A precision testing device and method for AC double-swivel heads

Abstract

This invention belongs to the field of machine tools, specifically relating to a precision testing device and method for an AC double-swivel head. The technical solution of this invention is as follows: A precision testing device for an AC double-swivel head includes a support and a testing platform. The upper part of the support is provided with a swivel head fixing component, and the bottom of the support is provided with multiple adjustable feet. A platform support frame is provided in the middle of the support, and the platform support frame has four locking corners. The testing platform is placed on the platform support frame with its four corners engaging with the four locking corners. Four adjustable bolts are provided between the bottom four corners of the testing platform and the platform support frame. The precision testing device and method for an AC double-swivel head provided by this invention can quickly measure the geometric accuracy and rotational positioning accuracy of the AC swivel head, without occupying the main machine, shortening the finished product delivery time, and without introducing linear axis motion errors, thus improving inspection efficiency and accuracy.

Description

Technical Field

[0001] This invention belongs to the field of machine tools, specifically relating to an AC double-swivel head precision detection device and method. Background Technology

[0002] With the continuous advancement of technology and the increasing sophistication of industrial demands, five-axis CNC machine tools are finding wider applications in aerospace, automotive mold making, and precision machinery. These machine tools are highly favored for their ability to efficiently and precisely machine complex curved surfaces and irregularly shaped workpieces. The AC swivel head device, as a key component of a five-axis CNC machine tool, directly affects the overall machine's working accuracy and stability. Traditionally, spatial error detection of the AC double swivel head axis system requires the use of a gantry frame mainframe, referring to the standard GB / T 33150-2016 "Accuracy Inspection of Five-Axis CNC Overhead Beam Moving Gantry Milling Machines." While this method can detect the spatial geometric errors of each axis of the AC double swivel head, it relies on linear axis motion, which introduces linear axis motion errors. Due to the accumulation of these errors, it cannot accurately reflect the spatial relative positional relationship of each axis.

[0003] Testing is performed using a testing platform and dial indicator pusher, as disclosed in CN115682867B, which describes a five-axis head testing mechanism and method, including a testing frame, a fixing plate, a testing platform, and a test bar. The testing platform simulates a machine tool's worktable, and the dial indicator is moved via Z-axis, X-axis, and Y-axis drive mechanisms, eliminating the need for manual pushing of the dial indicator and avoiding testing errors caused by manual adjustment. Although the head of this device is completely fixed, the linear motion of the dial indicator is still required, accumulating linear guideway errors.

[0004] In summary, the existing technology lacks a dedicated device and method for directly, efficiently, and accurately measuring the relative positional deviations (such as center intersection deviation and axis perpendicularity deviation) between the A-axis center, C-axis center, and main spindle axis inside the AC double swing head. Summary of the Invention

[0005] This invention provides a precision testing device and method for AC double oscillating heads, which can quickly measure the geometric accuracy and rotational positioning accuracy of AC oscillating heads, without occupying the main unit, shortening the finished product delivery time, and without introducing linear axis motion errors, thereby improving inspection efficiency and accuracy.

[0006] The technical solution of the present invention is as follows: An AC double-swivel head precision testing device includes a bracket and a testing platform. The upper part of the bracket is provided with a swivel head fixing component, and the bottom of the bracket is provided with multiple adjustable feet. The middle part of the bracket is provided with a platform support frame, and the platform support frame is provided with four corner clips. The testing platform is placed on the platform support frame and its four corners fit into the four corner clips. Four adjustable bolts are provided between the bottom four corners of the testing platform and the platform support frame.

[0007] Furthermore, the accuracy detection device for the AC double-swivel head has a detection platform made of natural marble.

[0008] Furthermore, in the aforementioned AC double-swivel head precision detection device, the swivel head fixing assembly includes a fixing plate and a transition sleeve. The fixing plate is fixedly connected to the upper part of the bracket, and the transition sleeve is installed on the lower side of the fixing plate. The transition sleeve is used to install the AC double-swivel head.

[0009] Furthermore, the AC double-swivel head precision detection device includes a transition sleeve available in various specifications to accommodate different specifications of AC double-swivel heads.

