Design And Processing Of The Helical Surface And The Key Technology Of Cad,

Conjugate surface is one kind of surfaces which have been used widely in the field of mechanical engineering. Since it features high transmission accuracy and good load-carrying performance, it is used in the design and manufacture of driving medium, graduator etc. The common conjugate surface includes tooth surface of gear, working surface of solid cam, helicoidal surfaces existing in spiral burr, worm, chip flute of cutters, and so on. Therefore, the research on the design and manufacture of conjugate surface has become an important part in the field of machine manufacture. Because of the complexity and manifoldness of conjugate surface, this paper only pivots on the helicoidal surface.The helicoidal surfaces are produced mostly by form cutting with forming cutters of end mill type, side mill type or disc type. The following items in design and manufacture of helicoidal surfaces should be taken into consideration: the design of profile of forming cutter, verification of profile of form and modification of installation parameter of disc cutters. The traditional designing method includes graphing method and analytical method. Graphing method is illustrative, but of low precision. Analytical method is of high precision, but of complicated process. Especially, both are of low adaptability and make high demand on designer's mathematical and special knowledge.With the development of the manufacture technology, the traditional design procedures of helicoidal surface can't meet the need of modern industry, and morever, manual calculation impedes the improvement of the manufacture of helicoidal surface. Therefore, it becomes very important and urgent to explore new method and automatize the design of helicoidal surfaces. The rapid development of the technology of computer and graph manipulation lays solid foundation for the application of numerical method and graphing method based on solid model.By retrieval of scientific and technological information, it is shown that technicians pay much attention to computer in the process of design and manufacture of helicoidal surface. Technicians are exploring various design procedures, specially in the field of the solid model of helicoidal surfaces, the design of profile of forming cutters for the machining of helicoidal surfaces and computer simulation and verification.On the basis of traditional design theory and method, this paper presents some new methods by taking the advantage of computer in numerical calculation, solid model and drawing. These new methods include CAD of forming cutters for helical surfaces, verification of profile of forming cutter and interference between cutters and workpiece, CAD of installation parameter of disc forming cutter. A thorough study has been made on the key theories and relative technical matters.Firstly, on the premise of ensuring the accuracy, this paper presents a practical and efficient method of CAD of forming cutters for helicoidal surface. For the generation of profile of forming cutter, the new method is divided into five steps, namely, solid model of helicoidal surface based on given end section or axial section of workpiece, extracting available information in the effective section, obtaining contact point in every effective sections, fitting line of engagement between forming cutter and workpiece and profile of forming cutter using NURBS curve, manual intervention which is helpful in the improvement of the local precision of profile of forming cutter. In section 1, in accordance with the generation of helicoidal surface and Boolean operation, this paper presents a approximate method to model helicoidal surface and creates a mathematical model. Because solid model of helicoidal surface is approximate, the section curve of workpiece obtained in available section is also approximate. In order to improve the accuracy of section curve, a method to extract available points is described in section 2. Contact point is a bridge between profile of forming cutter and end section or axial section of workpiece. In section 3,...