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Z-axix linear bearings

Posted: January 23rd, 2017, 1:30 am
by nilrog
I touched upon this on my printer thread...and I have seen it mentioned alot on the UM forums.

The linear bearings on the Z-axis really sucks, to the point that I can't believe that UM uses these ones in their printers. The printer is brand new and 9/10 i'm having a gap in the printed object approx. 10 mm from the build plate. It is not random...it happens on the same place all the time, when it happens. Never at a different height.

It is exactly like this guy described it:
https://ultimaker.com/en/community/1112 ... ply-149119

If I manually move the build plate up/down a couple of times then the following print might be ok, but not always. I was thinking about disassembling the printer to try and clean the bearings. But after reading the post/thread above...it feels like waisted time.

Apart from going for high-quality Misumi bearing, that requires a company to order through, is there any other good source for these linear bearings? I don't mind paying a bit...as I want a printer that can constantly, with ordinary maintenance, deliver consistent print results. If Misumi is the only good option then I will find a way to order from there.

Re: Z-axix linear bearings

Posted: January 23rd, 2017, 6:30 am
by johan
Ultimaker has as far as I know switched to using Misumi bearings on newer machines, you could probably get bearings from your local Ultimaker reseller.

Re: Z-axix linear bearings

Posted: January 23rd, 2017, 6:48 am
by Neotko
Ultiarjan fid that and got crappy quality bearings.

Indeed um3 uses misumi, but the stock left on resellers might not be.

Re: Z-axix linear bearings

Posted: January 23rd, 2017, 7:05 am
by nilrog
Ok, interresting info, thanks :)

I just asked 3D-Verkstan if they have a "solution" to the bearing issue. If this had been an old and used printer it would be a non-issue. But brand new parts I expect to work better. And I did my best to align the bearings according to the instructions when I assembled and mounted the build platform.

If they don't have a good solution then I will buy the Misumi bearings myself.

Re: Z-axix linear bearings

Posted: January 23rd, 2017, 8:17 am
by Anders Olsson
I have this issue on the UM2Go, and I agree, it is unbelievable that one finds such crappy components on a machine in this price range!
Changed bearings once on the UM2Go, but it did not completely solve the problem, I think the replacement bearings might also have come from a bad batch.

My UM2, UM2E and UM3 does not suffer from this problem at all as far as I can see though (although sometimes I hear strange sounds from the bearings in them UM2E).
The fact that the bed is much lighter at the UM2Go makes it more sensitive to jamming bearings though. Just adding some weight to the bed probably would do the trick in my case, but getting a set of good bearings would be the best option of course.

I was just thinking about if one could design a printable spring that puts a constant load on the buildplate by the way. It would be more elegant than just adding some weight, but other projects probably have higher priority right now :-)

Re: Z-axix linear bearings

Posted: January 23rd, 2017, 8:37 am
by johan
The single trapezoidal nut isn't really a good solution to move the platform. The nut gives way and you only use gravity to drive the platform downwards. A better solution would be a pre-tensioned nut (or a ball screw like Zortrax uses).

Re: Z-axix linear bearings

Posted: January 23rd, 2017, 9:06 am
by LePaul
I think the Heated Bed Upgrade for my UMO came with the better bearings?

Re: Z-axix linear bearings

Posted: January 23rd, 2017, 9:32 am
by nilrog
Anders Olsson wrote:I have this issue on the UM2Go, and I agree, it is unbelievable that one finds such crappy components on a machine in this price range!
I opened that can of worms in the UM forum once :-P ...and everyone jumped on me saying that the UM family is not "premium" and we should not expect better.
If I had bought a cheap chinese printer I would not have been surprised...but in an Ultimaker? :shock:

The bearings they use(d) are probably good in another application...but not in a 3D-printer...at least not one that claims to have the Z-resolution that UM does. The fact that you can "hide", or minimize, the effects by adding weight, and/or a pre-loaded nut (or one with less play), only shows that they are not up for the job.

Ofc it would have been nice to have a ballscrew...but with good quality bearings, and a z-nut with little play, that would not be needed to have good enough movement. At least not in a printer the size of an UM. That can be seen in the reports from those who upgraded their printers to Misumi bearings (at least).

Re: Z-axix linear bearings

Posted: January 23rd, 2017, 10:28 am
by Neotko
Well UM should aim to be better, and I suppose they do, but at the speed rate of an Ent.

Re: Z-axix linear bearings

Posted: January 23rd, 2017, 11:41 am
by gudo
Hi to all !
Anders
I was just thinking about if one could design a printable spring that puts a constant load on the buildplate by the way. It would be more elegant than just adding some weight, but other projects probably have higher priority right now :-)
Last year In early december, I got Z bearing issues, I changed them by a good quality new others, I took the opportunity to also change the z nut by a new one, and I kept the old one to make an adjustable anti backlash system,
It's very easy to do ! ;-)
- remove the 4 M3threads on the old nut by drilling the threaded holes at 3.2mm
- On the 4 screws that hold the new Z nut, use 2 longer M3 screws ( 25/30mm lenght) for indexing,
- find an appropriate spring with a smooth compression (with 10/ 10.5 mm ID , about 0.6/0.8mm wire dia. and about 8/10 coils)
You will get an adjustable pressure anti backlash system
That will improve a lot the Z stability and give a great accuracy
Since the modification it works well with no issues.
Image
Image

Re: Z-axix linear bearings

Posted: January 23rd, 2017, 11:48 am
by Neotko
Cool mod Gudo. Do you mind if I make a video tutorial showing the steps? Seems very easy and cheap to do, and I still have one bad nut from um on a bag.

Re: Z-axix linear bearings

Posted: January 23rd, 2017, 11:51 am
by LePaul
See doesn't that just make you want to send your printer to Gudo for servicing? Where's my packing tape :)

Re: Z-axix linear bearings

Posted: January 23rd, 2017, 11:59 am
by gudo
Yeah Neotko ! a video tutorial would be a great idea ! :-P
LePaul, when you want ! ;-)

Re: Z-axix linear bearings

Posted: January 23rd, 2017, 12:10 pm
by nilrog
@gudo

Great! I was thinking about such a solution for the z-nut on my way home today...now I don't have to think about the implementation :lol:

Re: Z-axix linear bearings

Posted: January 23rd, 2017, 3:51 pm
by Izzy
Hi Gudo, are you putting your buildplate stabliser on youmagine?