Play in lead screw nut

Discussion in 'Calibration, Help, and Troubleshooting' started by Stian Indal Haugseth, May 28, 2016.

  1. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    I did not have any lithium grease so after some googling I decided to try dry PTFE lube. Did not help. It still squeaks and now I also got a rattling lead screw. It starts to vibrate when I lower/raise the bed. Investigating further I noticed there is a bit of play in the lead screw nut. I can wiggle the screw in the nut on one side. This can not be normal? And my phone suddenly refuses to record video!

    Going to clean the screws and get some grease. But I'm thinking to get the screws replaced.
     
  2. Alex9779

    Alex9779 Moderator
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    This IS normal at least for the nuts and lead screws we have...
    At first is was worried too, but thinking about it I am glad about the play. The lead screws are not really straight. Watch anybody's videos, you can see it in RichRaps time lapses too, the lead screw is wiggling left and right. The play in the nut prevents too much of that motion to go into the bed and so the print.
    Remember our bed is fixed in the four corners, the rods are really stiff, and that play in the nut does nothing, the lead screw has always contact with its upper thread pitch to the lower one of the nut because of gravity, the pitch has to be right to get a good layers and for me it seems the pitch is ok...
     
  3. Ephemeris

    Ephemeris Well-Known Member

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    Since it is not an anti-backlash nut, some play is expected. E3Dis depending on accurate alignment of the four smooth rods such that gravity is sufficient to keep the backlash at bay. In other words, the the top side of the lead screw is always in contact with the bottom side of the nut thread.

    Some suggestions:

    Pull the rods and check them for straightness.

    Check the nuts on the lead screws by hand for smoothness of motion

    Put the lead screws next to each other and carefully verify they are REALLY the same pitch. The threads should stay in the same phase relative to each other all the way along their length. This sounds a little crazy but I recently received four lead screws from the same vendor. Thrre screws matched each other, and the fourth was a subtly different pitch.

    Go through the tramming procedure again.

    Good luck!
     
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  4. Dr Jeep

    Dr Jeep Well-Known Member

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    I checked my leadscrews for straightness and my conclusion is that they are pretty straight. What causes them to look bent I think is the coupling. That clamp design is always going to clamp slightly off centre if the diameter of the thing you are clamping is less than the hole in the clamp and as you tighten them they naturally torque themselves slightly skew on the thread (no matter how hard you try to hold them straight).

    I've found some steppers with threaded rod as part of the shaft...not particularly cheap but I would consider it as soon as I thought the wobble in those screws was causing quality issues as if you have everything trammed up the flexi coupling shouldn't be required.
     
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  5. Alex9779

    Alex9779 Moderator
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    I wanted to do a test with a dial gauge to measure the right left movement of the bed. The problem is that I have nothing at the moment to mount my gauge and you also would need some flat surface mounted on the bed. Better it would be to mount he dial gauge to the bed and a flat iron fixed to the case. The problem is you have to align the plate to the rods. Then you could measure how much the bed is moving left and right which may be caused by the lead screws.
    But the experiment is not easy to do...
     
  6. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    I agree with the reasoning here. It should be of minimum impact. And a little play would help in minimizing any z banding from a offset or skewed screw.

    The only problem could be vertical play but my bed is very smooth and I believe gravity should do it's job yes :)

    Thanks guys!
     
  7. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    Hmm.. all I could find yesterday was some moly grease in my garage. Some charcoal gray gunk not very beautiful to look at and messy as h.... But it did the trick in getting rid of the squeaking and rattling / vibrating / oscillating lead screw.

    I would not put this on the smooth rods as it would look too ugly and ruin the nice metallic reflections from the LED lights :D
     
  8. Alex9779

    Alex9779 Moderator
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    Every great will look ugly, I used white lithium great which turned dark grey, last week I cleaned them in the process of rebuilding the whole motion system and reapplied it, no it is light gray...
     
  9. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    Light gray lithium grease you say :D Anyways it should look better than moly grease. Thinking on the kids messing about and smears black all over. Not a great WAF.

    PS. Think you should have a great chat with your autocorrect :rolleyes:
     
  10. Dr Jeep

    Dr Jeep Well-Known Member

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    Not sure about moly to lithium or PTFE to moly, but you do also have to be a bit careful when mixing greases. Particularly when you have something like the linear bearings which are impossible to clean out properly. Some lubricants are incompatible and bind together to form a sort of sticky mucus.

    So I'd be careful about changing your mind on that moly grease later on, or even jumping between things like PTFE and moly.

    For the leadscrew I'd clean everything (including the inside of the nut) very well before changing, for the linear bearings I think the best approach is to just stick to whatever lubricant you used first.

    I used to service large format (A0) printers and I saw a customer almost write one off once using an aerosol oil/cleaner (not WD-40 but something similar) to stop a squeaking noise. Whatever it was it turned the lithium based product inside the printer into glue. :D
     
  11. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    I fully agree. I only used moly on the lead screws on top of dry PTFE. There should not be much other chemicals than PTFE powder on the lead screws. I would take it all apart for proper cleaning before using any other lube.

    I would be careful of the linear bearings. They have only thin "ball bearing oil" in/on them at the moment and I'm looking for a proper agent to de-grease them before applying anything else on them. I'm discussing some of this here: https://forum.e3d-online.com/index.php?threads/tips-for-replacing-bearings.1441/
     
  12. Alex9779

    Alex9779 Moderator
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    Hehe seems so... :D
     

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