Method and system for monitoring wear of rough-fine boring tool based on spindle load current

Abstract

This invention relates to the field of machine tool condition monitoring technology, specifically to a method and system for monitoring the wear of roughing and finishing boring tools based on spindle load current. The method includes: collecting spindle load current, spindle speed, feed rate, blank hole depth, cutting edge width, and unit cutting force; calculating the cutting load index at each moment; segmenting load abrupt change periods based on the load index sequence; calculating the current response offset using current and load data from the load abrupt change periods and their adjacent stable periods; constructing a wear trend scatter plot from the current response offsets of multiple consecutive load abrupt change periods; extracting the wear trend coefficient to obtain the wear index; and collecting the wear indices of historical boring tools and the current boring tool to assess the wear degree of the current boring tool. This invention accurately detects the wear state of boring tools by analyzing the synchronous response relationship between spindle load current and cutting load during load abrupt change periods.

Description

Technical Field

[0001] This invention relates to the field of machine tool condition monitoring technology, specifically to a method and system for monitoring roughing and finishing boring tool wear based on spindle load current. Background Technology

[0002] As the machinery manufacturing industry continues to develop towards higher precision, higher efficiency, and automation, roughing and finishing boring tools are widely used in engine cylinder blocks, hydraulic valve bodies, housing parts, and various precision hole machining scenarios. During the boring process, the wear state of the boring tool directly affects the hole diameter accuracy, surface roughness, and machining stability. When the boring tool wears to a certain extent, it not only leads to a decline in machining quality but may also cause problems such as tool breakage, workpiece scrap, and abnormal equipment downtime. However, most existing technologies are based on the analysis of monitoring data at a single moment or within a local time period, lacking comprehensive utilization of the long-term wear evolution trend and historical life pattern. They are easily affected by occasional operating condition disturbances, noise interference, and individual differences, resulting in low accuracy of wear assessment results and making it difficult to provide a reliable basis for boring tool life prediction and replacement decisions. Summary of the Invention

[0003] This invention provides a method and system for monitoring the wear of roughing and finishing boring tools based on spindle load current, in order to solve the existing problems: most existing technologies are based on the analysis of monitoring data at a single moment or in a local time period, resulting in low accuracy of wear assessment results and difficulty in providing a reliable basis for boring tool life prediction and replacement decisions.

[0004] The present invention provides a method and system for monitoring roughing and finishing boring tool wear based on spindle load current, which adopts the following technical solution: One embodiment of the present invention provides a method for monitoring wear of roughing and finishing boring tools based on spindle load current, the method comprising the following steps: The system obtains the spindle load current, spindle speed, boring tool feed rate, and blank hole depth at various moments during the current boring process, and also obtains the boring tool cutting edge width and the unit cutting force of the workpiece material. Based on the spindle speed and boring tool feed rate at each moment, combined with the boring tool cutting edge width, blank hole depth, and unit cutting force of the workpiece material, the cutting load index at each moment is obtained; based on the cutting load index at each moment, the boring tool machining time period is divided into several cutting time periods, and the load change period is selected; based on the cutting load index at each moment of the load change period and its adjacent cutting time period and the spindle load current, the current response deviation of the load change period is obtained; Based on the current response offset during continuous load change periods, a scatter plot of wear trend during load change periods is constructed; based on the scatter plot of wear trend during load change periods, the wear trend coefficient of load change periods is obtained, and then the wear index of load change periods is obtained. Obtain the wear index of all load change periods of the historical boring tool. Based on the wear index of all load change periods of the historical boring tool, obtain the boring tool break-in reference value and the boring tool failure reference value. Combine the wear index of all load change periods of the current boring tool to obtain the wear degree of the current boring tool.

[0005] Preferably, the method for obtaining the cutting load index at each moment based on the spindle speed, boring tool feed rate, boring tool cutting edge width, blank hole depth, and unit cutting force of the workpiece material includes: For any given time, the cutting load index at that time is positively correlated with the spindle speed at that time; The cutting load index at that moment is positively correlated with the boring tool feed rate at that moment; The cutting load index at the specified moment is positively correlated with the blank hole depth; The cutting load index at the specified moment is positively correlated with the unit cutting force of the workpiece material; The cutting load index at the specified moment is negatively correlated with the boring tool cutting edge width.

[0006] Preferably, the specific method for dividing the boring tool machining time into several cutting time periods based on the cutting load index at each time point, and screening out the periods of sudden load changes, includes: Based on the cutting load index at all times during the boring tool machining period, the boring tool machining period is divided into several cutting periods using the variable point grouping method. For any cutting period, the average value of the cutting load index at all times during the cutting period is recorded as the baseline cutting load level for the cutting period. If the difference between the baseline cutting load level of the cutting period and the baseline cutting load level of the previous cutting period is greater than the preset difference threshold of the cutting period, then the cutting period is regarded as the load change period.

