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I'm working on a (currently only conceptual) design for a Peltier-cooled sample holder, and the cold side will need some insulation. It's likely to be a rather complex shape, so 3D printing it looks like a good plan. I can get parts made on a Ultimaker (not sure which model at the moment), normally in PLA.

I can look up the bulk thermal conductivity of PLA (it seems to be the best of the typical filaments already. I can find high-TC filaments. What I can't find is how to design an insulating part. In particular, while a reduced fill will reduce the TC, and the actual percentage might allow a decent approximation to the thermal conductivity in an isotropic structure, it's highly unlikely I'll have an isotropic structure. This means I don't know how well I can approximate the final TC as a percentage of the bulk The fill patterns I've seen (as a part designer, not a printer operator) would likely end up like cells running in the direction I want to avoid heat flow (perpendicular to the Peltier's heat-spreader plates). Knowing the TC, I could calculate the heat flow - I have some background in thermal physics.

Is there any kind of established best practice for designing thermally insulating parts? Any way to approximate the thermal conductivity?

Chris H
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  • Be sure to include in your research the foamy PLA that one can use for models. The increase in volume is determined by the nozzle temperature and results in varying densities of extruded plastic. If you don't require extreme mechanical strength, it may provide the best insulation. https://www.matterhackers.com/store/l/colorfabb-lw-pla-filament-075kg/sk/MSC8ZXG5 – fred_dot_u Jan 20 '23 at 20:36
  • @fred_dot_u that's certainly interesting, though I'd have to consider whether we can get sufficient attachment points with it. The main mechanical mounting would probably have to come from the copper sample mount anyway, for reasons of temperature stability, so this part wouldn't have to be very strong. – Chris H Jan 20 '23 at 20:42
  • If you have a dual extruder printer add heatsink fins out of TPU. Just an idea. – AzulShiva Jan 30 '23 at 21:55
  • @AzulShiva I'm trying to block heat (and hot air) flow from the hot side of the peltier stack to the cold side. The cold side has to be on top. Under the hot side the plan is to have a large metal heatsink, or maybe water cooling – Chris H Jan 31 '23 at 07:02

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Coincidently, I am considering the same issue; I'm trying to design a 3D-printed Peltier refrigerator to maintain the "cold-chain" for drug distribution in low-resource settings.

I don't have the answers, but I did just come across this useful poster presentation on the same topic: Influence of 3D infill pattern on thermal transport, by Yu Han

Influence of 3D infill pattern on thermal transport

It may provide some help.

Greenonline
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David Holdsworth
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  • Hi and welcome to SE.3DP. I have added a reduced quality (but still readable) JPEG of the useful PDF to your answer, as otherwise your answer would have been just a *link-only answer*, which fall foul of SE rules, and so it would have been deleted. This is because of [link rot](https://en.wikipedia.org/wiki/Link_rot). Please take note of that fact in future answers. Also, please don't forget to take the [tour]. If you can update your answer with some concrete solution(s) to the OP's issue at a later time, please [edit] and do so. Thanks. – Greenonline Jan 20 '23 at 20:54