Engine shaft part machining method using numerical control machine tool

Abstract

The invention relates to the technical field of machine tool part machining, in particular to an engine shaft part machining method utilizing a numerical control machine tool. The method comprises the steps that vibration data and rotating speed data of a cutter of the numerical control machine tool at all moments during cutting each time are obtained; determining the contact impact strength, the vibration offset, the vibration fluctuation degree and the abrasion influence coefficient of each cutting; and determining a synchronous change coefficient, a cutting state abnormity degree and an adjustment factor of the current adjustment period, determining a steep degree parameter of an acceleration equation in the S-shaped acceleration and deceleration algorithm of the next adjustment period, and planning the feeding speed of the cutter in the numerical control machine tool. The feeding speed of the cutter is smoothed according to different cutting states, smooth acceleration and deceleration are achieved, the stability and efficiency in the numerical control machining process are improved, and the machining precision of engine shaft parts is improved.

Description

Technical Field

[0001] The present application relates to the technical field of machine tool parts processing, and in particular to a method for processing engine shaft parts using a numerically controlled machine tool. Background Art

[0002] In the field of modern industrial manufacturing, engine shaft parts are key mechanical components, and their accuracy and performance are directly related to the reliability and efficiency of the entire mechanical equipment. Using CNC machine tools to process engine shaft parts has become an efficient and accurate production method. CNC machine tools can achieve precise processing of complex shapes through preset program control while maintaining high repeatability and high production efficiency.

[0003] During the machining process, the precise adjustment and control of the feed speed of CNC machine tools is an important part of ensuring the machining quality of engine shaft parts, and is closely related to machining dimensional accuracy, geometric tolerance, surface roughness and production efficiency. Existing CNC machine tools often use S-type acceleration and deceleration algorithms to control the feed speed of the tool. The actual machining process may be affected by tool wear and cutting force changes, making it difficult for conventional S-type acceleration and deceleration algorithms to perform more precise and smooth control, 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 method for machining engine shaft parts using a numerically controlled machine tool is provided to solve the existing problems.

[0005] The solution to the technical problem of the present application is to provide a method for machining engine shaft parts using a CNC machine tool, comprising the following steps: Obtaining vibration data and rotation speed data of the tool of the CNC machine tool at each moment of each cutting; dividing all moments of 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 process period; determine the vibration offset of each cutting according to the fluctuation intensity of the peak of the vibration data in the cutting process period; analyze the difference in vibration data between adjacent peaks in the cutting process period and the interval time between adjacent peaks to determine the vibration fluctuation degree of each cutting; determine the wear influence coefficient of each cutting based on the vibration offset, the vibration fluctuation degree and the contact impact intensity; Preset each adjustment cycle; determine the synchronous change coefficient of the current adjustment cycle according to the difference between the frequency and the rotation speed of the vibration data of each cutting in the current adjustment cycle in the frequency domain; determine the abnormality of the cutting state in the current adjustment cycle according to the change trend and discreteness of the wear influence coefficient in the current adjustment cycle, combined with the synchronous change coefficient, and obtain the adjustment factor of the current adjustment cycle; Based on the adjustment factor of the current adjustment cycle, the steepness parameter of the acceleration equation in the S-type acceleration and deceleration algorithm of the next adjustment cycle is determined, and the feed speed of the tool in the CNC machine tool is planned.

[0006] Preferably, the method for obtaining the contact impact period and the cutting processing period is: Sudden changes are detected on the vibration data at all times during each cutting to obtain segmentation points; based on the segmentation points, the vibration data at all times during each cutting is divided into a contact impact period and a cutting processing period.

[0007] Preferably, determining the contact impact strength of each cutting comprises: Calculate the mean and standard deviation of the vibration data at all times during the contact impact period, and record them as a first mean and a first standard deviation; Calculate the mean and standard deviation of the vibration data at all times during the cutting process period, and record them as the second mean and the second standard deviation; The difference between the first mean and the second mean is recorded as a first difference; the difference between the first standard deviation and the second standard deviation is recorded as a second difference; The contact impact strength is the product of the first difference and the second difference.

