Geometric error identification method of multi-axis machine tool and multi-axis machine tool

A geometric error identification method of a multi-axis machine comprising a main spindle and a table, the method comprising:

• rotating one of a main spindle and a table to a plurality of indexed angular positions, the main spindle configured to mount a tool thereon, the table configured to retain a workpiece thereon, the main spindle and the table configured to be moved, based on signals from a control device, relative to each other along at least a first translation axis and a second translation axis, and with respect to at least a first rotation axis, so that the workpiece is machined with the tool, a jig mounted on said one of the main spindle and the table;
• measuring respective positions of the jig at said indexed angular positions using a position measuring sensor mounted on the other one of the main spindle and the table to obtain a plurality of measured positions of the jig at respective indexed angular positions;
• calculating any translational error in the position of the first translation axis from the plurality of measured positions of the jig;
• calculating any translational error in the position of the second translation axis from the plurality of measured positions of the jig;
• calculating any inclination error in the first rotation axis from the plurality of measured positions of the jig;
• calculating an ellipse approximate expression approximating an arc trajectory derived from the plurality of measured positions of the jig;
• and
• calculating and correcting any scaling error of the first translation axis and any scaling error of the second translation axis from the calculated ellipse approximate expression.