'Expansion molding': New method for LSR micro-molding

Engel has expanded the scope of X-melt technology to include low pressure micro-molding using liquid silicone rubber (LSR). X-melt is expansion molding, which relies on the inherent compressibility of plastic melts and uncured LSR. The procedure is to first accumulate the shot volume in front of the screw and then move the injection screw to its final forward injection position while the material is held in place by cold-runner valve-gate nozzles. The LSR is compressed using this pre-injection stage to create a spring or stored energy. The amount of energy is determined by the X-melt pressure, with the set pre-injection pressure and the size of the cushion or spring in the injection unit. LSR is 5% to 7% compressible in comparison with other liquids that are not compressible, depending upon the material durometer and supplier. LSR is held in this compressed state for a set time in the X-melt process to allow the LSR material pressures in the injection unit and cold runner to stabilize.