That is a pretty funny saying but it is true to some extent. Being an engineer who has designed a few products I understand that it is easy to get wrapped up in your design and overlook some basic problem. Recently I came across a problem with a coffee machine. The machine is a newer commercial design that brews from pods not those plastic cups. This is a nice feature because the pods are similar to a tea bag in that it is compostable and you are not passing boiling through a little plastic cup before you drink the coffee. These machines are common in offices or car dealerships for the customers to use.

The problem was that some people were changing the settings on the machine to brew a larger cup, say a travel mug and calls started coming in that the machines were overflowing. The compartment where the coffee pod fits into the machine can only hold so much water so there is a balance of how much water and how long it brews. By changing the “how much” water and not the brewing time, the machine would overflow.  

The catch was that it didn’t do it all the time. It turns out that some technicians would change the settings before the machine got installed, so those machines never had a problem. The design engineers didn’t know if the problem because as far as they were concerned the machine brewed a perfect 8oz cup, and it did. Just no one was using 8oz cups anymore…