[0010] Furthermore, in the aforementioned AC double-swivel head precision detection device, the adjustable feet include a foot plate, a vertical rod, a hollow threaded sleeve, a locking nut, and a fixing nut. The lower end of the vertical rod is fixedly connected to the foot plate, and the upper part of the vertical rod is provided with external threads. The bottom plate of the bracket is provided with a screw hole, and the hollow threaded sleeve is screwed into the screw hole and screwed together with the bottom plate. The locking nut is installed on the hollow threaded sleeve and positions the hollow threaded sleeve and the bottom plate. The vertical rod is inserted into the hollow threaded sleeve, and the fixing nut is installed on the upper end of the vertical rod to fix the foot plate, the vertical rod, and the hollow threaded sleeve together.

[0011] Furthermore, in the aforementioned AC double-swivel head precision testing device, the bracket has multiple vertical holes on its inner side, which are used to install support fixtures.

[0012] Furthermore, in the aforementioned AC double-swivel head precision detection device, a protective fence is installed above the bracket and a hanging ladder is installed at the rear.

[0013] A method for detecting the accuracy of an AC double-swivel head, utilizing the aforementioned accuracy detection device for an AC double-swivel head, includes the following steps: 1) Install the AC double oscillating head onto the transition sleeve of the oscillating head fixing assembly and secure it; 2) Insert the test bar into the AC double swing head, attach the dial indicator base to the test bar, and let the dial indicator probe touch the surface of the testing platform; rotate the C-axis of the AC double swing head, adjust the adjustable feet to roughly adjust the level of the bracket, and further adjust the adjustable bolts to make the surface of the testing platform perpendicular to the C-axis. 3) Select an appropriate hole position to install the dial indicator support fixture, fix the dial indicator on the support fixture, and make sure the dial indicator probe touches the test bar side busbar; rotate each axis of the AC double swing head in sequence, observe the dial indicator needle jump, and record the value at the specified position; or zero it at the specified position and calculate the error.

[0014] Furthermore, the specific process in step 2) of the AC double pendulum head accuracy detection method is as follows: drive the C-axis of the AC double pendulum head to rotate, perform coarse adjustment by adjusting the hollow screw sleeve of the adjustable foot, and then finely adjust the adjustable bolt so that the micrometer value changes ≤0.005mm when the C-axis rotates one revolution. Precisely adjust the table surface of the detection platform to be perpendicular to the C-axis rotation axis, and use this as the spatial reference plane for subsequent multiple measurements.

[0015] Furthermore, the specific process in step 3) of the aforementioned AC double-swivel head accuracy detection method is as follows: S1. Determination of A-axis 0 position, and parallelism check of principal axis and C-axis: Drive the AC double-swivel head A-axis to near 0° and clamp it; fix the dial indicator on the test bar, making the dial indicator probe parallel to the C-axis direction and touching the test platform surface, with a rotation radius R=300mm; drive the spindle to rotate one revolution at 45° intervals, and read the dial indicator value at 8 positions: 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°; by fine-tuning the A-axis angle, make the difference between the readings at the 180° position and the 0° position ≤0.003mm, and define the position of the A-axis as the mechanical 0 position; at the same time, evaluate the parallelism between the spindle axis and the C-axis axis, and the maximum difference at the 8 positions reflects the parallelism error; S2. Measurement of inter-axis intersection: S2.1 Measurement of the intersection of the A-axis and C-axis: Fix the dial indicator on the support fixture, drive the C-axis to 0°, the A-axis to +90°, and the spindle to 0°. The dial indicator probe should perpendicularly touch the end face of the probe or the end face of the spindle. Record the reading as MW1. Then, drive the C-axis to 180°, the A-axis to -90°, and the spindle to 180°. Record the reading as MW2. The center deviation MW_AC between the A-axis and the C-axis in the measurement direction is calculated using the following formula: MW_AC = |MW1 - MW2| / 2. S2.2 Measurement of the intersection between the A-axis and the main spindle: Drive the A-axis to +90°, touch the dial indicator probe to the side generatrix of the test bar, and measure the 450mm overhang. Rotate the C-axis to find the highest point, mark C0, and fix the C-axis. Drive the spindle to 0° and read the dial indicator value NW1. Rotate the C-axis 180°, the A-axis to -90°, the spindle to 180°, and the C-axis to find the highest point. Read the dial indicator value NW2. The center deviation MW_AS between the A-axis and the spindle in the measurement direction is calculated using the following formula: MW_AS = |NW1 - NW2| / 2; S3. Measurement of perpendicularity between A-axis and C-axis: High-precision measurement was performed using a three-dial method. Three dial indicators were placed 450mm above the side generatrix of the test bar along the A-axis. First, at the 0° position of the C-axis, the A-axis was driven to +90°, 0°, and -90° respectively, and the highest point of the A-axis was found. The three dial indicators at the corresponding positions were then zeroed. Next, the C-axis was rotated 180°, and the A-axis was driven to -90°, 0°, and +90° again. The average value of the readings of the three dial indicators at the highest point of the corresponding positions was recorded as LW1, LW2, and LW3. LW1 and LW3 were compared to obtain LWmax. The perpendicularity measurement error between the A-axis and the C-axis, WF_AC, was calculated using the following formula: WF_AC=[(LWmax-LW2) / 2] / 450mm; S4. Measurement of perpendicularity between A-axis and spindle axis: Drive the AC double oscillating head to the initial position: C-axis 0°, A-axis +90°, spindle 0°; fix two dial indicators to the side generatrix of the test bar using a support fixture, with one dial indicator probe positioned 450mm from the spindle end face and the other probe positioned 550mm; rotate the A-axis to find the highest point reached by the probes of both dial indicators, then zero the two dial indicators at this position; drive the AC double oscillating head to the mirror position: C-axis 180°, A-axis -90°, spindle 180°; rotate the A-axis again to find the highest point reached by the probes of both dial indicators and read the stable readings; record the readings as KW1 and KW2; calculate the perpendicularity WF_AS between the A-axis and the spindle using the following formula: WF_AS=[(KW2-KW1) / 2] / 100mm.

