Bill-Niebolo-NASF

The Basics of Automotive Surface Engineering by Isotropic Superfinishing

By : Bill Nebiolo ,

ABSTRACT

Certain machined, engineered components are functionally operative because they interact with their complementary partners to transmit energy/motion. Examples are bearings or gears. As a function of their operational efficiency, the metal-to-metal contact location becomes an area of engineering concern since this contact point is a probable area of parasitic frictional resistance. As such, the finish of the metal-to-metal contact areas becomes a critical variable in the efficiency equation related to energy or motion transfer. Typically, machined parts that have been polished to improve their final surface finish will have a unidirectional surface pattern that corresponds to the direction of polishing. Although the polished surface is improved, the presence of
polishing line asperities minimizes metal-to-metal contact because component contact is asperity peak-to-asperity peak.
Vibratory bowls are commonly used for generic deburring. By utilizing non-abrasive, high density media in conjunction with an isotropic superfinishing (ISF) chemistry, surfaces can be superfinished to an isotropic or random finish. This improved surface increases energy/motion transfer efficiency in the metal-to-metal contact area by reducing friction and providing several engineering advantages. This paper will review the technique used to generate the isotropic surface finish and will also review some of the engineering advantages that can be imparted to metal-to-metal contact surfaces.

Introduction

Certain machined, engineered components are functionally operative because they interact with their complementary partners to transmit energy/motion. Examples of engineered items that transmit energy/motion are bearings or gears. These engineered items transmit energy/motion by rolling, sliding, rotating or engaging their complementary partners.

As a function of their operational efficiency the metal-to-metal contact location of the complementary partners becomes an area of great engineering concern, since this contact point is a probable area of parasitic frictional resistance. As such, the finish of the metal-to-metal contact areas becomes a critical variable in the efficiency equation related to energy or motion transfer.

Typically, machined parts that have been subsequently polished to improve their final surface finish will have under magnification a unidirectional surface pattern that corresponds to the direction of polishing. Although the resulting polished surface is improved versus its original machined condition, the presence of the polishing line asperities minimizes metal-to-metal contact between complementary components because component contact is actually asperity peak-to-asperity peak.

Vibratory bowls are commonly used in metal finishing for generic deburring. By utilizing non-abrasive, high density media in conjunction with an isotropic superfinishing (ISF) chemistry the surfaces of the complementary components can be superfinished to an isotropic or random finish. This improved surface increases energy/motion transfer efficiency in the metal-to-metal contact area by reducing friction and providing an additional number of engineering advantages.

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