Product
Spotlight Foam Patterns vs Printed Patterns by Mike Horan, Legacy Foam A
s the investment casting industry evolves and moves toward more complex castings with reduced lead times the pattern making process must change too.
Foam patterns offer an exceptional way of supporting
those difficult castings that has not been previously experi- enced in patterns. A foam pattern will provide a quick turn- around and a solid pattern ready for shelling. While a printed pattern can offer complex shapes many draw backs still exist. The initial purchase price for a printing machine is very high in addition to maintenance and personnel to operate those machines. Lengthy build times are also part of the equation for printed patterns. Printing requires time consuming bench work no matter the size of the pattern. If the end pattern is larger than the frame of the printing machine, multiple pieces are required with more bench work including finishing and bonding of the individual pieces. Bonding the printed piec- es also introduces a joint which can lead to broken patterns during shipment to the foundry or failures during the shelling process. From a time perspective, printed patterns can take several
days to grow, cure, bench and join multiple pieces before the pattern is ready for shelling. Foam patterns can effortlessly address and eliminate each of these issues. A foam pattern is made from aluminum tools [existing wax tools can be used] and are produced as a single large pattern. The de-molded foam pattern will be ready for handling and does not require any bench work for preparation of the slurry application. Foam patterns can be injected and de-molded within a few minutes as compared to several days for a printed pattern. The foam is strong enough to ship cross country and will be able to withstand the shelling process. A complete, large, complex one piece foam pattern is an excel- lent choice for difficult castings that have unique features, a foam pattern will provide better processing success and re- duced lead times. As a wax to foam comparison, foam patterns continue to
provide excellent benefits while wax will struggle to produce a complex pattern. Wax tools with dozens of loose pieces can easily break a wax pattern during de-mold, chills can also be required for thicker sections in wax tools. A foam pattern is
strong enough to withstand complex tools that incorporate a multi-piece design and chills are not necessary to achieve a thick section in a pattern. In addition, foam does not require setters or special handling as a wax pattern will. Currently Legacy Foam is providing foam patterns to the foundries that are strong and ready for slurry.
24 ❘ March 2021 ®
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