Clemson University, one of the top 20 universities in the country according to US News and World Report, is home to the nations only graduate Department of Automotive Engineering located at the Clemson University International Center for Automotive Research (CU-ICAR). In addition to excellent research and faculty, CU-ICAR attracts many students and employers with its Deep Orange project. Deep Orange is a two-year vehicle prototype project that students are required to complete in order to receive a masters or Ph.D. in automotive engineering. From the time they enter into the program until graduation, students are immersed in the hands-on process of vehicle design, engineering, prototyping and production.
In 2011, CU-ICAR kicked off its fourth Deep Orange project with a sponsorship from BMW Manufacturing, Co. who also provided the main project objectives. BMW required the Deep Orange 4 vehicle to be based on BMW X3, targeting a niche market of performance-oriented SUV customers who want both best-in-class utility and space as well as a luxury design and experience. BMW also required a cost-efficient, low-volume manufacturing plan that wouldn’t negatively impact its existing production processes.
First, students conducted market analysis and generated three personas to represent the consumer demographics and lifestyles who would buy a transformative vehicle from BMW. Using the personas, they formed use-case scenarios to help define the interactions the target market would have with the vehicle and create the ultimate driver experience.
After the persona analysis, the team defined two main design goals:
- Compact crossover with pickup capabilities – To fit the urban lifestyle of the personas, the vehicle would need to be compact and have decent fuel economy, and at the same time, capacity for hauling and a large cargo space—a unique solution in the current small crossover SUV market.
- Versatility – In order to obtain the utility of a pickup truck in a compact vehicle, the design had to include functionality to easily transform and generate more space when applicable.
The resulting design had many compelling features, distinct from the BMW X3, including:
- Sliding roof – The sliding glass roof transforms the trunk compartment from an enclosed area into an open-bed configuration with the utility of a pickup cab.
- Rear window – The rear window mechanism is located behind the rear seats to seal the cabin and protect passengers when the vehicle is in truck mode. It also folds down to allow for additional cargo space.
- Rear seats – The rear seats can be adjusted to lie flat for the load floor.
- Rear doors – To enable access to the open trunk space like a truck tailgate, the more common rear hatch trunk was replaced with two doors which open on a hinge.
After landing on a design concept, the CU-ICAR team began working on a prototyping strategy and manufacturing plan. Since they were engineering a variation of the BMW X3, they didn’t have to start from scratch, but to accommodate the transformative design, the vehicle needed a new tailgate, roof, panels, side frames, guide rail and windows.
The team originally designed the transformative parts to be manufactured with steel stamping, in which pieces of flat sheet metal are formed between a tool and die. But when the design files were quoted by a metal forming shop, the Deep Orange budget ultimately couldn’t support the high costs of building these large parts in steel. Moreover, the metal shop’s lead times did not meet project deadlines.
“Even with the excellent relationships we have with manufacturing suppliers, it didn’t make sense to steel stamp these large parts,” said Bill Sowerby, Deep Orange program director. “Once the students realized traditional manufacturing was out of the question, they had to go back and rethink how to design and build the prototype.”
That’s when a student suggested using additive manufacturing process to rapid prototype the parts. The parts didn’t need to be built in steel, but needed to be strong enough to support the weight of the vehicle and a heavy structural foam that would be applied to the interior. The students decided to build the parts with the Stratasys Fused Deposition Modeling (FDM) process because of its strong engineering-grade thermoplastics and the ability to produce large parts by building separate sections and bonding them together with the same thermoplastic. The students sent the design files to Stratasys Direct Manufacturing to quote FDM services and discovered the parts would be 75 percent cheaper and ready 3-4 months faster compared to steel stamping.
“Conventional manufacturing processes are expensive and require long lead times. My team and I were facing the challenge of getting the parts built in the shortest possible time within the budget constraints. In addition to that, we were dealing with extremely tight dimensional tolerances and even a few millimeters of deviation from the CAD models would have resulted in either the parts would not align correctly or would leave with big gaps. We investigated other alternate options and talked with various body shops,” said Ashish Dubey, Project Manager Deep Orange 4. “During our research we came across the FDM process which is a rapid manufacturing process. We chose FDM because the cost and time to make all the parts was drastically lower than the conventional sheet metal forming processes. The final parts were as good as it can get in terms of geometric dimensioning and tolerances (GD&T). Overall it was great working with the Stratasys Direct Manufacturing (SDM) team and at the end of the day we got a chance to learn about a new technology which could very well be the future of low volume production parts.” –
By switching to additive manufacturing, the team had to consider factors unique to the alternative process. SDM recommended adjusting the part design for the FDM process to ensure they met tolerances, lined up with the original BMW X3 parts on the bottom half of the vehicle and were properly configured for secondary operations.
For example, changing the orientation or angle the layers of material are extruded onto the build platform would help create a strong, but smooth surface finish, ready for sanding, priming and painting. The team also slightly increased wall thicknesses in various areas of the part to increase strength and to compensate for material that would be removed while sanding and smoothing the surface. Lastly, the parts larger than 36 x 24 x 36 in. (the size of the largest FDM machine) had to be split into separate pieces with dovetail joints in design to increase tensile strength between sections that would later be hot-air welded together.
“FDM is a very different process than steel stamping so the redesign was important. I helped the Clemson students determine the best orientation and placement for the bonding joint to ensure we would accurately build and weld the parts together to meet dimensional accuracy,” said Eric Quittem, senior project engineer at SDM. “With thicker walls, we also knew there would be some slight stair stepping on the surface of the parts which is inherent with the layering process. This was new to the Clemson team and we reassured them that the layer lines could be removed with secondary operations.”
Stratasys Direct Manufacturing built 14 parts for Deep Orange in ABS-M30 on the Stratasys Fortus 900mc 3D Production System , including: four pieces of the tailgate, four pieces for the side frames, four pieces for the roof and rear window and two side panels. SDM’s finishing department sanded the parts smooth to prepare the parts for automotive primer and paint. Finishers also hot-air welded sections of the tailgate, side frames and side panels at the dovetail joints.
The students successfully integrated and assembled the functional prototype vehicle in time for its debut at the Center for Automotive Research Management Briefing Seminar in August 2014. BMW Manufacturing was impressed with not only the Deep Orange 4 design, but also the manufacturing plan.
“The ability to integrate more low-volume models without incurring capital- intensive retooling costs and efficiency losses will be key to success in the future as we strive to respond to changes in market needs faster and with more flexibility,” said Rich Morris, vice president of assembly, BMW Manufacturing. “The students working on this phase of the project did an excellent job of keeping costs down while finding optimal integration opportunities.”
SDM and 3D printing helped keep Deep Orange 4 on track and within budget. “Vehicle prototyping is just one of many 3D printing applications creating efficiencies and producing better parts in the automotive industry. It’s important for future automotive engineers to learn how to design for and use the technology because it’s becoming more and more of an integral process in automotive manufacturing,” said Mick Schrempp, account manager at Stratasys Direct Manufacturing who worked with Clemson University.