Evaluating Purgeability in Additive and Conventional Manifold Systems: An Experimental and Numerical Approach

In the injection molding process, manifold systems are essential for distributing the melt from the injection unit to the cavities of the mold. The increasing use of additive manufacturing enables the production of complex systems with optimized geometries that would be challenging or impossible to manufacture conventionally. These novel geometries not only promise improved flow distribution, but also more efficient purging during color and material changes, which is essential for minimizing waste and reducing energy consumption. The efficiency of these purging processes depends on various factors, including the geometry of the distribution system, the flow velocity and the rheological properties of the materials used. A number of simulative and experimental evaluation criteria are available to quantify the purgeability. In this paper, the purgeability of two additively manufactured manifold systems and a conventionally manufactured manifold system was analyzed both experimentally and numerically. For this purpose, experimental color change tests were first carried out and evaluated at six different operating points. These operating points were then transferred to the ANSYS Fluent simulation environment, and the results were compared with the experimental data. The results indicate that lower temperatures lead to faster purging for all geometries. However, the experimental data show no significant advantage, as the influence of the conventionally manufactured nozzles masks the potential benefits of the additively manufactured manifold systems – despite the latter demonstrating a clear purging advantage in the simulations.