A small-module gear numerical control gear hobbing machine and a control method

Abstract

The application discloses a small-module gear numerical control gear hobbing machine and a control method, and belongs to the technical field of numerical control machine tools. The method comprises the following steps: processing a workpiece based on processing parameters to obtain a formed gear; selecting a plurality of formed gears to perform three-dimensional scanning to obtain corresponding gear models; arranging a plurality of detection points in parallel along the thickness direction of the gear models to detect the opposite surfaces of each gear tooth in the gear models to obtain the processing symmetry of each gear tooth; sequentially connecting the detection points in the same layer to obtain the gear contour of the gear model, and obtaining the processing smoothness based on the gear contour; performing step correction on the processing parameters based on the processing smoothness and the processing symmetry, and calculating the change trend of the processing smoothness and the processing symmetry; and if the processing smoothness and the processing symmetry are not improved, stopping the production of the gear. The application realizes step correction and dynamic closed-loop control of the processing parameters, and ensures that the processing precision and efficiency are synchronously improved.

Description

Technical Field

[0001] This invention belongs to the field of CNC machine tool technology, specifically relating to a small module gear CNC hobbing machine and its control method. Background Technology

[0002] A CNC gear hobbing machine is a CNC machine tool specifically designed for manufacturing gears. It achieves gear cutting through the relative motion between the hob and the workpiece. Compared to traditional mechanical gear hobbing machines, CNC gear hobbing machines integrate a CNC system, allowing for program-controlled cutting paths and achieving high-precision and high-efficiency gear machining. CNC gear hobbing machines are typically equipped with servo motors, which, through the CNC system, control the rotation angle and speed of the hob and workpiece to ensure the correct meshing relationship between the tool and workpiece.

[0003] Existing technologies include methods to ensure gear machining quality, such as Chinese patent document CN111881860A, which discloses a hob wear in-situ identification modeling method and a hob wear in-situ identification method. This method improves the database's ability to express error sources by introducing thermal deformation values ​​and non-uniformity of allowance and optimizing the feature selection process. Combining the advantages of deep learning and artificial features, it achieves high-precision and robust hob wear state identification, and then adjusts control parameters according to the hob wear state.

[0004] However, the above method still determines the wear state of the gear hobbing machine through indirect prediction of current, and then adjusts the parameters of the gear hobbing machine according to the predicted wear state. It lacks direct detection of the actual forming quality of the gear, making it difficult to reflect the processing error in a timely and accurate manner, resulting in deviations in parameter adjustment. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a small-module gear CNC hobbing machine and its control method, thereby resolving the issues present in the background art.

[0006] To achieve the aforementioned objectives, this invention proposes a control method for a small-module gear CNC hobbing machine, comprising: Determine the processing parameters, process the workpiece based on the processing parameters to obtain the formed gear, select multiple formed gears for three-dimensional scanning to obtain the corresponding gear model; A coordinate system is established with the center of the gear model as the origin. Multiple detection points are arranged parallel to the thickness direction of the gear model, and the coordinate values ​​of the detection points are determined. The opposing surfaces of each tooth in the gear model are inspected to obtain the machining symmetry of each tooth; The detection points in the same layer are connected sequentially to obtain the multi-layer gear contour of the gear model in the thickness direction, and the machining smoothness is obtained based on the gear contour; The machining parameters are corrected stepwise based on machining smoothness and machining symmetry. The gear hobbing machine continues to produce gears based on the corrected machining parameters and calculates the changing trends of machining smoothness and machining symmetry. If the smoothness and symmetry of the machining process are not improved, then gear production should be stopped.

[0007] Furthermore, the opposite face of each tooth in the gear model is inspected to obtain the machining symmetry of each tooth, including the following steps: Each tooth in the gear model is divided into a front side, a left side, and a right side. The detection points on the same side and in the same layer of the tooth are connected to obtain multiple side contour lines. The side profiles of the teeth on the same side are superimposed to obtain a first line bundle. The first line bundle is then combined to form a representative profile. The representative profiles of the teeth on opposite sides are superimposed to obtain a second line bundle. An offset analysis is performed on the second line bundle. If the representative profiles do not coincide, the sides corresponding to the two representative profiles are defined as defective sides. The spindle motor current during hobbing is obtained, and the change data of the motor current is converted into the change data of the hob resistance. A resistance change curve is plotted based on the resistance data. If the resistance change curve does not match the standard curve, it is determined that the machining symmetry of the formed gear does not meet the requirements.

