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Scratched rods from linear bearings  

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luke.m7
(@luke-m7)
New Member
Re: Scratched rods from linear bearings

I emailed support and sent them pictures of my scratched rods 5 days ago, and still haven't heard back from them. I'm glad everyone here is getting prompt service, wish I could say the same.

Posted : 18/01/2018 7:48 pm
stahlfabrik
(@stahlfabrik)
Honorable Member
Topic starter answered:
Re: Scratched rods from linear bearings


I emailed support and sent them pictures of my scratched rods 5 days ago, and still haven't heard back from them. I'm glad everyone here is getting prompt service, wish I could say the same.

I talked to them in chat and next business day the replacements were sent. -> Maybe go to chat and talk about your email. They normally try to reply to email within 2 to 3 days - so after 5 days, I would go to chat. Be kind, of course

Posted : 18/01/2018 8:00 pm
tomaz.z2
(@tomaz-z2)
Eminent Member
Re: Scratched rods from linear bearings

i had two reclamation for mk3. first was broken printed part. send pictures to info mail and get answer in 7 minutes ❗ (i checked later 🙄 )! which is really awesome respond for email and part was sent the next day. second was the bad linear rods. first day i exchanged few mails in one hour, send the pictures later the same day, get confirmation in the morning and the third day the rods was on the way .... i'm really happy with email support (not as much that i need it 🙄 )

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Posted : 18/01/2018 9:21 pm
RotaryDane
(@rotarydane)
Eminent Member
Re: Scratched rods from linear bearings


Magnet.. If they DO NOT attract, they are stainless and soft.. if they attract then they are hard.

It may be obvious, but just in case... This statement only applies to the two variants of Prusa-supplied parts - the wrong one (non-magnetic stainless) and the correct ones (steel with high enough iron content to be magnetic). The hardness difference is only known in this case based on Prusa's knowledge of the specs of what it shipped.

Will have to correct you on one point I am sorry. Both rods are in fact stainless steel, meaning that they inherently have a high iron content (steel is iron with 0.02-2.14% carbon added) but where they differ is that the soft rods most likely have a higher Nickel content, making them non-magnetic, where the harder ones do not and thus are magnetic and hard.
On the other points I believe you are correct though, that the magnet method is an easy way of telling if your Prusa rods are of the soft or hard type - If a magnet snaps to them they are hard, if not or it's weakly attracted then they're soft.

Posted : 18/01/2018 10:09 pm
john.n13
(@john-n13)
Estimable Member
Re: Scratched rods from linear bearings

Thanks. Not to split hairs, but I did not say (and was careful not to) that the magnetic ones were not stainless steel - they may well be - I don't know what they are. I believe however that they will have a greater iron content, imparting enhanced magnetic properties.

You misunderstood my point about the magnet determining hardness. Prusa has linked hardness with magnetic properties for the two materials under discussion, allowing the use of a magnet to determine which of their supplies is hard or soft. Magnetic properties are not determined by hardness nor dependent on it.

Posted : 18/01/2018 10:20 pm
devdoc
(@devdoc)
Estimable Member
Re: Scratched rods from linear bearings

I just finished up with customer service who treated me excellently, and with respect. I was asked to present a video evidence file to them, and upon review, they agreed to ship the new rods and bearing with my pending order. They did ask if that was OK with me first, and I agreed. I don't need to waste their money shipping something now when I will have something coming in a week or so and I have plenty to work on in the meantime, like building my other MK3. So I just wanted to share my positive experience with the team resolving my issue amicably. Overall A+ experience dealing with Joseph's support team. It would have been nice to have no problems, but that is unavoidable, and they handled it perfectly.

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Posted : 18/01/2018 10:21 pm
Dewey79
(@dewey79)
Honorable Member
Re: Scratched rods from linear bearings


Received my MK3 today. Rods are hardened. They won't be installed though as my Misumi rods and bearings should be received tomorrow and I'll build with those.

Steve, where are you ordering your parts from?

