MK3S part melted  

RE: MK3S part melted

Correct photo 2

RE: MK3S part melted

It'd be nice to see the other side, the one that is being damaged by heat.

RE: MK3S part melted

The photos are of new parts, never used or installed.

RE: MK3S part melted

The image shows the sides that aren't affected, and don't show how the parts are different, especially on the side that eventually does melt.  Okay - second image shows it.  I don't see any major changes.  Did I miss something?  Isn't this part supposed to be better somehow?

RE: MK3S part melted

I don’t know, that’s why I was asking. The r5 version on github looks a bit different, but you have to examine that one closely to see the difference. There is more plastic around the bottom of it...fin and near the pinda probe holder, at least it looks like it’s thicker in those areas. An updated extruder cover part is also available there with the same characteristics. I would assume that the c2 version is a newer version than the r4 unless Prusa is just getting rid of older stock or had sent me that one by mistake.

RE: MK3S part melted

Here are the GIT links for people that want to compare. As @robert-c73 said, it's subtle:

• R5: https://github.com/prusa3d/Original-Prusa-i3/blob/MK3S/Printed-Parts/STL/extruder-body.stl
• R4: https://github.com/prusa3d/Original-Prusa-i3/blob/88e9bc3533ce454c670bbb7f308a832f3aaa784e/Printed-Parts/STL/extruder-body.stl

I need to rebuild my extruder this weekend so I was going to grab the R5s and print them, but looking at it I'm not sure how much that change will help. Especially since my issue is the fins and not the PINDA mount and that certainly isn't helping where the fins are melting (at the tips).

I guess I'll go ahead and print them anyway and see what I think while things are apart.

RE: MK3S part melted

I've thought about printing, molding and casting replacement parts in high temperature resin.  But I'm way too lazy for something crazy like that.  😉 

RE: MK3S part melted

The fins are supposedly reinforced on the r5 parts, so is the Pinda. Probably worth a try at least. I want to try them too but  can’t print with a broken off Pinda probe holder and right now z is calibrated about two inches above the bed and can’t go any lower until the pinda probe is either reattached or the broken part is replaced lol

RE: MK3S part melted

Printed a set of R5s for my rebuild this weekend. The fin on the cover (my melt problem) is clearly more robust. The additional material on the body is less obvious, but it is the kinda shiny bit next to the PINDA mount. It beefs up that joint a bit and makes the corner a 45 degree angle rather than a 90 degree angle that it was before.

Top = R5, Bottom = C1

Left = C1, Right = R5

Note that what looks like melt on the bottom of the old body is (I believe) the result of 24ish hours of printing with a bent heat break. Trying to clear a jam the nozzle wouldn't come off at 250 and the wrench slipped off the block 🙁 I'm actually impressed that other than needing to adjust my Live Z (the R5s were done before I did that) it was happily printing along.

RE: MK3S part melted

Cool

I started repairing my extruder the other day and since my printer was inoperable, I put in a new replacement R4 extruder body (actually, Prusa sent me one labeled "C2"), but then ran into issues with a broken heat cartridge wire and I inspected my hotend and discovered other issues with that too, so now I am awaiting replacement parts and if I am lucky, I may be able to print R5 parts next weekend and then re-do the extruder repair a second time to try those.  Good to know that they seem to be better.  I may just print one or two sets of the R5 ones when I can and then bide my time until something happens with the one I just put in.  3D printers can drive you to drink...one issue almost right after another one LOL

RE: MK3S part melted

Yeah I reinstalled the cover with the melted fin and just kept an eye on it rather than rebuild-print-rebuild. I did finally snip off the fin a day or two before I had my jam issue that snowballed, but I had gotten probably 1000 hours to that point and I wouldn't have torn it down yet just for that. Obviously if your PINDA mount is having trouble that's a bit different though.

Now I'm finding my old block is too gunked up to get the heater rand thermo out while cold. So now I have to jimmy things back together and try not to burn my fingers off while heating it up hopefully enough to unfreeze things...

RE: MK3S part melted

So during reassembly I am even more of the "not sure this is gonna help" opinion for the PINDA holder. In tightening the bolt for the PINDA there is still an awful lot of flex (like it would break during PINDA installation if you aren't paying attention.

I don't expect it to be any worse, so given that I didn't have PINDA issues I won't really be a good test subject on that issue. I'm also finally installing a sock as well which will change parameters for how heat gets around.

RE: MK3S part melted

I would try and install the heater block so that it's as far away from the Pinda probe as possible to try and prolong the life of the part as long as possible.  Prusa may have to reinforce that area a little more or better yet, have those parts printed in more heat resistant material than Petg.  I wonder if it would be even possible to make them out of Kevlar or some other very high temperature resistant material.  Some people are even using pt100 rated thermistors which facilitate printing at temperatures up to 500C. I wonder how petg parts would hold up under those conditions?

RE: MK3S part melted

You don't exactly have lots of choice about where the block is in relation to the PINDA. Unless you are meaning that they modify the body to move the PINDA further away, but I think I've read that you don't want them too far apart.

My guess is that they use/recommend PET-G as that is something that just about anyone should be able to print. There are people that print the parts in more heat resistant materials though. I believe you can even order them off Etsy and other places if (like me) you aren't setup to print such materials.

RE: MK3S part melted

I noticed on my printer that the heater may be able to be swapped around so that more of it is on the left hand side versus the right hand side where the pinda probe is.  That may or may not work, but it's an idea.  If there was a little more room, something heat resistant like kaptan tape might work near the Pinda probe holder too to resist heat better.

RE: MK3S part melted

Maybe a Silicone Sock?

RE: MK3S part melted

Thank you...my last post was only an idea in which I or anyone could try at their own risk...but I generally prefer to do things according to instructions.  I do plan on trying a silicone sock when I install my new hotend when it arrives.  The original extruder body on my printer survived more than four months and through hundreds of hours of print time, even though that was almost all PLA up until that point.  Nothing lasts forever of course.  Thank-you Joan for your suggestion.  You and everyone at Prusa Research have my respect.

RE: MK3S part melted

I just saw today that Prusa now has STL files for the newest extruder body and extruder cover parts for the MK3S.  The time stamps have been updated for all of the other plastic parts.  I wonder if other parts have been updated too, such as the heatbed cable cover with the screw pointing downwards instead of upwards too?  I will try these as soon as I repair my printer and can take the extruder apart for a second time to do this.

RE: MK3S part melted

Please let us know if there is anything different.  The same part melted on mine also.  

RE: MK3S part melted

I brought up this issue to Prusa Support and now they have a new part on the GitHub for you to print, it is labeled as R5. I just printed it, looks a lot thicker. Parts listed as extruder-cover.stl and extruder-body.stl

https://github.com/prusa3d/Original-Prusa-i3/tree/MK3S/Printed-Parts/STL