A thread rolling method based on a numerically controlled lathe

Abstract

The present invention discloses a thread rolling method based on a numerically controlled lathe, comprising: S1. Thread tool setting: First, move the hob to one side of the thread section, and set the Z-axis coordinate of the tool starting point during machining; then move the hob along the Z-axis by an integer multiple of the pitch; then rotate the workpiece and move the hob along the X-axis so that the thread groove can face the hob directly. The hob enters the thread groove and contacts the tooth root. At this time, set the X-axis coordinate of the tool starting point, and set the current angle of the main shaft as the machining starting angle; S2. Move the hob to the tool starting point; S3. Execute the machining program to start thread rolling. When rotating the workpiece, the moving distance of the thread groove on the Z-axis is shorter, which is convenient for control and adjustment. Compared with moving the hob on the Z-axis, it is more accurate and convenient. After aligning the thread groove at this position, the requirement for the position of the tool starting point is lower, improving the tool setting accuracy. During machining, the hob can smoothly roll along the thread to the tooth root, realizing thread rolling on a numerically controlled machine tool and reducing the machining risk.

Description

Technical Field

[0001] The present invention relates to the field of machining technology, and particularly relates to a thread rolling method based on a numerically controlled lathe. Background Art

[0002] After machining long shaft threads (such as hydraulic press tie rods) using numerically controlled horizontal lathe equipment, due to the fact that the turning tool cannot meet the machining requirements at the bottom of the thread or there are machining accuracy issues, there are right angles or large roughness at the bottom of the thread, resulting in stress concentration and easy fracture when stressed. Therefore, it is necessary to roll the bottom of the thread, and the surface metal of the rolled part undergoes plastic deformation. After rolling the bottom of the thread, the bottom of the thread becomes rounded, the roughness is reduced, the stress at the bottom of the thread is decreased, the stress on the thread section is improved, and the hardness and strength of the part are increased.

[0003] Currently, when rolling the bottom of the thread, ordinary lathes are mostly used for manual rolling. This method is relatively simple and easy to adjust during the machining process. However, manual operation is prone to misoperation and damage, relies heavily on manual experience, and it is difficult to ensure consistent production quality.

[0004] Although numerically controlled lathes are for automated machining and can be processed according to the preset machining program as long as the machining starts, reducing manual operation and achieving relatively unified production quality. However, since the numerically controlled lathe cannot stop midway after executing the machining program and needs to complete the machining before stopping, and rolling machining is different from cutting machining, the requirements for thread rolling machining are relatively high. If the rolling method is incorrect, it will damage the part and the tool, and even damage the numerically controlled lathe, posing a greater risk. Therefore, numerically controlled lathes are rarely used for thread rolling in the current industry. Those skilled in the art hope to have a thread rolling method based on a numerically controlled lathe that can achieve automatic rolling machining and reduce machining risks. Summary of the Invention

[0005] The main objective of the present invention is to propose a thread rolling method based on a numerically controlled lathe, aiming to solve the technical problems in the prior art that when thread rolling is performed using an ordinary machine tool with manual operation, it is prone to misoperation, difficult to ensure consistent production quality, and when using a numerically controlled lathe, the machining risk is relatively high.

[0006] To achieve the above objective, the present invention proposes a thread rolling method based on a numerically controlled lathe, including:

[0007] S1. Thread tool alignment:

[0008] 1) Move the hobbing cutter to the outside of the thread section to be rolled in the Z-axis direction, and set the Z-axis position of the current hobbing cutter as the Z-axis coordinate of the tool starting point;

[0009] 2) Move the hobbing cutter along the Z-axis into the outside of the thread section in the X-axis direction, and the moving distance along the Z-axis is an integer multiple of the thread pitch;

[0010] 3) Rotate the workpiece and move the hob along the X-axis towards the thread simultaneously to align the thread groove with the hob, and make the hob enter the thread groove and contact the root of the tooth to be rolled;

[0011] 4) Set the X-axis position of the current hob as the X-axis coordinate of the tool starting point, and set the angle of the current spindle as the starting angle for workpiece machining;

[0012] S2. Move the hob to the tool starting point;

[0013] S3. Execute the machining program to start the rolling process. While the workpiece is rotating, the hob moves along the Z-axis in a matching manner, so that the hob rolls along the root of the thread until the machining is completed.

[0014] Before machining on the numerical control machine tool, align the hob with the thread section of the workpiece to be rolled, so that the hob can move accurately in the thread groove during machining.