[0007] Preferably, the method for obtaining the current response offset during the load abrupt change period based on the cutting load index and spindle load current at each moment in the load abrupt change period and its adjacent cutting periods includes: For any time within any load change period, the average value of the cutting load index at all times within the cutting period adjacent to the load change period is denoted as the comparative cutting load degree of the load change period. The average value of the spindle load current at all times during the cutting period adjacent to the load change period is recorded as the comparative spindle load current value during the load change period. The difference between the spindle load current at the moment of the load change period and the comparative spindle load current value during the load change period is denoted as the spindle load current offset factor at the moment of the load change period. The difference between the cutting load index at the moment of the load change period and the comparative cutting load level during the load change period is denoted as the cutting load offset factor at the moment of the load change period. The sum of the ratios of the spindle load current offset factor to the cutting load offset factor at all times during the load abrupt change period is linearly normalized, and the normalized result is used as the current response offset during the load abrupt change period.

[0008] Preferably, the specific method for constructing a scatter plot of wear trends during the load abrupt change period based on the current response offset during the continuous load abrupt change period is as follows: For any load mutation period, a preset number of preceding load mutation periods is defined. The period before the load mutation Each period of load mutation is denoted as the preceding load mutation period; A rectangular coordinate system is constructed with time as the horizontal axis and the current response offset during the load change period as the vertical axis. Based on the last moment of each preceding load change period and the current response offset, each preceding load change period is taken as a data point and placed into the rectangular coordinate system to obtain a scatter plot of the wear trend during the load change period.

[0009] Preferably, the method for obtaining the wear trend coefficient for the period of load change based on the wear trend scatter plot during the period of load change includes: For any load change period, the RANSAC algorithm is used to fit a straight line to the scatter plot of the wear trend during the load change period. The fitted straight line is recorded as the wear evolution trend line of the load change period, and the slope of the wear evolution trend line of the load change period is used as the wear trend coefficient of the load change period.

[0010] Preferably, the specific method for obtaining the wear index during the period of load abrupt change is as follows: Record any data point in the scatter plot of the wear trend during the load mutation period as the target point, and obtain the contribution weight of the target point based on the distance between the target point and the wear evolution trend line during the load mutation period in the vertical direction. The contribution weight of the target point is negatively correlated with the distance between the target point and the wear evolution trend line during the load change period in the vertical axis direction; The product of the contribution weight of the target point and the current response offset corresponding to the target point is used as the wear factor of the target point; the sum of the wear factors of all data points in the wear trend scatter plot of the load change period is used as the wear response coefficient of the load change period. The wear index of the load abrupt change period is obtained by multiplying half the duration of the wear trend scatter plot corresponding to the load abrupt change period by the wear trend coefficient of the load abrupt change period, and then adding the wear response coefficient of the load abrupt change period to the product.

[0011] Preferably, the specific method for obtaining the boring tool break-in reference value and the boring tool failure reference value based on the wear index of all load change periods of the historical boring tool includes: Retrieve the wear index of each historical boring tool during all periods of load abrupt change in its service life from the database; for any historical boring tool, sort the wear index of the historical boring tool during all periods of load abrupt change in its service life according to the corresponding time to obtain the wear index sequence of the historical boring tool during its service life; The Ruptures algorithm is used to obtain the two inflection points with the largest rate of change in the wear index sequence of the historical boring tool during its service life. The wear index corresponding to the first inflection point is recorded as the running-in coefficient of the historical boring tool, and the wear index corresponding to the second inflection point is recorded as the failure critical coefficient of the historical boring tool. The average of the break-in coefficients of all historical boring tools is used as the benchmark value for boring tool break-in. Based on the failure critical coefficients of all historical boring tools, and combined with the Weibull distribution estimation method, the percentage is estimated. The wear index threshold at which the boring tool reaches failure is used as the benchmark value for boring tool failure. This represents the preset percentage of allowed failures.

[0012] Preferably, the specific method for obtaining the current wear degree of the boring tool is as follows: The Ruptures algorithm is used to obtain the two inflection points with the largest rate of change in the wear index sequence of the current boring tool's service life, and the wear index corresponding to the first inflection point is recorded as the running-in coefficient of the current boring tool. Based on the current boring bar's break-in coefficient, the wear index of the current boring bar during the most recent period of load change, and combined with the boring bar's break-in reference value and the boring bar's failure reference value, the current wear degree of the boring bar is obtained. The wear degree of the current boring tool is positively correlated with the wear index of the current boring tool during the most recent period of load change; The current wear level of the boring tool is positively correlated with the boring tool break-in reference value; The wear degree of the current boring tool is negatively correlated with the break-in coefficient of the current boring tool; The current wear level of the boring tool is negatively correlated with the boring tool failure reference value.

[0013] Another embodiment of the present invention provides a roughing and finishing boring tool wear monitoring system based on spindle load current, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of any of the above-described roughing and finishing boring tool wear monitoring methods based on spindle load current.

