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Rapid tooling from protoypes: the cool-spray mold-making method

We propose in the paper a process, based on the use of a high velocity, electric arc metal spray thoroughly atomized on a master model in order to make a shell. The mold is realized by placing the sprayed alloy into a frame and reinforcing it with appropriate material. The first part of the paper presents briefly the main rapid prototyping and tooling techniques used in industry. We then describe the tool/moldmaking method which is a process to reproduce shapes very accurately. Given any model, a metal shell can be build up around it to desired thickness. We describe and comment the tasks leading to the shell making. The realization of the mold itself is also presented. In most cases, the spray alloy shell must be reinforced with backup. We expose the application fields of this new technique especially in term of product and process validation. We focus on the natural links with stereolithography. By comparison with conventional processes, we show how fabrication time and costs are dramatically reduced by integration of this new moldmaking method. Finally, we present the limits of the technique and the perspective of work and further research.