Mike's Workshop Notebook

Westinghouse Pump Parts

These castings are intended for a future build of a Westinghouse-style, single-cylinder air pump. This effort was primarily an exercise to gain more experience in patternmaking and making cores.

One of the more interesting lessons learned was that the real challenge in casting wasn’t making the patterns or cores—it was designing the gating system. Developing an effective system of sprue, runners, gates and risers, and determining the best way to introduce the molten metal into the mold cavity, proved to be a critical part of the process.

It’s important that the metal flows into the mold smoothly and steadily. Excessive turbulence can introduce a number of problems: oxide formation that weakens the casting, erosion of the mold that can release sand into the cavity, and the potential for gas entrapment leading to porosity. Managing flow behavior is key to producing sound, reliable castings.