High-precision spline machining method

Abstract

The invention belongs to the technical field of spline machining, and particularly relates to a high-precision spline machining method. Comprising the following steps that gear rolling before heating is conducted, the allowance is reserved for 0.15, heat treatment is conducted, rough grinding and semi-accurate grinding are conducted on a spline blank, aging treatment is conducted on a spline shaft, accurate grinding is conducted after a grinding wheel is trimmed again after aging, and finishing is conducted after grinding is finished. Preserving heat at room temperature after finishing; and measuring the tooth profile deviation of the spline tooth surface and performing corresponding treatment, and repeating the process until the deviation is qualified. A gear rolling process is adopted for hot working before heat treatment of the spline, and compared with a spline pre-heating and post-heating rolling process, the machining efficiency is effectively improved, the machining precision can reach 4-5 levels, and the comprehensive machining cost is reduced by 2 / 5.

Description

Technical Field

[0001] The invention belongs to the technical field of spline processing, and in particular relates to a high-precision spline processing method. Background Art

[0002] At present, the main method for processing external splines of motor shafts is to use the knurling key processing technology. Knurling key processes with different precision and process requirements are used before and after heat treatment. The two knurling processes are costly and time-consuming. Especially for the processing of high-precision splines, its processing efficiency will be greatly limited, and it is difficult to meet the needs of large-scale continuous production. At the same time, the knurling key process has limited accuracy, and it is difficult to guarantee the processing accuracy of some high-precision splines. Summary of the Invention

[0003] The object of the present invention is to provide a high-precision spline machining method based on gear rolling before heat treatment and grinding after heat treatment, so as to ensure the machining accuracy of high-precision splines while improving their production efficiency.

[0004] To achieve the above objectives, the present invention adopts the following technical solutions.

[0005] A high-precision spline machining method comprises the following steps:

[0006] A. Hot pre-gear rolling process, with a margin of 0.15mm, and the initial diameter of the shaft blank is ;

[0007] in Refers to the number of teeth, Refers to the pitch circle diameter, It refers to the angular pressure at the pitch circle, It refers to the tooth tip circle pressure angle, It refers to the root circle pressure angle, Refers to the diameter of the tooth tip circle, Refers to the root diameter of the tooth, Refers to the tooth thickness of the tooth top arc. Refers to the tooth root arc thickness;

[0008] B. Heat treatment is carried out in a continuous carburizing furnace and includes the following steps in sequence:

[0009] B1. Strong penetration treatment: Maintain 1.0% carbon potential and heat evenly at 65~80 To 850℃~900℃ for 90~150 ;

[0010] B2, Diffusion treatment: maintain carbon potential at 0.76%, uniform temperature drop to 850~880℃; maintain carbon potential at 0.86%, constant temperature at 45 minute;

[0011] B3, quenching and heat preservation treatment: maintain carbon potential at 0.76%, cool evenly to 820℃~835℃ and keep warm for 50~60 ;

[0012] B4, oil cooling treatment;

[0013] C. According to the rolling distance error =3~4 Drive the grinding assembly to perform rough grinding on the spline blank. The single grinding amount during rough grinding is 5~10 , first by single feed 10 Rough grinding: During the grinding process, the grinding amount is gradually reduced as the grinding area of ​​the spline tooth surface expands. When the entire spline tooth surface can be ground, the single feed is 5 Grind 2~3 times; during the grinding process, use a single crystal diamond pen to dress the grinding wheel as needed. The grinding amount of the single crystal diamond pen is 20~40 , working stroke 1 time, dressing speed is 1~2 ;

[0014] D. According to the rolling distance error =2 Semi-fine grinding, single grinding amount is about 1~3 During the grinding process, the grinding wheel is dressed with a single crystal diamond pen as needed. The grinding amount of the single crystal diamond pen is 20~40 , working stroke 1 time, dressing speed is 1~2 ;

[0015] E. Perform aging treatment on the spline shaft, and then dress the grinding wheel again after aging. =2 Fine grinding, single grinding amount is about 0.5~1 During the grinding process, the grinding wheel is dressed with a single crystal diamond pen as needed. The grinding amount of the single crystal diamond pen is 5~10 , working stroke 1~2 times, idle stroke 1~2 times, dressing speed is 0.5~1 ;

