • @briskspirit said in Different lead/pitch for Z axis:

    @supraguy Is it noticeably slower for printing 0.1-0.2 layer heights?

    I'm sure that you'd never notice the speed. I left my maximum speed and acceleration settings the same, so there probably is no difference that way.

    What I do notice is that it's so much quieter, which is nice.


 

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