A precise assembly process method of a rotary table hydraulic motor

Abstract

The application discloses a precision assembly process method of a rotary table hydraulic motor and relates to the technical field of precision assembly processes.The precision assembly process method comprises the following steps: ensuring that the positioning hole of the hydraulic motor assembly is coaxial with the assembly: determining an assembly transition reference hole; assembling a left bearing seat and a stator; correcting the coaxial relationship between the stator hole and the central hole of the left bearing seat; checking the coaxial relationship between the left bearing positioning hole and the stator hole by using a dial gauge; driving the positioning pin into the hinge pin hole one and the hinge pin hole two; checking the coaxial relationship between the left bearing positioning hole and the stator hole by using a dial gauge; assembling a right bearing seat and the stator; correcting the right bearing seat; ensuring that the axial size of the main shaft dynamic blade is assembled in the center: determining an assembly measurement reference surface; determining a support height; adjusting a single-side gap; assembling; first verification; determining the left bearing cover assembly quantity; measuring the assembly reference size; turning over; second verification; determining the right bearing cover assembly quantity; rechecking; self-checking; and adding sealing rings and sealing strips.The precision machining difficulty is reduced, and the performance index and realizability of the hydraulic motor are improved.

Description

Technical Field

[0001] This invention relates to the field of precision assembly technology, and in particular to a precision assembly process method for a turntable hydraulic motor. Background Technology

[0002] The assembly of the rotary table hydraulic motor assembly should meet the shaft rotation accuracy requirements. Simultaneously, appropriate clearances are necessary to prevent leakage or increased frictional torque. Ensuring coaxial assembly of the component positioning holes and axial alignment of the main shaft moving blades are two key processes in hydraulic motor assembly, presenting the following technical challenges: (1) Coaxial assembly of component positioning holes: Only by assembling component positioning holes coaxially can the rotational accuracy and radial clearance of the shaft system be guaranteed. If positioning bosses are added to the left and right bearing seats and corresponding positioning grooves are added to the two sides of the stator, the coaxiality of the component positioning holes will rely entirely on the machining accuracy of the parts. The actual machining accuracy of the positioning structure fit clearance is difficult to meet the positioning requirements. If the left and right bearing seats are assembled with the stator separately and then the inner holes are precision ground, a relief groove needs to be added at the connection between the stator inner hole and the bearing seat, which increases the risk of leakage and also has the possibility of coaxial error caused by turning the machining.

[0003] (2) Axial dimension alignment of the main shaft moving blades: Axial dimension alignment of the main shaft moving blades is necessary to ensure the rotational accuracy of the shaft system and appropriate axial clearance. The axial dimensions of the main shaft, left and right bearing housings, and stator inevitably have accumulated machining errors. At the same time, in order to ensure the rotational accuracy of the shaft system, a reasonable bearing preload should be used. Therefore, the determination of the fitting amount of the left and right bearing covers must eliminate the accumulated machining errors on the premise of ensuring a reasonable bearing preload and ensuring the alignment of the axial dimensions of the main shaft moving blades. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a precision assembly process method for a rotary table hydraulic motor, comprising the following steps: S1. Ensure the hydraulic motor assembly positioning holes are aligned coaxially, including the following steps: S11. Grind the center hole of the left bearing housing, the positioning hole of the left bearing, the center hole of the right bearing housing, and the positioning hole of the bearing to make the center hole of the left bearing housing and the positioning hole of the left bearing coaxial, and the center hole of the right bearing housing and the positioning hole of the right bearing as the assembly transition reference hole. S12. Use bolt 1 to assemble the left bearing housing and the stator together; S13. Use the vertical coordinate boring machine, with the stator positioned by the equal height block pad. First, correct the center of the stator hole, then check that the coaxiality between the stator hole and the center hole of the left bearing seat is <0.01mm, and tighten the bolt. S14. Flip the left bearing housing and stator assembly over, using the left bearing housing for positioning, and use a dial indicator to verify that the left bearing positioning hole and the stator hole are coaxial. S15. Flip the left bearing housing and stator assembly over again, drill reaming pin hole one and reaming pin hole two, and drive in the positioning pin to ensure the repeatability of the coaxiality of the positioning hole assembly after multiple disassembly and assembly. S16. Place the left bearing housing and stator assembly on the single-axis turntable. Use a dial indicator to recheck that the left bearing positioning hole and stator hole are coaxial. After adjustment, disassemble the installed parts. Through the rechecks in S14 and S16, avoid the impact of the cumulative error of parallelism machining of the positioning surfaces at both ends of the assembly and the operational errors in the process of correction, tightening screws and drilling and reaming pin holes on the coaxiality of the assembly positioning hole assembly. S17. Using another bolt, assemble the right bearing housing with the stator. Referring to the calibration operation of the left bearing housing in steps S12 to S16, calibrate the right bearing housing. After the adjustment is qualified, disassemble the assembled parts.

