Water-assisted injection molding (WAIM): model and validation of water penetration behavior

Water-assisted injection molding enables the production of high quality hollow or partially hollow products, with a low process cost as well as a high design and manufacture flexibility. However, principle mechanism behind the building of the residual wall thickness are until now not (fully) understood. Present literature is hence not able to clearly indicate and consequently to explain the influence of a varying process/material parameter on the thickness of the residual wall. In this study, the building of the residual wall thickness during the water-assisted injection molding process was described with the aid of a physical model. The influence of polymer viscosity was thereafter predicted with the aid of the model and linked to the experimental obtained residual wall thickness and in-mold pressure measurements, in order to validate the proposed model. The comparison of the predictions and experiments revealed that the model is able to predict and consequently to explain the influence of a varying parameter on the formation of the residual wall thickness. Moreover, the accompanied insights into the principle mechanism behind the process lead to a more fundamental understanding of the water/polymer behavior during water injection.status: publishe