[0016] F. After the entire spline tooth surface can be ground in a single feed, the rolling distance error =1 , single grinding amount 0.2 Fine grinding: use a single crystal diamond pen to dress the grinding wheel as needed during the grinding process;

[0017] G. After the entire spline tooth surface can be ground in a single feed, the rolling distance error =0 , single grinding amount 0.2 , total grinding amount 0.5~1 Fine grinding: Use a single crystal diamond pen to dress the grinding wheel as needed during the grinding process; the machine should be preheated for more than 3 hours before each fine grinding to ensure sufficient thermal expansion of the grinding wheel spindle;

[0018] H. Stop feeding and drive the grinding assembly to reciprocate 4 to 8 times for finishing processing;

[0019] I. After finishing, keep warm at room temperature of 20℃±0.5℃ for 12 hours;

[0020] J. Measure the tooth profile deviation of the spline tooth surface. If it meets the requirements of the tooth profile shape deviation within the measurement range, the spline shaft is aged again and the spline shaft is finally measured. If it does not meet the requirements, the rolling distance error is corrected according to the involute profile of the tooth root. When the tooth profile of the tooth root deviates toward the body, the rolling distance error is corrected. =-1~0 , single grinding amount 0.2 , total grinding volume is about 0.5 ~1 Fine grinding and finishing; when the tooth profile at the root of the tooth deviates to the outside of the body, the rolling distance error =0~1 , fine grinding and finishing with the same parameters, then measure again. If it meets the requirements, aging treatment and final measurement are carried out. If it does not meet the requirements, repeat the above process.

[0021] A further improvement or preferred embodiment of the above-mentioned high-precision spline machining method is that the shaft blank needs to be positioned in the machine tool under the action of the front and rear centers of the machine tool, and the center pressure is 800~100 , Gear rolling forming pressure: 800~1200 .

[0022] A further improvement or preferred embodiment of the above-mentioned high-precision spline processing method is that during the gear rolling forming process, the rotation speed of the shaft blank is constant, and the circumferential speed of the shaft blank is 8-10 During the gear rolling process, the gear rolling plate is forced to be lubricated with oil mist.

[0023] A further improvement or preferred embodiment of the above-mentioned high-precision spline machining method is that when machining a spline shaft, the grinding is started from the tooth top, and the grinding assembly is driven to roll toward the tooth root, and then the direction is reversed and rolled toward the tooth top until it is released from the grinding wheel; after the feed, the above process is repeated again until the entire spline tooth surface can be ground after a single feed, and then the grinding amount is reduced and the above process is repeated until a single feed of 0.2 The entire spline tooth surface can be ground, completing the grinding process.

[0024] A further improvement or preferred embodiment of the above-mentioned high-precision spline machining method is that the spline tooth profile deviation is measured and the following steps are performed:

[0025] S1. Adjust the probe point to the upper side of the measuring plane by visual inspection to make the measuring point position deviation ;Measure the tooth profile deviation of the tooth surface to be measured, and measure every 1 The expanded length is 10 to 30 sampling points;

[0026] S2, then move the probe 20~50 degrees along the normal of the measuring plane , measure again, at this time the tooth profile deviation at the root gradually deviates to the outside of the body and is compressed along the expanded length;

[0027] S3, continue to move upward to adjust the probe, each time by 20~50 Repeat the measurement until the tooth profile deviation of the tooth root near the non-base circle is biased toward the body and compressed along the expanded length. At this time, the position deviation of the measuring point is ;

[0028] S4, move the probe downward 50~100 , and then adjust the probe movement to 5~10 , repeat steps S1 to S3 several times to fit the deviation measurement results of different probe positions. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the spline shaft cold rolling forming principle;

[0030] Figure 2 This is a schematic diagram of the cold-rubbing spline replacement processing principle;

[0031] Figure 3 It is a schematic diagram of the principle of measuring spline tooth profile deviation. DETAILED DESCRIPTION

[0032] The present invention is described in detail below with reference to specific embodiments.

[0033] In this application, the spline is subjected to a gear rolling process before heat treatment, which effectively improves the processing efficiency compared with the spline rolling process before and after heat treatment. At the same time, an improved grinding and grading processing process is adopted after heat treatment. Based on the processing process of this application, its processing accuracy can reach level 4-5. At the same time, the comprehensive processing cost and processing time can be shortened by about 2 / 5, which can effectively improve the production efficiency of high-precision splines, ensure their processing accuracy, and reduce the production costs of enterprises.

