Tailor-made hot runner solutions for planar components

At Fakuma 2018 HRSflow demonstrated the synergies generated from the combination of its universal hot runner systems and its expertise in the CAE simulation of injection molding processes. The complex, high-quality examples range from a sizeable, thin-walled suitcase shell and a collapsible two-material bath box to a laptop cover with a top-class surface; the latter produced using HRSflow’s FLEXflow technology of electric servo-driven valve gate systems.

Large, thin-walled, deformation-resistant suitcase shell

Despite its low mean wall thickness of only 1.8 mm, the shell for a lightweight 1.9 kg suitcase made of polypropylene has particularly high structural performance. The manufacturer traditionally fills the cavity for the approx. 490 mm x 290 mm x 690 mm parts via a single injection gate with a diameter of 5 mm positioned centrally on the outer surface. HRSflow performed extensive computer simulations of the flow behavior and the pressure conditions arising during the process. The solution is a customized axial single-nozzle solution, in which a hydraulically operated hot runner needle valve nozzle serves as an extension of the machine nozzle. Despite the long flow paths, this design ensures – unlike the original configuration – warp-free parts with high class surfaces, free of flow lines or visible weld lines. A brand emblem is clipped on to cover the gating point. Furthermore, the HRSflow nozzle enables, thanks to an optimized internal geometry with minimized dead spots, a fast color change between the 15 available shell colors.

Collapsible Box in 2 K-Technology

A collapsible box measuring 660 mm x 240 mm x 300 mm, used for bathing babies or small children, has been designed so that it can be folded away to save space. Made by two-component injection molding, the manufacturer combines a polypropylene (for the 2.5 mm thick side parts) with a thermoplastic elastomer that joins the PP parts flexibly to one another. To fill the cavities for the wall elements, use is made of a 10-drop hot runner system from HRSflow with valve gate nozzles of the Ma series, which are designed for medium shot weights. A cascade control system ensures that all the differently sized parts are perfectly filled at the same time. The second operation comprises the injection of the flexible component into the long but tight cavities for the hinges. This is done using a 4-drop hot runner system with valve gate nozzles of the Pa series, which are designed for lower shot weights.

In the project phase, HRSflow optimized all the functions with the help of extensive CAE flow simulations. This has resulted in evenly filled 2K parts without visible weld lines or entrapped air. The flexible components continue to connect the wall elements reliably for a long period of time and even after a large number of folding processes. In production, the system allows fast color changes to be completed within just a few cycles.