By: Bill Bregar
May 15, 2014
LAS VEGAS — An IKV official from Germany said using lasers to heat specific areas of an injection mold quickly can produce better parts, especially those with optical properties or high gloss, and micromolded parts and thin parts with long flow lines.
Maximilian Schöngart is head of the department of part design and materials technology at IKV, the Institute for Plastics Processing in Aachen, Germany. He presented IKV’s research findings during an Antec presentation April 28.
He said the constant cold mold temperature used in injection molding, to cool down the molten plastic in the mold, is not good enough for some demanding parts because the melt solidifies on the outer part of the melt flow. That can make it hard to fill out a part.
Rapid, or pulsed, heating and cooling of a mold is already done by induction, using water, oil, steam and cartridge or ceramic heaters. RocTool and Single are two well-known brands.
Lasers use the same principle, but operate by heat radiation, Schöngart told his Antec audience. He calls it Vario Thermal temperature control.
Lasers can be installed into the mold cavity, but this requires a specially designed mold. It is possible to use a mold, with no modifications required, if you use an external robot to apply the laser radiation, according to Schöngart. The robot directs a diode laser and a high-speed laser scanner to target heat to the mold. At IKV in Aachen, the used a KraussMaffei press with a Wittmann robot to direct the laser device into the open mold.
Schöngart said high-strength lasers require special protection around the press, such as metal sheets and large protective windows.
The research in Germany showed that the rapid-cycling heating and cooling of a mold can turn out a polycarbonate part with no weld lines, in the area where flow paths come together. It also cuts cycle time.