A study on replication and quality correlation of on-part and on-runner polymer injection molded micro features

Injection molding is increasingly gaining place in manufacturing of polymer components as is can ensure a cost efficient production with short cycle times. To ensure the quality of the produced parts and the stability of the process it is essential to perform frequent metrological inspections. In contrast to injection molding’s short cycle time, a metrological quality control can require a significant amount of time. The late detection of the problem can result to high losses and scrap rate. This paper presents an alternative approach to process monitoring and part quality control with fast off/in-line metrology of physical part quality indicators (“Product Fingerprint”). The proposed approach is based on the concept of metrology applied to dedicated micro features, positioned on the runners, similar or equal to those in the part in order to access the quality of the produced plastic parts. A designed experiment was employed to map the experimental space and quantify the pillars replication depending on position and processing parameter combinations. The pillars were assessed and the main effects of the processing parameters, were calculated to reveal that the effects of process parameter change were similar in all measurement positions. Results showed that the product fingerprints have a correlation to the quality of on-part micro features. The concept can support the creation of a fast part quality monitoring system that has the potential to decrease the use of off-line time-consuming detailed metrology for part approval.