Editor’s Note: The Engineerist is a three-part blog series written by Michael Corr, founder of Los Angeles-based manufacturing consulting firm, DuroLabs. This is part two.
Certification testing is expensive, especially when your product fails.
I was managing an engineering team several years ago when we submitted a new product with an injection-molded enclosure to UL for certification testing. The tests included a mechanical stress test with some rather extreme impact forces. This product was a deviation to a predecessor and therefore had legacy requirements which constrained our design options. With the time pressure we had to get the product to market, the mechanical engineering team and I were hoping a few modest changes to the existing legacy injection mold would be sufficient to pass the new certification testing and go into production. They weren’t.
Prototype Prep Before UL Testing
After a humbling blow to our egos and sizeable invoices from both the molder and UL, we took another approach. The ME team reviewed the points of failure of the plastic enclosure and came up with a few design improvements. But we didn’t want to risk failure again, and UL required testing parts fabricated from the actual production mold. It would be too expensive and risky if we were to modify the tool and fail again.
The solution was to leverage Proto Labs’ quick turn on CNC-milled parts and expansive plastic material options. Conveniently, Proto Labs’ library of materials included the same plastic used in our injection-molded production part—a PET thermoplastic we chose because of its recyclability. In just a few days and only a few hundred dollars, we had milled versions of all three different design options, in hand. While we recognized the differences in material properties of a milled part versus an injected part, there was minimal impact with our design, so our in-house test results would be valid.
Rapid Iteration Yields Validation
In our own lab, we recreated the same tests performed at UL and in a few hours had credible results. We replicated the test results on the original part to confirm our test procedures matched UL’s, allowing us to fairly compare the results for the new part designs. Each of the new designs showed improved performance, but they were still not passing the force impact tests. Using these latest failure results and additional FEA reports, we came up with two more design options. Again, after only a few days and minimal investment, we had a new batch of parts in hand from Proto Labs and continued our testing.
These final prototypes passed our internal tests and gave us the confidence to send the design updates to our mold supplier. A few weeks later, we had a batch of first articles from the tool back and ready for certification testing at UL. This time it was a success.
After this humbling episode, using Proto Labs to prototype parts before cutting steel became a requirement in our part design process. Regardless of how small the change or simple the part was, using Proto Labs was essential. Cutting a steel mold is an expensive and lengthy process. Most startup companies don’t have the capital or time to not have the greatest chance of success when parts come off the mold. Everything at a startup is very hand-to-mouth, with little leniency for failure. For that reason, it has become imperative to use quick and inexpensive prototyping processes. Proto Labs’ CNC milling is both, and the quality is so high that the parts are often indistinguishable from production parts.
Michael Corr is an engineering manager with more than 15 years of experience building and manufacturing various hardware products. Over the span of his career, he has developed telecom equipment, clean tech products, wearables, and most recently commercial grade UAVs.
With a focus in manufacturing, Corr has spent a significant amount of time managing production both in the U.S. and overseas and has incorporated a lot of his experience into design for manufacturability best practices. Corr currently manages his own manufacturing consulting firm, DuroLabs, based in Los Angeles.