Posted : 18/01/2018 10:23 pm
luke.m7
(@luke-m7)
New Member
Re: Scratched rods from linear bearings


I talked to them in chat and next business day the replacements were sent. -> Maybe go to chat and talk about your email. They normally try to reply to email within 2 to 3 days - so after 5 days, I would go to chat. Be kind, of course

Thanks, I didn't even know the live chat existed. Apparently the chat app is being blocked through my company's internet. Just logged in through my mobile device, and was able to chat with support. They said someone else will email me with a response tomorrow, so the waiting game continues...

Posted : 18/01/2018 10:58 pm
RotaryDane
(@rotarydane)
Eminent Member
Re: Scratched rods from linear bearings


Thanks. Not to split hairs, but I did not say (and was careful not to) that the magnetic ones were not stainless steel - they may well be - I don't know what they are. I believe however that they will have a greater iron content, imparting enhanced magnetic properties.

You misunderstood my point about the magnet determining hardness. Prusa has linked hardness with magnetic properties for the two materials under discussion, allowing the use of a magnet to determine which of their supplies is hard or soft. Magnetic properties are not determined by hardness nor dependent on it.

I apoligize for any misunderstandings. English isn't my first language 😳

Never meant to say that magnetic properties are tied up on hardness or vice versa. Just that it's the prefered method to determine which rods you have.

Posted : 18/01/2018 11:14 pm
john.n13
(@john-n13)
Estimable Member
Re: Scratched rods from linear bearings

Hey, no problem from this end.
On the materials topic, I really would like to know the metallurgical and as-delivered physical specs of the two rod materials involved here and I wish that Prusa would share that information with us - or at least that data for the "hard" material they selected. It would greatly facilitate the specification/selection process for those of us that might consider replacing the stock items - rods and bearings - with our own choices and at our own expense.

Posted : 18/01/2018 11:36 pm
ed
 ed
(@ed-3)
Reputable Member
Re: Scratched rods from linear bearings


Hey, no problem from this end.
On the materials topic, I really would like to know the metallurgical and as-delivered physical specs of the two rod materials involved here and I wish that Prusa would share that information with us - or at least that data for the "hard" material they selected. It would greatly facilitate the specification/selection process for those of us that might consider replacing the stock items - rods and bearings - with our own choices and at our own expense.

We have a Niton XL3t at work though I'm not sure we can pull an accurate reading off the rods without grinding a bit off of the surface, ie chromed, and not sure if he can get a reading off of something so small. I'll pass one of the rods off to our NDE when they come in to see if he can get chemistry and a hardness reading off of rod without buggering it up for fun. Though I too already have new rods and bearings so I'm not too concerned.

Posted : 18/01/2018 11:46 pm
john.n13
(@john-n13)
Estimable Member
Re: Scratched rods from linear bearings

That would be great if you can pull it off. I'm retired and no longer have access to those kind of facilities that I can use at will...
If the hard rods are in fact hard chrome plated, it will be the plated surface that needs the hardness tester run on it. The chemistry is really only significant if the rods are not plated and have been heat treated to reach a certain hardness level - the hardenability of the material (and the heat treatment processing required) will depend on its chemical makeup and the target hardness.

Posted : 19/01/2018 12:00 am
ed
 ed
(@ed-3)
Reputable Member
Re: Scratched rods from linear bearings


That would be great if you can pull it off. I'm retired and no longer have access to those kind of facilities that I can use at will...
If the hard rods are in fact hard chrome plated, it will be the plated surface that needs the hardness tester run on it. The chemistry is really only significant if the rods are not plated and have been heat treated to reach a certain hardness level - the hardenability of the material (and the heat treatment processing required) will depend on its chemical makeup and the target hardness.

We have a Rockwell tester and I'm thinking he can hit the area of the rod where the zip ties go but to be honest I'm not sure if hitting such a small diameter will work, I'll leave that to the expert.

Posted : 19/01/2018 12:17 am
gibsonlpsl
(@gibsonlpsl)
Eminent Member
Re: Scratched rods from linear bearings


Do any of the rods on your MK2s have visible or obvious damage from the bearings?