[0005] S2. Ensure the axial dimensions of the main shaft moving blades are aligned during assembly, including the following steps: S21. Determine the assembly measurement reference surface: Fine grind the left end face of the spindle and the left end face of the left bearing housing so that the left end face of the spindle and the left end face of the left bearing housing are perpendicular to the reference axis, and use them as the assembly measurement reference surface. S22. Determine the support height: Position the main shaft on the marble platform with the right end face as the positioning point. Measure the height of the left end step face of the main shaft moving blade. Select and use equal height blocks and jacks to support the stator according to this height. S23. Adjust the clearance on one side: Adjust the jack according to the axial clearance value between the left end step face of the main shaft moving blade and the left end face of the stator, so that the left end face of the stator is higher than the left end step face of the main shaft moving blade, and level the left end face of the stator. S24. Assembly: Install the left bearing housing on the stator, drive in the locating pin and fasten the two parts with bolt one, install bearing one into the main shaft, install the unmatched left bearing cover on the left bearing housing, connect with screws and tighten. S25. First verification: With the dial indicator below the left bearing housing, spindle and stator assembly, measure the axial clearance between the right end face of the step on the moving blade and the right end face of the stator. Verify the clearance adjusted in step S23 to avoid the impact of measurement and adjustment operation errors and machining errors of the axial dimensions of the spindle and stator parts on the assembly alignment of the axial dimensions of the moving blade of spindle 1. S26. Determine the fit quantity of the left bearing cover: Remove the left bearing cover and re-measure the axial clearance between the right end face of the moving blade step and the right end face of the stator to verify, so as to avoid the change of the axial clearance between the moving blade step and the stator end face under the two different states of bearing clamping and free; after confirming that there is no change, measure the step difference between the left end face of the left bearing housing and the left end face of bearing one, and add the bearing one preload to determine the fit quantity of the left bearing cover. The fit quantity of the left bearing cover meets the requirements. When measuring, the measurement is performed with bearing one without preload, which eliminates the cumulative machining error and avoids the influence of bearing preload on the measurement of bearing cover fitting dimensions. S27. Measure the assembly reference dimension: Measure the distance between the left end face of the spindle and the left end face of the left bearing seat, and record it as the assembly measurement reference dimension; S28. Flipping: Install the left bearing cover after the vehicle is assembled and tighten the screws. Flip the left bearing housing, main shaft and stator. Position the main shaft with the left end face and place it on the marble platform. Add leveling blocks and jacks for support under the left bearing housing. S29. Second verification: Measure the axial clearance between the right end face of the stator and the right end step face of the moving blade of the main shaft to verify the clearance after the flipping operation, so as to avoid the loosening of the fit between the main shaft step face and the bearing during the flipping process, which would cause the axial clearance between the moving blade step face and the stator end face to change. S210. Determine the right bearing cover fitting quantity: Install the right bearing housing on the stator and connect it with bolt two. Install bearing two into the spindle. Measure the step difference between the right end face of the right bearing housing and the right end face of the bearing, and add the bearing two preload. Determine the right bearing cover fitting quantity. Fit the right bearing cover to meet the requirements. When measuring, measure with bearing two without preload. This eliminates the cumulative machining error and avoids the influence of bearing preload on the bearing cover fitting dimension measurement. S211, Re-inspection: Install the right bearing cover after assembly and tighten the mounting screws of the left and right bearing covers. Measure the distance between the left end face of the main shaft and the left end face of the left bearing seat and compare it with the measurement value recorded in step S. Re-inspect whether the axial dimension alignment of the moving blade is qualified. By comparing the assembly measurement reference dimensions before and after bearing preload, it is determined that the bearing preload is reasonable and the axial dimension alignment of the moving blade is qualified. S212. Self-inspection: The rotational accuracy of the shaft system is qualified. S213. Install sealing rings and sealing strips: Disassemble the installed parts and install sealing rings and sealing strips. Reassemble according to the above steps and re-check whether the axial dimensions of the moving blades are aligned.

