Logarithmic spiral bevel gear is a complex curved surface shape. In order to ensure the accuracy of the collected data, some preparations should be made before collection.
(1) Calibration
Before measuring the logarithmic spiral bevel gear, the 3D family laser scanner should be calibrated. Because after a long time of practical use, the accuracy of the moving guide rail of the laser scanner decreases, and the hysteresis image will occur in the moving process, which affects the measurement accuracy. Therefore, before formal measurement, move the guide rail repeatedly to ensure smooth movement without affecting the measurement accuracy.
(2) Alignment of parts
The 3D family laser scanner system has its own machine coordinate system, and the distribution and quantity of data points are carried out in the workpiece coordinate system of CAD system. Therefore, before measurement, the position of CAD workpiece coordinate system in 3D family machine coordinate system must be determined, and the “3-2-1” method is usually used to align the logarithmic spiral bevel gear. That is, firstly, the calibration datum plane is determined through 3 points on the plane, and the datum axis is determined through 2 points. Finally, the origin of CAD workpiece coordinate system in 3D family machine coordinate system can be calculated through 1 point.
(3) Clamping of parts
The 3D family laser scanner is made of marble and equipped with a universal fixture V-groove. There are two ways to place the logarithmic spiral bevel gear in the V-groove: if the number of parts in the same batch is relatively large, a professional fixture must be made, so that the position where the workpiece in the same batch is placed is fixed, and there is no need to align it in the future; If the number of measuring parts is small, we can use naked eye observation to place the parts in a suitable position in the V-groove. Due to the small number of logarithmic spiral bevel gears we measure, our measurement accuracy can be met by visual observation.
(4) Data acquisition planning
The data acquisition process of logarithmic spiral bevel gear is efficient, and the acquisition results must be accurate. Accuracy refers to remembering that the data can truly reflect the structural characteristics of the part without generating scattered points. High efficiency refers to the reasonable planning of the measurement path, shortening the measurement path and reducing the time spent in the acquisition process. According to the actual structural characteristics of logarithmic spiral bevel gear, the acquisition method of self-use curved surface is adopted for scanning, the tooth surface with feature points is mainly scanned, and the feature point calibration method is adopted to collect the tooth surface of logarithmic spiral bevel gear.