A machining method for engine shaft parts using a numerically controlled machine tool

Abstract

This application relates to the technical field of machine tool part processing, and specifically relates to a method for processing engine shaft parts using a numerical control machine tool. The method includes: obtaining the vibration data and rotational speed data of the tool of the numerical control machine tool at each moment during each cutting; determining the contact impact strength, vibration offset, vibration fluctuation degree, and wear influence coefficient for each cutting; determining the synchronous change coefficient, cutting state abnormality degree, and adjustment factor for the current adjustment cycle, determining the steepness parameter of the jerk equation in the S-shaped acceleration and deceleration algorithm for the next adjustment cycle, and planning the feed speed of the tool in the numerical control machine tool. This application smooths the feed speed of the tool according to different cutting states, realizes smooth acceleration and deceleration, improves the stability and efficiency in the numerical control processing process, and improves the machining accuracy of engine shaft parts.

Description

Technical Field

[0001] This application relates to the technical field of machine tool part processing, and specifically relates to a processing method for engine shaft parts using a numerical control machine tool. Background Technique

[0002] In the field of modern industrial manufacturing, engine shaft parts, as key mechanical components, their accuracy and performance are directly related to the reliability and efficiency of the entire mechanical equipment. Using a numerical control machine tool to process engine shaft parts has become an efficient and precise production method. Through pre-set program control, the numerical control machine tool can achieve precise processing of complex shapes while maintaining high repeatability and high production efficiency.

[0003] During the processing, the precise adjustment and control of the feed speed of the numerical control machine tool are important links to ensure the processing quality of engine shaft parts, and are closely related to the machining dimensional accuracy, geometric tolerances, surface roughness, and production efficiency. The existing numerical control machine tools commonly use the S-shaped acceleration and deceleration algorithm to control the feed speed of the tool. In the actual processing process, it may be affected by tool wear and changes in cutting force, resulting in difficulty in performing more precise smooth control with the conventional S-shaped acceleration and deceleration algorithm, and the machining accuracy of parts still needs to be improved. Summary of the Invention

[0004] In order to solve the above technical problems, a processing method for engine shaft parts using a numerical control machine tool is provided to solve the existing problems.

[0005] The solution of this application to solve the technical problem is to provide a processing method for engine shaft parts using a numerical control machine tool, including the following steps:

[0006] Obtain the vibration data and rotational speed data of the tool of the numerical control machine tool at each moment during each cutting; divide all moments during each cutting into a contact impact period and a cutting processing period;

[0007] According to the difference in vibration data between the contact impact period and the cutting processing period, determine the contact impact strength of each cutting; according to the fluctuation intensity of the wave peaks of the vibration data within the cutting processing period, determine the vibration offset of each cutting; analyze the difference in vibration data between adjacent wave peaks within the cutting processing period, and the time interval between adjacent wave peaks, determine the vibration fluctuation of each cutting; based on the vibration offset, the vibration fluctuation, and the contact impact strength, determine the wear influence coefficient of each cutting;

[0008] Preset each adjustment period; determine the synchronous change coefficient of the current adjustment period according to the difference between the frequency and the rotational speed of the vibration data at each cutting in the current adjustment period in the frequency domain; determine the cutting state abnormality degree of the current adjustment period according to the change trend and the discrete situation of the wear influence coefficient in the current adjustment period, and combine the synchronous change coefficient to obtain the adjustment factor of the current adjustment period;

[0009] Based on the adjustment factor of the current adjustment period, determine the steepness parameter of the jerk equation in the S-curve acceleration and deceleration algorithm for the next adjustment period, and plan the feed speed of the tool in the CNC machine tool.

[0010] Preferably, the method for obtaining the contact impact period and the cutting processing period is as follows:

[0011] Perform mutation detection on the vibration data at all times during each cutting to obtain the segmentation points; based on the segmentation points, divide the vibration data at all times during each cutting into a contact impact period and a cutting processing period.

[0012] Preferably, determining the contact impact strength of each cutting includes:

[0013] Calculate the mean value and the standard deviation of the vibration data at all times during the contact impact period, and denote them as the first mean value and the first standard deviation;

[0014] Calculate the mean value and the standard deviation of the vibration data at all times during the cutting processing period, and denote them as the second mean value and the second standard deviation;

[0015] Denote the difference between the first mean value and the second mean value as the first difference; denote the difference between the first standard deviation and the second standard deviation as the second difference;

[0016] The contact impact strength is the product of the first difference and the second difference.

