THE REPRAP 3D PRINTERS FOR METAL CASTING PATTERNMAKING – CAPABILITIES AND APPLICATION E. M. Minev, E.Yankov, R.M. Minev Ruse University (RU)“А.Kanchev”, 1. Intrduction The focus of this research is the implementation of the economical solutions such as RepRap 3D printers to bring the investment casting technology closer to the perception of ‘reverse engineering’ and converting the modern foundry to a typical lean and agile production system. The developed technology is an integrated chain of: (i) CAD / CAM design; (ii) Multi-layer construction of foundry patterns; (iii) Precision vacuum investment casting in ceramic block forms. The process allows for rapid preparation of ‘conceptual’ and ‘functional’ metal prototypes using a variety of high strength, corrosion-resistant, anti-friction, and other special alloys based on Al, Cu, Fe, Co, Ni, Ti. The vacuum casting induction melting equipment (Leybold, MCP, Schultheiss) (Fig.1) has been used to construct the process chain. It enables complex alloying of the materials, flexibility and repeatability of the results. The technology could be widely applied in the following areas: (i) production of single and small-batch castings; (ii) conceptual development and testing of new products and machinery; (iii) production of spare parts and specific hollow, prismatic thin- walled castings; (iv) repair, improvement and adaptation of differnt equipment; (v) artistic casting; (vi) medical implants and dentures. (a) (b) Fig.1 Scheme (a) of a machine for precision casting in block forms with the combined use of differential pressure (a) - MCP and centrifugal forces (b) - Schultheiss. The main advantages of the technology of vacuum precision casting in block form [1-3] in combination with 3D CAD design and build of sacrificial models by layering 3D printing are: (i) the possibility to cast molds with complex shapes; (ii) shortening the production cycle (total time to receive ready product down to 3 days); (iii) obtaining quality castings with reduced porosity and improved mechanical performance; (iv) high precision and dimensional stability of products; (v) usage of variety of casting alloys. The technological processes are integrated with a computerized system for laser scanning and obtaining digital 3D profiles. The professional process chain would include higher grade RP machines for producing sacrificial patterns and specialised software but the current research project demonstrated that at this stage of the technology development sustainable results could be achieved using RepRap 3D budget printers and free range software. 2. Methods for production of casting patterns using the RP (Rapid Prototyping) techniques A study [4] performed in 1999 identified about forty technological approaches to RP. Only some of them have reached maturity and are used for production of sacrificial or permanent foundry patterns (Table 1). The most matured Rapid Prototyping (RP) technologies are based on the