[0015] The tool alignment step of the present invention is to first move the hob to one side of the thread section and set it as the Z-axis coordinate of the tool starting point during machining; then move the hob along the Z-axis by an integer multiple of the pitch, and do not move the hob along the Z-axis during the tool alignment process; then rotate the workpiece and move the hob along the X-axis to align the thread groove with the hob. The hob enters the thread groove and contacts the root of the tooth. At this time, set the X-axis coordinate of the tool starting point, and set the current angle of the spindle as the starting angle for machining.

[0016] The tool alignment method of the present invention no longer moves the hob along the Z-axis after moving the hob from the tool starting point to a position that is a multiple of the pitch. Rotate the workpiece and adjust the position of the thread groove to fit the hob. When rotating the workpiece, the moving distance of the thread groove along the Z-axis is short, which is convenient for control and adjustment. Rotating the workpiece is more accurate and convenient than moving the hob along the Z-axis, reducing the damage to the thread caused by excessive movement of the hob along the Z-axis when the hob is in the thread groove; since the moving distance of the hob from the tool starting point is an integer multiple of the pitch, when the thread groove is aligned at this position, the hob can enter the thread groove during machining, and the requirement for the position of the tool starting point is relatively low. It is not necessary to align the tool with the end of the thread section, realizing convenient tool alignment between the hob and the thread on the numerical control machine tool, improving the tool alignment accuracy. When accurate tool alignment is achieved, execute the machining program to start the rolling process, and the hob can smoothly roll along the root of the thread, realizing the rolling of the thread on the numerical control machine tool and reducing the machining risk.

[0017] Preferably, the tool starting point is located in the relief groove of the thread section during thread cutting machining of the workpiece, and the thread section is transitioned to the relief groove through a transition inclined surface;

[0018] In step S3, the rotation direction of the workpiece is opposite to the rotation direction of the workpiece during thread cutting machining, and the hob moves from one side of the relief groove towards the thread section.

[0019] The starting point of the cutting tool is located in the relief groove of the thread section. There is a transition inclined plane between the thread section and the relief groove. The end of the thread is on the transition inclined plane. In this way, there is an inclined plane transition from the transition inclined plane to the root of the thread at the end of the thread. Moreover, the crest of the thread part on the transition inclined plane will incline along with the transition inclined plane, that is, the depth from the crest to the root of the thread on the transition inclined plane gradually becomes shallower, and the cross-sectional size of the thread groove gradually becomes smaller in the direction close to the relief groove.

[0020] When the hob approaches the thread section from one side of the relief groove, the hob first passes through the transition inclined plane and gradually approaches the root of the thread groove, gradually increasing the contact and pressure with the root. Moreover, the cross-sectional size of the thread groove gradually becomes larger. When the hob just enters the thread groove, the thread heights on both sides of the thread groove are very small, and the hob can easily enter the thread groove, so as to reduce or avoid the direct collision between the hob and the root or the thread when the hob just enters the thread groove, making the processing smoother and further reducing the risk of rolling threads on the CNC lathe.

[0021] Preferably, in step S3, while the hob moves along the Z-axis, it inclines and moves away from the thread section along the X-axis.

[0022] During the hob process, the bearings connecting the hob and the bearings of the main shaft are under great pressure and heat up. After long-term use, the bearings may be burned out, or the main shaft may be overloaded and the alarm stops due to excessive force, affecting the processing and even causing equipment failures.

[0023] Therefore, the present invention sets the hob to move away from the thread section along the X-axis during the processing, that is, the hob inclines outward during the movement along the Z-axis to gradually reduce the rolling depth and finally move away from the root. In this way, the rolling process of the hob on the thread section is for a section close to the relief groove, rather than the entire thread section, which can shorten the processing time, and the rolling pressure during the processing also shows a decreasing trend as a whole. Since the main stress position of the thread section is in a section close to the relief groove, the bearing time and pressure of the hob and the main shaft are reduced, further reducing the risk of rolling threads on the CNC lathe.

[0024] Preferably, when the hob moves, the inclination angle α with respect to the X-axis is 0°015' to 0°025'.

[0025] Preferably, in the step S3, the hob feeds multiple times to the required rolling depth, and can be rolled to the required depth multiple times to reduce the pressure of each rolling and reduce the load of the CNC lathe.

[0026] Preferably, the hob includes a rolling seat and a rolling wheel rotatably connected to the rolling seat. There is a swing gap between the rolling wheel and the rolling seat for the rolling wheel to swing to adapt to the thread groove during the rolling process.

