After the initial casting process, the interior of the dynamo was machined on PCM’s five-axis milling machines.
dry conditions, and PCM duplicated the molding and gating process to achieve consistent casting geometry.” Considering the complexity of the
large-scale project, university profes- sors and PCM engineers benefitted from the local connection. “It was an enormous advantage
to actually talk to the people mak- ing the object and to work with them when we were designing the experiments,” said Cary Forest, UW-Madison physics professor. Casting the two sections in A356-2 aluminum, PCM built massive air set molds to cast the 11,500-lb. hemispheres. (Te sec- tions each weighed 6,800 lbs. after machining.) At nearly 75,000 lbs., each mold included numerous ris- ers and a complex system of chills. “Te casting required approxi-
mately 1,640 chills, which were all placed in the same locations to influence solidification,” Griep said. “Special attention was paid to timing our shakeout procedure as we knew this would be critical in trying to duplicate both shrink and casting geometries.”
In addition to a number of pour-
ing-related complexities, the hemi- spheres had to be machined heavily before delivery. Tirty-two stainless steel “water lines,” the concentric circles that ring the sphere’s interior, needed to be placed in exact locations to allow for proper temperature con- trol. PCM then tested the hemispheres
for vacuum integrity, before an outside firm coated the interior in alumina to hold up to the high temperatures. Te completed dynamo was delivered to the university in January 2012.
Business in Learning Tis unique project shows what
metalcasting facilities are capable of producing for large-scale projects. But PCM’s contribution to scien- tific research also highlights pub- lic research funding as a potential revenue stream, as the relation- ship between the metalcasting facility and the UW-Madison is ongoing and orders continue to be placed. “Tis relationship is more
Engineers used approximately 1,640 chills to ensure both hemi- spheres solidified uniformly.
important than ever,” said Dan Griep, PCM director of tooling. “Tere are a lot of funds flowing through the state of Wisconsin in these projects. If we can capture even half of the new UW busi- ness, it would have a huge impact on employment and enhance our ability to identify new business and understand where we should focus in the future.”
October 2013 MODERN CASTING | 41
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