[0014] The beneficial effects of the technical solution of this invention are as follows: This invention collects and analyzes the spindle load current, spindle speed, boring tool feed rate, blank hole depth, boring tool cutting edge width, and workpiece material unit cutting force at various moments during the current boring tool machining process. It then constructs a cutting load index to uniformly characterize the actual load state under different machining conditions. Furthermore, it identifies periods of load abrupt change through the cutting load index and obtains the current response offset by utilizing the load difference and current response relationship between the periods of load abrupt change and adjacent cutting periods. This reduces the impact of working condition changes on wear monitoring results. Simultaneously, a scatter plot of wear trends is constructed by measuring the current response offset during continuous load abrupt changes, and the wear index is obtained by combining the wear trend coefficient, thus achieving a dynamic characterization of the boring tool wear evolution process. Furthermore, by combining the wear index of historical boring tools, the boring tool break-in benchmark value and boring tool failure benchmark value are obtained, and the current wear degree of the boring tool is evaluated accordingly. This allows for full utilization of historical life patterns to calibrate the current boring tool condition, improving the accuracy, stability, and reliability of boring tool wear monitoring and life assessment results, and providing an effective basis for boring tool maintenance, replacement, and machining quality control. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart illustrating the steps of the roughing and finishing boring tool wear monitoring method based on spindle load current according to the present invention. Detailed Implementation

[0017] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of the roughing and finishing boring tool wear monitoring method and system based on spindle load current proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0019] The following description, in conjunction with the accompanying drawings, details the specific scheme of the roughing and finishing boring tool wear monitoring method and system based on spindle load current provided by this invention.

[0020] Please see Figure 1 The diagram illustrates a flowchart of a roughing and finishing boring tool wear monitoring method based on spindle load current according to an embodiment of the present invention. The method includes the following steps: Step S001: Obtain the spindle load current, spindle speed, boring tool feed rate and blank hole depth at each moment during the current boring process, and obtain the boring tool cutting edge width and the unit cutting force of the workpiece material.

[0021] It should be noted that during the cutting process, the boring tool becomes dull due to wear, increasing the cutting resistance. The spindle motor needs to output greater torque to overcome this resistance, which in turn causes the spindle load current to increase. That is, the spindle load current contains information directly related to the tool wear state. At the same time, the spindle load current is not only affected by the wear state, but also by factors such as spindle speed, boring tool feed rate, workpiece material properties, and machining structure parameters. Therefore, this embodiment simultaneously acquires parameters such as spindle load current, spindle speed, boring tool feed rate, blank hole depth, boring tool cutting edge width, and workpiece material unit cutting force to establish the correlation between cutting load and current response. This allows for the analysis of the boring tool wear state while considering differences in working conditions, thereby improving the accuracy and reliability of wear monitoring results.

[0022] Specifically, the spindle load current at each moment during the boring process is collected by a Hall current sensor installed on the power supply cable of the machine tool spindle drive motor, and the spindle speed and boring feed rate at each moment are read from the machine tool control system. The system obtains the blank hole depth, boring tool cutting edge width, and unit cutting force of the workpiece material. The blank hole depth and boring tool cutting edge width are input by the operator through the control panel. The unit cutting force of the workpiece material is obtained by the system from a preset material parameter library after the operator inputs the workpiece material type through the control panel.

[0023] Step S002: Based on the spindle speed and boring tool feed rate at each moment, combined with the boring tool cutting edge width, blank hole depth, and unit cutting force of the workpiece material, obtain the cutting load index at each moment; based on the cutting load index at each moment, divide the boring tool machining time period into several cutting time periods, and select the load change period; based on the cutting load index at each moment of the load change period and its adjacent cutting time period and the spindle load current, obtain the current response deviation of the load change period.

[0024] It should be noted that the impact of boring tool wear on the spindle load current manifests as an increase in the spindle current demand under the same cutting load conditions. Furthermore, when the boring tool is machining keyways, transverse holes, and other structures in the blank hole, the cutting load index and the spindle load current will undergo significant abrupt changes simultaneously. This clearly reflects the current response capability of the tool under load impact. The more severely worn the tool, the more current it needs to consume to overcome the additional resistance under the same load impact. Therefore, this embodiment analyzes the deviation of the spindle load current response relative to the change in cutting load by screening the period of load abrupt change and comparing it with the adjacent stable cutting period. This allows for the extraction of the current response deviation that reflects the wear state of the boring tool, thereby accurately monitoring the wear condition of the boring tool.

[0025] Specifically, for any given time, the cutting load index is obtained based on the spindle speed, boring tool feed rate, boring tool cutting edge width, blank hole depth, and unit cutting force of the workpiece material at that time.

[0026] The cutting load index at that moment is positively correlated with the spindle speed at that moment; The cutting load index at that moment is positively correlated with the boring tool feed rate at that moment; The cutting load index at the specified moment is positively correlated with the blank hole depth; The cutting load index at the specified moment is positively correlated with the unit cutting force of the workpiece material; The cutting load index at the specified moment is negatively correlated with the boring tool cutting edge width.

[0027] As an example, the specific formula for calculating the cutting load index at the stated moment is as follows: ; In the formula, The cutting load index represents the time specified. This indicates the spindle speed at the stated moment; This indicates the feed rate of the boring tool at the stated moment; Indicates the width of the boring bar's cutting edge; Indicates the depth of the hole in the blank; This represents the unit cutting force of the workpiece material.

