The parts required tight angle tolerances, and this was further complicated by lack of structure on the part to lock the angle dimension in place, particularly after the parts were machined on Gemstar’s 5 axis router. Thermoformed parts carry inherent stress, since they are heat formed from an extruded flat piece of plastic. After forming, the material can still have a tendency to flex back towards that original flat sheet, especially when machining removes some of the originally formed material.
A standard thermoformed tool design didn’t do the job. The parts off of standard male and female tools varied beyond what was acceptable.