Thread rolling method capable of adjusting stroke of thread rolling die

Abstract

The invention relates to the technical field of thread rolling machining, in particular to a thread rolling method capable of adjusting the stroke of a thread rolling die, which comprises the following steps of: keeping the relative rotational motion of the thread rolling die and a workpiece to carry out thread rolling on the workpiece, and completing the thread rolling work in the effective stroke LY of the thread rolling die; the motion compensation stroke is achieved through the linear velocity difference VL between the thread rolling die and the workpiece; meanwhile, the thread rolling die or the workpiece is driven by the motion control mechanism to axially move, so that the thread rolling length is increased; and an axial compensation speed model is established, the compensation speed Va is dynamically adjusted according to the rolling force Fz detected in real time, the coordination among the axial movement speed of the thread rolling die, the rotating speed of the thread rolling die and the rotating speed of a workpiece is guaranteed in real time, and the quality of rolled threads is guaranteed. The thread quality problems caused by a traditional connecting and rolling mode, such as the defects of thread form folding and crossing, are effectively avoided, and the thread rolling quality is improved.

Description

Technical Field

[0001] The invention relates to the technical field of thread rolling processing, and in particular to a thread rolling method with adjustable thread rolling die stroke. Background Art

[0002] Thread rolling is a common metal processing method, which is widely used in manufacturing parts with regular patterns such as threads, straight grains, and twill grains. The thread rolling machine is a key equipment for thread rolling. The effective stroke of the thread rolling die refers to the effective working length range in which the die can normally roll the workpiece during the thread rolling process. When the effective stroke of the thread rolling die is not enough to meet the requirements of the workpiece rolling length, the existing technology usually adopts the following solutions:

[0003] 1. Adjust the parameters of the thread rolling machine: Some thread rolling machines have a stroke adjustment device. You can try to increase the stroke by adjusting the relevant parameters of the thread rolling machine. For example, check whether the transmission mechanism of the thread rolling machine has an adjustable screw or guide rail, and increase the stroke of the thread rolling die appropriately by fine-tuning these components. However, this adjustment range is usually limited because the overall structure and design parameters of the thread rolling machine limit the large change of the stroke.

[0004] Second, use the method of multiple rolling (joint rolling): Divide the workpiece with a long rolling length into several sections for rolling. For example, if the rolling length requirement is L, and the effective stroke of the thread rolling die is l (L>l), you can first roll the first section with a length of l, then move the workpiece, reposition it, and then roll the next section until the entire rolling length L is completed. However, it should be noted that multiple rolling may cause an uneven transition at the connection of adjacent rolling sections. In order to reduce this situation, appropriate adjustments can be made in the overlapping area of ​​each rolling, such as reducing the rolling force or slowing down the rolling speed to make the connection more natural.

[0005] 3. Replace the appropriate thread rolling die: Choose a thread rolling die with a longer effective stroke. When purchasing a thread rolling die, you should accurately measure the required effective stroke according to the thread rolling length requirements of the workpiece. For example, if the thread rolling length of the workpiece is 50mm, and the effective stroke of the existing thread rolling die is only 30mm, you need to find a thread rolling die with an effective stroke greater than or equal to 50mm. At the same time, you should also consider whether other parameters of the thread rolling die, such as thread specifications, materials, etc., match the workpiece and the thread rolling machine.

[0006] However, the above solutions have certain defects. When using the method of multiple rolling, the transition between adjacent rolling sections is prone to unevenness, which affects the quality of rolling. When replacing the rolling die, it is necessary to consider the compatibility of the new die with the existing equipment, which increases the cost. Therefore, there is an urgent need for a new technical solution that can effectively increase the effective stroke of the rolling die, improve the rolling quality, and reduce the production cost.

[0007] In view of this, the present invention provides a thread rolling method with adjustable thread rolling die stroke. Summary of the invention

[0008] The purpose of the present invention is to provide a thread rolling method with adjustable thread rolling die stroke to address the deficiencies of the prior art, which can accurately detect the plugging and unplugging status of the plug to improve the safety and convenience of socket use.

