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1/2-10 Nut block - Backlash Compensation?

Discussion in 'CNC Mills/Routers' started by drxlcarfreak, Jun 6, 2017.

  1. drxlcarfreak

    drxlcarfreak Journeyman
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    I am working on a design for a 1500mm lead screw axis. Looking through other threads I found that a 1/2" lead screw should be sufficient for my length. I also found a link to this nut block for a 5 start 1/2" acme rod: 1/2-10 ACME DELRIN NUT BLOCK RH for acme threaded rod 5-start CNC 3d printer

    It does not have any anti-backlash compensation provisions in it. Is there an easy/tight/cheap way to add anti-backlash to it? I am trying to tuck it into a C beam as well, otherwise I would just use this one (I actually had planned to use this one and cut down the ears to clear the beam): 5 Start High Load Anti-Backlash Acme Nut - CRP162-00 | CNCRouterParts

    Thanks!
     
  2. Giarc

    Giarc Master
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    You could buy two of them for each screw and use the 1/4-20 holes to take out the slop between them. Mount one set to your Y axis plates in a slot. Or just leave the second free floating. If you are cheap like me, you would buy 3 total and cut one in half for the part that takes out the backlash and fasten it free floating to the mounted one as I mentioned above.
     
  3. Giarc

    Giarc Master
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    Better yet, one per axis and cut a slot in one side past the 1/2 - 10 hole and just put a 1/4 20 bolt in one side running parallel with the 1/2 - 10. ream one side of the slot with a 1/4 inch bit so that the bolt slides in then tighten the bolt to remove the backlash. The slot does not have to be very wide. The kerf of a saw blade should be enough, I suspect. Similar to the open builds nuts.
    [​IMG]

    These would have been handy when I built mine. I had to make my own.
     
  4. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    You might check with dumpsterCNC. They are currently down due to a tornado but should be up and running shortly.
     
  5. drxlcarfreak

    drxlcarfreak Journeyman
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    Wow, thanks guys! All very simple and making me smack my head and wonder why I didn't think of that myself!

    One question about the spring idea. What is the purpose of that over just using bolts to tighten the backlash, automatic compensation during wear? And a followup question, where would I get such a spring, I guess mainly what is the optimal spring coefficient that would work for this setup?
     
  6. drxlcarfreak

    drxlcarfreak Journeyman
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    Haha, fair enough. My typical MO is to go overkill or overbuild, so I will have to keep in mind its just a plastic piece, not an engine component!
     
    Tomias likes this.
  7. drxlcarfreak

    drxlcarfreak Journeyman
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    Oh, nice. Put a spring on each bolt instead of around the lead screw. That would work very well!

    Speaking of my overkill, Giarc, I noticed on your build that your model bolted your Nema 23 motors down with all four mounting bolts, but the pictures I saw of your actual build only used 2 bolts (I am guessing the bolts clashed with the X rails and couldn't be accessed from the back?). Is two mounting bolts enough to keep the motor from torquing out of position, or did you go back later and add the 3rd and/or 4th bolt?
     
  8. Giarc

    Giarc Master
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    Two bolts are enough. I made it so I could mount the four, and I did use them when I first assembled it, but they were a pain to access and tighten. I had to fasten the motor to the plate first, then the plate to the frame (the Z is still like that). When I reassembled for the final set-up I skipped the two that were hard to manipulate because I had all the plates on, everything nice and square before I realized the my mistake in not mounting the motors first. If you noticed there were a lot of bolts and t- nuts to line up. I didn't want to have to take it all apart again when I saw so many other c-beam builds only using two. I can not tell the difference in the machine's functionality. The bolts will clash unless you pocket out where the bolt head is located.
     
  9. drxlcarfreak

    drxlcarfreak Journeyman
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    Awesome, good to know! I hopefully will have a model ready enough for upload as a build diary in the next week or so with all your guys input!
     
    Giarc likes this.

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