[0008] Preferably, determining the vibration offset of each cutting comprises: Acquire the peak value of the vibration data at all times in the cutting process period during each cutting; The average value of the vibration data at all moments except the moment corresponding to the wave peak during the cutting process period is used as the basic vibration amount for each cutting; The difference between the peak value corresponding to each wave crest and the basic vibration amount is calculated, and the average of the difference values ​​of all wave crests in the cutting process period is used as the vibration offset of each cutting.

[0009] Preferably, the determining of the vibration fluctuation degree of each cutting comprises: The difference between the peak value of each wave crest and the peak value of its adjacent wave crest during the cutting process period is recorded as the peak value difference of each wave crest; Calculating the time interval between the time corresponding to each wave peak and the time corresponding to an adjacent wave peak in the cutting process period; The ratio of the peak value difference of each wave peak to the time interval is calculated, and the sum of the ratio results of all wave peaks in the cutting processing period during each cutting is taken as the vibration fluctuation degree of each cutting.

[0010] Preferably, determining the wear influence coefficient of each cutting includes: Calculating the product of the vibration offset and the vibration fluctuation degree, recorded as a first product; The sum of the contact impact strength and the first product is used as the wear influence coefficient of each cutting.

[0011] Preferably, the determining of the synchronous variation coefficient of the current adjustment cycle includes: Perform frequency domain analysis on the vibration data at all times during each cutting to obtain a spectrum diagram; use the frequency corresponding to the maximum amplitude in the spectrum diagram as the main vibration frequency of each cutting; Calculate the mean of the rotation speed data at all times during each cutting as the average rotation speed for each cutting; The synchronous variation coefficient is the difference between the main vibration frequency and the average rotation speed of all sub-cuts in the current adjustment cycle.

[0012] Preferably, determining the abnormality of the cutting state in the current adjustment cycle includes: Each cutting process in the current adjustment cycle is numbered from sequence number 1 in chronological order; the sequence number corresponding to each cutting in the current adjustment cycle and the corresponding wear influence coefficient are combined into a two-dimensional array; Obtaining the slope of the fitted straight line after linear fitting of all the two-dimensional arrays in the current adjustment period; Calculating the discrete degree of the wear influence coefficient of all cutting times in the current adjustment cycle; The product of the absolute value of the slope and the discrete degree is calculated and recorded as the second product. The ratio of the second product to the synchronous variation coefficient is used as the cutting state abnormality degree of the current adjustment cycle.

[0013] Preferably, the adjustment factor of the current regulation cycle is The calculation formula is: ,in, is the abnormality of the cutting state in the current adjustment cycle, is the logarithmic function with base 10.

[0014] Preferably, the steepness parameter of the acceleration equation in the S-shaped acceleration and deceleration algorithm of the next adjustment cycle includes: The Sigmoid function is used to transform the original jerk curve in the S-type acceleration and deceleration algorithm of the CNC machine tool to obtain the transformed jerk equation; The difference between the steepness parameter of the acceleration equation after the current adjustment cycle transformation and the adjustment factor is used as the steepness parameter of the acceleration equation after the next adjustment cycle transformation.

