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Workbee z axis lead screw preload ?

Discussion in 'CNC Mills/Routers' started by WR_Rider, Apr 23, 2019.

  1. WR_Rider

    WR_Rider Journeyman
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    I was installing the z axis lead screw and while everything appears square there seems to be some lateral preload on the lead screw bearings. Facing the spindle mount as I try to push the bearings into the recesses both bearings have to be pushed into the recessed in the same direction. It is like the preloaded block is off center but it appears centered.

    FYI, the lead screw hasn't yet been pushed into the motor drive coupler and the preloaded block adjustment bolt was installed just before making contact to set the pressure.

    So my question is this seem normal? I'm worried about wearing out the bearings and undo strain on the motors. I was thinking of shifting the preload block.

    Thanks
     
  2. Alex Chambers

    Alex Chambers Openbuilds Team
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    I assume you mean the black anti-backlash nut? I would loosen the screws holding it, install the leadscrew, then re-tighten the fixing screws. Did you run the leadscrew back and forth through the anti-backlash nut a few times? They are often tight when new.
    Alex.
     
  3. WR_Rider

    WR_Rider Journeyman
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    Correct, it is the "anti backlash" block, not a "preload" block.

    When I put the block on it didn't seem to have any way of adjusting any "play" / positioning of it so I just tightened it down. I have only turned the lead screw by hand and while it moves I do worry about the bearings having side load on them and wearing out, all though you might have a point that the block might "wear" in a bit.

    I think I will probably dissemble the 2 plates / assembly so I can loosen the block to reposition it. I'm not "keen" on having that lead screw positioned with a slight bend in it.

    Thanks! I do appreciate the input.
     
  4. Alex Chambers

    Alex Chambers Openbuilds Team
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    Sorry, I'd forgotten you can't get at those screws after fixing the Z plate to the X gantry. :(
    Alex. :banghead:
     
  5. WR_Rider

    WR_Rider Journeyman
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    Maybe that would be a nice "mod" to the original design. Have 2 slightly larger holes in the middle plate so one can access those 2 bolt heads from the back.

    However it sounds like we are in agreement that there really shouldn't be any side load on the lead screw so I will disassemble and adjust. Easier to fix now.

    Thanks again! Have a great week!
     
    Alex Chambers likes this.

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