Use of Injection Molding Simulation to Assess Critical Dimensions and Assign Tolerances

Abstract

Abstract When a product is certified for production and while its quality is being monitored, it is not economically feasible to watch every dimension of the part. Through the definition of critical dimensions, the amount of measurements necessary for quality control can be limited. However, in order to properly assign tolerances to the critical dimensions, the engineer needs to understand the capability of the process. Unfortunately, the subject of tolerances can be a great source of arguments between design and manufacturing engineers. Concurrent engineering has taken a holistic approach to the problem by forcing manufacturing engineers to get involved earlier in the development process. We propose a methodology that employs injection molding process simulation to track the development of critical dimensions from the design stage to production. This methodology provides a more quantitative approach to the tolerancing of injection molded parts. Furthermore, the application of this methodology will promote better communication between manufacturing and design engineers by giving them a common language, consisting of a software model and data. By gaining an understanding of process variation, the design and manufacturing team will be able to do four things: assess the process capability, determine if the part will function properly through tolerance analysis, assign critical dimensions, and set up a measurement scheme for quality control.