[0028] It should be noted that the spindle speed determines the frequency of contact between the cutting edge and the workpiece material per unit time; the higher the speed, the greater the cutting load. The feed rate determines the volume of material removed per unit time; the faster the feed rate, the greater the cutting load. The unit cutting force of the workpiece material reflects the material's ability to resist cutting; the more difficult the material is to machine, the greater the cutting load. The blank hole depth affects the overhang length of the boring tool; the deeper the hole, the worse the tool rigidity, and to maintain a stable cutting process, greater structural deformation and additional load need to be overcome, thus the overall cutting load tends to increase. The cutting edge width determines the contact area between the cutting edge and the workpiece; the wider the cutting edge, the more dispersed the cutting force distribution, and the smaller the load per unit area. Therefore, this embodiment integrates the positive or negative correlations between each factor and the cutting load into a cutting load index to characterize the actual load state of the boring tool under different working conditions under a unified dimension, and to provide a unified load evaluation basis for subsequent identification of load change periods and wear state analysis.

[0029] Specifically, based on the cutting load index at all times within the boring tool machining time period, the boring tool machining time period is divided into several cutting time periods using the variable point grouping method. Since the variable point grouping method is a well-known existing technology, it will not be described in detail in this embodiment. For any cutting period, the average value of the cutting load index at all times during the cutting period is recorded as the baseline cutting load level for the cutting period. If the difference between the baseline cutting load level of the cutting period and the baseline cutting load level of the previous cutting period is greater than the preset difference threshold of the cutting period, then the cutting period is regarded as a load change period. The specific value of the preset difference threshold of the cutting period can be set according to the actual situation. This embodiment does not make a hard requirement. In this embodiment, the sum of the mean of the cutting load index at all times in the previous cutting period plus its standard deviation is used as the difference threshold of the cutting period.

[0030] It should be noted that the cutting load experienced by the boring tool during machining changes in stages due to variations in workpiece structure, machining allowance, and the appearance of local feature areas. Therefore, the entire machining process typically consists of multiple cutting stages with relatively stable but differing load levels. This embodiment first uses a variable point grouping method to identify the location of cutting load changes and divides the machining process into several cutting periods. Then, the average value of the cutting load index at all times within each cutting period characterizes the overall load level corresponding to that cutting period, thereby reducing the impact of instantaneous fluctuations on the load assessment results. Furthermore, when the boring tool enters the keyway region, transverse hole region, or other machining areas that significantly increase cutting resistance, the overall load level of its corresponding cutting period will be significantly higher than the previous cutting period. Therefore, the difference between the baseline cutting load levels of adjacent cutting periods can be used to determine whether a load mutation has occurred, allowing the load mutation judgment criteria to adaptively adjust with changes in machining conditions, thereby improving the accuracy and stability of load mutation period identification.

[0031] Specifically, for any time within any load change period, the average value of the cutting load index at all times within the cutting period adjacent to the load change period is recorded as the comparative cutting load degree of the load change period. The average value of the spindle load current at all times during the cutting period adjacent to the load change period is recorded as the comparative spindle load current value during the load change period. The difference between the spindle load current at the moment of the load change period and the comparative spindle load current value during the load change period is denoted as the spindle load current offset factor at the moment of the load change period. The difference between the cutting load index at the moment of the load change period and the comparative cutting load level during the load change period is denoted as the cutting load offset factor at the moment of the load change period. The sum of the ratios of the spindle load current offset factor to the cutting load offset factor at all times during the load abrupt change period is linearly normalized, and the normalized result is used as the current response offset during the load abrupt change period.

[0032] As an example, the specific formula for calculating the current response offset during the load abrupt change period is as follows: ; In the formula, This indicates the current response offset during the period of load abrupt change; This indicates the number of moments within the aforementioned load mutation period; Indicates the first time during the period of load mutation. The spindle load current at each moment; This indicates the comparison spindle load current value during the period of load abrupt change; Indicates the first time during the period of load mutation. The cutting load index at each moment; This indicates the degree of comparative cutting load during the period of sudden load change; The linear normalization function can be normalized using a maximum and minimum value normalization function. The maximum and minimum values ​​can be obtained based on historical data or prior experience. Adjusting, calibrating, or optimizing the maximum and minimum values ​​does not constitute a limitation of this invention. The final normalized value range is [0, 1].

[0033] It should be noted that the spindle load current offset factor represents the magnitude of the change in spindle current relative to the reference state after a sudden load change, while the cutting load offset factor represents the magnitude of the change in cutting load relative to the reference state. This indicates the spindle current response intensity caused by a unit change in cutting load. When the boring tool is lightly worn, the cutting edge is sharp, the cutting efficiency is good, and the current increment caused by the increase in cutting load is small. As the wear of the boring tool continues to increase, the cutting edge dulling phenomenon gradually intensifies, and the friction, extrusion, and plastic deformation effects generated during the cutting process continuously increase. Under the same cutting load increment, more spindle driving force needs to be consumed, so the corresponding spindle load current increment will also increase synchronously. Therefore, the ratio of the spindle load current offset factor to the cutting load offset factor can effectively characterize the sensitivity of the boring tool to load changes, thereby indirectly reflecting the wear state of the boring tool.

[0034] Step S003: Based on the current response offset during continuous load change periods, construct a scatter plot of wear trend during load change periods; based on the scatter plot of wear trend during load change periods, obtain the wear trend coefficient of load change periods, and then obtain the wear index of load change periods.

