IN DEVELOPMENT z-axis ball screws

Discussion in 'Guides, Mods, and Upgrades' started by JesperJuul, Oct 25, 2016.

  1. JesperJuul

    JesperJuul Well-Known Member

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    Hi guys

    I needed two lead screws for a project, but instead of buying new ones i thought of using the rather bad (crocked) ones that came with my BigBox, and then upgrading the BigBox with a pair of 1204 nema-intergrated ball screws.

    Anyone has done it already or have any thoughts?
     
  2. A Dragon In A Pie Costume

    A Dragon In A Pie Costume Well-Known Member

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    first time im hearing about these, seems like a decent idea though
     
  3. PsyVision

    PsyVision Moderator
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    I saw those but wasn't sure I could get them in the length needed but I think RobotDigg (or whatever theyre called) did custom ones.

    I managed to sort my coupling such that it was tram but I think it's the way forward. Tom Salanderer thinks theyre good too
     
  4. JesperJuul

    JesperJuul Well-Known Member

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    I pulled the trigger, will be updating on arrival.
     
  5. Alex9779

    Alex9779 Moderator
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    IMHO ball screws are too much for the Z and not needed, gravity works for us.
    My Z screws have a lot of play in the nuts and still I have no issues with Z...
    Let me explain why.
    In XY direction the bed is guided by the four rods and bearings which are pretty solid compared to the forces you have in XY direction, theoretical nothing but if you screws are not straight then there might be a little but I think the rods are enough to keep the bed in place.
    In Z direction my screws have also play but this doesn't matter, that's where gravity does it's job. The bed is always forced downwards. So looking at the screw and nut always the lower part of the thread has contact, never, and I mean never ever, the upper part. No matter which direction you move the bed.
    Ball screws are great for horizontal movements when you don't wanna have backlash and need accurate positioning.
    In out case we have no backlash as long as we don't move the bed faster down than the inertia of the bed will keep it in place and I don't think we can move the bed that fast...
     
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  6. JesperJuul

    JesperJuul Well-Known Member

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    I get it Alex, but the case is that i have z-issues. I suspect it is the shitty bearings that "microsnag", but the ball screws wasn't that much more expensive than nema+coupler+leadscrew with nut, and since i needed two screws with steppers i thought what the hell - overengineering FTW!
     
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  7. Alex9779

    Alex9779 Moderator
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    :D LOL
    go for it. I am curious about the result...
     
  8. Jasons_BigBox

    Jasons_BigBox Well-Known Member

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    I agree, the z-screws should always be in compression due to the load from the bed. This means that any tolerances should close up.

    Bad bearings and/or poor rod alignment can cause the z to drag a bit. This would cause the screws to pull the bed down rather than hold it up if you know what I mean. Always worth double-checking how free the motion is without the screws.
     
  9. PsyVision

    PsyVision Moderator
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    I think Tom talks about them in this video:
    around 23 minutes in, because of the white benchy submitted. He's discussing them in relation to a Lulzbot Mini but essentially says they're a good idea. Although I think its more of integrated lead screw rather than integrated ball screw.
     
  10. eca

    eca Well-Known Member

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    And are theses just a simple swap? Does the nut just fit right in the hole and the screw holes line up, or will there be modification needed to the bed?
    I'm all for over-engineering things if it improves the function, reduces maintenance and looks cool doing it :p
     
  11. PsyVision

    PsyVision Moderator
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    Providing you can get one that has the correct length lead screw then I understand it is a straight swap.
     
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  12. eca

    eca Well-Known Member

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    He,he,he, so something I can quickly swap out so my wife doesn't notice me dismantling my BB again for another upgrade...
     
  13. Alex9779

    Alex9779 Moderator
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    Yeah those things are the best... Swapped my iPad2 to an iPad Pro and didn't use the Pencil for two weeks so she didn't notice... Swapped my iPhone 6S for an iPhone 7, same black case and she didn't notice until hers broke and I offered her my "old" :D :D :D
     
  14. R Design

    R Design Well-Known Member

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    It's 26 until 32 mins in.

    I'd definitely be interested in this integrated solution since it's this kind of band that is my only real print anomaly.

    Anyone know why the pitch of the lead screws changed between Kickstarter and 1.1 ?

    1.1 leadscrews are gentler (less steep, larger pitch...) and perhaps that at least reduces the number of bands that one can possibly get on a given print?
     
  15. PsyVision

    PsyVision Moderator
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    Hah I had to guess from the video alone as had no sound when I posted that :D

    The new ones are 8mm. I have them, switched out the 2mm ones. I had some banding until I got the couplers really tram with the 2mm ones. At the moment, my z wall is buttery smooth! How much of that is due to tram, 8mm or the lighter IDEX heads...
     
  16. R Design

    R Design Well-Known Member

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    Why did you switch to 8mm pitch? Did it make any difference?

    My banding is very very light (done plenty of tramming!) but I notice it since I only print in light and dark gray.

    Lighter IDEX heads + improved X rigidity from dual rods should improve side walls when printing at higher speeds. Methinks the original setup had quite a lot of slop. ;)

    There's quite a lot of detail on this page: https://www.pololu.com/product/2690
     
  17. PsyVision

    PsyVision Moderator
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    I switched for the hell of it to be honest!
     
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  18. JesperJuul

    JesperJuul Well-Known Member

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    This is totally my way of switching stuff :D
     
    #18 JesperJuul, Oct 29, 2016
    Last edited: Dec 25, 2016
  19. eca

    eca Well-Known Member

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    Well, if they can be found in the right length and at a decent price. I would probably also order some. My axis screws rotate noticeably. Even with tramming.
     
  20. R Design

    R Design Well-Known Member

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    The 8mm pitch would mean less turns / wobbles / lines per part. But on the other hand The steeper helix might produce more sideways pressure on the lead nuts than the shallow 2mm pitch. So one might imagine it could displace the bed further.

    Or perhaps the 8mm pitch rods were just "better quality"?
     

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