The Research On Interference Of Five Axis End Milling For Complex Surface Machining Based On Ring Milling Cutter

With the development of the Internet and the rise of the fourth industrial revolution,which takes information technology as the core,people have made increasingly higher demands on the performance and appearance of industrial products.Five-axis CNC machining has two rotational degrees of freedom compared to three-axis CNC machining,which makes the position of the tool can be continuously adjusted along with the machining surface when using five-axis machining,especially for machining turbine blades,marine propellers,and turbine runners of aircraft engines.There are great advantages in such complicated surfaces,but interference is easy to occur due to irregular irregularities in complex surfaces.Partial interference will cause the part to cut inaccurately and the machining errors.The global interference may cause the tool,the fixture and the workpiece to collide and damage the machine tool.Therefore,it is very meaningful to perform off-line interference detection and study the correction of tool position on the five-axis machining.In this paper,circular milling cutters will be used as machining tools to study the interference in the processing of complex curved surfaces around five axes.The main research contents are as follows:(1)First,calculate the Gaussian curvature and mean curvature of the processed surface at the tool contact,and then judge the neighborhood surface shape near the tool contact according to its positive and negative values.When it is determined as a convex surface,it is not necessary to perform curvature interference detection.If it is determined to be non-convex,it is necessary to compare the effective curvature of the annular milling cutter at the cutter contact,and to determine whether there is curvature interference in the curvature of the processed surface.(2)A tool projection bounding box method will be proposed for the interference detection of circular cutters,which the projection area is projected from the cutting surface of the annular cutter to the workpiece coordinate system,and the discrete points of the mesh on the parameter surface are determined tofall on the workpiece coordinate system.Under the projection area,the discrete points of the parametric surface grid are selected,and then the discrete grid points,which satisfying the conditions,are filtered and transformed to the tool coordinate system to perform the cutter bottom interference judgment and the corresponding tool position correction.(3)A two-grid subdivision method based on parametric surfaces will be proposed for the global interference of circular milling cutters.Firstly,the discrete mesh points in the bounding box of the ring milling cutter are screened,and the shortest distance from the discrete point to the knife axis segment that is satisfying all the conditions will be calculated,and the discrete points corresponding to the shortest distance from the knife axis segment are obtained.Finally,the discrete points of the surface are mesh-divided,the discrete points satisfying the precision are iterated and the shortest distance from the discrete point to the tool axis is determined,and the relationship between the distance and the tool radius is compared to determine whether there is a global interference or not.If there is a global interference,global interference avoidance will be performed and the tool position without interference will be obtained.(4)The VERICUT numerical control machining simulation software will be operated to simulate the five-axis end milled NURBS surface of circular cutter,which aims at simulating the feasibility of this algorithm.