Notifications
Clear all

Scratched rods from linear bearings  

Page 5 / 11
  RSS
ed
 ed
(@ed-3)
Reputable Member
Re: Scratched rods from linear bearings


https://www.thingiverse.com/thing:1974253/zip try this for packing the bearings

Park Polylube is on the lines of marine grease not sure I'd put that in my linear bearings, though I use it for everything on my bike. I will say I'm leaning toward the lithium at this point as that was the direction I was steered toward from my source but was also told to not to pack them too heavily, I believe it was 30% grease in the bearing channel, good luck trying to figure that out though. The wife brought me a couple of monoject injectors from her office but I've yet to try to push grease through one. I plan on continuing to waffle on the lube right up until I start the build.

Posted : 13/01/2018 4:54 pm
JLTX
 JLTX
(@jltx)
Reputable Member
Re: Scratched rods from linear bearings




Don't forget that these are recirculating ball type bearings and the tiny bearing balls need to roll freely to circulate in the tracks. Placing grease that is too thick will not allow the balls to properly circulate and slide on the rod. Any lightweight type Lithium grease or a 3-in-One type oil is what I see to be mostly recommended...not wheel bearing grease.

Agree. The SuperLube I use is low viscosity and I had zero problems on thousands of hours on MK2s. The video I posted is surprisingly effective at replacing the shipping oil. I didn’t believe until I tried it.

Not sure what video you're talking about but I planned on using naphtha or maybe taking the bearings into work and cleaning them with xylene, last resort as I can't stand the smell of the stuff... I'm still waffling on how I plan to lube bearings though.

See my earlier post in this thread for link. You don’t really need to remove the shipping oil that thoroughly. That oil is not bad, just insufficient. Simple process to replace with grease. With the correct hardened rods this works very well.

Posted : 13/01/2018 5:40 pm
james.f8
(@james-f8)
Active Member
Re: Scratched rods from linear bearings

Im in the beginning of assembly for an MK2S, and I test fit the bearings prior to assembly, and they were scratchy, and now my rods have scuffs. I wiped the rods prior and checked to make sure the ends of the bearings were clean prior to sliding the rod in.

I reached out to Prusa support to see if they can assist, as I don't want to go beyond step 2 (Y-Axis) if this will be a problem with the bearings and rods. Are the rods the same between the MK2S and the MK3, in terms of hardness/material? I bought my MK2S in July of 2017 (Just before MK3 announcement, unfortunately).

Thank you.

Posted : 14/01/2018 8:21 pm
peter.b12
(@peter-b12)
Eminent Member
Re: Scratched rods from linear bearings

I received my assembled MK3 mid-December. If I have unhardened rods and/or faulty bearings, approximately how many hours of running does it take for the scratches/grooves to manifest itself?

Also can @josefprusa please outline how they prepare the bearings prior to assembly in the factory?

...
Posted : 15/01/2018 1:08 am
gibsonlpsl
(@gibsonlpsl)
Eminent Member
Re: Scratched rods from linear bearings


I received my assembled MK3 mid-December. If I have unhardened rods and/or faulty bearings, approximately how many hours of running does it take for the scratches/grooves to manifest itself?

Also can @josefprusa please outline how they prepare the bearings prior to assembly in the factory?

For me, I'd estimate I noticed it around 20 hours in to the life of the printer. However, judging from other's comments, it seems it may show up even much sooner. If you used it even a few hours it's probably worth an examination of your rods.

...
Posted : 15/01/2018 1:29 am
dryja123
(@dryja123)
Honorable Member
Re: Scratched rods from linear bearings

Grab a file and run it against the very end of the rod and see if it scratches. If it scratches easily start a chat with a rep and get new rods before you have real issues. Refer to CRT's YouTube video regarding how to test the rods.

Jo confirmed in Tom's MK3 live build that some unhardened rods slipped through and they'll replace them.

Posted : 15/01/2018 1:59 am
jweaver
(@jweaver)
Honorable Member
Re: Scratched rods from linear bearings

Prusa told me to check the rods with a magnet..

The assumption is that if they are not attracted to a magnet they are stainless...

Anyone got a set of each type and want to test?

Posted : 15/01/2018 7:45 pm
Peter
(@peter-12)
Estimable Member
Re: Scratched rods from linear bearings

I thought it was hardened vs not hardened, not stainless vs not stainless.

Posted : 15/01/2018 8:56 pm
jweaver
(@jweaver)
Honorable Member
Re: Scratched rods from linear bearings


I thought it was hardened vs not hardened, not stainless vs not stainless.

I did too, but the fact that they want to check with a magnet means they are looking for stainless (atleast thats my understanding of steel and magnets)..

So I assume they rods they are shipping are either stainless, or hardened...

Posted : 15/01/2018 8:58 pm
dryja123
(@dryja123)
Honorable Member
Re: Scratched rods from linear bearings

Received my order today with hardened rods. I think they may have sorted their issues.

Posted : 16/01/2018 1:37 am
jweaver
(@jweaver)
Honorable Member
Re: Scratched rods from linear bearings


Received my order today with hardened rods. I think they may have sorted their issues.

