Just found this great resource for just about everything you ever wanted to know about working with polycarbonate, AKA Lexan.
Here it is: Polycarbonate Fundamentals: Machining & Forming Tips, via PlasticsMachining.com.
Specifically: “Heating cycle: Heating polycarbonate sheet for vacuum forming requires a heat penetration range of 360F to 410F. The ideal forming temperature is 375F.
When polycarbonate sheet reaches forming temperature, uniform “sag” occurs. The amount of sag depends on the size and thickness of the sheet. Once the uniform temperature has been achieved, timers can accurately reproduce the condition, with part-to-part consistency maintained. Polycarbonate sheet “sets up” quickly compared to other thermoplastics, and can be removed from the mold in a short period of time.
Cold bending: Polycarbonate sheet can be cold formed into circular shapes for walkways, etc. The rule states that the radius of the curvature must be at least 100 times the material thickness.
Strip heating: Strip heating or line bending is commonly used for producing localized angular bends in polycarbonate. Generally, pre-drying is not required for a material thickness of 0.118 inch or less. On thicker gauges, pre-drying can be avoided by back-routing or V-grooving the sheet to 1Ú8 inch or less thickness.”
So, now, let me introduce the latest caper… … … the Battery Module Project!