Using 3-D printing for this part had many advantages, and one was the opportunity to make the complex core passages as one unit.
pattern and fi xture costs. Printed core surfaces do not require any draft, so the part weight and wall thicknesses are maintained exactly as designed, with no time lost to dealing with is- sues related to adding draft. Using 3-D printing had other
advantages. One was the opportunity
Engine Cylinder for Aerospace PreciseCast Prototypes & Engineering
(Commerce City, Colorado) By using additive manufacturing
combined with standard rubber plas- ter melding (RPM), PreciseCast Pro- totypes & 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 variability of port height while reducing human error in core assembly and maintaining a negligible change in surface finish. The end result significantly reduced fallout and produced a more repeat- able, 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 fallout not only in mold making but also in maintaining tolerances for proper port height and position.
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 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. ■
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.
May/Jun 2017 | METAL CASTING DESIGN & PURCHASING | 31
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