A COMPARISON BETWEEN VERTICAL AND HORIZONTAL PLASTIC INJECTION MOLDING MACHINES FOR PROTOTYPE TOOLING APPLICATION

During the product development process, functional prototypes are usually required to perform mechanical and/or functional tests. For plastic injected parts these prototypes can be obtained using a prototype tooling, i.e. a mold for a reduced number of injections. They are usually manufactured of cheaper materials and in a shorter time when compared to production molds. Because the injection of prototypes is usually made using a horizontal injection molding machines, the inserts have to be assembled into a traditional mold base, which increases time and cost to obtain the prototypes. An option that could be used to further reduce costs and time to obtain such prototypes is the use of vertical injection molding machines, which usually requires simpler clamping systems. So far, it was not found in the literature any study in this area. This study aims to conduct a comparison between the injection process in these types of injection molding machines (horizontal and vertical). The idea was to analyze not only the process but also the quality of the moldings. Mold inserts for tensile and bending tests specimens (according to ASTM) were designed and manufactured in SAE 1045 steel using CAD/CAM and CNC machining, for these two machines. The pair of inserts for the horizontal injection machine was mounted in a mold base, while the pair of inserts for the vertical one was mounted directly on the machine (without a mold base). For the latter, C-clamps were used to keep the insert closed during the injection process. Polypropylene was the polymer injected. The time to manufacture the inserts and to inject the parts was compared and tensile and bending tests were performed. The results shown that the moldings have similar mechanical characteristics and that the prototype mold for the vertical machine was ready to produce in a shorter time. The study concluded that vertical injection molding machines can be considered a good alternative to obtain injected functional prototypes using prototype tooling.