Gear mechanism is the most widely used and important transmission mechanism in various mechanical equipment. In the reverse engineering design of gear, due to the complexity of gear tooth surface geometry, there are some technical difficulties in the reconstruction of gear three-dimensional model. It is worth studying to efficiently establish a gear model that meets the accuracy requirements.
There are many researches on the reverse engineering model reconstruction technology of gear in the past. The methods include the theoretical analysis of establishing a three-dimensional model of bevel gear through surface reconstruction based on the measured discrete point cloud data; There are also computer programming with the help of graphics processing software to realize the reverse model of spur gear, etc. To some extent, these methods show the technical achievements of reconstructing the gear model by reverse engineering, but there is no research on the reverse modeling strategy of bevel gear, and the precision of the reverse gear is insufficient.
Starting from the new perspective of creating a gear overall surface, we have studied the model reconstruction technology of the gear based on the technical route of physical reverse engineering, and finally realized the materialization of the gear (Fig. 1b). The modeling strategy is divided into two stages: firstly, the characteristic curve and each small surface patch are constructed in Imageware, and its error control function is used to adjust the control points and order of the surface, so as to reduce the difference between the surface and the original point cloud, and finally control the accuracy and smoothness of the required surface; Then, by constructing a large surface in Pro / E, the material other than the surface in the tooth tip circle solid is removed to realize the solid of the gear. This method of establishing gear three-dimensional model through surface reconstruction is efficient and convenient, and the fitting error can be controlled; Finally, the gear model obtained by removing the material is also in line with the characteristics of actual machining.
Using the basic steps of reverse engineering model reconstruction, the point cloud data of the gear is collected by the measuring equipment, and then the point cloud is preprocessed in the reverse engineering software to reconstruct the characteristic surface, analyze the surface fitting error, and adjust each fitting parameter to make it within the accuracy requirements, Finally, in the general CAD software, the digital model of gear can be established conveniently and quickly based on the created surface.
The research shows that: ① the digital model reconstruction of gear can be realized by reconstructing the characteristic surface of gear, and then removing the material substantiation from the perspective of machining; ② This work provides a new way for the exploration of reverse modeling of gear parts; ③ Based on the reconstructed model, the acquisition of gear parameters and the analysis of reverse precision and error are the contents to be further studied in the next step.