Refrigerator plastic shelf failure / KitchenAid redesign

Tom's personal refrigerator history. Used as the canonical teaching parable for "you can't substitute one material for another without redesigning the joints." Mid-1980s threaded-joint plastic failure → 1990 KitchenAid slot-and-drawer design.

Then in the mid-eighties I bought a new refrigerator. The outside was steel and the inside was a panel of plastic. Plastic is a much better material for the inside of a refrigerator because you're going to spill foods on it — it has a low internal surface energy, much lower than metals, and things don't stick to it as easily. But within five years I had to replace the refrigerator, because they used screws to attach the shelves to the plastic, and plastic is a lousy material for threaded joints. You just shouldn't use threaded joints in plastics — maybe in a Hasbro or Fisher-Price toy. And your child is going to come to you and say, daddy, my toy broke, can you glue it together. And you say, of course not, I took Professor Eagar's course on adhesives and we know that plastics have low surface energy and there's no good glue to fix your cheap little toy, child. Well, maybe you won't say it exactly that way to them, but that's in fact the case. Most of these things you just throw away. I had to throw away the refrigerator because the shelves were broken.