Much of SIGMADESIGN’s test lab work involves ensuring products pass a specific standard. Does it pass the appropriate parts of IEC 60068? One of the many MIL standard methods? FCC Part 15? This type of routine testing is interesting to do, but it is completed according to strict processes and the answer is typically “yes” or “no.” My favorite question to answer is “The unit passed (or failed), but by how much?” Or: “We need it to be this strong or this durable. Is it?”
It’s at this intersection of design/engineering and testing that the real fun begins, and I get to feel like I’m on an episode of Mythbusters. By customizing tests and executing quickly, we use testing as an integral part of the design process.
A few examples:
Sometimes, it’s as simple as testing a plastic detent. We recently designed an enclosure eventually destined for injection-molded mass production. The door swings open and stays open because of the detent. Our FEA says the detent is plenty strong. When we created the 3D printed enclosure and verified the FEA, it worked as expected, but would it last? We needed to simulate the opening of the enclosure once or twice a day for a maximum of ten years.
We attached our prototype 3D printed door to a custom jig with a pneumatic logic and cylinder to open and close it. About 10,000 cycles later with no noticeable wear, we deemed it passing with adequate design margin. Given that 3D printed ABS typically only has 80% the strength of a molded parts and a less controlled surface finish, we were able to deliver our design with confidence.
Another exciting test involved quickly helping a customer through some manufacturing process decisions. They had a few different designs prototyped. Our job was quite simply to pull a large sample of the units apart until they broke, helping them figure out which design was the strongest. We began by aging the items in our environmental chamber, cycling temperature and humidity to weaken the units as though they had been in use for years. Then we rigged them up on our motorized force stand, and proceeded to pull each one apart. We ended up with hundreds of data points. Through this custom test process, we were able help ensure the best product was brought to market.
Yet another test involved human factors engineering. We evaluated several button designs for a customer, measuring the press force, calculating tactile ratios and analyzing several other factors. We then proceeded to test a large number of prototype units to ensure manufacturing consistency and adherence to design specifications.
Testing to support engineering and manufacturing efforts is always interesting. The challenge comes in making sure we are fast and efficient enough to let the engineering effort continue at full steam while we complete our test work. This is why we have set up and expanded our in-house testing capability to complete customized work quickly.
by Douglas Burnette |Lead Test Technician