A method for machining a chamfer of a precision hole orifice arranged obliquely

Abstract

The application provides a kind of oblique precision hole orifice chamfer self-adaptive compensation processing method, which utilizes the measuring device installed on the numerical control machine tool to complete the automatic measurement of oblique precision hole position, automatically calculates the deviation value between the oblique precision hole position in the current state and the theoretical state according to the measurement result, and performs self-adaptive compensation on the deviation value to eliminate the feature size precision deviation caused by multi-station clamping, tool measurement, machine tool machining precision and other factors, and realize the automatic and accurate machining of chamfer position; solve the problem of time-consuming and laborious processing test under the traditional solidification compensation value mode due to unsuitable compensation value, eliminate the multi-station clamping positioning and machine tool machining precision error, better ensure the precision hole orifice chamfer structure size requirement, effectively avoid product quality problems, and also improve the machining efficiency of the part.

Description

Technical Field

[0001] This invention belongs to the field of CNC machining technology, and particularly relates to an adaptive compensation machining method for chamfering of oblique precision holes. Background Technology

[0002] As aircraft structural performance requirements increase, component designs are becoming increasingly larger, more complex, and more integrated. Aircraft structural components, as major load-bearing parts, are increasingly integrated with surrounding components, with lug structures featuring high-precision mounting holes appearing extensively on overall aircraft structural parts. During CNC machining, the chamfering of both ends of high-precision mounting holes typically requires the collaborative processing of two finishing stations: the first station completes the precision hole and one side chamfering, while the second station completes the other side chamfering. However, due to factors such as the precision of the cutting tools and machine tools themselves, and clamping and positioning errors, the chamfering of precision holes processed by the two stations must be stopped during machining to measure the chamfer dimensions and compensate for any deviations before further processing to ensure the chamfer dimensions are within acceptable limits. When the theoretical axis of the precision hole is parallel to the Z-axis of the machining coordinate system, the method of measuring the chamfer dimensions using specialized measuring tools and then manually calculating the compensation value is simple and mature. However, due to factors such as machining schemes and raw material size limitations, the theoretical axis of the precision hole cannot remain parallel to the Z-axis of the machining coordinate system, resulting in a theoretical angle and causing the precision hole to be skewed. The slanted precision hole structure makes it difficult for operators to measure, and the deviation cannot be accurately calculated and compensated for manually, ultimately leading to a lack of quality assurance in the processed products. Manual adjustment and intervention in machine tool processing not only consumes a significant amount of time but also carries substantial quality risks.

[0003] To address the aforementioned issues, traditional solutions involve improving tool measurement accuracy and clamping accuracy at each workstation. High-precision machine tools are prioritized, and multiple actual machining tests are conducted. Dimensional data from each machining process is recorded and compared with theoretical values ​​to calculate compensation values. The median compensation value is then directly incorporated into the CNC process parameters. However, this method has limitations. First, the solidified process parameters cannot adapt to complex and changing actual machining environments, and parts can only be machined on test-tested machine tools. When production capacity is insufficient and temporary adjustments to the machining equipment are necessary, the machining tests must be repeated. Second, due to the limited number of tests, the solidified parameters may not be applicable to every machining process, and the measurement accuracy is also limited by the structure of the chamfered opening of the inclined precision hole. Finally, long-term use of equipment and tooling inevitably leads to wear and tear, causing a gradual decrease in clamping and machining accuracy. This necessitates continuous adjustment of compensation values ​​to adapt to the actual machining conditions of the parts. Summary of the Invention

[0004] To address product quality issues caused by multi-station clamping and positioning, machine tool machining accuracy, and manual calculation errors, as well as the cumbersome, time-consuming, and labor-intensive process of re-processing and testing due to insufficient production capacity and temporary adjustments to processing equipment under traditional fixed compensation value methods; the limited number of processing tests and the fact that fixed parameters may not be suitable for every processing cycle; and the need for continuous optimization of compensation values ​​due to decreased machining accuracy after equipment and tooling wear, this invention provides an adaptive compensation machining method for chamfering the opening of inclined precision holes. The technical solution is as follows: An adaptive compensation machining method for chamfering of the opening of a slanted precision hole includes: The measuring device installed on the CNC machine tool is used to automatically measure the position of the inclined precision hole. Based on the measurement results, the deviation between the current position of the inclined precision hole and the theoretical position is automatically calculated, and the deviation is adaptively compensated to eliminate the deviation of the feature dimension accuracy caused by multi-station clamping, tool measurement, machine tool machining accuracy, etc., so as to realize the automated and precise machining of the chamfered part.

