fighting blobs-of-death: replacement extruders for Prusa i3 MK3(S, S+)??

[Justin Schmidt]

Hey Makers!

I have a Prusa in our makerspace that gets a lot of use by busy MIT students. The result is too many blobs-of-death that can only be remedied by tearing down the extruder and often I need to replace the entire hot end.

I did some quick searching, and it looks like most of the upgrades out there won't make it any easier to rebuild/replace parts or recover from bad blobs. Have any of y'all replaced your Prusa extruders? Anyone in a similar boat got any other suggestions?

Justin Schmidt

Instructor

K-12 Maker Lab | MIT Edgerton Center

Email | LinkedIn

[Chris Bruce]

My Mk3S+ with Revo makes things quite a bit easier, depending on how bad the blob is.  The key is that I don’t have to unwrap the wires all the way back to the control box.  

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[JD Pirtle]

With Prusas I usually increase the extruder temp beyond the recommended temp of the material I’m using (usually PLA), expose the filament intake into the extruder, then use a nozzle needle to slowly push any blockage out. This works on Minis…not sure which model you all use. I started doing this in 2013 with the infamously bad Makerbot Replicator 2 extruder/nozzle issue and I find it works on most FDM printers. 

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[Justin Schmidt]

Yup great advice for clearing clogs. I have problems with big blobs of melted filament oozing into the extruder body, caused by students in a rush who have iffy designs or bad bed adhesion (dirty plate, etc). Here's the current mess:

Justin Schmidt
Instructor

K-12 Maker Lab | MIT Edgerton Center

Email | LinkedIn

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From: k-12-f...@googlegroups.com on behalf of JD Pirtle
Sent: Tuesday, January 28, 2025 2:34 PM
To: Chris Bruce
Cc: k-12-f...@googlegroups.com
Subject: Re: [k-12-fablabs] fighting blobs-of-death: replacement extruders for Prusa i3 MK3(S, S+)??

To view this discussion visit https://groups.google.com/d/msgid/k-12-fablabs/37F2FC6C-D632-44C0-9189-AF70CFA5629E%40gmail.com.

[JD Pirtle]

Sorry, now I get the clog vs blob distinction…that's the biggest blob I've ever seen on a printer nozzle. When I’ve been in a similar situation with students rushing their prints, I have asked myself which is more work for me: repairing/cleaning up their mistakes or starting all prints myself. What ended up working is requiring students to repair what they break, which led to fewer issues and maintenance over time. 

On Jan 28, 2025, at 1:47 PM, Justin Schmidt <just...@mit.edu> wrote:

Yup great advice for clearing clogs. I have problems with big blobs of melted filament oozing into the extruder body, caused by students in a rush who have iffy designs or bad bed adhesion (dirty plate, etc). Here's the current mess:

<image.png>

[KRISTIN BURRUS]

If you keep having the same problem and filament is leaking above the nozzle, it may be coming from between the heat block and heat break.  I have also had the PFTE tube not inserted all the way, and it leaks from there. Here is a guide that might help https://help.prusa3d.com/guide/how-to-replace-a-heatbreak-heatsink-heaterblock-mk3s-mk3s-mk2-5s-mmu2s_16104 and https://help.prusa3d.com/guide/how-to-replace-a-hotend-mk3s-mk3s_161575#161802 Good luck.

[Melissa Anthony]

I agree with the suggestion to switch to a Revo. The Revo Six is a solid metal piece like the nextruder so it can't leak from the between the nozzle and the heat block, which is the most common cause for blobs in my experience.

I don't have blobs with them, but occasionally I have underextrusion, I think from heat creep.

It's an easy switch. https://e3d-online.zendesk.com/hc/en-us/articles/4410028113169-Revo-Six-Prusa-MK3-MK3S-MK3S-upgrade-guide

Melissa