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Comment by unwind | Hacker News Reader

Very cool, nice effort and a good write-up!

If my math is right it seems the cost in material for the printed part is around $5 which seems ridiculously cheap for a custom-designed and adapted solution like this. Nice!

I wish the author had spent a few words extra to motivate why it needs to be in PETG filament for "heat resistance", is the regular PLA limit of ~55 degrees Celsius not okay for a desktop accessory? I guess if it's in direct sunlight that might be exceeded, or perhaps if the laptop runs very hot?

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To be fair, that's something you learn as soon as you start 3d printing. Anything that experiences repeated stress and have any chance of getting over room temperature during summer should not be printed in PLA. And near a computer heating up, it sure looks like it's going to be higher than room temperature. Also pictures in a train exposed to sunlight via glasses are another reason for concern.

Compared to PLA, PETG has higher temperature resistance (by about 20°C), isn't quite as susceptible to stress, doesn't cost more and isn't any harder to print on modern printers.

Some people in the 3d printing community have totally ditched PLA and use PETG as a baseline because of that.

I use ABS as a baseline, it holds up well, is easier to sand than most other materials, and is soluble in acetone which gives you some nice methods for smoothing layer lines as well as adhering parts together. It requires a heated chamber though.

ABS also emits potentially toxic, and certainly unpleasant, fumes, so you need a good carbon filter and ventilation system!

> is the regular PLA limit of ~55 degrees Celsius not okay for a desktop accessory?

Not the author, but PLA has a glass transition temperature of around 60 degrees, which in layman's terms is when it starts to melt. However, depending on the quality of the printing process, layers start separating/the print is pliable significantly lower, at around 35-40 degrees. This means that in countries where you get 30+ degree summers, PLA is not really suitable for anything which experiences any kind of stress. I would hazard a guess that the standing laptop can cause quite a bit of stress when the train starts/stops.

It should be mentioned that as far as I can tell pretty much no one is selling pure PLA filament. They all have additives, so who knows what the actual glass transition temperature is for any random given filament. This has been true for a while too. Pure PLA has some properly awful properties, among which is it having pretty much no elastic deformation. Any amount of force will introduce microscopic cracks. The various additives reduce these kinds of issues and are therefore not really optional.

I used ASA for something I intended to keep in my garage, I live in Florida so summer gets hot. ASA is way more heat resistant than both. My water boiler uses the heat within the garage as part of how it warms water so my garage doesnt get too hot but it can still feel pretty bad in there.

Glass transition temperatures are a little bit misleading, but from personal experience even leaving a PLA print in direct sunlight under even a little tension will cause it to warp in as little as 30 minutes if you aren't careful.

It becomes pretty weak even on a hot day in the sun and in a hot car can melt (not into a puddle but into al dente pasta).

In addition to heat resistance, I find that PETG handles stress and resists stretching out way more than PLA

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