CN113927368B - Edge wear monitoring method of micro milling cutter based on inflection point identification of cutting force coefficient curve - Google Patents

Abstract

The invention relates to a micro milling cutter cutting edge wear monitoring method based on cutting force coefficient curve inflection point identification, which comprises the following steps: s1, collecting cutting force and cutting track profile of a micro milling cutter; s2, calculating a cutting force coefficient according to the cutting force, and calculating the undeformed cutting thickness according to the cutting track profile; s3, drawing a scatter diagram of the undeformed cutting thickness-cutting force coefficient; and S4, fitting the scatter diagram by adopting a logistic regression function, calculating a fitting curve inflection point, and representing the blunt radius of the cutting edge. According to the invention, the cutting force coefficient and the undeformed cutting thickness are respectively calculated through the collected cutting force and cutting track profile, a scatter plot relation graph of the undeformed cutting thickness and the cutting force coefficient is established, the curve inflection point of the relationship between the undeformed cutting thickness and the cutting force coefficient is determined through curve fitting, finally, the worn blunt radius of the cutting edge of the micro-milling cutter is represented by the curve inflection point, and the wear of the cutting edge of the micro-milling cutter is monitored.

Description

Edge wear monitoring method of micro milling cutter based on inflection point identification of cutting force coefficient curve

technical field

The invention relates to the technical field of micro milling cutter edge wear monitoring, in particular to a micro milling cutter edge wear monitoring method based on the identification of the inflection point of the cutting force coefficient curve.

Background technique

Micro-milling has high processing precision, diverse processing materials and the ability to process complex three-dimensional curved surfaces. It has broad application prospects in the fields of biomedicine and microelectronics. As the core component of the micro-milling process, the micro-milling cutter performs discontinuous cutting at an ultra-high speed and wears very quickly. In order to ensure machining accuracy and prevent tool breakage and workpiece and machine tool damage caused by excessive wear, online monitoring of micro milling cutter wear is necessary. Among various wear indicators, edge wear directly determines the cutting performance of micro-milling such as chip thickness, machining accuracy and stability. Realizing the monitoring of edge wear has important theoretical significance and application value.

The existing micro-milling cutter wear monitoring is mainly based on the tool face wear monitoring, and the monitoring of the micro-milling cutter edge wear cannot be realized.

Contents of the invention

For this reason, the technical problem to be solved by the present invention is to overcome the inability to realize the monitoring of the edge wear of the micro-milling cutter in the prior art, and provide a method of identifying and monitoring the edge wear of the micro-milling cutter by identifying the inflection point of the relationship curve between the undeformed cutting thickness and the cutting force coefficient. method, the method calculates the cutting force coefficient and the undeformed cutting thickness respectively through the collected cutting force and the cutting track profile, establishes the scatter relationship diagram between the undeformed cutting thickness and the cutting force coefficient, and then determines the undeformed cutting thickness by curve fitting -The inflection point of the cutting force coefficient relationship curve, and finally the inflection point of the curve is used to represent the blunt circle radius of the worn micro-milling cutter edge, and monitor the wear of the micro-milling cutter edge.

In order to solve the above technical problems, the present invention provides a micro milling cutter edge wear monitoring method based on the identification of the inflection point of the cutting force coefficient curve, comprising the following steps:

S1, collecting the cutting force and cutting track profile of the micro milling cutter;

S2. Calculate the cutting force coefficient according to the cutting force, and calculate the undeformed cutting thickness according to the cutting track profile;

S3, drawing undeformed cutting thickness-cutting force coefficient scatter diagram;

S4. Fitting the scatter diagram with a logistic regression function, calculating the inflection point of the fitting curve, and characterizing the radius of the blunt circle of the cutting edge.

F_i ^y，

In one embodiment of the present invention, in step S1, the collection process of cutting force includes: collecting the feed and normal four cutting forces at every two adjacent reference tooth position angles θ _i and θ _i+1 value F _i ^x ,

F _i ^y ,

F_i ^y，

计算得到径向切削力系数和切向切削力系数。In one embodiment of the present invention, in step S2, according to the values F _i ^x of the four cutting forces in the feed and normal directions,

F _i ^y ,

Calculate the radial cutting force coefficient and tangential cutting force coefficient.

F_i ^y，

计算参考齿位角θ_i处的削切力系数。In one embodiment of the present invention, the calculation process of the cutting force coefficient includes: calculating the coefficient matrix according to the undeformed cutting thickness and the axial depth of cut, combining the coefficient matrix and the values F _i ^x of the four cutting forces in the feed and normal directions,

F _i ^y ,

Calculate the cutting force coefficient at the reference tooth position angle θ _i .

