Just to follow up on this. Our temps here the past week have been hitting 115f. The other day I got in my car and it was reading 119f outside. So I’ve been torture testing a few extra/misprint parts from my MPCNC build. I have both PETG and PLA sitting outside in full sun. Around 3PM at full heat the PLA is soft and I can dent/deform it. Full (or nearly full) parts I can’t really reshape but I could slightly deform. Partial prints that aren’t as substantial (or something less 3D like the motor mounts) can easily be bent/reformed.
It seems that the extra perimeters and high infill give the parts plenty of strength even in temperatures high enough to soften the PLA. I wouldn’t actually run a machine in those conditions…and I’ve been keeping the AC in my shop on at 86 (the warmest it will go) when I’m not out there just in case. But I think when I start printing the new parts I’ll do so in PLA instead of PETG this time. Unless my next electric bill convinces me that even cooling the shop to 86 is too expensive as the temp in the shop gets higher than the outside temp when I don’t run the AC out there.
Oh – the PETG parts out in the sun…rock solid still. So they are far better suited for heat. But I’m not sure the slower printing and hassles of getting PETG dialed in are really worth it on this.