[0016] The beneficial effects of this invention are as follows: 1. This invention fundamentally eliminates the interference of linear axis motion errors, achieving accurate determination of the pure geometric relationship between axes. Traditional methods, whether using a mainframe gantry or a testing platform with linear guides, inevitably incorporate positioning errors of the linear axes themselves (X, Y, Z), backlash, and guide straightness errors into the measurement results. This results in the final data being a coupling of AC double-swivel head errors and linear axis errors, failing to truly and purely reflect the intrinsic spatial relative positional relationship between the A-axis, C-axis, and the main spindle axis.

[0017] 2. The detection process of this invention is greatly simplified and efficiency is significantly improved. Existing technologies, such as the dial indicator method, are cumbersome to operate, rely on human experience, and have poor repeatability. Even automatic dial indicator devices are time-consuming due to their complex multi-axis linkage and positioning. The structure of this invention is easy to install, the detection steps are easy to operate, and the data processing algorithm is simple. This allows the measurement process to completely eliminate the need for any external or additional linear axis movement. The measurement benchmark is directly established on the AC double-swivel head body under test or a stationary reference system rigidly connected to it, thereby eliminating the most important interference source in the error transmission chain and improving the measurement accuracy of core geometric deviations such as axis intersection and perpendicularity. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of an AC double-swivel head precision detection device; Figure 2 This is a schematic diagram of the head-swing fixing component; Figure 3 This is a schematic diagram of adjustable feet; Figure 4 This is a schematic diagram of the support frame and testing platform; Figure 5 A schematic diagram for establishing a baseline and checking the parallelism between the spindle and the C-axis; Figure 6 A schematic diagram showing the measurement of the intersection of the A-axis and C-axis. Figure 7 This is a schematic diagram showing the measurement of the intersection between the A-axis and the main spindle axis. Figure 8 This is a schematic diagram showing the measurement of the perpendicularity between axis A and axis C. Figure 9 This is a schematic diagram for measuring the perpendicularity of axis A to the main spindle axis. Detailed Implementation

[0019] like Figure 1-4 As shown, an AC double-swivel head precision testing device includes a bracket 1 and a testing platform 2. The bracket 1 has a swivel head fixing component 3 on its upper part and multiple adjustable feet 4 on its bottom. The bracket 1 has a platform support frame 21 in the middle, with four corner brackets 22 on the platform support frame 21. The testing platform 2 is placed on the platform support frame 21 with its four corners fitting into the four corner brackets 22. Four adjustable bolts 23 are provided between the bottom four corners of the testing platform 2 and the platform support frame 21. The testing platform 2 is made of natural marble. The bracket 1 has multiple vertical holes on its inner side for installing a gauge support fixture 6. A protective fence 8 is installed above the bracket 1, and a hanging ladder 9 is installed at the rear.

[0020] The head-swing fixing assembly 3 includes a fixing plate 31 and a transition sleeve 32. The fixing plate 31 is fixedly connected to the upper part of the bracket 1, and the transition sleeve 32 is installed on the lower side of the fixing plate 31. The transition sleeve 32 is used to install the AC double-swing head 5. The transition sleeve 32 is available in various specifications to accommodate different specifications of AC double-swing heads 5.

