Casting Study: Housing Cover and Thumbturn – Medeco STEELGUARD(tm) Lock

To meet market requirements, Medeco wanted to develop a new high security lock priced just below its top-of-the-line dropbolt lock. The high-end lock model is all brass. The housing cover is investment cast, and the thumbturn is a machined extrusion. As other processes and materials were eliminated, engineers settled on zinc die casting for the housing and thumbturn. To enhance the surface finish of the casting, a texture finish is integrated into the tooling. The housing and thumbturn are cast with a brush satin finish on the face surface and a textured finish on the side surfaces. In addition, the Medeco trademark is cast into the face of the housing. The finished pieces are lightly buffed, and then copper, nickel and brass plated. Copper adds plating adhesiveness; nickel, corrosion protection; and brass, decor. A clear polyurethane coating is applied after plating for protection and appearance. The die cast and plated components result in a cost savings of approximately 50 percent over the previous method without sacrificing function or aesthetics.

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