[0034] Specifically, the high-precision spline processing method of the present application mainly includes the steps of cold rolling pre-processing before heat treatment and graded grinding processing after heat treatment. The specific steps include:

[0035] A. Cold rolling before hot forming, with a margin of 0.15mm. Cold rolling splines are a high-speed plastic cold forming process. The working principle of cold rolling of spline shafts is as follows: Figure 1 As shown, the upper and lower tooth rolling plates are extruded with the tooth top surface, side tooth surface and tooth bottom surface of the spline shaft blank. Through the continuous extrusion between the working surface and the surface of the shaft blank, the spline shaft blank is driven to rotate and the tooth shape is gradually formed.

[0036] The forming process of cold-rolled spline processing is a replacement process. Through the extrusion of the shaft blank forming process, it can be regarded as the transfer (replacement) of the material corresponding to the tooth bottom area to the area where the tooth top is located, such as Figure 2 As shown, selecting the shaft blank size of the department can optimize the gear rolling process and reduce the subsequent processing volume; the initial diameter of the shaft blank can be obtained by calculation:

[0037] ;

[0038] in Refers to the number of teeth, Refers to the pitch circle diameter, It refers to the angular pressure at the pitch circle, It refers to the tooth tip circle pressure angle, It refers to the root circle pressure angle, Refers to the diameter of the tooth tip circle, Refers to the root diameter of the tooth, Refers to the tooth thickness of the tooth top arc. Refers to the tooth root arc thickness;

[0039] The shaft blank needs to be positioned in the machine tool under the action of the front and rear centers of the machine tool. The front and rear centers give force. Since the tooth rolling part will have a certain amount of beating relative to the axis during the processing, excessive pressure from the center will cause the shaft blank to bend and increase, resulting in problems such as cumulative deviation of the spline tooth pitch. Preferably, the center pressure is 80~100 More suitable, gear forming pressure: 800~1200 ;

[0040] During the gear rolling process, the rotation speed of the shaft blank remains constant. In actual implementation, according to the rate of plastic flow deformation of the material in the deformation zone, the circumferential speed of the shaft blank is recommended to be 8~10 For shafts of different diameters, the appropriate rotational speed can be determined based on the circumferential speed. During the gear rolling process, the gear rolling plate must be lubricated with forced oil mist (usually 40# guide rail oil is used).

[0041] B. Heat treatment is carried out in a continuous carburizing furnace and includes the following steps in sequence:

[0042] B1. Strong penetration treatment: Maintain 1.0% carbon potential and heat evenly at 65~80 To 850℃~900℃ for 90~150 ;

[0043] B2, Diffusion treatment: maintain carbon potential at 0.76%, uniform temperature drop to 850~880℃; maintain carbon potential at 0.86%, constant temperature at 45 ;

[0044] B3, quenching and heat preservation treatment: maintain carbon potential at 0.76%, cool evenly to 820℃~835℃ and keep warm for 50~60 ;

[0045] B4, oil cooling treatment;

[0046] Based on the above process, the spline shaft blank was quenched under different heat treatment temperature and heat treatment time parameters, and its key parameters such as deformation, curve deviation and surface hardness were measured. The results are shown in Table 1.

[0047] Table 1 Key parameters of spline at different heat temperatures and treatment times

[0048] Serial number Strong permeation treatment temperature ℃ Intensive treatment time#timg# Diffusion processing time#timg# Deformation Curve deviation#timg# Surface hardness#timg# 1 905 130 60 45.67 10.66 745.04 2 900 190 45 46.37 9.92 745.71 3 885 130 30 45.67 10.66 745.04 4 885 130 45 45.80 10.52 742.19 5 885 180 45 46.23 10.30 745.51 6 885 170 30 46.09 10.09 745.48 7 905 170 30 46.09 10.09 745.48 8 885 145 50 46.00 10.16 745.34 9 900 170 35 46.06 10.37 745.36 10 905 132 45 45.80 10.82 745.34