[0008] Further, combining the first wire bundle into a representative contour line includes the following steps: A reference line is obtained by connecting the two endpoints of each side profile line. The side profile lines are aligned with the reference line as the target to obtain the first line bundle. The longest reference line is located and defined as the reference line. Multiple reference points are selected on the reference line and mapped to each side profile line to obtain the acquisition points. The coordinate values ​​of the acquisition points corresponding to the same reference point are integrated into a coordinate set. A composite value is calculated in each coordinate direction based on the coordinate set. The composite value is the median or average of the coordinate values. The coordinate point corresponding to the composite value is determined in the coordinate system and defined as the composite point. The composite points are connected sequentially to obtain the representative profile line.

[0009] Further, the offset analysis of the second harness includes the following steps: The composite points in the two representative contour lines in the second line bundle are matched, and the Euclidean distance between the corresponding composite points is calculated. Two composite points with an Euclidean distance greater than a first threshold are defined as deviation positions. If the deviation positions appear consecutively and the number is greater than a second threshold, it is determined that the representative contour line has an offset.

[0010] Furthermore, correcting the processing parameters based on processing symmetry includes the following steps: The abnormal resistance range is located in the resistance change curve. The abnormal resistance range includes the range where the actual resistance value is greater than or lower than the standard resistance value. The processing parameters are adjusted in a stepwise manner to correct the abnormal resistance range. After each correction of the processing parameters, the number of deviation positions in the formed gear is obtained. If the number of deviation positions decreases, the processing parameters are adjusted again. Otherwise, gear processing is stopped.

[0011] Furthermore, obtaining the machining smoothness based on the gear profile includes the following steps: The profile of each gear tooth is divided into a left side, a right side, and a top side to obtain a standard profile. Multiple detection points are set on the standard profile, and the curvature of each detection point is obtained. The curvature fluctuation range of each side is determined based on the curvature. Curvature sequences corresponding to the left side, right side, and top side are generated based on the curvature of the detection points on the gear profile. A sliding window is set and its length is determined. A curvature feature sequence is extracted from each sequence based on the sliding window. If the value of an element in the curvature feature sequence exceeds the corresponding curvature fluctuation range, the position corresponding to that element is determined as a quality defect area, and the machining smoothness is also determined to be defective.

[0012] Furthermore, correcting the processing parameters based on processing smoothness includes the following steps: The coordinates of the quality defect area are used to determine the defect level, which includes low level and high level. Based on the machining smoothness of multiple formed gears, the probability of different defect levels of quality defect areas appearing at different positions is statistically analyzed. Quality defect areas with a probability of occurrence greater than a third threshold are defined as machining defect areas. If the number of low-level machining defect areas is greater than a fourth threshold, the clamping force of the fixture is adjusted. If the number of high-level machining defect areas is greater than the fourth threshold, the hob speed is adjusted.

[0013] The present invention also provides a small module gear CNC hobbing machine, which is used to implement the above-described method, and the hobbing machine includes: The processing module determines the processing parameters and processes the workpiece based on the processing parameters to obtain the formed gear; The scanning module selects multiple formed gears for three-dimensional scanning to obtain the corresponding gear model. A coordinate system is established with the center of the gear model as the origin. Multiple detection points are arranged parallel to the thickness direction of the gear model, and the coordinate values ​​of the detection points are determined. The analysis module detects the opposing surfaces of each tooth in the gear model to obtain the machining symmetry of each tooth; The detection points in the same layer are connected sequentially to obtain the multi-layer gear contour of the gear model in the thickness direction, and the machining smoothness is obtained based on the gear contour; The control module performs step corrections on the machining parameters based on machining smoothness and machining symmetry. The gear hobbing machine continues gear production based on the corrected machining parameters and calculates the changing trends of machining smoothness and machining symmetry. If machining smoothness and machining symmetry do not improve, gear production is stopped.

