Method for high-precision machining of splines

Abstract

The application belongs to the technical field of spline machining, and particularly relates to a high-precision spline machining method. The method comprises the following steps: hot tooth rolling machining, leaving a 0.15 allowance, heat treatment, rough grinding, semi-fine grinding of the spline blank, aging treatment of the spline shaft, fine grinding after the aging treatment and reconditioning of the grinding wheel, and finishing machining after the grinding is completed; room temperature preservation after the finishing machining; measuring spline tooth surface profile deviation and making corresponding adjustments, and repeating the above process until the deviation is qualified. The hot machining before the heat treatment of the spline adopts the tooth rolling process, which effectively improves the machining efficiency compared with the hot-before-and-hot-after spline rolling process, the machining precision can reach 4-5 levels, and the comprehensive machining cost is reduced by 2 / 5.

Description

Technical Field

[0001] This invention belongs to the field of spline machining technology, and particularly relates to a high-precision spline machining method. Background Technology

[0002] Currently, the main method for machining external splines on motor shafts is to use knurling technology. Different knurling processes with different precision and process requirements are used before and after heat treatment. The two knurling processes are costly and time-consuming. In particular, for the machining of high-precision splines, the machining efficiency is greatly limited, making it difficult to meet the needs of large-scale continuous production. At the same time, the precision of the knurling process is limited, making it difficult to guarantee the machining accuracy of some high-precision splines. Summary of the Invention

[0003] The purpose of this 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 improve the production efficiency while ensuring the high precision of spline machining.

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

[0005] A method for high-precision machining of splines includes the following steps:

[0006] A. Preheating gear rolling, leaving a allowance of 0.15mm, the initial diameter of the shaft blank is... ;

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

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

[0009] B1. Strong infiltration treatment: Maintain 1.0% carbon potential, and heat evenly for 65~80 degrees Celsius. Perform 90-150 minutes at 850℃~900℃. ;

[0010] B2. Diffusion treatment: Maintain carbon potential at 0.76%, uniformly reduce temperature to 850~880℃; maintain carbon potential at 0.86%, hold at a constant temperature of 45℃. minute;

[0011] B3. Quenching and heat preservation treatment: Maintain carbon potential at 0.76%, uniformly cool to 820℃~835℃ and hold for 50~60 minutes. ;

[0012] B4. Oil cooling treatment;

[0013] C. Based on rolling distance error =3~4 The drive grinding assembly performs rough grinding on the spline blank, with a single grinding depth of 5-10 mm during rough grinding. First, start with a single infeed of 10. In rough grinding, the grinding amount is gradually reduced as the area to be ground on the spline tooth surface expands. Once the entire spline tooth surface can be ground, the single feed rate is increased to 5. Grind 2-3 times; during grinding, use a single-crystal diamond grinding wheel to dress the grinding wheel as needed, with a grinding depth of 20-40 mm. One work trip, with a repair speed of 1-2. ;

[0014] D. Based on rolling distance error =2 Semi-finish grinding, with a single grinding amount of approximately 1-3. During the grinding process, the grinding wheel is dressed using a single-crystal diamond dressing tool as needed, with a dressing depth of 20-40 mm. One work trip, with a repair speed of 1-2. ;

[0015] E. Perform aging treatment on the spline shaft, and then dress the grinding wheel again according to the rolling distance error. =2 Fine grinding, with a single grinding amount of approximately 0.5~1. During the grinding process, the grinding wheel is dressed using a single-crystal diamond dressing tool as needed, with a dressing depth of 5-10. 1-2 working strokes, 1-2 idle strokes, and a repair speed of 0.5-1. ;

[0016] F. After the entire spline tooth surface can be ground in a single feed, calculate the rolling distance error. =1 Single grinding amount: 0.2 In fine grinding, the grinding wheel is dressed using a single-crystal diamond dressing tool 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 is considered. =0 Single grinding amount: 0.2 Total grinding amount 0.5~1 For fine grinding, the grinding wheel should be dressed using a single-crystal diamond pen as needed during the grinding process; the machine should be preheated for more than 3 hours before each fine grinding to ensure sufficient thermal elongation of the grinding wheel spindle;

[0018] H. Stop the feed and drive the grinding assembly to reciprocate 4-8 times for finishing.