[0005] Optionally, the method specifically includes: Step 1: Take the upper surface of the inclined precision hole as the reference surface, the upper chamfer surface of the inclined precision hole as the first feature surface, and the lower chamfer surface of the inclined precision hole as the second feature surface. Step 2: Complete the absolute size conversion of the chamfer, that is, distribute the chamfer tolerance to the three directions of X, Y, and Z to obtain the tolerance components in the three directions; Step 3: Perform finishing on the first feature surface and the reference surface; Step 4: Measure the actual hole center position of the first feature surface to be finished by the measuring device installed on the CNC machine tool. Compare the deviations of the actual hole center from the theoretical hole center in the X, Y, and Z directions with the magnitudes of the chamfer tolerance in the X, Y, and Z directions to determine whether the finishing of the first feature surface is qualified. If it is qualified, proceed to step 5. Step 5: Perform semi-finishing on the second feature surface; Step 6: Measure the actual hole center position of the semi-finished second feature surface using the measuring device installed on the CNC machine tool. Compare the deviations of the actual hole center from the theoretical hole center in the X, Y, and Z directions with the magnitudes of the chamfer tolerance in the X, Y, and Z directions to determine whether the semi-finishing of the second feature surface is qualified. If qualified, proceed to step 7. Step 7: Subtract the theoretical hole center position from the actual hole center position of the semi-finished second feature surface to obtain the hole center deviation of the semi-finished second feature surface. Compensate the hole center deviation to the machining coordinate system of the second feature surface. The hole position deviation compensation is completed by offsetting the coordinate system. Step 8: Perform finishing on the second feature surface in the offset coordinate system. Optionally, in step 2, a qualified chamfer satisfies the requirement that the difference between the actual center point and the theoretical center point of the chamfer in the X, Y, and Z directions is less than or equal to the components of the chamfer tolerance in the X, Y, and Z directions, respectively. Given the coordinates (Xθ, Yθ, Zθ) of the theoretical hole center of the first feature surface and the coordinates (X0, Y0, Z0) of the actual hole center of the first feature surface, the tolerance zone ±ΔL of the chamfer length L is compressed by multiplying it by a coefficient K, where K < 1, to offset measurement errors. The compressed tolerance zone is then assigned to the current machining coordinate system, i.e., Xθ, Yθ, Zθ, X0, Y0, Z0 satisfy: |X0 - Xθ| ≤ cosθ [(K] ΔL) 2 / 2] 1 / 2 |Y0-Yθ|≤cosθ [(K] ΔL) 2 / 2] 1 / 2 |Z0-Zθ|≤sinθ [(K] ΔL) 2 / 2] 1 / 2 .

[0006] Optionally, in step 4, the coordinates of the contact point between the measuring device's measuring end and the precision hole being measured are determined by first connecting the measuring device's measuring end to the piezoelectric switch via a hinge when the measuring device's measuring end contacts the precision hole being measured, and generating a pulse signal. This signal is emitted through a signal transmitter and received by a signal receiver connected to the machine tool, controlling the machine tool to stop and extracting the coordinates of the point, thus ending the measurement of that point.

[0007] Optionally, in step 4, firstly, a first reference point is selected on the theoretical axis of the precision hole, and the coordinates of the first reference point are used as the coordinates of the theoretical hole center on the first feature surface; then, four feature points are selected on the first feature surface, the plane formed by the four feature points is perpendicular to the theoretical axis of the precision hole, and the first reference point is located in this plane; during measurement, firstly, the measuring device is tilted at an angle θ to ensure that its axis is parallel to the theoretical axis of the precision hole, and the corresponding actual hole center is obtained by measuring these four feature points respectively. Then, the differences in X, Y, and Z coordinate values ​​between the actual hole center and the theoretical hole center are calculated respectively: ΔX, ΔY, and ΔZ; finally, it is determined whether the absolute value of the deviation meets the allocated tolerance requirements, that is, whether |ΔX|≤cosθ. [(K] ΔL) 2 / 2] 1 / 2 |ΔY|≤cosθ [(K] ΔL) 2 / 2] 1 / 2 |ΔZ|≤sinθ [(K] ΔL)2 / 2] 1 / 2 If the conditions are not met, the automatic processing flow will end.

