A Methodology for Machining Process Characterization

A number of analytical tools have been used, without any significant success, in the machine manufacturing industry to predict performance of machining processes. The overall equipment efficiency numbers realized on the plant floors provide the supporting evidence of a need of considerable improvements and offer an opportunity for the development of methodologies to characterize the machining processes before installation on the plant floor. Mechanical vibrations signature analysis approach has been used to characterize machine components on the plant floor, but in a limited capacity and under idle conditions. However, attempts to establish vibration standards in machining process characterization without exercising machining loads can cause a false sense of security.

This paper describes a methodology of characterizing a given machining process by considering the machine structure, tooling and spindle, workpiece fixture, and the part as the major elements of the machining process. The machining loads associated with the speeds and feeds dictate the response of the major elements and thus the performance of the machining process. The unique aspects of a machining process can be demonstrated through the fact that two alike machines may give acceptable or unacceptable levels of performance. Process characterization under machining loads is essential to determine the interactions among the major elements. This integrated system characterization approach is demonstrated through an application in identical turning operation on two machines. This approach has been successfully used to improve machining process robustness, reliability, capability on the plant floor, and reduce manufacturing costs.