Re: Scratched rods from linear bearings
This is ridiculous. PR needs to get on top of this and FIX it.
This isn't a "supply" issue. It's not, "Oh, we got a bad batch of X".
It 's a DESIGN issue which is possibly just exacerbated by bad supplies.
What are you basing this on? From what I've read, it WAS a supply issue. Josef said they mistakenly shipped some units with non-hardened stainless rods. And they ARE fixing it...if you contact support and verify you got the incorrect rods, they send you replacement hardened rods at no cost.
I haven't heard anyone who initially got the correct hardened rods (or replacement hardened rods) say anything that suggests a 'design' problem with the rods or bearings.
Re: Scratched rods from linear bearings
First i want to say, that Prusa chat support is making a good job with this topic.
they wanted me to check my rods with a magnet. And send me new Rods, no questions asked.
That is not what i am used to with a lot of companies.
Print quality may not be affected immediately, But when there is play, there is a chance that parts get stuck.
i don't want to leave my printer unattended, knowing that the y axis can be blocked. (and i know from experience that this could haben when there is only little play).
Re: Scratched rods from linear bearings
Hi Guys,
This is all a bit worrying!
For the record:-
My Mk3 kit was shipped 12/01/2018
I've just finished building it and have printed the castle @ 100um. (11 hours??)
It all seems OK.
I've just done the magnet test:- The rods on my Mk3 are all magnetic but the rods on my Mk2S (May 2017) are not!
The rods on my Mk3 don't have chamfered ends but my Mk2S rods are chamfered. (This could be another way of confirming which factory they came from).
None of the rods on either machine are marked.
As far as lubrication goes: The bearings on both machines were pre-oiled. I have never oiled the bearings. I've just kept the bars clean.
It's all good here 😀
P.S. The print quality on the castle is awesome! 😀
Re: Scratched rods from linear bearings
I have a *factory built* Mk2S. It has done about 150 hours. All the rods are practically non-magnetic - stainless. The Y rods were quite badly scored. The X and Z rods look OK. I had decided to swap out the Y rods for IGUS AWMP rods and RJZM-01-08 (encased) bearings. I also have the IGUS rods and RJZM-02-08 (encased) bearings ready to fit on the X axis - just waiting for the MK2.5 upgrade kit. Incidentally, I chose to go ahead with the IGUS replacements despite the bad press because the bearing are successfully running huge distances in thousands of machines (not just 3d printers but lots of them as well). When I removed the old Y rods and bearings, the decree of scoring was remarkable - you could slide the bearings but they sounded horrible and you could not easily rotate them because the balls caught on the score marks. Everything has always been kept really well lubricated. I fitted the IGUS bearings and rods and discovered that despite the fact that they glide like ice-on-glass off the machine, when fitted they tended to bind a little towards the rear end of the Y travel. So, using precision parallels and my best vernier gauge, I checked how parallel the Y axis was - it was wider at the rear by ~0.05 - 0.07mm. 50 microns isn't much but it was enough to make the IGUS bearings judder and stick (individually they have a 50um tolerance). When I looked back at the old Y rods, they were scored more deeply at the rear than the front. Now I have made the rods as parallel as measurement allows, the IGUS bearings again run like ice on glass. I believe good LMUU bearings have a slightly lower tolerance than the RJZMs. So, check how parallel your Y axis is and/or it may also be worth bearing (!) in mind Tom Salanderer's advice and let one of the two bearings on the left rod have some freedom and I wonder if the change from zip ties to U-bolts has something to do with the problems as well as the use of the 'wrong' softer steel????:
"Linear ball bearings are also pretty sensitive to misalignment, which is why most carriages only use three bearings instead of four. If you mount two bearings in a way where they are not aligned or have no way of aligning themselves, one of the bearings will inevitably run noisier or even jam. So either use precise mounts or provide a way for the bearings to align, for example by using only one zip tie per bearing. "
Re: Scratched rods from linear bearings
Right. I too wondered if the zip tie was better. But the bearing alignment is highly dictated by the slot in the "frog" and I haven't had any issues. Of course this assumes the bearing casing is precise. But the u-bolt makes it easier for a user to over tighten and wreak havoc. Good time to highlight step 30 of the assembly instructions in case anyone glosses over it. Need to leave those Y holder screws loose until this:
IMPORTANT: proper alignment of the smooth rods is crucial to reduce noise and overall friction.
