HOBAS Sheet Molding Compounds
SMC stands for sheet mold compound which refers to a production technology for fittings made of GRP. Basic materials are sheets of preimpregnated glass fiber and continuous glass fiber fleece for a smooth surface structure.
As a first step sheets and fleece are cut into pieces, which are then, layer by layer, folded up to a "sandwich". Then the glass fiber sandwich is put into an oven where it is preheated to increase the flexibility of the material. It can be then easily fitted into the steel mold. For each type of SMC fitting a particular mold has to be designed to give it its distinctive shape. The mold itself is part of a hydraulic press. After the sandwich has been placed into the bottom part of the mold both halves are compressed to form the fitting. Additionally the mold is heated to accelerate the polymerization. During this process step forces range from 30 up to 230 tons and temperatures from 125 up to 195°C. Finally, the pressure is released from the hydraulic press and the finished fitting is taken out of the mold.