[0021] The adjustable foot 4 includes a foot plate 41, a vertical rod 42, a hollow threaded sleeve 43, a locking nut 44, and a fixing nut 45. The lower end of the vertical rod 42 is fixedly connected to the foot plate 41, and the upper part of the vertical rod 42 is provided with external threads. The bottom plate 11 of the bracket 1 is provided with a screw hole. The hollow threaded sleeve 43 is screwed into the screw hole and screwed together with the bottom plate 11. The locking nut 44 is installed on the hollow threaded sleeve 43 and positions the hollow threaded sleeve 43 and the bottom plate 11. The vertical rod 42 is inserted into the hollow threaded sleeve 43, and the fixing nut 45 is installed on the upper end of the vertical rod 42 to fix the foot plate 41, the vertical rod 42, and the hollow threaded sleeve 43 together.

[0022] A method for detecting the accuracy of an AC double-swivel head, utilizing the aforementioned accuracy detection device for an AC double-swivel head, includes the following steps: 1) Install the AC double swing head 5 onto the transition sleeve 32 of the swing head fixing assembly 3 and fix it in place; 2) Insert the probe 7 into the AC double-swivel head 5, attach the dial indicator base to the probe 7, and let the dial indicator probe touch the table surface of the testing platform 2; rotate the C-axis of the AC double-swivel head 5, adjust the adjustable foot 4 to coarsely adjust the level of the bracket 1, and further adjust the adjustable bolt 23 to make the table surface of the testing platform 2 perpendicular to the C-axis; the specific process is as follows: drive the C-axis of the AC double-swivel head 5 to rotate, make coarse adjustment by adjusting the hollow screw sleeve 43 of the adjustable foot 4, and then finely adjust the adjustable bolt 23 so that the change in the dial indicator value is ≤0.005mm when the C-axis rotates one revolution, and precisely adjust the table surface of the testing platform 2 to be perpendicular to the C-axis rotation axis, which serves as the spatial reference plane for subsequent multiple measurements; 3) Select an appropriate hole position to install the dial indicator support fixture 6, fix the dial indicator on the support fixture 6, and ensure the dial indicator probe touches the side generatrix of the test bar 7; rotate each axis of the AC double swing head 5 in sequence, observe the dial indicator needle movement, and record the value at the specified position; or zero the dial indicator at the specified position and calculate the error; the specific process is as follows: S1. Determination of A-axis 0 position, and parallelism check of principal axis and C-axis: like Figure 5As shown, drive the A-axis of the AC double-swivel head 5 to near 0° and clamp it; fix the dial indicator on the test bar 7, so that the dial indicator probe is parallel to the C-axis direction and touches the table surface of the testing platform 2, with a rotation radius R=300mm; drive the spindle to rotate one revolution at 45° intervals, and read the dial indicator value at 8 positions: 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°; by fine-tuning the A-axis angle, make the difference between the readings at the 180° position and the 0° position ≤0.003mm, and define the position of the A-axis as the mechanical 0 position; at the same time, evaluate the parallelism between the spindle axis and the C-axis axis, and the maximum difference at the 8 positions reflects the parallelism error; S2. Measurement of inter-axis intersection: S2.1 Measurement of the intersection of the A-axis and C-axis: like Figure 6 As shown, fix the dial indicator on the support fixture 6, drive the C-axis to 0°, the A-axis to +90°, and the spindle to 0°, so that the dial indicator probe touches the end face of the test bar 7 or the end face of the spindle perpendicularly, and record the reading as MW1; then, drive the C-axis to 180°, the A-axis to -90°, and the spindle to 180°, and record the reading as MW2; the center deviation MW_AC between the A-axis and the C-axis in the measurement direction is calculated by the following formula: MW_AC=|MW1-MW2| / 2; S2.2 Measurement of the intersection between the A-axis and the main spindle: like Figure 7 As shown, drive the A-axis to +90°, touch the dial indicator probe to the side of the probe 7, and measure the 450mm overhang. Rotate the C-axis to find the highest point, mark C0, and fix the C-axis. Drive the spindle to 0° and read the dial indicator value NW1. Rotate the C-axis 180°, the A-axis to -90°, and the spindle to 180°. Rotate the C-axis to find the highest point and read the dial indicator value NW2. The center deviation MW_AS between the A-axis and the spindle in the measurement direction is calculated using the following formula: MW_AS = |NW1 - NW2| / 2; S3. Measurement of perpendicularity between A-axis and C-axis: like Figure 8 As shown, a three-dial indicator method is used for high-precision measurement. Three dial indicators are placed 450mm above the side generatrix of the test bar 7 along the A-axis. First, at the 0° position of the C-axis, the A-axis is driven to +90°, 0°, and -90° respectively. The highest point of the A-axis is found by rotating it, and the three dial indicators at the corresponding positions are zeroed. Then, the C-axis is rotated 180°, and the A-axis is driven to -90°, 0°, and +90° again. The average value of the readings of the three dial indicators at the highest points of the corresponding positions is recorded as LW1, LW2, and LW3. Comparing LW1 and LW3 yields LWmax. The perpendicularity measurement error WF_AC between the A-axis and C-axis is calculated using the following formula: WF_AC=[(LWmax-LW2) / 2] / 450mm; S4. Measurement of perpendicularity between A-axis and spindle axis: like Figure 9 As shown, drive the AC double swing head to the initial position: C-axis 0°, A-axis +90°, main shaft 0°; fix two dial indicators to the side generatrix of the test bar 7 using the support fixture 6, with the probe of one dial indicator located 450mm from the end face of the main shaft and the probe of the other dial indicator located 550mm; rotate the A-axis to find the highest point reached by the probes of the two dial indicators, and then zero the two dial indicators at this position; drive the AC double swing head 5 to the mirror position: C-axis 180°, A-axis -90°, main shaft 180°; rotate the A-axis again to find the highest point reached by the probes of the two dial indicators, and read the stable readings; record the readings as KW1 and KW2; calculate the perpendicularity WF_AS between the A-axis and the main shaft using the following formula: WF_AS=[(KW2-KW1) / 2] / 100mm.