[0035] It should be noted that boring tool wear is a continuous cumulative process, and its wear degree gradually increases with the increase of machining time, rather than abruptly occurring within a single load change period. Therefore, this embodiment uses the current response offset corresponding to multiple consecutive load change periods to construct a wear trend scatter plot. By analyzing the overall change trend between multiple historical windows, the wear trend coefficient is extracted to reflect the long-term evolution direction of the wear state. At the same time, the wear index is calculated by combining the matching degree of each data point with the overall trend, thereby reducing the impact of occasional abnormal factors on the monitoring results and making the obtained wear evaluation results more consistent with the actual wear law of boring tools.

[0036] Specifically, for any load mutation period, a preset number of preceding load mutation periods is defined. The period before the load mutation Each period of load mutation is denoted as the preceding load mutation period. The specific value can be set according to the actual situation. This embodiment does not make a hard requirement. In this embodiment, it is used as... Let's take 10 as an example; A rectangular coordinate system is constructed with time as the horizontal axis and the current response offset during the load change period as the vertical axis. Based on the last moment of each preceding load change period and the current response offset, each preceding load change period is taken as a data point and placed into the rectangular coordinate system to obtain a scatter plot of the wear trend during the load change period.

[0037] Furthermore, for any load change period, the RANSAC algorithm is used to perform a straight line fitting on the wear trend scatter plot of the load change period. The resulting fitted straight line is recorded as the wear evolution trend line of the load change period, and the slope of the wear evolution trend line of the load change period is used as the wear trend coefficient of the load change period. Since the RANSAC algorithm is a well-known prior art, it will not be described in detail in this embodiment.

[0038] It should be noted that boring tool wear accumulates gradually during continuous cutting. Therefore, the current response deviation corresponding to a single load abrupt change can only reflect the local state at a certain moment and cannot accurately reflect the development trend of boring tool wear. Therefore, this embodiment introduces a preceding load abrupt change period, correlates the current load abrupt change period with multiple previous load abrupt change periods, and characterizes the wear evolution process by observing the change law of current response deviation with machining time. A wear evolution trend line is fitted with a wear trend scatter plot, and the slope of the trend line is used as the wear trend coefficient to quantify the wear trend of the boring tool during machining.

[0039] Furthermore, any data point in the scatter plot of the wear trend during the load abrupt change period is recorded as the target point, and the contribution weight of the target point is obtained based on the distance between the target point and the wear evolution trend line during the load abrupt change period in the vertical direction. The contribution weight of the target point is negatively correlated with the distance between the target point and the wear evolution trend line during the load change period in the vertical axis direction; The product of the contribution weight of the target point and the current response offset corresponding to the target point is used as the wear factor of the target point; the sum of the wear factors of all data points in the wear trend scatter plot of the load change period is used as the wear response coefficient of the load change period. The product obtained by multiplying half the duration of the wear trend scatter plot corresponding to the load abrupt change period by the wear trend coefficient of the load abrupt change period, and adding the sum of the wear response coefficient of the load abrupt change period, is used as the wear index of the load abrupt change period (the duration of the wear trend scatter plot corresponding to the load abrupt change period is the time length from the first data point to the last data point in the wear trend scatter plot of the load abrupt change period).

[0040] As an example, the specific formula for calculating the wear index during the period of load abrupt change is as follows: ; In the formula, This indicates the wear index during the period of sudden load change; The scatter plot representing the wear trend during the period of load abrupt change is shown in the figure. Each data point contributes a weight; The scatter plot representing the wear trend during the period of load abrupt change is shown in the figure. The distance between each data point and the wear evolution trend line during the load abrupt change period in the vertical axis direction; The maximum distance between all data points in the wear trend scatter plot during the load abrupt change period and the wear evolution trend line along the vertical axis. The number of data points in the scatter plot representing the wear trend during the period of load abrupt change; The scatter plot representing the wear trend during the period of load abrupt change is shown in the figure. Current response offset corresponding to each data point; This represents the wear trend coefficient during the period of sudden load change; The scatter plot representing the wear trend during the period of sudden load change corresponds to the duration of the wear trend. This represents the weight normalization function.

[0041] It should be noted that boring tool wear is a gradual, cumulative process, and its evolution trajectory exhibits good continuity and trend. Therefore, data points that are closer to the wear evolution trend line often better reflect the true wear state of the boring tool. Thus, this embodiment constructs contribution weights based on the distance between data points and the wear evolution trend line along the vertical axis, and makes the contribution weights negatively correlated with the distance. This increases the influence of data points that conform to the overall wear pattern on the results. Furthermore, since the current response offset reflects the response intensity of the spindle current relative to the cutting load change during load variation, combining the contribution weights with the corresponding current response offsets to obtain the wear factor can weaken the impact of abnormal fluctuations while preserving wear information. The wear response obtained by accumulating all wear factors... The coefficient is used to characterize the overall wear response level of the boring tool in the current stage. On the other hand, the wear response coefficient represents the wear accumulation during the historical load change period, while the wear trend coefficient reflects the rate of change of the wear state over time. Therefore, this embodiment further combines the wear trend coefficient and the corresponding duration of the wear trend scatter plot to construct a trend term. The wear trend coefficient is used to reflect the wear growth rate, and the corresponding duration of the wear trend scatter plot is used to reflect the time scale of the continuous development of wear. The two together characterize the evolution trend of wear. Finally, the trend term and the wear response coefficient are fused to obtain the wear index of the load change period. The obtained wear index can reflect both the current wear level and the wear development trend, thereby more comprehensively characterizing the actual wear state of the boring tool.

