Water Assisted Injection Molding for Single and Multi-branched Tubular Components

Abstract

To produce hollow polymeric parts with complex geometries the Fluid Assisted Injection (FAI) technology is currently used. In this technology water and gas can be employed with or without the aid of a projectile. The process consists in the injection of water at high pressures, after the closing of the mold and polymer injection, and up to the filling of the whole molding zone. The injection of water at high pressures will force the polymer from the core to be expelled to a reservoir. This material expulsion is possible, not only thanks to the high water pressures, but also because the polymer is still in a viscous state, thus facilitating the evacuation. Even though the FAI technology is by direct injection of water/gas or with aid of a projectile, there is a common limitation, which is the inability to produce hollowed parts with forking channels. However, even if creating these branches is possible, there is the impossibility of them being geometrically complex and/or extensive. In these cases, the branches are created with inserts inside the mold, meaning that they will always be limited by a molding insert, and not controlled by the water jet. For cases where it is desired to add complex and/or extensive ramifications, subsequent steps of production and assembling must be added, influencing the overall production time. This work aims, therefore, at studying a new approach for the production of hollow parts with extensive branched channels and complex geometries within a single injection cycle, and thus eliminating subsequent processes that are currently required. The first approach is the application of several water injectors, guided towards the respective branches where hollow sections are intended to be produced. This innovation will have an impact on the serial production of high complexity tubular type parts, reducing the production time with the elimination of subsequent processes. Furthermore, a saving of raw materials is achieved by eliminating the necessity of a creation of additional molds. In this work, a detailed experimental study of the water assisted injection process was done to serve as a knowledge base to the concept of the new process named Multi-Path.H2O.