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Determining heat dissipation of 3D printed box - final results!

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HendriXML:
Thanks for your response, the idea of using a different material like PETG sounds good.

88 deg of glass transition temp vs 60 is a lot.

The box used for this experiment is a throwaway one, has already a big hole in it for the wires.  :-+

Like you said getting some airflow is what is under investigation. I hope the heatsink will create enough rising air / create enough pressure difference. I would be happy with 10 watts.

Conrad Hoffman:
If it has airflow, it becomes more difficult, but IMO your chances of success are way better in terms of not getting too hot.

DaJMasta:
I would consider the glass transition temperature as a guideline than a hard rule, though, and different blends from different manufacturers will behave somewhat differently.  My experience is that with moderate pressure at about 60-65C sustained, PETG will bend permanently given a while whereas if there isn't any load on it, I haven't yet seen it flex permanently.

I just had a PLA print start to warp and peel off the bed set to 65C while other PLAs (even from the same manufacturer, though in a different color) were fine with a 65C bed temp.  Lowering to 60C got me the adhesion I wanted, but it makes me think that the equivalent temperature for PLA to warp in a loaded situation is probably in the 45C ballpark, maybe even lower.

The plastic doesn't need to fully transition to be able to flow somewhat, and if you're looking for longevity, that's probably the temperature you want to design around.

CatalinaWOW:
One of the beauties of 3D printing is the ease of prototyping.  It is far easier to measure the results than to predict them with any accuracy.  All that said I would not expect much dissipation capability from this configuration.  Have you considered making the heat sink one of the walls of the box.  Lets the heat get to outside world the easiest way possible and saves the printing time of that box side.  The big downside is that it isn't electrically insulated from the world which may be important to your application.

HendriXML:
The reason for this little experiment is mostly to see what the maximal dissipation can be for this kind of box. It isn't optimized for airflow, it is also not fully closed. It is a box that can be used at the bench without any worries that a flying piece of clipped wire could short things out.

The question for me is, to what level of dissipation it still can be used. At this moment this is done in the name of science only. To answer the question how much difference the air slots make.

Maybe the pressure of the heated air is not good enough to push air through the top slots at a decent rate. In that case the temperatures in the box might become static and evenly spread, so even lesser amount of temp/weight difference of air can be created around the heatsink. In that scenario the vertical slots will be of not much use either, so it will be close to the performance of a completely closed box.

If it performs well then I'll have to find out what kind of effect covering top slots - a few at a time - have on the performance. Will is gradually perform less or will it collapse?

These thing might sharpen my intuition when designing other enclosures. However this kind of design will not be the best for high power stuff.

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