A screw stress relief heat treatment straightening device and method

Abstract

The application discloses a kind of screw stress relief heat treatment straightening device and method, belong to the technical field of slender rod processing process technology.The application is preloaded to the deformed position of screw using tool, and the stress value of the deformed position of screw is higher than the yield strength of material under heat treatment temperature by calculating and analyzing elastically-plastic theory, then the tool is put into heating furnace together with screw to carry out heat treatment, at this time, the screw produces slight plastic deformation and can be controlled within the preset deformation threshold range, and can be treated multiple times until the required straightening deformation amount is reached.The problem that the existing technology exists in the machining process of screw, which has reached the finished product size requirement, but still has deformation, and the surface hardness is very high, and machining cannot be used to modify the deformation.

Description

Technical Field

[0001] This invention relates to the field of slender rod processing technology, and in particular to a stress-relieving heat treatment and straightening device and method for lead screws. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Lead screws are the most commonly used transmission components in machine tools and precision machinery. Their main function is to convert rotary motion into linear motion or torque into axial reciprocating force. Lead screws are key functional components of CNC machine tools, and their accuracy directly affects the accuracy of the entire machine. Because lead screws are slender rod-shaped parts and are flexible components with poor rigidity, they are prone to deformation, resulting in machining errors such as straightness and cylindricity. Therefore, after machining, lead screws usually need to be straightened.

[0004] Traditional ball screw straightening involves using a dial indicator to detect the deviation at a certain point, followed by straightening with a hydraulic cylinder. However, during the downward movement of the hydraulic cylinder, the vertical position of the ball screw may change, causing the dial indicator to misrepresent the deviation and resulting in inaccurate straightening.

[0005] Chinese patent CN208213980U discloses a ball screw straightening machine, indicating that existing ball screw straightening typically requires workers to visually determine the bending position of the ball screw using a dial indicator, and then manually place the ball screw on a fixed support to be straightened by a straightening machine. The problem with this is that the quality of the ball screw depends entirely on the operator's skill level, affecting the screw's accuracy and stability.

[0006] Chinese patent CN213856433U describes a titanium rod straightening device that uses a heating wire to heat the rod, followed by the use of a counterweight to pull and straighten it. Depending on the rod's thickness, heating is applied for 3-6 seconds, after which the rod is automatically straightened under the traction of the counterweight. While the method is simple in principle, its deformation straightening control is poor.

[0007] Chinese patent CN115815375B discloses a lead screw straightening device and method. A nut equipped with strain gauges is fitted onto the lead screw to be straightened. When the nut moves from one end of the lead screw to the other, the deformation is transmitted to the nut through the deformation area of ​​the lead screw. The strain gauges receive the deformation signal from the nut and convert it into the deformation trajectory of the lead screw, thereby determining the maximum deformation position and maximum deformation amount. Pressure and vibration are then applied for straightening. This process is repeated through multiple cycles of measurement until the maximum deformation of the lead screw is less than a deformation threshold. This method is a cold straightening method, suitable for materials with low yield strength. However, the internal stress generated during cold working is not released, posing a risk of deformation rebound after straightening.

[0008] Chinese patent CN101704038A discloses a method for straightening crankshafts by tapping the rounded corners. This method releases internal stress in the deformed structure by tapping the rounded corners, eliminating bending deformation. The method involves placing a flat chisel, whose head matches the crankshaft's rounded corner, on the corner of the crankshaft at the critical section. A hammer is used to repeatedly tap the rounded corner while rotating it, monitoring the amount of deformation. By releasing internal stress through the deformed rounded corner, the crankshaft's deformation is restored. Crankshafts straightened using this method are less prone to rebound deformation, but the process is labor-intensive and requires the operator to have considerable practical experience. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the purpose of this invention is to provide a stress-relieving heat treatment straightening device and method for lead screws, in order to solve the problem that the lead screws have reached the required finished dimensions during the machining process, but still have deformation and high surface hardness, making it impossible to use machining to correct the deformation.

