In-mold sensor concept to calculate process-specific rheological properties

To gain extended knowledge on the flow behavior of polymer melts during filling phase of the injection molding process, an injection mold featuring complex sensor technology was developed. Three triple-combined FOS MTPS408 cavity sensors (FOS Messtechnik GmbH) are aligned along the flow path of a plate-shaped cavity. Each sensor features an infrared detector, a type K thermocouple, and a piezo-electric pressure detector. This configuration enables the local and transient recording of melt temperature, mold temperature and cavity pressure near gate, part center and end of part simultaneously. Averaged melt velocities are determined by evaluating the differing times of the rising edges of the infrared sensors. Local melt velocities and viscosities are calculated at each sensor position by evaluation of the gradients of temperature and pressure. Moreover, the used injection mold is equipped with RHCM technologies to additionally influence the mold surface temperature and hence the filling of the cavity. The specimens are plate-shaped parts having cut-outs and ribs similar to geometries found in numerous industrial applications such as cover panels. The application of this in-mold sensor concept provides novel possibilities for the systematic in-line analysis and evaluation of process-parameters in injection molding. Further studies will be carried out to connect the process-specific properties to the specimen morphology; aiming at controlling morphology by adjusting process parameters.