[0027] Preferably, the cross-sectional angle of the cutter part of the hob is smaller than the angle of the thread groove, so as to reduce or prevent the contact between the side surface of the hob and the side surface of the thread tooth and damage the thread. Brief Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following-described drawings are only some embodiments of the present invention. For those skilled in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0029] Figure 1 It is a schematic structural diagram of the thread rolling method of the present invention;

[0030] Figure 2 It is a schematic cross-sectional structure diagram when the hob of the present invention extends into the thread groove;

[0031] Figure 3 It is a schematic structural diagram of another angle of the thread rolling method of the present invention;

[0032] Figure 4 It is a schematic cross-sectional diagram when the thread groove is processed on the side close to the end face along the extending direction;

[0033] Figure 5 It is a schematic cross-sectional diagram when the thread groove of the present invention is processed on the side close to the relief groove along the extending direction.

[0034] In the drawings: 1 - workpiece, 11 - thread section, 111 - thread groove, 12 - relief groove, 13 - transition inclined surface, 2 - hob.

[0035] The realization of the object, functional features and advantages of the present invention will be further described with reference to the embodiments and the drawings. Detailed Embodiments

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0037] It should be noted that if there are directional indications in the embodiments of the present invention, such as up, down, left, right, front, back, etc., the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0038] In addition, if there are descriptions such as "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments may be combined with each other, but it must be based on the fact that those skilled in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0039] As Figures 1 to 5 shown, a thread rolling method based on a numerically controlled lathe includes:

[0040] S1. Thread tool setting:

[0041] 1) The main shaft of the numerically controlled lathe holds the workpiece 1, moves the hob 2 to the outside of the thread section 11 to be rolled in the Z-axis direction, and sets the Z-axis coordinate of the current position of the hob 2 as the Z-axis coordinate of the tool starting point; the position of the hob 2 in the Y-axis direction is basically flush with the axis of the workpiece 1, and sets the Y-axis coordinate of the current position of the hob 2 as the Y-axis coordinate of the tool starting point;

[0042] 2) Move the hob 2 along the Z-axis into the outside of the thread section 11 in the X-axis direction. The hob 2 does not collide with the thread section 11 during the movement. The moving distance along the Z-axis is an integer multiple n*L of the thread pitch L, referring to Figure 3 ;

[0043] 3) Loosen the main shaft rotation lock, and the operator manually rotates the workpiece 1. The workpiece 1 rotates along the main shaft S-axis. At the same time, use the handwheel to move the hob 2 along the X-axis closer to the thread, so that the thread groove 111 is directly opposite to the hob 2, and the operator judges that the hob 2 enters the thread groove 111 and contacts the bottom of the tooth to be rolled;

[0044] 4) Set the X-axis coordinate of the current position of the hob 2 as the X-axis coordinate of the tool starting point, and set the angle of the current main shaft as the machining starting angle of the workpiece 1;

[0045] S2. Move the hob 2 to the tool starting point;

[0046] S3. Execute the machining program to start rolling machining. While the workpiece 1 rotates, the hob 2 moves along the Z-axis in a matching manner, so that the hob 2 rolls along the thread bottom until the machining is completed.

[0047] Before machining on the numerically controlled machine tool, first set the tool of the hob 2 and the thread section 11 of the workpiece 1 to be rolled, so that the hob 2 can accurately move in the thread groove 111 during the machining process.

[0048] The tool setting steps of the present invention are as follows: First, move the hob 2 to one side of the threaded section 11 to set the Z-axis coordinate of the tool starting point during machining; then move the hob 2 along the Z-axis by an integer multiple of the pitch, and do not move the hob 2 along the Z-axis during the tool setting process; next, manually rotate the workpiece 1 and move the hob 2 along the X-axis so that the thread groove 111 can face the hob 2 directly. The hob 2 enters the thread groove 111 and contacts the tooth root. At this time, set the X-axis coordinate of the tool starting point, and set the current angle of the main shaft as the machining starting angle, that is, change the original machining starting angle of the main shaft for the workpiece.

[0049] The tool setting method of the present invention no longer moves the hob 2 along the Z-axis after moving the hob 2 from the tool starting point to a position that is an integer multiple of the pitch. Manually rotate the workpiece 1 and adapt the thread groove 111 to the position of the hob 2. When rotating the workpiece 1, the moving distance of the thread groove 111 along the Z-axis is short, which is convenient for control and adjustment. Rotating the workpiece 1 is more accurate and convenient than moving the hob 2 along the Z-axis, and reduces the damage to the thread caused by excessive movement of the hob 2 along the Z-axis when the hob 2 is in the thread groove 111.

