Valve gate cascade molding simulation integrated into Moldflow

Italian hot runner specialist HRSflow (San Polo di Piave) has developed a solution in collaboration with Autodesk (San Rafael, CA) to simulate the gradual opening and closing of its FLEXflow valve gate nozzles with Autodesk Moldflow, thus predicting pressure reduction and the associated clamping force reduction.

In addition, users will now be able to determine opening strokes (valve positions), opening and closing times, and opening and closing speeds of FLEXflow valve gate nozzles based on Moldflow filling analysis. The data can subsequently be employed as initial basic settings for the HRSflow control unit, which reportedly significantly facilitates first part validation. The new function will be available for Moldflow users starting from spring 2015.

The FLEXflow valve gate system, equipped with a servomotor, is said to be particularly suitable for the manufacturing of large-scale components with class A surfaces, for which cascade injection molding is frequently used. At the same time, the electrically-driven actuation cylinders of the valve gate nozzles allow for gradual, precisely-controlled and individual opening and closing of valve pins with pre-selected speeds. This allows for precise control of melt flow and volume flow into the cavity. The result is reportedly a filling process that is optimized in every respect, during which, due to the gradual opening and closing of the valves, the dreaded pressure loss in cascade injection molding and the associated pressure drop marks can be avoided.

For the new Moldflow function, HRSflow and Autodesk tested a slow and purposefully graded mold filling process in cascade injection molding on a close-to-production test tool for a real spoiler. The tool is equipped with a seven-drop hot runner system and additional pressure sensors. Throughout the test, the data gathered with the Moldflow analysis was verified.

Through this process, proof was obtained that, when using the FLEXflow system, the packing pressure is much more homogeneous and lower than in conventional cascade injection molding technology. This, in turn, positively affects component quality since molded parts exhibit much lower stress and thus a substantially reduced tendency to warp. Moreover, the tests showed up to 20% lower clamping force requirement.

In the future, with the new Moldflow function, Autodesk Moldflow users will be able to assess the influence of FLEXflow systems on the injection molding process, as well as component quality, during the development stage. Furthermore, the new Moldflow function supports current FLEXflow users to optimize their basic settings and when deciding on the required clamping force requirements. Another advantage reportedly lies in the opportunity to specifically take into consideration FLEXflow hot runner systems during feasibility studies.