Cold Forming polycarbonate sheet is any forming formed below 300 F (149 C). Barrel vault skylights and some face shields are cold formed.
In order for the part to maintain its shape a permanent frame must be used to hold the edges in place. As in all forming of plastics, inducing stress often leads to part failure. In barrel vaults the stress normally develops as spider cracking along the tightest radius. The spider cracking is often referred to a “crazing”. In order to avoid crazing, the minimum radius of curvature for polycarbonate is 100t, where t is the sheet thickness. For example: a sheet of 0.1 inches (2.54mm) cannot have a radius tighter than 10 inches (254mm). However, if you need a tighter radius, you can achieve that by heating the material to 300 F and then reforming. Be careful to check the stress on your part. That can be done by using polarizing film but that is a blog for another day.
Next time we will discuss Brake Forming and Strip Heating.
For additional information on cold forming of Polycarbonate sheet, contact Liz Grimes – Technical Director. Tel: 215-872-3532 Email: LGrimes@HighLinePC.com