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Monoprice Ultimate Cooling Duct

by cnorth Aug 25, 2017
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Mounting suggestion: shift the cooling fan/duct assembly forward as Reflector has done in his fan duct designs.

Mount the fan using the rear screw holes on the fan and the front holes on the cooling block. Then use the formerly disused third screw from the original fan duct to secure the front of the duct. You'll need to use a washer and nut here since the screw no longer has the cooling block to pair with.

You don't loose any coverage of the workspace, because the edge of the duct remains in line with the nozzle. All we've changed is which edge is in line with the nozzle. I know the duct isn't 100% symmetrical, but the increased airflow should more than compensate. If it really bothers you, print a mirrored part.

Smart design indeed!
Just a question: is there a reason why the model is placed vertically?
Because otherways I would just lay it down... maybe the movements of the print head would be smoother?

It's just a direction discrepancy between the modelling program and what thingiverse considers upright. It's not supposed to be printed in the direction the models show. It's supposed to be printed in the direction the first main image shows.

I don't want two fans, and I want something small and lightweight, so I printed the short nozzle and found that it really flowed a lot of air, almost none of it in the direction of the nozzle. It blows air in a strong jet straight out centered about 1/3 of the way from the right side of the nozzle. See arrow drawn on bottom of printed part in my photo. I bought a hot wire anemometer from amazon and confirmed what a holding a small piece of thread in front of the nozzle showed me. So using only one mounting screw I rotated it almost 45 degrees to the left and the airstream is centered on the nozzle. Excellent results. I see 4 m/s air speed at the nozzle. It would be great if this was a two piece duct that you could rotate after mounting to direct the flow in the proper direction, or maybe add internal guide blades. I used an Orion OD4010-24MB fan.

There's a lot of factors at play here. But the main point is not to cool directly at the nozzle only (especially considering it can cool down the nozzle too much and cause flow problems). When your hot end is moving around, it's glossing over other areas of your print. The cooler the other parts of your print, the quicker the freshly laid layers cool down, making your print act as a heatsink. Airflow also draws in nearby air, along with removing any hot pockets of air in the general vicinity, which all contributes to cooling.

Another test you could do is take a temperature reading of the print itself, with and without this duct, and with the duct readjusted.

The main point of this open design is to ensure an open flow, otherwise you end up with too much air resistance and blow back up through the fan blades. That's why it's soo open ended, because you'll lose more flow by trying to funnel the air. If you funneling the flow (like how the stock duct does), you'll lose CFM. Funny enough, the fan you're using is only rated for 6 CFM, so to get 8 CFM is pretty good, especially considering it's not a direct flow facing from the fan. It might be a good idea to also test the default airflow of the fan without any duct to see what kind of losses there are to CFM by having a duct installed.

I will look into making another version off of this information though.

I have been using your base design for quite a while and it works well on large pieces. Smaller ones (miniatures) it does not work quite as well and I think it is because the main airflow never gets to any of the area being printed as miniatures are narrow and tall in shape. I am not sure what the best solution for that is other than swapping out circular ducts (which does not provide as much airflow as your design here which is actually an advantage to smaller pieces) and this one which is good at cooling layers as something prints and works well for larger terrain.

Wow, fast reply. Hey, nice design. It flows better than the others I've tried. I plan to cover all but the very tip of my nozzle with ceramic cloth insulation and kapton tape to keep airflow off of it. I am almost there, having wrapped the heat block. A few more layers at the bottom will leave only the conical tip of the nozzle exposed. As it is pictured, the fan had little effect on the extruder temp. I have an actively heated chamber, so I set the air to the desired temp for printed part, currently using 55 C for ABS. So when I blow lots of air, the part just gets to the desired temp faster, it never gets too cold. The CFM reading on my meter is garbage, as I just bought it that day and did not enter the duct opening area into the meter yet. Funny that it was accidentally that close. Without symmetric airflow around the nozzle, I get good results on only one side of the Benchy prints. Maybe blowing to one side would work if a small arc of metal or plastic was behind the nozzle to bend the flow back around the nozzle and really make a downward vortex of air around it. I have started on a duct drawing myself, but my drawing skills are weak and slow. My current thinking is a duct almost exactly like your design, modified to have a thin mounting plate at the top, like the stock duct has, except have the plate be a circular disk not square, with multiple sets of holes all around the disk, maybe every 10 degrees, so it can be bolted up at almost any angle.

Comments deleted.

So, which one of these three is the best one to print?

The one in the picture is the tested and original version. The angular version should perform the same in theory, perhaps a little better because it has some side coverage to help direct the flow, but it was mostly made for aesthetics so it looks more flush with the fan. The one with a bar going across was designed partially for aesthetics, but mostly to try to combat potential over cooling of the hot end by concentrating the flow at more of a downward angle. The performance is untested, but it could perform anywhere from the same, better, or worse.

If you don't really care about looks or testing, then the original is the one to go with.

I gave this a try and in complete candor, I wasn't really expecting much improvement due to the simplicity of the design ... but was really surprised just how much better it worked than the stock air director. This is a MUST have improvement for these printers. Simple, but elegant.
Thank you!

There are three screws holding the stock fan/duct in - are you just leaving the third screw out, or replacing it with a shorter one that still holds the fan?


Only 2 screws are needed.

Thanks, just fitted it! I tried printing with the stock one so I could compare it, but as it started the overhangs, something happened and I ended up with a mess of plastic (sadly I don't have a camera so not sure what).

Could this be related to the poor stock duct? I've swapped to yours anyway and started again. If the same thing happens, I'll have to set up a camera or keep an eye on it.

Cooling fan test torture test

So, the re-print I watched, and it came loose! I'm guessing that's what happened the first time. I'm retrying with glue stick (but may try a raft/brim if this is no good - it didn't have a lot of plastic touching the bed)

This thing worked-too well. With PLA it instantly improved prints, but with PETG it cooled the extruder down so much it gave heater errors.

Try lowering the fan speed for heater errors ;)

Thanks! I will try that with my next PETG print and post the result.

Is there a reason you went with a design that's still blowing to the side of the nozzle instead of directly at it?

There's a lot of factors going on as to why I settled with this design path, which is too much to go into here, but people have been quite pleased with the results of using this duct, including myself since I use it too. This has been on my printer for probably a year already.

Suggestions on infill %? I'm guessing you would have to print this with ABS or PETG?

I just do 1.2mm walls and 20% infill as standard for most of my prints, you could probably print it with single layer walls though since it doesn't really need to have any strength. Doesn't use much filament either way, it's not a big print. PLA should be fine, it doesn't come close to the hotend and has constant air flowing over it. You can always print it in other materials just in case, but I don't think it's necessary. I personally use this part on my printer with PLA and can't see how there would be any issues.

Do you still need the little spacers when you put this on? I ended up not using mine.

Sounds duh, but you only use 2 of the three spacers and screws right?

You should have the spacers in, otherwise you're blocking the intake of the fan blades. The axle cap of the fan will almost completely block the intake hole in the heat sink above, and with no side intake, the fan will not perform properly.

This shroud as simple as it is was the best one out of all your designs. Truly perfect and the difference from the original shroud is outstanding

Yep. What I would suggest is lowering your extrusion temps just a little bit. The D6's tend to run a little hotter than the temp sensor registers. Anywhere from 2c, 5c or 10c.

I'm really interested in seeing if this helps... :)