Another bad bearing

Discussion in 'Calibration, Help, and Troubleshooting' started by Henry feldman, Mar 5, 2016.

  1. Henry feldman

    Henry feldman Well-Known Member

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    Put the X-carriage on and what a horrible grinding sound on one side. So clearly a bad LM8LUU bearing (if I reverse the carriage it makes the sound on the other side, so not the rod, but the bearing. Not a big deal since they are cheap, but I have such limited time to work on this, this puts it off for days! I have noted a fairly high bearing failure rate in the postings here... frustrating...
     
  2. MikeP-NZ

    MikeP-NZ Member

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    It's more likely that the bearing has become contaminated with dirt, swarf or something.
    It doesn't take much to make them run rough.
    High quality bearings are assembled, greased and sealed in clean-room like conditions. Lower quality ones... well that all costs money.
    All you can do is make sure that the contamination doesn't happen at your end by keeping them in a closed container until ready to install them.
    Once the rod is inside them they are pretty safe from contamination.
     
  3. Henry feldman

    Henry feldman Well-Known Member

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    Can't imagine sitting on the clean microfiber towel awaiting putting in the rod it got contaminated, it was taken out of the bag and put into the carriage, then the rods were put in. It is a clean room (the CNC is in another room) so I suspect a bad part. Unfortunately the local store only had 20mm long bearings, so the new ones won't arrive until next week...
     
  4. Spoon Unit

    Spoon Unit Well-Known Member

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    I took pretty much no care of my bearings, not being aware I needed to. That said, they all sat in the bag until they were added to a rod. As far as I can tell, they're all OK.
     
  5. UlrichKliegis

    UlrichKliegis Well-Known Member

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    Maybe it's a nice project to create some wipers that can sit on both ends of the bearings and keep the dust off. Some circular bracket and a felt ring. Imagine what will happen when people start to use their BBs as milling machines...
     
  6. Henry feldman

    Henry feldman Well-Known Member

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    There is a reason I have the CNC in a another room by itself. The first time it used MDF I choked my big shop vac 's HEPA filter (now have a cyclonic separator with static reduction on order) due to the staggering quantity of dust. There are whole chatrooms on the inventables site solely devoted to dust boots. I can't imagine putting the printer anywhere near a CNC. Of course if you did at least you wouldn't have to worry about anybody stealing your prints via recording the sound since when the CNC is on with dust collection, you can't hear yourself think and need at least gun-mufflers if not earplugs under them!
     
  7. Henry feldman

    Henry feldman Well-Known Member

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    noticing a lot of folks mentioning "bad bearings" in their posts. Someone else just posted that their LM8LUUs were "leaking bearings" so it is possible a few of the bearings "leaked" out on mine too. I could put my borescope inside a check, but that's more work than just waiting for new ones from ServoCity. I will note this bearing was leaking some oil onto the rod compared to the one on the right, so certainly something was broken (seal, missing ball,etc)
     
  8. Springfield-Jack

    Springfield-Jack Well-Known Member

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    Had at least 2 "bad bearings" -of course the order of the build meant that the X&Y got the best ones!-A magnet sweep of the floor to find a missing screw turned up half a dozen tiny spheres!
     
  9. UlrichKliegis

    UlrichKliegis Well-Known Member

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    Oh yes, I know what you are talking about. I used to work next to (that was next door but still bad) a milling machine making surgical planning models from polyurethane foam for some years. A two flute bit biting its way through that hard foam at 25kRPM for hours can be nerve wrecking. It can. I hope I recovered...
     
  10. Claudio Perez Gamayo

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    at least one bad bearing here too
     
  11. UlrichKliegis

    UlrichKliegis Well-Known Member

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    All these linear bearings keep their balls in plastic pockets in a chain-like tape or tape-like chain. They are perfectly packed there for their regular job when they are an interface between the rod and the bearings mantle carrying the load. They roll along there in a convection-like manner.

    What they don't like at all is to be levered out of their pockets by oblique forces, for instance when their new master tries to insert a rod in some odd way, not straightforward coaxially adjusted. You have practically no chance to re-insert missing balls to where they once belonged.
    A guiding template as an aide to mate rod and bearing gently colinearily and coaxially might be a nice project for your printer - if it gets that far.
     
  12. Henry feldman

    Henry feldman Well-Known Member

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    So in the interest of science, I borescoped the bearing, and yes, there are some ball bearings missing inside. Strangely not near the ends where one would expect them to be knocked off, but towards the center of the tube.
     
  13. Henry feldman

    Henry feldman Well-Known Member

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    Got replacement bearings from ServoCity, and voila. No more grinding. Assembly will recommence after my whirlwind trip to give a talk on the west coast...
     
  14. Richard Barbosa

    Richard Barbosa Well-Known Member

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    I had to replace all 8 crappy bearings with new ones. Actually Amazon carries, both, cheap and quality bearings and Servo City is great. I had made a video of the bad bearings to show E3D and was told that they were in talks about the bearings but that was the last I heard of it. I can only assume they are well aware that the bearings are not cutting the mustard.
     
  15. Madeinoz67

    Madeinoz67 Active Member

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    I've found a couple of small balls on the bottom of my tray as well
     

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