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Automotive air conditioning compressors utilizing aluminum scrolls offer improvements in engine performance and fuel economy by lowering energy consumption, reducing weight, and allowing smaller packaging. This alternative compressor design was first commercially produced in 1981. Since this time, scroll compressors have continually increased their share of the original equipment compressor market for Japanese, European, and US automotive manufacturers. Two essential components in the compressor assembly are the aluminum scroll castings (fixed and orbiting). The first production aluminum scrolls were machined from sand castings. This process was then replaced by squeeze casting, which has now been in use for over 12 years. Forging has recently emerged as an alternative process. The design and structural requirements of the aluminum scroll component challenge both squeeze casting and forging processes.

Squeeze Cast Permanent Mold (SCPM) is a premium grade aluminum casting process frequently used to produce safety critical aluminum suspension components. The emergence of SCPM as a major casting process for suspension components is relatively new in the high volume automotive market. Squeeze cast aluminum components have replaced iron/steel control arms and front knuckles in volume during the last four years. In late 1994, Delphi Chassis Systems and Casting Technology Company (A joint venture between Amcast Industrial and Izumi Industries) began a joint development program for an aluminum front knuckle conversion slated for application on mainstream passenger cars. This was the first high volume production two-cavity squeeze cast aluminum conversion program of its kind. Previously, aluminum conversions on front knuckles were limited to comparatively small volume single platform programs. This joint program is applicable to volumes in excess of 1.5 million cars annually.

Squeeze Cast Permanent Mold (SCPM) is a state of the art casting process targeting high strength, high integrity, and near net shape applications. Most recently, SCPM has been applied to aluminum front steering knuckles, aluminum scroll compressor castings, pistons, and a variety of components sharing the same stringent requirements. Squeeze casting is considered to be a premium grade casting process because it produces comparatively higher strength and superior structural integrity than other competitive processes. This paper will provide a detailed process description of SCPM and demonstrate the benefits of this state of the art casting process. In addition, process attributes will be correlated to casting characteristics that qualify squeeze casting as a premium grade casting process. A process flow diagram and description of a state of the art squeeze casting facility will be provided with a focus on how process controls reduce variation to produce consistent casting results.