to casting larger parts out of a range of alloys. Like direct metal, printed molds and cores allow foundry engineers to challenge old design limitations, moving gates, risers, parting lines, and vents to the places where they are the most useful, and eliminating assembly errors by making complex, multi-piece cores in a single model. This method is also frequently faster and cheaper than building tooling, even with existing designs. 3D Printed Investment Casting Waxes Probably the second most well established Additive Manufacturing (AM) process for making castings is to print the “wax”. Once again, by forming the target shape in an additive process, but making the shell with the traditional process, manufacturers can more rapidly accept that they are pouring the alloys they want, in the shell materials which they are familiar with. Tech Cast, in their article, outlines the slight differences in 3D printed patterns – which are more than offset by saving (in that example) $35K and 5 weeks on the casting. While the SLA process outlined by Tech Cast is well documented, other materials such as PMMA, PLA, and regular old WAX are available through other 3D printed platforms. Each process provides a different combination of speed, accuracy, cost, and processing time. A variant of this method, lost foam casting, is in development several places. In this case, the “foam” pattern is made by a hollow 3D printed shell. The thin shell decreases the time and cost of 3D printing very large parts. 3D Printed Tooling for sand casting (patterns & core boxes) This is probably the most straight forward path to metal using AM. Making your pattern board’s gates, and risers with a plastic or composite 3D printer isn’t rocket science, but it does provide one goose-bump inducing benefit… a new ‘patternmaker’ pool of employees is graduating from tech schools around the country. While these students aren’t studying woodworking or patternmaking in school, they are getting a decent primer on CNC programming, robotics, and 3D printing. So, whether you are running a plastic filament extruder, SLA, SLS, or direct metal printer – you can always “print” your traditional tooling. In the case of permanent molds or die casters – you can near net cast your iron tooling – reducing the cost and CNC time of machining a traditional tool, while enabling tricks like weight reduction, built-in features, and conformal cooling. Foundries like AFG, Alliant Castings, and Danko have all been using 3D printed patterns for a while, and many others are bringing the technology in-house. Another Technology of Note: Robotic Sand Milling – while the devil is in the details, the big picture concept is easy to grasp. Modern robots, like those made by ABB, can be converted into 6 axis milling systems, with automatic tool change. CAM software can let you plan tool paths, and mill the sand molds directly from pre-cast blocks of traditional resin bonded sand. This process is highly complementary to 3D printing, as the trade-offs in cost and speed for each process essentially dovetail with the other process. There are a few integrators who specialize this, and they can keep you from reinventing the wheel. Southern Cast Products, in AR, has several systems running. The killer app for this process is with BIG molds. You can machine mold sections up to 8’ by 8’ and never make tooling for those large, low volume tools again. In Summary As casting buyers you’ll want to know the details of how additive manufacturing is changing the economics of procurement. Each of the foundries in this publication has already put their own process into place, and has shown the commercial viability. As other foundries start to follow the pioneers, a buyer will be able to search for the right foundry and the best process for any given casting. These articles are a good start, but I urge you to reach out to all of these foundries, to visit and learn more. Contact: WILL SHAMBLEY
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