[0015] This application has at least the following beneficial effects: The present application determines the contact impact intensity of each cutting according to the difference in vibration data between the contact impact period and the cutting process period. The beneficial effect of the present application 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 taken into account to reflect the degree of contact impact generated when the tool contacts the part, and further reflects the wear of the tool in the CNC machine tool; the vibration offset of each cutting is determined according to the fluctuation intensity of the peak of the vibration data in the cutting process period; the difference in vibration data between adjacent peaks in the cutting process period and the interval time between corresponding moments between adjacent peaks are analyzed to determine the vibration fluctuation degree of each cutting; 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 of the present application is that the abnormal vibration of the tool in the cutting process period is taken into account to reflect the influence of tool wear or cutting force; the synchronous change coefficient of the current adjustment cycle is determined according to the difference between the frequency in the frequency domain corresponding to the vibration data of each cutting in the current adjustment cycle and the rotation speed. The beneficial effect of the present application is that the synchronous change coefficient of the current adjustment cycle is taken into account , to reflect the tool processing state of the CNC machine tool; according to the change trend and discrete situation of the wear influence coefficient in the current adjustment cycle, combined with the synchronous change coefficient, the cutting state abnormality of the current adjustment cycle is determined, which has the beneficial effect of considering the change trend of the machining process affected by the wear degree of the tool, combining the synchronous change of the vibration data and the speed change, further reflecting the cutting state of the CNC machine tool in the machining process, and accurately evaluating the tool cutting state during the current CNC machine tool machining; based on the cutting state abnormality, the adjustment factor of the current adjustment cycle is determined, and the cutting state abnormality of the CNC machine tool in the current adjustment cycle is evaluated. The jerk curve in the S-type acceleration and deceleration algorithm of the CNC machine tool is transformed, and the steepness parameter of the jerk equation of the next adjustment cycle is determined according to the difference between the steepness parameter in the jerk equation after the transformation in the current adjustment cycle and the adjustment factor, and the feed speed of the tool in the CNC machine tool is planned. The beneficial effect is that the jerk of the S-type acceleration and deceleration algorithm is adjusted based on the abnormality of the cutting state, the feed speed of the tool is smoothed according to different cutting states, smooth acceleration and deceleration is achieved, the stability and efficiency in the CNC machining process are improved, and the machining accuracy of engine shaft parts is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The following is a further detailed description of a method for machining engine shaft parts using a CNC machine tool of the present application in conjunction with the accompanying drawings.

[0017] Figure 1 A flowchart of a method for machining engine shaft parts using a CNC machine tool provided in an embodiment of the present application; Figure 2A flowchart of the steps of a method for obtaining the wear influence coefficient of each cutting provided in an embodiment of the present application; Figure 3 A flowchart of the steps of a method for obtaining the degree of abnormality of the cutting state in the current adjustment cycle provided in an embodiment of the present application. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of this application more clear, the following is a further detailed description of a method for machining engine shaft parts using a CNC machine tool proposed in this application in conjunction with the accompanying drawings and implementation examples. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0019] Unless defined otherwise, 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 application belongs.

[0020] See also Figure 1 , which shows a flowchart of a method for machining engine shaft parts using a CNC machine tool provided by an embodiment of the present application, the method comprising the following steps: Step 1, obtaining the vibration data and rotation speed data of the tool of the CNC machine tool at each moment during each cutting.

[0021] In actual processing and production, CNC machine tools cut parts according to the set processing programs. In order to improve the cutting efficiency and processing accuracy of machine tools, CNC machine tools are required to adjust the cutting speed in real time according to the actual processing status to adapt to various changes occurring during the cutting process.

[0022] During the cutting process, the vibration of the tool has a significant impact on the processing accuracy. During the production and processing of CNC machine tools, the tool will contact the surface of the part many times, that is, there are multiple tool feed controls. Each time the tool is fed, the part will be cut once, and the tool will vibrate. Therefore, a vibration sensor and a speed sensor are installed at the feed shaft where the tool is located to collect the vibration generated by the tool during each cutting process and the tool speed. Set the sensor acquisition frequency to f, normalize the collected data, and obtain the vibration data and speed data at each moment in each cutting process.

[0023] Preferably, in this embodiment, the acquisition frequency of the sensor is set to 500 Hz. As other implementations, the implementer can set it according to the actual situation. Secondly, the maximum and minimum value normalization method is used for normalization. As other implementations, the implementer can adopt other methods of the prior art, such as Z-score normalization method, etc. This embodiment does not impose any special restrictions on this.

[0024] At this point, the vibration data and rotation speed data of the CNC machine tool tool at each moment during each cutting are obtained.

[0025] Step 2, according to the difference in vibration data between the contact impact period and the cutting process period, determine the contact impact intensity of each cutting; according to the fluctuation intensity of the peak of the vibration data in the cutting process period, determine the vibration offset of each cutting; analyze the difference in vibration data between adjacent peaks in the cutting process period, as well as the interval time between adjacent peaks, 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.

