Super Plug, the first one-piece interior door module made entirely of composite thermoplastics, has moved from concept to actual production on six 1997 General Motors Corp. vehicles.
The award-winning design has been heralded since its 1995 introduction for its substantial cost and weight savings. The module consolidates as many as 61 parts, mostly made from metals and including window regulator backplates, wire harness attachments, armrest supports and speaker mounts.
However, until recently, no vehicle lines were equipped with the Super Plug, and no time frame had been released for the product's launch.
Behind the scenes, however, General Motors officials had been working since 1992 with its automotive systems division, Warren, Mich.-based Delphi Interior & Lighting Systems, and materials supplier GE Plastics of Pittsfield, Mass., to add the module to several new and redesigned models. The vehicles were chosen so the carmaker would not have to revamp existing production lines or components.
``It would have required a considerable investment to change a car line midstream,'' said senior project engineer Brian Staser of Delphi. ``That influenced our decision on when to go ahead with this.''
GM has added the Super Plug to its new 1997 minivan series, including the Chevrolet Venture, Pontiac Trans Sport, Oldsmobile Silhouette and Opel/Vauxhall Sintra, which is sold only in Europe. The Super Plug also is used on GM's retooled Chevrolet Malibu and Oldsmobile Cutlass.
Bringing the project to fruition required General Motors to design a new piece of door-in-white sheet metal, which is the door-panel skin that slips over the interior module, with sufficient space to accommodate the Super Plug.
``Normally, inner door panels contain lots of holes to fit the parts,'' Staser said. ``The Super Plug needed to fit into one big hole designed carefully with proper edged treatments and formations of sufficient structure to maintain rigidity.''
Meanwhile, Delphi set up a Super Plug manufacturing facility at its Columbus, Ohio, operations center. The modules, which are made from 30 percent glass-fiber-reinforced polycarbonate/polyester resins from GE Plastics' Xenoy line, are injection molded using gas-assist techniques. The dual-and single-cavity molding equipment has clamping forces of 700-1,500 tons.
The base module is then shipped to a just-in-time preassembly facility in either Doraville, Ga., or Oklahoma City, where General Motors assembly plants for those vehicles are located. Once there, Android Industries, a Whitmore Lake, Mich.-based vehicle assembler, completes production and tests 14 Super Plug variations. The modules are then sent to the GM plants and plugged into the door-in-white outer panels.
Super Plug models include those featuring either power or manual windows, power or standard door locks, base or uplevel speaker systems, and right- or left-side driver components.
Super Plug might represent only the first, albeit giant, step for thermoplastic door panels. John Madej, industry manager for door systems at GE Plastics, said the company is working with suppliers to develop a single, integrated panel marrying the interior module and its outer skin. A product could be five years away, Madej said.
Lear Corp. of Southfield, Mich., is developing a similar integrated product, which the firm plans to introduce on a test car in February at the 1997 SAE International Congress and Exposition in Detroit, said spokeswoman Leslie Touma.
``Carmakers are looking to suppliers for the next level of modular design,'' Madej said. ``I think that Super Plug came out at the right time in the industry's evolution. I can't wait to see what this leads to in the future.''
Both Delphi and GE Plastics said there is considerable interest among other carmakers in the Super Plug, although the companies declined to be more specific.
``It's public knowledge that Delphi wants to do 50 percent of its business outside General Motors by the year 2002,'' Staser said of Delphi's plan to become a stand-alone company. ``All I can say is that we're talking globally to other carmakers about door panels.''
If carmakers are interested, cost and weight reductions could be the reason. Delphi estimates that total system costs with Super Plug are 5-10 percent lower than similar door components, while the module is about 3.3 pounds lighter per door. The consolidated component also reduces vehicle assembly time, lowers operating noise, limits corrosion and enhances recyclability, according to Delphi.
Weight and cost savings helped sell General Motors on the idea. Norman Pilcher, vehicle chief engineer for minivans, said the carmaker had considered using metal-based door modules in the past but rejected the idea.
``Modular door hardware has been tried before with metal,'' Pilcher said. ``The plastic modules give us better sound-dampening properties from their compositives and significant mass reduction over comparable metal modules. Super Plug has done everything we've expected for it.''
Pilcher added that General Motors is considering using Super Plug with future new or redesigned car lines, although he could not give specifics.