Ensure all M3x10 screws on Y-holders are released, so the printed parts are able to move.
Move the Y-carriage back and forth across the entire length of the smooth rods to align them.
Then move the carriage to the front plate and tighten all screws in the front-Y-holders.
Move the Y-carriage to the rear plate and tighten all screws in the back-Y-holders.
Re: Scratched rods from linear bearings
So, I finally got around to checking my rods. The neodymium magnets did not stick and I found significant scratches on the Y rods. My order was early, placed on 9/28. Support is sending out new rods tomorrow.
With all the complaints and moaning going in the forums, I feel compelled to say... Problems occur with every product and every company. How the company responds to these problems and remedies them should define their excellence. Prusa is and has proven their excellence. Anyone who does not understand can go demand more from somewhere else, IMO. They very likely won't get what they expect elsewhere either, but one day they will figure out the problem lies with their expectations.
Re: Scratched rods from linear bearings
What are you basing this on? From what I've read, it WAS a supply issue. Josef said they mistakenly shipped some units with non-hardened stainless rods. And they ARE fixing it...if you contact support and verify you got the incorrect rods, they send you replacement hardened rods at no cost.
I haven't heard anyone who initially got the correct hardened rods (or replacement hardened rods) say anything that suggests a 'design' problem with the rods or bearings.
There is this hilarious radio in GTA that satirizes rampant consumerism. Went something like, "My doctor told me that if I didn't upgrade my whatever product, I was going to die!" I'll try to find it.
I'll have to multiquote here. I'm basing it on this:
Right. I too wondered if the zip tie was better. But the bearing alignment is highly dictated by the slot in the "frog" and I haven't had any issues. Of course this assumes the bearing casing is precise. But the u-bolt makes it easier for a user to over tighten and wreak havoc. Good time to highlight step 30 of the assembly instructions in case anyone glosses over it. Need to leave those Y holder screws loose until this:
IMPORTANT: proper alignment of the smooth rods is crucial to reduce noise and overall friction.
Ensure all M3x10 screws on Y-holders are released, so the printed parts are able to move.
Move the Y-carriage back and forth across the entire length of the smooth rods to align them.
Then move the carriage to the front plate and tighten all screws in the front-Y-holders.
Move the Y-carriage to the rear plate and tighten all screws in the back-Y-holders.
This is what my problem is. The proper alignment of the smooth rods is CRUCIAL. A little too skewed and you get stiction/can't use Igus bearings/get bearings digging into the rods. Plus it affects print quality, bed leveling, etc. This one issue is responsible for the lion's share of what ails this printer.
But it's only crucial enough to blame the user or supply problems or whatever, it's not crucial enough to adjust the design to, you know, allow for tolerances and adjustments. If the rods were correctly aligned (which you'd think would be a reasonable ask in 2018) the supply thing would probably not matter.
Look closely at the design and ask yourself: does this design assume that everything is made and assembled perfectly, or does it allow for some errors to be compensated for?
Pick a part. Even better, pick a printed part, because you know those won't come out perfectly. So assume it comes out slightly wrong because you know PR isn't going to spend time finishing the printed parts to get them to spec -- too time consuming, so they just throw them into the printers/kits. Imagine it gets installed in a printer. How much slop can the design take from the printed part, and what mechanism is there in the design to account for it?
Re: Scratched rods from linear bearings
The proper alignment of the smooth rods is CRUCIAL. A little too skewed and you get stiction/can't use Igus bearings/get bearings digging into the rods. Plus it affects print quality, bed leveling, etc.