[0017] Preferably, determining the vibration offset of each cutting includes:

[0018] Obtain the wave peaks of the vibration data at all times during the cutting processing period during each cutting;

[0019] Take the mean value of the vibration data at all times except the moments corresponding to the wave peaks during the cutting processing period as the basic vibration amount of each cutting;

[0020] Calculate the difference value between the peak value corresponding to each wave peak and the basic vibration amount, and take the mean value of the difference values of all wave peaks during the cutting processing period as the vibration offset of each cutting.

[0021] Preferably, determining the vibration fluctuation degree of each cutting includes:

[0022] Denote the difference between the peak value of each peak and the peak value of its adjacent peak during the cutting process as the peak difference of each peak.

[0023] Calculate the time interval between the moment corresponding to each peak and the corresponding moment of its adjacent peak during the cutting process.

[0024] Calculate the ratio result of the peak difference of each peak to the time interval, and take the sum of the ratio results of all peaks during the cutting process for each cutting as the vibration fluctuation degree of each cutting.

[0025] Preferably, determining the wear influence coefficient of each cutting includes:

[0026] Calculate the product of the vibration offset and the vibration fluctuation degree, and denote it as the first product.

[0027] Take the sum of the contact impact strength and the first product as the wear influence coefficient of each cutting.

[0028] Preferably, determining the synchronous change coefficient of the current adjustment period includes:

[0029] Perform frequency domain analysis on the vibration data at all moments during each cutting to obtain a frequency spectrum diagram; take the frequency corresponding to the maximum amplitude in the frequency spectrum diagram as the vibration main frequency of each cutting.

[0030] Calculate the mean value of the rotational speed data at all moments during each cutting as the average rotational speed of each cutting.

[0031] The synchronous change coefficient is the difference between the vibration main frequency and the average rotational speed for all cuttings within the current adjustment period.

[0032] Preferably, determining the cutting state abnormality degree of the current adjustment period includes:

[0033] Number each cutting process within the current adjustment period in chronological order starting from serial number 1; form a two-dimensional array with the serial number corresponding to each cutting within the current adjustment period and its corresponding wear influence coefficient.

[0034] Obtain the slope of the fitting line after linear fitting of all the two-dimensional arrays within the current adjustment period.

[0035] Calculate the dispersion degree of the wear influence coefficients of all cuttings within the current adjustment period.

[0036] Calculate the product of the absolute value of the slope and the dispersion degree, and denote it as the second product. Take the ratio of the second product to the synchronous change coefficient as the cutting state abnormality degree of the current adjustment period.

[0037] Preferably, the adjustment factor for the current adjustment period has the following calculation formula: , where is the abnormality degree of the cutting state in the current adjustment period, is the logarithmic function with base 10.

[0038] Preferably, the steepness parameter of the jerk equation in the S-curve acceleration and deceleration algorithm for the next adjustment period includes:

[0039] The original jerk curve in the S-curve acceleration and deceleration algorithm of the CNC machine tool is transformed using the Sigmoid function to obtain the transformed jerk equation;

[0040] The difference between the steepness parameter of the transformed jerk equation in the current adjustment period and the adjustment factor is used as the steepness parameter of the transformed jerk equation in the next adjustment period.

[0041] This application has at least the following beneficial effects:

[0042] Based on the difference in vibration data between the contact impact period and the cutting period, the contact impact intensity of each cutting is determined. The beneficial effect is that the vibration data at all times during each cutting is divided into two periods, and the difference in vibration data between different periods is considered to reflect the degree of contact impact generated when the tool contacts the part, and further reflect the wear condition of the tool in the CNC machine tool; according to the fluctuation intensity of the peaks in the vibration data during the cutting period, the vibration offset of each cutting is determined; by analyzing the difference in vibration data between adjacent peaks and the interval time between corresponding moments of adjacent peaks during the cutting period, the vibration fluctuation degree of each cutting is determined. Based on the vibration offset, the vibration fluctuation degree, and the contact impact intensity, the wear influence coefficient of each cutting is determined. The beneficial effect is that the abnormal vibration condition of the tool during the cutting period is considered to reflect the influence of tool wear or cutting force; according to the difference between the frequency and the rotational speed in the frequency domain corresponding to the vibration data of each cutting in the current adjustment period, the synchronous change coefficient of the current adjustment period is determined. The beneficial effect is that the synchronism between the vibration data and the rotational speed change is considered to reflect the tool processing state of the CNC machine tool; according to the change trend and discreteness of the wear influence coefficient in the current adjustment period, combined with the synchronous change coefficient, the cutting state abnormality degree of the current adjustment period is determined. The beneficial effect is that the change trend of the machining process affected by the tool wear degree is considered, combined with the synchronous change of the vibration data and the rotational speed change, to further reflect the cutting state of the CNC machine tool during the machining process and accurately evaluate the tool cutting state during the current CNC machining; based on the cutting state abnormality degree, the adjustment factor of the current adjustment period is determined, the jerk curve in the S-curve acceleration and deceleration algorithm of the CNC machine tool in the current adjustment period is transformed, and according to the difference between the steepness parameter in the transformed jerk equation and the adjustment factor in the current adjustment period, the steepness parameter of the jerk equation in the next adjustment period is determined to plan the feed speed of the tool in the CNC machine tool. The beneficial effect is that based on the cutting state abnormality degree, the jerk of the S-curve acceleration and deceleration algorithm is adjusted, and the feed speed of the tool is smoothed according to different cutting states to achieve smooth acceleration and deceleration, improve the smoothness and efficiency in the CNC machining process, and improve the machining accuracy of the engine shaft parts. Description of the Drawings

[0043] The following further elaborates in detail a method for machining engine shaft parts using a CNC machine tool according to the present application with reference to the drawings.

[0044] Figure 1 It is a step flowchart of a method for machining engine shaft parts using a CNC machine tool provided by an embodiment of the present application;

[0045] Figure 2It is a flowchart of the steps for the method of obtaining the wear influence coefficient for each cutting provided by the embodiment of the present application;

[0046] Figure 3 It is a flowchart of the steps for the method of obtaining the abnormality degree of the cutting state in the current adjustment cycle provided by the embodiment of the present application. Detailed implementation manners

[0047] In order to make the objectives, technical solutions and advantages of the present application clearer, the following further elaborates in detail a method for machining engine shaft parts using a numerically controlled machine tool proposed by the present application in combination with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs.

[0049] Please refer to Figure 1 , which shows a flowchart of the steps for a method of machining engine shaft parts using a numerically controlled machine tool provided by an embodiment of the present application. The method includes the following steps:

[0050] Step 1, obtain the vibration data and rotational speed data of the tool of the numerically controlled machine tool at each moment during each cutting.

[0051] In actual machining production of a numerically controlled machine tool, the machine tool performs cutting machining on parts according to the set machining program. In order to improve the cutting efficiency and machining accuracy of the machine tool, it is necessary for the numerically controlled machine tool to adjust the cutting speed in real time according to the actual machining state to adapt to various changes occurring during the cutting process.

[0052] During the cutting process, the vibration of the tool has a significant impact on the machining accuracy. When the numerically controlled machine tool is in production machining, the tool will come into contact with the part surface multiple times, that is, there are multiple tool feed controls. Each time the tool is fed, the part will be cut once, and then the tool will vibrate. Therefore, a vibration sensor and a rotational speed sensor are installed at the feed axis where the tool is located to collect the vibration generated by the tool and the rotational speed of the tool during each cutting process. Set the acquisition frequency of the sensor to f, and perform normalization processing on the acquired data to obtain the vibration data and rotational speed data at each moment during each cutting process.

[0053] Preferably, in this embodiment, the acquisition frequency of the sensor is set to 500 Hz. As other implementation manners, the implementer can set it according to the actual situation. Secondly, the maximum-minimum normalization method is used for normalization processing. As other implementation manners, the implementer can use other methods in the prior art, such as the Z-score normalization method, etc. This embodiment does not make special limitations on this.

[0054] So far, the vibration data and rotational speed data of the tool of the CNC machine tool at each moment during each cutting are obtained.

[0055] Step 2: Determine the contact impact strength of each cutting according to the difference in vibration data between the contact impact period and the cutting period; determine the vibration offset of each cutting according to the fluctuation strength of the wave peaks in the vibration data during the cutting period; analyze the difference in vibration data between adjacent wave peaks and the interval time between adjacent wave peaks during the cutting period to determine the vibration fluctuation of each cutting; determine the wear influence coefficient of each cutting based on the vibration offset, the vibration fluctuation, and the contact impact strength.

[0056] Engine shaft parts, such as crankshafts and transmission shafts, are core components in engines. When machining these parts, precise and stable tool feed speeds are required for production. Therefore, in the feed system of CNC machine tools, it is crucial to achieve smoother acceleration and deceleration control to ensure the machining accuracy and quality of shaft parts.