[0006] Furthermore, the center hole of the left bearing housing and the positioning hole of the left bearing are ground out in one go, and the coaxiality is ≤0.005mm; the center hole of the right bearing housing and the positioning hole of the right bearing are ground out in one go, and the coaxiality is ≤0.005mm.

[0007] Furthermore, the left end face of the spindle and the outer circle of the bearing seat are ground out in one go, and the perpendicularity is ≤0.01mm; the left end face of the left bearing seat and the bearing positioning hole are ground out in one go, and the perpendicularity is ≤0.01mm.

[0008] The beneficial effects of this invention compared with the prior art are: (1) This invention addresses the requirements for shaft rotation accuracy and internal leakage control of the turntable hydraulic motor assembly, solving two key technical difficulties: coaxial assembly of the component positioning holes and axial dimension assembly of the main shaft moving blades, thus ensuring shaft rotation accuracy and fit clearance; (2) This invention reduces the difficulty of precision machining and improves the performance indicators and feasibility of the hydraulic motor; (3) This invention is also applicable to the precision assembly process of hydraulic motor components with similar structures, dimensions and technical requirements. Attached Figure Description

[0009] Figure 1 This invention provides a process flow diagram to ensure the coaxial assembly of the positioning holes of the hydraulic motor assembly.

[0010] Figure 2 This invention provides a process flow diagram for ensuring the axial dimension alignment of the main shaft moving blades during assembly.

[0011] Figure 3 This is a front sectional view of the turntable hydraulic motor assembly of the present invention.

[0012] Figure 4 This is a cross-sectional view of the turntable hydraulic motor assembly of the present invention along the MM direction.

[0013] Figure 5 This is a cross-sectional view of the left bearing housing, main shaft, and stator assembly of the present invention.

[0014] Figure 6 This is a cross-sectional view of the left bearing housing of the present invention.

[0015] Figure 7 This is a cross-sectional view of the stator of the present invention.

[0016] Figure 8 This is a cross-sectional view of the right bearing housing of the present invention.

[0017] Reference numerals: 1-Spindle; 2-Left bearing cover; 3-Bearing 1; 4-Left bearing housing; 5-Locking pin; 6-Stator; 7-Reference axis; 8-Left end face of spindle; 9-Outer circle of bearing seat; 10-Bolt 1; 11-Left end face of left bearing housing; 12-Left end stepped end face of spindle moving blade; 13-Left end face of stator; 14-Right end face of stator; 15-Right end stepped end face of spindle moving blade; 16-Right end face of spindle; 17-Sealing ring; 18-Sealing strip; 19-Right bearing housing; 20-Bearing 2; 21-Right bearing cover; 22-Screw; 23-Bolt 2; 24-Left bearing positioning hole-; 25-Center hole of left bearing housing; 26-Reaming pin hole 1; 27-Stator hole; 28-Reaming pin hole 2; 29-Bearing positioning hole; 30-Center hole of right bearing housing. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments. The illustrative embodiments and descriptions herein are used to explain the present invention, but are not intended to limit the present invention.

