Research On The Efficient Virtual Measurement Technology For Globoidal Cam Machining Error

The actuating mechanism with globoidal cam as the core pieces has the advantages of high precision, heavy load torque, compact structure, long service life, which has been widely used in the automation machinery. Presently, the CNC machining method is the main machining method for globoidal cam at home and abroad ,and this greatly improves the machining precision and efficiency. Compared with abroad, there is still a large gap in the wheeled actuating mechanism of the globoidal cam, and the market share is still very low. The main cause is that the working profile of globoidal cam as a skew helical surface,its machining and measurement heavily rely on some expensive equipments such as precise CNC machining center, Coordinate Measuring Machines(CMMs), the manufacturing level and measuring methods are unsound and the overall level are fairly backward at home. Thus it severely restricts the precision-efficient development and application of globoidal cam at home. How to reduce the severe dependence of the CMMs, achieve the efficient and low-cost measurement for the machining error of globoidal cam is an important issue in the machining of globoidal cam mechanism. Therefore, it is urgent necessary to develop an efficient virtual measuring technique for the profile machining error of the globoidal cam to cover the shortage of complex surfaces measurement by three-coordinates measuring machine. Therefore, based on the virtual measuring principle and the meshing theory of the globoidal cam, this paper has explored a virtual measurement method and model for the machining error of the globoidal cam with the help of UG and its development tools, VC++ , etc, and developed some virtual measurement software, analyzed some examples. Specific studies are as follows:1) Review the development of the CNC machining technology of the globoidal cam, the measuring technology for CNC machining errors and virtual measuring technology. Then, analyze the developing trend of the virtual measurement technology in CNC machining technology of the globoidal cam. Finally, the profile equation of the globoidal cam is derived according to the meshing theory and the basis is established for the subsequent study.2) Based on the virtual measuring principle and taking the CNC machining simulation model as the virtual measure object, the virtual measuring method for machining error of globoidal cam has been proposed. The discrete position of the virtual gauge head is planed by the theoretical profile equation of globoidal cam and the geometry relationship between the gauge head and the measured surface is judged by the geometric interference function, and finally solving the processing error by the interference level. 3) According to the virtual measuring model, the virtual measuring software is developed by UG secondary development tools and VC++ based on UG platform. Then, the measurement trace of globoidal cam's virtual gauge head is verified by VERCUT. This measuring software achieves seamless integration with the UG platform which provides an effective CAD/CAM/CAT platform for the virtual design, virtual manufacturing and virtual measurement of the globoidal cam.4) Based on the above research, the example analysis is done. The machining simulation models processed by the generating method and the one-side milling method are separately measured by the virtual measurement software, and the actual value of virtual measurement is consistent with the theoretical predication value. Thus it reflect the proposed method is correct, the established model is effective and the developed software is credibleTo sum up, this paper not only provides some effective solutions to achieve efficient and low-cost measurement for the processing error of globoidal cam, but also lays the theoretical foundation to expand the application of the virtual measurement technology in the processing of complex surface.