[0057] During the production and machining of engine shaft parts by CNC machine tools, the machining tool used is a face milling cutter. Usually, multiple cutting edges are contained in the face milling cutter. Under the influence of the face milling cutter structure, the cutting edges are always in intermittent contact with the workpiece, and different degrees of vibration are generated during cutting. If the feed speed is adjusted improperly, it is easy to cause abnormal vibration during the machining process, and the tool wear and cutting force will also affect the machining accuracy of the parts. The CNC machine tool needs to adjust the tool feed speed in a timely manner according to the actual machining state.

[0058] When machining different parts of the crankshaft in the engine, the external milling of the crankshaft journal and the connecting rod journal is an important link, and multiple feed cuttings are required. The cutting forces of the milling cutters for different machining parts may be different, and as the tool wears continuously, different degrees of abnormal vibration are likely to occur. During each cutting, when the milling cutter just contacts the workpiece surface for a period of time, a strong contact impact will be generated, and the vibration data during this period is generally large. After the contact impact ends, the vibration data during cutting suddenly decreases. Therefore, the vibration data during each cutting shows a certain step characteristic. If the tool wear is greater and the cutting force is greater, the abnormal vibration generated may be more obvious. Compared with the vibration data in the normal cutting state, the abnormal vibration of the tool will make the fluctuation difference of the vibration data in different step periods larger, and after the contact impact ends, the deviation degree of the wave peaks of the vibration data during cutting is larger.

[0059] Based on the above analysis, the collected vibration data is divided to distinguish two gradient periods: the contact impact period when the milling cutter just contacts the workpiece surface and the cutting period after the contact impact ends. Specifically:

[0060] Perform mutation detection on the vibration data at all times during each cutting to obtain segmentation points;

[0061] Based on the segmentation points, divide the vibration data at all times during each cutting into a contact impact period and a cutting process period;

[0062] Preferably, in this embodiment, the Bernaola Galvan segmentation algorithm is used to obtain the segmentation points. Among them, the Bernaola Galvan segmentation algorithm is a well-known technology and will not be elaborated here. As other implementation manners, implementers can adopt other methods of existing technologies, such as Pettitt mutation point detection, etc. This embodiment does not make special restrictions on this.

[0063] Calculate the mean and standard deviation of the vibration data at all times during the contact impact period, denoted as the first mean and the first standard deviation;

[0064] Calculate the mean and standard deviation of the vibration data at all times during the cutting process period, denoted as the second mean and the second standard deviation;

[0065] Denote the difference between the first mean and the second mean as the first difference;

[0066] Denote the difference between the first standard deviation and the second standard deviation as the second difference;

[0067] Preferably, in this embodiment, denote the absolute value of the difference between the first mean and the second mean as the first difference; denote the absolute value of the difference between the first standard deviation and the second standard deviation as the second difference.

[0068] Take the product of the first difference and the second difference as the contact impact intensity of each cutting;

[0069] Preferably, in this embodiment, the calculation formula for the contact impact intensity of each cutting is: , where, is the contact impact intensity of the th cutting, is the mean of the vibration data at all times during the contact impact period of the th cutting, that is, the first mean, is the mean of the vibration data at all times during the cutting process period of the th cutting, that is, the second mean, is the standard deviation of the vibration data at all times during the contact impact period of the th cutting, that is, the first standard deviation, is the The standard deviation of the vibration data at all times during the cutting process of the secondary cutting, i.e., the second standard deviation; secondly, is the first difference, is the second difference.

[0070] It should be noted that the greater the difference in the central distribution trend or fluctuation of the vibration data between the contact impact period and the cutting process period, the greater the abnormal vibration generated by cutting, and the greater the contact impact strength, indicating that the contact impact generated when the tool contacts the part is greater.

[0071] Furthermore, the step flow chart of the method for obtaining the wear influence coefficient for each cutting provided in the embodiments of the present application is as Figure 2 shown.

[0072] First, analyze the deviation of the vibration data during the cutting process period, specifically:

[0073] Obtain the peaks of the vibration data at all times during the cutting process period for each cutting;

[0074] Preferably, in this embodiment, the Automatic multiscale-based peak detection (AMPD) algorithm is used to obtain the peaks. The automatic multiscale-based peak detection algorithm is a well-known technology and will not be elaborated here. As other implementation manners, implementers can use other methods of the prior art, such as the difference method, etc. This embodiment does not make special limitations on this.

