Casting Study: Lubrication Metering Assembly – Graco, Inc.

The design requirements for the assembly’s 10-in.-long housing called for non-tapered walls in the meter chamber, allowing free rotation of the metering gears, and zero draft in the valve area. Previous designs utilized two aluminum castings requiring secondary machining to accomplish these criteria. To simplify manufacturing and reduce costs, the company turned to the zinc die casting process. The zinc die cast housing is produced as a stronger, one-piece component. The previous design required two aluminum castings to be threaded together. Secondly, the housing is cast net-shape, reducing the trim operations. Thirdly, and most importantly, the meter housing is cast with zero draft, eliminating the secondary machining operation in the meter chamber (.530 in. deep) and valve area (1.300” deep). Finally, zinc die casting offers greater dimensional stability than aluminum castings, reducing scrap and rework. As a result of using the zinc die casting process, secondary machining cost were reduced by nearly 80 percent.