In the next few weeks, a Fergus Falls, Minn., company will begin manufacturing low density polyethylene paddle boats and swim rafts on a French rotational molding machine equipped with infrared heaters that is making its debut in the United States. Shoremaster Inc. bought the machine in March from Datome of Ollioules, France, and, with the help of a Datome engineer, put it together in Fergus Falls. The rotomolding machine is Shoremaster's second; in 1991, the firm began making LDPE plastic floats for its commercial marinas on an FSP clamshell. From that captive operation, it branched into proprietary and custom plastic molding.
Electric cooperative Otter Tail (County) Power Co., also based in Fergus Falls, introduced Shoremaster to Datome. Now the rotational molder will license the technology for Datome in the United States and build the machines for third parties in Fergus Falls, where it has four plants, said Dennis Tuel Jr., who owns Shoremaster with his father, Dennis Sr. The French firm already has sold 12 of its machines in Europe.
The Datome machine features all-electric infrared heating technology, which allows precise oven-temperature control in deep cavities, according to Rob Katzenmeyer, plastics division manager at Shoremaster.
``If you have a deep hollow part, you can put an infrared bulb right in the mold, which helps you maintain more uniform wall thickness down in the cavity,'' he said recently by telephone. ``It heats just the mold, not the air around it.''
That process means the building does not become hot, since there is minimal heat released when the oven opens, he said.
Katzenmeyer described the process like this: The oven spins for its primary rotation, while the molds inside rotate as well. Once the heating cycle is completed, the door opens and a mold transfer system tips into the oven and grabs the mold frame. The pendulum swings back to a four-station carousel, the carousel pivots and the mold frame, with the molds in it, spins before high-velocity fans for cooling. At that point, the transfer system grabs the next mold frame and tips it into the oven for heating.
The other two stations are for workers who, at floor-level, put the molds in and take the parts out, controlling the mold frame by remote. The machine also allows in-mold foaming without using a drop box.
``It's a continuous high-production machine,'' said Shoremaster President Erik Ahlgren, who noted that custom work makes up just 10 percent of the firm's undisclosed plastics sales.
The plastics business focuses mainly on products the firm can sell through its U.S. dealer network, such as the proprietary paddle boats and swim rafts. If those lines do well, the company may buy another, larger Datome, according to Tuel. He would not disclose the machine's cost, but said it sells for 10-15 percent more than conventional rotomolding machines with gas ovens.
The plastics rotomolding division employs 10 at a 20,000-square-foot plant in Fergus Falls, though Katzenmeyer said he expects to hire several new workers once production gears up on the new machine.
For more than 25 years, Shoremaster has manufactured aluminum products for the marine industry, such as boat lifts, docks and piers. Corporate sales are about $12 million.