details DESIGN
Hole feature is well designed to support core.
• Since cores are surrounded by metal, they undergo mechanical stresses during solidifi cation due to volume change and during fi lling due to hydrodynamics and momentum. To withstand the stresses, cores must be secured and well supported inside the mold cavity.
• A core pocket provides the form, fi t and functionality of the component and reduces its weight.
• In the shank pivot mount, a core print, which is the area that comes in contact with the mold and provides the bearing surface to locate and support the core, is oriented parallel to the parting plane for ease of placement and molding. T e core print vents the gases generated from the core, which is surrounded by liquid metal.
CASTING
Integrating features makes casting sounder and easier to produce.
• Metalcasting involves solidifi ca- tion and cooling of the liquid metal in the mold, leading to volumetric changes and possible shrinkage porosities. Building metal feeding paths into the casting design eliminates the need for additional risers, which are required to introduce liquid metal into a casting section to make it more sound.
• Casting shapes are complex, and predicting solidifi cation behav- ior can be diffi cult. Computer modeling and casting design rules should be used to validate complex shapes before releasing the design.
Jiten Shah is president of Product Development & Analysis (PDA) LLC, Naperville, Ill., and a 25-year casting design and manufacturing veteran.
May/Jun 2012 | METAL CASTING DESIGN & PURCHASING | 23
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