[0050] Since the moving distance of the hob 2 from the tool starting point is an integer multiple of the pitch, when the thread groove 111 is set at this position, the hob 2 can enter the thread groove 111 during machining. The requirement for the position of the tool starting point is relatively low, and it is not necessary to align the tool with the end of the threaded section 11. It is convenient to align the hob 2 with the thread on the numerical control machine, improving the tool setting accuracy. After achieving precise tool setting, execute the machining program to start the rolling process. The hob 2 can smoothly roll along the thread to the tooth root, realizing the rolling of the thread on the numerical control machine and reducing the machining risk.

[0051] In some specific embodiments, the tool starting point is located in the relief groove 12 of the threaded section 11 during thread cutting machining of the threaded section 11, and the threaded section 11 is transitioned to the relief groove 12 through a transition inclined surface 13;

[0052] In step S3, the rotation direction of the workpiece 1 is opposite to the rotation direction of the workpiece 1 during thread cutting machining, and the hob 2 moves from one side of the relief groove 12 to the threaded section 11.

[0053] During the cutting machining of the threaded section 11, a relief groove 12 is provided on the workpiece 1 for the cutting tool to retract.

[0054] The tool starting point is located in the relief groove 12 of the threaded section 11. The diameter of the relief groove 12 is smaller than the diameter of the tooth root of the thread. There is a transition inclined surface 13 between the threaded section 11 and the relief groove 12, and the end of the thread is on the transition inclined surface 13. Thus, there is an inclined surface transition from the transition inclined surface 13 to the tooth root at the end of the thread. Moreover, the tooth crest of the thread part on the transition inclined surface 13 will be inclined along with the transition inclined surface 13, that is, the depth from the tooth crest to the tooth root on the transition inclined surface 13 gradually becomes shallower, and the cross-sectional size of the thread groove 111 gradually becomes smaller in the direction close to the relief groove 12. Refer to Figure 3 andFigure 5 。

[0055] When the hob 2 approaches the threaded section 11 from one side of the relief groove 12, the hob 2 first passes through the transition inclined surface 13 and gradually approaches the bottom of the thread groove 111, gradually increasing the contact and pressure with the bottom. Moreover, the cross-sectional size of the thread groove 111 gradually becomes larger. When the hob 2 just enters the thread groove 111, the thread heights on both sides of the thread groove 111 are very small, and the hob 2 can easily enter the thread groove 111. Refer to Figure 5 , Figure 5 which shows a schematic cross-sectional view of the thread groove 111 along the extension direction near the side of the relief groove 12. If rolling starts from the starting side of the cutting process of the threaded section 11 and this side is the end face, refer to Figure 4 , Figure 4 which shows a schematic cross-sectional view of the thread groove 111 along the extension direction near the side of the end face. The height of the bottom of the tooth may be too high, and the hob 2 may directly collide with the bottom of the tooth. The pressure is very high when first contacting. In addition, there is no chamfer or the chamfer is very small at the end of the threaded section 11 on this side, and the thread heights on both sides of the thread groove 111 are relatively high. The hob 2 needs to directly enter between the two side threads. The position of the hob 2 and the thread groove 111 needs to be very precise to enter, otherwise it is easy to cause tool collision and damage to the thread and the equipment. This solution can reduce or avoid the direct collision of the hob 2 with the bottom of the tooth or the side threads when just entering the thread groove 111, make the processing smoother, and further reduce the risk of rolling threads on the CNC lathe.

[0056] In some specific embodiments, in step S3, while the hob 2 moves along the Z-axis, it moves obliquely along the X-axis in a direction away from the threaded section 11.

[0057] During the process of the hob 2, the bearings connecting the hob 2 and the bearings of the main shaft are under relatively large pressure and heat up. After long-term use, the bearings may be burned out, or the main shaft may be overloaded due to excessive force and an overload alarm may stop the machine, affecting the processing and even causing equipment failure.

[0058] Therefore, the present invention sets the hob 2 to move away from the threaded section 11 along the X-axis during the processing, that is, the hob 2 inclines outwards during the movement along the Z-axis, as shown in Figure 1 forming an angle α, gradually reducing the rolling depth, and finally moving away from the bottom of the tooth. In this way, the rolling process of the hob 2 on the threaded section 11 is for a section close to the relief groove 12, rather than the entire threaded section 11. Refer to Figure 1The medium length M is the actual rolling length, which can shorten the processing time. Moreover, the rolling pressure as a whole shows a decreasing trend during the processing. When the threaded section 11 of the workpiece 1 is stressed in cooperation with the nut, the nut is mainly connected to the side of the threaded section 11 close to the tool withdrawal groove 12, that is, the main stress position of the threaded section 11 is in a section close to the tool withdrawal groove 12. Therefore, only rolling a section close to the tool withdrawal groove 12 does not affect the normal use of the workpiece 1, thereby reducing the bearing time and pressure of the hob 2 and the main shaft, and further reducing the risk of rolling threads on the CNC lathe.

