Ceramic Seals for Hot Runner Nozzles
In cooperation with the companies Graveurbetrieb Leonhardt and OxiMaTec GmbH, Mold-Masters Europa GmbH has developed the first hot runner nozzle with a gate seal made of high-strength, thermally insulating high-performance ceramic. Gate seals provide the connection between the hot runner nozzle and the steel mould. Plastic is injected into the mould through this seal and solidifies there in its final shape. Injection moulding with a hot runner system is a very challenging process that can now be better controlled with the new ceramic gate seal.
The ceramic mixture is based on zirconium dioxide and, compared to conventional ceramics, is characterized by its very high toughness and strength. At the same time, however, the new seals are designed to withstand high compressive loads. The immediate separation of the hot zone from the cold zone represents a considerable benefit. Heat transfer from the hot runner to the mould is reduced, so that the hot runner system needs less energy for heating. Since the hot runner system transfers less heat to the mould, the cooling time and thus the cycle time are shortened accordingly. This improves the economics and increases the productivity of the injection moulding process.
The ceramic material has been tailored specifically to the requirements of hot runner system technology. The complex manufacturing method permits production of components with a demanding geometry such as that found in a hot runner system. These initial components provide the foundation for further developments with regard to production of plastic products. For instance, the ceramic gate seals permit low-wear processing of highly abrasive materials. It may also be possible in the future to replace additional components in the hot runner system with this ceramic.