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MK3S print fan shroud causing 'blob of death'  

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Frank
(@frank-8)
Trusted Member
MK3S print fan shroud causing 'blob of death'

I recently upgraded from MK3 to MK3S with it's new print fan and print fan shroud.  After several successful PLA prints I did a long (2-3 hours) print while I was away from the house, and when I came home I found the dreaded 'blob of death' stuck to my hotend and extruder assembly, and everything else within 2 meters (well, not quite, but you get the idea).  After several hours of work with paint stripper blower and dental picks, I managed to recover without fatally damaging the thermister and/or hotend heater cable.  However, after this I continued to have part detachment issues that I finally traced down to the print fan shroud dipping below the nozzle and dragging across the print.  This eventually caused the part to detach from the print bed and stick to the nozzle, beginning the 'blob of death' downward spiral.

I tried printing another print fan, but of course getting a good print depends on good part cooling, which naturally depends on having that print fan shroud in the right place - catch 22! 

After closer inspection, I was able to sand down the existing fan shroud so it didn't break the plane of the extruder tip, and so stopped scraping over the part. After this I was able to print another fan shroud, so I may now be back in business.  However, I'm not impressed with the current shroud design.  Anyone else having problems with the print fan shroud?

TIA,

Frank

 

Posted : 27/06/2019 1:25 am
vintagepc
(@vintagepc)
RE: MK3S print fan shroud causing 'blob of death'

Yes, even my ABS one has started to droop a smidge. I've since switched to a skelestruder in the hopes it has fewer airflow issues.

Posted : 27/06/2019 1:44 am
Sembazuru
(@sembazuru)
Prominent Member
RE: MK3S print fan shroud causing 'blob of death'

I remember there was a thread and resulting file for reworking the MK3 part cooling fan using fluid dynamic simulations. Ah, I found the Thingiverse page:

https://www.thingiverse.com/thing:3249344

I'm not sure if he is planning on spinning a revision that will fit the MK3S extruder, but I did ask in the comments on Thingiverse.

See my (limited) designs on:
PrusaPrinters - https://www.prusaprinters.org/social/1448-sembazuru/prints
Thingiverse - https://www.thingiverse.com/Sembazuru/designs...
Posted : 27/06/2019 4:18 am
Frank
(@frank-8)
Trusted Member
Topic starter answered:
RE: MK3S print fan shroud causing 'blob of death'

Thanks - I look forward to a MK3S revision 😉

Frank

 

Posted : 27/06/2019 1:07 pm
Sembazuru
(@sembazuru)
Prominent Member
RE: MK3S print fan shroud causing 'blob of death'

I'm cross-posting RHD's response to my request on Thingiverse:

It is true that I cannot make a nozzle that suits all different variants of extruders.
In order for the nozzle to work well and get a good fit, I have to make a CAD model for each extruder so that I have a CAD model to work with.
It is a lot of work to do that and that is why I have waived some variants.

But when it comes to Prusa model S, I actually thought about adapting the nozzle.
I just haven't had time with this because I am now renovating our kitchen.
But give me some time so we'll see.

So, I guess the fastest way to get the part cooling fan duct adapted is to go over to his house and help him with reno his kitchen. 😉

See my (limited) designs on:
PrusaPrinters - https://www.prusaprinters.org/social/1448-sembazuru/prints
Thingiverse - https://www.thingiverse.com/Sembazuru/designs...
Posted : 27/06/2019 3:58 pm
PHerz
(@pherz)
Active Member
RE: MK3S print fan shroud causing 'blob of death'

FWIW, I have changed my Hotend to the Mosquito Hotend from Slice Engineering and (at no one's suggestion) I have done away with the fan shroud entirely. So, far, in the last week I have printed a lot of generic PETG and some PLA. With great success!  :}

Posted : 14/07/2019 4:29 pm
rick.j5
(@rick-j5)
Eminent Member
RE: MK3S print fan shroud causing 'blob of death'

I don't know if it was the shroud or not but I've removed my Mk3S upgrade now as I simply couldn't get it to behave. I certainly had drooping issues with the lower edge of the heatsink surround.

On the plus side I decided to go the whole hog so there's a standard E3D heatbreak turning up next week, a Bondtech extruder upgrade, and some assorted spares from Prusa.

Posted : 19/07/2019 11:16 am
Frank
(@frank-8)
Trusted Member
Topic starter answered:
RE: MK3S print fan shroud causing 'blob of death'

No problems for me after printing/installing a new shroud. This time I took the precaution of printing a second shroud right after the first, so I can replace it (and print a new one!) immediately if I see any sagging.

Posted : 19/07/2019 12:20 pm
RH_Dreambox
(@rh_dreambox)
Prominent Member
RE: MK3S print fan shroud causing 'blob of death'

So, I guess the fastest way to get the part cooling fan duct adapted is to go over to his house and help him with reno his kitchen. 😉

Thanks @sembazuru, you are welcome to help in August when the new kitchen benches arrive 🙂

I have done some tests on a new fan shroud which I call RHD C-S. Unfortunately, it turned out to be very difficult to convert the C-nozzle to an S (C-S).
Prusa has placed the fan so close to hotend that it is almost impossible to distribute the air flow well in such a short distance.
There may be two solutions to this.
1. Move back the tilting fan 10-12 mm to extend the air ducts.
2. Install the fan vertically and design it as my Bear fan shroud.

Someone who has more suggestions?

Bear MK3 with Bondtech extruder...
Posted : 19/07/2019 12:42 pm
--
 --
(@)
Illustrious Member
RE: MK3S print fan shroud causing 'blob of death'

Not optimal from a multipart print capability but rotate the fan so the nozzle and flow is already horizontal: motor shaft parallel to the bed, blades perpendicular.  It increases the extruder footprint, but helps with the energy aspects of keeping the air moving in the desired direction and no 45 or 90 degree bends to get the air into the shroud.

This post was modified 2 years ago by --
Posted : 19/07/2019 3:29 pm
RH_Dreambox
(@rh_dreambox)
Prominent Member
RE: MK3S print fan shroud causing 'blob of death'

It was a good idea!
I think you mean something like this?

 

Attachment removed
Bear MK3 with Bondtech extruder...
Posted : 20/07/2019 12:22 pm
DrKenB
(@drkenb)
New Member
What is a skelestruder?

I'm new to 3D printing, and even newer to Prusa (my first printer was a Chiron).  So please forgive me for asking, but what is a "skelestruder"?  I did a search on Amazon and came up empty-handed.

Posted : 23/10/2021 11:37 pm
JoanTabb
(@joantabb)
Moderator
Skelestruder

Skelestruder is a community design for a replacement extruder, for use with the Mk3 series of Prusa Printer, 
It was designed to isolate motor heat from the extruder hobbed gears, and introduces a 3:1 step down gear ratio that enables use of a lighter stepper motor in an effort to reduce ringing and possible increase maximum print speed. 

https://www.thingiverse.com/thing:2845416
you are unlikely to see it on Amazon, as it is a printable item

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 24/10/2021 7:57 am
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