Powder separation strategies for recycling in multi-material additive manufacturing

Multi-material Additive Manufacturing technologies that process a number of different powder materials in one build are slowly gaining market relevance. One reason these novel technologies' potential is not yet being fully exploited is the complex powder recycling of materials with similar physical properties and particle sizes below 200 microns. In Multi-material Laser Beam Melting (MMLBM) the powder bed is a mixture composed of all processed materials, which need to be separated during the recycling process. This paper proposes suitable powder separation principles for materials commonly used in MMLBM. Furthermore, evaluation criteria are elaborated to rank technologies and distinguish the most relevant ones in terms of separation accuracy, practicability and cost effectiveness. Performance of selected separation strategies is analysed experimentally. As a result, flotation techniques, heavy media separation, principles based on particle inertia, magnetic separation and dry sieving appear to be most promising and are thus suggested for further research.