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

[0020] J. Measure the tooth profile deviation of the spline. If it meets the requirements for tooth profile shape deviation within the specified range, perform aging treatment on the spline shaft again and conduct a final measurement. If it does not meet the requirements, correct the rolling distance error based on the involute profile at the tooth root. When the tooth root profile deviates towards the inside of the shaft, adjust the rolling distance error accordingly. =-1~0 Single grinding amount: 0.2 Total grinding amount is approximately 0.5. ~1 Fine grinding and finishing; when the tooth root profile deviates outward, the rolling distance error is considered. =0~1 The same parameters are used for fine grinding and finishing, and then the measurement is performed again. If the requirements are met, aging treatment and final measurement are performed. If the requirements are not met, the above process is repeated.

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

[0022] In a further improvement or preferred embodiment of the aforementioned high-precision spline machining method, the rotational speed of the shaft blank remains constant during the gear rolling process, and the circumferential speed of the shaft blank is 8~10. During the tooth rolling process, ensure that the tooth rolling plate is lubricated by forced oil mist.

[0023] A further improvement or preferred embodiment of the aforementioned high-precision spline machining method involves, when machining a spline shaft, starting the grinding process from the tooth tip and driving the grinding assembly to roll towards the tooth root. Then, the direction is reversed, and the assembly rolls towards the tooth tip until it disengages from the grinding wheel. This process is repeated after each feed until the entire spline tooth surface can be ground in a single feed. The grinding depth is then reduced, and the process is repeated until a single feed depth of 0.2 mm is achieved. The entire spline tooth surface can be ground, and the grinding process is then complete.

[0024] A further improvement or preferred embodiment of the aforementioned high-precision spline machining method includes the following steps for measuring the spline tooth profile deviation:

[0025] S1. Visually adjust the probe's measuring point to the upper side of the measuring plane, reducing the positional deviation of the measuring point. ; Measure the profile deviation of the tooth surface to be measured, and measure every 1 The unfolded length is set to 10-30 sampling points;

[0026] S2. Then move the probe 20-50 degrees along the normal direction of the measuring plane. Upon measurement again, the tooth profile deviation at the root gradually shifts outward and is compressed along the unfolded length;

[0027] S3. Continue to move the probe upwards, adjusting it by 20-50 degrees each time. Repeat the measurement until the tooth profile deviation near the tooth root (excluding the base circle) is biased inwards and compressed along the unfolded length. At this point, the measurement point position deviation is determined. ;

[0028] S4. Move the probe downwards by 50-100 degrees. Then adjust the probe's movement amount to 5~10 each time. Repeat steps S1 to S3 several times to fit the deviation measurement results of different probe positions. Attached Figure Description

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

[0030] Figure 2 This is a schematic diagram illustrating the principle of cold knurling replacement machining.

[0031] Figure 3 This is a schematic diagram illustrating the principle of measuring the profile deviation of splined teeth. Detailed Implementation

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

[0033] In this application, the heat treatment of splines before heat treatment adopts a gear rolling process, which effectively improves the processing efficiency compared to the pre-heat and post-heat rolling process. At the same time, an improved grinding and grading process is adopted after heat treatment. Based on the processing technology of this application, the processing accuracy can reach level 4-5. Meanwhile, the overall 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 cost of enterprises.

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

[0035] A. Cold rolling of splines before hot forming, leaving a 0.15mm allowance. Cold rolling of splines is 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 gradually form a tooth shape.

[0036] The forming process of cold-rolled splines is a replacement process. Through the extrusion of the shaft blank, the forming process can be viewed as a transfer (replacement) of material from the tooth root region to the tooth tip region. Figure 2 As shown, selecting the appropriate shaft blank size can optimize the gear rolling process and reduce subsequent machining. The initial diameter of the shaft blank can be calculated as follows:

[0037] ;

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

[0039] The shaft blank needs to be positioned in the machine tool by the action of the front and rear centers. Force is applied by these centers. Because the gear-rolling section will have some runout relative to the axis during machining, excessive center pressure will cause increased bending of the shaft blank, leading to problems such as accumulated deviations in spline tooth pitch. Preferably, the center pressure is 80~100. Suitable rolling forming pressure: 800~1200 ;

[0040] During the gear rolling process, the rotational speed of the shaft blank remains constant. In practice, based on the rate of plastic flow deformation of the material in the deformation zone, a circumferential speed of 8~10 is recommended for the shaft blank. For shaft blanks of different diameters, the appropriate rotation speed can be determined based on the circumferential speed. During the gear rolling process, the gear rolling plate is guaranteed to be lubricated by forced oil mist (generally using 40# guide rail oil).

