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details DESIGN


As-Cast Features, Heat Sink Properties Key in Headlight


JITEN SHAH, PRODUCT DEVELOPMENT & ANALYSIS, NAPERVILLE, ILLINOIS CASTING PROFILE


Cast Component: Headlight sub-assembly consisting of mounts for daytime running lamp (DRL) and turn signal.


Casting Process: Diecasting. Material: 380 aluminum.


Weight: 0.27 lbs. (DRL) and 0.54 lbs. (turn signal).


Dimensions: 10 x 4 x 2 in. (DRL) and 4 x 3 x 4 in. (turn signal).


mounting surfaces, which were required to be parallel. T e assembly also required tight tolerances for the lens hole position, which provided wiring access for the bulbs. T e part needed a rigid material to hold up to component assembly and mounting.


A Daytime Running Lamp Mounts


Generous corner radii and fi llets reduce stress concentration.


• Smooth transitions allow tranquil fl ow of the liquid metal into the cavity, without any inclusions and re-oxidation products being trapped.


n OEM for a headlight subassembly was looking for an alterna- tive to plastic for daytime running lamp and turn signal mounts. Diecast aluminum was chosen over plastic for its heat sink char- acteristics, which would conduct heat away from the LED bulbs. Aluminum also allowed for consistent dimensions at the bulb


Turning Signal Mount Heat sink fi ns with appropriate spacing and fl atness ensure proper thermal performance.


• T e casting must be sound at the root of the cooling fi ns—any shrinkage or porosity will act as an insulator. Using casting process simulation, die cooling (for heavy sections) and heating channels (for thin sections) can be optimized for better thermal balance, which assures sound castings. T e fi ns’ root areas must have generous fi llets, and their corner radii must be suffi cient. Sharp radii will cause the casting to stick during ejection from the die cavity, leading to distortion.


20 | METAL CASTING DESIGN & PURCHASING | Jan/Feb 2012


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