Dream Cars Come to Life
Direct digital manufacturing speeds the 3Rs—rebuild, restore, and replicate.
Step outside of the high-volume, highly automated world of production automotive manufacturing (which is well documented in this issue of Manufacturing Engineering) for a few minutes, but not too far out. There’s a fascinating world populated with car enthusiasts who restore, rebuild, replicate, and race some of the sleekest cars that ever rolled out of someone’s garage or specialty build shop. Their “rides” include muscle cars, replicas, newly built high-performance NASCAR race cars, or open cockpit road racers. And they all share one thing in common—they all need fast turnaround and economical fabrication of components and the fixturing to produce them. Some simply replace original parts; others upgrade components to handle a more powerful engine, customize the car, or meet new regulations.
Additive manufacturing (AM) technology continues to grow in importance as a time-saver and a budget extender both for direct digital manufacturing (DDM) in-house or by relying on service bureaus. The RedEye On Demand digital manufacturing service has more than 100 fused deposition modeling systems manufactured by its parent company, Stratasys Inc. (Eden Prairie, MN), and is capable of quick turnaround, processing CAD data directly into prototypes, fixturing, or final parts.
Fused deposition modeling is an additive-manufacturing process that creates plastic parts by applying real production-grade thermoplastics, the same ones used in injection-molding processes, in layers from the bottom up. Repeatability, quality parts appearance, and reliable function are easily achieved in low-volume production applications for components or fixtures.
Roaring Forties (RF; Thomastown, Victoria, Australia) is a manufacturer of replica kits for one of the most famous GT cars, the Ford GT40. The GT40 was Henry Ford II and Ford Motor Co.’s (Dearborn, MI) entry into road racing in the 1960s. The GT40 name is derived from Grand Tourisme, which measures 40" (1.02-m) high at the windshield. The GT40 is justifiably famous for winning the 24 Hours of Le Mans four successive years from 1966 to 1969.
Roaring Forties provides Individually Constructed Vehicle (ICV) kits to enthusiasts who build the cars themselves. (In Australia, it is illegal for Roaring Forties to assemble the car.) The GT40 can be built by enthusiasts in four stages at a cost, according to RF, of about AU $90,000. Roaring Forties provides every component required from start to finish in some 160 separate kits for sequential build.
When an emission regulation changed, Roaring Forties was required to fit a new engine into the existing chassis. One of the critical changes was to the brake and fuel-line harness. The companies turned to RedEye On Demand, because of its experience with its DDM capability for building parts for development testing and end use. In this case, RF recognized that the manufacturing technique could be used to build a simple jig for the fuel line which could be used both as a fixture for aligning assemblies and as a “go/no go” gage.
The ability to manufacture parts like jigs, fixtures, and tools on demand allows processes to be optimized and implemented in a shorter timeframe. Parts for fixturing and tooling in the automotive manufacturing environment need to withstand the harsh environment of high temperature and vibration and be light weight and portable. And, as in the case of Roaring Forties, when parts require design changes, fixtures have to be altered quickly.
When Roaring Forties co-owners Jonathan Klopsteins and Paul Bottomley heard that digital manufacturing technology could be applied to jigs and fixtures, they gave the go-ahead to give it a try. RedEye looked at the ABS prototype of the harness and how it was manufactured and suggested using polycarbonate (PC) material, reasoning that the higher melting point would allow Roaring Forties to solder brackets on prior to brazing. Because the jig isn’t stressed during use, RedEye engineers also suggested building it with a sparse fill, saving build time, piece cost, and materials.
Fixtures are most frequently used in holding, assembly and alignment, calibration, test hardware and prototyping. RedEye On Demand saved the Roaring Forties team time and money on fabrication and assembly tools. Digital manufacturing technology reduced fixturing manufacturing time to days and eliminated machining with its longer turnaround time of four to six weeks for machining and assembling metal, wood, and other common fixturing materials.
According to Roaring Forties, once you hand a part to a customer, there are a multitude of ways of perceiving quality. Parts not only need to look good and be fit for the purpose at hand, they need to work well as part of an overall assembly. “If one part doesn’t mate up with another, it will result in an unhappy customer—something we strive to avoid,” the co-owners aver.
You might not think about appearance as much as function when it comes to NASCAR cars, but when Joe Gibbs Racing (JGR; Huntersville, NC) needed an enclosure for heater-control components, appearance and function were both considered essential. The challenge for Joe Gibbs Racing was to produce a part that would act as an enclosure for the heater control components to be used in the cars during races each week. These components include wires, gages, and switches. The enclosure itself would be composed of two pieces. The main body would include recesses for the switches and gages with enough room on the inside to route wires and other electrical components. The second part would be a thin-walled backing plate used to close the open face of the main body.
