For Fiat Chrysler Automobiles (FCA) US LLC, 3D printers are a common tool engineers use to prototype and test designs at the 5.4 million square foot Chrysler Technology Center (CTC). Engineers here have been using additive manufacturing technology since 1989. In one example, the design engineers used 3-D printing to open a unique window on the world of axle development.
“Efficient axles are critical to our powertrain strategy,” says Jeffrey Lux, Vice President-Transmission Powertrain. “For the customer, they offer an economical way to improve total powertrain efficiency. We’ve introduced six new axle families since the foundation for FCA US was established in 2009.”
Part of the process of developing new axle families is to test lubricant flow in the differential housings. But conventional methods of evaluating oil flow were cumbersome. “We needed to take a CNC to make holes in the differential housings,” says Tom Sorovetz, casting engineer, Chrysler, “ then put in plexiglass in those holes, and then use a flashlight to try to see where the oil goes through the unit while it undergoes testing on a dynamometer.”
Viewing was further complicated by the tendency of the standard axle lubricant to turn milky white in color as motion introduced air into the lubricant.
“We were not getting the information we needed,” continues Sorovetz, who has worked with a number of additive manufacturing systems over the last 26 years.
Thus, the decision was made to use additive manufacturing to print a see-through plastic component exclusively for test purposes. Additive manufacturing would help the designers correlate the virtual analysis of fluid flow.
The 3D printing material chosen was Somos WaterShed XC 11122 resin. The engineers used stereolithography to build clear differential housings. After the 3D print build, the housings are polished and the bearing surfaces are machined on the inside. Ring gear and pinions are then added.
The resin is Somos WaterShed XC 11122 material. It is a low viscosity liquid photopolymer that produces strong, water-resistant, ABS-like parts. This resin looks like true, clear-engineered plastic.
The additively made differential housing is then put on a dynamometer. The engineers run no load tests at speeds ranging from 60 mph to 100 mph, including tipping the housing five degrees up or down to simulate off-road driving. The engineers can see through the housing, and watch lubricant distribution. They can see lubricant puddling, dry areas, and other issues with the housing design that ineffectively distribute lubricant, which all could potentially lock up the axles.
Engineers at the CTC have used 3D printing technology routinely. Transfer cases are another design where it comes in handy. This center is an amazing facility for an engineer. It is the auto industry’s only headquarters building where a vehicle design can go from a napkin sketch to production prototype to advertising campaign – and everything in between – under one roof. Its 129 dynamometer cells run 24 hours a day, seven days a week. It includes an aerodynamics testing facility that generates the highest wind speeds of any domestic OEM’s wind tunnel, speeds to more than 160 mph.