[0059] Further, the inclination angle α of the hob when moving with respect to the X-axis is 0°015' to 0°025'. Within this inclination angle range, a section of the threaded section close to the tool withdrawal groove can be rolled. Preferably, the inclination angle α is 0°02'.

[0060] In some specific embodiments, in step S3, the hob 2 feeds multiple times to the depth required for rolling, and can be rolled to the required depth multiple times, reducing the pressure for each rolling and reducing the load on the CNC lathe.

[0061] Further, the multiple-feed machining can be: when rolling the first to the fourth cut, each time increase by 0.1 mm, gradually making the hob penetrate to the required depth; when rolling the fifth cut and above, such as the fifth to the tenth cut, do not increase the depth of the hob, and the hob runs empty according to the depth of the fourth cut to trim the bottom of the entire thread at this depth.

[0062] In some specific embodiments, the hob 2 includes a rolling seat and a rolling wheel rotatably connected to the rolling seat. There is a swinging gap between the rolling wheel and the rolling seat for the rolling wheel to swing to adapt to the thread groove 111 during rolling, reducing damage to the thread teeth caused by machining errors. Since there is a swinging gap between the rolling wheel and the rolling seat, higher requirements for the fitting accuracy when the rolling wheel enters the thread groove 111 after the CNC lathe starts machining are required. Through the tool setting method of the present invention, and reducing the position accuracy requirements when entering from one side of the tool withdrawal groove 12, the hob 2 can enter the thread groove 111 more accurately.

[0063] In some specific embodiments, the cross-sectional angle b of the cutting part of the hob 2 is smaller than the angle c of the thread groove 111, referring to Figure 2 , so as to reduce or prevent the side surface of the hob 2 from contacting the side surface of the thread tooth and damaging the thread. Specifically, it can be: a 55-degree rolling wheel is used for a 60-degree triangular thread, and for a 45-degree serrated thread, the hypotenuse is 50 degrees and the straight side is changed to 89 degrees.

[0064] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A thread rolling method based on a numerically controlled lathe, characterized in that, it includes the following steps: S1. Thread tool setting: 1) Move the hob (2) to the outside of the thread section (11) to be rolled in the Z-axis direction, and set the Z-axis position of the current hob (2) as the Z-axis coordinate of the tool starting point; 2) Move the hob (2) along the Z-axis into the outside of the thread section (11) in the X-axis direction, and the moving distance along the Z-axis is an integer multiple of the thread pitch; 3) Rotate the workpiece (1), and at the same time move the hob (2) along the X-axis closer to the thread, so that the thread groove (111) is directly opposite to the hob (2), and the hob (2) enters the thread groove (111) and contacts the bottom of the tooth to be rolled; 4) Set the X-axis position of the current hob (2) as the X-axis coordinate of the tool starting point, and set the angle of the current main shaft as the machining starting angle of the workpiece (1); S2. Move the hob (2) to the tool starting point; S3. Execute the machining program to start rolling processing. While the workpiece (1) is rotating, the hob (2) moves matchingly along the Z-axis, so that the hob (2) rolls along the bottom of the thread until the processing is completed.

2. The thread rolling method according to claim 1, characterized in that, the tool starting point is located in the relief groove (12) during the thread cutting process of the thread section (11), and the thread section (11) is transitioned to the relief groove (12) through a transition inclined surface (13); In step S3, the rotation direction of the workpiece (1) is opposite to the rotation direction of the workpiece (1) during the thread cutting process, and the hob (2) moves from one side of the relief groove (12) to the thread section (11).

3. The thread rolling method according to claim 2, characterized in that, In step S3, while the hob (2) is moving along the Z-axis, it moves obliquely along the X-axis away from the thread section (11).

4. The thread rolling method according to claim 3, characterized in that, the inclination angle α of the hob when moving to the X-axis is 0°015' - 0°025'.

5. The thread rolling method according to claim 1, characterized in that, in the step S3, the hob (2) is fed in multiple times to the depth to be rolled.

6. The thread rolling method according to claim 1, characterized in that, the hob (2) includes a rolling seat and a rolling wheel rotatably connected to the rolling seat, and there is a swinging gap between the rolling wheel and the rolling seat for the rolling wheel to swing to adapt to the thread groove (111) during the rolling process.

7. The thread rolling method according to claim 1, characterized in that, the cross-sectional angle of the cutting part of the hob (2) is smaller than the angle of the thread groove (111).

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