Yes, the non-magnetic x rod has significant wear marks, while the other x rod has nearly none.

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Posted : 19/01/2018 7:17 am
gz1
 gz1
(@gz1)
Estimable Member
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.

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Posted : 19/01/2018 7:24 pm
Ken
 Ken
(@ken-4)
Eminent Member
Re: Scratched rods from linear bearings


I decided to take a look at my rods (even thought they are still in the box) and they do not appear blue..

They also have more of a chamfer at the ends, which on the video looks like the old (soft) rods..... But as a final test, I took a file to the end, and with a light stroke easily removed material.

Clearly mine are not the "hard" versions and I am going to try and get Prusa to replace them before I start my build.. I am not in the mood to build it, wait for the scratches and then do a rebuild when it happens.

I am not convinced they will help, but atleast I was honest and told the truth, where as I could have just told them that mine were scratched and used someone elses photos...

Lets see what they say....

Jon

Edit: I just did a quick test and slid a bearing back and forth at the end of the shaft a handful of times.. You can already see marks on the rods... Very fine, but they are there and permanent..,

Both Angus Deveson (Maker's Muse) and Thomas Sandladerer did live builds of the MK3 kit and (I think both) were given unhardened rods. Besides looking for scratches and using a file on the end of the rod they said it was possible to identify unhardened rods because a magnet wouldn't stick to them. They said that Prusa accidentally sent out a few kits with unhardened rods - though it appears that it was more than "a few". Mine are also unhardened. Note that Thomas S. (the more technical of the two) said that it will take a long time before the unhardened rods are sufficiently scored that it actually affects print quality. So I think you can go ahead and assemble your printer but hold onto the replacement rods for a later time when you need to make several repairs.

Thanks,
Ken...
Posted : 20/01/2018 8:25 pm
Pintie
(@pintie)
Eminent Member
Re: Scratched rods from linear bearings

"it will take a long time before the unhardened rods are sufficiently scored that it actually affects print quality."

depends on what "a long time" is....

my mk3 runns every day for 4 weeks now.
an you can realy feel the wear on the rods. so its starting to get play.

i will get the new hardend ones on monday. i hope this solves the Problem.

Posted : 20/01/2018 10:38 pm
Ken
 Ken
(@ken-4)
Eminent Member
Re: Scratched rods from linear bearings


"it will take a long time before the unhardened rods are sufficiently scored that it actually affects print quality."

depends on what "a long time" is....

my mk3 runns every day for 4 weeks now.
an you can realy feel the wear on the rods. so its starting to get play.

i will get the new hardend ones on monday. i hope this solves the Problem.

It would be interesting to know what print quality issues you start to observe and what the run-time of your printer is at that point.

Thanks,
Ken...
Posted : 20/01/2018 10:48 pm
Pintie
(@pintie)
Eminent Member
Re: Scratched rods from linear bearings

at the moment there are not print issues .... yet
i have about 300m and 6 days print time.

but the Y Axis allready has a little play. so i'm sure "long time" will be less than a couple of weeks.
x and z a visible but not as deep.

Posted : 20/01/2018 11:29 pm
Ken
 Ken
(@ken-4)
Eminent Member
Re: Scratched rods from linear bearings


at the moment there are not print issues .... yet
i have about 300m and 6 days print time.

but the Y Axis allready has a little play. so i'm sure "long time" will be less than a couple of weeks.
x and z a visible but not as deep.

I asked Thomas Sandladerer how long is a long time and here's his response: "I've been using cheap stainless rod (+ tons of grease) on my Mendel90 for probably thousands of hours without ever noticing a drop in quality. Yes, the rods had very visible wear on them and the bearings felt extremely loose, but with the profiles I used and the way the printer was built (very similar to i3), it never translated into worse prints.
Still, hardened rods are the more correct option to use with LMxUU and will work longer in more configurations."

Thanks,
Ken...
Posted : 21/01/2018 12:11 am
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