Horsepower Retention by ISF (Isotropic Superfinishing) of Automotive Racing Components
By : Bill Nebiolo ,
ABSTRACT
By: William P. Nebiolo, REM Chemicals, Inc.
Automotive power and drivetrain components typically transfer the energy from fuel combustions through a series of metal-to-metal mechanical components. Typical examples of metal-to-metal components include bearings, camshafts rotation and gear teeth in a transmission or differential.
The normal manufacturing steps for bearings and camshafts typically include various machining operations that normally end with a final grinding step. For economical reasons, automotive transmission and differential gears are usually lapped to generate the final surface finish. A careful examination of the as manufactured surface of these components reveals a polishing pattern associated with the final grinding or lapping step used to finish the component. Typically the pattern is visible as parallel rows of micro-asperity peaks and valleys.
In operation these mechanical components work by engaging their complementary partners. As such, bearings roll in races, gear teeth roll and slide against other gear teeth and camshafts engage cam followers. The presence of the micro-asperity peaks and valleys on the surface of these components reduces the actual available area of metal-to-metal contact. This results in frictional heat generation and a loss of engine horsepower.
This paper will examine the use of the ISF Process to improve the micro surface of automotive metal-to-metal contact surfaces. Evidence will be presented demonstrating how the improved micro surface of ISF processed parts retains horsepower, increases component durability and reduces operating temperature.
INTRODUCTION
Traditionally, automotive engine parts such as camshafts, rocker arms and valve springs, drivetrain parts such as transmission gears, shifting linkages and splines, differential parts such as rings and pinions, and universally mounted components such as bearings operate by rolling, sliding or pushing against their complementary partners.
Several OEM manufacturing steps are required to produce these components. These include, but are not limited to various combinations of forging, blanking, cold heading, and machining, hobbing and hardening operations such as thru-hardening, induction hardening, case hardening, nitriding, etc.7, 8
OEM FINISHING
OEM manufacturers will typically employ a final grinding operation to remove heat treatment warping, generate the final dimensions/geometry and achieve the ultimate surface finish. Automotive gears are typically lapped for economy reasons. See Photo 1.
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