Z-Axis linear bearings issue

[mjmdavis 0]

I was having trouble with my printing. @gr5 helped me identify it as a probable z-axis issue in this topic here.

After taking my z-rod out to clean, I realised that I also appeared to have a problem with my z-axis bearings. They stick often and hard enough to support the entire weight of the bed. See the video below:

 

 

I had pretty severe crunching sounds the whole time I had the printer but many people said this was normal. Now I'm thinking that mine were, in fact, indicative of a real issue. What should my next step be?

examples of printing issues:

Edited June 25, 2017 by Guest

[neotko 1,417]

If you are in warranty check with your reseller. It might be the z nut (a new one costs 3€ from pololu) or the flanged bearings (misumi new ones cost 10-20€ each depending on the quality)

Google neotko pololu misumi ultimaker

And check more posts with that issues and solutions.

[mjmdavis 0]

@neotko I guess that there could also be wrong with the z-nut but in the video, the z-screw has been removed. So it seems that I definitely have an issue with the linear bearings on the z-axis.

How does one swap the bearings out?

[neotko 1,417]

@neotko I guess that there could also be wrong with the z-nut but in the video, the z-screw has been removed. So it seems that I definitely have an issue with the linear bearings on the z-axis.

How does one swap the bearings out?

On umo+ is easy since it has scape holes up and down, but um2 only has bottom for the shafts to leave. I suppose with strength and much care. Check the um2 assembly manual and follow in reverse ?

https://github.com/Ultimaker/Ultimaker2/blob/master/um2%20assembly%20manual%20V1.1%20_english.pdf

Edited June 25, 2017 by Guest

[rowiac 50]

@mjmdavis,

From your photos it looks like you have constant z-axis banding that you are trying to solve. If so, replacing the sticking Z bearings may not solve the problem.

The symptom of bad Z bearings is a bad layer at approximately 10-12mm height on the printed object, which shows up consistently. This is a result of the bearings sticking after direction reversal and that happens at about 10-12mm after the direction reversal, which you can see happening at the beginning of your video.

Continuous horizontal banding is a different issue that has been discussed at length on this forum. Regardless of this however, changing your Z bearings to better quality ones that don't stick is a good move.