Conversion of rapid prototyping models into metallic tools by ceramic moulding - an indirect rapid tooling process

INEGI developed a process to convert models made by rapid prototyping or conventional techniques into metallic moulds. The main purpose is to rapidly obtain prototype tools by casting a metal into a ceramic mould produced by mixing in variable proportions, ceramic particles, a liquid binder and a catalyst added to start a sol-gel reaction. This liquid slurry is poured into the box containing the mould to be reproduced. After a short period of time the ceramic mixture acquires a rubber consistency. The pattern is removed from the ceramic mould, which is fired and sintered in order to generate an inert mould with the desired strength in which most alloys can be cast. The effect of ceramic materials (shape, granulometric distribution, chemical composition), sintering conditions (time and temperature) and casting conditions (mould preheating temperature and pouring temperature) were studied in order to obtain ceramic moulds and, subsequently, metallic moulds with tailored properties (accuracy reproduction of details, low roughness and high mechanical strength).