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Large printer - lead screw and anti BL concerns

Discussion in 'General Talk' started by Zeuligan, Feb 1, 2019.

  1. Zeuligan

    Zeuligan New
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    Hi, I'm currently planning my first dyi 3D printer and got tons of stuff to sort, but one thing that I keep coming back to is the lead screw and BL nut. I hope someone could help me.
    The printer is going to be large, 500x500x500 active printing area - atleast. With a bed of prob closer to 600x600 in aluminium. All high quality rails. Basically quite heavy.

    I got recommended to go with a 10mm 2mm lead acme lead screw for Z, but to my question/concern. I can't find a block type anti backlash nut for 10mm (like the one for 8mm in here) and need that for the type of design I'm thinking.

    Will it be smarter to scale down and go with 8mm screws to get access to standard blocks and parts or just make my own nuts? Cheaper, but strong enough?

    Everything on the machine will be milled or laser cut, so no printed parts.
     
  2. Rob Taylor

    Rob Taylor Journeyman
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    Get two nuts, put a spring between them and hold them together with enough slop to move back and forth a few millimeters. Boom, anti-backlash nut. Unless you mean "block-type" is the limitation, in which case you just need a metal cube with a hole through it, really. Easy enough to machine.

    You're unlikely to see problems with an 8mm screw over just a couple of feet under proper tension, but 10mm makes sense if you're planning on accelerating hard and want to absolutely minimise whip.
     
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  3. Zeuligan

    Zeuligan New
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    Yeah, I ment a Anti-backlash nut block, Open build style, but for a TR10X2 Trapezoidal lead screw. Just cad and machine one then after the open build design? I need a flat block design, rather than the big round anti back-lash nuts with springs you can buy.
    XY-cube design is the thought so want speed and accuracy. Thats whey I ended up with the choice of 10mm screw and 23 nema.

    Thx for your reply to my unworthy question :)
     
  4. Rob Taylor

    Rob Taylor Journeyman
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    If you have the capacity to turn an internal trapezoidal thread (or tap one in a drilled hole, probably easier for multi-start unless you have a CNC lathe with a servo spindle) you can make the OB-style nut.

    All it technically requires is two sections of internal trapezoidal thread, a living hinge mechanism- the metal "U" shape to connect them, and a tapped and untapped hole for a screw to tension the two arms together. Then something perpendicular to allow it to fasten to the moving platform. It's an incredibly simple design, you could weld a pair of McMaster-Carr ACME nuts together with a steel U-bracket and get good results with some care.

    Personally for speed and accuracy I'd just grab some 12mm ballscrews. They're stupid cheap these days.
     
  5. Giarc

    Giarc Master
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    It is easy to make your own tap out of a piece of the screw. Then, drill out the 8mm Openbuilds AB nut and re- tap it. Or do like I did and buy a chunck of delrin and make your own from scratch. I think modding an OB AB nut would be quicker and easier, though.
     

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