Yeah, we get that, that part makes sense. But back to my previous question...do you have evidence that there is a specific design flaw that prevents a user from properly aligning the rods if they take care in doing so? I'm genuinely asking. I'm getting ready to do a partial rebuild with new rods and bearings. If you have identified a specific flaw in the design that is actually the cause of all the rod issues as your previous post suggested (or more importantly, a remedy), I'd really like to know about it before I rebuild it. I think we all would. But I'll be glad if that's not the case.
Re: Scratched rods from linear bearings
Yeah, we get that, that part makes sense. But back to my previous question...do you have evidence that there is a specific design flaw that prevents a user from properly aligning the rods if they take care in doing so? I'm genuinely asking. I'm getting ready to do a partial rebuild with new rods and bearings. If you have identified a specific flaw in the design that is actually the cause of all the rod issues as your previous post suggested (or more importantly, a remedy), I'd really like to know about it before I rebuild it. I think we all would. But I'll be glad if that's not the case.
Let me reiterate. I apologize for not being clear.
Pick.
Any.
Part.
I was being quite literal. You can run the mental exercise on pretty much any part in the chain and run the thought experiment on it.
What if the bearing pockets aren't cut perfectly on the Y bed? What if the paint coating is a little thicker in one part of the pocket than the other? What if the U-bolt isn't centered perfectly on the bearing, or not the right pressure is used? What if the bearing thickness isn't exactly consistent? What if the cumulative error of all 4 different extrusion attachment points and threaded holes is too much for the bearings to handle? What about the cumulative error between all 4 different printed smooth rod holders that sit on top of the extrusions?
All you had to do was PICK.ANY.PART. And as I stated, the easiest parts to run this experiment on would be the printed parts, since you KNOW those won't come out perfectly.
And that's just the Y axis; this is essentially replicated across the entire printer, so I have a real hard time with you asking me for a specific example.
There's another thread started recently about the Z axis:
https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/fine-tune-your-mk3-z-axis-t13806.html
I think he's identified the problem and is going in the right direction, although he's missing a few things.
It's hard to imagine that these parts (the z axis mounts in particular) have reached 2018 where not only are they not being injection molded to cut down on turnaround time (it's really a stupid part to be printing), but they're still actually flawed in their design anyways.
2018. Think about it.
Trivia: how many of you have checked the planar flatness of your Y axis rods?
Re: Scratched rods from linear bearings
Another one here, for info. My Mk3 was ordered on 24th Sept and I tested the rods last night. Magnet no stick, incorrect rods. I spoke with support who asked me to send a small video of the magnet not sticking and my original order number and they will get replacements sorted. They also asked me to test all three axes so maybe there are some mixed sets out there? Anyway all my rods failed. Video had to go to [email protected]. Email and video sent, now awaiting acknowledgement / response.
Re: Scratched rods from linear bearings
Another one here, for info. My Mk3 was ordered on 24th Sept and I tested the rods last night. Magnet no stick, incorrect rods. I spoke with support who asked me to send a small video of the magnet not sticking and my original order number and they will get replacements sorted. They also asked me to test all three axes so maybe there are some mixed sets out there? Anyway all my rods failed. Video had to go to [email protected]. Email and video sent, now awaiting acknowledgement / response.
For what it's worth, I contacted Prusa Support about my unhardened rods on Jan 17th, they asked for how I determined that and video proof on the 19th, I responded with a video 4 hours later, on Jan 23 they agreed to send new rods/bearings but needed my order number, I responded with that information12 hours later, on the 26th I was informed that they were on the shipping list and I received them (in Denver) on Jan 31. Pretty decent turn-around as far as I'm concerned.
I verified that they're hardened using a cheap magnet. The small, round, flat ones that you can get in bulk at your work supply room for your office.