[0075] Take the mean value of the vibration data at all times other than the times corresponding to the peaks during the cutting process period as the basic vibration amount for each cutting;

[0076] Calculate the difference value between the peak value corresponding to each peak and the basic vibration amount, and take the mean value of the difference values of all peaks during the cutting process period for each cutting as the vibration offset amount for each cutting;

[0077] Preferably, in this embodiment, calculate the absolute value of the difference between the peak value corresponding to each peak and the basic vibration amount; take the mean value of the absolute values of all peaks during the cutting process period for each cutting as the vibration offset amount for each cutting.

[0078] It should be noted that the basic vibration amount is the vibration generated by inevitable situations during the cutting process. When the peak value of the peak deviates more from the basic vibration amount, there is more likely to be abnormal vibration. Therefore, the greater the obtained vibration offset amount, the greater the deviation degree of the abnormal vibration situation in the vibration data compared to the basic vibration amount, and the greater the possibility of abnormal vibration.

[0079] Further, by analyzing the differences between adjacent wave peaks and the high-frequency occurrence of peaks, the abnormal vibration condition of the tool in the CNC machine tool is reflected, specifically as follows:

[0080] The difference between the peak value of each wave peak in the cutting period and the peak value of its previous wave peak is recorded as the peak difference of each wave peak.

[0081] Preferably, in this embodiment, the absolute value of the difference between the peak value of each wave peak in the cutting period and the peak value of its previous wave peak is recorded as the peak difference of each wave peak.

[0082] Calculate the time interval between the moment corresponding to each wave peak in the cutting period and the corresponding moment of its previous wave peak.

[0083] Calculate the ratio of the peak difference of each wave peak to the time interval, and take the sum of the ratios of all wave peaks in the cutting period for each cutting as the vibration fluctuation degree for each cutting.

[0084] It should be noted that the smaller the time interval, the higher the frequency of wave peak occurrence, and the greater the obtained vibration fluctuation degree, indicating that the vibration change of the tool in the CNC machine tool is more irregular and the frequency of occurrence is higher.

[0085] Further, based on the contact impact strength, the vibration offset, and the vibration fluctuation degree, a wear influence coefficient is determined, specifically as follows:

[0086] Calculate the product of the vibration offset and the vibration fluctuation degree, which is recorded as the first product, and take the sum of the contact impact strength and the first product as the wear influence coefficient for each cutting.

[0087] It should be noted that the larger the vibration offset and the vibration fluctuation degree, the greater the possibility of abnormal vibration of the tool, and the greater the impact on the tool wear or cutting force. The greater the contact impact strength, the greater the contact impact generated when the tool contacts the part, resulting in a higher degree of tool wear, and the greater the obtained wear influence coefficient, indicating that each cutting in the machining process is more likely to be affected by tool wear or cutting force.

[0088] Thus, the wear influence coefficient for each cutting is obtained.

[0089] Step 3: Preset each adjustment period; determine the synchronous change coefficient of the current adjustment period according to the difference between the frequency and the rotational speed of the vibration data for each cutting in the current adjustment period in the frequency domain; determine the cutting state abnormality degree of the current adjustment period based on the change trend and the discrete situation of the wear influence coefficient in the current adjustment period, in combination with the synchronous change coefficient.

[0090] Furthermore, in addition to the crankshaft journals and connecting rod journals of the engine crankshaft, it also includes multiple parts such as cranks and crank throws. Due to different machining technical requirements, different milling cutter speeds need to be set. In a good machining state, the change in the milling cutter speed has little effect on the vibration of the tool; when the machining state is poor, since the milling cutter rotates periodically, then as the rotation speed changes, the frequency of abnormal vibration will also change synchronously.

[0091] Based on the above analysis, by analyzing the synchronization of the vibration data and the rotational speed data changes, the synchronization coefficient is determined, specifically as follows:

[0092] Perform frequency domain analysis on the vibration data at all times during each cutting to obtain a frequency spectrum diagram;

[0093] Preferably, in this embodiment, the discrete Fourier transform is used to obtain the frequency spectrum diagram. Among them, the discrete Fourier transform is a well-known technology and will not be elaborated here. As other implementation manners, the implementer can use other methods of the existing technology, for example, the fast Fourier transform, etc. This embodiment does not make special restrictions on this.