[0026] Engine shaft parts, such as crankshafts and transmission shafts, are core components of engines. When machining these parts, accurate and stable tool feed speeds are required for processing and 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.

[0027] When CNC machine tools are producing and processing engine shaft parts, the processing tool used is a disc milling cutter. The disc milling cutter usually contains multiple blades. Under the influence of the disc milling cutter structure, the blades and the workpiece are always in intermittent contact, and different degrees of vibration are generated during the cutting process. Improper feed speed adjustment can easily cause abnormal vibration during the processing, and the wear of the tool and the cutting force will also affect the processing accuracy of the parts. The CNC machine tool needs to adjust the feed speed of the tool in time according to the actual processing status.

[0028] When processing different parts of the crankshaft in the engine, the external milling of the crankshaft journal and the connecting rod journal is an important link, which requires multiple feed cutting. The cutting force of different milling cutters in the processing parts may also be different, and as the tool continues to wear, it is easy to have different degrees of abnormal vibration. During each cutting, when the milling cutter just contacts the surface of the workpiece, a strong contact impact will be generated for a period of time. The vibration data during this period is generally large, and after the contact impact ends, the vibration data during the cutting process suddenly decreases. Therefore, the vibration data during each cutting shows a certain step feature. The greater the wear of the tool and the greater the cutting force, the more obvious the abnormal vibration may be. Compared with the vibration data under normal cutting conditions, abnormal vibration of the tool will make the fluctuation difference of the vibration data in different step periods greater, and after the contact impact ends, the peak deviation of the vibration data during cutting processing is large.

[0029] Based on the above analysis, the collected vibration data is divided to distinguish the two gradient periods: the contact impact period when the milling cutter just contacts the workpiece surface and the cutting processing period after the contact impact ends. Specifically: Perform mutation detection on the vibration data at all times during each cutting to obtain the segmentation points; Based on the segmentation point, the vibration data at all times during each cutting is divided into a contact impact period and a cutting processing period; Preferably, in this embodiment, the Bernaola Galvan segmentation algorithm is used to obtain the segmentation points, wherein the Bernaola Galvan segmentation algorithm is a well-known technology and will not be described in detail here. As other implementation methods, the implementer may adopt other methods of the prior art, such as Pettitt mutation point detection, etc. This embodiment does not impose any special restrictions on this.

[0030] Calculate the mean and standard deviation of the vibration data at all times during the contact impact period, and record them as a first mean and a first standard deviation; Calculate the mean and standard deviation of the vibration data at all times during the cutting process period, and record them as the second mean and the second standard deviation; The difference between the first mean and the second mean is recorded as a first difference; The difference between the first standard deviation and the second standard deviation is recorded as a second difference; Preferably, in this embodiment, the absolute value of the difference between the first mean and the second mean is recorded as the first difference; the absolute value of the difference between the first standard deviation and the second standard deviation is recorded as the second difference.

[0031] The product of the first difference and the second difference is used as the contact impact strength of each cutting; Preferably, in this embodiment, the calculation formula of the contact impact strength of each cutting is: ,in, For the Contact impact strength of the first cutting, For the The mean value of the vibration data at all times during the contact impact period during the first cutting, i.e. the first mean value, For the The mean value of the vibration data at all times during the cutting process is the second mean value. For the The standard deviation of the vibration data at all times during the contact impact period during the first cutting, i.e. the first standard deviation, For the The standard deviation of the vibration data at all times during the cutting process is the second standard deviation; secondly, For the first difference, The second difference.

[0032] It should be noted that if the central distribution trend or fluctuation difference of the vibration data between the contact impact period and the cutting processing period is greater, the abnormal vibration generated by the cutting is greater, and the contact impact intensity is greater, it means that the contact impact generated when the tool contacts the part is greater.

[0033] Further, the step flow chart of the method for obtaining the wear influence coefficient of each cutting provided in the embodiment of the present application is as follows: Figure 2 shown.

