Press Release
Up to the challenge
As Chrysler LLC prepared to unleash its new, limited-production Dodge Challenger, prototype plastic components loomed as a stumbling block to launch - until one rapid prototype shop stepped up to the challenge
A CAD workstation can blend contours and shapes together to provide a virtual appearance, but it can’t measure accelerated pulse rates at the sight of a sleek new profile. CAM-laced technology can establish fit and function, yet can’t slow the rush of running one’s hand over a sporty interior. And extensive engineering analysis will guide and test performance criteria, though only the throaty rumble and powerful resonance of the engine’s start-up will quicken the heartbeat.
All the testing, lab work, computer analysis and studio design work cannot equal the enthusiasm of the energized consumers waiting for the new ‘retro’ Dodge Challenger from Chrysler LLC. That’s why project leaders for Chrysler were determined to not only thoroughly test the vehicle’s components and systems’ performance, but also to construct prototype vehicles to accurately gauge market response.
But therein was the problem - a limited production schedule of only five to six thousand vehicles per year where many prototype shops were not ready, willing or able to invest time, labor and dollars to develop concept tooling, processes and prototype construction. Included among the needed parts to complete vehicle models were both the front and rear wrap around fascias measuring a touch over six feet long by 28 inches high (with grill cutouts, lighting openings, side markers, and options for single and dual exhaust packages) and the rear left and right tail lamp assemblies and the central light bar spanning the rear deck.
At about this same time, Steve Kelly, sales engineer with the 3-Dimensional Services Group, a Rochester Hills, MI-based prototype firm with specialties in injection molding among many other manufacturing disciplines, was wrapping up another smaller project for Chrysler, developing close out plugs and cosmetic fastener covers to complete interior stylings. Mr. Kelly overheard the problems of Chrysler’s Challenger team, and the possibility of prototype fascia pieces and lighting components not being ready for four months, as other prototype shops and production houses had offered.
"These proposed time frames for prototypes were unacceptable to Chrysler," Kelly says, "and frankly, they were running out of options...quickly. Our design and engineering crews at 3-Dimensional Services and group member Urgent Plastic Services (also in Rochester Hills) reviewed the parts required, the process steps, the tooling needs, and then we went back to Chrysler with a proposal to deliver the prototypes in eight weeks. Two days later we had an order in hand and CAD files supplied by Chrysler and their design/build partners. The process to develop both injection mold tooling for the tail lamps and light bar systems, consisting of nearly 80 individual components, and RIM-style molds, measuring approximately eight feet long by four feet deep and weighing up to 2,400 pounds along with inserts and variations for the fascias, was underway."
"Within the pledged eight week time period, we started delivering the first of the front and rear fascia assemblies to Chrysler. Within that same period we also provided the entire125 sets of the tail lamp and light bar appliqué. The project included adhesive assembly of the lighting components, replicated reflex lens construction, wiring harnesses, air dams, grill components, lamps and side markers, plus all mounting brackets and supports. Chrysler stylists and engineers were able to test the components for fit, function, aesthetics and to run simulated assembly procedures through their Technical Center test facilities. And, the early prototype completions provided a chance to gauge consumer reactions and response to the final, critical design elements."
3-Dimensional’s strength is rooted in the combination of technology and craftsmanship which allows it to produce parts quickly and efficiently. Though all prototype parts are constructed using processes as close to production-like techniques as possible, 3-Dimensional Services also utilizes advanced systems to expedite prototype builds. For example, with the fascia assemblies, 5-axis laser cutting machines were used to trim out openings for light packages, while SLA (stereolithography apparatus) ‘positive’ models of the fascias were employed to help create the ‘negative’ mold patterns. These models were formed from multiple parts that were then pieced together to form a single fascia replica. At the same time, skilled pattern makers and tooling engineers hand finished both the SLA model and epoxy pattern surfaces, plus high speed CNC machining was used to generate both A- and B-Class surface finishes for the tooling so resulting polyurethane RIM parts would have similar, high class and flawless finishes.
