Direct Part Fabrication Direct part fabrication involves the


creation of a metal part from powder or filament feed by melting or sintering material via a point energy source, typi- cally a laser. Some of these technologies can be used to repair or “re-grow” a metal part (e.g. replacing a broken tip from a fan blade). Direct metal parts do not neces-


sarily have the full properties of cast metal, but they can be created quickly, without tools or setup. They also can be used in many cases as tooling for molding technologies. Depending on the required proper- ties for the application, these parts can often have functional uses, some of which are in medical implants, art and flight hardware. Consult the sidebar “Direct Metal Part


Production” for details on each of the major methods of direct part fabrication available today.


Indirect Part Fabrication Another method of creating a metal


part from AM is to create a pattern or tool that can be inserted into the standard metalcasting workflow. In the last few years, several new/updated technologies have become available, each of which can be used to differ- ing advantages. The choice of which path to use for a given part depends on factors such as the size of the cast- ing, complexity, number of castings to be made from each tool, and accuracy requirements. Improvements in soft- ware, systems and mate- rials have increased the accuracy, surface finish, usability and fit into the metalcasting workflow. The latest generations of new systems and materi- als are offering lower cost approaches, though per- formance of these systems remains unproven. Consult the sidebar “In-


I


direct Metal Part Produc- tion” for details on each of the major methods of indirect part fabrication. Sand Molds, Cores,


Patterns and Inserts—Pat- terns for sand casting tools can be created by the majority of the AM technology available today. Stereolithography


MODERN CASTING / July 2010


Additive manufacturing involves the fusing of materials layer by layer to form a solid object. Here, a component is created in the stereolithography process, which uses a laser to convert a liquid resin into a polymeric object.


(SLA), selective laser sintering (SLS), 3D printing, jet printing, DLP and fused deposition modeling (FDM) technologies are available at prices ranging from $3,000 to more than $1 million. All of these options provide a means to create a positive tool that can be bolted to a squeeze board, whether powder- or resin-based. Printing a squeeze board pattern can be faster and cheaper than CNC milling the same part, especially as complexity increases. Molds and cores also can be print-


ed directly on 3D printing systems, as well as a few of the laser sintering stations. For many geometry types at low volume, the speed of fabrica- tion and elimination of tooling can make this option favorable. Sands molds are typically silica sand with an organic binder, but the options for refractory and metal choice continues to expand. Investment Casting Patterns—Jet


How Does AM Fit Into Metalcasting Facilities?


nstances of additive manufacturing (AM) equipment being integrated into large metalcasting facilities to provide rapid turnaround patterns, castings or molds are growing. Depend-


ing on the size and financial stability of the metalcasting facility, adopting AM solutions can range from purchasing the occasional core, pattern or mold from a service bureau to installing a fleet of million-dollar AM machines for the in-house creation of mixed direct and indirect metal parts. For many metalcasting facilities, the new generation of smaller,


less expensive AM machines offers a chance to slowly enter the field. Furthermore, AM service bureaus are now located all over the world, and metalcasting facilities can purchase a wide range of patterns, cores, molds or metal parts on demand.


MC


printing, 3D printing, SLA and SLS so- lutions all can create patterns that can be used for investment casting as a replacement for wax patterns. Each system has its own sweet spot for accuracy, cost, surface finish and speed. Picking the correct solution for your customer needs can introduce a wide range of possibilities.


MC For More Information


For more industry data provided by Wholers Associates, visit www.whol- ersassociates.com.


About the Author


William Shambley, who has spent 10 years in materials development for additive manufacturing, is president of Viridis3D LLC, Tyngsboro, Mass.


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