Tool wear and form accuracy in ultrasonically machined microchannels

Quantifying wear on the basis of weight at micro levels may be erroneous. Moreover, information about wear distribution cannot be obtained on the basis of weight monitoring. Thus, quantification on the basis of linear measurements is an effective solution at micro levels. This paper presents a mathematical model for quantifying wear measured in two dimensions and subsequently converting it to a three dimensional wear model. The efficacy of the model was verified through machining data from ultrasonic micromachining of glass with tungsten carbide tools. The tool wear values obtained for the model was then correlated with the form accuracy of the machined microchannel which were found reasonable. Further, the effects of different process parameters like abrasive concentration, power rating, abrasive size and workpiece feed were studied on the tool wear behaviour and presented vis-a-vis microchannel form accuracy. High power rating and high abrasive concentration resulted in more tool wear and increased form inaccuracy; coarse abrasives resulted in higher form inaccuracy. Longitudinal wear resulted in decreased microchannel depth while lateral wear led to tapered microchannel walls and edge rounding wear yielded rounded corners in the fabricated microchannels.