[0008] Optionally, in step 6, firstly, a second reference point is selected on the theoretical axis of the precision hole, and the coordinates of the second reference point are used as the coordinates of the theoretical hole center on the second feature surface. Then, four feature points are selected on the second feature surface, and the plane formed by the four feature points is perpendicular to the theoretical axis of the precision hole, with the second reference point located within this plane. During measurement, the measuring device is first tilted at an angle θ to ensure that its axis is parallel to the theoretical axis of the precision hole. The corresponding actual hole center is obtained by measuring these four feature points respectively. Then, the differences in X, Y, and Z coordinate values ​​between the actual hole center and the theoretical hole center are calculated as ΔX, ΔY, and ΔZ. Finally, it is determined whether the absolute value of the deviation meets the allocated tolerance requirements, i.e., whether |ΔX|≤cosθ is satisfied. [(K] ΔL) 2 / 2] 1 / 2 |ΔY|≤cosθ [(K] ΔL) 2 / 2] 1 / 2 |ΔZ|≤sinθ [(K] ΔL) 2 / 2] 1 / 2 .

[0009] Optionally, in step 7, the X-axis deviation, Y-axis deviation, and Z-axis deviation calculated in step 6 are compensated to the machining coordinate system of the second feature surface to correct the machining coordinate system.

[0010] Optionally, in step 8, the semi-finishing and finishing of the second feature surface are both performed by the same tool to eliminate errors caused by different tools.

[0011] The beneficial effects of this invention are at least as follows: By utilizing an online measurement system, a measuring device installed on a CNC machine tool is used to directly measure the actual hole position of a slanted precision hole and perform real-time error compensation machining. This solves the problem of time-consuming and labor-intensive machining tests due to unsuitable compensation values ​​in the traditional fixed compensation value method. It also eliminates multi-station clamping and positioning and machine tool machining accuracy errors, better ensures the chamfer structure size requirements of the precision hole opening, effectively avoids product quality problems, and improves the machining efficiency and flexibility of the machining process. Attached Figure Description

[0012] Figure 1 This is a schematic diagram showing the conversion of the chamfer size of the oblique precision hole opening; Figure 2This is a schematic diagram of the automatic measurement of the relative deviation between the actual hole center and the theoretical hole center on the first characteristic surface; Figure 3 This is a schematic diagram of adaptive compensation machining for the relative deviation between the actual hole center and the theoretical hole center on the second feature surface; Figure 4 This is a schematic diagram showing the positional relationship between the actual hole center and the theoretical hole center on the second characteristic surface; Figure 5 This is a schematic diagram showing the relative deviation between the actual hole center and the theoretical hole center on the second characteristic surface; Figure 6 This is a schematic diagram of the measuring device structure; Figure 7 This is a schematic diagram of the measuring device in operation; Wherein: 1-First feature surface, 2-Second feature surface, 3-Theoretical axis of precision hole, 4-Machining coordinate system of first feature surface, 5-Reference surface, 6-First reference point, 7-Actual hole center corresponding to the first feature point, 8-First feature point 1, 9-First feature point 2, 10-First feature point 3, 11-First feature point 4, 12-Machining coordinate system of second feature surface, 13-Actual hole center corresponding to the second feature point, 14-Second reference point, 15-Second feature point 1, 16-Second feature point 2, 17-Second feature point 3, 18-Second feature point 4, 19-Actual semi-finished second feature surface, 20-Theoretical semi-finished second feature surface, 21-Compensated finishing coordinate system of second feature surface, 22-Signal transmitter of measuring device, 23-Power supply of measuring device, 24-Hinge of measuring device, 25-Contact piezoelectric switch of measuring device. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0015] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited from each other.

[0016] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0017] The present invention will be further illustrated using the compensation machining process for the chamfering of a certain oblique precision hole as an example. The CNC system used is a Sinumerik 840D, but it is applicable to other CNC systems; the measuring device inside the machine tool is a wireless probe.

[0018] Step 1: Perform absolute size transformation on the first feature surface 1, such as... Figure 1 As shown.