How do you know they are hardened?

Posted : 16/01/2018 1:40 am
Laird Popkin
(@laird-popkin)
Estimable Member
Re: Scratched rods from linear bearings

On Facebook "Michal Průša: the "soft" rods are hardened stainless steel which has HRC 28 so it's non magnetic, the hardened ones (correct ones) is steel with HRC 60-62 and they are magnetic".

My rods aren't magnetic. Does that mean that they're the soft rods that will wear out?

...
Posted : 16/01/2018 2:12 am
dryja123
(@dryja123)
Honorable Member
Re: Scratched rods from linear bearings

My rods are magnetic. First thing I did was take a magnet off of the fridge and it stuck right on.

Posted : 16/01/2018 2:14 am
JLTX
 JLTX
(@jltx)
Reputable Member
Re: Scratched rods from linear bearings

Ok, I just received my new rods tonight. They are very different, much smoother feeling, have a brighter color, and are magnetic. Old rods are less smooth, duller, and non-magnetic. Very clear difference. The new ones feel harder, which I know seems silly. But I could tell when I first put the machine together that the rods didn't feel as nice as on the MK2S (which I had already sold so couldn't compare directly).

Posted : 16/01/2018 5:36 am
MarcoZ76
(@marcoz76)
Eminent Member
Re: Scratched rods from linear bearings

My MK3 has scratch and big groves, on Y linear rods. Also they are not Magnetic. I made a vide to compare a linear rods with real steel hardened on my Haribo edition MK2S and standard MK2S and MK3 printers.

Check the video for magnatic test:

...
Posted : 16/01/2018 12:54 pm
edith.f
(@edith-f)
Active Member
Re: Scratched rods from linear bearings

got my rods replaced, but only x and y xis, hope they will send me the z axis rods...

this is such a joke how they handle this ... my printer ran nearly nothing since i got it on 22.dec

Posted : 16/01/2018 5:17 pm
arthur.c2
(@arthur-c2)
Trusted Member
Re: Scratched rods from linear bearings

Hi guys, my MK3 has been shipped today !

I had this problem on my first printer, a french Tobeca 2. The rods were scratched within a few weeks, so I changed them for HPC rods but i kept the same linear bearings and never had problem since.

The rods are hardened steel (60 +/-3 HRC). Also it's h6 tolerance instead of g6 which means a little less play. I bought them by 1m length and had to cut them myself. You have to use a grinder, no way to make any mark on this with a metal saw, it's really really hard !

If I have understood corerctly, the problem is that some people have steel rods and others have stainless rods ?

Any idea why ? Seems illogical.

I will receive my printer soon and i don't know if i use included rods or not ... I don't want to change them in 2 weeks ...

Also I could buy quality linear bearings, do you know where i can find some ? (not misumi or other chinese ones)

Posted : 17/01/2018 4:28 pm
jweaver
(@jweaver)
Honorable Member
Re: Scratched rods from linear bearings

I will receive my printer soon and i don't know if i use included rods or not ... I don't want to change them in 2 weeks ...

When you get it, check the rods with a magnet.. if they don't attract, they are stainless and therefore soft.. If they do, then they are hard.

If you have the hard ones, there should be no reason not to use them.

Posted : 17/01/2018 4:44 pm
RotaryDane
(@rotarydane)
Eminent Member
Re: Scratched rods from linear bearings


...
The rods are hardened steel (60 +/-3 HRC). Also it's h6 tolerance instead of g6 which means a little less play. I bought them by 1m length and had to cut them myself. You have to use a grinder, no way to make any mark on this with a metal saw, it's really really hard !

If I have understood corerctly, the problem is that some people have steel rods and others have stainless rods ?

Any idea why ? Seems illogical.

I will receive my printer soon and i don't know if i use included rods or not ... I don't want to change them in 2 weeks ...
...

It comes down to the composition of the stainless steel (SS), basically it can have a higher or lower content of certain additives to give it it's "stainless" properties. Carbon content is however what makes Steel Steel, and it's this that defines how 'hardenable' a steel is and the treatment of the steel is pretty crucial to it's final hardness. The addition of Nickel typically increases the corrosion resistance, but detrimentally effects hardness and telltale makes the steel non-magnetic.
So most likely what happened is that PR received a batch of rods, which were indeed SS, but the wrong type with a too-high Nickel content and/or not hardned properly, which made them too soft as many people have pointed out. There isn't much to be done other than exchange the affected rods for some that are guaranteed to be the right steel.
Luckily though, it's easy to identify, as the 'faulty' rods are non-magnetic or only slightly magnetic, and the correct ones are properly magnetic.

Have a MK3 with badly scratched rods myself, but was holding off ordering new rods until the root cause and propper solution came out.

Posted : 17/01/2018 5:27 pm
Pintie
(@pintie)
Eminent Member
Re: Scratched rods from linear bearings

i will get new ones, too.
i will get them with the new pei coated sheets in 2-3 weeks

Posted : 17/01/2018 5:29 pm
Page 5 / 11
Share: