A thin film of powder is deposited across a plate in a pattern that’s based on a photographic image, rather like the way a copier duplicates an “image” set on its glass. In this case, the images are segments from CAD drawing. Each cross-section becomes a separate image, and these images are rendered not in ink or toner but in powder. Layer by layer, ultimately totaling thousands of layers, the CAD illustration is “printed” in powder created from a plaster-based material until a three-dimensional shape is finished. Once the material is set, the CAD drawing has been rendered as a prototype.
That is a simplified explanation of 3D Printing (3DP), a “paradigm” for producing models. Simplified though it is, it’s a description that makes it easy to understand why that process is having an important effect on metalcasting.
Z Corp. has applied 3DP to develop a line of printers used by design and production engineers to render prototypes of shoes, medical implants, appliance parts, architectural structures, and automotive components.
Applying 3DP to foundry operations came about after a casting pattern and prototype manufacturer recommended using the paradigm to produce metalcasting molds. The result is the ZCast process. It forms molds in a plaster-ceramic composite material that’s suitable for casting prototypes in low-temperature, nonferrous metals (aluminum, magnesium, zinc.) Available to foundries for three years, ZCast offers to “cut casting time from 17 days to three.”
Typically, metalcasting molds are produced from a pattern (or pattern set), which has to be created first. Z Corp. contends that skipping patternmaking can save weeks of production time and considerable development cost. (Specific time and cost savings vary according to the part size and design detail, but the company indicates that two days or less is not uncommon.)
Because Z Corp.’s 3D Printers render all the mold cavities and inserts, ZCast also makes complex casting designs easier to produce. The company states that the process has produced parts that are comparable to sand castings in finish and tolerance. These castings can be machined, too.
Z Corp. applications engineer Howard Rhett reports that ZCast has been well received by the metalcasting market, drawing a steady succession of customers for the large-format printers over the past three years. It’s not for every foundry, he concedes. ZCast is successful at foundries that have experience in modeling, staffs trained in process development, and capital to invest in sophisticated product development.
But, the ZCast process is available to other foundries, too. Z Corp. organized the Metal Casting Partner Program, a network of foundries operating ZCast and companies that need cast metal prototypes. The point is simply to grow the number of companies with access to prototype castings. ZCast operators gain the opportunity to use their capability as a service to the wider industrial market; foundries, designers, and product developers get the prototype castings they need for their own projects.