[0019] 1) First, by measuring the three-dimensional digital model of the part, the angle θ = 3° between the theoretical axis 3 of the precision hole and the Z-axis of the current machining coordinate system can be obtained, and the chamfer size is 1.2 ± 0.1 × 45°. Second, a first reference point 6 is selected on the theoretical axis 3 of the precision hole, and the coordinates of the first reference point 6 (X86.039, Y0, Z-45.012) are used as the coordinates of the center of the theoretical hole of the first feature surface. A second reference point 9 is selected on the theoretical axis 3 of the precision hole, and the coordinates of the second reference point 9 (X85.962, Y0, Z48.036) are used as the coordinates of the center of the theoretical hole of the second feature surface. 2) The positions of the precision holes in the parts that were previously test-cut were measured and recorded. The results are shown in the table below: Table 1 Measurement Record Results

[0020] Based on the above measurement data, it can be seen that the maximum error between the in-machine measurement and the measurement of the hole position coordinates is 0.006, which does not exceed 0.01. Therefore, 0.01 can be allocated to compensate for the measurement error. Thus, when compressing the tolerance zone ±ΔL of the chamfer length L, the parameter K can be set to 0.9, that is, the tolerance zone is modified to ±0.9×ΔL, i.e., ±0.9×0.1=±0.09; 3) The compressed tolerance is allocated to the first feature surface machining coordinate system 4. Through calculation, it can be obtained that... The tolerance assigned in the X direction = cosθ [(0.9×ΔL)] 2 / 2] 1 / 2 = cos3° (0.09 2 / 2) 1 / 2 ≈0.06, The tolerance of the Y-axis allocation = cosθ [(0.9×ΔL)] 2 / 2] 1 / 2 = cos3° (0.09 2 / 2) 1 / 2 ≈0.06, The tolerance for Z-direction allocation = sinθ [(0.9×ΔL)] 2 / 2] 1 / 2 = sin3° (0.09 2 / 2) 1 / 2 ≈0.003, Then calculate the X-coordinate deviation |ΔX|, Y-coordinate deviation |ΔY|, and Z-coordinate deviation |ΔZ| between the actual hole center and the theoretical hole center. Determine whether the absolute values ​​of the deviations meet the allocated tolerance requirements, i.e., whether |ΔX|≤0.06, |ΔY|≤0.06, and |ΔZ|≤0.003. If not, the subsequent processing flow can be terminated.

[0021] The second step is to compile the machining program for the first station, which includes the fine machining process for the first feature surface 1 and the datum surface 5.

[0022] The third step is to develop the measurement program for the first workstation, such as... Figure 2 As shown, the program includes the automatic measurement of the coordinates of the actual hole center 7 corresponding to the four first feature points of the first feature surface 1, specifically as follows: First, four feature points are selected, the plane formed by the four feature points is perpendicular to the theoretical axis of the precision hole, and the first reference point 6 is located in this plane. Second, in the first feature surface machining coordinate system 4, a measuring device installed on the machine tool (see...) is used... Figure 6 and Figure 7By measuring the actual coordinates of the four feature points, the coordinates of the actual hole center 7 corresponding to the four feature points, i.e., the actual finishing hole center of the first feature surface 1, can be obtained (X86.064, Y-0.034, Z-45.014). Then, the coordinates of the actual finishing hole center of the first feature surface 1 (X86.064, Y-0.034, Z-45.014) and the coordinates of the theoretical hole center of the first feature surface 1 (X86.039, Y0, Z-45.012) are calculated respectively. The differences in the X, Y, and Z directions are: ΔX = 86.064 - 86.039 = 0.025, ΔY = -0.034 - 0 = -0.034, ΔZ = -45.014 - (-45.012) = -0.002. It is determined that the deviation values ​​in the X, Y, and Z directions (0.025 and 0.034) are both less than the tolerance allocated in that direction (0.06), and the deviation value in the Z direction (0.002) is less than the tolerance allocated in that direction (0.003). Therefore, the actual finishing of the first feature surface meets the design requirements.

[0023] Step 4: Compile the semi-finishing program for the second station, such as... Figure 3 As shown, the program includes a semi-finishing allowance of L1 = 0.2mm for the second feature surface. The program can theoretically form a semi-finished second feature surface 20. However, due to the double-sided clamping and machining of the part, after flipping it over, it is straightened and aligned again and the coordinate system is set. Affected by various factors such as tool setting and clamping, the actual semi-finished second feature surface 19 is formed after the program is executed.

