Multicomponent Calibration of Machine-Tool Dynamometers

Abstract

Service loads of machine-tool dynamometers are usually reduced to a system of three mutually orthogonal force components through a fixed reference point. Three additional components (moments) result if the resultant cutting force does not pass through the reference point. At least some of these six components reach finite values under machining operations; sometimes all six must be considered. It follows that the response surface of the output signal of each channel to all six components must be known in order to evaluate the measurement process. Six component calibration of multi-component dynamometers, such as, e.g., wind tunnel balances, is known to be a rather expensive and time-consuming operation. It will be shown that, under some rather general limiting conditions, useful estimates of the response surface parameters may be obtained with a reasonable number of straightforward tests. Expensive special purpose calibration stands are dispensed with, simple jigs and general purpose equipment being all that is needed for most applications. The performance of machine-tool dynamometers may, therefore, be analyzed in detail, and a good understanding of their measurement capabilities may be obtained, even when operating under a light budget. Details are given concerning the application of the proposed method to a tool-post-type lathe dynamometer.