[0019] Example: Figures 1-8 The precision assembly process of a rotary table hydraulic motor shown includes the following steps: S1. Ensure the hydraulic motor assembly positioning holes are aligned coaxially, including the following steps: S11. Finely grind the center hole 25 of the left bearing housing, the positioning hole 24 of the left bearing, the center hole 30 of the right bearing housing, and the positioning hole 29 of the bearing, so that the center hole 25 of the left bearing housing and the positioning hole 24 of the left bearing are coaxial, and the center hole 30 of the right bearing housing and the positioning hole 29 of the right bearing are coaxial, to serve as assembly transition reference holes. The center hole 25 of the left bearing housing and the positioning hole 24 of the left bearing are ground in one step, and the coaxiality is ≤0.005mm; the center hole 30 of the right bearing housing and the positioning hole 29 of the right bearing are ground in one step, and the coaxiality is ≤0.005mm. S12. Use bolt 10 to assemble the left bearing housing 4 and the stator 6 together; S13, upper vertical coordinate boring, use equal height block pads to position stator 6, first correct stator hole 27 to find the center, then check the coaxiality of stator hole and left bearing seat center hole <0.01mm, tighten bolt -10; S14. Flip the left bearing housing 4 and stator 6 assembly over, with the left bearing housing 4 in position, and check the left bearing positioning hole 24 and stator hole 27 for coaxiality using a dial indicator. S15. Flip the left bearing housing 4 and stator 6 assembly over again, drill reaming pin hole 1 26 and reaming pin hole 28 and drive in the positioning pin 5 to ensure the repeatability of the coaxiality of the positioning hole assembly after multiple disassembly and assembly. S16. Place the left bearing housing 4 and stator 6 assembly on the single-axis turntable. Use a dial indicator to recheck that the left bearing positioning hole 24 and stator hole 27 are coaxial. After the adjustment is qualified, disassemble the assembled parts. Through the rechecks in S14 and S16, the cumulative error of the parallelism machining of the positioning surfaces at both ends of the assembly and the operational errors in the process of correcting and tightening screws 22 and drilling and reaming pin holes are avoided from affecting the coaxiality of the assembly positioning hole assembly. S17. Use another bolt 10 to assemble the right bearing housing 19 with the stator 6. Refer to the correction operation of the left bearing housing 4 in steps S12 to S16 to correct the right bearing housing 19. After the adjustment is qualified, disassemble the assembled parts.

[0020] S2. Ensure the axial dimensions of the main shaft moving blades are aligned during assembly, including the following steps: S21. Determine the assembly measurement reference surface: Fine grind the left end face 8 of the spindle and the left end face 11 of the left bearing seat so that the left end face 8 of the spindle and the left end face 11 of the left bearing seat are perpendicular to the reference axis 7, which serves as the assembly measurement reference surface. The left end face 8 of the spindle and the outer circle 9 of the bearing seat are ground in one go, and the perpendicularity is ≤0.01mm; the left end face 11 of the left bearing seat and the bearing positioning hole 24 are ground in one go, and the perpendicularity is ≤0.01mm. S22. Determine the support height: Position the main shaft 1 on the marble platform with the right end face 16 as the positioning point. Measure the height of the left end step face 12 of the main shaft moving blade. Select and use equal height blocks and jacks to support the stator according to this height. S23. Adjust the clearance on one side: Adjust the jack according to the axial clearance value between the left end step face 12 of the main shaft moving blade and the left end face 13 of the stator, so that the left end face 13 of the stator is higher than the left end step face 12 of the main shaft moving blade, and level the left end face 13 of the stator. S24. Assembly: (All sealing rings 17 and sealing strips 18 from S21 to S211 are not installed yet) Install the left bearing housing 4 on the stator 6, drive in the locating pin 5 and fasten the two