[0024] Step 5: Compile the semi-precision measurement program for the second station, such as... Figure 3As shown, the program includes measuring the coordinates of the actual hole center 11 corresponding to the four second feature points of the second feature surface 2, specifically as follows: First, four second feature points are selected, the plane formed by the four feature points is perpendicular to the theoretical axis of the precision hole, and the second reference point 14 is located in this plane; secondly, the actual coordinates of the four second feature points are measured respectively using a measuring device installed on the machine tool under the machining coordinate system 12 of the second feature surface, so as to obtain the coordinates of the actual hole center 13 corresponding to the four second feature points, that is, the coordinates of the actual semi-finished hole center of the second feature surface 2 (X85.911, Y0.048, Z48.033); then, the coordinates of the actual semi-finished hole center of the second feature surface 2 (X85.911, Y0.048, Z48.033) are calculated respectively. The X, Y, and Z direction differences between the coordinates (X85.962, Y0, Z48.033) and the theoretical hole center coordinates (X85.962, Y0, Z48.036) of the second feature surface are: ΔX = 85.911 - 85.962 = -0.051, ΔY = 0.048 - 0 = 0.048, ΔZ = 48.033 - 48.036 = -0.003. After judgment, the X-direction deviation value of 0.051 and the Y-direction deviation value of 0.048 are both less than the tolerance of 0.06 allocated in this direction, and the Z-direction deviation value of 0.003 does not exceed the tolerance of 0.003 allocated in this direction. Therefore, the actual semi-finishing of the second feature surface 2 does not exceed the design requirements, and the finishing of the second feature surface 2 can continue after coordinate system compensation.

[0025] Step 6: Develop an error calculation and compensation program, such as... Figure 3 As shown, the X-axis deviation, Y-axis deviation, and Z-axis deviation calculated in the previous step are compensated into the second feature surface machining coordinate system 12 to correct the machining coordinate system. That is, the origin coordinates (X0, Y0, Z0) of the finishing second feature surface machining coordinate system 8 are modified to (X-0.051, Y0.048, Z-0.003). Figure 4 This is a schematic diagram showing the positional relationship between the actual hole center and the theoretical hole center on the second characteristic surface. Figure 5 This is a schematic diagram showing the relative deviation between the actual hole center and the theoretical hole center on the second characteristic surface.

[0026] Step 7: Compile the finishing program for the second station. Under the compensated finishing coordinate system 21 for the second feature surface, complete the finishing of the second feature surface 2 through the program. In order to eliminate the error introduced by different tools, it should be ensured that the semi-finishing and finishing of the second feature surface are completed by the same tool.

[0027] Finally, during the chamfering process of the oblique precision hole opening, the first station machining program and the first station measurement program are executed sequentially. After the tolerance requirements are met, the hole is flipped over, and the second station semi-finishing program, the second station semi-finishing measurement program, the error calculation and compensation program, and the second station finishing program are executed sequentially to complete the adaptive compensation machining of the oblique precision hole opening.

[0028] The above description merely illustrates embodiments of the present invention and is quite specific and detailed; however, it should not be construed as limiting the scope of the patent. 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 scope of protection of the present invention. Furthermore, any parts of the present invention not described in detail are conventional techniques.

Claims

1. A method for adaptive compensation machining of chamfered openings of oblique precision holes, characterized in that, include: The measuring device installed on the CNC machine tool is used to automatically measure the position of the inclined precision hole. Based on the measurement results, the deviation between the current position of the inclined precision hole and the theoretical position is automatically calculated, and adaptive compensation is performed on the deviation. The method specifically includes: Step 1: Take the upper surface of the inclined precision hole as the reference surface, the upper chamfer surface of the inclined precision hole as the first feature surface, and the lower chamfer surface of the inclined precision hole as the second feature surface. Step 2: Complete the absolute size conversion of the chamfer, that is, distribute the chamfer tolerance to the three directions of X, Y, and Z to obtain the tolerance components in the three directions; Step 3: Perform finishing on the first feature surface and the reference surface; Step 4: Measure the actual hole center position of the first feature surface to be finished by the measuring device installed on the CNC machine tool. Compare the deviations of the actual hole center from the theoretical hole center in the X, Y, and Z directions with the magnitudes of the chamfer tolerance in the X, Y, and Z directions to determine whether the finishing of the first feature surface is qualified. If it is qualified, proceed to step 5. Step 5: Perform semi-finishing on the second feature surface; Step 6: Measure the actual hole center position of the semi-finished second feature surface using the measuring device installed on the CNC machine tool. Compare the deviations of the actual hole center from the theoretical hole center in the X, Y, and Z directions with the magnitudes of the chamfer tolerance in the X, Y, and Z directions to determine whether the semi-finishing of the second feature surface is qualified. If qualified, proceed to step 7. Step 7: Compensate the X-axis deviation, Y-axis deviation, and Z-axis deviation calculated in Step 6 to the machining coordinate system of the second feature surface to correct the machining coordinate system. By offsetting the coordinate system, the hole position deviation compensation is completed. Step 8: Perform finishing machining on the second feature surface in the second feature surface machining coordinate system.

