Answered: hardening lexan sheets

f. Non shattering plastic from the following list;polycarbonate, acetel monopolymer (Delrin), acetal copolymer (Acetron GP), POM (acetal), ABS, PEEK, PET, HDPE, LDPE, Nylon (all grades), Polypropylene, FEP;as cut from a single 12" x 24" sheet up to 0.070" thick.

Plastic can be mechanically altered by cutting, drilling or bending etc., but it cannot be chemically treated, melted or cast. Teams may heat the polycarbonate to aid in bending.

so here’s my question.

Can we put a legal sheet of lexan (12 x 24) in an oven which would make it smaller and thicker? it would be kind of like a shrinkydink. i dont know if that would be considered mechanically altered, but it is not “chemically treated, melted or cast” which would be illegal.


No, this is not legal. The intent is to allow heat to aid bending, not use heat to custom form. What you’ve described is much closer to custom forming or casting, than it is to bending.

ok thanks, i’ll just double it up.

You’re welcome!

I dont know if you want me to make a sepperate thread about this, but would
this polycarbonate Fresnel lens be legal if it is thinner than .070?

i have no idea if it had been “chemically treated, melted or cast.”

To take it further, is it legal to buy a professionally “mechanically altered” legal piece of polycarbonate?

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No, this would not be legal. The rule makes allowances for raw materials that can then be modified, within the specified rules. Pre-manufactured material are not allowed.