In order to obtain the actual coordinate points of the hourglass worm tooth surface, the coordinate machine or gear measuring center can be used to measure it. Because the gear measuring center has a rotating c-axis, it has more flexibility in the measurement of hourglass worm. The measurement diagram is shown in the figure.

According to the figure, the scanning function of gear measuring center is used to collect the data of hourglass worm tooth surface

(1) the hourglass worm is located radially by the upper and lower centers of the gear measuring center through the center holes at both ends.

(2) the probe is located at the reference position (1), the corresponding Z value is measured, and the axial positioning is carried out through the distance conversion of the reference relative to the throat center in the processing process.

(3) place the probe on the YOZ plane, that is, the x-axis coordinate is 0 and lock the x-axis.

(4) lock the c-axis coordinate, scan with the contour scanning function, move one axial tooth profile of the scanning hourglass worm along the – Z direction, and the probe moves to position ② in the scanning process.

(5) the c-axis rotates at a certain angle θ C, and repeat step (4) to complete another axial tooth profile measurement. If the accuracy of tooth surface measurement needs to be improved, turn the angle θ C may be smaller.

(6) repeat step (5) to measure a series of axial tooth profiles until the whole hourglass worm tooth surface is measured.

Because the three-dimensional probe is used to compensate the probe radius, the data obtained is the actual data of hourglass worm tooth surface. Select a set of data as the benchmark, through the corner θ The actual coordinate values (XC, YC, ZC) of the toroidal worm tooth surface in the measuring coordinate system can be obtained by selecting coordinate transformation. The radial positioning and axial positioning between the coordinate system and the theoretical coordinate system of hourglass worm tooth surface have been carried out by the above steps (1) and (2), and the circumferential positioning is determined by the least square matching between the measured data and the theoretical data.