Study On Topography Simulation Of High Speed NC Machined Surfaces

The application of free-form surfaces increase sharply in the modern die & mould industry. The inner configuration and outer shape design of moulded parts become more and more complicated, furthermore higher accuracy and surface quality are demanded. All these bring forward higher requirements to the die & mould manufacturing. Therefore, the investigation on surface topography simulation for free-form surface machining is of great significance theoretically and practically to die & mould manufacturing. By means of the modeling for ball-end mill, NUBRS free-form surface as well as cutting forces prediction, an efficient algorithm of the surface topography simulation for high speed machining is presented. The topography of the high speed machined surfaces are simulated, which are verified experimentally.The simplified geometrical models of solid and indexable ball-end mills are constructed by employing analytic geometry principles, and the equations of cutting edges are given. Based on the chip formation mechanism and differential geometry principles, the predictive model of cutting forces is established. Based on the cantilever beam theory and the Hooke' law, the formula of tool deflection is derived. The movement trajectory equation of any point on the cutting edge is obtained via the graphic matrix transformation algorithm, consequently the moving enveloped surface of the tool is obtained, which is then modified by taking into account the tool runout and deflection. By extending the Z-map algorithm to the surface topography simulation of NUBRS free-form surface machining, the topography simulation is conducted via Boolean computation, in which Matlab language is used in the programming and an open modular structure is adopted in simulation program.High speed milling of P20 steel with solid carbide ball-end mill is performed on CNC machining center, the dynamic cutting force curves and topography of work-piece are obtained, which confirmed the validity of the cutting force model and free-form surface topography simulation model proposed in the thesis.