[0034] First, analyze the deviation of vibration data during the cutting process, specifically: Acquire the peak value of the vibration data at all times in the cutting process period during each cutting; Preferably, in this embodiment, an automatic multiscale-based peak detection (AMPD) algorithm is used to obtain the peak value, wherein the automatic multiscale peak detection algorithm is a well-known technology and will not be described in detail here. As other implementation methods, the implementer can adopt other methods of the prior art, such as the differential method, etc., and this embodiment does not impose any special restrictions on this.

[0035] The average value of the vibration data at all moments except the moment corresponding to the wave peak during the cutting process period is used as the basic vibration amount for each cutting; Calculating the difference between the peak value corresponding to each wave crest and the basic vibration amount, and taking the average of the difference values ​​of all wave crests in the cutting process period during each cutting as the vibration offset of each cutting; Preferably, in this embodiment, the absolute value of the difference between the peak value corresponding to each peak and the basic vibration amount is calculated; and the average of the absolute values ​​of all peaks in the cutting process period during each cutting is taken as the vibration offset of each cutting.

[0036] It should be noted that the basic vibration amount is the vibration generated by the inevitable situation in the cutting process. The more the peak value of the wave peak deviates from the basic vibration amount, the more likely it is that abnormal vibration will exist. Therefore, the larger the obtained vibration offset amount, the greater the degree of deviation of the abnormal vibration in the vibration data compared to the basic vibration amount, and the greater the possibility of abnormal vibration.

[0037] Furthermore, by analyzing the differences between adjacent peaks and the high frequency of peaks, the abnormal vibration of the tool in the CNC machine tool can be reflected, specifically: The difference between the peak value of each wave crest in the cutting process period and the peak value of the previous wave crest is recorded as the peak value difference of each wave crest; Preferably, in this embodiment, the absolute value of the difference between the peak value of each peak in the cutting process period and the peak value of the previous peak is recorded as the peak value difference of each peak.

[0038] Calculating the time interval between the time corresponding to each wave peak in the cutting process period and the time corresponding to the previous wave peak; Calculating the ratio of the peak value difference of each wave crest to the time interval, and taking the sum of the ratios of all wave crests in the cutting processing period during each cutting as the vibration fluctuation degree of each cutting; It should be noted that the smaller the time interval is, the higher the frequency of the peaks appearing, and the larger the resulting vibration fluctuation is, which means that the vibration changes of the tool in the CNC machine tool are more irregular and the frequency of occurrence is higher.

[0039] Further, based on the contact impact strength, the vibration offset and the vibration fluctuation, the wear influence coefficient is determined, specifically: Calculating the product of the vibration offset and the vibration fluctuation degree as a first product, and taking the sum of the contact impact strength and the first product as the wear influence coefficient of each cutting; It should be noted that the greater the vibration offset and the vibration fluctuation, 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 intensity, the greater the contact impact generated when the tool contacts the part, which will cause a higher degree of tool wear. The larger the resulting wear influence coefficient, the more likely it is that each cutting during the machining process will be affected by tool wear or cutting force.

[0040] At this point, the wear influence coefficient of each cutting is obtained.

[0041] Step 3, preset each adjustment cycle; determine the synchronous change coefficient of the current adjustment cycle based on the difference between the frequency and the rotational speed in the frequency domain of the vibration data of each cutting in the current adjustment cycle; determine the abnormality of the cutting state in the current adjustment cycle based on the change trend and discreteness of the wear influence coefficient in the current adjustment cycle, combined with the synchronous change coefficient.

[0042] Furthermore, in addition to the crankshaft journal and connecting rod journal, the engine crankshaft also includes multiple parts such as the crank and crank. Due to different processing technology requirements, different milling cutter speeds need to be set. Under good processing conditions, the change in milling cutter speed has little effect on tool vibration; when the processing condition is poor, since the milling cutter is rotating periodically, the frequency of abnormal vibration will change synchronously with the change in rotation speed.

[0043] Based on the above analysis, the synchronization coefficient is determined by analyzing the synchronization of the vibration data and the speed data changes, which is: Perform frequency domain analysis on the vibration data at all times during each cutting to obtain a spectrum diagram; Preferably, in this embodiment, discrete Fourier transform is used to obtain the spectrum diagram, wherein discrete Fourier transform is a well-known technology and will not be described in detail here. As other implementation methods, the implementer can adopt other methods of the prior art, such as fast Fourier transform, etc. This embodiment does not impose any special restrictions on this.