[0042] Step S004: Obtain the wear index of all load change periods of the historical boring tool. Based on the wear index of all load change periods of the historical boring tool, obtain the boring tool break-in reference value and the boring tool failure reference value. Combine the wear index of all load change periods of the current boring tool to obtain the wear degree of the current boring tool.

[0043] It should be noted that in the field of machining, the wear process of cutting tools generally follows a three-stage pattern: rapid wear in the early break-in stage, followed by a long-term stable normal wear stage, and finally, severe wear and rapid failure. For the same type of cutting tool, the proportion of each of the three stages in its entire life cycle is basically the same. Therefore, this invention identifies two inflection points for each tool by collecting a large number of complete wear index sequences of historical boring tools of the same model from brand new to scrap, namely, the transition from the break-in period to the normal wear period and from the normal wear period to the severe wear period. The first inflection point reflects the wear state of the tool when it completes the initial break-in, and the second inflection point is the critical failure point when the tool enters a dangerous state. By collecting the data of these two inflection points of all historical tools, statistically significant break-in and failure benchmark values ​​can be established, providing an objective reference scale for the current tool life assessment, and thus providing a more scientific basis for tool replacement decisions.

[0044] Specifically, the wear index of each historical boring tool during all periods of load abrupt change in its service life is retrieved from the database (the historical boring tool is the same model as the current boring tool and has been replaced due to wear reaching its service life). For any historical boring tool, the wear index of the historical boring tool during all periods of load abrupt change in its service life is sorted according to the corresponding time to obtain the wear index sequence of the historical boring tool during its service life. The Ruptures algorithm is used to obtain the two inflection points with the largest rate of change in the wear index sequence of the historical boring tool during its service life. The wear index corresponding to the first inflection point is recorded as the running-in coefficient of the historical boring tool, and the wear index corresponding to the second inflection point is recorded as the failure critical coefficient of the historical boring tool. Since the Ruptures algorithm is a well-known existing technology, it will not be described in detail in this embodiment. The average of the break-in coefficients of all historical boring tools is used as the benchmark value for boring tool break-in. Based on the failure critical coefficients of all historical boring tools, and combined with the Weibull distribution estimation method, the percentage is estimated. The wear index threshold at which the boring tool reaches failure is used as the boring tool failure threshold. The preset allowable failure percentage, the The specific value can be set according to the actual situation. This embodiment does not make a hard requirement. In this embodiment, it is used as... Taking 10 as an example, since the Weibull distribution estimation method is a well-known existing technology, it will not be described in detail in this embodiment.

[0045] It should be noted that boring tool wear typically exhibits distinct phases. It undergoes a break-in phase in the initial stage of use, followed by a stable wear phase, and finally a failure wear phase. The wear growth rate varies significantly across these phases, while the proportion of each phase in the total lifespan is roughly the same. Therefore, this embodiment analyzes the wear index sequence over the complete service life of historical boring tools, using the two inflection points with the largest rates of change to characterize the end of the break-in phase and the beginning of the failure wear phase, respectively, thereby obtaining the break-in coefficient and failure threshold coefficient for historical boring tools. Considering that boring tools of the same model undergo manufacturing... Due to factors such as errors, clamping conditions, and machining conditions, there will still be certain individual differences. Therefore, by statistically averaging the running-in coefficients of all historical boring tools, a benchmark value for boring tool running-in that can reflect the overall running-in characteristics of boring tools of the same model can be obtained. At the same time, since the failure state of boring tools has a certain degree of randomness and discreteness, the failure critical coefficient of all historical boring tools is statistically modeled using the Weibull distribution, and the failure threshold of boring tools is determined by combining the allowable failure percentage. This establishes a life reference system that conforms to the actual life law, providing a basis for accurately assessing the current wear stage of the boring tool and its degree of approach to failure.

[0046] Specifically, the Ruptures algorithm is used to obtain the two inflection points with the largest rate of change in the wear index sequence of the current boring tool's service life, and the wear index corresponding to the first inflection point is recorded as the current boring tool's break-in coefficient; Based on the current boring bar's break-in coefficient, the wear index of the current boring bar during the most recent period of load change, and combined with the boring bar's break-in reference value and the boring bar's failure reference value, the current wear degree of the boring bar is obtained. The wear degree of the current boring tool is positively correlated with the wear index of the current boring tool during the most recent period of load change; The current wear level of the boring tool is positively correlated with the boring tool break-in reference value; The wear degree of the current boring tool is negatively correlated with the break-in coefficient of the current boring tool; The current wear level of the boring tool is negatively correlated with the boring tool failure reference value.

[0047] As an example, the specific formula for calculating the current wear level of the boring tool is as follows: ; In the formula, This indicates the current wear level of the boring tool; This indicates the wear index during the most recent period of load change in the boring tool; This indicates the current break-in coefficient of the boring tool; This indicates the reference value for boring tool break-in; This indicates the reference value for boring tool failure; This represents the pre-set conservative estimate coefficient. The specific value can be set according to the actual situation. This embodiment does not make a hard requirement. In this embodiment, it is used as... Taking 0.8 as an example, the purpose is to lower the estimated end-of-life threshold, so as to reserve an additional safety margin and avoid tool failure before the expected end of life due to statistical bias or individual differences.

