Excerpt from the November 2017 issue of Additive Manufacturing by Brent Donaldson
Atop a high plateau between the Susquehanna and Delaware Rivers, American manufacturing used to run through the heart of Hazleton, Pennsylvania. Or at least large deposits of high-carbon anthracite coal, the discovery of which helped launch the United States to global dominance in manufacturing throughout much of the 19th and 20th centuries.
Today, tucked behind the Weir Minerals building off of North Cedar Street, you’ll find the Hazleton Casting Company (HCC)—a specialty high alloy foundry that utilizes centuries-old techniques for its casting operations, which serve makers of pumps and valves among many other manufacturers. But you’ll find something else there, too: a quiet glimpse into the future of industrial foundry operations.
A mechanical whir within a small warehouse adjacent to HCC is the casting call of a Viridis3D RAM123 robotic sand printer—a “game-changer,” as HCC President Tony Badamo calls it. Located just a stone’s throw from the foundry furnaces, the Viridis machine prints molds and cores straight from a digital model into a bed of sand, one sweeping layer at a time, without any need for a pattern or core box, the tooling that has long been typical of industrial casting.
A Perfect Dilemma
It was only a few years ago when Hazleton began exploring additive technologies to complement its existing toolmaking capabilities and started subcontracting with outside printing bureaus to manufacture molds and cores from customers’ digital models. But when problems arose with any given outsourced product—excessive slag, shrink defects from the alloys reacting with the environment, or mold design flaws such as improper placement of the risers—the variables were numerous enough that pinpointing a root cause was difficult at best. Was there a quality issue with the sand? Was the binder distribution from the print head consistent? Was there a defect resulting from the geometry of the mold itself?
From the customer’s perspective, of course, the onus to get it right falls squarely on the foundry. “We ran into problems where there was a lot of finger-pointing,” Badamo says. “When that happened to us the first time, we knew that if we were going to be a player in this market and in this environment, we needed to get this process in-house.” HCC purchased the Viridis machine in November of 2016.
By printing molds and cores straight from CAD from the sand printing system, Hazleton can offer customers a production timeline of three to four weeks for a prototype or final part, rather than the three to four months typically required when patternmaking and core box machining are part of the process.
All the Sand That’s Fit to Print
In Hazleton’s case, the concept of flexibility goes beyond complex design geometries that 3D printing is capable of producing. Much of the sand in a mold is not in the detailed features; it’s contained in the thick, safe mass of the mold that is strong enough to support casting. Of course, time on the 3D printing system is expensive, and printing sand is pricier than foundry sand, so as each span of the print head deposited sand to build the simple mold shell wall, Badamo’s team realized that it was essentially wasting time and money. A lightbulb went off, Badamo says, and the team devised a money-saving method based on one simple philosophy: Print what needs printing, and don’t print what doesn’t. The solution? Place the mold cavity shell—without the wall—into a flask (the reinforcement tooling, typically box-shaped, used to contain molds in foundry casting) and pack it with foundry sand. That is, in the same way sand might be packed around a pattern, pack the sand instead around the complex 3D-printed form.
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