[0014] The beneficial effects of this invention are as follows: This invention first performs a three-dimensional scan of the processed gear to establish a gear model. Multiple detection points are arranged along the thickness direction in the gear model to capture the processing shape and features of each layer of the gear. Then, the processing smoothness and processing symmetry of each tooth's opposing side are detected, and the processing parameters are steppedly corrected based on the detection results, realizing feedback adjustment based on the actual gear morphology. The gear hobbing machine continues production based on the corrected processing parameters, and the processing effect is dynamically judged by the trend of processing quality changes, and production is determined accordingly, thereby ensuring the stability of production efficiency and product quality. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the gear model of the present invention; Figure 2 This is a flowchart illustrating the steps of a CNC gear hobbing machine control method for small-module gears according to the present invention. Figure 3 for Figure 1 A magnified schematic diagram of part A in the middle; Figure 4 This is a schematic diagram illustrating the principle of synthesizing representative contour lines. Figure 5 This is a system structure diagram of a small-module gear CNC hobbing machine according to the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] It is understood that the terms "first," "second," etc., used in this application may be used herein to describe various elements, but unless otherwise specified, these elements are not limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of this application, a first script may be referred to as a second script, and similarly, a second script may be referred to as a first script.

[0018] like Figure 2 As shown, a control method for a small-module gear CNC hobbing machine includes: S1: Determine the processing parameters, process the workpiece based on the processing parameters to obtain the shaped gear, select multiple shaped gears for 3D scanning to obtain the corresponding gear model.

[0019] S2: Establish a coordinate system with the center of the gear model as the origin, arrange multiple layers of detection points parallel to the thickness direction of the gear model, and determine the coordinate values ​​of the detection points.

[0020] In this embodiment, the machining parameters include cutting speed, feed rate, and depth of cut. These parameters are determined manually. After the machining parameters are determined, the gear hobbing machine processes the workpiece based on these parameters to obtain a shaped gear. The gear hobbing machine is equipped with a laser scanner. The laser scanner performs a high-precision multi-directional scan of the machined shaped gear to obtain point cloud data. A gear model is synthesized from the point cloud data. However, to ensure that the subsequently set detection points are on the same plane, the detection points are set after the gear model is generated, rather than directly using the point cloud as the detection points for analysis.

[0021] S3: Detect the opposite face of each tooth in the gear model to obtain the machining symmetry of each tooth.

[0022] S4: Based on the preset detection method, the gear model is detected to obtain the machining symmetry of the formed gear.

[0023] S5: Based on machining smoothness and machining symmetry, the machining parameters are corrected in a stepwise manner. The gear hobbing machine continues to produce gears based on the corrected machining parameters and calculates the changing trends of machining smoothness and machining symmetry.

[0024] S6: If the smoothness and symmetry of the machining process are not improved, then stop gear production.

[0025] Assuming the obtained gear model is as follows Figure 1 As shown, a spatial coordinate system is established with the center of the formed gear as the origin, and multiple points are selected as inspection points on the spatial coordinate system. To increase the simplicity of the diagram, only some inspection points are drawn. Assuming three layers of inspection points are set up, refer to... Figure 3 Three layers of detection points were arranged along the thickness direction, named layer R1, layer R2 and layer R3 respectively. Each layer includes multiple detection points, and the coordinates of each detection point are obtained.

[0026] exist Figure 3In the diagram, a gear tooth is divided into three sides: the front side Q, the left side Z, and the right side U. The right side U is not shown in the diagram due to obstruction. By connecting the detection points on the same side and the same layer, a side profile representing the shape of that side can be obtained. For gears, the shapes of the left and right sides should be the same or mirror symmetrical. By comparing the side profiles of the left and right sides, the machining symmetry of the gear hobbing machine can be determined. If there is a problem with the machining symmetry, the parameters of the gear hobbing machine should be adjusted. The specific method for judging machining symmetry will be introduced in detail later.

[0027] By connecting the detection points on different sides and in the same layer, the gear profile of the gear model in each layer can be obtained. By performing curvature analysis on the gear profile, the machining smoothness of the gear teeth can be obtained. Machining smoothness represents whether there are quality defects such as protrusions and depressions on the gear surface.

