“
Design consultation on post-casting machining and surface finishing, prior to tooling design, die construction and die cast production, is the recommended course of action.”
be protected from deburring or polishing. (Fig. 2). Die Cast Mounting Features:
Wherever possible, create raised “shoulders” on bosses that will receive painting masks; scuffing thus can be avoided on surround- ing painted surface areas during fastener torqueing and mounting of mated parts (see Figs. 3). Die Cast Bosses: Include cor-
rectly designed gussets to improve die fill and avoid resulting sink marks on Class “A” surfaces. Short and stocky bosses are preferable to tall, thin designs to optimize metal flow and insure integrity of the feature (Figs. 4). Die Cast Corners: Use the
Fig. 4. Tall bosses (left) can lack integrity for support, but shorter bosses with gussets optimize designs.
maximum allowable radius for all internal and external corners to permit vibratory deburring media to reach all part surfaces. Tis de- sign guideline for die cast corners of housings is also vital to assuring the complete filling of the die cav- ity and maintaining the integrity of the corners of the part (see Fig. 5). Die Cast Surfaces: Subtle
textured surfaces can be produced, as-cast, on selected areas of a com- ponent by special preparation of the die. Tese cast-in textures are created by photoengraving tech- niques during die construction and are sometimes recommended for use on the underside of complex parts to aid in the smooth filling of the die (Fig. 6).
Finishing Steps and Alternatives
Depending on the specifications
on durability, protection and cos- metic appearance, most aluminum, magnesium and zinc die castings will receive one to three post- casting finishing steps: deburr- ing, conversion and/or combined conversion functional coating, and a final surface finish coating. Post-Trim Deburring: Vibra-
tory processes including auto- mated operations using a range of media types, are used to round sharp edges, remove burrs, loosen flash and debris, and smooth and
36 | METAL CASTING DESIGN & PURCHASING | Nov/Dec 2015
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