I'm planning to print up a bunch of brackets to mount LED shop lights (very similar to these) to the ceiling in my garage. My plan is to use an upside-down "U" shape bracket that screws into a joist/drywall anchor in the middle and then sort of clips around the sides of the metal frame.
Maybe filament type doesn't matter much here, but I'd rather not come out to one of the lights having fallen on my car if I can help it 😅
I think the main considerations are just temperature and stiffness. It can get up to about 85F in the garage on the hottest summer days, and probably a few degrees warmer by the ceiling. The lamps are cheap LED tubes, so the metal housing only gets slightly warm to the touch (say 90-100F or so). I know PLA is a bit stiffer at room temp, but I'm worried it might soften too much at the worst case of warm temperatures.
Any thoughts on PLA vs PETG for this situation?
That link doesn’t work for me. But basically use PETG for strength and heat resistance, PLA is better for rigidity or dimensional accuracy, but it’ll soften super easily. ASA/ABS would be better but is trickier to print and needs an enclosure.
PETG is weaker than PLA. Actually PLA is the strongest filament.
It’s not quite that clear cut I’m afraid. PLA is stiffer which can be desirable but also makes it quite brittle. That means while it has a higher tensile strength, it has a lower impact strength - and it fails more unexpectedly and catastrophically than PETG, which is much more likely to deflect and bend rather than snap. That plus PLA’s susceptibility to warping or bending in even fairly moderate heat generally makes it less practical for real-world practical things that are going to deal with a bit of abuse.
PLA is much better than PETG for models or anything requiring dimensional accuracy over strength, though.
First of all, PLA is not brittle at all. I don't understand why people use this word. Glass is brittle, PLA is not. It does have lower impact resistance than PETG, but the difference is not that big. Also, bendy part is as useful as a snapped part in every application that requires strength. Tensile strength and flexural strength is usually more important in most applications and PLA excels in those.
If impact resistance is important to you, you can try BASF PRO1 PLA, which absorbs much higher impact forces than any regular PETG.
Glass transition temperature for PLA is 60C. It does NOT warp or bend at temperatures below 60C. It's just physically impossible. But yeah, 60C is quite a low temperature for many applications. Glass transition temperature of PETG is just 81C. While it's higher than PLA it is still not suitable for anything which can reach boiling water temps.
If both strength and temperature resistance are important, then the obvious choice is ASA. PETG's only benefit is that you can buy certified food safe PETG filament easily and cheaply. Otherwise PETG is pretty much useless for all intents and purposes.
In the interests of avoiding pointless semantic arguments, you can probably safely assume that in any discussion of the relative merits of materials, the word “more” precedes any adjective describing said material’s properties. For example: PLA is more brittle than PETG.
I don’t agree. There are many application where a bending failure mode is much more desirable than snapping. OP’s situation, for example. Pretty sure they’d much rather they were alerted to a problem because their lights were pointing in the wrong direction than smashed on the floor.
The extra temperature resistance of PETG compared to PLA might not be a big number on paper, but it makes it suitable for many things PLA isn’t. Things for use in a car, for example, are common to see problems when printed in PLA (you can find tons of pictures of PLA phone holders melted in the sun). PETG isn’t immune but will almost always fare better in any situation where there might be heat. For example, an LED light fitting, like OP's situation.
Anyway. Do we really have to fanboy materials?