[0010] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0011] A lead screw stress relief heat treatment straightening device includes a tooling cylinder, wherein the tooling cylinder is hollow.

[0012] A number of straightening units are provided around the circumference of the tooling cylinder. The straightening units are evenly distributed along the length of the tooling cylinder and are oriented in the same direction. Each straightening unit includes a clamping screw and a locking nut. One end of the clamping screw passes through the locking nut and extends into the tooling cylinder. The insertion depth of the clamping screw is adjustable so that the deformation of the lead screw is controllable.

[0013] The number of clamping screws is three or more, and they are evenly distributed along the circumference of the tooling cylinder and located in the same cross-section;

[0014] The lead screw is placed in the tooling cylinder, and one end of the clamping screw contacts the deformed part of the lead screw so that the lead screw deforms in the opposite direction to the original deformation direction. The lead screw and the tooling cylinder are heated simultaneously until the required straightening deformation is achieved.

[0015] Furthermore, the tooling cylinder is provided with lead screw through holes at both the top and bottom;

[0016] The tooling cylinder is provided with lifting bolts on its circumferential side, and the lifting bolts are located at one end of the tooling cylinder along its length; the tooling cylinder is provided with limit screws on its circumferential side, and the limit screws are located at the other end of the tooling cylinder along its length.

[0017] Furthermore, the cross-sectional area of ​​the tooling cylinder is larger than the cross-sectional area of ​​the lead screw.

[0018] Furthermore, a measuring reference surface is provided on the surface of the tooling cylinder. The measuring reference surface is located at the installation location of the clamping screw and is parallel to the central axis of the tooling cylinder. The measuring reference surface is perpendicular to the clamping screw.

[0019] This invention also provides a method for stress-relieving heat treatment and straightening of a lead screw based on the above-mentioned lead screw stress-relieving heat treatment and straightening device, comprising the following steps:

[0020] S1. Place the lead screw in the tooling cylinder, and screw the clamping screw through the lock nut into the tooling cylinder until the end of the clamping screw presses against the lead screw; adjust the screwing depth of the clamping screw located at the deformed part of the lead screw so that the lead screw deforms in the opposite direction to the original deformation, and tighten the lock nut.

[0021] S2. The tooling cylinder connecting screw is hoisted and placed vertically in the heating furnace for stress relief heat treatment, so that the screw will undergo slight plastic deformation.

[0022] Repeat the above steps until the accumulated micro-plastic deformation reaches the required amount of straightening deformation.

[0023] Furthermore, S1 also includes:

[0024] The stress values ​​of the deformed parts of the lead screw under applied deformation are calculated using the elastic-plastic deformation theory.

[0025] The direction of the applied deformation is opposite to the original deformation direction, and the stress value is higher than the yield strength of the lead screw material at the stress relief heat treatment temperature.

[0026] Furthermore, before tightening the clamping screws and lock nuts, the following steps are also included:

[0027] Apply a high-temperature resistant, non-stick lubricating material to the surfaces of the clamping screws and locking nuts.

[0028] Furthermore, the minute plastic deformation is controlled within a deformation threshold range, wherein the deformation threshold range is preset.

[0029] Furthermore, the screwing depth of the clamping screw located at the deformation part of the lead screw is adjusted based on the measurement reference plane and according to the amount of minute plastic deformation.

[0030] Furthermore, S1 also includes:

[0031] After placing the lead screw in the tooling cylinder, screw the limit screw into the tooling cylinder so that the lead screw is above the limit screw to prevent the lead screw from falling off.

[0032] The technical solution provided by this invention has at least the following technical effects or advantages:

[0033] 1. The technical solution provided by this invention addresses the problem of lead screws deforming during processing but already meeting the required finished dimensions and having very high surface hardness, making machining impossible for fine repair. It employs tooling to preload the deformed portion of the lead screw. Through elastoplastic theory calculations, the stress value at the deformed portion is slightly higher than the material's yield strength at heat treatment temperature, but much lower than its yield strength at room temperature. This reduces the loading force and deformation, preventing overload damage to the lead screw. This process can be repeated multiple times until the required straightening deformation is achieved.

