Precise multi-component injection molding thanks to valve gate technology

The application example described here is also a two-component application, where plastic and metal components are processed together. In this case, it's a plastic housing for an electronic sensor in an automotive application into which 10 mm long steel fibers have to be integrated. This metal portion creates a Faraday cage which protects the sensor as required. This product required that production be carried out in a clean room where no material residue is released in the production area. For this purpose, it had to be ensured that the metal components did not project from the plastic sheathing at any point. This is why only an extremely reliable hot runner solution with a valve gate – like that offered by Frankenberg, Germany-based company Günther Heisskanaltechnik GmbH – was considered for production. This solution provides an outstanding injection point appearance, and the hot runner system from Günther is able to ensure the cleanliness and efficiency required. The only way to manufacture the product from a standpoint of cost and technology is by using hot runner technology.

The main component of the sensor housing is comprised of a specialized PBT-metal compound with a shot weight of 5.3 grams. The sealing element is injected with a 1.9-gram mixture of thermoplastic polyester elastomers (TPEE) also containing a steel fiber portion. Both materials were specially developed based on customer requirements from leading specialist compounder RTP Company and subjected to preliminary testing for their processing characteristics at the GÜNTHER technical center. To achieve the required process reliability and precision for this application, Günther chose to use hot runner nozzles of type 8NHF80LA-2.0 with a material pipe diameter of 8 mm, an injection point diameter of 2 mm and precise valve gate technology. A double T-manifold is used for each component. The valve gate is operated using individual cylinders of type ENV3/10/L/G here.

Thanks to easy maintenance and short downtimes, the use of valve gate technology saves lots of time and money. Should the needle guide or needle be changed, the mold does not need to be removed. Thanks to the long service life of the needle guides, downtimes are extremely short. On the product side, valve gate technology guarantees high sprue quality over long periods of time, including for filled plastics. Material changes can be easily responded to thanks to straightforward gate adaptation. Unique opening behavior makes sequential injection and cascade injection molding possible.