details DESIGN
Generous draft, corner radii and fi llets aid tooling production and mold life.
• Here, the design was adjusted to produce the casting without the use of any core or core pins, which require additional maintenance.
Permanent mold gravity casting can produce thin walls and elevated mechanical properties due to rapid cooling rates during solidifi cation of 300 series alloys.
• Sound, thin walls can be cast in permanent mold using careful design. In the process, directional solidifi cation and/or localized cooling or heating rates can be achieved with the use of mold coatings and external aids in selected areas. T rough computer simulation, design engineers can validate the casting confi guration and mold design with the desired thermal balance and predict the casting quality ahead of time.
• Corner radii and fi llets eased tooling production, reduced heat concentrations, particularly in the mounting lugs-to- rib junctions, and helped with casting fi lling and solidifi cation.
Molded pockets provide better internal soundness compared to heavier section thicknesses and reduce overall component weight.
• Pockets produced with metal tooling incorporating carefully designed cross ribs assisted in feeding the mounting lugs. T e ribs also reduced casting distortion during solidifi cation and heat treatment cycles for better dimensional reproducibility and tolerances.
• Attaching a mounting fl ange with the lugs wherever possible aided feeding.
Jiten Shah is president of Product Development & Analysis (PDA) LLC, Naperville, Ill., and a 25-year casting design and manufacturing veteran.
Jul/Aug 2012 | METAL CASTING DESIGN & PURCHASING | 21
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