Better joining of metal to plastic

Rimless spectacles will benefit from a new joining process, which uses lasers to form a better bond between the metal arm and plastic lens. Liftec, a new process developed by researchers at the Fraunhofer Institute for Laser Technology ILT in Aachen, is unveiled this week at the Productronica show in Germany. A laser heats the end of the metal pin that attaches the arm to the lens. The beam penetrates the transparent plastic lens without damaging it, and heats the metal pin to a temperature above the melting point of the plastic. “The heat radiated by the pin melts the surrounding material, and mechanical pressure is applied to push the metal part into the plastic,” says ILT engineer Jens Holtkamp. “As the joint cools, a positive bond is formed between the two parts.”