[0048] It should be noted that, due to differences in initial manufacturing errors, clamping conditions, and actual machining conditions among different boring tools, the actual wear stages corresponding to the same wear index may not be completely consistent. Therefore, this embodiment first obtains the break-in coefficient of the current boring tool by using the break-in inflection point in its own wear index sequence to characterize the individual characteristics formed by the current boring tool in the early stage of its lifespan. Then, it compares the break-in coefficient of the current boring tool with the break-in benchmark value formed by a group of boring tools of the same model to correct for individual differences in the current wear state. Simultaneously, it introduces the boring tool failure benchmark value obtained from historical boring tool statistics as a lifespan endpoint reference, enabling the current wear state to be mapped to the complete lifespan range for evaluation. The larger the wear index during the most recent load mutation period of the current boring tool, the more severe the current wear state. The break-in coefficient of the current boring tool... The larger the number, the higher the wear level of the boring tool in the early stages of its lifespan, and therefore the actual wear level corresponding to the same wear index is relatively lower. The larger the boring tool break-in reference value, the higher the wear level corresponding to the overall break-in stage of the same model boring tool, and therefore the current wear level is correspondingly increased. The larger the boring tool failure reference value, the higher the allowable failure wear level, and therefore the current wear level is relatively reduced. On the other hand, considering that there may still be some deviation between the historical statistical model and the actual machining environment, and that the wear level of different boring tools when they reach the failure state also has a certain degree of dispersion, a conservative estimation coefficient is further introduced to make a safety correction to the failure reference value, and to appropriately predict the end of the lifespan in advance, thereby reserving a safety margin for boring tool replacement and maintenance decisions and reducing the risk of sudden failure caused by individual differences or statistical errors.

[0049] Furthermore, a wear threshold is preset. The specific value of the wear threshold can be set according to the actual situation. This embodiment does not make a hard requirement. In this embodiment, the wear threshold is 0.85 as an example. When the wear of the boring tool is greater than the wear threshold, it means that the boring tool has been severely worn and needs to be replaced.

[0050] Another embodiment of the present invention provides a roughing and finishing boring tool wear monitoring system based on spindle load current, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the roughing and finishing boring tool wear monitoring method based on spindle load current in steps S001 to S004.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for monitoring wear of roughing and finishing boring tools based on spindle load current, characterized in that, The method includes the following steps: The system obtains the spindle load current, spindle speed, boring tool feed rate, and blank hole depth at various moments during the current boring process, and also obtains the boring tool cutting edge width and the unit cutting force of the workpiece material. Based on the spindle speed and boring tool feed rate at each moment, combined with the boring tool cutting edge width, blank hole depth, and unit cutting force of the workpiece material, the cutting load index at each moment is obtained; based on the cutting load index at each moment, the boring tool machining time period is divided into several cutting time periods, and the load change period is selected; based on the cutting load index at each moment of the load change period and its adjacent cutting time period and the spindle load current, the current response deviation of the load change period is obtained; Based on the current response offset during continuous load change periods, a scatter plot of wear trend during load change periods is constructed; based on the scatter plot of wear trend during load change periods, the wear trend coefficient of load change periods is obtained, and then the wear index of load change periods is obtained. Obtain the wear index of all load change periods of the historical boring tool. Based on the wear index of all load change periods of the historical boring tool, obtain the boring tool break-in reference value and the boring tool failure reference value. Combine the wear index of all load change periods of the current boring tool to obtain the wear degree of the current boring tool.

2. The method for monitoring roughing and finishing boring tool wear based on spindle load current according to claim 1, characterized in that, The method for obtaining the cutting load index at each moment based on the spindle speed, boring tool feed rate, boring tool cutting edge width, blank hole depth, and unit cutting force of the workpiece material includes the following specific methods: For any given time, the cutting load index at that time is positively correlated with the spindle speed at that time; The cutting load index at that moment is positively correlated with the boring tool feed rate at that moment; The cutting load index at the specified moment is positively correlated with the blank hole depth; The cutting load index at the specified moment is positively correlated with the unit cutting force of the workpiece material; The cutting load index at the specified moment is negatively correlated with the boring tool cutting edge width.

3. The method for monitoring roughing and finishing boring tool wear based on spindle load current according to claim 1, characterized in that, The method for dividing the boring tool machining time into several cutting periods based on the cutting load index at each moment, and screening out periods of sudden load changes, includes the following specific methods: Based on the cutting load index at all times during the boring tool machining period, the boring tool machining period is divided into several cutting periods using the variable point grouping method. For any cutting period, the average value of the cutting load index at all times during the cutting period is recorded as the baseline cutting load level for the cutting period. If the difference between the baseline cutting load level of the cutting period and the baseline cutting load level of the previous cutting period is greater than the preset difference threshold of the cutting period, then the cutting period is regarded as the load change period.

