Research On Spiral Bevel Gear Virtual Manufacture Theory And Algorithm

Processing and manufacturing of spiral bevel gears widely adopted computer-aided manufacturing systems for processing design, theoretical analysis, inspection, etc. The virtual manufacturing technology was combined with the manufacturing theory of spiral bevel gear combination to construct three-dimensional spiral bevel gear aided manufacturing platform and provide the support for CNC machine.A cutting simulation algorithm of spiral bevel gears was put forward to verify the movement in the CNC machine cutting process. The algorithm separated the cutting process into a series of discrete cutting movements. The cutting movement number was quantified by computing the amount of cutting blades. For any discrete movement, the algorithm interpreted the cutter blades and the spiral bevel gear as cones and layer circles respectively. So the data points on the gear tooth surface were generated by calculating the intersection points of the cones and circles. The algorithm adopted analytic calculation and was applied on the multiple cutting movements simulation of the spiral bevel gear. To improve the cutting simulation speed, the triangular patches stitched technology was put forward to display the cutting tooth surface, while the NURBS fitted surface are adopted to show the solid of spiral bevel gear.To achieve spiral bevel gear pairs’interference points or areas during the meshing movement, an interference check algorithm was put forward. Based on the gear parameters and points on the tooth surface, the algorithm established two kinds of gear models including a series of circles model and NUBRS one to describe the spiral bevel gear. In view of the complexity of NUBRS surface intersection and the characters of meshing movement, this problem was transferred into the intersection between the NUBRS tooth surface of pinion and a series of circles of gear. Meanwhile the intersection algorithm between the circle and NUBRS surface was proposed in the case of single or multi intersection areas.The simulation method was applied to analyze the meshing process of spiral bevel gear pairs. The gear and pinion were assembled with the assembly constraints. Based on the geometrical bodies’interference check, a contact point simulation algorithm of tooth contact was proposed to estimate the contact condition of tooth surface. The corresponding computer simulation program was developed to generate the instantaneous contact points, compute the transmission errors and describe the contact area.Based on the tilt generated cutting principle, a numerical algorithm of scallop height was put forward to control the cutting surface quality of spiral bevel gears. The cutting process was described as a series of non-continuous cutting movements of blades. The designed parameters of cutter blades and cutting process parameters were combined to build the mathematical tooth surface model. The mathematical model established the relationship among the scallop height, the blades number, the cutter rotational speed, the roll rate and the roll rotation angle. According to the mathematical model, scallop heights were computed by numerical algorithm and the influence of cutting process parameters was analyzed.The thesis is supported by national“863”project of china: precise and effective complete set manufacturing equipment for auto mobile spiral bevel gear and hypoid gear (No.2007AA042005).