Study On Wear Characteristics Of Left And Right Cutting Edges And Their Flank Faces In Turning Large Pitch Internal Thread

Large pitch internal thread who can transmit torque and accuracy is the key part in heavy-duty press machines,nuclear power and other manufacturing equipment.The machining quality consistency of left and right thread surfaces affects the performance of heavy equipment seriously.In turning large pitch thread,the features of process scheme are low speed,large cutting depth and feeding.There is obviously different wear on the left and right cutting edges.This different wear greatly restricts the machining efficiency of turning large pitch thread.It has become a key problem to be solved.Under the support of scientific and technological projects in Heilongjiang Province,named as “Efficient cutting technology of high-quality large pitch thread”(GC13A404)and National Natural Science Foundation of China,named as "Based on the generalized dynamic space of high feed cutting tool vibration wear mechanism"(51575148),aiming at the need of high efficiency and precision in turning press nuts,this paper presents the methods to characterize the change of cutting edges and the different wear between left and right flank faces.The changes of the cutting edges and distribution of flank wear with the cutting stroke are revealed.The tool performance test method is given and the process design method of tool life in turning trapezoidal internal thread is proposed.The experiment of turning large pitch thread is carried out by axial stratified cutting method.During the experiment,the left and right cutting edges work with equal cutting strokes and parameters.The force equations of left and right cutting edges are used to reveal the difference of forces acting on tool when turning left and right thread surfaces.Applying equidistant measuring method along cutting edge,the characteristic parameters of cutting edges are extracted.The distribution functions of edge radius and plastic deformation widths on cutting edges are constructed to reveal and reflect the change characteristics of edge radius and plastic deformation,which provides the basis for studying the wear mechanism of abrasive wear and plastic deformation on cutting edges and controlling the tool life effectively.Applying equidistant measuring method along cutting edge,the wear characteristics are extracted and analyzed from the diagram of wear condition on left and right flank faces.By polynomial fitting with two unknowns and high power,the distribution functions of wear widths on flank faces are constructed to study the different wear between left and right cutting edges.It can be used to obtain the following evaluation indexes: the maximum wear width and its position,the maximum wear rate and its position,and wear rates at different positions on cutting edges.These evaluation indexes can reveal the forming process of wear on flank faces,and show that the distribution characteristics of wear widths on left and right flank faces along the length direction of cutting edge change with cutting stroke.Finally,a method for characterizing the different wear between left and right flank faces is proposed.In turning large pitch internal thread,the wear widths on left and right flank faces are regarded as wear characteristic parameters.The datum of wear widths which are extracted through 10 times measure on left and right flank faces are used in establishing reference sequence.The effective values and kurtosis of tool accelerated speed vibration signal in radial cutting depth,cutting speed and axial feed directions are regarded as vibration characteristic parameters.The effective values and kurtosis are extracted to established comparative sequence in the last axial stratified turning before the wear measurement.Adopting the relational analysis algorithm modified,the reference sequence is compared positive and negative correlation with comparative sequence.Grey incidence matrix of wear widths and vibration characteristic parameters on different position of flank face along cutting edge.The relations between vibration energy,signal shock and wear widths of flank face are revealed in cutting,meanwhile,the influence mechanism which tool vibration affects service life is expounded.By the comparative experiment of turning trapezoidal internal thread,the influence of cutting edge shape on tool life and machining surface quality was obtained.Based on the machined surface roughness of left and right thread surfaces,the detection method of tool wear and service life and the test method of cutting performance are proposed.Then the service life and residual life of tool are calculated.In order to improve the cutting efficiency and ensure the overall tool life and the quality of the surface,the process design method of tool life in turning trapezoidal internal thread is proposed.