3D Printing of Sand
Karunakaran, K.P.1, Alain Bernard2, Ranjeet Kumar1, Sajan Kapil1, Yicha Zhang2, Arun Sharma1 and Rakeshkumar, K.3
1 Rapid Manufacturing Laboratory, Indian Institute of technology Bombay, INDIA 2 IRCCyN, Ecole Centrale de Nantes, France 3 Fr. C. Rodrigues Institute of Technology, New Bombay, INDIA
Sand casting is the most common route to produce huge metallic objects. In order to facilitate the extraction of the pattern from the sand mold, they are made in multiple pieces. Due to the draft allowances and the several joints among these pieces and the related misalignments, sand casting is the most inaccurate casting process. 3D printing of the sand mold directly has a disruptive effect as its accuracy approaches that of Investment Casting. The other interesting application of sand 3D printing is building houses, statues etc. Sand is the cheapest material and it can be printed very fast. Therefore, huge molds, as big as 4m, can be 3D printed. Typically 3D printing of sand molds uses a powder-bed approach. Two popular approaches, both using coated sand, are (i) Selective Laser Sintering (SLS) and (ii) multi-jet binder dispensing. Although SLS is the earliest, the latter approach is more popular today. Nozzle clogging is the most common problem in the existing sand 3D printers requiring replacement of the expensive print head almost annually. Layer thickness of <0.3mm limits its applications to only prototype castings. The raw material takes away Lion’s share of the cost (over 90%). Different binder combinations are required for different metals. Under our Government’s “Make in India” drive, IIT Bombay has initiated the development of a sand 3D printer through a Public-Private Partnership (PPP). Our aim is to justify it for large batch production, if not mass production. We propose to use CO2 as the fluid to be printed to completely eliminate nozzle clogging. We wish to build in thick layers (>2mm) supplemented with in-situ multiaxis machining of the layer edges. We shall also invest considerable efforts in bringing down the cost of the binder composition. The safe and economic portability of the fragile sand mold to the foundries at distant places is one more issue to be addressed. This paper will exhaustively review the existing sand 3D printing technologies and describe our ambitious new process.