A method for modifying the tooth thickness of a double-lead worm gear

Abstract

The present application relates to gear machining technical field, especially a kind of variable tooth thickness modification machining method for double lead worm gear and worm, including the wave form distortion rate of idle cutting force of hobbing cutter and torsional stiffness coefficient;Real-time monitoring cutting force wave form distortion rate and tool torsional deformation, calculate disturbance intensity index to divide disturbance level and set detection opportunity;Through the tooth thickness curve of actual measurement, tooth thickness change rate coefficient is obtained to judge machining quality;The tooth thickness deviation curve of unqualified tooth groove is analyzed to determine the dominant interference type, and the spindle speed or tool pose is regulated based on disturbance level;The control effect is verified by attenuation coefficient;When not up to standard, attenuation difference is used to optimize control coefficient;Finally, the overall quality of worm is evaluated by the consistency coefficient of tooth thickness change rate of each tooth groove of full tooth surface.The present application solves the problem that the full tooth surface consistency of formed worm is low due to the resonance and deformation disturbance of asymmetric characteristics of hobbing cutter in variable tooth thickness worm machining.

Description

Technical Field

[0001] This invention relates to the field of gear machining technology, and in particular to a variable tooth thickness profile machining method for double-lead worm gears. Background Technology

[0002] Dual-lead worm gear drives are widely used in high-precision transmission fields such as precision CNC machine tool rotary tables, robot RV reducers, and aerospace actuators because they can precisely adjust the meshing backlash through axial movement without changing the center distance. The core of this type of transmission pair lies in the asymmetrical geometric feature of the worm, which has different leads on the left and right tooth surfaces, thus achieving continuous axial variation in tooth thickness. Traditionally, worm gears paired with this special worm are generated using a dedicated dual-lead hob with parameters identical to the worm. However, this method suffers from limitations such as high tool manufacturing costs, long design cycles, and the rigid limitation that each hob can only machine one type of worm gear.

[0003] To overcome the aforementioned limitations, using standard involute hobs instead of dedicated hobs for machining variable tooth thickness worm gears has become an important technological direction in this field. However, during the machining process with standard hobs, the asymmetry in the spatial distribution of the cutting edges due to the different leads on the left and right tooth surfaces of the hob causes distortion in the cutting force waveform, easily triggering multi-mode resonance in the machine tool. Simultaneously, the inconsistent cutting force vectors caused by different pressure angles at each section lead to coupled torsional and bending deformations in the hob, resulting in a complex and variable cutting state during machining. Ultimately, this causes the tooth thickness along the tooth width to deviate from the design value, and the consistency across the entire tooth surface is difficult to guarantee. Existing machining methods lack real-time quantitative sensing of this coupled disturbance, making it impossible to dynamically adjust the detection strategy based on the disturbance intensity to balance efficiency and quality. Furthermore, it is impossible to trace the root cause of the tooth thickness deviation as resonance or deformation, resulting in a lack of targeted control measures. Optimization of machining parameters relies heavily on operator experience, severely restricting the manufacturing quality and efficiency of high-precision variable tooth thickness worm gears.

[0004] Therefore, how to achieve real-time quantitative perception and root cause tracing of coupled disturbances during standard hobbing process, and to carry out graded control and closed-loop verification according to the disturbance level, so as to improve the machining accuracy and full tooth surface consistency of variable tooth thickness worm gears, has become a technical problem that urgently needs to be solved in this field.

[0005] Chinese Patent Application Publication No. CN115488439A discloses a method for machining tangential variable tooth thickness external gears. The method involves first rough machining the teeth of the tangential variable tooth thickness external gear using a gear shaping method, and then machining the finished tangential variable tooth thickness external gear using profile grinding. A gear shaping cutter with a tooth thickness smaller than the width of the small end tooth groove of the tangential variable tooth thickness external gear is used for rough machining. First, the gear shaping cutter is used to machine the middle of the tooth groove of the tangential variable tooth thickness external gear in the manner of shaping a spur gear; then, the gear shaping cutter is used to machine the left and right helical tooth surfaces in the manner of shaping helical teeth, leaving a grinding allowance for the tooth thickness. The profile grinding process involves first grinding the left and right helical tooth surfaces, and then grinding the root circle. This invention uses a gear shaping method to rough machine the teeth of the tangential variable tooth thickness external gear, and then uses profile grinding to finish the tooth surfaces and root circles. The gear shaping rough machining can reduce machining allowance and is highly efficient, while the profile grinding can improve gear precision, meeting the needs of mass production.

[0006] However, the aforementioned method for machining external gears with tangential variable tooth thickness still has the following problems:

[0007] This solution employs a static process route of roughing gear shaping followed by finishing gear grinding. It achieves variable tooth thickness machining by pre-setting the helix angle and leaving allowance. Its core lies in the pre-calculation of tool geometry parameters. This solution is an open-loop machining method, which cannot detect the resonance and deformation coupling disturbances dynamically induced by the asymmetric characteristics of the tool during machining. Furthermore, it cannot adjust process parameters according to the real-time machining status. When dealing with parts such as double-lead worm gears, which have extremely high requirements for the consistency of tooth thickness variation, it is difficult to guarantee the accuracy of the entire tooth surface. Dynamic deviations generated during machining cannot be detected and corrected in a timely manner, which can easily lead to batch scrap, and the root cause of the problem is difficult to trace. Summary of the Invention

[0008] Therefore, the present invention provides a variable tooth thickness profile machining method for dual-lead worm gears, which overcomes the problem of low uniformity of the entire tooth surface of the variable tooth thickness worm gear caused by the resonance and deformation disturbance of the asymmetric characteristics of the hob during the machining of variable tooth thickness worm gears in the prior art.

[0009] To achieve the above objectives, the present invention provides a method for variable tooth thickness profile machining of a double-lead worm gear, comprising:

[0010] Obtain the waveform distortion rate of the idling cutting force and the torsional stiffness coefficient of the hob when it is idling at a predetermined speed;

[0011] Based on the three-phase cutting force signal of the hob, the real-time cutting force waveform distortion rate and real-time cutting force waveform distortion frequency of the hob are obtained, and the real-time tool torsional deformation of the hob is determined.

[0012] Based on the real-time cutting force waveform distortion rate and the idle cutting force waveform distortion rate, the disturbance intensity index of the hob on the machining process is obtained to determine the disturbance level in the current machining process and set the detection timing for the tooth groove.

[0013] Obtain the actual tooth thickness values ​​at several positions of the current tooth groove, generate the first actual tooth thickness variation curve, and determine the first tooth thickness variation rate coefficient to determine whether the tooth groove quality based on the current hob is qualified.

[0014] Based on the first actual tooth thickness variation curve, the deviation main frequency is determined to determine the current dominant interference type, and based on the disturbance level, the current machining parameters are adjusted by the spindle speed adjustment amount and the spindle position compensation amount.

[0015] Obtain the second tooth thickness change rate coefficient after adjustment, and obtain the tooth thickness change attenuation coefficient to determine whether the current adjustment effect is qualified;

[0016] Based on the absolute attenuation difference between the tooth thickness variation attenuation coefficient and the preset tooth thickness variation attenuation coefficient, the amount of spindle speed adjustment and the amount of spindle position compensation are determined by the optimization coefficient.

[0017] Obtain the uniformity coefficient of tooth thickness variation rate, which characterizes the uniformity of tooth thickness variation across all tooth grooves of the formed worm gear, to determine the quality of the current formed worm gear.

[0018] Furthermore, the process of determining the disturbance level in the current machining process and setting the timing for detecting the tooth groove includes,

[0019] The distortion increment is calculated based on the real-time cutting force waveform distortion rate and the hob idle cutting force waveform distortion rate.

[0020] The disturbance intensity index is calculated based on the distortion increment and the real-time tool torsional deformation.

[0021] Based on the fact that the disturbance intensity index is less than or equal to the first preset disturbance intensity index, the disturbance level in the current processing process is determined to be a slight disturbance, and a detection is performed after processing three tooth grooves.

[0022] Furthermore, the process of determining the disturbance level in the current machining process and setting the timing for detecting the tooth groove also includes,

[0023] Based on the fact that the disturbance intensity index is greater than the first preset disturbance intensity index and less than or equal to the second preset disturbance intensity index, the disturbance level in the current processing process is determined to be medium disturbance, and a detection is set to be performed after each tooth groove is processed.

[0024] If the disturbance intensity index is greater than the second preset disturbance intensity index, the disturbance level in the current processing process is determined to be a severe disturbance, and processing is stopped.

[0025] Wherein, the first preset disturbance intensity index is less than the second preset disturbance intensity index.

[0026] Furthermore, the process of determining whether the machining quality of the current tooth groove is qualified includes,

[0027] Obtain the first actual tooth thickness value at at least 10 different locations of the current tooth groove;

[0028] The first tooth thickness deviation value is calculated based on the first actual tooth thickness value and the theoretical tooth thickness value.

[0029] Using the tooth width position as the abscissa and the first tooth thickness deviation value as the ordinate, a first actual tooth thickness variation curve is generated, and the slope value is calculated as the first tooth thickness variation rate coefficient.

[0030] Based on the fact that the first tooth thickness change rate coefficient is greater than the preset first tooth thickness change rate coefficient, it is determined that the tooth groove quality processed by the current hob is unqualified.

[0031] Furthermore, determining the current dominant disturbance type and, based on the disturbance level, the process of adjusting the current machining parameters by the spindle speed adjustment includes:

[0032] Analyze the first tooth thickness variation curve and extract the frequency component with the largest amplitude in the spectrum distribution as the deviation main frequency;

[0033] The frequency difference is calculated based on the distortion frequency of the real-time cutting force waveform and the dominant frequency of the deviation.

[0034] Based on the fact that the frequency difference is less than a preset frequency difference, the current dominant interference type is determined to be resonance-dominant.

[0035] Based on the fact that the current disturbance level is a slight disturbance, it is determined that the spindle speed in the current machining state will be reduced by the first spindle speed adjustment amount;

[0036] The first spindle speed adjustment amount is obtained by multiplying the current spindle speed, the first speed adjustment coefficient, and the ratio of the deviation of the main frequency to the machine tool's natural frequency.

[0037] Based on the fact that the disturbance level is severe, it is determined that the spindle speed in the current machining state will be reduced by the second spindle speed adjustment amount;

[0038] The second spindle speed adjustment amount is obtained by multiplying the current spindle speed, the second speed adjustment coefficient, the ratio of the deviation of the main frequency to the machine tool's natural frequency, and the ratio of the current disturbance intensity index to the preset disturbance intensity index.

[0039] Furthermore, determining the current dominant disturbance type and, based on the disturbance level, the process of adjusting the current machining parameters by the spindle position compensation includes:

[0040] Based on the frequency difference being greater than or equal to a preset frequency difference, the current dominant interference type is determined to be a deformable dominant type.

[0041] Based on the fact that the current disturbance level is a slight disturbance, it is determined that the position of the current hob X-axis will be adjusted by the first X-axis position compensation amount;

[0042] The first X-axis position compensation amount is obtained by multiplying the hob bar radius, the displacement compensation coefficient, and the real-time tool torsional deformation amount.

[0043] Based on the fact that the current disturbance level is severe, it is determined that the position of the current hob X-axis is adjusted by the second X-axis position compensation amount, and the cutting edge attitude angle is adjusted by the C-axis compensation amount.

[0044] The adjustment of the second X-axis position compensation amount is obtained by multiplying the hob bar radius, displacement compensation coefficient, real-time tool torsional deformation amount, and the ratio of the current disturbance intensity index to the preset disturbance intensity index.

[0045] The C-axis compensation amount is obtained by multiplying the angle compensation coefficient, the real-time tool torsional deformation amount, and the ratio of the current disturbance intensity index to the preset disturbance intensity index.

[0046] Furthermore, the process of determining whether the current regulatory effect is satisfactory includes,

[0047] Obtain the second actual tooth thickness value at at least 10 different locations of the current tooth groove;

[0048] The second tooth thickness deviation value is calculated based on the second actual tooth thickness value and the theoretical tooth thickness value.

[0049] Using the tooth width position as the abscissa and the second tooth thickness deviation value as the ordinate, a second actual tooth thickness variation curve is generated, and the slope value is calculated as the second tooth thickness variation rate coefficient.

[0050] The tooth thickness variation attenuation coefficient is calculated based on the first tooth thickness variation rate coefficient and the second tooth thickness variation rate coefficient.

[0051] Based on the fact that the tooth thickness change attenuation coefficient is less than the preset tooth thickness change attenuation coefficient, it is determined that the current control effect is unqualified.

[0052] Furthermore, the process of determining the spindle speed adjustment and the spindle position compensation amount by optimizing the coefficients includes,

[0053] Based on the fact that the absolute attenuation difference is less than or equal to a preset absolute attenuation difference, the optimization range of the processing parameters is determined as the first optimization range;

[0054] The first optimization amplitude is based on the fact that the dominant interference type is resonance dominant, and the first speed adjustment coefficient and the second speed adjustment coefficient are corrected by the first optimization coefficient to obtain the first speed adjustment coefficient correction value and the second speed adjustment coefficient correction value;

[0055] The first optimization magnitude is based on the fact that the dominant disturbance type is deformation-dominant. The displacement compensation coefficient and the angle compensation coefficient are corrected by the first optimization coefficient to obtain the displacement compensation coefficient correction value and the angle compensation coefficient correction value.

[0056] Furthermore, the process of determining the spindle speed adjustment and the spindle position compensation amount by optimizing the coefficients also includes,

[0057] Based on the fact that the absolute attenuation difference is greater than the preset absolute attenuation difference, the optimization range corresponding to the processing parameters is determined as the second optimization range;

[0058] The second optimization amplitude is based on the fact that the dominant interference type is resonance dominant, and the first speed adjustment coefficient and the second speed adjustment coefficient are corrected by the second optimization coefficient to obtain the first speed adjustment coefficient correction value and the second speed adjustment coefficient correction value;

[0059] The second optimization magnitude is based on the fact that the dominant disturbance type is deformation-dominant. The displacement compensation coefficient and the angle compensation coefficient are corrected by the second optimization coefficient to obtain the displacement compensation coefficient correction value and the angle compensation coefficient correction value.

[0060] Furthermore, the process of determining the quality of the currently formed worm gear includes,

[0061] Obtain the tooth thickness variation curve of each tooth groove of the formed worm gear along the tooth width direction, and record the total number of tooth grooves;

[0062] The uniformity coefficient of tooth thickness variation rate is calculated based on the average value and standard deviation of the tooth thickness variation rate coefficient of all tooth grooves;

[0063] Based on the fact that the uniformity coefficient of tooth thickness change rate is less than the preset uniformity coefficient of tooth thickness change rate, it is determined that the quality of the current formed worm gear is unqualified and it is rejected.

[0064] Based on the fact that the uniformity coefficient of tooth thickness change rate is greater than or equal to the preset uniformity coefficient of tooth thickness change rate, the quality of the current formed worm gear is determined to be qualified, and the variable tooth thickness processing is completed.

[0065] Compared with existing technologies, the advantages of this invention are as follows: By collecting the distortion rate of the hob's idling cutting force waveform and the torsional stiffness coefficient before machining, this invention determines the characteristic benchmark of the tool-spindle system, solving the technical problem that traditional methods cannot distinguish between the inherent characteristics of the tool and the disturbances introduced by machining; by fusing the real-time cutting force waveform distortion increment with the real-time tool torsional deformation to calculate the disturbance intensity index, this invention achieves a quantitative characterization of the mutually reinforcing effect of resonance risk and tool deformation risk caused by the asymmetry of the cutting edge distribution, and dynamically sets the detection timing based on this index, so that the detection timing is precisely matched with the machining risk, solving the contradiction that efficiency and quality cannot be balanced under a fixed detection frequency; by analyzing the tooth thickness deviation curve of the defective tooth groove and extracting the deviation main frequency, and comparing it with the cutting force waveform distortion frequency, this invention achieves precise tracing of the root cause of the tooth thickness machining deviation, enabling the control measures to be precisely controlled for different root causes; By implementing control based on the dominant interference type and disturbance level, under the resonance-dominant type, the speed adjustment is calculated by the deviation of the deviation frequency from the machine tool's natural frequency. Under the deformation-dominant type, the X-axis position compensation and C-axis attitude compensation are calculated by real-time torsional deformation and disturbance intensity indicators, achieving dynamic matching between the control amplitude and the severity of the disturbance, avoiding over-control or under-control. The tooth thickness change attenuation coefficient is calculated by the attenuation degree of the tooth thickness change rate coefficient before and after control, quantitatively verifying the control effect. When the standard is not met, the control coefficient is automatically optimized based on the absolute attenuation difference, making the machining parameters more and more accurate with use. The tooth thickness change rate uniformity coefficient is calculated by calculating the ratio of the standard deviation to the average value of the tooth thickness change rate coefficient of the entire tooth surface, and the quality of the variable tooth thickness worm gear machined by the spout is determined accordingly. This solves the deep problem that traditional single tooth groove inspection cannot assess the consistency of the entire tooth surface, improving the machining quality of variable tooth thickness worm gears.

[0066] Furthermore, this invention determines the characteristic benchmark of the tool-spindle system by acquiring the waveform distortion rate and torsional stiffness coefficient of the hob during idle operation before machining, thus solving the technical problem that traditional methods cannot distinguish between the inherent characteristics of the tool and the disturbances introduced by machining. Through coordinate transformation, the tangential cutting force component is calculated in real time from the three-dimensional cutting force signal, and combined with the torsional stiffness coefficient, the real-time waveform distortion rate, distortion frequency, and tool torsional deformation are simultaneously obtained, achieving real-time quantitative perception of the resonance risk and tool deformation risk caused by the asymmetry of the cutting edge distribution. The invention also calculates the disturbance by fusing the incremental distortion of the cutting force waveform with the tool torsional deformation. The dynamic strength index is used to determine the current disturbance level and dynamically set the detection timing according to the disturbance level. Specifically, for mild disturbances, an inspection is performed every three slots to improve processing efficiency, while for severe disturbances, an inspection is performed on every slot to ensure processing quality. This ensures that the detection strategy is precisely matched with processing risks, resolving the contradiction between efficiency and quality under a fixed detection frequency. By linearly fitting the tooth thickness deviation curve of the defective tooth slots to extract the tooth thickness change rate coefficient, the abstract tooth surface quality is transformed into a quantifiable index. This allows for accurate determination of whether the current processing parameters are acceptable for the tooth slot processing quality, effectively reducing the accumulation of errors during continuous processing.

[0067] Furthermore, this invention analyzes the tooth thickness deviation curve of defective tooth grooves, extracts the dominant frequency of the deviation, and compares the dominant frequency with the distortion frequency of the real-time cutting force waveform. This achieves precise tracing of the root cause of the tooth thickness deviation. Specifically, when the frequency difference is less than a preset value, it is determined to be a resonance-dominant type, indicating that the deviation is mainly caused by machine tool resonance excited by the distortion of the cutting force waveform; when the frequency difference is greater than or equal to the preset value, it is determined to be a deformation-dominant type, indicating that the deviation is mainly caused by the cutting trajectory deviation caused by the torsional deformation of the tool. This solves the technical problem that traditional methods cannot distinguish the root cause of the deviation and can only blindly try and fail. The invention also performs graded control based on the dominant interference type and disturbance level. Under the resonance-dominant mode, the speed adjustment is calculated by the deviation of the main frequency from the machine tool's natural frequency. Under the deformation-dominant mode, the X-axis position compensation and C-axis attitude compensation are calculated by real-time torsional deformation and disturbance intensity indicators, achieving precise matching between the control object and the root cause of the influence, and between the control amplitude and the risk level. The tooth thickness change attenuation coefficient is calculated by the attenuation degree of the tooth thickness change rate coefficient before and after control, which can transform the abstract control effect into a quantifiable attenuation ratio, achieving objective verification of the effectiveness of the control measures. This solves the problem of traditional methods that only control without detecting the control effect, effectively reducing the accumulation of machining quality errors and improving the machining quality of variable tooth thickness worm gears.

[0068] Furthermore, this invention quantifies the degree of control deviation by calculating the absolute attenuation difference between the tooth thickness variation attenuation coefficient and the preset attenuation coefficient when the control effect is not up to standard. This solves the problem of mismatch between optimization intensity and deviation degree caused by the traditional method of uniformly treating all non-compliance. The optimization amplitude is determined according to the dominant interference type. Specifically, the speed adjustment coefficient is corrected under the resonance-dominant type, and the displacement compensation coefficient and angle compensation coefficient are corrected under the deformation-dominant type, achieving a precise correspondence between the optimization object and the root cause of the deviation. The basic optimization step size factor is calibrated through a limited number of process experiments, and the optimization coefficient is dynamically determined based on the actual number of optimizations, avoiding slow optimization or overshoot oscillation of the machine tool caused by fixed step size optimization. After completing the machining of all tooth slots, the tooth thickness variation rate uniformity coefficient is calculated by calculating the ratio of the standard deviation to the average value of the tooth thickness variation rate coefficient of each tooth slot. This solves the problem that the traditional method only focuses on the qualification of a single tooth slot and cannot evaluate the consistency of the entire tooth surface. This makes the machining parameters more and more accurate with use, improves the machining quality of high-precision dual-lead worm gears, and reduces the scrap rate. Attached Figure Description

[0069] Figure 1 This is a schematic diagram of the steps in the variable tooth thickness modification machining method for a dual-lead worm gear according to an embodiment of the present invention;

[0070] Figure 2 This is a logic block diagram illustrating how the disturbance level in the current processing stage is determined based on a disturbance intensity index, according to an embodiment of the present invention.

[0071] Figure 3 This is a logic block diagram of an embodiment of the present invention for determining whether the current control effect is qualified based on the attenuation coefficient of tooth thickness variation;

[0072] Figure 4 This is a logic block diagram illustrating how the optimization magnitude of processing parameters is determined based on the absolute attenuation difference in an embodiment of the present invention. Detailed Implementation

[0073] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0074] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0075] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0076] Please see Figure 1 The diagram shown is a schematic representation of the steps in the variable tooth thickness profile machining method for a dual-lead worm gear according to an embodiment of the present invention.

[0077] The present invention provides a method for variable tooth thickness profile machining of a double-lead worm gear, comprising:

[0078] Step S1: Based on the hob rotating at a predetermined speed, obtain the waveform distortion rate of the hob's idling cutting force and the hob's torsional stiffness coefficient.

[0079] The hob is a standard involute hob, and the predetermined rotational speed is 100 r / min to 200 r / min, preferably 150 r / min.

[0080] Step S2: Continuously acquire the real-time cutting force signal of the hob and the radial displacement of the hob shank. Based on the real-time cutting force signal, determine the real-time cutting force waveform distortion rate and real-time cutting force waveform distortion frequency of the hob. Based on the radial displacement and the hob torsional stiffness coefficient, determine the real-time tool torsional deformation of the hob.

[0081] Step S3: Based on the real-time cutting force waveform distortion rate and the idle cutting force waveform distortion rate, the distortion increment is calculated, and combined with the real-time tool torsional deformation, the disturbance intensity index is calculated. The disturbance level in the current machining process is determined according to the disturbance intensity index, and the detection timing parameters for the tooth groove are set according to the disturbance level.

[0082] Step S4: When the set detection time is reached, the actual tooth thickness values ​​at several positions of the current tooth groove are obtained, and based on the theoretical tooth thickness values ​​at several positions, the tooth thickness deviation values ​​at several positions are calculated. Based on the tooth thickness deviation values, a first actual tooth thickness variation curve is generated, and a first tooth thickness variation rate coefficient is calculated. Based on the first tooth thickness variation rate coefficient, it is determined whether the processing of the current tooth groove is qualified.

[0083] Step S5: Under the condition that the machining quality of the current tooth groove is unqualified, perform Fourier transform on the first actual tooth thickness variation curve, extract the frequency component with the largest amplitude as the deviation main frequency, determine the current dominant interference type according to the difference between the deviation main frequency and the distortion frequency of the real-time cutting force waveform, and adjust the current machining parameters according to the dominant interference type and the disturbance level.

[0084] Step S6: Under the condition of completing the adjustment, continue to process the next tooth groove. After reaching the set detection time, obtain the second actual tooth thickness change curve after adjustment, and calculate the second tooth thickness change rate coefficient. Based on the second tooth thickness change rate coefficient, calculate the tooth thickness change attenuation coefficient, and determine whether the current adjustment effect is qualified according to the tooth thickness change attenuation coefficient.

[0085] Step S7: If the current control effect is not up to standard, determine the optimization range of the processing parameters based on the absolute attenuation difference between the tooth thickness change attenuation coefficient and the preset tooth thickness change attenuation coefficient, and perform optimization according to the dominant interference type.

[0086] Step S8: Under the condition of optimization, continue to process all tooth grooves until processing is completed, obtain the tooth thickness variation curve of each tooth groove along the tooth width direction and the total number of tooth grooves, calculate the tooth thickness variation rate uniformity coefficient that characterizes the uniformity of tooth thickness variation of all tooth grooves of the formed worm wheel, and determine whether the quality of the current formed worm wheel is qualified based on the tooth thickness variation rate uniformity coefficient.

[0087] Specifically, this invention determines the characteristic benchmark of the tool-spindle system by collecting the waveform distortion rate and torsional stiffness coefficient of the hob during idle cutting before machining, solving the technical problem that traditional methods cannot distinguish between the inherent characteristics of the tool and the disturbances introduced by machining. By fusing the real-time cutting force waveform distortion increment with the real-time tool torsional deformation to calculate the disturbance intensity index, it achieves a quantitative characterization of the mutually reinforcing effect of resonance risk and tool deformation risk caused by the asymmetry of the cutting edge distribution. Based on this index, the detection timing is dynamically set, so that the detection timing is precisely matched with the machining risk, solving the contradiction between efficiency and quality under a fixed detection frequency. By analyzing the tooth thickness deviation curve of the defective tooth groove and extracting the deviation main frequency, and comparing it with the cutting force waveform distortion frequency, it achieves precise tracing of the root cause of the tooth thickness machining deviation, enabling the control measures to be precisely adjusted for different root causes. The system adjusts the speed based on the type and level of interference. Under resonance-dominant conditions, the speed adjustment is calculated by the deviation of the main frequency from the machine tool's natural frequency. Under deformation-dominant conditions, the X-axis position compensation and C-axis attitude compensation are calculated by real-time torsional deformation and disturbance intensity indicators. This achieves dynamic matching between the adjustment range and the severity of the disturbance, avoiding over- or under-adjustment. The attenuation coefficient of tooth thickness variation is calculated by the attenuation of the tooth thickness variation rate coefficient before and after adjustment, quantitatively verifying the adjustment effect. When the standard is not met, the adjustment coefficient is automatically optimized based on the absolute attenuation difference, making the machining parameters more and more accurate over time. The uniformity coefficient of tooth thickness variation rate is calculated by the ratio of the standard deviation to the average value of the tooth thickness variation rate coefficient across the entire tooth surface. Based on this, the quality of the variable tooth thickness worm gear machined is determined, solving the deep-seated problem that traditional single-tooth-groove inspection cannot assess the consistency of the entire tooth surface, thus improving the machining quality of variable tooth thickness worm gears.

[0088] In this embodiment of the invention, step S1, which involves obtaining the waveform distortion rate of the hob's idling cutting force and the torsional stiffness coefficient of the hob before machining, includes:

[0089] Step S11: Install the standard involute hob on the spindle of the CNC gear hobbing machine, adjust the machine tool so that the hob and the worm gear blank are in a non-contact state, and drive the hob to idle at a predetermined speed.

[0090] Step S12: The three-dimensional dynamic force sensor installed on the spindle bearing housing continuously collects the cutting force time-domain signal during hob idling, with a sampling frequency not less than 100 times the hob rotation frequency. Simultaneously, the angle position signal of the spindle is acquired in real time by the angle encoder installed on the hob spindle. Using the zero-position pulse corresponding to each revolution of the hob in the angle position signal as the trigger signal, the cutting force time-domain signal is truncated for an entire cycle. The cutting force waveform data within a complete revolution of the hob is extracted, and the ratio of the maximum amplitude to the average amplitude of the cutting force waveform within the entire cycle is calculated as the hob idling cutting force waveform distortion rate.

[0091] Step S13: A tangential force is applied to the position of the hob bar near the cutting edge by an electric cylinder mounted on the tool holder. The loading direction is perpendicular to the axis of the tool bar and tangential to the tool bar. During the loading process, the tangential force value is measured in real time by a force sensor mounted on the loading device. At the same time, the torsion angle of the tool bar under the action of the tangential force is measured by an angle encoder. The magnitude of the tangential force is changed, and at least three loading-unloading cycles with different loads are performed. A curve is plotted with the torque generated by the tangential force as the abscissa and the torsion angle as the ordinate. The slope of the curve is fitted and used as the hob torsional stiffness coefficient.

[0092] The torque is the product of the tangential force and the radius of the hob bar.

[0093] In this embodiment of the invention, step S2, which involves obtaining the real-time cutting force waveform distortion rate, the real-time cutting force waveform distortion frequency, and the real-time tool torsional deformation during gear hobbing, includes the following steps:

[0094] Step S21: During the gear hobbing process, a three-dimensional dynamic force sensor installed on the spindle bearing housing continuously collects the real-time three-dimensional cutting force signal when the hob cuts the worm gear blank at a sampling frequency of not less than 100 times the hob rotation frequency.

[0095] The three-axis cutting force signal includes mutually perpendicular force components F_x in the X-axis direction, F_y in the Y-axis direction, and F_z in the Z-axis direction, wherein the X-axis, Y-axis, and Z-axis are orthogonal coordinate axes fixed to the machine tool coordinate system;

[0096] Step S22: The angle position signal of the spindle is acquired in real time by an angle encoder installed on the hob spindle. The angle position signal represents the real-time rotation angle of the hob in the machine tool coordinate system. Based on the angle position signal, the X-axis force component and the Y-axis force component are transformed into coordinates. The real-time tangential cutting force component of the hob in the rotation tangential direction is calculated according to the following formula.

[0097] ;

[0098] In the formula, For the real-time tangential cutting force component, The force component in the X-axis direction. This represents the current angle and position of the hobbing cutter. This represents the force component along the y-axis.

[0099] Step S23: Simultaneously, using the zero-position pulse corresponding to each revolution of the hob in the angle position signal as the trigger signal, the real-time cutting force signal is subjected to sliding window-type whole-cycle interception to obtain the cutting force waveform data in the most recent complete rotation cycle before the current moment.

[0100] Step S24: For the cutting force waveform data within each captured complete rotation cycle, the ratio of the maximum amplitude to the average amplitude of the cutting force waveform within the complete rotation cycle is taken as the real-time cutting force waveform distortion rate at the current moment; simultaneously, a fast Fourier transform is performed on the waveform data within the complete rotation cycle to extract the frequency value with the largest amplitude in the spectrum, and the frequency value is taken as the real-time cutting force waveform distortion frequency at the current moment. After each rotation cycle is completed, the real-time cutting force waveform distortion rate and the real-time cutting force waveform distortion frequency are updated once.

[0101] Step S25: Based on the hob torsional stiffness coefficient obtained in step S1 and the tangential cutting force component obtained through the above coordinate transformation, calculate the real-time tool torsional deformation according to the following formula.

[0102] ;

[0103] In the formula, This represents the real-time torsional deformation of the cutting tool. The real-time tangential cutting force component is given by R, where R is the radius of the hob shank. This represents the torsional stiffness coefficient of the hob.

[0104] Specifically, the disturbance level in the current processing is determined based on the comparison result between the disturbance intensity index and the first preset disturbance intensity index and the second preset disturbance intensity index, and the detection timing parameters for the current tooth groove are set according to the disturbance level, wherein,

[0105] If the disturbance intensity index is less than or equal to the first preset disturbance intensity index, the disturbance level in the current processing process is determined to be a mild disturbance, and a detection is performed after processing three tooth grooves.

[0106] If the disturbance intensity index is greater than the first preset disturbance intensity index and less than or equal to the second preset disturbance intensity index, then the disturbance level in the current processing process is determined to be medium disturbance, and a detection is set to be performed after each tooth groove is processed.

[0107] If the disturbance intensity index is greater than the second preset disturbance intensity index, the disturbance level in the current processing process is determined to be a severe disturbance, and processing is stopped.

[0108] In this embodiment of the invention, the specific process for obtaining the disturbance intensity index is as follows:

[0109] Step S31: Obtain the real-time cutting force waveform distortion rate and the idle cutting force waveform distortion rate, and use the difference between the real-time cutting force waveform distortion rate and the idle cutting force waveform distortion rate as the distortion increment;

[0110] Step S32: Obtain the real-time torsional deformation of the tool, and multiply the real-time torsional deformation of the tool by the distortion increment to obtain the strength disturbance index;

[0111] In this embodiment of the invention, the first preset disturbance interference index is the critical value between mild and moderate disturbance, and the second preset disturbance interference index is the critical value between moderate and severe disturbance. The specific methods for obtaining the first and second preset disturbance interference indices are as follows: a standard involute hob is installed on a CNC gear hobbing machine, and at least 10 worm gear tooth grooves are continuously machined under normal process parameters. The disturbance intensity index during the machining process of each tooth groove is collected in real time, and its average value μ and standard deviation σ are calculated. The average value μ plus one standard deviation σ is used as the first preset disturbance interference index, with a value range of 0.01 rad to 0.02 rad, preferably 0.015 rad. The average value μ plus two standard deviations σ is used as the second preset disturbance interference index, with a value range of 0.02 rad to 0.04 rad, preferably 0.025 rad. The preferred value range and preferred value can be calibrated according to the actual dynamic characteristics of the machine tool and the machining accuracy requirements, and are not specifically limited here.

[0112] Please see Figure 2 As shown, it is a logic block diagram of an embodiment of the present invention for determining whether the tooth groove quality processed by the current hob is qualified based on the first tooth thickness change rate coefficient.

[0113] Specifically, the quality of the tooth groove processed by the current hob is determined based on the comparison between the first tooth thickness variation rate coefficient and the preset first tooth thickness variation rate coefficient.

[0114] If the first tooth thickness change rate coefficient is less than or equal to the preset first tooth thickness change rate coefficient, then the tooth groove quality based on the current hob machining is determined to be qualified.

[0115] If the first tooth thickness change rate coefficient is greater than the preset first tooth thickness change rate coefficient, then the tooth groove quality based on the current hob machining is determined to be unqualified.

[0116] In this embodiment of the invention, the process of generating the first actual tooth thickness variation curve and calculating the first tooth thickness variation rate coefficient includes:

[0117] Step S41: When the set detection timing is reached, pause the hobbing process. Use a laser displacement sensor mounted on the tool holder to perform equal-interval scanning along the worm gear tooth width direction to obtain the actual tooth thickness values ​​at at least 10 different positions of the current tooth groove. Record the tooth width position coordinates Xi and the actual tooth thickness value corresponding to each measurement point. , where i=1,2,…,n, and n is the total number of measurement points;

[0118] Step S42: Obtain the theoretical tooth thickness value of the current tooth groove at each measurement point. The theoretical tooth thickness value is calculated in advance based on the design parameters of the double-lead worm and the target of variable tooth thickness modification of the worm wheel;

[0119] Step S43: Calculate the first tooth thickness deviation value at each measurement point. The first tooth thickness deviation value is... - Using the tooth width position as the horizontal axis and the first tooth thickness deviation value as the vertical axis, a first actual tooth thickness variation curve is generated.

[0120] Step S44: Perform linear least squares fitting on the data points of the first actual tooth thickness variation curve to obtain the fitting line k·X+b, where X is the tooth width position coordinate and b is the intercept of the fitting line, i.e. the tooth thickness deviation estimate at X=0. The absolute value of the slope k of the fitting line is used as the first tooth thickness variation rate coefficient.

[0121] In this embodiment of the invention, the preset first tooth thickness variation rate coefficient is calibrated based on the design allowable tooth thickness deviation variation rate, and the value range is 0.005 to 0.015, preferably 0.01. The preferred value range and preferred value can be determined according to the actual situation, and are not specifically limited here.

[0122] Specifically, this invention determines the characteristic benchmark of the tool-spindle system by acquiring the waveform distortion rate and torsional stiffness coefficient of the hob's idle cutting force before machining, thus solving the technical problem that traditional methods cannot distinguish between the inherent characteristics of the tool and the disturbances introduced by machining. Through coordinate transformation, the tangential cutting force component is calculated in real time from the three-dimensional cutting force signal, and combined with the torsional stiffness coefficient, the real-time cutting force waveform distortion rate, distortion frequency, and tool torsional deformation are simultaneously obtained, achieving real-time quantitative perception of the resonance risk and tool deformation risk caused by the asymmetry of the cutting edge distribution. Furthermore, by fusing the incremental cutting force waveform distortion with the tool torsional deformation, the disturbance is calculated... The dynamic strength index is used to determine the current disturbance level and dynamically set the detection timing according to the disturbance level. Specifically, for mild disturbances, an inspection is performed every three slots to improve processing efficiency, while for severe disturbances, an inspection is performed on every slot to ensure processing quality. This ensures that the detection strategy is precisely matched with processing risks, resolving the contradiction between efficiency and quality under a fixed detection frequency. By linearly fitting the tooth thickness deviation curve of the defective tooth slots to extract the tooth thickness change rate coefficient, the abstract tooth surface quality is transformed into a quantifiable index. This allows for accurate determination of whether the current processing parameters are acceptable for the tooth slot processing quality, effectively reducing the accumulation of errors during continuous processing.

[0123] Specifically, the current dominant interference type is determined based on the comparison between the frequency difference and the preset frequency difference, and the adjustment range of the current processing parameters is determined based on the dominant interference type and the disturbance level.

[0124] If the frequency difference is less than the preset frequency difference, then the current dominant interference type is determined to be resonance-dominant.

[0125] If the frequency difference is greater than or equal to the preset frequency difference, then the current dominant interference type is determined to be the variant dominant type.

[0126] In this embodiment of the invention, the specific process for obtaining the frequency difference is as follows;

[0127] Step S51: Under the condition that the current machining quality of the tooth groove is unqualified, perform fast Fourier transform on the data points of the first tooth thickness variation curve, convert the tooth thickness deviation distribution in the time domain into a spectrum distribution in the frequency domain, and extract the frequency component with the largest amplitude in the spectrum distribution as the deviation main frequency.

[0128] Step S52: Obtain the distortion frequency of the real-time cutting force waveform, and use the absolute difference between the deviation main frequency and the distortion frequency of the real-time cutting force waveform as the frequency difference.

[0129] In this embodiment of the invention, the preset frequency difference is obtained by hammer impact modal test calibration, and the value range is 5Hz to 15Hz, preferably 10Hz. The preferred value range and preferred value can be determined according to the actual situation, and are not specifically limited here.

[0130] In this embodiment of the invention, based on the dominant type being resonance-dominant, if the disturbance level is a slight disturbance, then the first control amplitude is determined;

[0131] Specifically, the first adjustment range is to reduce the spindle speed in the current machining state by a first spindle speed adjustment amount. Specifically, the first spindle speed adjustment amount is calculated according to the following formula.

[0132] ;

[0133] In the formula, This is the adjustment amount for the first spindle speed. This is the current spindle speed. The first speed adjustment coefficient is obtained by calibration based on the machine tool response characteristics. The value ranges from 0.1 to 0.3, with 0.15 being the preferred value. For the deviation of the main frequency, This is the machine tool's inherent frequency.

