Catastrophic MK3 failure: hot end clogging up and ripping off cable during PETG printing
 

Catastrophic MK3 failure: hot end clogging up and ripping off cable during PETG printing  

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Refsvik
(@refsvik)
New Member

Hi,

I have been happy with the MK3 kit that I built in the summer of 2020. Now, the hot end has clogged up during printing, and grabbed one of the thin cables and ripped it off.

Should I replace all the caked up parts, or should I upgrade to a MK3S? How do I proceed from here? Is a silicone sock the solution here, or is there another fix?

Sincerely,

Kjell Are Refsvik

Norway

 

Posted : 04/04/2021 9:05 pm
Baklin
(@baklin)
Estimable Member

MK3? Looks like a MK3s already to me. Atleast looking at the angled part cooling fan.

 

You have taken it apart quite a bit already.

I would go on a little further so you can take out the complete hotend. 

 

That way you only have to deal with metal parts. The thermistor needs to replaced anyway.  If you are lucky you can remove the heater cartridge. But if the wires are damaged if is a good idea to replace that too.

If you have a heatgun you can than heat up the petg mess and remove it.

 

Normally the advice with a blob like this is: heat got you into this mess, heat will get you out of it.

 

But with the broken wires you can use the printers heater to help you.

This post was modified 3 weeks ago by Baklin
Posted : 04/04/2021 9:32 pm
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fuchsr
(@fuchsr)
Honorable Member

I would consider that far from a catastrophic failure. If you have a heat gun, you should be able to melt and then scrap away most of that filament. The thermistor (thin cables) costs next to nothing and can be easily replaced.

Would a silicone sock help? In a sense, but you could still clog up things to the point that removing the sock might rip off the thermistor or heat element cables. Better to figure out why you had this mess in the first place. 

Upgrade to a Mk3S+? Depends. Personally, I would probably look at this mess as a divine intervention to make me upgrade and get all the improvements they added to the machine... On the other hands, if you're happy with your Mk3, the thermistor replacement will cost you probably less than $10 and is easy, whereas the upgrade will be a lot more expensive and a lot more involved. 

Posted : 04/04/2021 9:40 pm
Refsvik
(@refsvik)
New Member

@baklin

Thank you for responding, and yes - you are of course right. This is a i3 MKS3S. I am just about to find and turn on my heating gun and take out the hotend to clean and repair it. 

Posted : 05/04/2021 10:16 am
Refsvik
(@refsvik)
New Member

@fuchsr

Thank you for responding. Yes. want to repair the things that are broken (as cheaply as possible) and maybe do a + upgrade later on after identifying the real problem. I think I may have a z-height that is too low and that is causing some of these problems. I need to do more research on how to reduce the amount of boogers and other problems I can observe while timelapsing a normal print:

I agree, a thermistor and a silicone sock is perhaps where I will begin and take it from there. Thank you once again for responding during my time of despair. 

Posted : 05/04/2021 10:21 am
karl-herbert
(@karl-herbert)
Illustrious Member

@refsvik

The Pinda V2 runs great on the MK3S - no need to switch to the SPinda. You could possibly reprint the fanshroud when the printer is running again. If you order a thermistor, I would also order a heater cartridge and possibly a front fan. These are wear parts that can quickly become defective. If the heatbreak is bent (happens easily when disassembling the hotend), I would also order a replacement.

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 05/04/2021 2:29 pm
Laura F Farrell
(@laura-f-farrell)
Trusted Member

Should I replace all the caked up parts, or should I upgrade to a MK3S? How do I proceed from here? Is a silicone sock the solution here, or is there another fix?

A: I think your question really is - what do I need to replace?

From the photos, I can see that the thermistor is destroyed. The nozzle, heater element and the heated block are all caked in filament. It looks like the shroud for the fan also.

So easiest thing to do is warm up the block with a hairdrier and see if you can screw out the block from the heatbreak. If you can do this hopefully you can replace only these parts or maybe less!

It might be possible to warm up filament enough to "unpeel" it from the block and nozzle - this is ideal! But chances are you will get stuck.

So it looks like:

New nozzle, heat block, heated element, hotend sensor and if you are ordering from Prusa get the fan shroud (its very cheap).

Rough cost you are looking at about 40-50 euros worth of kit. It might be easier for you to simply buy the replacement hotend which is all of this plus the heatsink and heatbrake (which you might have been able to save?) If you cannot unscrew the block from the heatbrake then you might need the whole lot. I would say with a bit of gentle external heating you probably might be able to save the heatbrake and heatsink which will reduce the cost a lot.

Best of luck with it

 

Posted : 08/04/2021 2:30 pm
Refsvik liked
Refsvik
(@refsvik)
New Member

Thank you, Laura. I came to the conclusion that my employer could afford the cost of a completely new hot end and save me some time here, so that is what I went with as a solution. Thanks for your input, though.

Posted : 08/04/2021 4:50 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: @refsvik

Thank you, Laura. I came to the conclusion that my employer could afford the cost of a completely new hot end and save me some time here, so that is what I went with as a solution. Thanks for your input, though.

Having a spare, particularly for commercial use, makes sense. I'd still recommend keeping a few loose spares around in case swapping a part is faster:

  1. Heater block
  2. Heatbreak
  3. Thermistor
  4. Heater cartridge
  5. Nozzles

I keep these plus a hotend in my drawer. Don't forget some thermal paste for the top of the heatbreak.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 08/04/2021 5:46 pm
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