@Rob: It sounds like the problem isn't expansion of the plastic but, as Brooks says in the article, the change in stiffness with temperature.
I'm not sure what material this door latch is made from, but often plastic parts that are designed to flex in operation are made from polypropylene. The elastic modulus of polypropylene changes by a factor of five between room temperature and 100°C, i.e. it is five times less stiff at 100°C than at room temperature. I'd guess that, even from room temperature to 90°F, it might change by as much as 50%.
The mechanical properties of plastics are highly dependent on temperature and strain rate. Design engineers need to keep these effects in mind. When designing a steel part, it's usually safe to assume that the elastic modulus, yield strength, tensile strength, and ductility are the same from room temperature to at least 300°F. With plastics, you can't assume that the properties listed on the datasheet are the same properties the material will have in your application.
Several years ago, Joseph Ogando wrote a great article for Design News regarding the use and abuse of plastics datasheets. It points out many of the parameters that affect the properties of plastics. I've sent it to a lot of people over the years as a reference.
Sounds like the hook should have been designed to be free of the plastic even as the plastic expanded. Even so, should the plastic on this microwave -- which is expected to get hot -- expand so easily? At merely 80 degrees? Seems the plastic may be part of the culprit.
Truchard will be presented the award at the 2014 Golden Mousetrap Awards ceremony during the co-located events Pacific Design & Manufacturing, MD&M West, WestPack, PLASTEC West, Electronics West, ATX West, and AeroCon.
In a bid to boost the viability of lithium-based electric car batteries, a team at Lawrence Berkeley National Laboratory has developed a chemistry that could possibly double an EV’s driving range while cutting its battery cost in half.
For industrial control applications, or even a simple assembly line, that machine can go almost 24/7 without a break. But what happens when the task is a little more complex? That’s where the “smart” machine would come in. The smart machine is one that has some simple (or complex in some cases) processing capability to be able to adapt to changing conditions. Such machines are suited for a host of applications, including automotive, aerospace, defense, medical, computers and electronics, telecommunications, consumer goods, and so on. This discussion will examine what’s possible with smart machines, and what tradeoffs need to be made to implement such a solution.