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details DESIGN


As-cast cored slot enables assembly into the frame.


• A sand-cored as-cast cored pocket replaced an expensive ma- chined slot and was designed carefully to avoid metal penetra- tion and sand burn-on, leaving a clean surface.


• When the core is surrounded by metal from both sides, its thickness is driven by the section thickness of the metal and core cross-section thickness.


• A local solidifi cation time profi le of the casting during solidifi - cation shows a hot spot inside the pocket area. Casting process modeling can be used to ensure the cored pocket is not going to pose metal penetration and sand burn problems, which will make the decoring operation diffi cult.


Smooth transitions leads to better fatigue life.


• Steel castings designed for optimal directional solidifi cation will be made more effi ciently and repeatedly sound.


• Smooth transitions from square to round cross sections is a must to avoid localized stress concentration for bet- ter fatigue life.


The casting’s hot spot is fed by the riser for a shrinkage-free critical area.


• A hot spot is the region last to solidify in a casting, leaving a shrinkage void.


• A fl exible gating system allowing progressive fi lling is key in making a clean and sound casting consistently with optimum mold yield and fewer risers. By eliminating risers and its connections, the casting surface fi nish is better, eliminating the secondary cutting and grinding operations.


Jiten Shah is president of Product Development & Analysis (PDA) LLC, Naperville, Ill., and a 25-year casting design and manufacturing veteran.


Mar/Apr 2013 | METAL CASTING DESIGN & PURCHASING | 21


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