2. The method according to claim 1, characterized in that, In step 2, a properly machined chamfer satisfies the requirement that the differences in the X, Y, and Z coordinates between the actual and theoretical center points of the chamfer are less than or equal to the components of the chamfer tolerance in the X, Y, and Z directions, respectively. Given the coordinates (Xθ, Yθ, Zθ) of the theoretical hole center on the first feature surface and the coordinates (X0, Y0, Z0) of the actual hole center on the first feature surface, the tolerance zone ±ΔL of the chamfer length L is compressed by multiplying it by a coefficient K, where K < 1, to compensate for measurement errors. The compressed tolerance zone is then assigned to the current machining coordinate system, i.e., Xθ, Yθ, Zθ, X0, Y0, Z0 satisfy: |X0 - Xθ| ≤ cosθ[(KΔL] 2 / 2] 1 / 2 |Y0-Yθ|≤cosθ[(KΔL) 2 / 2] 1 / 2 |Z0-Zθ|≤sinθ[(KΔL) 2 / 2] 1 / 2 .

3. The method according to claim 1, characterized in that, In step 4, the coordinates of the contact point between the measuring device's measuring end and the precision hole being measured are determined by first connecting the measuring device's measuring end to the piezoelectric switch via a hinge when the measuring device's measuring end contacts the precision hole being measured, and generating a pulse signal. This signal is emitted through a signal transmitter and received by a signal receiver connected to the machine tool, controlling the machine tool to stop and extracting the coordinates of the point, thus ending the measurement of that point.

4. The method according to claim 1, characterized in that, In step 4, firstly, a first reference point is selected on the theoretical axis of the precision hole, and the coordinates of the first reference point are used as the coordinates of the theoretical hole center on the first feature surface. Then, four feature points are selected on the first feature surface, and the plane formed by the four feature points is perpendicular to the theoretical axis of the precision hole, with the first reference point located within this plane. During measurement, the measuring device is first tilted at an angle θ to ensure that its axis is parallel to the theoretical axis of the precision hole. The actual hole center is obtained by measuring these four feature points respectively. Then, the differences in the X, Y, and Z coordinate values ​​between the actual hole center and the theoretical hole center are calculated as ΔX, ΔY, and ΔZ respectively. Finally, it is determined whether the absolute value of the deviation meets the allocated tolerance requirements, i.e., whether |ΔX|≤cosθ[(KΔL]). 2 / 2] 1 / 2 |ΔY|≤cosθ[(KΔL) 2 / 2] 1 / 2 |ΔZ|≤sinθ[(KΔL)] 2 / 2] 1 / 2 If the conditions are not met, the automatic processing flow will end.

5. The method according to claim 1, characterized in that, In step 6, firstly, a second reference point is selected on the theoretical axis of the precision hole. The coordinates of the second reference point are used as the coordinates of the theoretical hole center on the second feature surface. Then, four feature points are selected on the second feature surface. The plane formed by the four feature points is perpendicular to the theoretical axis of the precision hole, and the second reference point is located in this plane. During measurement, the measuring device is first tilted at an angle θ to ensure that its axis is parallel to the theoretical axis of the precision hole. The actual hole center is obtained by measuring the four feature points respectively. Then, the differences in the X, Y, and Z coordinate values ​​between the actual hole center and the theoretical hole center are calculated as ΔX, ΔY, and ΔZ. Finally, it is determined whether the absolute value of the deviation meets the allocated tolerance requirements, that is, whether |ΔX|≤cosθ[(KΔL]). 2 / 2] 1 / 2 |ΔY|≤cosθ[(KΔL) 2 / 2] 1 / 2 |ΔZ|≤sinθ[(KΔL)] 2 / 2] 1 / 2 .

6. The method according to claim 1, characterized in that, In step 8, the semi-finishing and finishing of the second feature surface are both performed by the same cutting tool.

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