MK8 Extruder Fan Duct & Print Cooler

by apexio, published

MK8 Extruder Fan Duct & Print Cooler by apexio Oct 26, 2012


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This is a fan duct for the MK8 Extruder. It's purpose it to cool extruded materials thereby significantly improving print quality. Especially small prints and prints with sharp corners.

Ever have portions of your print rising up higher than the rest of the layer? This is the cure.

Designed from scratch in Tinkercad to be compatible with Emmet's Minimalistic MK8 Extruder.


Derived from kommisar's MK7 duct.


Please ready step 6 carefully. Failure to do so may damage your Replicator.

1) Print duct. I used 15% infill, 0.2mm layers, 1 shell. No Support, No Raft. Make sure you have a sticky print bed and that your nozzle is nice and close to it.

1.5) Recommended: Turn your printer off until step 9.

2) Unbolt extruder fan and heatsink. Take off the heatsink and set the old spacers aside.

3) Loosen the two bolts on the plastic piece that holds the extruder wiring harness and filament guide, on top of your extruder. Loosen them until they're about to come out.

4) Install heatsink into the duct. It goes in the side with the depressed area - not the flush side. Don't insert the fan or bolts yet.

5) Hold the heatsink in place while you slide the assembly into place on the extruder. You will probably need to tilt your extruder motor shaft upward for the parts to fit into place. At the same time, also lift up on your filament holder / wiring harness holder to get the edge of the heatsink under the lip. This step is easier done than explained.

6) With the new part in place, and using your HAND, move the entire extruder down the X-axis guide rods, all the way to the right. The arm on the new part needs to press the endstop button on the circuit board. You will hear it click. If your rep is on, a red light too. If it does not contact the button, this part will not work and trying to use it will probably break something.

6) Gently tighten the two bolts for the wiring harness and filament guide. They should not be very tight. You want the wiring harness / filament holder able to move a little.

7) Reinstall fan and bolts. Make sure fan is moving air toward the extruder (label facing extruder).

8) Confirm the heatsink is in contact with the aluminum heat transfer block that connects the extruder motor. Confirm the duct is not putting pressure on the X-axis guide rods.

9) If all is well, adjust your X-axis home offset. You can do this by running a calibration script or decrease the X offset by ~16.5mm. In ReplicatorG go to Machine -> Onboard Preferences -> Homing/VREFs -> X home offset. Do some math. Commit. This step is needed because you altered the home position of your extruder by ~16.5mm by installing the new duct :)

10) Enjoy! Post a picture if you make one.

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can you make one for makerbot replicator 2 ???

but doesn't this mean you have to run 100% fan all the time, since you're cooling both your nozzle throat and cooling your platform?

End result being, even PLA can warp with a fan in the first few layers. then your nozzle contacts supports, or walls and your print is ruined.

Maybe it's warmer, less voluminous air than I get from my filament cooling fan.

is this to add extra cooling

RepG might not be setting the value on your mightyboard. Try using the onboard controls to verify the X offset has been changed. Utilities -> Home Offsets -> X Offset -> 135.490mm. You can also modify it there.

I'm on firmware 7.3... I don't seem to have a "home offsets" menu. There's a "home axes" menu under "utilities", but it just sends it "home", doesn't let me adjust anything. What's your firmware? thanks!

I'm on 7.3 (sailfish). Keep looking, it's in there.

Ah, I'm not on Sailfish, stock Makerbot firmware. Maybe it's time to upgrade ;)

Definitely time to upgrade.

Successfully printed this out, but I can't get my rep1 calibrated afterwards. Feel like I'm missing something fundamental: I measured the gap with my calipers: yep, about 16.5mm. Just like you said, in the repG ctrl panel I modify the x home offset. Honestly I wasn't sure if I should add or subtract the value, but here's the thing: Changing that value makes no difference to the machine: Each time after I set the value (to either 135 or 168, given a base value of 152), I do a reboot, confirm the value was set, and print: every time, it starts printing off the left side of the build plate based on the current missing offset value. However, via the repG ctrl panel, if I say "center x" it goes to the exact middle of the plate (based on a current value of 135). If you could confirm if the value should be added or subtracted would be helpful, and any other advice to get it re-centered. What am I missing here? :) Thanks!

This is very clever - using the existing fan's air flow is much simpler than adding another fan. No added cabling, no buying another fan, etc.

But is cooling the plastic right out of the extruder a good idea for both ABS and PLA? For PLA you certainly want to cool off the plastic as soon as it's printed, but I've always heard that for ABS you want to keep the ABS warm (by closing the sides, using a heated print bed, etc.) to keep it from warping. If this gives improved PLA prints but worse ABS prints, that would mean swapping it in/out when changing print materials, which would be a lot of work. Or does it turn out to work well for ABS as well?

 I use it for ABS.   I use it in an enclosure and don't get warped parts.

It really only cools the top layers faster than usual - not the lower layers, which are the ones that would cause warping if cooled.

 I was wondering on how it would perform with ABS.
I'll put this on soon, as I have had issues with
steep angle edges curling. This could improve the prints.

Is this compatible for Dual Emmet's Minimalistic MK8 Extruder on a Replicator1 ?

It's only for a single extruder.  However, it can be easily modified for a dual setup.   http://tinkercad.com/things/gJsUvBNIGqotinkercad.com/things/gJsUvBNIG...

Tweaked, printing now. I'll share here as soon as I verify that it fits.

If your teaked version is for the dual and your print/version works this would be great. :) Look forward to your results.

It's http://www.thingiverse.com/thing:33254http://www.thingiverse.com/thi....

Basically I copied it in TinkerCAD and clipped off one of the two vents, then mirrored one copy.

Dual mk 8 extruder fan duct and print cooler
by laird

This is very impressive, love the design