[0028] In this embodiment, a vibration sensor is installed inside the gear hobbing machine. At the same time, the wear state of the cutting tool is predicted based on existing technology. If the vibration sensor determines that abnormal vibration occurs during processing, the clamping force of the fixture is increased; otherwise, the cause is ruled out. If the cutting tool is predicted to be worn, the hob is replaced; otherwise, the cause is ruled out. If there is no abnormal vibration or cutting tool wear, the processing parameters are adjusted. The specific adjustment needs to be determined based on the judgment results of processing symmetry and processing flatness.

[0029] In this embodiment, detecting the opposing surfaces of each tooth in the gear model to obtain the machining symmetry of each tooth includes the following steps: Each tooth in the gear model is divided into a front side, a left side, and a right side. Detection points on the same side and in the same layer within the tooth are connected to obtain multiple side profile lines.

[0030] The side profiles of the teeth on the same side are superimposed to obtain the first line bundle. The first line bundle is then combined to form a representative profile. The representative profiles of the same teeth on opposite sides are superimposed to obtain the second line bundle. Offset analysis is performed on the second line bundle. If the representative profiles do not coincide, the sides corresponding to the two representative profiles are defined as defective sides. The spindle motor current during hobbing is obtained, and the change data of the motor current is converted into the change data of the hob resistance. The resistance change curve is plotted based on the resistance data. If the resistance change curve does not match the standard curve, it is determined that the machining symmetry of the formed gear does not meet the requirements.

[0031] Continue to refer to Figure 3As described above, the gear teeth are divided into a front side Q, a left side Z, and a right side U. To compare the symmetry of the left side Z and the right side U, firstly, the detection points on the same side and in the same layer are connected, for example, the detection points on the left side Z are connected to obtain side contour lines L1, L2, and L3. Then, these three side contour lines are superimposed to obtain a first line bundle. The three first line bundles are then combined into a representative contour line, defined here as representative contour line 1. The purpose is to eliminate the slight error that may exist between the surface of the gear and the actual surface during scanning and modeling. The specific merging method will be introduced in the next step. Similarly, the three contour lines on the right side U can be merged to obtain the corresponding representative contour line 2. In other embodiments, more layers of detection points can be set to generate more contour lines, thereby improving detection accuracy.

[0032] Next, representative contour line 1 and representative contour line 2 are superimposed to obtain the second wire bundle. The purpose of superposition is to determine whether representative contour line 1 and representative contour line 2 can coincide. If they can coincide, the machining symmetry requirement is met. During superposition, the machining shape of the gear needs to be determined, such as... Figure 3 The sides of the gear teeth are mirror-symmetrical, so when stacking, one side profile line should be reversed before stacking.

[0033] If representative contour line 1 and representative contour line 2 do not coincide, the left side Z and right side U are defined as defective sides. The spindle motor current during machining is acquired using a high-precision current sensor within the gear hobbing machine. The magnitude of the motor current is directly proportional to the resistance of the hob cutter; therefore, changes in hob resistance can be inferred from changes in motor current. During machining, the hob resistance generally remains constant, so the motor current should also remain constant. If a change in motor current is detected, it indicates a change in machining resistance, confirming a problem with machining symmetry. Furthermore, this embodiment also plots a resistance change curve based on the resistance change data. For machining scenarios where resistance changes are not constant, the actual resistance change curve is compared with a standard curve to obtain their similarity. If the similarity is low, a problem with machining symmetry is considered. If the resistance change curve has a high similarity to the standard curve, but representative contour line 1 and representative contour line 2 do not coincide, the gear model is considered inaccurate, and the detection result of that gear is not used as an adjustment reference. If multiple gear models show inaccuracies, a 3D scanner inspection is required.

[0034] Specifically, combining the first wire bundle into a representative contour line includes the following steps: Connect the two endpoints of each side profile line to obtain a reference line. Align each side profile line with the reference line as the target to obtain the first line bundle. Locate the longest reference line and define it as the reference line. Select multiple reference points on the reference line and map the reference points to each side profile line to obtain the acquisition points. Integrate the coordinate values ​​of the acquisition points corresponding to the same reference point into a coordinate set. Calculate the composite value in each coordinate direction based on the coordinate set. The composite value is the median or average of the coordinate values. Determine the coordinate point corresponding to the composite value in the coordinate system and define it as the composite point. Connect the composite points sequentially to obtain the representative profile line.

[0035] like Figure 4 As shown in Figure a, to synthesize the side profiles L1, L2, and L3 into a representative profile 1, firstly, the two endpoints of each side profile are connected to obtain a reference line. For example, connecting endpoints C1 and D1 yields a reference line for the corresponding side profile L1. Then, the side profiles are superimposed with the goal of coinciding with the reference line, thus obtaining... Figure 4 The result shown in b demonstrates that by superimposing the data with the control line as a reference, a good superimposition effect can be achieved even if the lengths of the side contour lines are different.

[0036] After overlaying, the longest reference line is selected as the reference line, and multiple reference points are selected at intervals on it, such as E1 and E2 in the figure. A perpendicular line is generated based on the reference points, perpendicular to the reference line. This perpendicular line will intersect at least one side profile line. For example, a perpendicular line drawn based on reference point E1 will intersect three side profile lines; the intersection point is defined as the acquisition point. The coordinate values ​​of the acquisition points are then synthesized. For example, three acquisition points corresponding to the same reference point E1 have x-coordinates of 3, 4, and 5. If the synthesized value is the average, then the synthesized value in the x-axis direction is (3+4+5) / 3=4. Similarly, synthesized values ​​in other axial directions are obtained. Based on the synthesized values ​​of the x, y, and z axes, a coordinate point can be determined. Repeating this process, multiple coordinate points, i.e., synthesized points, can be determined along the reference line. Connecting these synthesized points sequentially yields the representative profile line.

[0037] In this embodiment, the offset analysis of the second harness includes the following steps: The composite points of the two representative contour lines in the second bundle are matched, and the Euclidean distance between the corresponding composite points is calculated. Two composite points with an Euclidean distance greater than the first threshold are defined as deviation positions. If the deviation positions appear consecutively and the number is greater than the second threshold, it is determined that there is an offset in the representative contour line.

[0038] The reference lines for the left side Z and the right side U have the same spacing between their reference points. For example, each reference point is positioned at a 1 mm interval. If the left side Z is composited using reference line 1 and the right side U is composited using reference line 2, and both reference lines 1 and 2 start from the left endpoint and select a point as a reference point at a 1 mm interval, then after composited, the composite points on the representative contour line 1 and the representative contour line 2 can be matched one-to-one from left to right. Assuming representative contour line 1 includes 10 composite points, numbered 1-10, and representative contour line 2 includes 11 composite points, numbered 11-21, then representative contour lines 1 and 2 are superimposed. The Euclidean distance between composite points 1 and 11, and the Euclidean distance between composite points 2 and 12 are calculated. If the Euclidean distance between composite points 1 and 11 is greater than a first threshold, which is determined based on the processing precision, such as 2 mm, then the positions of composite points 1 and 11 in the representative contour lines are determined to be off-center positions. In addition, since composite point number 21 has no corresponding composite point, it is directly regarded as an off-center position.

[0039] During the processing, if a processing deviation occurs, and the spacing between the detection points is small, multiple deviation positions will appear consecutively. Therefore, if the deviation positions are consecutive on the representative contour line and the number is greater than the second threshold, such as 5, it is determined that the representative contour lines 1 and 2 are offset.

[0040] In this embodiment, the correction of processing parameters based on processing symmetry includes the following steps: The abnormal resistance range is located in the resistance change curve. The abnormal resistance range includes the range where the actual resistance value is greater than or lower than the standard resistance value. The processing parameters are adjusted stepwise to correct the abnormal resistance range. After each correction of the processing parameters, the number of deviations in the formed gear is obtained. If the number of deviations decreases, the processing parameters are adjusted again. Otherwise, the gear processing is stopped.

[0041] Abnormal resistance ranges include ranges where the actual resistance value is significantly greater than or lower than the standard resistance value. For example, a critical threshold can be set, and when the difference between the actual resistance value and the standard resistance value exceeds the critical threshold, it is determined that the actual resistance value is significantly greater than the standard resistance value.

[0042] If the actual resistance value is greater than the standard resistance value, it indicates that the cutting depth is too large. In this case, representative curves of the two defective sides are obtained. The superposition of these curves determines which side was cut deeper, i.e., which representative curve has a greater degree of curvature. Then, the specific machining parameters are adjusted based on the meshing process between the hob and the workpiece. For example, through meshing analysis, it is determined that the hob first contacts the left side for cutting, and then the right side. The deeper cut on the left side indicates that the hob's rotational speed is too high, resulting in a larger contact depth with the left side, requiring a reduction in rotational speed. In this embodiment, to achieve automated adjustment of the gear hobbing machine, adjustment values ​​are set. When the system determines through the above analysis that the hob rotational speed needs adjustment, it reduces the hob rotational speed in steps, decreasing the preset adjustment value each time. After each reduction, the adjustment effect is determined by scanning the machining symmetry of the gear. If the overlap of the representative curves increases after adjustment, the parameter adjustment continues; otherwise, a reminder command is issued to the operator, instructing them to adjust the machining parameters manually.

[0043] In this embodiment, obtaining machining smoothness based on gear contour includes the following steps: The profile of each gear tooth is divided into a left side, a right side, and a top side to obtain a standard profile. Multiple detection points are set on the standard profile, and the curvature of each detection point is obtained. The curvature fluctuation range of each side is determined based on the curvature. Based on the curvature of the detection points on the gear profile, curvature sequences corresponding to the left side, the right side, and the top side are generated respectively. A sliding window is set and the window length is determined. Based on the sliding window, a curvature feature sequence is extracted from each sequence. If the value of an element in the curvature feature sequence exceeds the corresponding curvature fluctuation range, the position corresponding to that element is determined as a quality defect area, and the machining smoothness is also determined to be defective.

[0044] Machining smoothness represents the smoothness of the gear surface. The above analysis of machining symmetry can determine whether the two sides are symmetrical and identical, but it cannot be used to detect surface smoothness. If a small bulge appears on one side profile and a depression appears on the other, it may be eliminated during the synthesis of the representative curve, or the two sides may have defects in the same position due to tool wear, making it impossible to determine the surface smoothness by comparison. Therefore, this embodiment also proposes the following method to determine the smoothness of the side.

[0045] For the gear profile, it is also divided into multiple teeth, and it is a two-dimensional image. Therefore, the profile of each tooth is divided into the left side, the right side and the top side. Since three layers of detection points are set along the thickness direction of the gear, three gear profiles will be obtained, and the processing smoothness of each of the three gear profiles will be judged.

[0046] Before making a judgment, the standard profile of the gear teeth is first obtained. Multiple detection points are then set on this profile, and the curvature of each detection point is obtained. The maximum and minimum curvatures of the detection points on the left side are also obtained. The portion between the maximum and minimum curvatures is taken as the curvature fluctuation range of the left side. For example, if the maximum curvature is 0.13 and the minimum curvature is 0.11, the curvature fluctuation range is [0.11, 0.13]. In other embodiments, if the gear tooth profile has a large curvature variation, each side can be divided into multiple smaller intervals, and the curvature fluctuation range of each interval can be statistically analyzed, thereby further improving the accuracy of the judgment result.

[0047] This embodiment sets up detection points on the gear model for analysis. To improve detection accuracy, the detection points need to be densely distributed. However, the factory environment is relatively harsh. If there are residual large dust particles on the gear, abnormal protrusions may appear in the scanned gear model. Protrusions or depressions generated during gear processing can cause abnormal curvature at multiple consecutive detection points. Therefore, to eliminate the influence of abnormal protrusions or depressions on curvature, after obtaining the curvature sequence representing the side, a curvature feature sequence is extracted using a sliding window. For example, if the sliding window is set to 3, when the curvature sequence is [0.12 0.18 0.14], 0.18 represents an abnormal protrusion caused by dust, exceeding the curvature fluctuation range. By averaging, 0.147 is obtained, thus eliminating this value and improving the detection accuracy. Finally, the detection points corresponding to elements in the curvature feature sequence that exceed the curvature fluctuation range are defined as quality defect points.

[0048] In this embodiment, the correction of processing parameters based on processing smoothness includes the following steps: The coordinates of the quality defect area are used to determine the defect level, which includes low level and high level. Based on the machining smoothness of multiple formed gears, the probability of different defect levels of quality defect areas appearing at different locations is statistically analyzed. Quality defect areas with a probability of occurrence greater than the third threshold are defined as machining defect areas. If the number of low-level machining defect areas is greater than the fourth threshold, the clamping force of the fixture is adjusted. If the number of high-level machining defect areas is greater than the fourth threshold, the hob speed is adjusted.