In one embodiment of the present invention, in step S3, the undeformed cutting thickness is used as the abscissa, and the radial cutting force coefficient and the tangential cutting force coefficient are respectively used as the ordinate to plot the undeformed cutting thickness-radial cutting force coefficient and Scatter plot of undeformed cutting thickness versus tangential cutting force coefficient.

In one embodiment of the present invention, in step S4, the scatter plots of undeformed cutting thickness-radial cutting force coefficient and undeformed cutting thickness-tangential cutting force coefficient are respectively fitted using logistic regression function, and two simulated The inflection point of the fitting curve, calculate the average value of the inflection points of the two fitting curves, and characterize the radius of the blunt circle of the cutting edge.

In one embodiment of the present invention, in step S1, the collection process of the cutting track profile includes: collecting the maximum profile width radius and the minimum profile width radius of the cutting track, and determining the radial runout length r _o and the angle γ _o .

In one embodiment of the present invention, in step S2, the undeformed cutting thickness is calculated according to the radial runout parameter and the feed rate per tooth.

In one embodiment of the present invention, in step S1, the sampling frequency is set according to the spindle speed, and the cutting force of the micro-milling cutter is collected to ensure that the spindle rotates once for one sampling.

In one embodiment of the present invention, in step S1, a force sensor is set to collect the cutting force, and an image collection device is set to collect the contour of the cutting track.

The above technical solution of the present invention has the following advantages compared with the prior art:

According to the micro-milling cutter edge wear monitoring method based on the inflection point recognition of the cutting force coefficient curve of the present invention, the cutting force and cutting track profile are collected, the cutting force coefficient and the undeformed cutting thickness are calculated respectively, and the undeformed cutting thickness and cutting force are established. Coefficient scatter diagram, and then determine the inflection point of the undeformed cutting thickness-cutting force coefficient relationship curve by curve fitting, and finally use the inflection point of the curve to represent the blunt circle radius of the worn micro-milling cutter edge, and monitor the wear of the micro-milling cutter edge. Realizing the monitoring of micro-milling cutter edge wear plays an important role in improving the precision of micro-milling, and effectively prevents a series of adverse consequences such as tool breakage, vibration, workpiece and machine tool damage caused by excessive wear of the micro-milling process, and improves Micro-milling processing efficiency, reduce production costs.

Description of drawings

In order to make the content of the present invention more easily understood, the present invention will be described in further detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein

Fig. 1 is the flow chart of the steps of the micro milling cutter edge wear monitoring method based on the inflection point identification of the cutting force coefficient curve in the present invention;

Fig. 2 is a fitting curve diagram of undeformed cutting thickness-cutting force coefficient of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and implement it, but the examples given are not intended to limit the present invention.

With reference to shown in Fig. 1, a kind of micro milling cutter edge wear monitoring method based on cutting force coefficient curve inflection point identification of the present invention comprises the following steps:

S1, collecting the cutting force and cutting track profile of the micro milling cutter;

S2. Calculate the cutting force coefficient according to the cutting force, and calculate the undeformed cutting thickness according to the cutting track profile;

S3, drawing undeformed cutting thickness-cutting force coefficient scatter diagram;

S4, using the logistic regression function to fit the scatter plot, calculating the inflection point of the fitting curve, and characterizing the radius of the blunt circle of the cutting edge;

The cutting edge wear monitoring method of the micro milling cutter based on the inflection point recognition of the cutting force coefficient curve in this embodiment calculates the cutting force coefficient and the undeformed cutting thickness respectively through the collected cutting force and the cutting track profile, and establishes the undeformed cutting thickness and cutting force Coefficient scatter diagram, and then determine the inflection point of the undeformed cutting thickness-cutting force coefficient relationship curve by curve fitting, and finally use the inflection point of the curve to represent the blunt circle radius of the worn micro-milling cutter edge, and monitor the wear of the micro-milling cutter edge. Realizing the monitoring of micro-milling cutter edge wear plays an important role in improving the precision of micro-milling, and effectively prevents a series of adverse consequences such as tool breakage, vibration, workpiece and machine tool damage caused by excessive wear of the micro-milling process, and improves Micro-milling processing efficiency, reduce production costs.

F_i ^y，

设置力传感器采集切削力，并且，根据主轴转速设置采样频率，采集微铣刀切削力，保证主轴旋转一度进行一次采样。Specifically, the cutting force collection process includes: collecting the feed and normal four cutting force values F _i ^x at every two adjacent reference tooth position angles θ _i and θ _i+1 ,

F _i ^y ,

Set the force sensor to collect the cutting force, and set the sampling frequency according to the spindle speed to collect the cutting force of the micro-milling cutter to ensure that the spindle rotates once for one sampling.

