detailset DESIGN
Design Using 3-D-Printed Sand Cores JITEN SHAH, PRODUCT DEVELOPMENT & ANALYSIS, NAPERVILLE, ILLINOIS
CASTING PROFILE
Cast Component: Conformable compressed natural gas tank.
Process: Low pressure semi-permanent mold using 3-D-printed sand core.
Material: 7075 aluminum. Weight: 71.4 lbs.
Dimensions: 11.25 x 11.25 x 20.25 in. (quarter-scale model).
Thermal barrier coating aids directional solidifi cation.
• In semi-permanent molds, where sand cores are inserted into the metal mold to produce internal passages, it is important to control the heat transfer at the metal mold interface to achieve the desired directional solidifi cation, which predicates the overall internal soundness and local mechanical properties.
• Casting process simulation assists in validating and optimizing the process parameters to achieve the desired results. In this case, a proprietary thermal barrier technology was used to help direct solidifi cation.
enables 20-35% more compressed natural gas than a cylinder due to better use of the allowable packaging space. T e tank can operate at 3,600 psi yet withstand a burst pressure of 8,100 psi and tens of thousands of cylindrical loads. T e challenge to the project was to pro- duce a high integrity casting using a stronger alloy. REL and Eck chose to cast the tank in 7075 aluminum alloy using 3-D-printed sand cores with highly complex, fi xed walls coated with a proprietary thermal barrier technology.
C
urrent compressed natural gas (CNG) cylindrical tanks are one- piece formed metal (steel or aluminum) or various forms of carbon fi ber composites. REL Inc., Calumet, Mich., in collaboration with Eck Industries, Manitowoc, Wis., developed a new design for the conformable tank using the Schwarz P-Surface cell design, which
18 | METAL CASTING DESIGN & PURCHASING | Jul/Aug 2015
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