Optimization Of Rough Machining In Multi-axis CNC Based On 3D Entity Model

Rough machining is an important stage in the production process of stone products.To improve the efficiency of 3D rough machining of stone material,making full use of multi-axis NC machining technology and the advantage of diamond circular sawblade.The 3D entity description of special shaped stone for rough machining was based on the diamond circular sawblade and the five axis NC machining.The research included workpiece modeling,the strategy of material removal,the rough machining processing time optimization,five axis of circular sawblade cutting simulation system ect.Firstly,the method to obtaining the data information of the 3D entity described in the STL graphic exchange file was proposed.the geometric characteristics and processing modes of circular sawblade,the stone removal mechanism were studied.According to the characteristics of block sawing method,a workpiece model based on boundary representation was proposed,and its data structure was established,which is used to improve the speed of the intersection between the tool and the workpiece.Secondly,on the basis of analyzing the traditional cutting method of circular saw blade,according to the relationship between material removal depth and material removal amount,combined with the characteristics of large cutting depth of circular saw blade,the planning strategy of removing rough processed 3D stone material was put forward.For the material removal planning of convex shaped stone,the strategy was based on the workpiece vertex and the 3D shaped machining target surface contour point,the characteristic workpiece vertexes and the characteristic cutting point corresponding to the material removal maximum depth were searched,and the octree algorithm was used to improve the search efficiency.According to the characteristic workpiece vertexes and the characteristic cutting point,a sawing reference plane was constructed to determine the circular sawblade’s attitude.In this strategy,a binary space segmentation algorithm was used to judge the removal vertexes of the workpiece in the process of sawing.The spatial geometric characteristics of the workpiece removal body was analyzed,and the volume calculation formula of the spatial convex polyhedron was used to calculate the material removal amount of each sawing.For the removal planning of sawing rough processing materials for complex concave shaped stone materials,the processing target model is simplified with the idea of concave convex,the corresponding convex polyhedron algorithm was proposed for model simplification,and the corresponding sawing reference plane planning was given.Then,based on the processing of circular sawblade along the sawing reference plane,the cutting time model was established.through analyzing of the spatial geometry of the polygon of the sawing intersection,the definition of the minimum span of 3D convex polygon was proposed,and the optimal sawing feeding direction and the shortest sawing feeding stroke are determined.Combined with the one-cutting-fits-all machining mode,a method for generating the shortest cutting path was proposed.Finally,the model for BC rotary five axis CNC machine was established in Vericut software,according to the structure characteristics of the machine’s model and cutting path,through the machine kinematics transforming cutting path which contains APT data into NC code.In view of the problem that the material removal part of the workpiece could not peel off after sawing in Vericut,a method of generating the path of sawing back along the reference plane’s normal was proposed to realize the display of the block sawing in Vericut.Through the simulation processing of typical stone products roadblock ball,the simulation results of the planning layer in MATLAB and the sawing processing results of the implementation layer in Vericut were compared to verify the efficiency and practicability of the proposed rough material removal strategy.