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

[0042] B1. Strong infiltration treatment: Maintain 1.0% carbon potential, and heat evenly for 65~80 degrees Celsius. Perform 90-150 minutes at 850℃~900℃. ;

[0043] B2. Diffusion treatment: Maintain carbon potential at 0.76%, uniformly reduce temperature to 850~880℃; maintain carbon potential at 0.86%, hold at a constant temperature of 45℃. ;

[0044] B3. Quenching and heat preservation treatment: Maintain carbon potential at 0.76%, uniformly cool to 820℃~835℃ and hold for 50~60 minutes. ;

[0045] B4. Oil cooling treatment;

[0046] Based on the aforementioned process, the splined shaft blank was quenched under different heat treatment temperatures and 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 splines under different heat temperatures and processing times.

[0048] Serial Number Intensive osmosis treatment temperature (°C) Strong infiltration treatment time diffusion treatment time Deformation Curve deviation Surface hardness 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 spline tooth surface meet the necessary hardness requirements. The hardened spline shaft has better wear resistance and impact resistance, but the corresponding machining difficulty is also higher. To ensure the highest possible machining efficiency while minimizing machining errors, this application employs the following multi-stage grinding process to further process the spline, including rough grinding, semi-finish grinding, and finish grinding. Specifically:

[0050] C. Based on rolling distance error =3~4 The drive grinding assembly performs rough grinding on the spline blank, with a single grinding depth of 5-10 mm during rough grinding. First, start with a single infeed of 10. In rough grinding, the grinding amount is gradually reduced as the area to be ground on the spline tooth surface expands. Once the entire spline tooth surface can be ground, the single feed rate is increased to 5. Grind 2-3 times; during grinding, use a single-crystal diamond grinding wheel to dress the grinding wheel as needed, with a grinding depth of 20-40 mm. One work trip, with a repair speed of 1-2. ;

[0051] Specifically, to facilitate tool setting, when machining splined shafts, the grinding process begins from the tooth tip, driving the grinding assembly to roll towards the tooth root. Then, the direction is reversed, rolling towards the tooth tip until it disengages from the grinding wheel. This process is repeated after each feed until the entire spline tooth surface can be ground in a single pass. The grinding depth is then reduced, and the process is repeated until a single feed depth of 0.2 mm is achieved. The entire spline tooth surface can be ground, thus ending the grinding process;

[0052] In theory, feed rate refers to the depth to which the abrasive grains can cut into the workpiece. The exposed portion of the abrasive grains is the key factor affecting the feed rate. The size of the feed rate determines the depth of cut of the tool on the workpiece. Increasing the feed rate will increase the corresponding grinding depth. Although it can remove surface material faster, it will lead to tool overload, spline surface deformation due to stress, and decreased machining quality.

[0053] Through multiple comprehensive tests and analyses, this application divides the spline grinding process into several progressive stages: an initial rough grinding stage, a second stage of semi-finish grinding, and a fine grinding stage. After measurement and calibration, repeated fine grinding is performed. By rationally controlling the number of grinding passes and the feed rate, the stability of the microstructure during spline shaft machining is improved. This achieves a balance between high-efficiency grinding, product yield, and spline machining accuracy. The specific steps are as follows:

[0054] D. Based on rolling distance error =2 Semi-finish grinding, with a single grinding amount of approximately 1-3. During the grinding process, the grinding wheel is dressed using a single-crystal diamond dressing tool as needed, with a dressing depth of 20-40 mm. One work trip, with a repair speed of 1-2. ;

[0055] E. Perform aging treatment on the spline shaft, and then dress the grinding wheel again according to the rolling distance error. =2 Fine grinding, with a single grinding amount of approximately 0.5~1. During the grinding process, the grinding wheel is dressed using a single-crystal diamond dressing tool as needed, with a dressing depth of 5-10. 1-2 working strokes, 1-2 idle strokes, and a repair speed of 0.5-1. ;

[0056] F. After the entire spline tooth surface can be ground in a single feed, calculate the rolling distance error. =1 Single grinding amount: 0.2 In fine grinding, the grinding wheel is dressed using a single-crystal diamond dressing tool 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 is considered. =0 Single grinding amount: 0.2 Total grinding amount 0.5~1 For fine grinding, the machine should be preheated for more than 3 hours before each fine grinding to ensure sufficient thermal elongation of the grinding wheel spindle;

[0058] H. Stop feeding and drive the grinding assembly to reciprocate 4-8 times for finishing.

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

[0060] J. Measure the profile deviation of the spline tooth surface. If it meets the requirements for profile shape deviation within the measurement range, perform aging treatment on the gear involute template again and conduct a final measurement on the gear involute template. If it does not meet the requirements, correct the rolling distance error based on the involute profile at the tooth root. When the tooth root profile deviates towards the inside, adjust the rolling distance error accordingly. =-1~0 Single grinding amount: 0.2 Total grinding amount is approximately 0.5~1 Fine grinding and finishing; when the tooth root profile deviates outward, the rolling distance error is considered. =0~1 The same parameters are used for fine grinding and finishing, and then the measurement is repeated. If the requirements are met, aging treatment and final measurement are performed. If the requirements are not met, the above process is repeated.

[0061] like Figure 3 As shown, in the process of measuring the profile deviation of spline tooth surface, under ideal conditions, when measuring the involute of the tooth surface using the generating mechanism, the theoretical measuring point is in contact with the measured involute of the tooth surface in the plane. If the tooth surface involute is a standard involute, the probe will not move; otherwise, the probe will deviate along the generating line direction. This deviation is the profile deviation. When the deviation exists, the actual measuring point in contact between the probe and the measured involute will be distributed in a region on the probe.

[0062] Based on the above measurement principles, it is known that deviations in the measuring point position will cause deviations in the tooth profile measurement 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 measurement error of the tooth profile deviation caused by the measuring point position deviation; when the probe radius is infinitely large, i.e., becomes a plane, the measuring point position deviation will not cause measurement error, which is consistent with the generation principle of involute curves. However, the actual measuring chamber probe diameter is necessarily small. Therefore, this application proposes the following improved measurement scheme to enhance the accuracy of spline tooth profile deviation measurement, better determine the tooth profile deviation, and improve the accuracy after high-precision spline machining. Specifically, the following steps are included:

[0063] S1. Visually adjust the probe's measuring point to the upper side of the measuring plane, reducing the positional deviation of the measuring point. ; Measure the profile deviation of the tooth surface to be measured, and measure every 1 The unfolded length is set to 10-30 sampling points;

[0064] S2. Then move the probe 20-50 degrees along the normal direction of the measuring plane. Upon measurement again, the tooth profile deviation at the root gradually shifts outward and is compressed along the unfolded length;

[0065] S3. Continue to move the probe upwards, adjusting it by 20-50 degrees each time. Repeat the measurement until the tooth profile deviation near the tooth root (excluding the base circle) is biased inwards and compressed along the unfolded length. At this point, the measurement point position deviation is determined. ;

[0066] S4. Move the probe downwards by 50-100 degrees. Then adjust the probe's movement amount to 5~10 each time. 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 errors caused by the limitations of the measurement method and the structure of the measuring device itself. It achieves the cancellation of positive and negative errors through bidirectional fitting, which is beneficial for the measurement and correction of involute template tooth profile deviation. It can effectively reduce the influence of positive tooth tip radius and probe size deviation on the measurement results of involute tooth profile deviation, ensure accurate and effective measurement, and further improve the machining accuracy of splines.

