| 摘要 |
This invention relates to an improved method of manufacturing a heater nozzle for an injection molding system. The heater nozzle has a helical heating element which is cast into an outer portion around an inner liner through which the melt flows. The outer portion is formed of a conductive material such as a beryllium copper alloy and the inner liner is formed of a durable corrosion resistant material such as stainless steel to provide an excellent combination of these characteristics. The heater nozzle is made by positioning the heating element around a pre-heated solid threaded liner in a mold and pressure casting the beryllium copper outer portion around them. The elongated liner is very accurately located in the mold by having the lower end received in a seat in the mold and the upper end received in an aperture through the plunger as it closes. In another embodiment, the inner liner is provided with a Y-shaped joint by attaching an arm portion to it by brazing them in a vacuum furnace prior to the pressure casting step. After pressure casting, the liner is then drilled to form the melt passage through it and the heater nozzle is machined to remove the projecting ends of the liner and to finish the outside according to predetermined dimensions. This provides a very economical method of making heater nozzles with the necessary combination of characteristics to withstand the operating conditions of a large range of applications. |