[0034] 2. The technical solution provided by this invention has a bending cross section of the tooling cylinder that is much larger than that of the lead screw, and has great rigidity. The deformation caused by tightening the screw to press the lead screw is also much smaller than the deformation of the lead screw, which can effectively play the role of straightening the tooling.

[0035] 3. The technical solution provided by the present invention involves heat treatment of the lead screw. Heat treatment can reduce the residual stress in the lead screw, redistribute it to a more uniform degree, and enhance the deformation resistance of the metal matrix, thereby improving the geometric accuracy and stability of the lead screw. Attached Figure Description

[0036] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0037] Figure 1 This is a schematic diagram of the structure of the lead screw stress relief heat treatment straightening device provided in an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the lead screw stress relief heat treatment straightening device provided in an embodiment of the present invention;

[0039] In the diagram: 1. Lifting bolt; 2. Clamping screw; 3. Locking nut; 4. Tooling cylinder; 5. Lead screw; 6. Limit screw.

[0040] The distances or dimensions between parts have been exaggerated to show their positions; the diagram is for illustrative purposes only. Detailed Implementation

[0041] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0042] Example 1

[0043] As described in the background section, the lead screw 5 deforms during the machining process, but has already reached the required finished size and has a very high surface hardness, making it impossible to perform fine finishing by machining. In order to solve the above technical problems, this invention proposes a lead screw stress relief heat treatment straightening device.

[0044] like Figures 1-2 As shown in the figure, this embodiment describes a lead screw stress relief heat treatment straightening device, including a tooling cylinder 4, which is hollow and used to place the lead screw 5.

[0045] A straightening unit is installed on the circumferential side of the tooling cylinder 4. There are multiple straightening units, and the straightening units are evenly distributed along the length direction of the tooling cylinder 4 and are installed in the same position and direction. Screw holes are evenly spaced along the length direction on the circumferential side of the tooling cylinder 4. Screw holes are evenly distributed along the circumferential direction of the tooling cylinder 4 on the same cross section. The straightening unit includes a clamping screw 2 and a locking nut 3. One end of the clamping screw 2 passes through the locking nut 3 and the screw hole and extends into the tooling cylinder 4. There are three clamping screws 2, which are evenly distributed along the circumferential direction of the tooling cylinder 4 and are located on the same cross section.

[0046] The tooling cylinder 4 has lead screw through holes at both the top and bottom to facilitate the placement of the lead screw 5 inside the tooling cylinder 4; a lifting bolt 1 is installed around the circumference of the tooling cylinder 4, with the lifting bolt 1 located near the top at one end of the tooling cylinder 4 along its length, allowing the tooling cylinder 4 and the lead screw 5 to be placed vertically inside the heating furnace; a limit screw 6 is installed around the circumference of the tooling cylinder 4, located at the other end of the tooling cylinder 4 along its length, with one end of the lead screw 5 entering the tooling cylinder 4 through the lead screw through hole at the top of the tooling cylinder 4 and positioned on the limit screw 6, which prevents the lead screw 5 from slipping off.

[0047] The tooling cylinder 4 has a measuring reference surface machined on its surface. The measuring reference surface is located at the mounting location of the clamping screw 2 and is parallel to the central axis of the tooling cylinder 4. The measuring reference surface is perpendicular to the clamping screw 2. The screwing depth of the clamping screw 2 can be measured through the measuring reference surface, thereby controlling the direction, position, and magnitude of the deformation of the lead screw 5.

[0048] The cross-sectional area of ​​the tooling cylinder 4 is much larger than that of the lead screw 5, making the bending modulus of the tooling cylinder 4 50 times that of the lead screw 5.