[0049] To avoid accidental occurrences, this embodiment determines whether to adjust the processing parameters based on the detection results of multiple gear models. For example, 10 gear models are continuously acquired for inspection, and after the quality defect area is acquired, it is divided into low-grade and high-grade. Low-grade represents slight unevenness on the gear surface, while high-grade represents larger defects on the gear surface. For example, it is determined based on the value of the curvature of the detection point exceeding the standard curvature range. When the value exceeding the standard curvature range is small, it is defined as a low-grade defect point, and when the value exceeding the standard curvature range is large, it is defined as a high-grade defect point. The specific threshold for classifying low-grade and high-grade can be determined through experience or production requirements.

[0050] The probability of occurrence at each location is then calculated. For example, in 10 gear models, if a quality defect area appears 8 times near location 1, and all of them are low-level defects, then the probability of a low-level quality defect appearing at location 1 is 8 / 10 * 100% = 80%. With the third threshold set to 50%, location 1 is considered a quality defect area because its probability is greater than 50%. If analysis reveals a large number of low-level quality defect areas, it indicates that insufficient clamping force may have caused slight vibrations, resulting in numerous minor unevennesses on the gear surface. Therefore, the system attempts to increase the clamping force to correct this. If the number of high-level machining defect areas exceeds the fourth threshold, the system attempts to adjust the hob speed, as an improper hob speed may lead to uneven cutting force.

[0051] like Figure 5 As shown, the present invention also provides a small module gear CNC hobbing machine, which is used to implement the above-mentioned method. The hobbing machine includes: The machining module determines the machining parameters and processes the workpiece based on these parameters to obtain the shaped gear.

[0052] The scanning module selects multiple formed gears for 3D scanning to obtain the corresponding gear models. A coordinate system is established with the center of the gear model as the origin. Multiple detection points are arranged parallel to the thickness direction of the gear model, and the coordinate values ​​of the detection points are determined.

[0053] The analysis module detects the opposing surfaces of each tooth in the gear model to obtain the machining symmetry of each tooth. It then connects the detection points in the same layer to obtain the multi-layer gear profile in the thickness direction of the gear model and obtains the machining smoothness based on the gear profile.

[0054] The control module performs step corrections on the machining parameters based on machining smoothness and machining symmetry. The gear hobbing machine continues gear production based on the corrected machining parameters and calculates the changing trends of machining smoothness and machining symmetry. If machining smoothness and machining symmetry do not improve, gear production is stopped.

[0055] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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.

[0056] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

[0057] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for a small-module gear CNC hobbing machine, characterized in that, include: Determine the processing parameters, process the workpiece based on the processing parameters to obtain the formed gear, select multiple formed gears for three-dimensional scanning to obtain the corresponding gear model; A coordinate system is established with the center of the gear model as the origin. Multiple detection points are arranged parallel to the thickness direction of the gear model, and the coordinate values ​​of the detection points are determined. The opposing surfaces of each tooth in the gear model are inspected to obtain the machining symmetry of each tooth; The detection points in the same layer are connected sequentially to obtain the multi-layer gear contour of the gear model in the thickness direction, and the machining smoothness is obtained based on the gear contour; The machining parameters are corrected stepwise based on machining smoothness and machining symmetry. The gear hobbing machine continues to produce gears based on the corrected machining parameters and calculates the changing trends of machining smoothness and machining symmetry. If the smoothness and symmetry of the machining process are not improved, then gear production should be stopped. The steps to detect the opposing surfaces of each tooth in the gear model and obtain the machining symmetry of each tooth include the following: Each tooth in the gear model is divided into a front side, a left side, and a right side. The detection points on the same side and in the same layer of the tooth are connected to obtain multiple side contour lines. The side profiles of the teeth on the same side are superimposed to obtain a first line bundle. The first line bundle is then combined to form a representative profile. The representative profiles of the teeth on opposite sides are superimposed to obtain a second line bundle. An offset analysis is performed on the second line bundle. If the representative profiles do not coincide, the sides corresponding to the two representative profiles are defined as defective sides. The spindle motor current during hobbing is obtained, and the change data of the motor current is converted into the change data of the hob resistance. A resistance change curve is plotted based on the resistance data. If the resistance change curve does not match the standard curve, it is determined that the machining symmetry of the formed gear does not meet the requirements.

