Gating to the Point
Hot Runner Technology for Micro Parts
Injection molding applications pose specific requirements to the production process if shot weights are extremely low. In the framework of a customer project, Plastechnik AG in Bösingen, Switzerland, worked on a small bearing cage of polypropylene, which is part of a flow measurement device and weighs only 7 mg. Producing their own molds, the plastic processors worked together with Heitec Heisskanaltechnik GmbH in Burgwald, Germany, to master this demanding task. They developed a 4-cavity mass production mold. Even though material throughput is low with only 0.028 g per shot, the hot runner system enables process-secure processing. This is because the system causes no shear and leaves the melt undamaged when transferring the plastic melt into the cavity.
The hot half was completely produced by Heitec. Hot runner nozzles of the First-Line (type: 01.010.13.60) series are employed here, with a shank diameter of 13 mm and a runner diameter of 3 mm. The nozzles’ thermal profile is highly precise, enabling a very small diameter of the gate, i.e. 0.32 mm. As manifold, a so-called nozzle manifold, also named rotary distributor, was used.
The tool was sampled at the site of Arburg, producer of injection molding machines, where it immediately achieved excellent results. All cavities were filled homogeneously at the first shot. This is an excellent result, in particular considering the fact that injection pressure was only 600 bars. The outstanding thermal profile of the nozzles completely eliminates stringing, which is much-feared with the material employed. Provided unit numbers for this article increase as scheduled, the partners have agreed to build a 16-fold mass production mold with identical hot runner components.
Heitec Heisskanaltechnik GmbH
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