Dynamic design of machine tool structures using an updated model

Structural design modifications using an updated finite element model has emerged as promising techniques with the potential of improving dynamic characteristics of mechanical equipment economically and efficiently. This paper is an attempt to evaluate the effectiveness of application of such a technique by comparing its prediction of modified dynamic characteristics due to design changes with the actually measured characteristics. First, a finite element model of a drilling machine is updated using experimental modal data. The design changes to the machine tool are then considered in terms of a lumped mass and a stiffener. The modified dynamic characteristics are predicted on the basis of the updated finite element model and are compared with the measured changes. The comparison indicates that a reasonable agreement exists between the analytically obtained predictions and the measured changes. This demonstrates that an updated model can be used reliably to tune the dynamic characteristics of even a complex structure like that of a machine tool in a desired way. Some of the possibilities that may further enhance the predictive capability of the updated model are highlighted.