Patent ID: 8589103
Filing Date: 2013-11-19
Classification: B23Q,G01B

Abstract:
1. An on-machine measurement method in which a machined surface shape of a workpiece machined by a machine tool is measured on the machine tool, the machine tool having a table with a workpiece holding mechanism for holding a workpiece, a tool holding mechanism section for holding a tool, and a feed mechanism section for relatively moving the table and the tool holding mechanism section in a first axis direction to parallel move the table and the tool holding mechanism section relative to each other, in a second axis direction, orthogonal to the first axis direction, to approximate and separate the table and the tool holding mechanism section, and in a third axis direction orthogonal to the first and second axis directions, comprising: arranging a reference mirror having a specular reference surface on the table; arranging a first laser displacement sensor for measuring displacement of the machined surface of the workpiece and a second laser displacement sensor for measuring displacement of the reference surface of the reference mirror on the tool holding mechanism section; driving the table and the tool holding mechanism section in the first direction and the second direction by the feed mechanism section and thereby relatively moving the table and the tool holding mechanism section so as to draw a sinusoidal trajectory oscillating in the second axis direction along a scanning direction coinciding with the first axis direction, and measuring displacement of the machined surface by the first laser displacement sensor and measuring displacement of the reference surface by the second laser displacement sensor during the relative movement of the table and the tool holding mechanism section; analyzing the obtained machined-surface displacement data and the obtained reference-surface displacement data to calculate sensitivity of the first laser displacement sensor and then correcting the machined-surface displacement data on the basis of the calculated sensitivity; and calculating the actual shape of the machined surface by taking the difference between the corrected machined-surface displacement data and the reference-surface displacement data, wherein: the sensitivity represents the degree of influence of error factors caused by the machined surface upon a displacement component coming from the machined surface shape and a displacement component coming from movement errors of the feed mechanism section, the displacement components being included in the machined-surface displacement data; a component of the sinusoidal trajectory is separated from each of the machined-surface displacement data and the reference-surface displacement data, and then an amplitude ratio thereof is calculated and the sensitivity is set on the basis of the calculated amplitude ratio; the sinusoidal trajectory is defined by an equation: when a coordinate value of the first axis is a and a coordinate value of the second axis on the sinusoidal trajectory is b A is a single amplitude of the sinusoidal trajectory and a λ