Application Notes AP-1116 Calibration of a 5-axis machine by volumetric positioning and tool tip positioning measurement I. What is the problem II. How to solve this problem First, using the laser vector method [1] to calibrate and compensate the volumetric positioning errors including the 3 displacement errors, 6 straightness errors and 3 squareness errors. Second, using the non-contact laser spindle professional tester [2] to measure the tool tip displacement errors at various rotational angles. This measurement can be used to calibrate or to compensate the angular errors of the 2 rotational axes. Finally, to measure the tool tip positioning errors dynamically at various tool paths and geometries. IV. Positioning of a 5-axis machine The machine coordinate is defined as (Xm, Ym, Zm, A, B). The center of rotation of A and B is defined as (Xp, Yp, Zp). The tool tip position is defined as (Xt, Yt, Zt). The relations Xp = Xm + Cx, Yp = Ym + Cy, Zp = Zm + Cz , where Cx, Cy, and Cz are constants. III. How it works For a 5-axis system tool it is very important to calibrate both the volumetric positioning (X, Y, Z) and the two rotational axes, A and B or A and C. Using a laser interferometer to calibrate the 3 linear axes and the 2 rotational axes separately and independent of each other is not enough. There are straightness errors for each of the 3 linear axes, and squareness errors between the 3 linear axes, skew, Non-orthogonal and non-intersection of the 2 rotational axes, and the non-intersection of the center lines of the spindle and the z-axis. Hence it is important to measure the volumetric positioning (X, Y, Z) by the laser vector method and the tool tip positioning (A, B, and R) by the tool tip positioning measurement. The laser vector method is described in Ap-1109 and the spindle tester is described in Ap-1114. After calibrating and compensating the volumetric positioning accuracy by the laser vector method, mount the spindle tester with a precision sphere to the spindle and mount the laser head at position 2 as shown in Fig. 1. Align the laser beam with a focus lens to be focused at and perpendicular to the surface of the precision sphere as shown in Fig. 2. Move the 5 axes such that the center of the tool tip, represented by the center of the precision sphere, is at a fixed position. Measuring the changes of the tool tip positions due to various movements, the angular errors of A and B at various angles can be determined.