Z-axis old vs new threaded rods and nut.

Discussion in 'Build Help' started by EpicFail, Aug 7, 2017.

  1. EpicFail

    EpicFail Active Member

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    I wasnt aware that I had the original zaxis rods, and I was curious if the move to a taller pitch was to help remove some of the z-axis banding im seeing due to settling issues ? Is it worth the time and effort to do a quick swap out and re-factoring of zsteps?
     
  2. Old_Tafr

    Old_Tafr Well-Known Member

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    Worth a look at the Kickstarter update on the BB at the time of shipping where they discuss the tolerance of the Z-Axis smooth rods and the bearings, maybe not directly relevant to changing the threaded rods but good background as these tolerances and the movement of the bed due to stiction may also have some effect on banding.

    Plenty of grease during printing, including packing the bearings with grease during initial assembly, plus on the threaded rods helps too.
     
  3. Ephemeris

    Ephemeris Well-Known Member

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    I believe the banding is mostly a function of the straightness of the leadscrews. Some are not so good, some are bad, a few are pretty good.

    For most of us the easiest way to test them is to clean them, lay them on a glass table, and give them a gentle push so they roll several inches. If it rolls smoothly you've won the lead screw lottery! I've never had that luck but I have bought a couple that are okay. Most were not good, making a clack-a- clack-a-clack-a sound as they roll and then stop prematurely rocking back and forth on a bowed area.

    As for the switch to Tr8x8 lead screws, I'm against it. It degrades your vertical resolution and requires four times as much torque to move the Z-platform as the original Tr8x2 lead screws. Given that many BigBoxes had problems with the couplers slipping occasionally, I have to believe putting four times (4x) the torque on them can only make the problem more likely.

    Yes I know the Tr8x8 can move the bed faster, but I don't see that as any sort of practical advantage.
     
    #3 Ephemeris, Aug 7, 2017
    Last edited: Aug 7, 2017
  4. EpicFail

    EpicFail Active Member

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    Hmm, yeah I remember a post way back when they talked about rods that didnt fit correctly and they had to wait for a new batch? I dont remmeber one about the lead screws, so Ill have to track that down.

    Otherwise, I was looking at getting some spring loaded backlash nuts to replace the current ones. The sliding on one layer seemed... odd.. Almost like the nozzle pitched to the side?

    There probably needed to be a better solution for locking that thing in as well :|

    I'll go back to printing benchmark objects and see if I can get photos to illustrate my problems.

    Otherwise, I would like to point out its often just very subtle issues, but for the most part I think would be acceptable to many.
     
  5. R Design

    R Design Well-Known Member

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    The development to wait for in this domain are the lead screws integrated in stepper motors (the lead screw IS the shaft of the motor so no couplers required) that have been ordered as swap in replacement so for the BigBox by Greg. THAT improves print quality. However don't know what pitch has been selected for these?
     
  6. Greg Holloway

    Greg Holloway Administrator
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    They are 8mm, 4-start. Basically identical to the later batch of BB supplied leadscrews.

    Of all of the mods I have done to the BB adding the integrated leadscrew steppers has had by far the best effect on print quality. Combine that with the silentstepsticks and the machine prints flawlessly.
     
    Stian Indal Haugseth likes this.

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