[0134] Subtract the first spindle speed adjustment amount from the current spindle speed to perform secondary machining on the current tooth groove, and obtain the adjusted spindle speed for subsequent tooth groove machining.

[0135] If the disturbance is equal to a severe disturbance, then the second control amplitude is determined.

[0136] Specifically, the second adjustment range is to reduce the spindle speed in the current machining state by a second spindle speed adjustment amount. Specifically, the second spindle speed adjustment amount is calculated according to the following formula.

[0137] ;

[0138] In the formula, This is the adjustment amount for the second spindle speed. This is the current spindle speed. The second speed adjustment coefficient is obtained by calibration based on the machine tool response characteristics. The value ranges from 0.4 to 0.6, with 0.45 being the preferred value. For the deviation of the main frequency, The machine tool's inherent frequency, This is the current disturbance intensity index. This is a preset disturbance intensity index.

[0139] Subtract the second spindle speed adjustment amount from the current spindle speed to perform secondary machining on the current tooth groove, and obtain the adjusted spindle speed for subsequent tooth groove machining.

[0140] In this embodiment of the invention, based on the dominant type being a deformed dominant type, if the disturbance level is a slight disturbance, then the third control amplitude is determined;

[0141] Specifically, the third adjustment range is to adjust the current position of the hob's X-axis by the first X-axis position compensation amount to counteract the radial offset of the cutting trajectory caused by torsional deformation. The first X-axis position compensation amount is calculated according to the following formula.

[0142] ;

[0143] In the formula, This is the first X-axis position compensation amount. The displacement compensation coefficient is calibrated by measuring the ratio of the actual radial offset of the hob holder under unit torque to the theoretical radial offset. Its value ranges from 0.8 to 1.2, with 1.0 being preferred. This represents the real-time torsional deformation of the cutting tool. The radius of the hob cutter shank is given.

[0144] Add the first X-axis position compensation amount to the current hob X-axis position, perform secondary machining on the current tooth groove, and obtain the adjusted hob X-axis position for subsequent tooth groove machining.

[0145] If the disturbance is equal to a severe disturbance, then the fourth control amplitude is determined.

[0146] Specifically, the fourth adjustment range involves adjusting the current hob's X-axis position using the second X-axis position compensation amount and adjusting the cutting edge attitude angle using the C-axis compensation amount to counteract the radial offset of the cutting trajectory caused by torsional deformation. The second X-axis position compensation amount and the C-axis compensation amount are calculated according to the following formula to compensate for the cutting edge attitude angle offset caused by torsional deformation.

[0147] ;

[0148] ;

[0149] In the formula, This is the second X-axis position compensation amount. The displacement compensation coefficient is calibrated by measuring the ratio of the actual radial offset of the hob holder to the theoretical radial offset under unit torque. Its value ranges from 1.3 to 1.8, with 1.5 being preferred. This represents the real-time torsional deformation of the cutting tool. The radius of the hob shank is... This is the current disturbance intensity index. To preset the disturbance intensity index, This is the C-axis compensation amount. The angle compensation coefficient is calibrated by measuring the ratio of the actual torsional angle of the hob bar under unit torque to the theoretical torsional angle. The value range is 0.5 to 1.5, with 1.0 being preferred.

[0150] The current position of the hob on the X-axis is added to the second X-axis position compensation amount, and the current position of the hob on the C-axis is added to the C-axis compensation amount. The current tooth groove is then processed a second time to obtain the adjusted hob X-axis and C-axis positions for subsequent tooth groove processing.

[0151] Please see Figure 3 As shown, it is a logic block diagram of an embodiment of the present invention for determining whether the current control effect is qualified based on the attenuation coefficient of tooth thickness change.

[0152] Specifically, the current control effect is determined to be satisfactory based on the comparison between the tooth thickness variation attenuation coefficient and the preset tooth thickness variation attenuation coefficient.

[0153] If the tooth thickness variation attenuation coefficient is less than the preset tooth thickness variation attenuation coefficient, then the current control effect is determined to be unqualified.

[0154] If the tooth thickness variation attenuation coefficient is greater than or equal to the preset tooth thickness variation attenuation coefficient, then the current control effect is determined to be qualified.

[0155] In this embodiment of the invention, the specific process for obtaining the tooth thickness variation attenuation coefficient is as follows:

[0156] Step S61: After completing the secondary machining of the current tooth groove, continue machining the next tooth groove. When the set detection time is reached, pause the hobbing feed. Use a laser displacement sensor mounted on the tool holder to perform equal-interval scanning along the worm gear tooth width direction to obtain the second actual tooth thickness value of the current tooth groove at at least 10 different positions. Record the tooth width position coordinates Xj and the second actual tooth thickness value corresponding to each measurement point. , where j=1,2,…,m, and m is the total number of measurement points;

[0157] Step S62: Obtain the theoretical tooth thickness value of the current tooth groove at each measurement point. And calculate the second tooth thickness deviation value at each measurement point, the second tooth thickness deviation value is - Using the tooth width position as the horizontal axis and the second tooth thickness deviation value as the vertical axis, a second actual tooth thickness variation curve is generated.

[0158] Step S63: Perform linear least squares fitting on the data points of the second actual tooth thickness variation curve to obtain the fitting line k'·X+b', where X is the tooth width position coordinate and b' is the intercept of the fitting line, i.e. the tooth thickness deviation estimate at X=0. The absolute value of the slope k' of the fitting line is used as the second tooth thickness variation rate coefficient.

[0159] Step S64: Divide the difference between the first tooth thickness change rate coefficient and the second tooth thickness change rate coefficient by the first tooth thickness change rate coefficient to obtain the tooth thickness change attenuation coefficient.

[0160] In this embodiment of the invention, the preset tooth thickness variation attenuation coefficient is calibrated by the accuracy grade and tooth thickness tolerance requirements of the worm gear, and the value range is 0.6 to 0.9, preferably 0.75. The preferred value range and preferred value can be determined according to the actual situation, and are not specifically limited here.

[0161] Specifically, this invention analyzes the tooth thickness deviation curve of defective tooth grooves, extracts the dominant frequency of the deviation, and compares it with the distortion frequency of the real-time cutting force waveform. This enables precise tracing of the root cause of tooth thickness deviation. Specifically, when the frequency difference is less than a preset value, it is determined to be a resonance-dominant type, indicating that the deviation is mainly caused by machine tool resonance excited by the distortion of the cutting force waveform; when the frequency difference is greater than or equal to the preset value, it is determined to be a deformation-dominant type, indicating that the deviation is mainly caused by the cutting trajectory deviation caused by the torsional deformation of the tool. This solves the technical problem that traditional methods cannot distinguish the root cause of deviation and can only blindly try and fail. It also performs graded control based on the dominant interference type and disturbance level. Under the resonance-dominant mode, the speed adjustment is calculated by the deviation of the main frequency from the machine tool's natural frequency. Under the deformation-dominant mode, the X-axis position compensation and C-axis attitude compensation are calculated by real-time torsional deformation and disturbance intensity indicators, achieving precise matching between the control object and the root cause of the influence, and between the control amplitude and the risk level. The tooth thickness change attenuation coefficient is calculated by the attenuation degree of the tooth thickness change rate coefficient before and after control, which can transform the abstract control effect into a quantifiable attenuation ratio, achieving objective verification of the effectiveness of the control measures. This solves the problem of traditional methods that only control without detecting the control effect, effectively reducing the accumulation of machining quality errors and improving the machining quality of variable tooth thickness worm gears.

[0162] Please see Figure 4 As shown, it is a logic block diagram of an embodiment of the present invention for determining the optimization magnitude of processing parameters based on the absolute attenuation difference.

[0163] Specifically, when it is determined that the current control effect is not up to standard, the optimization range of the machining parameters is determined based on the comparison between the absolute attenuation difference of the tooth thickness variation attenuation coefficient and the preset absolute attenuation difference, and optimization is performed according to the dominant interference type.

[0164] If the absolute attenuation difference is less than or equal to the preset absolute attenuation difference, then the optimization range of the processing parameters is determined to be the first optimization range.