The part itself needed to be strong enough for racetrack use and accurate so that the gages would fit well in the recesses designed for them. It would replace a crude hand-fabricated piece that was functional but not visually appealing. In addition, the old part required fabrication time and CNC time that the racing team needed to eliminate.
“Our product has to be performance-
driven, but it also has to look good.”
Joe Gibbs Racing, which has its own CNC machine shop, also has a Stratasys machine, a Fortus 400mc 3-D production system. It knew the capabilities of direct digital manufacturing, and had added the machine for quick turnaround on prototyping parts, especially using thermoplastics like polycarbonate and polyphenylsulfone. It takes just 15 min from completion of CAD design to start building the prototype. JGR, however, determined that its in-house resources would not be adequate to handle production of the required large number of parts in the 10 days until the racing season was scheduled to begin.
JGR contacted RedEye On Demand to produce the part, because of its fast turnaround and choice of materials available to provide the right strength and surface finish. The final parts were delivered to JGR within one week without involving any JGR personnel involvement. The 30 new parts took about 30–35 hr each to produce. Traditional manufacturing might have taken four to six weeks. The parts, which were made from ABS black, didn’t require additional surface finish work such as sanding or painting. This last point was particularly important from JGR’s point of view. “Our product has to be performance-driven, but it also has to look good,” explains JGR’s Mark Bringle. “We can’t have a fast car that looks terrible. It’s not good for the sponsor. With RedEye’s service, the products were appealing, the functionality was perfect, but the big thing was the delivery time.”
In custom restoration, one change by Ivan Viduka to his 1970 Ford Mk1 Capri—replacing a standard engine with a 3.0-L quad cam to compete in the Australian Historic Racing Series—led to the need to customize other components. A new high-performance air intake system was needed to ensure top performance. With no major financial backing, Viduka’s goal was to reduce costs associated with low-volume tooling and machining, so he approached RedEye On Demand for their digital manufacturing services.
“The ability to manufacture parts like jigs, fixtures, and tools on-demand allows
processes to be optimized and
implemented in a shorter timeframe.”
An initial design concept for the intake plenum was developed with CAD software and sent to RedEye where a rapid prototype was created using polycarbonate (PC) material. Due to its suitable heat-resistance properties, PC possesses lower yield strength than aluminum, which would normally be used for this application. A suitable thickness was applied to the design with the aid of CAE analysis to ensure the plenum component was able to resist maximum engine vacuum changes during snap throttle events and backfire.
No additional machining was required, because all of the intake plenum features and holes were digitally manufactured using PC. All mounting holes were heli-coiled for additional strength so correctly sized fasteners could be used and sealing of the plenum was maintained. The initial design was used for development testing and included idle speed control, PCV, and vacuum bosses ready to go without addition machining required.
As part of the testing phase, improvements to the design were identified. In this case, the new design included a second throttle body unit that increased horsepower while bosses and ribs added increased structure to the lower mounting surface. After testing of the second design, the model was updated with more beneficial changes and a new prototype was created using sparsely filled ABS to produce casting patterns. A split plenum design was favored to avoid the need for an additional core model. The two halves of the plenum were machined and welded together. Working with good engineering and the team at RedEye On Demand, Viduka was able to develop more than 350 hp [261 kW], giving him enough power to drive circles around his competition.
The ability of fused deposition modeling to speed automobile restoration, customization, and production is nowhere illustrated better than in the case of a Pit Viper, a GT500E-inspired Mustang that started life as a 1968 Fastback. Brook Phillips and his team at Total Performance Inc. (Wichita, KS) began the process by selecting 3-D scanning and the fused deposition modeling technology for nine components: two pair of side scoops, two hood scoops, front grill, rear bumper, and center console. The goal was, of course, perfection in fit, finish, and symmetry. To achieve the 1/16" (1.58-mm) precision and consistent flush and gap that Phillips wanted, he turned to Realadi Inc. for TPI reverse engineering and 3-D scanning tools and to Stratasys for rapid prototyping and direct digital manufacturing.
Through its RedEye On demand service group, Stratasys built one-quarter scale and full-size models and manufactured the finished parts for the Pit Viper. The process showed that restoring vehicles no longer needs to be a laborious process. Phillips and his team found that the procedure can be accelerated by the DDM technology, saving both time and money, while meeting critical symmetry and fit objectives. ME
This article was first published in the September 2011 edition of Manufacturing Engineering magazine. Click here for PDF.