Research On Three-NURBS Precision And Smooth Interpolation Method For Five-axis Machining Of Linear Micro Toolpaths

With the increasing application of complex free-form surface in various fields related to industry,the machining of complex surface by five-axis NC machine tool has attracted extensive attention.Thanks to the good properties of NURBS(non-uniform Rational B-splines)curves in mathematics and algorithms,NURBS curves have been greatly popularized in the field of NUMERICAL control machining.But compared with the numerical control machining technology of foreign developed countries,the numerical control machining technology of Our country is still in the backward stage.Therefore,the continuous development of NUMERICAL control machine tools with NURBS curve machining function has important practical significance for improving the overall level of China's manufacturing industry at this stage.In view of the above practical problems,this paper carries out the research work of three NURBS smoothing interpolation technology under the condition of guaranteeing the interpolation accuracy of five-axis machining linear micro tool path.The main research content of this project is divided into the following two parts:(1)The interpolation method of NURBS curves is studied.A NURBS curve interpolation method based on curvature adaptively selecting feature points was proposed for the mass discrete tool position data generated in the nc programming processing stage,and the interpolation accuracy was satisfied.Firstly,the curvature of each discrete data point is calculated,and feature data points such as piecewise points and curvature maximum points are selected based on the curvature information.Then the initial NURBS interpolation curve is constructed and the interpolation error is calculated.Secondly,in the curvature segment beyond the preset interpolation error,new feature points are added and new NURBS interpolation curves are generated.The above process is repeated until all data points not on the NURBS interpolation curve meet the interpolation accuracy conditions.Finally,MATLAB is used for simulation verification of actual data.The results show that the method proposed in this paper can better retain the features of the original data curve in terms of shape and accuracy even when removing a large number of original tool position data.(2)The three NURBS finishing interpolation method is studied.Firstly,a coordinated data processing method for three spline curves at the same time is proposed for the case that a set of data points can be compressed and spline interpolation can be carried out accurately.Secondly,in order to better deal with the precision of the cutting contact path between the cutter and the surface of the part,this paper constructed a tool path with three NURBS curves including cutter contacts on the basis of the existing double NURBS spline machining trajectory,and proposed a three-nur BS finishing interpolation method for five-axis machining based on dual quaternion method.In this method,the tool path smoothing interpolation is studied from the Angle of dual quaternion,and the node vector is calculated by using dual quaternion method.After that,the NURBS curves of the tool center point,the tool axis point and the tool contact are constructed by interpolation,and the tool path of three NURBS smoothing interpolation above~1G is finally obtained to meet the error accuracy requirements.Simulation experiments were carried out with the help of MATLAB,and the results showed that the proposed method had significant advantages over the existing linear interpolation methods in terms of the degree of tool path smoothing and the compression amount of tool number points,proving the effectiveness of the proposed method in the aspect of three NURBS smoothing interpolation.