[0044] The frequency corresponding to the maximum amplitude in the spectrum diagram is taken as the main vibration frequency of each cutting; Calculate the mean of the rotation speed data at all times during each cutting as the average rotation speed for each cutting; Each cutting and the previous cutting processes are recorded as an adjustment cycle; Preferably, in this embodiment, each cutting and the previous 7 cutting processes are recorded as an adjustment cycle. As other implementation modes, the implementer can set them according to the actual situation.

[0045] The difference between the main vibration frequency and the average rotation speed of all sub-cuts in the current adjustment cycle is used as the synchronization variation coefficient of the current adjustment cycle; Preferably, in this embodiment, the DTW distance between the main vibration frequency and the average rotation speed of all sub-cuts in the current adjustment cycle is used as the synchronization variation coefficient of the current adjustment cycle.

[0046] It should be noted that the smaller the synchronous variation coefficient is, the more synchronous the variation of the tool vibration and rotation speed is, which means that when the rotation speed of the milling cutter changes, it will affect the variation of the tool vibration, which further reflects that the tool machining state of the CNC machine tool is poor.

[0047] Furthermore, during the machine tool processing, due to multiple cutting operations, the tool temperature gradually increases, which may have an adverse effect on the quality of the processed parts. If the processing state is poor, due to improper control of the tool feed speed during machine tool processing and increased tool wear, the vibration data in the cutting process is more and more likely to be abnormal, which is specifically manifested in the fluctuation of the wear influence coefficient and the overall change trend. At the same time, the main vibration frequency and the rotation speed change synchronously.

[0048] Based on the above analysis, the cutting state abnormality is determined by analyzing the change trend of the wear influence coefficient and the synchronous change coefficient in the current adjustment cycle to reflect the cutting state of the CNC machine tool during machining, specifically: Each cutting process in the current adjustment cycle is numbered from sequence number 1 in chronological order; the sequence number corresponding to each cutting in the current adjustment cycle and the corresponding wear influence coefficient are combined into a two-dimensional array; Performing linear fitting on all the two-dimensional arrays in the current adjustment period to obtain the slope of the fitting line; Preferably, in this embodiment, the least squares method is used for linear fitting, wherein the least squares method is a well-known technology and will not be described in detail here. As other implementation methods, the implementer may adopt other methods of the prior art, such as the maximum likelihood estimation method, etc. This embodiment does not impose any special restrictions on this.

[0049] Calculating the discrete degree of the wear influence coefficient of all cutting times in the current adjustment cycle; Preferably, in this embodiment, the information entropy of the wear influence coefficient of all cutting times in the current adjustment cycle is calculated, wherein the calculation of information entropy is a well-known technology and will not be repeated here. As other implementation methods, the implementer may adopt other methods of the prior art, such as coefficient of variation, variance, standard deviation, etc. This embodiment does not impose any special restrictions on this.

[0050] Calculating the product of the absolute value of the slope and the discrete degree, recording it as a second product, and taking the ratio of the second product to the synchronous variation coefficient as the cutting state abnormality of the current adjustment cycle; Preferably, in this embodiment, the calculation method of the abnormality of the cutting state in the current adjustment cycle is: ,in, is the abnormality of the cutting state in the current adjustment cycle, is the absolute value of the slope of the current adjustment cycle, is the information entropy of the wear influence coefficient of all cutting times in the current adjustment cycle, that is, the degree of discreteness, is the synchronous variation coefficient of the current adjustment cycle, To preset a value greater than 0 to avoid the denominator being 0, in this embodiment, The value is 0.01; the step flow chart of the method for obtaining the abnormality of the cutting state in the current adjustment cycle provided in this embodiment is as follows Figure 3 shown.

