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replacement of lead screw

Discussion in 'Concepts and Ideas' started by Ester, Feb 28, 2018.

  1. Ester

    Ester Well-Known
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    Hi guys,
    I just incorporated the C-beam actuator in a microscopy setup and was wondering if I can in some way increase the accuracy of the positioning. The accuracy does more or less correspond to the testing data provided but sadly that is not precise enough for my needs.
    I was thinking of trying to improve the positioning by replacing the 8mm metric acme lead screw with a different one that has a smaller pitch.
    Do you see any problems I could encounter?
     
  2. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    The only issue with using a less aggressive lead screw comes in finding a decent anti-backlash nut that works with the C-beam system. Ultimately you may wind up having to make it yourself (which is not really a big deal). Other options to increase the accuracy include swapping out the stepper with a 0.9 degree, 400 steps/rotation stepper or using a reduction belt and reducing pulleys.
     
  3. Gary Caruso

    Gary Caruso OpenBuilds Team
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    Oh come on, you can’t just go and say “microscopy setup” and not give some details or pics!
    I know of a place on alibaba that has open build compatable tr8*2 and tr8*4 screws and anti-backlash nuts...
     
  4. Giarc

    Giarc Master
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    I just made a 5/16"-18 Lead screw - available cheap at most hardware stores - for my lazer Z axis (1.4111 mm/rotation). Basically my goal was to build it out of scrap and things I had leftover from other projects. I cut it to length then, using a cutting wheel in my angle grinder I made a tap out of the left over. It took all of about 5 minutes. I filmed the process, but have not edited or uploaded it to the web. I was going to incorporate it in my laser build log that I haven't got around to yet. Anti-backlash nuts are easy to make, but not worth it unless, like me you need it for a specific screw and they are not readily available. I used Delrin for my CNC router for both the 1/2"-10 five start screws, and 3/8"-8 four start (https://openbuilds.com/builds/lead-screw-driven-ox-derivative-850x1500.3307/). You could use HDPE which you can find in the scrap bin at your local Tap Plastics, or in the kitchen in the form of a plastic cutting board. I used a drill press and a scroll saw to make the nuts.
     
  5. Giarc

    Giarc Master
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    Another nice thing about the 5/16"-18, besides the accessibility and cheap price, is that it works with the 8mm shaft coupler and the 8mm bearings since it is 7.9375mm in diameter. Also, I agree with Gary, "you can’t just go and say “microscopy setup” and not give some details or pics! "
     
  6. Ester

    Ester Well-Known
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    Hi guys, thanks for the tips!
    I think I am going to use an M8 lead screw which should work fine with the shaft coupler aswell. I`m afraid I won`t be able to avoid making the backlash-nut, but i guess I´ll manage. About the "microscopy setup": it does sound much more fancy than it actually is and it is super rough at the moment. I will give you some more details once it actually works, but don`t expect too much, ok!?
     
    GrayUK likes this.
  7. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    No big deal, just a couple of M8 nuts with a compression spring in between. I'd probably go with a coupling nut for one of them just to have a length to grip. A housing to hold them could easily be 3D printed.
     

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