Direct metal rapid casting: mechanical optimization and tolerance calculation

Purpose - The purpose of this paper is to optimize the mechanical performances of parts produced by the ZCast Direct Metal Casting process varying the thermal treatment parameters. Adopting the optimized settings, a specific dimensional evaluation is planned to calculate the international tolerance (IT) grade ensured by the process. Design/methodology/approach - Cylindrical ZCast samples are manufactured and heat treated varying time and temperature. The baked parts underwent compression tests and the rupture surfaces are observed using the scanning electron microscopy. A regression analysis is performed on the results to optimize the baking process. For the dimensional assessment, a specific benchmark is designed, built and treated. It is measured before and after baking using a coordinate measuring machine and the results are processed to obtain the IT grade. Findings - The results proved that in the heat treatment of ZCast parts time has a negligible effect on the compressive strength, whereas temperature can be optimized for best mechanical response. The IT grade is calculated for green and baked parts; separately in all three directions in space. Tolerance is proved to be fundamentally the same in every direction and independent on the heat treatment. The considered rapid casting process can be classified in IT15 grade. Originality/value - The paper suggests an original approach to improve knowledge of the ZCast process. The study of the building phenomena is combined with macroscopic measurements to develop a solid understanding of the expected performances, which is fundamental in order to support the industrial application of the technology.