[0049] As shown in Table 1, after heat treatment based on the aforementioned heat treatment parameters, the physical parameters of the rough-machined tooth surface of the spline meet the necessary hardness index requirements. The hardened spline shaft has better wear resistance and impact resistance, but the corresponding processing difficulty is also higher. In order to ensure the highest possible processing efficiency while minimizing the processing error as much as possible, this application adopts the following multi-pass grinding process to further process the spline, including rough grinding, semi-finishing grinding, fine grinding and other process flows. Specifically:

[0050] C. According to the rolling distance error =3~4 Drive the grinding assembly to perform rough grinding on the spline blank. The single grinding amount during rough grinding is 5~10 , first by single feed 10 Rough grinding: During the grinding process, the grinding amount is gradually reduced as the grinding area of ​​the spline tooth surface expands. When the entire spline tooth surface can be ground, the single feed is 5 Grind 2~3 times; during the grinding process, use a single crystal diamond pen to dress the grinding wheel as needed. The grinding amount of the single crystal diamond pen is 20~40 , working stroke 1 time, dressing speed is 1~2 ;

[0051] In particular, in order to facilitate tool setting, when processing spline shafts, start grinding from the tooth top and drive the grinding assembly to roll toward the tooth root, then reverse and roll toward the tooth top until it is out of the grinding wheel. After feeding, repeat the above process again until the entire spline tooth surface can be ground after a single feed, then reduce the grinding amount and repeat the above process until a single feed of 0.2 The entire spline tooth surface can be ground, ending the grinding;

[0052] In theory, the feed rate refers to the depth of the exposed abrasive that can cut into the workpiece. The exposed part of the abrasive is the key to how high the feed rate can be adjusted. The size of the feed rate determines the depth of the tool's cutting on the workpiece. Increasing the feed rate will increase the corresponding grinding depth. Although it can remove surface material faster, it will cause tool overload, deformation of the spline surface due to stress, and reduced processing quality.

[0053] Through multiple comprehensive tests and analyses, this application divides the spline grinding process into multiple progressive stages: rough grinding in the initial stage, semi-finishing grinding and fine grinding in the second stage, and repeated fine grinding after measurement and calibration. By reasonably controlling the number of grinding passes and the grinding feed, the stability of the microstructure during spline shaft processing is improved, achieving compatibility and excellence in terms of efficient grinding, product productivity, and spline processing accuracy. The specific steps are as follows:

[0054] D. According to the rolling distance error =2 Semi-fine grinding, single grinding amount is about 1~3 During the grinding process, the grinding wheel is dressed with a single crystal diamond pen as needed. The grinding amount of the single crystal diamond pen is 20~40 , working stroke 1 time, dressing speed is 1~2 ;

[0055] E. Perform aging treatment on the spline shaft, and then dress the grinding wheel again after aging. =2 Fine grinding, single grinding amount is about 0.5~1 During the grinding process, the grinding wheel is dressed with a single crystal diamond pen as needed. The grinding amount of the single crystal diamond pen is 5~10 , working stroke 1~2 times, idle stroke 1~2 times, dressing speed is 0.5~1 ;

[0056] F. After the entire spline tooth surface can be ground in a single feed, the rolling distance error =1 , single grinding amount 0.2 Fine grinding: use a single crystal diamond pen to dress the grinding wheel as needed during the grinding process;

[0057] G. After the entire spline tooth surface can be ground in a single feed, the rolling distance error =0 , single grinding amount 0.2 , total grinding amount 0.5~1 Before each fine grinding, the machine should be preheated for more than 3 hours to ensure sufficient thermal expansion of the grinding wheel spindle;

[0058] H. No longer feed the tool, drive the grinding assembly to reciprocate 4 to 8 times for finishing processing;

[0059] I. After finishing, keep warm at room temperature of 20℃±0.5℃ for 12 hours;

[0060] J. Measure the tooth profile deviation of the spline tooth surface. If the tooth profile shape deviation meets the requirements within the measurement range, the gear involute template is aged again and the gear involute template is finally measured. If it does not meet the requirements, the rolling distance error is corrected according to the involute profile of the tooth root. When the tooth profile of the tooth root deviates toward the body, the rolling distance error is corrected. =-1~0 , single grinding amount 0.2 , the total grinding amount is about 0.5~1 Fine grinding and finishing; when the tooth profile at the root of the tooth deviates to the outside of the body, the rolling distance error =0~1 2. Fine grinding and finishing with the same parameters, then measuring again. If it meets the requirements, aging treatment and final measurement are carried out. If it does not meet the requirements, repeat the above process;

