Hot runners refine metal and ceramic injection moulding
Having a large gate point plays an important role
With the MIM technology, the parts are often gated directly, and not via a sub runner. Nevertheless, a relatively large gating point must be used in this case to obtain the necessary throughput and to transfer sufficient heat into the gate point. This is necessary because the metal-filled material transfers some of the heat into the cavity, and the melt freezes quickly due to the high filler content. However, with the CIM technology, a sub-runner is often used. Here, too, a large gate point is of importance in order to cause as little shear stress as possible and to transfer the molten material as quickly as possible into the cavity.
With regard to wear resistance, the hot runner technology used has to meet severe requirements for both MIM and CIM. In products from Günther, nozzle tips made of hard alloys have been shown to provide the best possible wear protection. For this reason, long lifetimes are possible without needing to change some components of the nozzle.
A further quality increase can be achieved with the company's hot runner nozzles and manifolds, which are heated by a fluid. It is well known that particularly for the processing of CIM-feedstock, a very homogeneous control of temperature is necessary to avoid segregation and inhomogeneities of the molten material. This could cause the formation of voids in the component. Because of the inertia of the fluid, a nozzle heated by a liquid even provides more constant temperature behaviour than an electrically heated hot runner nozzle.