details DESIGN
Key features, like as-cast mounting holes, are positioned in the main die cavity, away from the movable slides and core pins.
• Careful design and selection of die materials and core pins, which aff ect hole position tolerances, are key in the diecasting process. Movable slides and core pins wear out cycle after cycle and add variability.
Cored pockets and holes are coplanar to the parting plane.
• Optimized feature locations make die fabrication simpler and less ex- pensive and lead to sounder castings.
Parting plane location impacts as-cast dimensions.
• Your die casting supplier should optimize die cycle times and utilize tight temperature and pressure controls. Metal shrinks as it solidifi es and cools, so the die cavity is made larger to achieve tighter dimensional tolerances. Parting plane location and draft are important because the casting has to be stripped away from the die cavity every cycle after cooling.
Jiten Shah is president of Product Development & Analysis (PDA) LLC, Naperville, Ill., and a 25-year casting design and manufacturing veteran.
Jan/Feb 2012 | METAL CASTING DESIGN & PURCHASING | 21
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