Simulation And Experimental Study On Surface Topography And Cutting Force In Ball End Milling

Ball end milling cutter is widely used in the machining field of complex surface parts because of its edge characteristics.However,the machining process of these parts is more complex,except that,the processing quality and efficiency often restrict each other.For these reasons,the traditional method which selects process parameters by trial-machining is difficult to meet the needs of modern enterprise production.Now the progress of computer and simulation technology supports an approach to high quality and efficient production.Surface quality and cutting force can be predicted by means of machining simulation,thereby the influence on surface quality of different processing parameters combination can be analyzed,and then,the reasonable parameters can be selected.Therefore,it is of great theoretical and practical value to study the cutting mechanism of ball end milling and build accurate prediction models that include surface quality and cutting force.Focusing on the modeling and simulation of surface topography,firstly,the formation mechanism of surface topography in ball end milling is studied.Then the sweeping motion of the cutting edge is expressed by establishing the milling motion coordinate system and using the method of transformation matrix.Finally,the simulation model of milling surface topography based on the geometric motion of cutter is established.These factors influencing surface topography,such as rotational speed,feed speed,tool parameters,machining inclination angle and cutter runout are considered in this model.Moreover,an improved Z-map simulation algorithm is proposed to overcome the shortcomings of common topography simulation algorithms in this paper.The algorithm improves the simulation efficiency while ensuring the calculation accuracy by introducing genetic algorithm to solve the non-linear equations.For the topography simulation in end milling free form surfaces,a retrieval algorithm of tool location is proposed to match the cutting time to the tool location,thus the difficult problem of topography simulation in milling complex surfaces is solved.The influence of milling force on surface quality can not be neglected either.Considering that,a micro-element milling force model is established.Besides the influence mechanism of runout on chip thickness is emphatically analyzed,a calculation method of cutter runout is also deduced theoretically in this model.Moreover,the influence of milling force on the surface topography is discussed,and the simulation model considering tool deformation is built.A series of cutting experiments using ball end milling cutter are designed to validate the correctness of milling force model.The comparison between simulation and experiment results show that the model proposed can accurately predict the milling force after introducing cutter runout.In order to verify the correctness of simulation model of surface topography,a series of cutting experiments of aluminium alloy parts are designed,then the roughness and geometric topography of milling surfaces are measured.After that,the similarities and differences between the height characteristics and the regional distribution characteristics of the measured and simulated topography are compared and analyzed.The results show that the proposed simulation model of surface topography can reasonably and effectively predict the roughness and texture of milling surfaces.Based on the simulation model of surface topography,the effects and mechanism of these influencing factors which include feed rate,path interval,tool radius,machining inclination angle,cutter runout and feed mode on the 3D surface roughness and surface texture characteristics are researched respectively.Besides that,the selection principles of each parameter are also given in this paper.