[0061] like Figure 3 As shown in the figure, during the measurement of the tooth profile deviation of the spline tooth surface, in an ideal state, when the tooth surface involute is measured using the generating mechanism, the theoretical measuring point contacts the involute of the tooth surface to be measured in the plane. If the involute of the tooth surface is a standard involute, the probe will not move. Otherwise, the probe will have a deviation along the generating line direction. This deviation is the tooth profile deviation. When the deviation exists, the actual measuring points where the probe contacts the involute to be measured will be distributed in an area on the probe.

[0062] Based on the above measurement principle, it can be seen that the deviation of the measuring point position will cause the tooth profile measurement deviation near the base circle; the larger the absolute value of the measuring point position deviation and the smaller the probe ball diameter, the greater the tooth profile deviation measurement error caused by the measuring point position deviation; when the probe radius is infinite, that is, it becomes a plane, the measuring point position deviation will not cause measurement error, which is in line with the involute generation principle. The actual measuring room probe diameter is necessarily small. For this reason, this application is based on the following improved measurement scheme to improve the measurement accuracy of the spline tooth surface tooth profile deviation, so as to better determine the tooth profile deviation and improve the accuracy of high-precision spline processing. Specifically, it includes the following steps:

[0063] S1. Adjust the probe point to the upper side of the measuring plane by visual inspection to make the measuring point position deviation ;Measure the tooth profile deviation of the tooth surface to be measured, and measure every 1 The expanded length is 10 to 30 sampling points;

[0064] S2, then move the probe 20~50 degrees along the normal of the measuring plane , measure again, at this time the tooth profile deviation at the root gradually deviates to the outside of the body and is compressed along the expanded length;

[0065] S3, continue to move upward to adjust the probe, each time by 20~50 Repeat the measurement until the tooth profile deviation of the tooth root near the non-base circle is biased toward the body and compressed along the expanded length. At this time, the position deviation of the measuring point is ;

[0066] S4, move the probe downward 50~100 , and then adjust the probe movement to 5~10 , repeat steps S1 to S3 several times to fit the deviation measurement results of different probe positions.

[0067] After testing, the above method can effectively avoid the two errors caused by the measurement method and the structural limitations of the measuring device itself, and realize the offset of positive and negative errors through bidirectional fitting, which is beneficial to the measurement and correction of the involute template tooth profile deviation. It can effectively reduce the influence of the positive tooth top fillet and the probe size deviation on the involute tooth profile deviation measurement results, ensure accurate and effective measurement, and help to further improve the processing accuracy of the spline.

