affect the ability of the part to resist wear and fatigue; to assist or destroy effective lubrication; to increase or decrease friction and/or abrasion with mating parts; and to resist corrosion. As these characteristics become critical under certain operating conditions, the surface fi nish can dictate the performance, integrity and service life of the component. The role of mass-fi nishing processes (barrel, vibratory, centrifugal and spindle fi nishing) as a method for removal of burrs, developing edge contour and smoothing and polishing parts has been well established and documented for many years. Less well known and less clearly understood is the role special- ized variants of these types of processes can play in extending the service life and performance of critical components or tools in demanding manufacturing or operational applications.
Manufacturers have
discovered that as mass fi nishing processes
have been adopted, an unanticipated development has taken place—their parts are better.
To understand how edge condition and surface topography improvement can impact part performance, some understanding of how part surfaces developed from common machining, grinding, honing, and other methods can negatively infl uence part function over time. A number of factors are involved: 1) Positive vs. Negative Surface Skewness: The skew of surface profi le symmetry can be an important surface attribute. Surfaces are typically char- acterized as being either negatively or positively skewed. This surface charac-
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teristic is referred to as Rsk (Rsk—skewness—the measure of surface symmetry about the mean line of a profi lometer trace). Conventionally machined parts usually display a concentration of surface peaks above this mean line, a positive skew (Fig 1.).