[0023] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A precision detection device for an AC double-swivel head, characterized in that, The device includes a support frame and a testing platform. The upper part of the support frame is equipped with a head-swing fixing component, and the bottom of the support frame is equipped with multiple adjustable feet. The middle part of the support frame is equipped with a platform support frame, which has four corner clips. The testing platform is placed on the platform support frame and its four corners fit into the four corner clips. There are four adjustable bolts between the bottom four corners of the testing platform and the platform support frame.

2. The accuracy detection device for the AC double-swivel head according to claim 1, characterized in that, The testing platform is made of natural marble.

3. The accuracy detection device for the AC double-swivel head according to claim 1, characterized in that, The head-swing fixing assembly includes a fixing plate and a transition sleeve. The fixing plate is fixedly connected to the upper part of the bracket, and the transition sleeve is installed on the lower side of the fixing plate. The transition sleeve is used to install the AC double head.

4. The accuracy detection device for the AC double-swivel head according to claim 3, characterized in that, The transition sleeve is available in various sizes to accommodate different sizes of AC double-swivel heads.

5. The accuracy detection device for the AC double-swivel head according to claim 1, characterized in that, The adjustable feet include a base plate, a vertical rod, a hollow threaded sleeve, a locking nut, and a fixing nut. The lower end of the vertical rod is fixedly connected to the base plate, and the upper part of the vertical rod is provided with external threads. The bottom plate of the bracket has a screw hole, and the hollow threaded sleeve is screwed into the screw hole and screwed together with the bottom plate. The locking nut is installed on the hollow threaded sleeve and positions the hollow threaded sleeve and the bottom plate. The vertical rod is inserted into the hollow threaded sleeve, and the fixing nut is installed on the upper end of the vertical rod to fix the base plate, the vertical rod, and the hollow threaded sleeve together.

6. The accuracy detection device for AC double-swivel heads according to claim 1, characterized in that, The bracket has multiple vertical holes on its inner side, which are used to install meter support fixtures.

7. The accuracy detection device for the AC double-swivel head according to claim 1, characterized in that, A protective fence is installed above the support structure, and a ladder is installed at the rear.

8. A method for detecting the accuracy of an AC double-swivel head, characterized in that, The accuracy detection device for the AC double-swivel head as described in any one of claims 1-7 includes the following steps: 1) Install the AC double oscillating head onto the transition sleeve of the oscillating head fixing assembly and secure it; 2) Insert the test bar into the AC double swing head, attach the dial indicator base to the test bar, and let the dial indicator probe touch the surface of the testing platform; rotate the C-axis of the AC double swing head, adjust the adjustable feet to roughly adjust the level of the bracket, and further adjust the adjustable bolts to make the surface of the testing platform perpendicular to the C-axis. 3) Select an appropriate hole position to install the dial indicator support fixture, fix the dial indicator on the support fixture, and make sure the dial indicator probe touches the test bar side busbar; rotate each axis of the AC double swing head in sequence, observe the dial indicator needle jump, and record the value at the specified position; or zero it at the specified position and calculate the error.

