X-axis rod damage after 50 hrs: Misaligned rods, lubrication, or bad bearings?
 

X-axis rod damage after 50 hrs: Misaligned rods, lubrication, or bad bearings?  

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Fourninetysix
(@fourninetysix)
New Member

Hello All,

I've clocked about 50 hours of print time on my new MK3S+, overall it's been good fun and running smoothly but I'm curious as to whether other users have had the same issue:

gouging on X-axis

Initial prints had no unusual noises but a few prints ago, a 'groaning' noise started coming from the area of the extruder head. This progressed to a low, grumbling noise whenever the X-axis would traverse at a certain speed. I pulled apart the X-axis and discovered a series of long gouges on one of the rods that wasn't there during the initial assembly. My theory is that it could be a couple things: 1) One of the LM8UU bearings failed. 2) The bearing was 'fine' but since the Prusa manual doesn't mandate that the bearings are packed with grease before assembly, the bearing failed prematurely. In reviewing this, it seems strange that the guidance is to just place the bearings on the rods right out of the packaging, as they come packed in some kind of lightweight anti-corrosion oil which doesn't seem to be anything like the lubricant recommended by Prusa for maintenance. And lastly 3) because of user error, one of the X-axis rods or bearings was misaligned, causing the gauging that I have. 

 

I don't doubt that my accuracy in assembling my first 3D printer is a bit off, but it seems that a few dozen hours is a bit short to have the bearing cut grooves into the X-axis rails based on one of the factors I listed above, or one that I haven't thought of. If you guys have any thoughts as to what the likely cause is, I'd be curious to hear it. Perhaps I should be more diligent on assembly? In any case, I have new rods and bearing on order, I plan to pack them thoroughly with Super Lube 21010 - we'll see how it goes.

-Will S.

 

 

Posted : 02/04/2021 8:19 pm
Dan Rogers
(@dan-rogers)
Prominent Member

check for alignment issues when you get in there to repair the problems.  something other than "has plenty of oil" could have contributed to that issue.

Since you may need new bearings - I cannot speak poorly of Drylins - elimintate the balls entirely.  I don't have 100 hours on them yet, but i'm over 50.

Posted : 02/04/2021 8:39 pm
pcweber
(@pcweber)
Estimable Member

Something in the extruder assembly sounds to be off. Make sure you used the m3x10 screws and nothing bigger. Make sure you have followed the wiring instructions, something may be touching. I've got over a thousand hours and I have packed the bearings once and plan to replace the X and Y axis bearings during my next major maintenance routine.

There's several opinions regarding the drylins, since I get great results from the stock bearings, I hesitate changing them.

Finally, having just purchased your printer, yours is under guarantee. Call tech support, they're there to help. You're not alone.

 

Stay safe and healthy, Phil...
Posted : 02/04/2021 9:15 pm
Clarmrrsn
(@clarmrrsn)
Honorable Member

Could be a bad bearing, as even with just the light oil on them they should run a lot longer than 50 hours

By the sound of it you had the issue very quickly after build, quick question, were the bearings aligned correctly on the rods, with 2 rows divided evenly over the top of the rod to spread the load as per the manual. 

Did you mark the bearings correctly and align them on the X axis rods when mounting the extruder? If just 1 row was on top of the rod this could also cause this issue as all the weight is on 1 row of bearings.

When you get your new bearings and rods be sure to pack correctly, this method was recommended by Prusa Support when my bearings were a little noisy after installation. 

Soak the bearings in 99%IPA to remove the shippjng oil, dry them thoroughly then mark the bearing positions as per the manual before packing. Squirt a good amount (bearing about half full) superlube grease with PTFE (or other recommended grease) inside the bearing, THEN put your finger over the other end of the bearing and insert the shaft perfectly straight and carefully. While maintaining good pressure with your finger to form a seal press the shaft in with firm pressure, this works the grease into all the races and in and around the bearings and packs it properly.  You will feel the grease try to find its way past your finger, try not to let it, make it find its way around the ball bearings if there is too much you will feel it. You will be very surprised how much  grease is used this way.

You dont want to overpack, but when you remove and reseat for assembly a little will come out anyway.

Tank you very much!...
Posted : 03/04/2021 1:14 pm
cwbullet
(@cwbullet)
Illustrious Member

Could be any of the items that you listed.  Work through each and determine the cause.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 03/04/2021 9:43 pm
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