ST. LOUIS — Structural foam molder FM Corp. has driven the use of plastics into a breakthrough application for the passenger bus industry.
The Rogers, Ark., company, known for its medical and electronics parts, has started making plastic cargo and passenger doors for major tour-bus operator Motor Coach Industries Inc. of Oklahoma City.
The contract is not only the first one in the transportation field for FM, it also marks possibly the first plastic doors for the bus industry, said David Shallenberg, manager of manufacturing services for FM. The doors are expected to be used in new bus production by the third quarter of this year, Shallenberg said.
``It's a total metal replacement project,'' Shallenberg said. ``With our process, we're actually able to reduce by half the weight of cargo doors and passenger doors for over-the-road buses.''
The cargo doors, made from a polycarbonate and ABS blend, and the passenger doors, using a 10 percent glass-filled PC, will be molded on a new, wide-platen structural foam press that FM bought a year ago, Shallenberg said March 30 at the Society of the Plastics Industry Inc.'s Structural Plastics Division meeting in St. Louis.
The machine, made by Wilmington Machinery in Wilmington, N.C., features dual 6-inch extruders with two 75-pound shot accumulators and a multinozzle injection manifold. The press has a clamping force of 750 tons.
The contract, which was awarded four months ago, will allow FM to mold six doors per bus. Each plastic door weighs as much as 25 pounds less than its metal counterpart, Shallenberg said. With each bus expected to travel as much as 500,000 miles, Motor Coach Industries expected to receive significant fuel savings due to the weight drop, he said.
Traditional injection molding was ruled out for the structural door panels. The structural foam process allows for greater strength and durability, he said.
FM will make a 7-inch-high plastic skirt for each door. The skirt, placed at the bottom of each door, protects against damage from rocks and road debris, Shallenberg said. The cargo doors are ready for production, while the passenger doors must undergo parts verification.
MSI Mold Builders Inc. of Cedar Rapids, Iowa, will make the tools for the bus doors. FM will mold the parts at its 165,000-square-foot plant in Rogers.
The company, which employs 300, has 14 presses at its 49 molding stations, Shallenberg said. The structural foam presses can handle shot sizes from 4 ounces to 150 pounds. The firm recorded sales of $32 million in 1997.