DUSSELDORF, GERMANY — Wilmington Machinery has developed a novel method of blow molding multilayer industrial parts that replaces an accumulator head with a series of extruders that work together.
The process uses intermittent extrusion using reciprocating screws — one screw for each layer desired, said Kemp Shepard, vice president of marketing for the firm in Wilmington, N.C.
``We're continuing to develop it and we're encouraging companies to come to the lab to evaluate value-added products,'' Shepard said at K'98 in Dusseldorf.
Wilmington distributed information about the process at its small booth in the U.S. pavilion, but it did not display a machine.
Wilmington's initial machine can mold three-layer parts, but Wilmington plans to make machines that can extrude as many as seven layers.
The process works like injection molding: For each screw, as the melt builds up in the barrel, it pushes the screw back. Then all extruders screws push forward at the same time, creating a multilayer parison. Shepard said the machine uses a simple head to form the parison.
The technology can make parts with a barrier layer. It also can add a thin coating — for example, a nylon coating of polyethylene. Shepard said another recent development is a foam inner layer with skins on each side.
Shepard said the machine is part of Wilmington's emphasis on new technology for blow molding industrial products.