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how the passages relate to the external features of the casting. As with traditional tooling, part- ings and gating design are important processes. Alloy A206 was chosen for this component because it off ers high mechanical properties. T is alloy is known as a diffi cult alloy to cast, as it requires a steep thermal gradient to produce high quality castings. Extra care was taken into consideration to accommodate this alloy with the gat- ing design. CAD was used to model the gating system, and simulation was used to validate and optimize the cast- ing soundness.


Using 3-D printing for this part had many advantages, and one was the opportunity to make the complex core passages as one unit.


issues related to adding draft. Using 3-D printing had other


advantages. One was the opportunity to make the complex core passages as one unit. T e mold assembly is also simplifi ed, and the one-piece design


eliminated the need for costly core- assembling fi xtures. Fillets and blends between passages are maintained, as paste-joints can be avoided. T is strengthens the core assembly and improves the dimensional stability of


Engine Cylinder for Aerospace


PreciseCast Prototypes & Engineer- ing (Commerce City, Colorado) By using additive manufactur-


ing combined with standard rubber plaster melding (RPM), PreciseCast Prototypes & Engineering was able to 3-D print a wax corebox to produce a single plaster core. That replaced the five hand-assembled pieces and greatly reduced the vari- ability of port height while reducing human error in core assembly and maintaining a negligible change in surface finish. The end result signifi- cantly reduced fallout and produced a more repeatable, predictable part, thus reducing manufacturing time and cost. T e standard RPM process (previ-


ously used) required producing fi ve separate plaster core pieces that would be hand-assembled in the exterior mold. T is caused a potential for fall- out not only in mold making but also in maintaining tolerances for proper port height and position.


MEDIA RESOURCE


To watch a video of metal being poured into a 3-D printed sand mold, go to www.metalcastingtv.com.


PreciseCast Prototypes & Engineering was able to 3-D print a wax corebox to produce a single plaster core.


PreciseCast Prototypes & Engineering was able to 3-D print a wax corebox to produce a single April 2017 MODERN CASTING | 27


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