CAD is Perfect… but it’s not Engineering!


Have you ever had a mechanical designer say to you “I don’t understand why it doesn’t work… the CAD looks right!?” I have! And it raises an interesting point that is repeatedly ignored. CAD is an amazing tool that can help you predict how a product will turn out… but it doesn’t replace REAL ENGINEERING!

Just to put it into perspective, a coworker of mine came up to me and asked me who ‘The Engineer’ was on a particular project we both were working on… I said, “I am”. Then she said, “No no – The Engineer… The ElectricalEngineer” as if it were a higher calling! Let me think… I designed the hardware, circuit, and wrote the program… but because I’m a ‘mechanical ‘guy’ I wasn’t considered the engineer. Needless to say, that really stuck with me. It brought back all of those late nights of studying and working my way through my degree only to get disregarded by a high school drop out. We design real things… and this has two drawbacks.

  1. What we do is easy.
  2. CAD takes the place of a mechanical engineering education.

The truth is that the pretty picture on the screen has very little to do with engineering. All the engineering needs to be done before/while the CAD is being created. We work closely with industrial designers to design a shape, feel, weight, and overall experience for the customer. Then we define every aspect of a part to ensure that an imperfect chain of manufacturing processes can work flawlessly in production… (well, at least as close as we can get).

Okay, so back to our mechanical designer… “I don’t understand why it doesn’t work… the CAD looks right!?” Fortunately, this designer happens to also be a mechanical engineer. She was very discouraged that her CAD model wasn’t lining up with the parts we were getting in. And to make matters worse, this problem was holding up a product launch! She knew the trouble spots to look out for, but the problems she saw didn’t make sense.

The investigation began! It wasn’t too long before she found the problems… and yes, there were many! The drawings called out 0.080″ thick sheet metal when the CAD model was designed with 0.060″. Then she discovered that the projected views were reversed! The added thickness caused the screw holes to be misaligned by ~1mm and the reversed views caused the parts to come in mirrored. There were some other minor errors, but nothing worth mentioning. She traced them back to the drawing created by an outside “CAD jockey” house.


Unfortunately, the details engineers work out are often hidden from sight. Frequently a manager or coworker will see a pretty picture and say, “Now, I’m not a mechanical guy, but I don’t understand what’s so difficult?” or in other words… “I could do that, so why are you so slow?”

I don’t think there’s any way around this, but I do know that it’s very attractive to release a design before all the due diligence is done and meet the deadline… but I plead with you to hold your ground! If we give in and work fast and sloppy, it will give you and mechanical engineering a bad name. In a time of ‘scrum sprints’ and ‘fast iteration loops’ it is ever more important that we stick together and make sure things are done right. After all, if a program has a problem, you change some things, hit the ‘compile’ button, and you’re done in 3 minutes. Our ‘compile’ button takes 3 weeks.

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