Research On Machining Precision Of Micro Structure Milled By Microdiameter Ball End Milling Cutter

Micro structure is widely used in various fields.Because its feature scale is small,and the structure is complex.Geometric accuracy is usually high,and cutting tool is easy to be wear out,parts machining accuracy is difficult to achieve the requirements.Micro bevel andcurved surface is manufacturedby the micro diameter ball end milling cutter.The cutting tool diameteris very small andthe rigidity of the cutting toolis worse than the conventional cutting tools,andeasy to deform so as to cause the machining error.The ball end milling cutter is inclined to a certain angle in milling process,and the contact geometry of the workpiece and tool is different due to the different inclination angle,resulting in different speed and wear of the cutting edge,affecting the shape,position error and surface topography of the workpiece.In the paper the milling force modeling,machining dimension error prediction and influence of inclination angle on the geometric error,surface topographyabout the micro structure milled by ball end milling cutteris deeply studied.The main research contents and innovative achievements are as follows:1.Based on the factors such as the curvature radius of the workpiece,the tool inclination angle,and the phenomenon of tool eccentricity and single tooth cutting,the milling force model of micro ball end milling cutter is established.Firstly,the material properties and geometrical properties of micro ball end milling cutting tools are analyzed.Then the minimum cutting thickness,cutting tool eccentricity and single tooth cutting in the micro cutting process are discussed,and the motion trajectory model and the instantaeous cutting thickness model of the cutting edge point are established.The cutting angles of micro diameter cutting tool are analyzed,and the solving model of the cutting angle is established.Whether the cutting edge is engaged in cutting is discussed.According to the geometric characteristics of workpiece and cutting mechanism,micro milling force model is established,and on the basis,the whole ball milling force model is established by using analytic geometry,differential geometry,numerical method,solid modeling and so on.With the micro diameter ball end milling experiment carried out,the cutting force model is validated.2.Based on the geometric feature of the variable section of the micro ball end mill,the prediction model of machining error is established.The cutting load along the spiral line of the space is transformed into the concentrated load on the micro ball end milling cutting tool,and the equivalent action point of concentrated load is obtained.Based on the mechanical model of two segment and three segment cantilever beam,the prediction models of the workpiece machining error are established and verified.The experimental results show that the predicted values of the model are more consistent with the experimental results based on the three segment cantilever beam mechanics model.3.Influence of inclination,tilt angle and compound inclination angle of tools in visual cone range on shape precision and position precision is revealed.According to the change of tool position,the maximum cutting speed and the minimum cutting speed model of the cutting edge are established.Based on the micro milling force,the maximum and minimum cutting speed of the cutting edge,the influence of the angle on the shape and position accuracy is analyzed.The influence of different curvature radius on the geometric precision of the machined parts with the same angle is studied.4.The influence of different inclination of micro ball end milling cutter on the surface topography of micro structure is revealed.The forming process of the milling surface topography cut by the ball end milling cutter is described.The calculation model of the residual height is established,and the modeling and simulation of the convex and concave surfaces with different radius of curvature is made.The influence of the convex surface and concave curve with different radius of curvature on the residual height is discussed.Micro milling experimentswere carried out with inclination,tilt angle changing from-30°to 30°and compound inclination angle of tools in visual cone range.The influence of different inclination angles on the average height of Sa,the average deviation of Ra,the maximum height of Rz,the average width of the contour units Rsm is studied.The surface roughness is relatively poor when the angle is ±5°,so the processing under±5°is avoided.