[0051] It should be noted that, the larger the absolute value of the slope is, the more the wear influence coefficient shows a certain change trend, and the machining process is gradually affected more by the wear degree of the tool. Secondly, the larger the discrete degree is, the different degrees of wear influence are caused during multiple cuttings, which further indicates that the state of the tool fluctuates; secondly, the smaller the synchronous change coefficient is, the more synchronous changes there are between the vibration and rotation speed of the tool, and the machining state of the CNC machine tool is poor. The greater the abnormality of the obtained cutting state is, the worse the cutting state of the current CNC machine tool is during machining.

[0052] At this point, the abnormality degree of the cutting state in the current adjustment cycle is obtained.

[0053] Step 4, based on the abnormality of the cutting state, 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 acceleration equation in the S-type acceleration and deceleration algorithm of the next adjustment cycle, and plan the feed speed of the tool in the CNC machine tool.

[0054] Based on the above analysis, the cutting state at different times is judged through the vibration data during the machining of shaft parts. The greater the impact of tool wear or cutting force during the machining process, the greater the abnormality of the cutting state, and the more likely it is to affect the accuracy of the machined parts. Therefore, the impact of tool wear or cutting force can be reduced by increasing the smoothness of the tool feed speed.

[0055] The Sigmoid function is used to transform the original jerk curve in the S-type acceleration and deceleration algorithm of the CNC machine tool to obtain the transformed jerk equation; It should be noted that the method of transforming the original jerk curve in the S-type acceleration and deceleration algorithm using the Sigmoid function is a well-known technology and will not be described in detail here.

[0056] Furthermore, the size of the steepness parameter in the transformed jerk equation will affect the smoothness of the tool feed speed. Therefore, when the cutting state abnormality is greater, in order to achieve smoother tool feed speed control, it is necessary to reduce the steepness parameter in the jerk equation. Therefore, based on the cutting state abnormality, an adjustment factor is determined to smooth the feed speed during the CNC machine tool machining process, specifically: The calculation formula of the adjustment factor of the current regulation cycle is: ,in, is the adjustment factor of the current regulation cycle, is the abnormality of the cutting state in the current adjustment cycle, is the logarithmic function with base 10.

[0057] Based on the adjustment factor of the current adjustment cycle, the steepness parameter of the acceleration equation in the S-type acceleration and deceleration algorithm of the next adjustment cycle is determined to smooth the feed speed during the CNC machine tool processing, specifically: The difference between the steepness parameter of the acceleration equation after the current adjustment cycle transformation and the adjustment factor is used as the steepness parameter of the acceleration equation after the next adjustment cycle transformation.

[0058] According to the jerk equation, CNC machine tools plan the feed speed of the tool in the CNC machine tools to achieve smooth acceleration and deceleration, thereby controlling the feed speed of the tool, improving the stability and efficiency of the CNC machining process, and improving the machining accuracy of engine shaft parts.

[0059] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0060] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the present application. It should be pointed out that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application without departing from the content of the technical solution of the present application, shall fall within the protection scope of the technical solution of the present application.

Claims

1. A method for machining engine shaft parts using a CNC machine tool, characterized in that: The method comprises the following steps: Obtaining vibration data and rotation speed data of the tool of the CNC machine tool at each moment of each cutting; dividing all moments of 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 process period; determine the vibration offset of each cutting according to the fluctuation intensity of the peak of the vibration data in the cutting process period; analyze the difference in vibration data between adjacent peaks in the cutting process period and the interval time between adjacent peaks to determine the vibration fluctuation degree of each cutting; determine the wear influence coefficient of each cutting based on the vibration offset, the vibration fluctuation degree and the contact impact intensity; Preset each adjustment cycle; determine the synchronous change coefficient of the current adjustment cycle according to the difference between the frequency and the rotation speed of the vibration data of each cutting in the current adjustment cycle in the frequency domain; determine the abnormality of the cutting state in the current adjustment cycle according to the change trend and discreteness of the wear influence coefficient in the current adjustment cycle, combined with the synchronous change coefficient, and obtain the adjustment factor of the current adjustment cycle; Based on the adjustment factor of the current adjustment cycle, the steepness parameter of the acceleration equation in the S-type acceleration and deceleration algorithm of the next adjustment cycle is determined, and the feed speed of the tool in the CNC machine tool is planned.

