Research On Tool Path Planning For Five-axis NC Machining Of Stone Engraving

With the rapid development of economy and people’s life greatly enriched and improved,people’s demand for stone carving products is also growing.And people have more requirements on aesthetic feeling of modeling and precision on stone carving products.Personalize customization and small batch production is an inevitable trend for the development.Stone relief modeling and NC machining technology have been widely concerned.Five-axis machining is often employed in the machining of parts with complex sculptured surfaces for improved accuracy and productivity.Owing to the two added rotational motions,five-axis machining offers higher material removal rate,better accessibility to the machined part surface,and higher surface quality over three-axis machining.However,the two rotational motions introduce critical challenges in tool gouging avoidance and optimal tool orientation determination in five-axis machining.In view of the above problems,in this thesis,a new method of tool orientation programming based on surface partitioning was proposed.Firstly,the geometric characteristics of complex surfaces were analyzed,according to the geometric characteristics of the surface and the curvature,the surface was divided into slices,and the surface was similar to a number of surface patches.Aiming at the problem of low efficiency of traditional single tool path for complex surface,a tool path planning strategy based on partition was proposed.For the region with small variation of the flat curvature,the tool path was generated by iso-parameter method,this thesis adopts the iso-scallop method,according to the different curvature tools with different radii,maximize processing space,and finally achieve the purpose of enhancing the efficiency of machining.The tool path was generated by using the iso-parametric method in the flat area.Tool orientation planning was used in normal processing method.In this method,the tool.orientation was in the same direction as that of the surface method.The method would get the maximum machining strip width.In view of the region with more severe curvature changes,iso-scallop method was adopted.The normal processing method was also adopted to the tool orientation programming.Considering the complexity surface could lead to the tool interference,the tool orientation needs to be further optimized.The specific method is to set a threshold value to measure the posture change rate of the adjacent cutter contact points.The change rate of the tool orientation can be obtained by calculating the difference between the adjacent tool orientations.If the vector change rate was smaller than the threshold value,the tool orientation change was in the allowable range.If the vector change rate is greater than the threshold value,then the vector wave is too large.For such cases,the tool orientation of accessible range can be calculated by using the free-interference algorithm,then a tool orientation that satisfies the threshold was selected in accessible range.In order to verify the effectiveness and practicability of the proposed method,the MATLAB programming software was used to simulate and analyze the change of the tool orientation of the non-partition surface,the partition surface and the partition optimization.Through the simulation experiment,the data of the tool orientation in three cases will be obtained,then vector difference curves of the three cases were drawn.Through the analysis of the curve graph,the method can smooth the cutter shaft,and improve the machining quality.