2. The method according to claim 1, characterized in that, Combining the first wire bundle into a representative contour line includes the following steps: A reference line is obtained by connecting the two endpoints of each side profile line. The side profile lines are aligned with the reference line as the target to obtain the first line bundle. The longest reference line is located and defined as the reference line. Multiple reference points are selected on the reference line and mapped to each side profile line to obtain the acquisition points. The coordinate values ​​of the acquisition points corresponding to the same reference point are integrated into a coordinate set. A composite value is calculated in each coordinate direction based on the coordinate set. The composite value is the median or average of the coordinate values. The coordinate point corresponding to the composite value is determined in the coordinate system and defined as the composite point. The composite points are connected sequentially to obtain the representative profile line.

3. The method according to claim 2, characterized in that, The offset analysis of the second harness includes the following steps: The composite points in the two representative contour lines in the second line bundle are matched, and the Euclidean distance between the corresponding composite points is calculated. Two composite points with an Euclidean distance greater than a first threshold are defined as deviation positions. If the deviation positions appear consecutively and the number is greater than a second threshold, it is determined that the representative contour line has an offset.

4. The method according to claim 3, characterized in that, Correcting the machining parameters based on machining symmetry includes the following steps: The abnormal resistance range is located in the resistance change curve. The abnormal resistance range includes the range where the actual resistance value is greater than or lower than the standard resistance value. The processing parameters are adjusted in a stepwise manner to correct the abnormal resistance range. After each correction of the processing parameters, the number of deviation positions in the formed gear is obtained. If the number of deviation positions decreases, the processing parameters are adjusted again. Otherwise, gear processing is stopped.

5. The method according to claim 1, characterized in that, Obtaining machining smoothness based on the gear profile includes the following steps: The profile of each gear tooth is divided into a left side, a right side, and a top side to obtain a standard profile. Multiple detection points are set on the standard profile, and the curvature of each detection point is obtained. The curvature fluctuation range of each side is determined based on the curvature. Curvature sequences corresponding to the left side, right side, and top side are generated based on the curvature of the detection points on the gear profile. A sliding window is set and its length is determined. A curvature feature sequence is extracted from each sequence based on the sliding window. If the value of an element in the curvature feature sequence exceeds the corresponding curvature fluctuation range, the position corresponding to that element is determined as a quality defect area, and the machining smoothness is also determined to be defective.

6. The method according to claim 5, characterized in that, Correcting the machining parameters based on machining smoothness includes the following steps: The defect level of the quality defect area is determined based on the curvature of the detection points within the quality defect area. The defect level includes low level and high level. The probability of occurrence of quality defect areas of different defect levels at different positions is statistically analyzed based on the machining smoothness of multiple formed gears. Quality defect areas with a probability of occurrence greater than a third threshold are defined as machining defect areas. If the number of low-level machining defect areas is greater than a fourth threshold, the clamping force of the fixture is adjusted. If the number of high-level machining defect areas is greater than the fourth threshold, the hob speed is adjusted.

7. A small-module gear CNC hobbing machine, used to implement the method as described in any one of claims 1-6, characterized in that, The gear hobbing machine includes: The processing module determines the processing parameters and processes the workpiece based on the processing parameters to obtain the formed gear; The scanning module selects multiple formed gears for three-dimensional scanning to obtain the corresponding gear model. A coordinate system is established with the center of the gear model as the origin. Multiple detection points are arranged parallel to the thickness direction of the gear model, and the coordinate values ​​of the detection points are determined. The analysis module detects the opposing surfaces of each tooth in the gear model to obtain the machining symmetry of each tooth. It then connects the detection points within the same layer to obtain a multi-layered gear profile in the thickness direction, and obtains the machining smoothness based on this profile. The control module performs step-wise corrections on the machining parameters based on the machining smoothness and symmetry. The gear hobbing machine continues gear production based on the corrected machining parameters and calculates the changing trends of machining smoothness and symmetry. If the machining smoothness and symmetry do not improve, gear production is stopped.

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