2. The method for machining engine shaft parts using a numerically controlled machine tool as claimed in claim 1, characterized in that: The method for obtaining the contact impact period and the cutting processing period is: Sudden changes are detected on the vibration data at all times during each cutting to obtain segmentation points; based on the segmentation points, the vibration data at all times during each cutting is divided into a contact impact period and a cutting processing period.

3. The method for machining engine shaft parts using a numerically controlled machine tool as claimed in claim 1, characterized in that: Determining the contact impact strength of each cutting comprises: Calculate the mean and standard deviation of the vibration data at all times during the contact impact period, and record them as a first mean and a first standard deviation; Calculate the mean and standard deviation of the vibration data at all times during the cutting process period, and record them as the second mean and the second standard deviation; The difference between the first mean and the second mean is recorded as a first difference; the difference between the first standard deviation and the second standard deviation is recorded as a second difference; The contact impact strength is the product of the first difference and the second difference.

4. The method for machining engine shaft parts using a numerically controlled machine tool as claimed in claim 1, characterized in that: Determining the vibration offset of each cutting comprises: Acquire the peak value of the vibration data at all times in the cutting process period during each cutting; The average value of the vibration data at all moments except the moment corresponding to the wave peak during the cutting process period is used as the basic vibration amount for each cutting; The difference between the peak value corresponding to each wave crest and the basic vibration amount is calculated, and the average of the difference values ​​of all wave crests in the cutting process period is used as the vibration offset of each cutting.

5. The method for machining engine shaft parts using a numerically controlled machine tool as claimed in claim 4, characterized in that: Determining the vibration fluctuation degree of each cutting includes: The difference between the peak value of each wave crest and the peak value of its adjacent wave crest during the cutting process period is recorded as the peak value difference of each wave crest; Calculating the time interval between the time corresponding to each wave peak and the time corresponding to an adjacent wave peak in the cutting process period; The ratio of the peak value difference of each wave peak to the time interval is calculated, and the sum of the ratio results of all wave peaks in the cutting processing period during each cutting is taken as the vibration fluctuation degree of each cutting.

6. The method for machining engine shaft parts using a numerically controlled machine tool as claimed in claim 1, characterized in that: Determining the wear influence coefficient of each cutting includes: Calculating the product of the vibration offset and the vibration fluctuation degree, recorded as a first product; The sum of the contact impact strength and the first product is used as the wear influence coefficient of each cutting.

7. The method for machining engine shaft parts using a numerically controlled machine tool as claimed in claim 1, characterized in that: The step of determining the synchronous variation coefficient of the current adjustment cycle includes: Perform frequency domain analysis on the vibration data at all times during each cutting to obtain a spectrum diagram; use the frequency corresponding to the maximum amplitude in the spectrum diagram as the main vibration frequency of each cutting; Calculate the mean of the rotation speed data at all times during each cutting as the average rotation speed for each cutting; The synchronous variation coefficient is the difference between the main vibration frequency and the average rotation speed of all sub-cuts in the current adjustment cycle.

8. The method for machining engine shaft parts using a numerically controlled machine tool as claimed in claim 1, characterized in that: Determining the abnormality of the cutting state in the current adjustment cycle includes: Each cutting process in the current adjustment cycle is numbered from sequence number 1 in chronological order; the sequence number corresponding to each cutting in the current adjustment cycle and the corresponding wear influence coefficient are combined into a two-dimensional array; Obtaining the slope of the fitted straight line after linear fitting of all the two-dimensional arrays in the current adjustment period; Calculating the discrete degree of the wear influence coefficient of all cutting times in the current adjustment cycle; The product of the absolute value of the slope and the discrete degree is calculated and recorded as the second product. The ratio of the second product to the synchronous variation coefficient is used as the cutting state abnormality degree of the current adjustment cycle.

9. The method for machining engine shaft parts using a numerically controlled machine tool as claimed in claim 1, characterized in that: Adjustment factor for the current adjustment period The calculation formula is: ,in, is the abnormality of the cutting state in the current adjustment cycle, is the logarithmic function with base 10.

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

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