Tooling around

Detroit, MI-For nearly 70 years, Detroit Diesel Corp has supplied powertrain components to premier commercial truck, motorcoach, and rv motorhomes, bus, and emergency vehicle builders around the globe. The company has maintained its leadership role by continuously developing cutting-edge technologies for its product lines of diesel and alternative fuel engines, transmissions, and axles.

Keeping up with these wide-ranging specifications and performance standards may not require a whole new engine concept, but may take numerous enhancements of engines, incorporating design modifications and the latest component innovations. The process frequently requires prototype parts and comprehensive testing.

Occasionally, assistance is required to complete the assembly procedures of modified engines. “Detroit Diesel had developed the sixth generation of its electronic engine control system, called the DDEC VI,” says Ken Zalucki, sales engineer for the rapid prototyping firm 3-Dimensional Services (Rochester Hills, MI; www.3dimensional.com). “Major components of the DDEC VI are a series of sensors installed at each of the six fuel injectors on the top of the engine head and under the valve cover that provide operational monitoring and control. Placing the new sensor terminals into the engine during the pre-production build stages, that is, completing engines for various testing and trials while also coordinating the necessary assembly procedures, turned out to be somewhat of a challenge.”

The terminal, Zalucki explains, required a male wiring plug be inserted into its female counterpart at the injector location, a position too close to the engine wall and between two valve springs that limited access for assembly by hand.

“The process proved very difficult if not impossible to put enough pressure on the plug while securing the retaining clips to successfully engage the parts,” explains Zalucki. “For those few times when the plug was forced in, connector blades were frequently bent or misaligned, requiring repair or replacement. Because this was only the pre-production builds, completion of most tools and assists planned for production schedules were still up to 12 weeks down the road.”

The first tool attempt by 3-Dimensional consisted of a pliers-like design with thin jaws similar to needle nose pliers. Each side had multiple step surfaces to properly locate and grasp the plug and to depress the locking flanges. A stop pin was incorporated into the design that prevented the tool from being pressed too hard and exerting excessive pressure on the parts that could crush the terminal, plug, or contact blades.

“Once Detroit Diesel verified the operation of this initial tool and provided feedback,” notes Zalucki, “we began the process of fine tuning and finalizing the design. Some of the modifications included making sure the tool met all of their ergonomic criteria. The first finished tool, now measuring nearly 10 inches long and meeting all specifications, plus with a cushioning rubber coating on the handles to improve comfort, was delivered approximately seven days after the original prototype tool. Three additional tools were completed within another week. And more may be ordered for service centers to complete warranty work in the future.”

To complete the tools, 3-Dimensional Services relied upon a sampling of its production process resources, including its laser cutting capabilities, to cut and trim the handles from 3/8-in thick durable steel, and to cut and shape the work-holding jaws. The jaws were also machined to final size and form utilizing cnc machining centers, and then each jaw tip was welded to the handles. To assemble with the included spring action, the handles were drilled, tapped, and fastened. Where necessary, surfaces were hardened, ground, and polished to provide a finished appearance, and the tools were given an acid bath resulting in an attractive and rust-resistant gunmetal gray color. The final process was the rubber dip to complete the handles.

Prototyping running shoes

Canton, MA-Reebok is successfully utilizing 3D Systems’ (Rock Hill, SC; www.3dsystems.com) DuraForm Flex Plastic for prototyping a number of its products. Used in the company’s selective laser sintering systems, the DuraForm Flex Plastic reportedly is flexible and soft yet tear-resistant and durable. Reebok uses this thermoplastic elastomer material to create complex, functional prototypes of footwear, sandals, and athletic equipment.

Reebok produces parts at 0.15 mm layer thickness, which is comparable to other flexible materials, yet DuraForm Flex Plastic delivers an exceptional surface finish and the ability to create parts with fine-feature details. By further reducing layer thicknesses from 0.15 mm to 0.1 mm, the material offers up to a 33 percent improvement in resolution. The parts produced are able to withstand repeated bending and flexing as well as harsh functional testing. By varying machine process conditions, this material can consistently create parts with optimized Shore A hardness ranging between 45 and 75.

“Our application is different than most,” says Gary Rabinovitz, rapid prototyping lab manager at Reebok. “We build one or two confirmation samples. The parts are very flexible and can be painted, so we get the look and feel of a real shoe. For this type of application, we prefer DuraForm to all the other materials available on the market.”

Paul Bates, director of advanced process engineering for Reebok International, explains that the material “gives us a much more consistent and stable material for our flexible parts. We can setup large complex builds that run overnight with the confidence that we will have good results in the morning.”

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