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msurunner

Hotend solution?

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Here's my thought, maybe someone has already tried it and it's not intellectually sound or it's already available and I just don't know it. What if someone created a fan shroud that cooled the part printed, as well as the PEEK part? Thus, we save on weight from snowygrouch's design (BTW, just got our first snow here in Billings, MT, USA), by keeping with a single fan. I have to think that by doing this, we could also turn the fan vertical and bring it closer to the hotend box, thus lowering the torque on the hotend assembly (I know it's not large anyways, but still). Thoughts? Anyone feeling ambitious? I might try modeling if someone's thinking it sounds like a legit idea...

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My answer is that I wanted to do that at first when I looked at the problem. However you need to think very carefully about the different cooling offered by "suck or blowing" of the air.

If for example you put some sort of reverse u bend inlet duct on the standard fan, to draw air

through between the aluminium plate and the wood...the trouble is that the air at the duct entry has

very low velocity, and hence no inertia. So it will follow the path of least resistance, and just be drawn

in from the sides (there are "4 open side slots" between the Alumnium plate and the wood).

If you blow air into that space, the air is already up to speed and so will be thrown forward and swirl

over the alumium plate and also hit the exposed PTFE.

These small fans have such pathetic pressure head, that athough you could make such a duct,

I would think your mass flow rate would be tiny. Too much pressure drop.

There is definetly a possibility to improve the design, and possibly a proper fan with some beef to it

could be substituted. But I would think that you would be much better making a duct with dual exits

than trying to draw through that gap THEN into a 90 degree bend THEN through the fan THEN into another

90degree bend.

I know now that even looking at the standard fan you can barely feel any good draught flowing through it

just as it is with one duct with a single bend.

So I think that a far better fan needs to be considered. However then you are looking at bigger windings....equals

more mass etc etc. But there is possibly something small. light and powerful available if you want to pay a bit more.

Or water cool it, but I am not very keen on the plumbing for that, or the potential for disasters in case of leaks.

Regards

Calum

EDIT:::

Looking at the printhead, I have been retarded. The small 40mm fan could in fact just it in vertically

between the Z height of the nozzle tip and x axis rod. Then I could have done a duct with a split exit, which

might have been able to do both part and printhead cooling in one. But experimentation would be

needed to size the top and lower duct exits depending on which needs most bias. Having the fan vertical

will really increase its flowrate due to lower pressure drop. Thus even this useless PC chipset fan might

do it....will do a new design ! :D Thanks for the suggestion.

This is an awesome list of fans>

http://www.performance-pcs.com/catalog/ ... ts_id=4544

RIght now the fan I have on the printhead gives 5CFM for 15 grams fan mass (+duct mass).

I have seen from a quick look, the "cooljag 40x20mm" which gives 17.8cfm for 30grams. Could be that

one of these instead of two fans, and two ducts would give a small mass saving.

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Haha, good, I'm glad you came to the same conclusion I was trying to get to. I was about halfway through your post and was trying to figure out how to better explain it when I hit your edit. Yes, my idea would be simply to have a smaller, second output in the shroud to the PEEK part. If we do lazy math and assume perfectly clean fluid transfer, you could theoretically take a third or whatever of the normal output, neck it down while diverting it to the PEEK, thus increasing its velocity and cooling ability, while still allowing for a large volume to cool the part being printed. I personally don't think there is a HUGE cooling need for the PEEK, unless printing slower speeds and higher temps (Exotic materials and/or ultra quality), but I think the more improvement we can make the better. Also, I rarely run my cooling fan at full output and it seems to have enough airflow that if amped up, I think it out to support a dual outlet... Let me know how your design is looking Calum and maybe we can collaborate on it...

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Although this would give a problem with fan modulation.

If the fan is linked to the bed cooler, it will go off for 1st layer and when the print finishes. I like

to keep the printhead cooler on for at least 10mins after the machine finishes to cure heatsoak.

Forgot about that....

Hmm.

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Okay, so super exotic solution: a variable geometry shroud to direct airflow to the printhead right away, and to the bed after the first layer coupled with a Daid Cura fix to add a heatsoak run-time option in the slicer.... Readily achievable solution, ignore cooling the printhead until after the first layer, then utilize the dual outlets coupled with said Daid Cura option for heatsoak.

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