[0094] Take the frequency corresponding to the maximum amplitude in the frequency spectrum diagram as the main vibration frequency of each cutting;

[0095] Calculate the mean value of the rotational speed data at all times during each cutting as the average rotational speed of each cutting;

[0096] Record each cutting and the previous multiple cutting processes as an adjustment cycle;

[0097] Preferably, in this embodiment, each cutting and the previous 7 cutting processes are recorded as an adjustment cycle. As other implementation manners, the implementer can set it according to the actual situation.

[0098] Take the difference between the main vibration frequency and the average rotational speed of all cuttings within the current adjustment cycle as the synchronization change coefficient of the current adjustment cycle;

[0099] Preferably, in this embodiment, the DTW distance between the main vibration frequency and the average rotational speed of all cuttings within the current adjustment cycle is taken as the synchronization change coefficient of the current adjustment cycle.

[0100] It should be noted that the smaller the synchronization change coefficient, the more synchronous the change between the vibration of the tool and the rotational speed, which means that when the rotational speed of the milling cutter changes, it will affect the change of the tool vibration, and further reflects that the machining state of the tool of the CNC machine tool is poor.

[0101] Furthermore, during the machining process of the machine tool, due to multiple cutting operations, the temperature of the cutting tool gradually increases, which may have an adverse impact on the quality of the machined parts. If the machining state is poor, affected by improper control of the feed speed of the cutting tool during machine tool machining and increased tool wear, the possibility of abnormal vibration data during the cutting process becomes greater and greater, specifically manifested in the fluctuation and overall change trend of the wear influence coefficient, and at the same time, there is a synchronous change between the main vibration frequency and the rotational speed.

[0102] Based on the above analysis, by analyzing the change trend of the wear influence coefficient and the synchronous change coefficient within the current adjustment period, the cutting state abnormality degree is determined to reflect the cutting state during the machining of the CNC machine tool, specifically as follows:

[0103] Number each cutting process within the current adjustment period in chronological order from serial number 1; form a two-dimensional array with the serial number corresponding to each cutting within the current adjustment period and its corresponding wear influence coefficient;

[0104] Perform linear fitting on all the two-dimensional arrays within the current adjustment period to obtain the slope of the fitting line;

[0105] Preferably, in this embodiment, the least squares method is used for linear fitting. Among them, the least squares method is a well-known technology and will not be elaborated here. As other implementation manners, implementers can adopt other methods of existing technologies, such as the maximum likelihood estimation method, etc. This embodiment does not make special restrictions on this.

[0106] Calculate the dispersion degree of the wear influence coefficients of all cuttings within the current adjustment period;

[0107] Preferably, in this embodiment, calculate the information entropy of the wear influence coefficients of all cuttings within the current adjustment period. Among them, the calculation of information entropy is a well-known technology and will not be elaborated here. As other implementation manners, implementers can adopt other methods of existing technologies, such as the coefficient of variation, variance, standard deviation, etc. This embodiment does not make special restrictions on this.

[0108] Calculate the product of the absolute value of the slope and the dispersion degree, denoted as the second product, and take the ratio of the second product to the synchronous change coefficient as the cutting state abnormality degree of the current adjustment period;

[0109] Preferably, in this embodiment, the calculation method of the cutting state abnormality degree of the current adjustment period is: , where is the cutting state abnormality degree of the current adjustment period, is the absolute value of the slope of the current adjustment period, is the information entropy of the wear influence coefficients of all cuttings within the current adjustment period, that is, the dispersion degree, is the synchronous change coefficient of the current adjustment cycle, is a preset value greater than 0 to avoid the denominator being 0. In this embodiment, takes the value of 0.01; The flowchart of the steps for obtaining the cutting state abnormality degree of the current adjustment cycle provided in this embodiment is as Figure 3 shown.

[0110] It should be noted that the greater the absolute value of the slope, the more obvious the change trend of the wear influence coefficient, and the greater the influence of the tool wear degree on the machining process. Secondly, the greater the degree of dispersion, the more different wear influence degrees during multiple cuttings, which further indicates that the tool state fluctuates; Secondly, the smaller the synchronous change coefficient, the more synchronous the vibration of the tool and the rotational speed, the worse the machining state of the CNC machine tool, and the greater the obtained cutting state abnormality degree, indicating that the cutting state during the current CNC machine tool machining is worse.

[0111] Thus, the cutting state abnormality degree of the current adjustment cycle is obtained.

[0112] Step 4, based on the cutting state abnormality degree, determine the adjustment factor of the current adjustment cycle. Based on the adjustment factor of the current adjustment cycle, determine the steepness parameter of the jerk equation in the S-curve acceleration and deceleration algorithm of the next adjustment cycle, and plan the feed speed of the tool in the CNC machine tool.