[0049] In use, the lead screw 5 is placed inside the tooling cylinder 4 through the lead screw through hole. The lead screw 5 is tightened by the combination of multiple sets of locking screws (straightening unit) set on the tooling. At the deformed part of the lead screw, the screw loading depth can be adjusted based on the measurement reference plane to make the lead screw 5 deform in the opposite direction to the original deformation direction. Then, the lead screw 5 and the tooling cylinder 4 are placed vertically in the heating furnace by the lifting bolt 1 and heated together. The lead screw 5 produces a small plastic deformation, which can be controlled within the preset deformation threshold range. The process can be repeated until the required straightening deformation amount is achieved.

[0050] Example 2

[0051] This embodiment provides a stress-relieving heat treatment and straightening method for lead screw 5 based on the lead screw stress-relieving heat treatment and straightening device described in Embodiment 1, including the following steps:

[0052] S1. Place the lead screw 5 on the tooling cylinder 4, and screw the limit screw 6 into the tooling cylinder 4 so that the lead screw 5 is above the limit screw 6 to prevent the lead screw 5 from falling off; screw one end of the clamping screw 2 into the tooling cylinder 4, and clamp the lead screw 5 with one end of the clamping screw 2 to limit the position of the lead screw 5; adjust the screwing depth of the clamping screw 2 located at the deformed part of the lead screw so that the lead screw 5 deforms in the opposite direction to the original deformation, and tighten the lock nut 3.

[0053] Specifically, based on the screwing depth of the clamping screw 2 and the structure of the lead screw 5, the stress value of the deformed part of the lead screw under applied deformation is calculated by the elastic-plastic deformation theory, and the deformation amount of the lead screw 5 is determined; the direction of applied deformation is opposite to the original deformation direction, and the stress value is higher than the yield strength of the lead screw 5 material at the stress relief heat treatment temperature.

[0054] The deformation part of the lead screw is preloaded by clamping screw 2. According to the calculation and analysis of elastic-plastic theory, the stress value of the deformation part of the lead screw should be slightly higher than the yield strength of the material at the stress relief heat treatment temperature, but lower than the yield strength of the material at room temperature. This reduces the loading force requirement and reduces the risk of breakage of lead screw 5.

[0055] Furthermore, before tightening the clamping screw 2 and the locking nut 3, apply a coating to the surface of the clamping screw 2 and the locking nut 3 to prevent the threaded connection from seizing at high temperatures, so that the clamping screw 2 and the locking nut can be repeatedly disassembled and used.

[0056] In this embodiment, the high-temperature resistant anti-sticking lubricating material is a high-temperature resistant nickel-based anti-sticking lubricant or a graphite high-temperature grease. The material of the tooling cylinder 4 should have sufficient mechanical properties at the stress-relieving heat treatment temperature of the lead screw 5, and be able to ensure the stability of its shape and size.

[0057] S2. The tooling cylinder 4, together with the lead screw 5, is hoisted and placed vertically in the heating furnace for stress-relieving heat treatment, so that the lead screw 5 produces slight plastic deformation. The slight plastic deformation is controlled within the preset deformation threshold range. The above steps are repeated until the slight plastic deformation accumulates to the required straightening deformation amount.

[0058] In this case, the deformation occurs immediately upon the application of external force, but only a portion of the deformation disappears immediately upon the removal of the force, while the remaining deformation persists even after the force is removed; this is known as micro-plastic deformation. This plastic deformation is caused by the stress at the deformed area exceeding the material's yield strength. The preset deformation threshold range is calculated using a finite element model based on the elastic-plastic deformation theory. This finite element model is constructed using existing finite element analysis software such as ABAQUS or ANSYS, based on the structure of the lead screw 5.

[0059] Based on the amount of deformation correction and the range of deformation threshold, the screwing depth of the clamping screw 2 is then iteratively adjusted.

[0060] The tooling cylinder 4 and the lead screw 5 are placed together in a heating furnace for heat treatment. Heat treatment can reduce the residual stress in the lead screw 5, redistribute it to a more uniform degree, and enhance the deformation resistance of the metal matrix, thereby improving the geometric accuracy and stability of the lead screw 5 and preventing it from rebounding after straightening.

[0061] The tooling cylinder 4, together with the lead screw 5, is placed vertically in the heating furnace by hoisting to reduce deformation caused by its own weight when placed horizontally.

