Steel and Aluminum Molds: The Effect of Thickness on Productivity and Part Quality

The use of aluminum to manufacture injection molds aims to maximize the productivity of plastic parts, as its alloys present higher heat conductivity than tool steel alloys. However, it is essential to accurately control the injection molding parameters to assure that the design tolerances are achieved in the final molded plastic part. The purpose of this research is to evaluate the use of aluminum alloys in high-volume production processes. It delves into the correlation between the type of material used for mold production (steel or aluminum) and the thickness of the injected part, and how these variables affect the efficiency of the process in terms of the quantity and quality of the produced parts. The findings suggest that replacing steel molds with aluminum alloys significantly reduces injection molding cycle time, the difference ranging from 57.1% to 72.5%. Additionally, the dimensional accuracy and less distortion provided by aluminum have improved product quality. In case of thinner geometries, the results indicated that higher pressures were needed to completely fill the cavity. In addition, an increase in the warping of the parts was observed due to the solidification of the flow front, resulting in more pronounced pressure gradients along the part. Therefore, due to their lower stiffness and high thermal conductivity, aluminum molds would not be recommended for this type of geometry in high-production processes. For the cases associated with lower pressures (greater thicknesses), aluminum molds showed better dimensional quality compared to steel. This result indicates that these tools could be an interesting alternative for manufacturing large volumes of parts in aluminum molds.