GM and supplier tighten windows and costs
By Staff -- Purchasing, 11/19/1998
Not too long ago, car maker General Motors was having problems with leaking windows on some car models. "We were always fighting with wind noise and water intrusion on quarter window assemblies," says Larry Filipczak, senior project engineer for door systems in GM's North American Operations Car Group.These design issues weren't even the whole problem. GM also had to consider logistics and cost. There were three suppliers that provided parts for the rear quarter windows: a PVC encapsulation supplier, metal form roll supplier for division posts, and a rubber supplier that provided glass run channels. GM still had to assemble the parts to create the quarter windows, which meant coordinating these three suppliers in addition to hundreds of production suppliers.
Another design challenge was the sealing capability of PVC (polyvinyl chloride), the industry standard of the time. "PVC doesn't provide the sealing characteristics for wind noise and cold-weather performance that we needed," says Dave Todd, senior project engineer at General Motors. GM had to find a solution that improved the design without raising costs.
To assist GM in developing a model that would solve the problem without adding costs or disrupting the supply chain, supplier Harvard Industries put its Kingston-Warren division to work. The company had been supplying epdm (ethylene propylene diene monomer) glass run channels to GM. Ultimately, Kingston-Warren engineers suggested a subassembly design.
Now Harvard Industries provides an assembly that includes the three components in a single encapsulated window and sealing module. To achieve this, Harvard Industries took several steps, including signing an agreement with a leading European manufacturer to make the tooling for glass encapsulation molding.
To eliminate sealing problems caused by PVC, Harvard Industries replaced PVC with epdm rubber. By using epdm for the quarter-window trim, division post, and glass-run channels, the assembly is highly durable. In the manufacturing process, the three components are placed in a 350-ton rubber injection press and encapsulated with edpm. The result is an appearance that is more uniform in color and texture.
The assembly exceeds GM's criteria for containing manufacturing and logistics costs. Harvard Industries delivers a finished product to GM, so the automaker does not need to coordinate numerous suppliers. Also, the assembly process for GM is substantially easier, as the encapsulated vent window is flush mounted in one step. The attachment is seamless, tight, and solid. The elasticity of the adhesive method reduces the angular torsion by 30%, resulting in fewer installation problems, a decrease in damaged parts, and faster assembly.
"The ability to encapsulate the rear-door glass and glass run channel resulted in considerable savings in assembly, shipping, and warranty costs," says GM's Todd. In fact, General Motors has used Harvard Industries' modular design on all but two new sister vehicle applications, beginning with the 1997 Grand Prix, Chevrolet Malibu, and Oldsmobile Cutlass models. By the year-2000 model year, GM will include this technology on more than 1.2 million vehicles per year
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