F_i ^y，

计算得到径向切削力系数和切向切削力系数；具体地，切削力系数的计算过程包括：根据未变形切削厚度和轴向切削深度计算系数矩阵A_i：In this embodiment, according to the values F _i ^x of the four cutting forces in the feed and normal directions,

F _i ^y ,

Calculate the radial cutting force coefficient and the tangential cutting force coefficient; specifically, the calculation process of the cutting force coefficient includes: calculating the coefficient matrix A _i according to the undeformed cutting thickness and the axial cutting depth:

为参考齿位角为θ_i时，轴深z处第k切削刃的齿位角，M为刀齿个数；in

is the tooth position angle of the kth cutting edge at the shaft depth z when the reference tooth position angle is θ _i , and M is the number of cutter teeth;

F_i ^y，

计算参考齿位角θ_i处的削切力系数，具体的计算公式为：Combining the coefficient matrix A _i and the values F _i ^x of the four cutting forces in the feed and normal directions,

F _i ^y ,

Calculate the cutting force coefficient at the reference tooth position angle _θi , the specific calculation formula is:

为刃口处径向和切向切削力系数，反映刃口钝圆半径与刃口磨损；

为后刀面的摩擦系数，表征后刀面磨损。in

is the radial and tangential cutting force coefficient at the cutting edge, reflecting the blunt radius of the cutting edge and the wear of the cutting edge;

is the friction coefficient of the flank, which characterizes the wear of the flank.

分别作为纵坐标，绘制未变形切削厚度-径向切削力系数

和未变形切削厚度-切向切削力系数

的散点图，并且采用逻辑回归函数分别拟合未变形切削厚度-径向切削力系数和未变形切削厚度-切向切削力系数的散点图，确定两个拟合曲线的拐点，计算两个拟合曲线拐点的平均值，表征刃口钝圆半径。Referring to Figure 2, taking the undeformed cutting thickness h _i as the abscissa, the radial cutting force coefficient and the tangential cutting force coefficient

As the vertical coordinates, draw the undeformed cutting thickness-radial cutting force coefficient

and undeformed cutting thickness-tangential cutting force coefficient

The scatter plot of the undeformed cutting thickness-radial cutting force coefficient and the undeformed cutting thickness-tangential cutting force coefficient were respectively fitted using the logistic regression function to determine the inflection points of the two fitting curves and calculate the two The average value of the inflection points of the fitted curves represents the radius of the blunt circle of the cutting edge.

Specifically, the collection process of the cutting track profile includes: collecting the maximum profile width radius and the minimum profile width radius of the cutting track, determining the radial runout length r _o and the angle γ _o , and using an image acquisition device to collect the cutting track profile by imaging;

Calculate the undeformed cutting thickness according to the radial runout parameters, including the radial runout length r _o and the angle γ _o and the feed per tooth f _z , the calculation formula is:

为第k个刀齿在采样点i处的齿位角。Where R _k is the equivalent radius of the k-th tooth under the action of jumping, Δθ _m,k is the angle between the two teeth under the action of jumping, h _k (i) is the k-th tooth at the sampling point i Theoretical undeformed cutting thickness at

is the tooth position angle of the kth tooth at sampling point i.

Specifically, in order to verify the accuracy of the micro milling cutter edge wear monitoring method based on the identification of the inflection point of the cutting force coefficient curve, in this embodiment, a comparative experiment was carried out between monitoring the radius of the blunt circle and actually measuring the radius of the blunt circle according to the method. The specific experiment The process is:

Taking the micro-milling of straight slots with two-edged flat milling cutters as an example, the radius of the blunt circle of the new cutter is about 2 ^μm , the helix angle is 30°, the rake angle is 0°, the relief angle is 7°, and the tool diameter is 800 μm;

The first step: set the milling parameters as rpm=18000, the feed rate per tooth is 4 μm, and the axial depth of cut is 60 μm;

The second step: use the force sensor to collect the cutting force in real time;

The third step: use the image acquisition device to collect the cutting track profile by imaging method, and calculate the run-out length of 0.9 μm and the run-out angle of 18° according to the cutting track profile;

Step 4: Calculate the theoretical undeformed cutting thickness according to the runout parameters (runout length is 0.9 μm, runout angle is 18°) and feed rate per tooth is 4 μm;

Step 5: Calculate the coefficient matrix, and calculate the cutting force coefficient for every two adjacent sampling points, including the radial cutting force coefficient and the tangential cutting force coefficient;

Step 6: draw undeformed cutting thickness-radial cutting force coefficient, undeformed cutting thickness-tangential cutting force coefficient scatter diagram;

Step 7: Fit the scatter plot with the logistic regression function, calculate the inflection point of the fitting curve, and find the average value of the inflection points of the two curves to represent the blunt circle radius of wear and monitor the wear of the cutting edge;

Step 8: Subsequent cutting segments, repeat the above steps 2 to 7.

