Building Smarter Crash-Test Dummies

Jon Lawson

Erica Mutch reveals how a redesigned component helps build smarter crash-test dummies

If it’s not broken, don’t fix it, right? But when there’s a way to make it better, engineers can get it done. In a complex system, the tiniest components play critical roles, so refining a product can start with its smallest elements.

Slice6, a miniature data acquisition system manufactured by Diversified Technical Systems (DTS), depends on a small connector unit to collect, store and transmit data from sensor arrays in military and automotive crash-test dummies. This connector unit needs to be both rugged and reliable to perform in extreme shock, vibration, and blast environments – it’s all in a day’s work for test dummies used in injury biomechanics testing. Reliable connector performance, however, didn’t satisfy the company that supplied the unit when its engineers realised the custom unit could be made even better.

Connector Units In Crash-Test Dummies

The custom connector unit, made by Omnetics Connector Corporation, consists of a U-shaped metal shell with two integrated connectors: one Micro connector with 36 pins positioned inside the shell, and one Nano connector with 36 pins positioned on the shell’s exterior. The width of the shell measures just 13mm.

The unit fits inside the Slice6 DAQ module, which measures 24 x 30 x 10mm and weighs in at 28g. Size, weight and product availability are key considerations when designing the connector unit. Military orders can be time-critical and the connector unit, made exclusively for DTS, took 10 days to manufacture in small batches of 100 or 120 pieces – not an unusual task for the connector supplier, which specialises in MIL-spec, medical and precision miniature interconnects. Even so, this was a longer lead time than the company liked to quote.

“To manufacture the old version of the unit, we were cutting wires to about 25mm, stripping them on both ends and then crimping a Nano contact on one end and a Micro contact on the other. Each unit contained 36 wires,” says Travis Neumann, special projects manager at Omnetics. “Prepping the wire took about three days. Then we loaded the wires into the connector housing. It took another three days to get all the wires loaded into the two connector pieces that go into the metal shell. After that, we epoxied the connectors to the shell and tested the unit. Overall, it was a time consuming and inefficient manufacturing process.”

Ensuring Quality Control In Crash-Test Dummies

Quality control is critical. Slice6 supports NHTSA and EURO NCAP testing, and meets SAE J211, ISO 6487and FAA data acquisition requirements. There is no margin for error. Yet, inside that tiny housing there was a cumulative .91m of wire handled by at least six people.

“When a part has a more complicated pin-out, there is a greater risk of getting things crossed. So we always test each piece,” says Neumann.

The engineering team wanted to trim that lead time, plus eliminate the potential for pin-loading error. The solution came in one easy piece: a tiny flex circuit. “Now we make a surface-mount style Micro connector, load the contacts into the plastic pin housing and fill it with epoxy. On the Nano side, we do the same thing,” says Neumann, whose background in hybrid microelectronics exposed him to flex circuitry’s potential uses in connector design. “The flex board arrives 100% tested. When we solder the contacts onto the flex board, our fixtures don’t allow us to put the parts on incorrectly. Finally, we do an IPC visual inspection after they are soldered and then test the parts.”

Considerable Time Savings

The time savings are significant: a 120-piece order can be made in about four hours. “This allows us to meet our just-in-time (JIT) supplier goals to reduce inventory and shorten our lead times,” says Grant Newton, Mechanical Engineering department manager at DTS.

The flex board is more costly, but the labour savings are considerable. Plus, replacing that expanse of wire with the tiny flex board enabled Omnetics to reduce the size of the unit by 3.17mm, which in turn allowed DTS to fit the Slice6 into tighter spaces.

“We were surprised that Omnetics was able to fit our requirements into an even smaller space. This allowed our customers to fit our products into even tighter locations, so it was a big win for everyone,” says Newton. “Omnetics provided us with details about how the product was being manufactured, which allowed us to discuss the changes from a more informed viewpoint. The engineering team is always open to discuss new designs with us. We consider them an extension of our design team.”

One more advantage of redesigning with flex is, naturally, flexibility. Although DTS originally designed its product for crash dummies, it is now being embedded on helicopter rotors and other devices that gather data that allows manufacturers to make cars, planes, child seats and other vehicles safe. Pretty smart, for a bunch of dummies.

Erica Mutch is with Omnetics

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