4. The method for monitoring roughing and finishing boring tool wear based on spindle load current according to claim 3, characterized in that, The method for obtaining the current response offset during the load abrupt change period based on the cutting load index and spindle load current at each moment in the load abrupt change period and its adjacent cutting periods includes the following specific methods: For any time within any load change period, the average value of the cutting load index at all times within the cutting period adjacent to the load change period is denoted as the comparative cutting load degree of the load change period. The average value of the spindle load current at all times during the cutting period adjacent to the load change period is recorded as the comparative spindle load current value during the load change period. The difference between the spindle load current at the moment of the load change period and the comparative spindle load current value during the load change period is denoted as the spindle load current offset factor at the moment of the load change period. The difference between the cutting load index at the moment of the load change period and the comparative cutting load level during the load change period is denoted as the cutting load offset factor at the moment of the load change period. The sum of the ratios of the spindle load current offset factor to the cutting load offset factor at all times during the load abrupt change period is linearly normalized, and the normalized result is used as the current response offset during the load abrupt change period.

5. The method for monitoring roughing and finishing boring tool wear based on spindle load current according to claim 1, characterized in that, The specific method for constructing a scatter plot of wear trends during load abrupt changes based on the current response offset during continuous load abrupt change periods includes: For any load mutation period, a preset number of preceding load mutation periods is defined. The period before the load mutation Each period of load mutation is denoted as the preceding load mutation period; A rectangular coordinate system is constructed with time as the horizontal axis and the current response offset during the load change period as the vertical axis. Based on the last moment of each preceding load change period and the current response offset, each preceding load change period is taken as a data point and placed into the rectangular coordinate system to obtain a scatter plot of the wear trend during the load change period.

6. The method for monitoring roughing and finishing boring tool wear based on spindle load current according to claim 1, characterized in that, The specific method for obtaining the wear trend coefficient during the load change period based on the wear trend scatter plot during the load change period is as follows: For any load change period, the RANSAC algorithm is used to fit a straight line to the scatter plot of the wear trend during the load change period. The fitted straight line is recorded as the wear evolution trend line of the load change period, and the slope of the wear evolution trend line of the load change period is used as the wear trend coefficient of the load change period.

7. The method for monitoring roughing and finishing boring tool wear based on spindle load current according to claim 6, characterized in that, The specific method for obtaining the wear index during the period of load abrupt change is as follows: Record any data point in the scatter plot of the wear trend during the load mutation period as the target point, and obtain the contribution weight of the target point based on the distance between the target point and the wear evolution trend line during the load mutation period in the vertical direction. The contribution weight of the target point is negatively correlated with the distance between the target point and the wear evolution trend line during the load change period in the vertical axis direction; The product of the contribution weight of the target point and the current response offset of the target point is used as the wear factor of the target point. The sum of the wear factors of all data points in the wear trend scatter plot during the load abrupt change period is taken as the wear response coefficient during the load abrupt change period. The wear index of the load abrupt change period is obtained by multiplying half the duration of the wear trend scatter plot corresponding to the load abrupt change period by the wear trend coefficient of the load abrupt change period, and then adding the wear response coefficient of the load abrupt change period to the product.

8. The method for monitoring roughing and finishing boring tool wear based on spindle load current according to claim 1, characterized in that, The method for obtaining the boring tool break-in reference value and boring tool failure reference value based on the wear index of all load change periods of the historical boring tool includes the following specific methods: Retrieve the wear index of each historical boring tool during all periods of load abrupt change in its service life from the database; for any historical boring tool, sort the wear index of the historical boring tool during all periods of load abrupt change in its service life according to the corresponding time to obtain the wear index sequence of the historical boring tool during its service life; The Ruptures algorithm is used to obtain the two inflection points with the largest rate of change in the wear index sequence of the historical boring tool during its service life. The wear index corresponding to the first inflection point is recorded as the running-in coefficient of the historical boring tool, and the wear index corresponding to the second inflection point is recorded as the failure critical coefficient of the historical boring tool. The average of the break-in coefficients of all historical boring tools is used as the benchmark value for boring tool break-in. Based on the failure critical coefficients of all historical boring tools, and combined with the Weibull distribution estimation method, the percentage is estimated. The wear index threshold at which the boring tool reaches failure is used as the benchmark value for boring tool failure. This represents the preset percentage of allowed failures.

9. The method for monitoring roughing and finishing boring tool wear based on spindle load current according to claim 1, characterized in that, The specific method for obtaining the current wear degree of the boring tool is as follows: The Ruptures algorithm is used to obtain the two inflection points with the largest rate of change in the wear index sequence of the current boring tool's service life, and the wear index corresponding to the first inflection point is recorded as the running-in coefficient of the current boring tool. Based on the current boring bar's break-in coefficient, the wear index of the current boring bar during the most recent period of load change, and combined with the boring bar's break-in reference value and the boring bar's failure reference value, the current wear degree of the boring bar is obtained. The wear degree of the current boring tool is positively correlated with the wear index of the current boring tool during the most recent period of load change; The current wear level of the boring tool is positively correlated with the boring tool break-in reference value; The wear degree of the current boring tool is negatively correlated with the break-in coefficient of the current boring tool; The current wear level of the boring tool is negatively correlated with the boring tool failure reference value.

10. A roughing and finishing boring tool wear monitoring system based on spindle load current, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the computer program is executed by the processor, it implements the steps of the roughing and finishing boring tool wear monitoring method based on spindle load current as described in any one of claims 1-9.

Images