ADDITIVE MANUFACTURING is the magazine devoted to industrial applications of 3D printing and digital layering technology. We cover the promise and the challenges of this technology for making functional tooling and end-use production parts.
Issue link: https://am.epubxp.com/i/894355
AM / AM Answers Its Casting Call additivemanufacturing.media 55 the base shape was static, it made sense to build just this much using a conventional pattern. "In this case, it is really not about variation; it's about com- plexity," Badamo says. "When we compared the cost to print versus the cost to actually build the core using conventional tooling, it was pretty close to a wash. The 3D-printed core was almost as inexpensive as the conventional product. We were able to allow our customer to forgo that tooling expense to build that core," which otherwise might have accounted for at least 50 percent of the cost of the tooling, he says. 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 rein- forcement 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. "That's the panache that we didn't have when we were outsourcing," Badamo says. "That's something that we saw by getting the printer in-house and in the hands of people who really know molding." The process hasn't been without challenges. Even with Hazleton's journeymen who spend 8,000 hours learning their trade before they're truly considered a molder at HCC, none of them had ever seen a 3D-printed mold that needed to be pieced together. "We've printed pieces that had men in the foundry scratching their heads," Badamo says. "We have a pump casing that we printed all of the components to, and there's a core that has a feature on it that needs to be indexed properly. We keyed the index the way we would for a core made from a core box, but that meant we put the key in the wrong spot for the 3D-printed version. We got around it and salvaged the part, but that was a learning experience." The Flash Drive Warehouse For all of the new capabilities that sand 3D printing brings to Hazleton's foundry operations, the team still has to work with the designs that customers bring to them. While HCC is capable of providing feedback and design suggestions to its customers, Badamo's team members are not design engineers themselves. That said, AM is pushing engineers who make cast components to consider design optimization, as well driving foundries to rethink solutions to castings previously created with conventional tooling. When a pump company ordered a set of castings based on 25-year-old conventional tooling, Hazleton encountered prob- lems that stemmed from complications of the core shape. The original pattern was made in three pieces with narrow gaps and joints that would traditionally be sealed in the open air. When the original product was manufactured, the tooling was new and the pieces fit together seamlessly. Now, years later, the wooden tooling had warped, creating gaps between the pieces that allowed for metal penetration during the casting. Not only that, but the penetration itself was surrounded by metal, leaving no practical access for machining the error away. Then, another lightbulb went off: Print it all with one body and eliminate the flashpoints. Indeed, this capability of AM—consolidating assemblies—shows great promise across numerous industries, particularly aerospace and automo- tive, where various fasteners and assembly steps can become obsolete through AM. In the case of the pump casting, the advantage was avoiding potential casting errors resulting from poor fit in the tooling assembly. The idea worked. "We made three of them and shipped them out," Badamo says. "Last we heard, they were in assembly and testing, and everything is going really well." Badamo says that in his day-to-day interactions with cus- tomers, the majority don't yet grasp the efficiencies offered by AM. They know what it is, he says, and are familiar with the general processes involved, but don't yet understand or appreciate its capabilities. Yet then there are some customers at the edge of the envelope—customers with legacy products that have made a determination that they simply don't want to own pattern samples. One pump manufacturer is one such example. While the company has a pattern inventory that goes back to its found- ing more than 100 years ago, it concluded that housing those patterns no longer makes sense. The manufacturer is in the process of modeling every product, Badamo says, and looking at 3D direct-to-print molds (in combination with disposable patterns also made with 3D printing) as a means of phasing out the storage inventory entirely. The goal? To have a century's worth of pattern inventory stored on a flash drive. If that isn't progress, it's hard to say what is.