[0113] Based on the above analysis, the cutting state at different times is judged through the vibration data during the machining process of shaft parts. If the influence of tool wear or cutting force during the machining process is greater, the cutting state abnormality degree is greater, and it is more likely to affect the accuracy of the machined parts. Therefore, the influence caused by tool wear or cutting force can be reduced by increasing the smoothness of the tool feed speed.

[0114] Use the Sigmoid function to transform the original jerk curve in the S-curve acceleration and deceleration algorithm of the CNC machine tool to obtain the transformed jerk equation;

[0115] It should be noted that the method of using the Sigmoid function to transform the original jerk curve in the S-curve acceleration and deceleration algorithm is a well-known technology and will not be elaborated here.

[0116] Furthermore, the magnitude of the steepness parameter in the transformed jerk equation will affect the smoothness of the tool feed speed. Therefore, when the cutting state abnormality degree is greater, in order to achieve smoother control of the tool feed speed, it is necessary to reduce the steepness parameter in the jerk equation. Therefore, based on the cutting state abnormality degree, determine the adjustment factor to smooth the feed speed during the machining process of the CNC machine tool. Specifically:

[0117] The calculation formula for the adjustment factor of the current adjustment cycle is as follows: , where is the adjustment factor of the current adjustment cycle, is the abnormality degree of the cutting state in the current adjustment cycle, is the logarithmic function with base 10.

[0118] Based on the adjustment factor of the current adjustment cycle, determine the steepness parameter of the jerk equation in the S-curve acceleration and deceleration algorithm for the next adjustment cycle to smooth the feed speed during the machining process of the CNC machine tool. Specifically:

[0119] Take the difference between the steepness parameter of the transformed jerk equation in the current adjustment cycle and the adjustment factor as the steepness parameter of the transformed jerk equation in the next adjustment cycle.

[0120] The CNC machine tool plans the feed speed of the tool in the CNC machine tool according to the jerk equation, realizes smooth acceleration and deceleration, thereby controlling the feed speed of the tool, improving the smoothness and efficiency during the CNC machining process, and improving the machining accuracy of engine shaft parts.

[0121] It should be understood that although Figure 1 the steps in the flowchart of Figure 1 are shown in sequence according to the arrows, these steps do not necessarily execute in the order indicated by the arrows. Unless there is a clear indication in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders. Moreover,

[0122] At least a part of the steps in

[0123] may include multiple sub-steps or multiple stages. These sub-steps or stages do not necessarily execute at the same time, but can execute at different times. The execution order of these sub-steps or stages is not necessarily sequential either, but can execute alternately or in turn with at least a part of other steps or sub-steps or stages of other steps. The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combinations of these technical features do not conflict, they should all be considered as the scope described in this specification.The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made. Therefore, any simple modification, equivalent change, and decoration made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application all fall within the protection scope of the technical solution of the present application.

Claims

1. A machining method for engine shaft parts using a numerically controlled machine tool, characterized in that, The method includes the following steps: Obtain the vibration data and rotational speed data of the tool of the numerical control machine tool at each moment during each cutting; divide all moments during each cutting into a contact impact period and a cutting processing period; Determine the contact impact intensity of each cutting according to the difference in vibration data between the contact impact period and the cutting processing period; determine the vibration offset of each cutting according to the fluctuation intensity of the wave peaks in the vibration data during the cutting processing period; analyze the difference in vibration data between adjacent wave peaks and the time interval between adjacent wave peaks during the cutting processing period to determine the vibration fluctuation of each cutting; based on the vibration offset, the vibration fluctuation, and the contact impact intensity, determine the wear influence coefficient of each cutting; Preset each adjustment period; determine the synchronous change coefficient of the current adjustment period according to the difference between the frequency and the rotational speed of the vibration data of each cutting in the frequency domain during the current adjustment period; according to the change trend and discreteness of the wear influence coefficient during the current adjustment period, and in combination with the synchronous change coefficient, determine the cutting state abnormality degree of the current adjustment period to obtain the adjustment factor of the current adjustment period; Based on the adjustment factor of the current adjustment period, determine the steepness parameter of the jerk equation in the S-curve acceleration and deceleration algorithm of the next adjustment period to plan the feed speed of the tool in the numerical control machine tool.

