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TECHNICAL PAPERS

Thermal Expansion of the Workpiece in Turning

[+] Author and Article Information
D. A. Stephenson, M. R. Barone

Engineering Mechanics Department, General Motors Research and Development Center, Warren, MI

G. F. Dargush

Civil Engineering Department, State University of New York at Buffalo, Buffalo, NY

J. Eng. Ind 117(4), 542-550 (Nov 01, 1995) (9 pages) doi:10.1115/1.2803532 History: Received May 01, 1994; Revised September 01, 1994; Online January 17, 2008

Abstract

Thermal expansion of the part can be a significant source of dimensional and form errors in precision machining operations. This paper describes a method for calculating the thermal expansion of an axisymmetric workpiece. The analysis is based on a commercially available boundary element code modified to properly represent concentrated moving heat sources such as those produced in machining. The inputs required are the amount of heat entering the part from the cutting zone and the thermal properties of the workpiece material. Calculations are compared with direct measurements of expansion from tests on large diameter 2024 aluminum sleeves. The agreement between calculated and measured values is generally reasonable, although calculated expansions are consistently smaller than measured expansions. This error is probably due to errors in estimating the heat input to the part, and particularly the neglect of flank friction in heat input calculations. Sample calculations for hard turning of a wheel spindle show that expansions can approach tolerances on critical surfaces. Based on sample calculations, thermal expansion is likely to be significant when hard turning parts with tolerances on the order of 0.01 mm. For these applications, critical surfaces should be machined first, before cuts on other sections heat the part, and gaging should be carried out only after the part has cooled.

Copyright © 1995 by The American Society of Mechanical Engineers
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