Need some input on 3D Printing a light cover for a “Typical 40W Bulb”. Material choices in particular. Do we think PETG would have enough heat resistance to not deform? Also I have been told that a bulb puts out UV and that the plastic yellowing would be a concern.
All thoughts appreciated.
Thanks.
Incandescent Bulb ?
Very much most likely incandescent, yes.
Good idea, I can suggest that.
I’d suggest getting a laser heat reader (~$15 on Amazon) for the light source and leave the light source on a few hours before reading. Then you have a more accurate idea of heat requirements (was uncertain if light source is prefab or if you’re creating your own). Agree that LED will significantly reduce heat. Also will need to take into consideration the translucency of your material and if it supports your heat level.
With about 2 inches of space and airflow you can run 20-40w using PETG lampshade for the 8 hours I tested, but the cost of incandescent in energy use and in greater failure rate is not worth it LED is way better.
How close to the bulb are you going to be? Bulbs get very hot, but you can touch them without burning your hand so that puts it in the 150C range on the glass.
PETg has a Tg of ~60-80C and so if it’s not in direct contact with the bulb should be able to handle ambient temperatures from a 40W bulb (depending on ambient temperatures and airflow)
ABS or ABS/PC is the safest bet for something like this. With a Tg of ~105-120 you’d be hard pressed to melt this on a lightbulb below 100W in direct contact.
The temperature that the lampshade reaches will depend on several factors, some of which others have already mentioned. They include: the type of bulb (incandescent, fluorescent, LED - as in: is the 40W the actual power or is it the equivalent light emitted compared to an incandescent); spacing between the shade and the bulb; whether the bulb is fully enclosed by the shade or open to natural convection (and how open); the thickness of the shade; the opacity and light transmission characteristics of the plastic used; and the ambient conditions.
Quite a while ago, I offered to do a heat transfer analysis of a printer component that looked like it was going to happen, but the maker was never able to provide CAD drawings, so it didn’t. I might be persuaded to do a simple CFD analysis of a lampshade. Try me. 
Polycarbonate will do the job. And yes it is hard to print but it is trasperent also as PETG.