[0068] This invention is mainly used for the processing and fabrication of high-precision splines and high-hardness, high-precision splines that are 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, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for high-precision machining of splines, characterized in that, Includes the following steps: A. Preheating gear rolling, leaving a allowance of 0.15, the initial diameter of the shaft blank is... ; in This refers to the number of teeth. It refers to the pitch circle diameter. This refers to the angular pressure at the pitch circle. This refers to the pressure angle of the tooth tip circle. This refers to the pressure angle of the tooth root circle. This refers to the tip circle diameter. This refers to the diameter of the tooth root circle. This refers to the thickness of the tooth tip arc. This refers to the thickness of the tooth root arc; B. Heat treatment; C. Based on rolling distance error =3~4 The drive grinding assembly performs rough grinding on the spline blank, with a single grinding amount of 5 during rough grinding. ~10 First, start with a single infeed of 10. In rough grinding, the grinding amount is gradually reduced as the area to be ground on the spline tooth surface expands. Once the entire spline tooth surface can be ground, the single feed rate is increased to 5. Grind 2-3 times; D. Based on rolling distance error =2 Semi-finish grinding, with a single grinding amount of approximately 1 ~3 ; E. Perform aging treatment on the spline shaft, and then dress the grinding wheel again according to the rolling distance error. =2 Fine grinding, with a single grinding amount of approximately 0.5~1. ; F. After the entire spline tooth surface can be ground in a single feed, calculate the rolling distance error. =1 Single grinding amount: 0.2 fine grinding; G. Before each fine grinding, the machine should be preheated for more than 3 hours to ensure sufficient thermal elongation of the grinding wheel spindle; H. Stop the feed and drive the grinding assembly to reciprocate 4-8 times for finishing. I. After finishing, keep warm at room temperature (20℃±0.5℃) for 12 hours; J. Measure the tooth profile deviation of the spline. If it meets the requirements for tooth profile shape deviation within the specified range, perform aging treatment on the spline shaft again and conduct a final measurement. If it does not meet the requirements, correct the rolling distance error based on the involute profile at the tooth root. When the tooth root profile deviates towards the inside of the shaft, adjust the rolling distance error accordingly. =-1~0 Single grinding amount: 0.2 Total grinding amount is approximately 0.

5. ~1 Fine grinding and finishing; when the tooth root profile deviates outward, the rolling distance error is considered. =0~1 The same parameters are used for fine grinding and finishing, and then the measurement is repeated. If the requirements are met, aging treatment and final measurement are performed. If the requirements are not met, the above process is repeated. The measurement of the spline tooth profile deviation is performed using the following steps: S1. Visually adjust the probe's measuring point to the upper side of the measuring plane, reducing the positional deviation of the measuring point. ; Measure the profile deviation of the tooth surface to be measured, and measure every 1 The unfolded length is set to 10-30 sampling points; S2. Then move the probe 20-50 degrees along the normal direction of the measuring plane. Upon measurement again, the tooth profile deviation at the root gradually shifts outward and is compressed along the unfolded length; S3. Continue to move the probe upwards, adjusting it by 20-50 degrees each time. Repeat the measurement until the tooth profile deviation near the tooth root (excluding the base circle) is biased inwards and compressed along the unfolded length. At this point, the measurement point position deviation is determined. ; S4. Move the probe downwards by 50-100 degrees. Then adjust the probe's movement amount to 5~10 each time. Repeat steps S1 to S3 several times to fit the deviation measurement results of different probe positions.

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, and the center pressure is... Gear forming pressure: .

3. The high-precision spline machining method according to claim 1, characterized in that, During the gear rolling process, the rotational speed of the shaft blank remains constant, and the circumferential speed of the shaft blank is 8~10. During the tooth rolling process, ensure that the tooth rolling plate is lubricated by forced oil mist.

4. The high-precision spline machining method according to claim 1, characterized in that, When machining a splined shaft, the grinding process begins at the tooth tip, driving the grinding assembly to roll towards the tooth root. Then, the direction is reversed, and the assembly rolls towards the tooth tip until it disengages from the grinding wheel. This process is repeated after each infeed until the entire spline tooth surface can be ground in a single pass. The grinding depth is then reduced, and the process is repeated until the depth of cut is 0.2 mm. The entire spline tooth surface can be ground, thus ending the grinding process; The heat treatment in step B is carried out in a continuous carburizing furnace and includes the following steps in sequence: B1. Strong infiltration treatment: Maintain 1.0% carbon potential, and heat evenly for 65~80 degrees Celsius. Perform 90-150 minutes at 850℃~900℃. ; B2. Diffusion treatment: Maintain carbon potential at 0.76%, uniformly reduce temperature to 850~880℃; maintain carbon potential at 0.86%, hold at a constant temperature of 45℃. minute; B3. Quenching and heat preservation treatment: Maintain carbon potential at 0.76%, uniformly cool to 820℃~835℃ and hold for 50~60 minutes. ; B4. Oil cooling treatment.

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