Identification of tool parallel axis offset through the analysis of the topography of surfaces machined by peripheral milling

A method for the identification of the tool parallel axis offset (TPAO) that occurs when the end mill is held in the spindle is developed. The method is based on the analysis of the topography of surfaces machined by peripheral milling and considers the cutter grinding errors. As known from the literature, TPAO causes each cutting edge to be at a different radius from the spindle axis and creates transition bands in the topography of milled surfaces, in which roughness grooves generated by different teeth blend together. In this paper, the TPAO, defined by the distance of the tool axis from the spindle axis and by an angle relating the offset direction to the position of cutting edges, is expressed as a function of the width of the roughness grooves at any height of the transition bands. This expression allows the TPAO to be estimated by measuring the groove widths at only two heights and solving a system of two linear equations. In order to obtain the groove widths, a procedure based on digital image processing is developed. Through this procedure, the groove widths are estimated at more than the two necessary heights without high computational cost. This leads to the resolution of an overdetermined system of linear equations that allows the TPAO to be identified with more accuracy. Finally in order to verify the predictions of the proposed method, a series of cutting tests were carried out. A reasonable agreement between the experimental results and the predicted ones was found.