As mentioned previously, the design of the pattern for the rear fascia was made more complicated in order to accommodate the various engine and exhaust options that would be available. For some models, a small half-moon arc was required to provide clearance for single pipe exhaust systems; other fascias were provided with dual arc cutouts for twin exhaust systems...some side by side, others had one exhaust pipe on each side of the car. This somewhat innocuous exhaust option, however, required major tool adaptations, multiple inserts and significant design complexities.
Another breakthrough technology that the 3-Dimensional Services Group technicians have developed and refined in order to speed up the prototype build process especially for injection molded pieces, has been in the constructing of the injection mold tooling. To minimize delays and operations waiting for tools to be completed, the companies use what they call E-Z Cut aluminum alloy for the mold tooling. "Over many applications we’ve tested multiple aluminum alloys and have found this one holds up well in low to medium volume molding applications," Kelly remarks. "The speeds at which the aluminum can be cut, however, helps to reduce machining times by 50% or more as compared to steels. Coupled with today’s high speed CNC machining centers, that means faster completion of tooling, resulting in faster injection molded pieces."
In addition, employing new material technologies, major sections of the fascia patterns were constructed from and shaped using Ren Shape? 450, a modeling material of cured polyurethane specially formulated to be an easy-to-machine, dimensionally stable material, ideal for use with CNC machining equipment. The use of the Ren board and its machining characteristics were instrumental in producing the smooth, A-Class visible surfaces for both the front and rear fascia sections.
Another advantage 3-Dimensional Services brought to the Challenger projects was seen in the lighting components, and the many years of experience their technicians have in working with and simulating the reflex properties of the lenses in order to accurately replicate overall vehicle appearance. Although the reflex levels and performance conditions of the tail lamps are critical and must meet government mandated standards - to produce an actual reflex specification is a complex operation of plating and polishing pin ends to mirror like finishes—the company’s engineers have developed an advanced high speed CNC machining program that produces near-reflex like surfaces and reflective prism geometries that create lenses with production quality and appearance.
To finalize the total affect of the lighting systems and tail lamp assemblies, 3-Dimensional Services Group associates, using their own in-house injection molding equipment, including an 850 ton unit and a 500 ton system, developed insert molding tools that generated a virtual no-line transition from the clear backup lighting lens and the stop/turn signal red acrylic material.
"Even when fabricating production tooling," Kelly points out, "it can be difficult to produce pieces without a readily apparent line between different molded colors, but to achieve the desired visual and aesthetic results is critical, and in the prototype parts as well as final production. It’s just one more technique that our tooling engineers have developed for prototype parts that aid our customers’ engineers, stylists and designers, and marketing strategists in making their product decisions."
To complete the Challenger fascias and lighting project, 3-Dimensional Services Group developed assembly procedures, including adhesive application methods, gasket insertions, and the affixing of appliqués within the fascia pieces. Mr. Kelly also notes that the prototype shops designed leak testing systems for the lighting components and provided wiring diagrams that could be useful for establishing production assembly procedures down the road.
"We were able to not only provide the prototype parts Chrysler needed in about half the time they were being quoted by other shops,” says Mr. Kelly, “but, in addition, the whole package developed by 3-Dimensional, including tooling designs, process standards, accessory packages and assembly data, has helped the automaker beat its competition to the showroom floor with an exciting new vehicle that may energize their customer base."
Since its founding in 1991 as 3-Dimensional Services, the firm’s mission has redefined prototyping - the ability to manufacture complete, production-like prototype parts in a rapid time frame. Now, as part of the 3-Dimensional Services Group, the company along with affiliates Urgent Plastic Services and Urgent Design & Manufacture, provide prototype services for virtually all process disciplines that, in addition to injection molding, and stamping, includes laser process cutting and welding, CNC machining, robotic and manual welding, hydroforming and tube bending, vehicle frame fabrication, vibration welding, casting and pattern fabrication, RIM tooling, rapid modeling, high definition stamping of exotic alloys, and assembly operations.
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