innovations CASTING
Professor, Students Pursuing Rapid Casting Technique
something new and different. Such is the case of Sam Ramrattan and two graduate students at Western Michi- gan Univ., Kalamazoo, Mich. In 2005, the engineering professor in WMU’s College of Engineering and Applied Sciences began researching ways to use existing technology in metalcasting facilities to reduce tooling costs. One development involved cur- ing shell sand with an infrared light source and machining it with a three- axis CNC machine. Te graphitic sand could be used for molds while not being deleterious to the tooling equipment. “I realized this has greater implica- tions than just for foundry pattern shops,” Ramrattan said. “Tis could be a rapid casting technology. We were meeting and exceed- ing traditional build speeds that 3-D printing would allow. [3-D printers] can cure thousandths of an inch at one time and a mold can take 48 hours. Our cure layers are a little larger than a quarter of an inch, about 8 mm, and we can produce molds in a few hours. We have an advantage in throughput.”
B
Te molds begin as digital model that’s sectioned into layers so a CNC code can be produced for each layer. Sand is cured in a working envelope of a three-axis CNC mill, and the part cavity for that layer is machined. Te com-
y definition, innovation is not the destination of a linear path. What be- gins as an exploration of one concept veers toward
machines the cavity. Tis continues un- til the mold is built layer by layer. Te uncured sand is removed, and metal is cast into the mold. Te total time from digital model to final casting can be less than six hours. While early results are encour-
Ramrattan continues to work on the process with help from two WMU graduate assistants.
pleted layer then is filled with uncured sand to preserve the cavity. A new layer of coated sand is placed in the appara- tus and cured, and the CNC mill again
aging, the process faces significant challenges before it can be consid- ered a commercially viable method of producing castings. Surface finish must be improved, and Ramrattan’s team is still searching for proper sand coatings. Hemant Bohra and Mi- chael Konkel, two WMU graduate students, are investigating coatings, as well as machining and automation improvements. “By no means is the process
commercially ready, but the proof of concept is in place,” Ramrattan said. “If we can improve the surface finish and get the right types of coatings, I believe it will be something viable.” ■
The rapid prototyping technique involves curing sand with infrared light (top left) and machining each layer (bottom left) to produce the final casting (right).
Mar/Apr 2014 | METAL CASTING DESIGN & PURCHASING | 49
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