Prusa i3 MK3 - Cooling with a view

by jltx Dec 31, 2017
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I modified the new R3 version of the MK3 extruder cover, adding fan supports. https://www.thingiverse.com/LaserFlyer73/designs

Thanks, I'll give it a try because the stock shroud is pretty bad sometimes.

Hope it works out. This solution was always a struggle due to highly constrained area to work with. If you want truly superior part cooling and visibility (along with improved print quality and more) I’d recommend skelestruder. I have new dozuki instructions up. Check it out.

Can you make a version that fit on this https://www.thingiverse.com/thing:2843264 ?
Or upload the raw files, then I can try to edit it?

Revised MK3 Extruder and X Carriage
by vekoj

I uploaded the step files so anyone can mod to fit their needs.

Thank you.

Hi together,

I quickly made a new heated bed assembly that fitts to the beds with screw terminals. It‘s total flat on the top side. I've also extended the cable-guide at the back. I attach the stl-files as well a picture...

The two screws that held the pieces together are mounted from top to bottom...


BigAl1410 - the bed cover you uploaded doesn't work with this thing - it is too tall.

In my case it fits perfect. If the nose touch the bed there is still a gap of about 2mm between the cooling and the cover. Hmmm.

Ahhh. I forgott that I've changed the screws of the terminals to flat-head screws. Sorry! Attached I have a version that allow the terminal-screws going through.

Another important thing: Please mount the cable shoes that the higher part is facing down. I've a print running at the moment but later I can add a picture...

Thanks. I'll take a look.

No Problem. If you like, you can add the files...

This is great, love seeing the nozzle in action!

What if instead of the air looping around the back it had "Y" at the fan, air going down to left as is, the other duct travels just below fan to connect where the JLTX letters are? This would remove the requirement of messing with the heated bed assembly. I took a stab at this, but my 3d cad skills aren't quite up to the task.

Best way to learn CAD! Not to discourage you, but I looked at this early and there are still challenges. Airflow at y is uneven unless you completely remount fan, y itself blocks a lot of view unless way high, I wanted airflow from all sides but to reach anywhere near the rear portion, you are over the bed pins and cover. Take a look. It’s a highly constrained problem.

Thanks for the response!

Thanks - this is an awesome design and one that should have been incorporated into the printer from the start. Having to peer under the factory shroud is not ideal. I wish I could use it as is - but my bed has the screw terminals so it hits even the lowest profile terminal cover out there. I guess the back end of the shroud could be adjusted to clear the terminals, but it may not work with the current design. Still, I printed this to get an idea of how it works. This seems to be the only part Prusa prints in ABS, the rest being PETG. So I tried ABS and also had rough results on the overhangs. The supports you built-in are great! Some sanding cleaned up the roughness just fine. The back support clip is too small. The loop part on the shroud is too small and fragile. I think it needs a little more material at that area. Thanks again for this design. Very nice job and I look forward to the update!

Can you test the new cover I added? I don't have this bed type to test the fit. It's not very creative, but it might work. I suspect the screws are still too tall. let me know

Yes, just tested both versions and the stock M3 socket screws still are too tall for the new version of the cover. Using the button socket will totally eliminate interference problems and I can confirm they fit under even the 1st version of your terminal cover. However, in addition to switching to button socket screws, I also need to remove the plastic terminal shrouds and replace with lower profile heat shrink tubing. The plastic shrouds are in the way of fitting the terminal cover now. So, a little rework of the wiring and all fits quite nicely. Printed in ABS, there doesn't seem to be a need for the rear support yet, either. But, I think a great place to insert a support without affecting airflow would be to put a small tab that would be inserted between the Noctua fan and the hot end body. That would really work well I think.

good news about the button heads. Surprised that fits under the 1st version. It doesn't look like it is sitting quite flush. I would expect the new one to fit better, but I could back off on the recesses.

Thanks! I'll print and try. However, I can tell you that it will likely not work. There is less than 1mm between your shroud and the top of the standard screw heads. So even with the thinnest layer over the terminals, the terminal cover will likely contact the shroud. However, if the standard socket head screws are replaced with button screw heads, a lot of extra space can be gained. With the stock M3 socket head screws, the top of the head sits 4.36mm above the surface of the bed. By switching to shorter M3 button socket cap screw, the top of the screw head sits only 2.75mm above the bed surface, saving 1.61mm. That would allow for plenty of room. I'll try printing both versions and let you know. Attached are images of the screw heads - button on left, standard on right.

They must be using new parts to fit this, because the old ones won't. But those are not yet on GitHub so I'm guessing.

I am getting terrible results printing on the prusa i3 mk3. For some reason the supports that are included leave the surface extremely rough in those areas. Any ideas? I really like the design and heres to hoping it helps :)

I have tried to use with supports and without... no luck

Thanks in advance

This is on the main throat? It should just be cosmetic and not affect functionality. You can add your own supports in meshmixer, for example. I don’t recommend slic3r supports because it builds them into all the air ports.

Design looks good and its a clever idea to turn the fan.

But what I dont understand: how do you change your nozzle wihtout removing your shroud? You cant reach the hotend with a open-end wrench as far as I can tell.

