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 Rapid prototyping using ice as a build material at first blush seems unlikely to be practical. It requires parts to be built in a low temperature chamber, and once completed, they must be maintained at those low temperatures or they'll melt. Upon reflection, however, these disadvantages may be offset by some interesting possibilities.
Dr. Ming C. Leu and his group at the University of Missouri-Rolla have built an experimental Rapid Freeze Prototyping (RFP) demonstration system. According to Dr. Leu, the system is fast, inexpensive and environmentally friendly compared to many RP methods. The mechanical design is quite simple. The machine uses technology similar to some inkjet-based RP systems. It uses a drop on demand nozzle driven by an X-Y stage to create outlines for each layer, and a continuously-jetting nozzle to quickly fill them in. This architecture provides fast operation like a wide area inkjet machine, but keeps the number of parts and their complexity to a minimum for low system cost. While there is a need for close control of temperatures at the jetting tips so that the water freezes quickly after it's deposited, temperature is a quantity that is relatively easy to measure and lends itself to straightforward control. The design of a low-temperature chamber doesn't necessarily add a lot of cost either. The technology used in supermarket frozen-food display cases can be utilized.  
This panel, left photo: A closeup of an ice vase; right: an investment cast part made from an ice pattern. Obviously, since the build material is frozen water there are no flames or chemical disposal or exposure problems. The water can also be colored with food-coloring or other materials. And, - as has been far too often pointed out by now - the water can also be flavored to create custom-manufactured Popsicles other ice cream novelties, as well.There is one surprising additional feature of using water that is not well known, however. The surface quality of ice parts is excellent. Dr. Leu says the finish is similar to the best examples from inkjet-based RP technology. The high surface tension of water is an important contributing factor.
 
The test system is not designed for high accuracy, but Dr. Leu says resolution is in the range of 0.004 to 0.006 inches. He feels that the first applications of the equipment will be for investment casting, an application where good surface quality is important. As one example, there is ongoing work by his group to use the equipment for the fabrication of dental prosthetics.For more info contact:
Dr. Ming C. Leu,
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