parts with bolt 10, install the bearing 3 into the main shaft 1, install the unmatched left bearing cover 2 on the left bearing housing 4, connect and tighten with screw 22. S25. First verification: With the dial indicator below the left bearing housing 4, the main shaft 1 and the stator 6 assembly, measure the axial clearance between the right end step face 15 of the moving blade and the right end face 14 of the stator. Verify the clearance adjusted in step S23 to avoid the impact of measurement and adjustment operation errors and machining errors of the axial dimensions of the main shaft 1 and stator 6 parts on the assembly alignment of the axial dimensions of the moving blade of the main shaft 1. S26. Determine the fit quantity of the left bearing cover: Remove the left bearing cover 2 and measure the axial clearance between the right end face 15 of the moving blade and the right end face 14 of the stator again to verify, so as to avoid the change of the axial clearance between the moving blade step end face and the stator end face under the two different states of bearing clamping and free; after confirming that there is no change, measure the step difference between the left end face 11 of the left bearing housing and the left end face of bearing-3, and add the preload of bearing-3 to determine the fit quantity of the left bearing cover 2. The fit quantity of the left bearing cover 2 meets the requirements. When measuring, the measurement is performed without preload on bearing-3, which eliminates the cumulative machining error and avoids the influence of bearing preload on the measurement of bearing cover fitting dimensions. S27. Measure the assembly reference dimension: Measure the distance between the left end face 8 of the spindle and the left end face 11 of the left bearing seat, and record it as the assembly measurement reference dimension; S28, Flipping: Install the left bearing cover 2 after the vehicle is assembled and tighten the screws 22. Flip the left bearing seat 4, main shaft 1 and stator 6. Position the main shaft with the left end face 8 and place it on the marble platform. Add a height block and jack support under the left bearing seat 4. S29. Second verification: Measure the axial clearance between the right end face 14 of the stator and the right end step face 15 of the moving blade of the main shaft to verify the clearance after the flipping operation, so as to avoid the loosening of the fit between the step face of the main shaft 1 and the bearing during the flipping process, which would cause the axial clearance between the step face of the moving blade and the end face of the stator to change. S210. Determine the machining quantity of the right bearing cover: Install the right bearing housing 19 on the stator 6 and connect it with bolt 23. Install the bearing 20 into the spindle 1. Measure the step difference between the right end face of the right bearing housing 19 and the right end face of the bearing 20, and add the preload of the bearing 20 to determine the machining quantity of the right bearing cover 21. The machining quantity of the right bearing cover 21 meets the requirements. When measuring, the measurement is performed without preload on the bearing 20, which eliminates the cumulative machining error and avoids the influence of bearing preload on the measurement of bearing cover fitting dimensions. S211, Re-inspection: Install the right bearing cover 21 after assembly and tighten the left and right bearing cover mounting screws 22. Measure the distance between the left end face 8 of the main shaft and the left end face 11 of the left bearing seat and compare it with the measurement value recorded in step S27. Re-inspect whether the axial dimension alignment of the moving blade is qualified. By comparing the assembly measurement reference dimensions before and after bearing preload, it is determined that the bearing preload is reasonable and the axial dimension alignment of the moving blade is qualified. S212. Self-inspection: The rotational accuracy of the shaft system is qualified. S213. Install sealing ring 17 and sealing strip 18: Disassemble the installed parts and install sealing ring 17 and sealing strip 18. Reassemble according to the above steps and re-check whether the axial dimension alignment of the moving blade is qualified.