[0062] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A stress-relieving heat treatment straightening device for lead screws, characterized in that, Includes a tooling cylinder, wherein the tooling cylinder is hollow; A plurality of straightening units are provided around the circumference of the tooling cylinder, and the straightening units are evenly distributed along the length of the tooling cylinder and in the same orientation. Each straightening unit includes a clamping screw and a locking nut, with one end of the clamping screw passing through the locking nut and extending into the tooling cylinder. The insertion depth of the clamping screw is adjustable to control the deformation of the lead screw. The insertion depth of the clamping screw is iteratively adjusted according to the amount of deformation to be corrected and the deformation threshold range. A measuring reference surface is provided on the surface of the tooling cylinder, which is located at the installation location of the clamping screw and parallel to the central axis of the tooling cylinder, and perpendicular to the clamping screw. The number of clamping screws is three or more, and they are evenly distributed along the circumference of the tooling cylinder and located in the same cross-section; The lead screw is placed on the tooling cylinder, and one end of the clamping screw contacts the deformed part of the lead screw so that the lead screw deforms in the opposite direction to the original deformation direction. The lead screw and the tooling cylinder are heated simultaneously until the required straightening deformation is achieved. The stress value at the deformed part of the lead screw is higher than the yield strength of the lead screw material at the stress relief heat treatment temperature.

2. The lead screw stress-relieving heat treatment straightening device as described in claim 1, characterized in that, The tooling cylinder has lead screw through holes at both the top and bottom; The tooling cylinder is provided with lifting bolts on its circumferential side, and the lifting bolts are located at one end of the tooling cylinder along its length; the tooling cylinder is provided with limit screws on its circumferential side, and the limit screws are located at the other end of the tooling cylinder along its length.

3. The lead screw stress-relieving heat treatment straightening device as described in claim 1, characterized in that, The cross-sectional area of ​​the tooling cylinder is larger than the cross-sectional area of ​​the lead screw.

4. A method for stress-relieving heat treatment and straightening of a lead screw based on the lead screw stress-relieving heat treatment and straightening device according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Place the lead screw in the tooling cylinder, pass the clamping screw through the lock nut and screw it into the tooling cylinder, with the end of the clamping screw pressing against the lead screw; adjust the screwing depth of the clamping screw located at the deformed part of the lead screw so that the lead screw deforms in the opposite direction to the original deformation, and tighten the lock nut. S2. The tooling cylinder connecting screw is hoisted and placed vertically in the heating furnace for stress relief heat treatment, so that the screw will undergo slight plastic deformation. Repeat the above steps until the accumulated micro-plastic deformation reaches the required amount of straightening deformation.

5. The stress-relieving heat treatment straightening method for lead screws as described in claim 4, characterized in that, S1 further includes: The stress values ​​of the deformed parts of the lead screw under applied deformation are calculated using the elastic-plastic deformation theory. In this process, the direction of the applied deformation is opposite to the original deformation direction, and the stress value is higher than that of the stress-relief heat treatment. Yield strength of lead screw material at temperature.

6. The stress-relieving heat treatment and straightening method for lead screws as described in claim 4, characterized in that, Before tightening the clamping screws and lock nuts, the following are also included: Apply a high-temperature resistant, non-stick lubricating material to the surfaces of the clamping screws and locking nuts.

7. The lead screw stress-relieving heat treatment straightening method as described in claim 4, characterized in that, The minute plastic deformation is controlled within a deformation threshold range, wherein the deformation threshold range is preset.

8. The stress-relieving heat treatment and straightening method for lead screws as described in claim 4, characterized in that, The screwing depth of the clamping screw located at the deformation part of the lead screw is adjusted based on the measurement reference plane and according to the amount of minute plastic deformation.

9. The stress-relieving heat treatment and straightening method for lead screws as described in claim 4, characterized in that, S1 further includes: After placing the lead screw in the tooling cylinder, screw the limit screw into the tooling cylinder so that the lead screw is above the limit screw to prevent the lead screw from falling off.

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