“
We have proven the
technology is viable. The next step is a matter of making it
competitive...Now it’s about improving our processes and materials so these castings are the best we can produce.” —ADAM LOUKUS, REL INC.
proved challenging for casting simu- lation software. “Because of the constant curvature of the internal structure, it is ex- tremely diffi cult to model effi ciently. T e structure is such that we need to develop simplifying techniques to model and analyze the fi nal tanks. It almost cripples the CAD and FE
programs we use,” Adam Loukus said. “While the structure is effi - cient, it’s computationally taxing.” T e fi nal casting would be a single aluminum component, but it would require a number of sand cores, which could be stacked atop one another to produce the com- plex cavity. REL Inc. produced the
majority of these cores in house, though some were 3-D printed for prototype models.
Castings to Meet Demanding Parameters
T e tank needed to operate at
3,600 psi, though it had to with- stand a burst pressure of 8,100 psi. T is demand placed a premium on uniformity in casting, because inconsistencies in the casting wall could result in failure. T e low pressure permanent mold
process was appealing because it could reduce turbulence while the mold is fi lled with molten metal. REL Inc. partnered with Eck Industries Inc., Manitowoc, Wisconsin, to produce the fi rst version in 7075 aluminum. “It wouldn’t do us much good
to have great properties at the top of the tank if we have trouble near the gates,” Adam Loukus said. “It required a lot of process improve- ments and changes to the low pres- sure process. We needed to optimize the gating. We needed to introduce the metal in the most uniform man- ner possible.” T ose fi rst articles proved prom-
ising, though engineers eventually opted to cast the tanks in A206 aluminum, because of its improved structural strength.
REL Inc. produced the complex core struc- ture by stacking sand cores on top of one another.
24 | METAL CASTING DESIGN & PURCHASING | Mar/Apr 2016
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