Arburg GmbH + Co. KG has developed a hydraulic compression molding machine designed for a 0.5-millimeter-thick optical application.
The machine and application were debuted at Chinaplas 2012 in Shanghai. To mold the light-guide panels — a thin optical panel used in tablets and thin-film transistor screens using LED lighting — the mold does not close completely.
“These panels have a flow-path to wall-thickness ratio of 350-to-1,” said Jan Lachhein, group leader for application testing at Lossburg, Germany-based Arburg. “This is why regular injection molding won't work.”
The hydraulic Allrounder 630 S has a clamping force of 250 metric tons and operates with a two-cavity mold. It maintains a 1mm gap until the last 50 milliseconds of the process. The mold, in turn, must be designed so the cavity is sealed, even in the partially open state.
The process helps reduce shrinkage and deformation and can accommodate precise molding specifications.
The light-guide panel features nearly imperceptible ridging and changes in thickness at the edges that are designed to guide LED light.
Most tablet panels are lit from behind, according to Lachhein, but the light-guide panel can be lit from the edges and maintain even brightness across the entire panel surface.
Panel production is about to be rolled out in Taiwan, and a local mold maker that Arburg declined to identify signed a contract for another of the machines during Chinaplas, held April 18-21.
“We have long-term experience in the optical-disc business,” said Lachhein. “At the beginning of 2000 the optical-disc business died, but the experience is relevant.
“This is basically a DVD, but the shape is different.”
At Chinaplas, Arburg also introduced its new Edrive Allrounder for the first time in Asia.
The company also showcased its Allrounder 570 H as a representative of the Hidrive hybrid high-performance series. The Hidrive machine was equipped with a special packaging unit, operating with a four-cavity mold from Glaroform AG of Näfels, Switzerland, and produced polystyrene cups in a cycle time of three seconds.
The use of transparent polystyrene and a film printed on both sides gave the cups a decorative surface on both the inside and outside.