Stop the machine after each tool pass, and use a microscope to calibrate the radius of the blunt circle of the cutting edge. The actual wear of the cutting edge and the monitored blunt circle radius of the first three cutting segments are shown in Table 1:

cutting fragment Measure blunt circle radius Monitor blunt circle radius Monitoring error 1 2.00μm 1.86μm 7.00% 2 2.20μm 2.32μm 5.45% 3 2.50μm 2.39μm 4.40%

Table 1

Through the comparison of the wear monitoring value of the micro-milling cutter edge and the actual measured value in Table 1, it can be seen that a kind of micro-milling cutter edge wear monitoring method proposed by the present invention can effectively monitor the wear of the micro-milling cutter edge, and the monitoring error is no more than 10%. , can accurately monitor the wear of the edge of the micro-milling cutter, and implement the estimation of the sharpness of the edge of the micro-milling cutter.

Those skilled in the art should understand that the embodiments of the present application may be provided as methods, systems, or computer program products. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowcharts and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general purpose computer, special purpose computer, embedded processor, or processor of other programmable data processing equipment to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing equipment produce a An apparatus for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions The device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions can also be loaded onto a computer or other programmable data processing device, causing a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process, thereby The instructions provide steps for implementing the functions specified in the flow chart or blocks of the flowchart and/or the block or blocks of the block diagrams.

Apparently, the above-mentioned embodiments are only examples for clear description, and are not intended to limit the implementation. For those of ordinary skill in the art, on the basis of the above description, other changes or changes in various forms can also be made. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (7)

1. A micro-milling cutter edge wear monitoring method based on cutting force coefficient curve inflection point recognition, is characterized in that: comprise the following steps: S1. Collect the cutting force and cutting track profile of the micro-milling cutter; the cutting force collection process includes: collecting the feed and normal four cutting forces at every two adjacent reference tooth position angles θ _i and θ _i+1 The value of F _i ^x ,

F _i ^y ,

S2. Calculate the cutting force coefficient according to the cutting force. According to the feed and normal four cutting force values F _i ^x ,

F _i ^y ,

Calculate the radial cutting force coefficient and the tangential cutting force coefficient. The calculation process of the cutting force coefficient includes: calculating the coefficient matrix according to the undeformed cutting thickness and the axial cutting depth, combining the coefficient matrix with the feed and normal four cutting forces F _i ^x ,

F _i ^y ,

Calculate the cutting force coefficient at the reference tooth position angle θ _i ; calculate the undeformed cutting thickness according to the cutting track profile; S3, drawing undeformed cutting thickness-cutting force coefficient scatter diagram; S4, using the logistic regression function to fit the scatter plot, calculating the inflection point of the fitting curve, and characterizing the radius of the blunt circle of the cutting edge. 2. the micro milling cutter edge wear monitoring method based on cutting force coefficient curve inflection point identification according to claim 1, is characterized in that: in step S3, take undeformed cutting thickness as abscissa, radial cutting force coefficient and cutting The cutting force coefficient is taken as the ordinate respectively, and the scatter diagrams of undeformed cutting thickness-radial cutting force coefficient and undeformed cutting thickness-tangential cutting force coefficient are drawn. 3. The micro-milling cutter edge wear monitoring method based on the inflection point identification of the cutting force coefficient curve according to claim 1, characterized in that: in step S4, a logistic regression function is used to respectively fit the undeformed cutting thickness-radial cutting force coefficient and undeformed cutting thickness-tangential cutting force coefficient scatter plot, determine the inflection point of the two fitting curves, calculate the average value of the inflection points of the two fitting curves, and characterize the radius of the blunt circle of the cutting edge. 4. The micro-milling cutter edge wear monitoring method based on cutting force coefficient curve inflection point identification according to claim 1, characterized in that: in step S1, the collection process of the cutting track profile comprises: collecting the maximum profile width radius of the cutting track And minimum profile width radius, determine the radial runout length r _o and angle γ _o . 5. The micro milling cutter edge wear monitoring method based on the identification of the inflection point of the cutting force coefficient curve according to claim 1, wherein in step S2, the undeformed cutting thickness is calculated according to the radial runout parameter and the feed per tooth . 6. The micro-milling cutter edge wear monitoring method based on the inflection point identification of the cutting force coefficient curve according to claim 1, characterized in that: in step S1, the sampling frequency is set according to the spindle speed, and the cutting force of the micro-milling cutter is collected to ensure that the spindle One degree of rotation takes one sample. 7. The micro milling cutter edge wear monitoring method based on the inflection point identification of the cutting force coefficient curve according to claim 1, characterized in that: in step S1, a force sensor is set to collect cutting force, and an image acquisition device is set to collect the cutting track profile.

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