ST. LOUIS—General Motors Corp. has been very good to Siegel-Robert Inc.
A mounting workload with the world's No. 1 carmaker has led to both expansion and award-winning innovation for the St. Louis-based injection molder.
On the expansion front, the company has recently added a total of 200,000 square feet at three plants and is installing nine new injection presses and other automated equipment. The expansion will help it prepare to do work for the launch of GM's 1999 full-size pickup trucks and other light-truck models.
The firm estimates the expansion to cost more than $10 million in buildings and equipment, said Michael Honigfort, Siegel-Robert vice president of product design and methods engineering.
For innovation, Siegel-Robert has developed one of the auto industry's first all-plastic exterior mirror housings that uses coinjection and gas-assist molding in the same assembly. The unpainted, two-piece part eliminates the need for metal or structural plastic brackets to give the fold-away mirror stiffness and stability.
Those mirrors are being used on GM's 1998 newly designed minivans, including the Chevrolet Venture, Oldsmobile Silhouette and Pontiac Trans Sport.
Besides impressing GM, the mirror also won over judges at the 1998 new-product design competition, sponsored by the Washington-based Society of the Plastics Industry Inc.'s Structural Plastics Division. The product took first place in the automotive category during the division's recent conference in St. Louis.
What might have been the clincher for the judges was the marriage of two highly involved molding processes to create a deceptively simple part. Other plastic mirror housings normally include brackets attached either to the mirror's head or mounting applique. Siegel-Robert developed its mirrors for three years.
``We couldn't get the stiffness we needed to replace the brackets without coinjection,'' Honigfort said. ``We eliminated parts, and we eliminated painting. That's where we came up with significant cost and weight savings.''
Besides ridding the mirrors of two heavy brackets, Siegel-Robert employs a high-gloss, molded-in color to give them their black shade. That stamps out the need for painting, a process that can absorb as much as half the cost of some parts.
Other molders could be nipping at Siegel-Robert's heels. Mirror producer Donnelly Corp. of Holland, Mich., now makes all-plastic mirrors that use glass-filled nylon brackets, said Peter Whitehead, Donnelly's manager for outside mirror engineering. Donnelly is developing its own plastic mirrors without brackets, and also is considering two-shot molding using ABS and elastomer materials to make future mirrors.
Siegel-Robert's process underwent considerable design scrutiny before the idea was shopped to GM, said molding engineer Cliff Riley. Parts were subjected to finite element and mold flow analysis. The computer simulations and tests on actual vehicles revealed a part with improved functionality over conventional designs, Riley said.
``The [mirrors] didn't have the weld lines, sink marks or flow lines that can be a problem,'' Riley said. ``We were able to produce a stable mirror.''
Siegel-Robert uses a weatherable polycarbonate/PET blend from GE Plastics for its mirror skin. Using the gas-assist process, the material creates a hollow, lightweight shell to surround the mirror. The mounting applique also is molded from PC/PET.
In a second process, a 30 percent glass-filled ABS is coinjected into the applique as a reinforcing core substituting for the brackets.
The work is performed at Siegel-Robert's 180,000-square-foot Ripley, Tenn., plant on two 600-ton Battenfeld injection presses.
Laser Die & Engineering of Kentwood, Mich., made the two-cavity molds for the special parts.
``The goal was to make a prototype out of aluminum to find the best way to get gas through the part,'' Laser Die plant manager James Perren said. ``But once we made production tools from steel, we had to account for different heat factors and change the gas channels, panel locations and wall stock. I think the final product was well-received.''
Also in the midst of an expansion, Laser Die plans to add about 10,000 square feet of space by August and a high-speed, five-axis computer numerically controlled milling machine that is expected to cut 600 inches a minute, Perren said.
Siegel-Robert is wrapping up its three-plant expansion, including installing nine Van Dorn Demag injection presses, with clamping forces of 500-1,500 tons; four new robotic paint cells; and two computer-controlled, servo-driven coordinate measuring machines.
The project involves plants in Wilson, Ark.; Portageville, Mo.; and Ripley, all of which will make grilles, body side moldings and nameplates for GM's new light trucks, scheduled for production this summer, Honigfort said.
Siegel-Robert recorded about $270 million in North American injection molding-related sales during 1997.