Acoustic Emission Characteristics of Abrasive Flow Machining

Abstract

Abrasive Flow Machining (AFM) is a nontraditional finishing process that deburrs and polishes by forcing an abrasive-laden viscoelastic polymer across the workpiece surface. Current applications include improvement in air and fluid flow for cylinder heads, intake manifold runners and injector nozzles. Present manufacturing methods include a series of flow test and AFM operations which require significant material handling and operator adjustment. An effective on-line monitoring and adaptive control system for AFM is needed. This paper reports on the development of an acoustic emission (AE) based monitoring strategy and the AE characteristics of abrasive flow machining. Initial results showed AE to be a viable sensing method for determining the performance characteristics of AFM for simple extrusion passage geometries in a selected part design. The root mean square (RMS) voltage of the AE signal was mainly determined by the metal removal and related AFM process parameters. Frequency decomposition of the AE signals revealed distinct frequency bands which have been related to the different material removal modes in AFM and to the workpiece material. Research was also performed on the application of AFM to finish orifices of varying sizes. Extremely high correlations were found between the AE signal and both the orifice diameter and the volumetric flow rate. Work is continuing with the equipment manufacturer and key industrial users to apply the monitoring strategy as part of a prototype Flow Control AFM.