9. The accuracy detection method for the AC double-swivel head according to claim 8, characterized in that, The specific process in step 2) is as follows: drive the C-axis of the AC double swing head to rotate, make a coarse adjustment by adjusting the hollow screw sleeve of the adjustable foot, and then finely adjust the adjustable bolt so that the micrometer value changes ≤0.005mm when the C-axis rotates one revolution. Precisely adjust the table surface of the detection platform to be perpendicular to the rotation axis of the C-axis, and use this as the spatial reference plane for subsequent multiple measurements.

10. The accuracy detection method for the AC double-swivel head according to claim 8, characterized in that, The specific process in step 3) is as follows: S1. Determination of A-axis 0 position, and parallelism check of principal axis and C-axis: Drive the AC double-swivel head A-axis to near 0° and clamp it; fix the dial indicator on the test bar, making the dial indicator probe parallel to the C-axis direction and touching the test platform surface, with a rotation radius R=300mm; drive the spindle to rotate one revolution at 45° intervals, and read the dial indicator value at 8 positions: 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°; by fine-tuning the A-axis angle, make the difference between the readings at the 180° position and the 0° position ≤0.003mm, and define the position of the A-axis as the mechanical 0 position; at the same time, evaluate the parallelism between the spindle axis and the C-axis axis, and the maximum difference at the 8 positions reflects the parallelism error; S2. Measurement of inter-axis intersection: S2.1 Measurement of the intersection of the A-axis and the C-axis: Fix the dial indicator on the support fixture, drive the C-axis to 0°, the A-axis to +90°, and the spindle to 0°. The dial indicator probe should perpendicularly touch the end face of the probe or the end face of the spindle. Record the reading as MW1. Then, drive the C-axis to 180°, the A-axis to -90°, and the spindle to 180°. Record the reading as MW2. The center deviation MW_AC between the A-axis and the C-axis in the measurement direction is calculated using the following formula: MW_AC = |MW1 - MW2| / 2. S2.2 Measurement of the intersection between the A-axis and the main spindle: Drive the A-axis to +90°, touch the dial indicator probe to the side generatrix of the test bar, and measure the 450mm overhang. Rotate the C-axis to find the highest point, mark C0, and fix the C-axis. Drive the spindle to 0° and read the dial indicator value NW1. Rotate the C-axis 180°, the A-axis to -90°, the spindle to 180°, and the C-axis to find the highest point. Read the dial indicator value NW2. The center deviation MW_AS between the A-axis and the spindle in the measurement direction is calculated using the following formula: MW_AS = |NW1 - NW2| / 2; S3. Measurement of perpendicularity between A-axis and C-axis: High-precision measurement was performed using a three-dial method. Three dial indicators were placed 450mm above the side generatrix of the test bar along the A-axis. First, at the 0° position of the C-axis, the A-axis was driven to +90°, 0°, and -90° respectively, and the highest point of the A-axis was found. The three dial indicators at the corresponding positions were then zeroed. Next, the C-axis was rotated 180°, and the A-axis was driven to -90°, 0°, and +90° again. The average value of the readings of the three dial indicators at the highest point of the corresponding positions was recorded as LW1, LW2, and LW3. LW1 and LW3 were compared to obtain LWmax. The perpendicularity measurement error between the A-axis and the C-axis, WF_AC, was calculated using the following formula: WF_AC=[(LWmax-LW2) / 2] / 450mm; S4. Measurement of perpendicularity between A-axis and spindle axis: Drive the AC double oscillating head to the initial position: C-axis 0°, A-axis +90°, spindle 0°; fix two dial indicators to the side generatrix of the test bar using a support fixture, with one dial indicator probe positioned 450mm from the spindle end face and the other probe positioned 550mm; rotate the A-axis to find the highest point reached by the probes of both dial indicators, then zero the two dial indicators at this position; drive the AC double oscillating head to the mirror position: C-axis 180°, A-axis -90°, spindle 180°; rotate the A-axis again to find the highest point reached by the probes of both dial indicators and read the stable readings; record the readings as KW1 and KW2; calculate the perpendicularity WF_AS between the A-axis and the spindle using the following formula: WF_AS=[(KW2-KW1) / 2] / 100mm.

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