ST. LOUIS — Continuing its quest to be a leading force in low-pressure structural foam and structural web gas-assisted molding in North America, Horizon Plastics Co. Ltd. recently installed its 11th multinozzle structural foam/structural web machine.
The 750-ton, two-screw Uniloy-Springfield machine gives the Cobourg, Ontario-based company the ability to run two colors, two types of plastic resin or two processes — structural foam or structural web — at one time, said Brian A. Read, Horizon vice president. He spoke in an interview at the SPI Structural Plastics Division's Applied Plastics Technology and Design Conference, held March 29-April 1 in St. Louis.
``We are Canada's largest structural foam molder,'' he said. ``And we are one of the largest in North America.''
The new machine features a platen dimension of 86 inches by 130 inches. While Horizon declined to reveal the cost of the machine, such a model typically costs more than $1.5 million.
The structural foam molding process involves a one-step injection of a foaming agent and thermoplastic resins to create a rigid plastic part, Read said. The process can create lightweight products with a strength-to-weight ratio two to five times greater than metal parts.
Because structural foam requires much less clamping force, a 750-ton structural foam press can produce parts that ordinarily would require an injection press with several thousand tons of clamping force, he said.
An occasional drawback to structural foam molding is the resulting ``swirl'' pattern on the surface of the part.
That, Read said, is where structural web gas-assisted molding stands as an advancement in the technology.
It is a process not unlike foam molding but one that injects inert gas into the mold instead of foam. The process forms numerous ribs or ``webs'' that radiate out from the point of injection.
These interconnecting webs support surface skins and help make the molded part strong, lightweight and less costly to produce, and give it a near-Class A surface.
Horizon entered structural web molded automobile spoilers in the conference's new-product design competition.
Read called Horizon's use of multinozzles an advancement for the industry. The injection-side platens have numerous drilled holes leading directly to the mold area.
Injection nozzles can be attached to the holes in any configuration, Read said. The machine can be programmed to inject plastic in sequence through the nozzles.
The multinozzle process facilitates the use of several molds at once on the platen.
``We see the future going toward structural web gas-assisted molding,'' he said.
Using structural foam and structural web molding, Horizon produces pallets, sliding boards for swing sets, and ladders, among other products, at its 140,000-square-foot facility, Read said. The privately held company employs 180-200.