[0165] If the absolute attenuation difference is greater than the preset absolute attenuation difference, then the optimization range of the processing parameters is determined to be the second optimization range.

[0166] In this embodiment of the invention, based on the fact that the dominant interference type is resonance-dominant, the first optimization amplitude is used to correct the speed adjustment coefficient with a first optimization coefficient to obtain a corrected speed adjustment coefficient value. The corrected speed adjustment coefficient value is calculated according to the following formula.

[0167] ;

[0168] ;

[0169] In the formula, This is the correction value for the first speed adjustment coefficient. As the first optimization coefficient, This is the correction value for the second speed adjustment coefficient.

[0170] The second optimization range involves correcting the speed adjustment coefficient using a second optimization coefficient to obtain a corrected speed adjustment coefficient value, which is calculated according to the following formula.

[0171] ;

[0172] ;

[0173] In the formula, This is the correction value for the first speed adjustment coefficient. This is the first speed adjustment coefficient. This is the second optimization coefficient. This is the correction value for the second speed adjustment coefficient. This is the second speed adjustment coefficient.

[0174] In this embodiment of the invention, based on the fact that the dominant interference type is deformation-dominant, the first optimization amplitude is used to correct the displacement compensation coefficient and the angle compensation coefficient with a first optimization coefficient to obtain the corrected values ​​of the displacement compensation coefficient and the angle compensation coefficient. The corrected values ​​of the displacement compensation coefficient and the angle compensation coefficient are calculated according to the following formula.

[0175] ;

[0176] ;

[0177] In the formula, This is the correction value for the displacement compensation coefficient. This is the displacement compensation coefficient. As the first optimization coefficient, This is the correction value for the angle compensation coefficient. This is the angle compensation coefficient.

[0178] The second optimization range involves correcting the displacement compensation coefficient and the angle compensation coefficient using a second optimization coefficient, resulting in corrected values ​​for the displacement compensation coefficient and the angle compensation coefficient. These corrected values ​​are calculated using the following formula.

[0179] ;

[0180] ;

[0181] In the formula, This is the correction value for the displacement compensation coefficient. This is the displacement compensation coefficient. This is the second optimization coefficient. This is the correction value for the angle compensation coefficient. This is the angle compensation coefficient.

[0182] In this embodiment of the invention, the first optimization coefficient and the second optimization coefficient are calibrated through a finite number of process experiments to obtain a basic optimization step size factor. The processing parameters are then optimized once using the basic optimization step size factor, and the first optimization coefficient and the second optimization coefficient are determined based on the actual number of optimizations.

[0183] The basic optimization step size factor characterization system has a response sensitivity to the control parameters ranging from 0.05 to 0.1, preferably 0.08.

[0184] Wherein, when the optimization range is the first optimization range, the first optimization coefficient is the basic optimization step size factor multiplied by the first actual optimization number; when the optimization range is the second optimization range, the second optimization coefficient is the basic optimization step size factor multiplied by the second actual optimization number.

[0185] In this embodiment of the invention, the first actual number of optimizations ranges from 1 to 5 times, preferably 2 times, and the second actual number of optimizations ranges from 5 to 8 times, preferably 6 times. The preferred range and preferred value can be determined according to the actual situation, and are not specifically limited here.

[0186] Specifically, under optimized conditions, the quality of the current formed worm gear is determined to be qualified based on the comparison between the tooth thickness variation rate uniformity coefficient and the preset tooth thickness variation rate uniformity coefficient.

[0187] If the uniformity coefficient of tooth thickness variation rate is less than the preset uniformity coefficient of tooth thickness variation rate, then the quality of the currently formed worm gear is determined to be unqualified.

[0188] If the uniformity coefficient of tooth thickness variation rate is greater than or equal to the preset uniformity coefficient of tooth thickness variation rate, then the quality of the currently formed worm gear is determined to be qualified.

[0189] In this embodiment of the invention, the specific method for obtaining the uniformity coefficient of tooth thickness variation rate is as follows:

[0190] Step S81: After optimization and machining of all tooth grooves, the machined worm gear is inspected on its entire tooth surface using a laser displacement sensor mounted on the tool holder. The tooth thickness variation curve of each tooth groove along the tooth width direction is obtained, and the total number of tooth grooves is recorded.

[0191] Step S82: For each tooth groove, obtain the tooth thickness variation rate coefficient of each tooth groove in the same way as in step S44 or step S63, and calculate the average value and standard deviation of the tooth thickness variation rate coefficients of all tooth grooves.

[0192] Step S83: Calculate the ratio of the standard deviation to the average value, and subtract the difference of the ratio from 1 to obtain the uniformity coefficient of the tooth thickness variation rate.

[0193] In this embodiment of the invention, the preset tooth thickness variation rate uniformity coefficient is the minimum allowable consistency coefficient of the tooth groove of the entire tooth surface of the formed worm gear. By performing full tooth surface inspection on several batches of qualified formed worm gears, the tooth thickness variation rate uniformity coefficient of the entire tooth surface of each worm gear is statistically analyzed. The mean value minus the standard deviation of the statistical results is taken as the preset tooth thickness variation rate uniformity coefficient, with a value range of 0.85 to 0.95, preferably 0.90. The preferred value range and preferred value can be determined according to the actual situation, and are not specifically limited here.

[0194] Specifically, this invention quantifies the degree of control deviation by calculating the absolute attenuation difference between the tooth thickness variation attenuation coefficient and the preset attenuation coefficient when the control effect fails to meet the standard. This solves the problem of mismatch between optimization intensity and deviation degree caused by the traditional method of uniformly treating all non-compliance. The optimization amplitude is determined based on the dominant interference type. Specifically, the speed adjustment coefficient is corrected under resonance-dominant conditions, and the displacement compensation coefficient and angle compensation coefficient are corrected under deformation-dominant conditions, achieving a precise correspondence between the optimization object and the root cause of the deviation. The basic optimization step size factor is calibrated through a limited number of process experiments, and the optimization coefficient is dynamically determined based on the actual number of optimizations, avoiding slow optimization or overshoot oscillation of the machine tool caused by fixed step size optimization. After completing the machining of all tooth slots, the tooth thickness variation rate uniformity coefficient is calculated by calculating the ratio of the standard deviation to the average value of the tooth thickness variation rate coefficient of each tooth slot. This solves the problem of the traditional method only focusing on the qualification of a single tooth slot and failing to assess the consistency of the entire tooth surface, making the machining parameters more accurate with use, improving the machining quality of high-precision dual-lead worm gears, and reducing the scrap rate.

[0195] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for modifying a variable tooth thickness profile of a double lead worm gear, characterized by, include, Obtain the waveform distortion rate of the idling cutting force and the torsional stiffness coefficient of the hob when it is idling at a predetermined speed; Based on the three-phase cutting force signal of the hob, the real-time cutting force waveform distortion rate and real-time cutting force waveform distortion frequency of the hob are obtained, and the real-time tool torsional deformation of the hob is determined. Based on the real-time cutting force waveform distortion rate and the idle cutting force waveform distortion rate, the disturbance intensity index of the hob on the machining process is obtained to determine the disturbance level in the current machining process and set the detection timing for the tooth groove. Obtain the actual tooth thickness values ​​at several positions of the current tooth groove, generate the first actual tooth thickness variation curve, and determine the first tooth thickness variation rate coefficient to determine whether the tooth groove quality based on the current hob is qualified. Based on the first actual tooth thickness variation curve, the deviation main frequency is determined to determine the current dominant interference type, and based on the disturbance level, the current machining parameters are adjusted by the spindle speed adjustment amount and the spindle position compensation amount. Obtain the second tooth thickness change rate coefficient after adjustment, and obtain the tooth thickness change attenuation coefficient to determine whether the current adjustment effect is qualified; Based on the absolute attenuation difference between the tooth thickness variation attenuation coefficient and the preset tooth thickness variation attenuation coefficient, the amount of spindle speed adjustment and the amount of spindle position compensation are determined by the optimization coefficient. Obtain the uniformity coefficient of tooth thickness variation rate, which characterizes the uniformity of tooth thickness variation across all tooth grooves of the formed worm gear, to determine the quality of the current formed worm gear.

