Improving heat transfer and compressed air consumption in low pressure die casting of aluminum wheels

Abstract

Automotive wheels made from aluminum alloys are generally manufactured using the Low-Pressure Die Casting (LPDC) method. The molten aluminum is pressurized and filled into the cavities between the molds, and it is cooled using cooling channels in the LPDC. While the cooling fluid can be either air or water in industrial applications, only air cooling is utilized within the scope of this study. The primary expenditures of the process are attributed to the cycle time and the consumption of compressed air. In industrial settings, the primary coolant supply, emanating from either one or two inlet sources, is systematically channeled through a series of nozzles. These nozzles are strategically designed to impinge air onto specific areas of the mold pockets, ensuring efficient cooling.This research focuses on enhancing the cooling channels and mold pocket regions in LPDC through a combination of experiments and Computational Fluid Dynamics (CFD) integrated with Conjugate Heat Transfer (CHT) analyses. The study involves designing cooling channels to achieve a uniform mass flow distribution at the nozzle outlets, and optimizing the mold pocket regions. This optimization resulted in a 46% reduction in compressed air flow while maintaining comparable levels of heat transfer in the optimized mold pocket design. Moreover, flow rate non-uniformity at nozzle outlets was reduced from 11.5% to 2.0% to achieve uniform cooling and temperature distribution across the wheel spokes. An experimental setup with a cooling pipe network allowed simultaneous flow rate measurements from 20 outlets using flow rate sensors.The improved cooling channel and mold pocket design were adapted to the LPDC, and 20 aluminum alloy wheels were successfully cast with a 46% lower mass flow rate. All these wheels were tested in accordance with the relevant test specifications and the results obtained were assessed as compliant according to certain limits.