Smart Molding International 4-2022

49 www.smart-molding.com sensors Mr. Streili, in your opinion, what are the main challenges in injection molding? I think the main challenge is the complexity of the process itself. There are many parameters that ultimately influence the quality of the finished product: part size, material, the temperature of the environment as well as the temperature of the plastic. Also, molding processes with an inlay, where several materials come together, behave differently than those without. Many injection molders underestimate these influences or know little about how seemingly miniscule changes in the process can affect the quality of their parts. For instance, switching from one material supplier to the next canhave a decisive impact on product quality – even if the composition of the plastic is exactly the same on paper. Which role does measuring cavity pressure play in overcoming these challenges? Cavity pressure plays a crucial role in injection molding. It reflects the complete process in the cavity – and thus provides insights into the conditions under which the component is produced. This makes cavity pressure an indicator of the product quality. Specific quality-relevant properties of the part, such as dimensional accuracy, surface quality, weight and degree of forming, relate directly to the conditions during the different phases of the process. The cavity pressure thus represents a part- specific fingerprint of the product quality and can be used tomake precise statements about optimum process parameters. Also, by measuring cavity pressure, manufacturers can identify scrap parts before they even come out of the mold. What does this quality check look like? The sensors collect measurement data before it is transmitted to a process monitoring system, which evaluates them and visualizes the results in the shape of a curve. For sorting out NOK parts, a so-called evaluation box needs to be defined. If the curve of the cavity pressure goes through this box, the produced part is good; if it does not, the part is defective. It is important to define these boxes correctly. If the evaluation box is too small, there will be pseudo scrap. If it is too big, the product quality will be affected. By identifying problems and increasing efficiency, the service package MoldValidation II helps to optimize existing processes