material to remove,” Willson said. T e walls of the casting are 0.06 in.
but have been reinforced with a web of checkerboard ribbing to provide stiff - ness. T e ribs serve a dual function by helping to feed metal into the bosses on the wall. Investment casting excels at casting
part detail but is a relatively expensive casting process. For O’Fallon Casting, part size is a greater cost factor than part weight or complexity. “T e more detail incorporated into
a design, the more cost eff ective invest- ment casting becomes,” Willson said. T e designer of the electronic hous-
ing packed as much value as possible into the part, adding features to im- prove function, reduce machining cost and aid manufacturability. T e design reduced the total part count, leading to reduced costs of procurement, assem- bly and inventory. Among the features that have been
incorporated are diffi cult to machine “D” shaped holes that are fl at on one edge and then rounded off , cast to net size and shape. A rectangular open- ing on the bottom of the part likely to be used for a screen includes cast-in hooks to clamp it in place. T in fi ns on parallel sides remove heat. T e fi ns are relieved on one side for access to screw on a cover. The interior configuration is un-
dercut and provides a sealing surface on top of a thin wall between the top and bottom half of the casting. A slot consisting of two vertical rails opposite each other is cast-in for insertion of a card or similar device. On the part’s superstructure, what
looks to be a thick wall is actually hol- lowed out from the backside to remove
MEDIA RESOURCE Using the Actable App, scan this page to watch a video
pointing out the features of O’Fallon’s casting. For instructions on how to use the app, go to page 3. To watch online, go to
www.metalcastingtv.com
Electronics Housing O’Fallon Casting, O’Fallon, MO
Material: A356-T6. Process: Investment casting. Weight: 2.2 lbs. Dimensions: 7.5 x 7.5 x 10 in. Application: Defense industry.
• T e customer avoided hours of fabrication and assembly by combining mul- tiple parts and features into a single, rigid piece. It is lighter and more pre- cise than a comparable fabrication; secondary machining was minimized.
• T in walls (0.06 in.) keep the weight low, while a lattice of ribbing pro- vides rigidity. Holes and slots further remove unnecessary material.
May/Jun 2013 | METAL CASTING DESIGN & PURCHASING | 21
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