I’ve been reading that some plastic is dangerous to engrave on and wondered how to tell what to stay away from. I had wanted to engrave on cell phone cases, but wasn’t sure what to look for
It is primarily PVC you have to stay away from, it “eats everything” when it gets burned. Also PLA and PUR are not something to play with. In general, it is difficult for non-professionals to decide which plastic you are working with. If you are lucky, it is marked with a triangle and some letters which indicate the abbreviation for the plastic types. With this information you can find processing instructions online, typically at the plastics industry association which has an extensive library.
That said, I do not think that mobile phones are made of PVC and a single cover or two, with a well-functioning extraction on your laser machine, should not be a life-threatening action.