2. The variable tooth thickness profile machining method for a double-lead worm gear according to claim 1, characterized in that, The process of determining the disturbance level in the current machining process and setting the timing for detecting the tooth groove includes, The distortion increment is calculated based on the real-time cutting force waveform distortion rate and the idle cutting force waveform distortion rate. The disturbance intensity index is calculated based on the distortion increment and the real-time tool torsional deformation. Based on the fact that the disturbance intensity index is less than or equal to the first preset disturbance intensity index, the disturbance level in the current processing process is determined to be a slight disturbance, and a detection is performed after every three tooth grooves are processed.

3. The variable tooth thickness profile machining method for a double-lead worm gear according to claim 2, characterized in that, The process of determining the disturbance level in the current machining process and setting the timing for detecting the tooth grooves also includes, Based on the fact that the disturbance intensity index is greater than the first preset disturbance intensity index and less than or equal to the second preset disturbance intensity index, the disturbance level in the current processing process is determined to be medium disturbance, and a detection is set to be performed after each tooth groove is processed. If the disturbance intensity index is greater than the second preset disturbance intensity index, the disturbance level in the current processing process is determined to be a severe disturbance, and processing is stopped. Wherein, the first preset disturbance intensity index is less than the second preset disturbance intensity index.

4. The variable tooth thickness profile machining method for a double-lead worm gear according to claim 3, characterized in that, The process of determining whether the tooth groove quality based on the current hob machining is qualified includes, Obtain the first actual tooth thickness value at at least 10 different locations of the current tooth groove; The first tooth thickness deviation value is calculated based on the first actual tooth thickness value and the theoretical tooth thickness value. Using the tooth width position as the abscissa and the first tooth thickness deviation value as the ordinate, a first actual tooth thickness variation curve is generated, and the slope value is calculated as the first tooth thickness variation rate coefficient. Based on the fact that the first tooth thickness change rate coefficient is greater than the preset first tooth thickness change rate coefficient, it is determined that the tooth groove quality processed by the current hob is unqualified.

5. The variable tooth thickness profile machining method for a double-lead worm gear according to claim 4, characterized in that, The process of determining the current dominant disturbance type and, based on the disturbance level, adjusting the current machining parameters by the spindle speed adjustment amount includes: Analyze the first actual tooth thickness variation curve and extract the frequency component with the largest amplitude in the spectrum distribution as the deviation main frequency; The frequency difference is calculated based on the distortion frequency of the real-time cutting force waveform and the dominant frequency of the deviation. Based on the fact that the frequency difference is less than a preset frequency difference, the current dominant interference type is determined to be resonance-dominant. Based on the fact that the current disturbance level is a slight disturbance, it is determined that the spindle speed in the current machining state will be reduced by the first spindle speed adjustment amount; The first spindle speed adjustment amount is obtained by multiplying the current spindle speed, the first speed adjustment coefficient, and the ratio of the deviation of the main frequency to the machine tool's natural frequency. Based on the fact that the disturbance level is severe, it is determined that the spindle speed in the current machining state will be reduced by the second spindle speed adjustment amount; The second spindle speed adjustment amount is obtained by multiplying the current spindle speed, the second speed adjustment coefficient, the ratio of the deviation of the main frequency to the machine tool's natural frequency, and the ratio of the current disturbance intensity index to the preset disturbance intensity index.

6. The variable tooth thickness profile machining method for a double-lead worm gear according to claim 5, characterized in that, The process of determining the current dominant disturbance type and, based on the disturbance level, adjusting the current machining parameters by the spindle position compensation includes: Based on the frequency difference being greater than or equal to a preset frequency difference, the current dominant interference type is determined to be a deformable dominant type. Based on the fact that the current disturbance level is a slight disturbance, it is determined that the position of the current hob X-axis will be adjusted by the first X-axis position compensation amount; The first X-axis position compensation amount is obtained by multiplying the hob bar radius, the displacement compensation coefficient, and the real-time tool torsional deformation amount. Based on the fact that the current disturbance level is severe, it is determined that the position of the current hob X-axis is adjusted by the second X-axis position compensation amount, and the cutting edge attitude angle is adjusted by the C-axis compensation amount. The adjustment of the second X-axis position compensation amount is obtained by multiplying the hob bar radius, displacement compensation coefficient, real-time tool torsional deformation amount, and the ratio of the current disturbance intensity index to the preset disturbance intensity index. The C-axis compensation amount is obtained by multiplying the angle compensation coefficient, the real-time tool torsional deformation amount, and the ratio of the current disturbance intensity index to the preset disturbance intensity index.

7. The variable tooth thickness profile machining method for a double-lead worm gear according to claim 6, characterized in that, The process of determining whether the current regulatory effect is satisfactory includes: Obtain the second actual tooth thickness value at at least 10 different locations of the current tooth groove; The second tooth thickness deviation value is calculated based on the second actual tooth thickness value and the theoretical tooth thickness value. Using the tooth width position as the abscissa and the second tooth thickness deviation value as the ordinate, a second actual tooth thickness variation curve is generated, and the slope value is calculated as the second tooth thickness variation rate coefficient. The tooth thickness variation attenuation coefficient is calculated based on the first tooth thickness variation rate coefficient and the second tooth thickness variation rate coefficient. Based on the fact that the tooth thickness change attenuation coefficient is less than the preset tooth thickness change attenuation coefficient, it is determined that the current control effect is unqualified.

8. The variable tooth thickness profile machining method for a double-lead worm gear according to claim 7, characterized in that, The process of determining the spindle speed adjustment and spindle position compensation amount by optimizing the coefficients includes... Based on the fact that the absolute attenuation difference is less than or equal to a preset absolute attenuation difference, the optimization range of the processing parameters is determined as the first optimization range; The first optimization amplitude is based on the fact that the dominant interference type is resonance dominant, and the first speed adjustment coefficient and the second speed adjustment coefficient are corrected by the first optimization coefficient to obtain the first speed adjustment coefficient correction value and the second speed adjustment coefficient correction value; The first optimization magnitude is based on the fact that the dominant disturbance type is deformation-dominant. The displacement compensation coefficient and the angle compensation coefficient are corrected by the first optimization coefficient to obtain the displacement compensation coefficient correction value and the angle compensation coefficient correction value.

9. The variable tooth thickness profile machining method for a double-lead worm gear according to claim 8, characterized in that, The process of determining the spindle speed adjustment and spindle position compensation amount by optimizing the coefficients also includes... Based on the fact that the absolute attenuation difference is greater than the preset absolute attenuation difference, the optimization range corresponding to the processing parameters is determined as the second optimization range; The second optimization amplitude is based on the fact that the dominant interference type is resonance dominant, and the first speed adjustment coefficient and the second speed adjustment coefficient are corrected by the second optimization coefficient to obtain the first speed adjustment coefficient correction value and the second speed adjustment coefficient correction value; The second optimization magnitude is based on the fact that the dominant disturbance type is deformation-dominant. The displacement compensation coefficient and the angle compensation coefficient are corrected by the second optimization coefficient to obtain the displacement compensation coefficient correction value and the angle compensation coefficient correction value.

10. The variable tooth thickness profile machining method for a double-lead worm gear according to claim 9, characterized in that, The process of determining the quality of the current forming worm gear includes... Obtain the tooth thickness variation curve of each tooth groove of the formed worm gear along the tooth width direction, and record the total number of tooth grooves; The uniformity coefficient of tooth thickness variation rate is calculated based on the average value and standard deviation of the tooth thickness variation rate coefficient of all tooth grooves; Based on the fact that the uniformity coefficient of tooth thickness change rate is less than the preset uniformity coefficient of tooth thickness change rate, it is determined that the quality of the current formed worm gear is unqualified and it is rejected. Based on the fact that the uniformity coefficient of tooth thickness change rate is greater than or equal to the preset uniformity coefficient of tooth thickness change rate, the quality of the current formed worm gear is determined to be qualified, and the variable tooth thickness processing is completed.

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