Help before I send this thing back.  

RE: Help before I send this thing back.

@ferly

That is what I was concurring with.  

RE: Help before I send this thing back.

Posted by: @ferly

I tightened the ubolts only so I couldnt move them with my fingers. They do need a lot of tension to stay in place, but can very easily be overtightend. Try to lose the tension to the point where you could almost turn them by hand.

Well your misfortune shed light on the correct belt tension, so something good came from it. So thank you ;).

I have a 11h print going now, when its done, Ill do what you suggested. Tighten until I can almost spin the bearing and see if that helps. Wouldn't that be something if it was just to tight, even though it wasn't even that tight, lol.

RE: Help before I send this thing back.

Bearings should be tighten as little as possible, the u bolt should just be hitting the bearing so they could not move, if you tighten to hard, then you can bent the bearings.

The whole printer should not be tighten to much on bolt etc.

RE: Help before I send this thing back.

@burrfree

Not sure if this will help.  I had a rattle in my Y-axis when I used Hilbert fill pattern and use an angled wrench/spanner to tighten the U-bolt  nut without removing the heat plate on a Mk3S.  I use the the second/simple version, the the more complex one was found latter.

https://www.thingiverse.com/thing:3301027
https://www.thingiverse.com/thing:2766241

RE: Help before I send this thing back.

Posted by: @peter-m-3

Bearings should be tighten as little as possible, the u bolt should just be hitting the bearing so they could not move, if you tighten to hard, then you can bent the bearings.

The whole printer should not be tighten to much on bolt etc.

 

I gave this a try. Tightened it to the point just past where I could not spin the bearing in the cutout. I mist say, this is much looser than I had it, but it didnt do a thing for the vibration. I can still hear the rod vibrating inside the bearing. Mostly in the center of travel in the middle of the rod. Seems the stepper vibrations cause the rod to vibrate most in the middle and you can hear it in the bearings.

I can try thicker grease maybe, but really at this point this is getting ridiculous. I didn't spend 800 dollars on a printer that I have to tweak here and there to get it quiet. Maybe if I tighten this nut like this, tongue out at a right angle, left foot in the air, maybe a slight cross breeze.....

My best solution thus far has been sticking paper between the bearings to slightly miss align them. This is not an acceptable solution though for a brand new printer. A few years old I dont mind doing hacks, but not brand new.

My experience thus far with prusa has been a huge letdown. No solutions can be given other than throwing more rods and bearings at it. Doing a few google searches I find this is not an uncommon complaint. Linear rails upgrade would most certainly fix it, but I am not spending more money, and I will not modify the stock printer and void warranty, especially now since I am heavily leaning towards returning it.

I am out of ideas, and I appreciate the help you guys here have given. Prusa was supposed to get back to me today with a solution ans never did, so.... Just an overall bad experience. I know they may not happen often, just sucks I drew the short straw.

RE: Help before I send this thing back.

@burrfree

Sorry, you are having a tough time.  I have had generally positive experiences with my multiple Prusas.  Not the same from the many others.  I have found that unusually the problem is a stupid mistake on my part such as I broke a wire, overtightened a screw, or misread the instructions.  Keep trying and you will get there.  

RE: Help before I send this thing back.

Have you tried adjusting the pulley on the back by the motor?  Mine made that noise as well and my pulley was off by just a bit.  I also had the U-Bolts too tight.  

Once again, my thoughts.

RE: Help before I send this thing back.

Posted by: @osmosis

Have you tried adjusting the pulley on the back by the motor?  Mine made that noise as well and my pulley was off by just a bit.  I also had the U-Bolts too tight.  

 

Once again, my thoughts.

Yeah so I had to actually flip my pulley around because the belt was riding up on the motor side and I was already as close to the motor as I could get. Flipping made no difference though.

I really want to keep it, but I already have the wife screaming in my ear "I thought you said this was going to be quiet, I thought you didnt have to mess with it, blah blah blah"  lol

As far as assembly specs are concerned, maybe prusa could release a recommended torque setting for all the screws. That would eliminate to loose or to tight issues. As for my Frame and everything on it (other then the ubolts), they are as tight as then can be without stripping the heads or threads.