[0068] The present invention is mainly used for the processing and preparation of high-precision splines and high-hardness and high-precision splines positioned by internal teeth.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A high-precision spline machining method, characterized in that: The steps include: A. Hot pre-gear rolling process, with a margin of 0.15, and the initial diameter of the shaft blank is ; in Refers to the number of teeth, Refers to the pitch circle diameter, It refers to the angular pressure at the pitch circle, It refers to the tooth tip circle pressure angle, It refers to the root circle pressure angle, Refers to the diameter of the tooth tip circle, Refers to the root diameter of the tooth, Refers to the tooth thickness of the tooth top arc. Refers to the tooth root arc thickness; B. Heat treatment is carried out in a continuous carburizing furnace and includes the following steps in sequence: B1. Strong penetration treatment: Maintain 1.0% carbon potential and heat evenly at 65~80 To 850℃~900℃ for 90~150 ; B2, Diffusion treatment: maintain carbon potential at 0.76%, uniform temperature drop to 850~880℃; maintain carbon potential at 0.86%, constant temperature at 45 minute; B3, quenching and heat preservation treatment: maintain carbon potential at 0.76%, cool evenly to 820℃~835℃ and keep warm for 50~60 ; B4, oil cooling treatment; C. According to the rolling distance error =3~4 Drive the grinding assembly to perform rough grinding on the spline blank. The single grinding amount during rough grinding is 5 ~10 , first by single feed 10 Rough grinding: During the grinding process, the grinding amount is gradually reduced as the grinding area of ​​the spline tooth surface expands. When the entire spline tooth surface can be ground, the single feed is 5 Grind 2~3 times; during the grinding process, use a single crystal diamond pen to dress the grinding wheel as needed. The grinding amount of the single crystal diamond pen is 20 ~40 , working stroke 1 time, dressing speed is 1~2 ; D. According to the rolling distance error =2 Semi-fine grinding, single grinding amount is about 1 ~3 ; During the grinding process, the grinding wheel is dressed with a single crystal diamond pen as needed. The grinding amount of the single crystal diamond pen is 20 ~40 , working stroke 1 time, dressing speed is 1~2 ; E. Perform aging treatment on the spline shaft, and then dress the grinding wheel again after aging. =2 Fine grinding, single grinding amount is about 0.5~1 During the grinding process, the grinding wheel is dressed with a single crystal diamond pen as needed. The grinding amount of the single crystal diamond pen is 5~10 , working stroke 1~2 times, idle stroke 1~2 times, dressing speed is 0.5~1 ; F. After the entire spline tooth surface can be ground in a single feed, the rolling distance error =1 , single grinding amount 0.2 Fine grinding: use a single crystal diamond pen to dress the grinding wheel as needed during the grinding process; G. After the entire spline tooth surface can be ground in a single feed, the rolling distance error =0 , single grinding amount 0.2 , total grinding amount 0.5~1 Fine grinding: During the grinding process, the grinding wheel is dressed with a single crystal diamond pen as needed; Before each fine grinding, the machine should be preheated for more than 3 hours to ensure sufficient thermal expansion of the grinding wheel spindle; H. Stop feeding and drive the grinding assembly to reciprocate 4 to 8 times for finishing processing; I. After finishing, keep warm at room temperature of 20℃±0.5℃ for 12 hours; J. Measure the tooth profile deviation of the spline tooth surface. If it meets the requirements of the tooth profile shape deviation within the measurement range, the spline shaft is aged again and the spline shaft is finally measured. If it does not meet the requirements, the rolling distance error is corrected according to the involute profile of the tooth root. When the tooth profile of the tooth root deviates toward the body, the rolling distance error is corrected. =-1~0 , single grinding amount 0.2 , total grinding volume is about 0.5 ~1 Fine grinding and finishing; when the tooth profile at the root of the tooth deviates to the outside of the body, the rolling distance error =0~1 , fine grinding and finishing with the same parameters, then measure again. If it meets the requirements, aging treatment and final measurement are carried out. If it does not meet the requirements, repeat the above process.

2. The high-precision spline machining method according to claim 1, characterized in that: The shaft blank needs to be positioned in the machine tool under the action of the front and rear centers of the machine tool, and the center pressure is , gear rolling forming pressure: .

3. The high-precision spline machining method according to claim 1, characterized in that: During the gear rolling process, the rotation speed of the shaft blank remains constant, and the peripheral speed of the shaft blank is 8~10 During the gear rolling process, the gear rolling plate is forced to be lubricated with oil mist.

4. The high-precision spline machining method according to claim 1, characterized in that: When machining a spline shaft, start grinding from the tooth top and drive the grinding assembly to roll toward the tooth root, then reverse and roll toward the tooth top until it is out of the grinding wheel; repeat the above process again after feeding until the entire spline tooth surface can be ground after a single feed, then reduce the grinding amount and repeat the above process until a single feed of 0.2 The entire spline tooth surface can be ground, completing the grinding process.

5. The high-precision spline machining method according to claim 1, characterized in that: The measurement of the spline tooth profile deviation is carried out in the following steps: S1. Adjust the probe point to the upper side of the measuring plane by visual inspection to make the measuring point position deviation ;Measure the tooth profile deviation of the tooth surface to be measured, and measure every 1 The expanded length is 10 to 30 sampling points; S2, then move the probe 20~50 degrees along the normal of the measuring plane , measure again, at this time the tooth profile deviation at the root gradually deviates to the outside of the body and is compressed along the expanded length; S3, continue to move upward to adjust the probe, each time by 20~50 Repeat the measurement until the tooth profile deviation of the tooth root near the non-base circle is biased toward the body and compressed along the expanded length. At this time, the position deviation of the measuring point is ; S4, move the probe downward 50~100 , and then adjust the probe movement to 5~10 , repeat steps S1 to S3 several times to fit the deviation measurement results of different probe positions.

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