[0021] This invention addresses the requirements for shaft rotation accuracy and internal leakage control in turntable hydraulic motor assemblies, solving two key technical challenges: coaxial assembly of component positioning holes and axial dimension alignment of main shaft moving blades. This ensures shaft rotation accuracy and fit clearance. Furthermore, this invention is also applicable to the precision assembly process of hydraulic motor assemblies with similar structures, dimensions, and technical requirements.

Claims

1. A precision assembly process method for a rotary table hydraulic motor, characterized in that, Includes the following steps: S1. Ensure the hydraulic motor assembly positioning holes are aligned coaxially, including the following steps: S11. Grind the center hole (25) of the left bearing housing, the positioning hole (24) of the left bearing housing, the center hole (30) of the right bearing housing, and the positioning hole (29) of the bearing housing so that the center hole (25) of the left bearing housing is coaxial with the positioning hole (24) of the left bearing housing, and the center hole (30) of the right bearing housing is coaxial with the positioning hole (29) of the right bearing housing, so as to serve as the assembly transition reference hole; S12. Use bolt one (10) to assemble the left bearing housing (4) and the stator (6) together; S13. Use the vertical coordinate boring machine to position the stator (6) with the equal height block pad. First, correct the center of the stator hole (27), then check the coaxiality of the stator hole (27) and the center hole (25) of the left bearing seat to be <0.01mm, and tighten the bolt (10). S14. Flip the left bearing housing (4) and stator (6) assembly over, with the left bearing housing (4) in position, and check the left bearing positioning hole (24) and stator hole (27) for coaxiality using a dial indicator. S15. Flip the left bearing housing (4) and stator (6) assembly over again, drill the first (26) and second (28) reaming pin holes and drive in the positioning pin (5). S16. Place the left bearing housing (4) and stator (6) assembly on the single-axis turntable, and check the left bearing positioning hole (24) and stator hole (27) for coaxiality using a dial indicator. After the adjustment is qualified, disassemble the assembled parts. S17. Use another bolt (10) to assemble the right bearing housing (19) with the stator (6). Refer to the correction operation of the left bearing housing (4) in steps S12 to S16 to correct the right bearing housing (19). After the adjustment is qualified, disassemble the installed parts. S2. Ensure the axial dimensions of the main shaft moving blades are aligned during assembly, including the following steps: S21. Determine the assembly measurement reference surface: Fine grind the left end face (8) of the spindle and the left end face (11) of the left bearing seat so that the left end face (8) of the spindle and the left end face (11) of the left bearing seat are perpendicular to the reference axis (7) and serve as the assembly measurement reference surface; S22. Determine the support height: Position the main shaft (1) on the marble platform with the right end face (16) in place. Measure the height of the left end step face (12) of the main shaft moving blade. Select and use equal height blocks and jacks to support the stator according to this height. S23. Adjust the clearance on one side: Adjust the jack according to the axial clearance value between the left end step face (12) of the main shaft moving blade and the left end face (13) of the stator, so that the left end face (13) of the stator is higher than the left end step face (12) of the main shaft moving blade, and level the left end face (13) of the stator. S24. Assembly: Install the left bearing housing (4) on the stator (6), drive in the positioning pin (5) and fasten the two parts with bolt one (10), install bearing one (3) into the main shaft (1), install the unmatched left bearing cover (2) on the left bearing housing (4), connect and tighten with screws (22); S25. First verification: The dial indicator is placed below the left bearing housing (4), the main shaft (1) and the stator (6) assembly. The dial indicator is used to measure the axial clearance between the right end step face (15) of the moving blade and the right end face (14) of the stator. The adjusted clearance in step S23 is verified. S26. Determine the matching quantity of the left bearing cover: Remove the left bearing cover (2) and measure the axial clearance between the right end step face (15) of the moving blade and the right end face (14) of the stator again for verification; after confirming that there is no change, measure the step difference between the left end face (11) of the left bearing seat and the left end face of the bearing (3), and add the preload of the bearing (3) to determine the matching quantity of the left bearing cover (2). The matching quantity of the left bearing cover (2) meets the requirements. S27. Measure the assembly reference dimension: Measure the distance between the left end face (8) of the spindle and the left end face (11) of the left bearing seat, and record it as the assembly measurement reference dimension; S28, Flip over: Install the left bearing cover (2) after the vehicle is assembled and tighten the screws (22), flip over the left bearing seat (4), main shaft (1) and stator (6), position it with the left end face (8) of the main shaft and place it on the marble platform, add equal height blocks and jacks for support under the left bearing seat (4); S29. Second verification: Measure the axial clearance between the right end face (14) of the stator and the right end step end face (15) of the main shaft moving blade to verify the clearance after the flipping operation. S210. Determine the right bearing cover matching quantity: Install the right bearing housing (19) on the stator (6) and connect it with bolt two (23). Install bearing two (20) into the main shaft (1). Measure the step difference between the right end face of the right bearing housing (19) and the right end face of bearing two (20), and add the preload of bearing two (20) to determine the right bearing cover (21) matching quantity. Match the right bearing cover (21) to meet the requirements. S211, Re-inspection: Install the right bearing cover (21) after vehicle assembly and tighten the left and right bearing cover mounting screws (22). Measure the distance between the left end face (8) of the main shaft and the left end face (11) of the left bearing seat and compare it with the measurement value recorded in step S (27) to re-inspect whether the axial dimension alignment of the moving blade is qualified. S212. Self-inspection: The rotational accuracy of the shaft system is qualified. S213. Add sealing ring (17) and sealing strip (18): Disassemble the installed parts and add sealing ring (17) and sealing strip (18). Reassemble according to the above steps and re-check whether the axial dimension alignment of the moving blade is qualified.

2. The precision assembly process method for a rotary table hydraulic motor as described in claim 1, characterized in that, The center hole (25) of the left bearing housing and the positioning hole (24) of the left bearing are ground out in one go, and the coaxiality is ≤0.005mm; the center hole (30) of the right bearing housing and the positioning hole (29) of the right bearing are ground out in one go, and the coaxiality is ≤0.005mm.

3. The precision assembly process method for a rotary table hydraulic motor as described in claim 1, characterized in that, The left end face (8) of the main spindle and the outer circle (9) of the bearing seat are ground out in one go, and the perpendicularity is ≤0.01mm; the left end face (11) of the left bearing seat and the bearing positioning hole (24) are ground out in one go, and the perpendicularity is ≤0.01mm.

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