RE: Help before I send this thing back.

I noticed elsewhere on the forum that one member had to put a shim on one side of his Y-axis pully bracket to correct his misalignment. 

RE: Help before I send this thing back.

Posted by: @agkirk

I noticed elsewhere on the forum that one member had to put a shim on one side of his Y-axis pully bracket to correct his misalignment. 

I don't know how much the offset belt has to do with my issue, its just something i noticed. Also whats strange is both the motor pulley and idler at the other end have the belts light up pretty well when the table is drive to their extremes. Its during travel from one side to the other the belt rides into the side. What I cant figure out is why, because the belts come out of the center of the table straight. Perhaps the way its being attached is putting a slight twist to it that I cannot see well when its all assembled.

RE: Help before I send this thing back.

Just an update for people posting here, I got my third set of rods and bearings. I measured all the rods I have, including the Z and X Axis ones, and the rods are all the same size within .0002" of each other at .3144 - .3146". Its safe to say the rods have a good quality control to them. The bearings on the other hand I dont think so. This last batch are nice and tight. When I assemble it, I have zero slop than can be felt by tugging on the front right corner of the bed.

My vibrations is virtually gone. There is still a slight vibration coming from one of the bearings at a certain speed, but its so faint I can look the other way. That being said, with how sloppy the bed was with the previous rods and bearings, I have to say Misumi bearings are not that great.

If someone else is out there with the same issue, contact prusa. Keep getting bearings until you get a set that fits.

RE: Help before I send this thing back.

Posted by: @

@tool_aenima1

Good to hear Prusa is helping out.

-

In my opinion Prusa has two major foo-pahs in their instructions: they claim the bearings do not need to be cleaned and greased. Every bearing manufacturer - unless the bearings are sold pre-lubricated with appropriate G2 Lithium grease - recommend bearing be cleaned and greased.

Be sure to add grease to the bearings BEFORE installing them. Prusa ships bearing in the same ultra-light preserving oil they come with from the factory. That oil is not suitable for operation.

This is 100% correct and should be noted in the instructions 👍 👍 

RE: Help before I send this thing back.

These are the kind of issues that I wanted to avoid so I ordered both my MK3s preassembled.  Worth every penny.

RE: Help before I send this thing back.

No way to know for sure, but I'm curious if they install the bearings as they come in the kit or clean and grease them before installation. 

RE: Help before I send this thing back.

No idea, but since the thing comes with the prusa nameplate printed in galaxy silver still stuck to the PEI and on the printer I would hope so.  So far I've not had any issues that weren't of my own doing.   I'm not far off from probably wanting to do a full round of maintenance so I'll probably be checking all that stuff soon.  Doing multi-day mmu prints etc really put the hours on. Every other week I get in and clean things out with the compressed air.   I intend to replace the last of the orange pieces the next time I take the machines apart so I'm definitely going to look at them.

RE: Help before I send this thing back.

Posted by: @baklin

No way to know for sure, but I'm curious if they install the bearings as they come in the kit or clean and grease them before installation. 

I would like to know this too. If they don't grease them then my next Prusa(s) would have to be the kit again.

My assembled printer did not have greased bearings

Posted by: @brad-2

Posted by: @baklin

No way to know for sure, but I'm curious if they install the bearings as they come in the kit or clean and grease them before installation. 

I would like to know this too. If they don't grease them then my next Prusa(s) would have to be the kit again.

I purchased an assembled printer, because I wanted to finally own a printer that didn't need tinkering.  It had bad, loud bearings, and Prusa is sending me replacements.  The moral of the story here is that the preassembled printers don't (as far as I can tell) come with bearings that have been cleaned and greased.  My hope is that they just had a bad batch of bearings, and the replacements they send will all fit nicely and be quiet.

Grease

You may have to grease the bearings.  I did.  

RE: My assembled printer did not have greased bearings

"My hope is that they just had a bad batch of bearings, and the replacements they send will all fit nicely and be quiet."

Why Prusa doesn't properly lubricate the bearings is beyond me. It's annoying for the customers, because repairs already have to be carried out on a new device, which also implies time and work.

wbr,

Karl