Thanks,
Ken
Re: Scratched rods from linear bearings
I have hardened rods, but my x and y have become scored due to the bearings I contacted support on Friday who told me to check all rods and bearings ,I said it was just the x from what I could see and that it was clicking and clunking as it traveled across, they asked for a video and pictures which I did , they said they would replace the set. I then noticed the left y rod had a groove appearing sent a follow up email saying the y was also affected but I’m concerned they are just sending the x axis set which is arriving Monday and I will have to hassle for them to post the y next week as I haven’t had a reply to that mail and it has been posted so quickly , I am now wondering if there are better bearings than stock
Re: Scratched rods from linear bearings
I am now wondering if there are better bearings than stock
This is rather widely agreed upon, and discussed at length in other threads. Search the forum for "MISUMI".
Re: Scratched rods from linear bearings
I have hardened rods, but my x and y have become scored due to the bearings......<SNIP> I am now wondering if there are better bearings than stock
Are you sure you're asking the right question?
Re: Scratched rods from linear bearings
12 hours in with my mk3 and the upper x rod has scoring. Customer support told me that if it isnt making noise and isnt affecting printing then don't worry about it.
I do worry about it and added a small amount of sewing machine oil. i also ordered my own replacement bearings and rod.
I definitely would lubricate they bearings
Re: Scratched rods from linear bearings
my mk3 kit was shipped with crappy non hardened steel rods from a mk2. try a strong magnet against each rod, if it barely sticks, you may have gotten the non hardened ones. a magnet should attach strongly to the hardened steel rods.
Re: Scratched rods from linear bearings
if it isnt making noise and isnt affecting printing then don't worry about it
Lame answer - basically means 'go away' - not what I'd call support. This was a big issue in the early days and support know it. This is as much crap bearings as rods - so change both, don't waste your time replacing one if you're not replacing the other.
The scoring you see is caused when balls slide instead of roll. Run the bearing on the rod, if it feels rough or lumpy or the movement doesn't feel smooth in the bin they go ...
Re: Scratched rods from linear bearings
Hi all, recently I started to hear a very loud noise from the Y axis so I took it apart.
I noticed that there are deep scratches on both smooth rods, and the bearings doesn't run run smoothly.
I tried to place a strong magnet on both back in february when I got the printer, and they are correctly hardened rods.
Is it possible that I originally mounted the Y-axis wrong? If I try to push a single linear bearing along a rod now that I have disassembled them there is a lot of friction, even at the beginning or in the end of the rod, where the bearing never reach when mounted on the printer
Re: Scratched rods from linear bearings
The Y-axis bearing mount with the U-bolts can be easily overtightened, leading to stuck bearing balls that are no longer rolling but sliding.
So yes, it is possible that you tightened the bolts too much, bent the linear bearing and scratched the rods.
In your photo it looks like the hardened layer of the rod actually broke away.
Talk to support if they can help you with new parts, or get them from a rod & bearing supplier. If you are in the US you are lucky and can buy high quality ones from Misumi.
Nevertheless, that U-bolt still needs to be itghtened very carefully. I recommend sliding the Y-axis assembly back and forth, and checking for play and friction. Just tighten the bolts until the bearings don't move any more when you try to wiggle. If you tighten the bolts just a little too much you can clearly feel the friction increasing.
Re: Scratched rods from linear bearings
The Y-axis bearing mount with the U-bolts can be easily overtightened, leading to stuck bearing balls that are no longer rolling but sliding.
So yes, it is possible that you tightened the bolts too much, bent the linear bearing and scratched the rods.
In your photo it looks like the hardened layer of the rod actually broke away.
Talk to support if they can help you with new parts, or get them from a rod & bearing supplier. If you are in the US you are lucky and can buy high quality ones from Misumi.
Nevertheless, that U-bolt still needs to be itghtened very carefully. I recommend sliding the Y-axis assembly back and forth, and checking for play and friction. Just tighten the bolts until the bearings don't move any more when you try to wiggle. If you tighten the bolts just a little too much you can clearly feel the friction increasing.
Thank you for your reply, I just talked to the support and they will send me new rods and new linear bearings. The wrong assembly of the Y-axis was likely the cause of the problem.