Vid Samples of the Heated Bed with Misumi Bearings

Discussion in 'Calibration, Help, and Troubleshooting' started by JohnEsc, May 21, 2016.

  1. JohnEsc

    JohnEsc Well-Known Member

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    Here are 3 videos of the progress of my heated bed movement...
    First video, sound of the bearings BEFORE the upgrades of the rods, drilled-out holes, and new bed corners:
    Feb. 1, 2016: https://www.dropbox.com/s/pso9loj96kgqy84/VID_20160201_183921.mp4?dl=0

    Second video, sound of the bearings AFTER the upgrades of the rods, drilled-out holes, and new bed corners:
    Feb. 21, 2016: https://www.dropbox.com/s/5ev9mm4su2omuew/VID_20160221_123429.mp4?dl=0

    Third video, sound of the bearings after replacing the bearings from China with Misumi bearings made in Vietnam:
    May 20, 2016: https://www.dropbox.com/s/p0lr5dv8easvfy5/VID_20160520_203936.mp4?dl=0
     
  2. R Design

    R Design Well-Known Member

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    Haha.

    Be interesting to side by side a print.

    What was the rod upgrade?

    Now my bearings are perfect, it's the lead screws that I'm starting to wonder about. They've always wobbled visibly but at .25mm layer height (not at 0.1mm) there's a slight repeated banding.....
     
  3. Old_Tafr

    Old_Tafr Well-Known Member

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    I don't really like the adjustment of the Z-Axis smooth rods or the lead screws.

    Apart from (maybe not so) obvious manufacturing defects in the rod itself, the way of securing the rod in the (flexible?) coupling could lead (no pun intended :) ) to the rod not being perpendicular OR it could even be that the Z motor(s) are not perpendicular either.

    Both effects could lead to the lead screw waddling (spell checker preferred waddling to wobbling) at the top even if the rod itself is perfect.

    Any slight deviation from true at the motor end is simply amplified the higher you go.

    I cannot immediately think of way to check and correct these two problems, what happens in practice is that grease helps disguise the problem, moving the bed to the top forces the lead screw into position and the combined effect probably either forces the screw straighter in the flexible coupling (with the bed at the top releasing and re-tightening the one grub screw could possibly help align it) and or attempts to bend the motor shaft (by a minute amount) and will place a lot of strain on its bearings.

    It could be argued however that the lead screw should "float" as the alignment of the bed is done by the four vertical smooth rods, so the only real need for the lead screw to be accurate is the profile of the threads and the thread pitch, so that you get accurate vertical steps.

    In this case having the motor shaft, flexible coupling and lead screw perfectly aligned is of less consequence, but the more tightly constrained it is (particularly at the motor end) the more wear will occur.

    I had seen a post where a different flexible coupling (with some actual flex) is suggested, this might help.

    Checking the lead screw on a surface plate before assembly would be good, in lieu of a surface plate (doesn't every good home have one?) I find some MDF panels are remarkably flat and temperature stable.
     
  4. Alex9779

    Alex9779 Moderator
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    Just for info @JohnEsc replaced the rods because he had his box BEFOR the Z issue occurred after which E3D delivered updated rods if I remember correctly. So John had the very first release. I see no point at the moment to replace the rods...
     
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  5. Old_Tafr

    Old_Tafr Well-Known Member

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    A general thought about bearings, not necessarily relevant to this post but as with all the mechanical components is that we are all going about the process backwards.

    We assemble the parts, then we maybe discover noise, rough movement etc. This could in fact be due to misalignment of components that then make things run roughly, with the components themselves being just fine.

    I doubt that e3d have time to check each bearing on each rod, or to quality check say each rod for accuracy in all dimensions. They rely on the supplier's quality control, maybe spot checks, their own builds and customer feedback.

    At some stage I read a suggestion to check linear bearings on rods to match them up, this is probably as close to a check that anyone can make at home, but some checks before starting to assemble would be good.

    I think Spoon Unit (sorry it was Mike01hu :( ) suggested that the bearings have to be run on the rods dozens? of times before they "run in" I personally find that they need this plus far more lubrication than applied by the manufacturer. As Mike01hu mentions don't allow the bearing to twist round the rod if you are running them in manually before assembly.

    What we should be doing is checking all components, running them in before assembly, then assembling, then if there is rough running checking for misalignment.

    Measurements I have made, for example between the X-Carriage smooth rods show them to be parallel with a high degree of accuracy, but it far more difficult to say check the alignment of the four Z rods.

    Pre-assembly and lots of grease !

    If we discover rough running bearings and a mismatch of sizes prior to assembly then this is the time to get replacements from e3d.
     
    #5 Old_Tafr, May 21, 2016
    Last edited: May 21, 2016
  6. mike01hu

    mike01hu Well-Known Member

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    I commented elsewhere on bushing issues and the need to "run in" each one but it appears that this does not always work, as I have found out. There is one thing that you should note, and that is that these bushings do not like rotational movement so that should be avoided when running the bushings by hand before fitting. Despite my problem bushing, I have not seen any deterioration in print quality but as it is on the Y-axis there is good mechanical rigidity, unlike the Z-axis, where any disruption in a bushing will increase the chance of banding etc., this is further emphasised by the automatic levelling process whereby the Z motors are in continuous movement in step with X-Y movement.
     
  7. Alex9779

    Alex9779 Moderator
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    My opinion on this is that running in is a kind of wear. You move the bearing as long as the unevenness somewhere in the bearing might wear-out... But wear is what I do not want and if you lubricate the bearings then you reduce wear and so you reduce the effect of running in. So you should do that with dry bearings then when they feel smoother grease them. But still it is wear and wear increases tolerances and increased tolerances result in play and play reduces quality...
    If a bearing does not run smooth out of the box the bearing is junk... That's my opinion...
     
  8. Alex9779

    Alex9779 Moderator
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    BTW too much grease is also not good for bearings. Named manufacturers like INA have detailed manuals how to grease or lubricate their bearings...
     
  9. mike01hu

    mike01hu Well-Known Member

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    I'll go with that Alex. Although, I did say before that cheap bushings do have a less good finish on the ball tracks and "running in" can partially address this but there is no real solution other than changing it for a better quality product.:cool:
     

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