Research On Virtual Machining System For Indexing CAM

The virtual machining system for indexing cam can illustrate real machining environment and the cutting process of contour of indexing cam comprehensive and realistically. It can be used to check whether collision or interference will occur during machining process, to establish machinability and rationality of processing plan and to protect machining accuracy in design period. So, design can be improved as early as possible. The application of virtual machining system can make development time shorten, cost decreased. The technical level of indexing cam design and manufacturing will be upgraded.At the beginning of this dissertation, milling force model of indexing cam contour and machining methods have been developed. CNC machine tool, the architecture of virtual machining system, modelling of machining system and NC code translation have been researched.The development of the cutting force model for machining of gear indexing cam is based on the analysis of cutting edge expression and cutting force unit vector expression. Assuming the cutter to be divided into a number of differential elements in the axial direction of the cutter, the model is derived by summarizing the cutting forces produced by each differential cutter disc engaged in the cut. Cutting force equation is established by means of window function. The equation for calculating uncut chip thickness of differential disc is educed. The results of cutting force simulation can be summarized as follows: (1) As machining the section of cam contour which corresponds to the rotation of indexing plate, the rotation feeding speed increases to maximum value from zero, and then decreases to zero from maximum value, therefore, the maximum cutting area and maximum cutting force becomes greater and greater up to the highest level, and then become smaller and smaller down to the lowest level. (2) As machining the section of cam contour which corresponds to dwell of indexing plate, the rotation feeding speed is zero, so the maximum cutting area and maximum cutting force hold at a constant level. (3) As machining the left section and right section of cam contour which correspond to roller going into engagement and finishing engagement respectively, changing range of cutting area or cutting force is smaller than that as machining the middle section of contour. The maximum value of cutting force occurs in machining middle section of contour. (4) There are three component cutting forces, Fx is greater than Fz, and Fz is greater than Fy. (5) Cutting force will become smaller and smaller with the increasing of cutter's (spindle's) speed. Cutting force will become greater and greaterwith the increasing of workpiece feeding speed or the increasing of axial cutting depth.The coefficient of cutting force is derived based on the analysis of machining process of barrel indexing cam contour. The simulation results of milling force in the machining of barrel indexing cam indicate that as follows: (1) As machining the sections of cam contour which correspond to the rotation of indexing plate, cutting area and cutting force are such greater than those corresponding to dwell position of indexing plate. (2) As machining the section of cam contour which corresponds to dwell of indexing plate, the maximum cutting area and maximum cutting force hold at a constant level. (3) As machining the left section and right section of cam contour which correspond to roller going into engagement and finishing engagement respectively, cutting area and cutting force are pulse function, and their maximum values increase rapidly. (4) There are three component cutting forces, Fy is greater than Fx, and Fxis greater than Fz.NC machining method of gear indexing cam with smaller diameter cutter is developed. NC program coordinate equation is derived based on the theory of isometric curve surface and the research of swept surface of roller axis according to engagement of roller and cam contour. The software framework for computer aided NC programming and practical machining example are illustrated.The appr...