Takes one look at the fracture patterns in the transparent plastic and the reported spontaneous breakage by Roboto owners and concludes I’ve seen this before, its residual stress/strain cracking.
See http://en.wikipedia.org/wiki/Environ...tress_cracking and section on “Predicting ESC”, which states:
“Residual stress and residual strain are especially important because they can drive crack growth. They frequently arise from poor injection moulding, especially where cold tools are used in the process. Polycarbonate is a particular problem, and tool temperatures in excess of 80 C must be used to lower residual stresses and strains.”
Polycarbonate being one of the few commercially produced transparent plastics.
Now for the next step. IMO, Mattel or whoever is in charge should ask the manufacturer for comment and have their factory production control manual and records independently review, as it would appear they are providing some defective goods. They could also confirm the cause of cracking by employing someone skilled in residual strain measurement and in the fracture analysis of brittle materials (e.g. glass, transparent plastics) by allowing them to examine and test the cracked Roboto's.