Method of operating a machine tool with a sensing probe in order to gather positional data for the calculation of tool offset parameters

Claim 1

The method of operating a machine tool of the kind comprising a tool spindle having an axis of rotation, means for rotating the spindle through predetermined angles of rotation, a table movable relative to the spindle transversely to said axis, a surface-sensing probe mounted on the spindle, means for generating a probe signal at the instant of said probe being brought into a sensing relationship with a surface defined on said table, means responsive to the occurrence of a said probe signal for producing an output corresponding to the position of said axis relative to a primary datum which is fixed in relation to the table, and a computer connected to read said output; the method comprising: (a) providing on the table a first and a second test surface having therebetween a mid-point defining a secondary datum, said mid-point having an actual position (CA) which may differ from a demanded position (CN), stored in the computer, by an error (WO); (b) operating the machine to bring the probe into sensing relationship with the first test surface and produce a first corresponding said output (A1); (c) operating the machine to rotate the spindle through 180°; (d) operating the machine to bring the probe into sensing relationship with the second test surface and produce a second said corresponding output (A2); (e) operating the machine to again bring the probe into sensing relationship with the first test surface, without having rotated said spindle after step (d) above and produce a third said corresponding output (B); and (f) operating the computer to read said outputs and determine the following values: WO=CN-(A1+A2)/2 PO1=(F-(A2-A1)/2, and PO2=A2+PO1-F-B wherein WO=said error, PO1=the distance between said spindle axis and the second test surface at the instant of said first output, PO2=the distance between said spindle axis and the first test surface at the instant of said second output, F=the known distance between the first and second test surfaces, and the position A2 is further from said primary datum than the position A1 and B.

Claim 2

The method of operating a machine tool of the kind comprising a tool spindle having an axis of rotation, means for rotating the spindle through predetermined angles of rotation, a table movable relative to the spindle transversely to said axis, a surface-sensing probe mounted on the spindle, means for generating a probe signal at the instant of said probe being brought into a sensing relationship with a surface defined on said table, means responsive to the occurrence of a said probe signal for producing an output corresponding to the position of said axis relative to a primary datum which is fixed in relation to the table, and a computer connected to read said output; the method comprising: (a) providing on the table a first and a second test surface having therebetween a mid-point defining a secondary datum, said mid-point having an actual position (CA) which may differ from a demanded position (CN), stored in the computer, by an error (WO); (b) operating the machine to bring the probe into sensing relationship with the first test surface and produce a first corresponding said output (A1); (c) operating the machine to rotate the spindle through 180°; (d) operating the machine to bring the probe into sensing relationship with the second test surface and produce a second said corresponding output (A2); (e) operating the machine to again bring the probe into sensing relationship with the first test surface, without having rotated said spindle after step (d) above and produce a third said corresponding output (B); and (f) operating the computer to read said outputs and determine the following values: WO=CN-(A1+A2)/2 PO1=(F-(A2-A1)/2, and PO2=A2+PO1-F-B wherein WO=said error, PO1=the distance between said spindle axis and the second test surface at the instant of said first output, PO2=the distance between said spindle axis and the first test surface at the instant of said second output, F=the known distance between the first and second test surfaces, and the position A2 is further from said primary datum than the position A1 and B.