Because I am looking for a quick way to change the nozzle without removing the shroud every time. Or at least it should have a quick release mechanism.

Easiest way to change a nozzle doesn't need a wrench at all. tinyurl.com/easynozzlechanges

Wow nice! Didn't know that. Will try if this way. Thanks

Exactly. Good write up. I just add the pliers because the heater block wants to turn a little sometimes. I use this to minimize torque since it just uses fingers. Also fits under easier without having to raise Z all the way.


Good question. I use the needle nose pliers to hold the heat block while it use a 7mm socket on the nozzle. I don’t have to remove any parts beforehand which was one of my goals. I haven’t used a box wrench but I see your point about little room.

Ah I with pliers, of course. Will try that the next time and then consider printing this when it works fine with pliers :) Thanks!

I don’t over tighten the nozzles and it works fine with pliers. It shouldn’t take much torque when heated. Check e3d for specs


Is it really necessary to "replace factory heated cable cover with the lower profile one supplied here"?


Yes. Very easy.

What 'extruder cover' mod are you using, I don't recognize the screw hole you use for the sock holder?

See construction section:

"get this part from my laser mod project"

Does this cooler setup cause interference with the printer frame since the fan sticks out so far?

That would be terrible. No. The fan is far in front of the frame.

Excellent! I just had to ask since some of the things I've printed off thingiverse have me scratching my head at their design. I'm going to give your cooler a shot -- looks awesome.

There are caveats, like removing for full XYZ calibration. The rear can rub on the bed pins when the steel sheet is not in place. Has not been an issue for me.

Do you think it would be a good idea to "notch" the back of the nozzle si it permit a full XYZ calibration without interference ?

I looked at that but felt it would eat into precious air channel capacity. It also makes for a more challenging print since the bottom would not be flush. I have yet to do another XYZ cal after the first one so this has not been a problem for me.

Can you share the STEP version without supports please? I'd like to replace the inductive sensor with a BLTouch, but the hole is too small for that....

Can you include some pictures on assembly? Thanks!

What would you like to see? The first picture shows the two screw points on the extruder cover. The third pic shows clip in the back corner. There is not much to it. The assembly instructions describe how to do it. Is something not clear?

Somewhat lol. I would love a quick video even of the assembly. I think maybe part of it is the words you use. You keep saying to replace the 'Nozzle', and I am not sure why I would need to remove my nozzle to replace the cooing shroud?

You are right. That wording was awful. I replaced "nozzle" with shroud to be more clear and differentiate from the actual nozzle. Thanks for pointing this out.

The part I am confused about is two parts:

  1. Where does the part " Brace V4" come into play?

  2. You have this section in the install that talks about installing a new extruder cover, but I do not see that part in the thing files.

[Save this step until you are satisfied with new shroud, and it is optional, but adds garter screw; get this part from my laser mod project]. Note when removing extruder cover you may find it stuck. This is due to screw from back side tapping in. You can pry off but be careful. Bonus is this should be the last time you remove it. New cover has clearance built in and installs exactly like original.

both are optional. I removed the brace when I realized it wasn't needed, but some people wanted it back. It screws in the upper hole on extruder and fan. The other part is found in my other project. I will change that to a link since it seems hard to find for some reason.

Nice. I had a feeling I knew what you meant, but I wasn't 100%, and it does sound a little more complicated than I thing it might actually be... I still think a quick youtube video would be helpful lol. I may just have to print the parts, and attempt it. and maybe make one as I stumble through it. If I do I might send you the link and you can post it to the thing if you like it :)

2 questions:
1: would you be willing to add the bracket back to this thing? I realize it might not be strictly necessary, however I for one appreciate the additional rigidity
2: Prusa just recently deployed a new heatbed cover, which is much more securely attached. https://github.com/prusa3d/Original-Prusa-i3/blob/MK3/Printed-Parts/stl/heatbed-cable-cover.stl . Might be worth a refactor.

  1. Yes, sorry about that.

  2. Yes, done. low profile version added. Need spacer for screw that goes through heatbed.

w00t! Danke my friend!

Gern geschehen

FYI I uploaded a new version, V1.1. I tweaked the screw holes on the top piece and repositioned so the print on same plane.

Okay, dumb question. I really like that socket wrench knob. Who makes it, or where did you get it?

It says Kobalt which I think is Lowes. It's handy. <-- pun

Hi there. I really like your intake tract although I'm convinced that the airstream would benefit from having something in the middle so the air doesn't hit a flat thing. This is the concept I have in my intake tract.
Anyway, I have a question. Do you believe that adding a spin to the air prior to entering the actual fan is beneficial to the airflow in this type of fan? And why?

I'm testing different intake designs. There are Venturi vortex type solutions in commercial use that are designed to give a slight boost (trucking industry, etc). I don't have a fluid dynamic simulator so honestly it is trial and error. The impeller rotates counter-clockwise so I am trying to pre-bias.

Man! With a bit more tweaking, you could pretty much make it a 360 degree cooler! That would be awesome!!!

Not exactly as is, needs some tweaks to fit that extruder. Once I get this dialed in, I can look at an MK2 version.

Will it work with a Prusa I3 MK2S?