2. The machining method of engine shaft parts using a numerical control machine tool according to claim 1, characterized in that, The method for obtaining the contact impact period and the cutting processing period is as follows: Perform mutation detection on the vibration data of all moments during each cutting to obtain the segmentation points; based on the segmentation points, divide the vibration data of all moments during each cutting into a contact impact period and a cutting processing period.

3. A machining method for engine shaft parts using a numerical control machine tool according to claim 1, characterized in that, The determination of the contact impact intensity of each cutting includes: Calculate the mean value and standard deviation of the vibration data of all moments during the contact impact period, denoted as the first mean value and the first standard deviation; Calculate the mean value and standard deviation of the vibration data of all moments during the cutting processing period, denoted as the second mean value and the second standard deviation; Denote the difference between the first mean value and the second mean value as the first difference; denote the difference between the first standard deviation and the second standard deviation as the second difference; The contact impact intensity is the product of the first difference and the second difference.

4. A machining method for engine shaft parts using a numerical control machine tool according to claim 1, characterized in that, The determination of the vibration offset of each cutting includes: Obtain the wave peaks of the vibration data of all moments during the cutting processing period of each cutting; Take the mean value of the vibration data of all moments except the moments corresponding to the wave peaks during the cutting processing period as the basic vibration amount of each cutting; Calculate the difference value between the peak value corresponding to each wave peak and the basic vibration amount, and take the mean value of the difference values of all wave peaks during the cutting processing period as the vibration offset of each cutting.

5. A machining method for engine shaft parts using a numerically controlled machine tool according to claim 4, characterized in that The determination of the vibration fluctuation of each cutting includes: Denote the difference between the peak value of each wave peak and the peak value of its adjacent wave peak during the cutting processing period as the peak value difference of each wave peak; Calculate the time interval between the moments corresponding to each wave peak and the corresponding moments of its adjacent wave peaks during the cutting processing period; Calculate the ratio result of the peak difference of each wave peak to the time interval, and take the sum of the ratio results of all wave peaks within the cutting processing period during each cutting as the vibration fluctuation degree of each cutting.

6. A machining method for engine shaft parts using a numerical control machine tool according to claim 1, characterized in that The determination of the wear influence coefficient for each cutting includes: Calculate the product of the vibration offset and the vibration fluctuation degree, denoted as the first product; Take the sum of the contact impact strength and the first product as the wear influence coefficient for each cutting.

7. A machining method for engine shaft parts using a numerical control machine tool according to claim 1, characterized in that, The determination of the synchronous change coefficient for the current adjustment cycle includes: Perform frequency domain analysis on the vibration data at all times during each cutting to obtain a spectrogram; take the frequency corresponding to the maximum amplitude in the spectrogram as the vibration main frequency for each cutting; Calculate the mean value of the rotational speed data at all times during each cutting as the average rotational speed for each cutting; The synchronous change coefficient is the difference between the vibration main frequency and the average rotational speed for all cuttings within the current adjustment cycle.

8. The machining method for engine shaft parts using a numerically controlled machine tool according to claim 1, characterized in that, The determination of the cutting state abnormality degree for the current adjustment cycle includes: Number each cutting process within the current adjustment cycle in chronological order starting from serial number 1; form a two-dimensional array with the serial number corresponding to each cutting within the current adjustment cycle and its corresponding wear influence coefficient; Obtain the slope of the fitted straight line after linear fitting of all the two-dimensional arrays within the current adjustment cycle; Calculate the degree of dispersion of the wear influence coefficients for all cuttings within the current adjustment cycle; Calculate the product of the absolute value of the slope and the degree of dispersion, denoted as the second product, and take the ratio of the second product to the synchronous change coefficient as the cutting state abnormality degree for the current adjustment cycle.

9. A machining method for engine shaft parts using a numerical control machine tool according to claim 1, characterized in that, Adjustment factor for the current adjustment cycle The calculation formula is as follows: , where is the abnormality degree of the cutting state in the current adjustment cycle, is the logarithmic function with base 10.

10. A machining method for engine shaft parts using a numerically controlled machine tool according to claim 1, characterized in that The steepness parameter of the jerk equation in the S-curve acceleration and deceleration algorithm for the next adjustment cycle includes: Use the Sigmoid function to transform the original jerk curve in the S-curve acceleration and deceleration algorithm of the CNC machine tool to obtain the transformed jerk equation; Take the difference between the steepness parameter of the transformed jerk equation in the current adjustment cycle and the adjustment factor as the steepness parameter of the transformed jerk equation in the next adjustment cycle.

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