Development of a quality assurance framework for chemical coated sand used in Additive Manufacturing technologies

Abstract

The importance of South Africa's foundry industry cannot be overemphasized as it contributes towards the economic development of the country. It has been reported that the local foundry industry has been under severe pressure in previous years owing to very low economic growth, drought and continuing import leakage. The Vaal University of Technology positioned itself to provide cutting edge services to the foundry industry that are aimed to assist local foundries to become more competitive on a global scale. The services offered include casting simulation and printing of moulds and cores. The moulds and cores are printed with a Voxeljet VX1000 machine that uses a binder jetting process. The local manufacturing of moulds and cores for the foundry industry, using binder jetting additive manufacturing technology, is still considered to be expensive. The high manufacturing cost can be directly linked to expensive printing material, supplied by the OEM. A possible solution to mitigate the printing cost could be to localise the chemical coated sand used in the Voxeljet 3D printing process. However, this poses a risk to the quality of the printed components, as no quality assurance measures, for chemical coated sand, are available. Due to this reason, a quality assurance framework for the chemical coating process had to be examined. This study investigated the evolution and meaning of "quality" and defined quality assurance as processes, procedures and work instructions, which are used to ensure a repeatable product or service that adheres to a desired quality standard. The quality by design methodology was identified as a suitable methodology to aid with the development of the quality assurance framework that could be used to ensure the quality of the chemical coated sand. The methodology consisted of 8 sequential steps that were used to determine the quality target product profile, critical quality attributes, process flow diagram, critical process parameters and material attributes, quality risk assessment, design space, control strategy and continuous improvement strategy of the chemical coating process. These components serve as the QA framework that could be used as a basic structure or guideline for the development of processes, procedures or work instructions.