A very cool idea

Since the mid-1980s, RP technologies have been helping product designers develop products more quickly, with Polymers, metals, wax, paper, wood and sand all forming the basis of one system or another.

But, argues Dr Ming Leu from the University’s engineering department, most systems are still too costly, and many of them generate dust or emit smoke, posing health risks.

Driven by the goal of creating an environmentally benign rapid prototyping process that uses cheap and clean materials and works as well as existing technologies, Dr Leu has developed a method that uses ice rather than plastics to create models. He calls his system ‘Rapid Freeze Prototyping’ (RFP).

Rapid Freeze Prototyping has the potential, says Leu, to be faster, cleaner, and, because of the availability of water, less expensive than traditional rapid prototyping systems.

RFP works in a similar fashion to other RP techniques. Leu has built a system that can make three-dimensional ice parts of arbitrary geometry, layer-by-layer, by freezing droplets of water that are deposited from a nozzle onto a surface. In order to keep the fabricated part intact, the whole process occurs within a freezing chamber.

Leu and his team are currently using the system with modelling and analysis methods to understand the behaviour of material solidification and fluid spreading during the ice part building process.

Also, rather than creating the prototype layer by layer, Leu’s system first creates a frozen ‘shell’ of ice which is then filled with water, an approach that further reduces the time involved.

While the system is still at an experimental stage, Leu believes it offers manufacturers a variety of advantages over other systems. Aside from its speed and lower operating costs, the system would also make it easier for manufacturers to build transparent parts, as well as colour parts (just add food colouring to the water stream).

One promising application of the RFP technology is investment casting. The Massachusetts based Duramax company recently developed the Freeze Cast Process (FCP), a technology of investment casting with ice patterns made by molding. The company has demonstrated several advantages of this process over the competing wax investment and other casting processes, including low cost (35-65% reduction), high quality, fine surface finish, no shell cracking, easy process operation, and faster run cycles. Additionally, there is no smoke and smells in investment casting with ice patterns