Abstract
Sand casting is one of the oldest and most versatile processes used in foundries. However, traditional sand casting is expensive and time-consuming. Rapid sand casting, one of the additive manufacturing (AM) technologies that can be used by the local foundry industry for sand casting, has been shown to be cheaper and faster than traditional sand casting. However, this technology has not been adopted by the local foundry industry in South Africa due to the high cost of AM printers, the high cost of the imported silica sand and binder recommended by the 3D printer manufacturers, the unknown manufacturability of the sand moulds and the unknown returns.
The objective of this study was to investigate if the adoption of rapid sand casting has technical and financial benefits. The sand mould for the impeller of a centrifugal pump was chosen for the study because of its wide range of applications in many industries, and also its complexity, which result in long lead times to produce high quality moulds in traditional sand casting. The literature has shown that AM is one of the processes that can be applied to ensure high quality impeller sand moulds with high resolution and high dimensional accuracy. Due to local availability, the Voxeljet VX1000 printer that uses binder jetting was used.
The financial feasibility and profitability was evaluated using the payback period (PP) and discounted cash flows (DCF), which were implemented at the net present value (NPV) and the internal rate of return (IRR). The payback period was found to be 3.33 years for annuity cash flows and 3.15 years for mixed stream cash flows. The net present value was found to be R5 352 227.94, while the internal rate of return was 11.14%. A sensitivity analysis showed that by using local cheaper local silica sand instead of imported silica sand, the NPV could be increased to R16 416 119.76 and the IRR to 31.21%.
This study has shown that rapid sand casting can be assessed through a combination of casting simulation and financial analysis. The results indicate that there is strong evidence that binder jetting is both technically and financially feasible.