[0009] In order to solve the above technical problems, the following technical solutions are adopted:

[0010] A thread rolling method with adjustable thread rolling die stroke, by controlling the thread rolling die rotation speed n1 and the workpiece rotation speed n2, a linear speed difference V between the thread rolling die and the workpiece is obtained. L =π*D1*n1-π*D2*n2, and the total length of rolling thread L Z =L Y +ΔL, where L Y is the effective stroke of the thread rolling die itself, ΔL is the motion compensation stroke, and specifically includes the following steps:

[0011] S1. Keep the relative rotation between the thread rolling die and the workpiece to roll the workpiece and complete the effective stroke L of the thread rolling die itself. Y Thread rolling work inside;

[0012] S2. Using the linear speed difference V between the thread rolling die and the workpiece L To achieve motion compensation stroke; at the same time, the motion control mechanism drives the thread rolling die or workpiece to move axially to extend the thread rolling length;

[0013] S3. Establish an axial compensation velocity model: Va = (n1-n2)·P·tanθ / (2π), where P is the theoretical pitch and θ is the helix angle;

[0014] The thread rolling die speed n1 and the workpiece speed n2 are synchronously controlled by a motion controller; the compensation speed Va is dynamically adjusted according to the rolling pressure Fz detected in real time.

[0015] Furthermore, an adaptive control algorithm based on Lyapunov stability is introduced in S3:

[0016] The kinetic equation is as follows:

[0017]

[0018] Among them, τ is the torque of the control input, J is the inertia matrix, q is the generalized coordinate, is the generalized speed, is the generalized acceleration vector, is the Coriolis force and centrifugal force matrix, G(q) is the gravity vector, e is the tracking error, K p , Ki is the adaptive gain matrix, K p , K i Adaptive adjustment based on the Lyapunov function V.

[0019] Furthermore, in S3, the motion controller adopts a three-level control architecture, including:

[0020] (a) The host computer generates the machining path planning and transmits the data to the motion controller via the EtherCAT Ethernet network protocol;

[0021] (b) The motion controller executes the CANopen protocol to control the servo drive, and the motion controller executes the Profinet protocol to control the PLC control module;

[0022] (c) The servo drive realizes dual closed-loop control of the speed loop and position loop, and the PLC control module controls the operation of the hydraulic system and the sensor group.

[0023] Furthermore, the motion control mechanism is installed on the thread rolling die or on a fixture of the workpiece.

[0024] Furthermore, the motion control mechanism includes a drive module, a linear guide and a ball screw transmission system, wherein the linear guide is used to drive the linear motion of the thread rolling die or the workpiece in the horizontal direction, and the ball screw is used to convert the rotational motion of the drive module into the linear motion of the thread rolling die; the drive module includes a servo motor or a hydraulic drive device, which is used to drive the axial movement of the thread rolling die or the workpiece.

[0025] Furthermore, the motion control mechanism also includes a mounting structure, which is used for mounting and dismounting the motion control mechanism and the thread rolling die, and ensures the axial and radial accuracy of the thread rolling die after mounting.

[0026] Furthermore, the ball screw transmission system is equipped with a temperature compensation module, and the compensation formula is:

[0027] ΔL comp =α·(T-T0)·L0+β·(dT / dt)·L0

[0028] Where, ΔL comp is the temperature compensation length, α is the thermal expansion coefficient, T is the current temperature, T0 is the reference temperature, L0 is the initial length of the ball screw transmission mechanism at the reference temperature T0, β is the coefficient related to the temperature change rate, and dT / dt is the temperature change rate.

[0029] The above technical solution has the following beneficial effects:

[0030] The present invention discloses a thread rolling method with adjustable thread rolling die stroke, which allows the thread rolling die to generate additional movement relative to the workpiece during the thread rolling process, and utilizes the linear speed difference between the thread rolling die and the workpiece to supplement the lack of effective stroke. Specifically, a motion control mechanism is added to the original mechanism, and the motion control mechanism drives the thread rolling die or the workpiece to move axially to extend the thread rolling length; then, by establishing an axial compensation speed model, the motion controller synchronously controls the thread rolling die rotation speed and the workpiece rotation speed, and dynamically adjusts the compensation speed Va according to the real-time detected rolling force Fz, so as to ensure the coordination between the axial movement speed of the thread rolling die, the thread rolling die rotation speed and the workpiece rotation speed in real time, and ensure the quality of the rolled thread. It effectively avoids the thread quality problems caused by the traditional rolling method, such as defects such as thread tooth folding and crossing, and improves the thread rolling quality; and there is no need to replace the thread rolling die, which reduces the production cost, improves the production efficiency, shortens the process flow, and ensures the stability and consistency of the thread rolling process. This method is suitable for workpieces of various materials, especially for difficult-to-process materials such as high-strength titanium alloys, and can effectively avoid the occurrence of defects such as thread folding; this method is simple to operate, and only requires adding a set of motion control mechanisms to the existing thread rolling machine and matching the corresponding motion controller. There is no need for large-scale transformation of the thread rolling machine, which is easy to promote and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be further described below in conjunction with the accompanying drawings:

[0032] Figure 1 The present invention is a flowchart of a thread rolling method with adjustable thread rolling die stroke according to an embodiment of the present invention.

[0033] Figure 2 It is a schematic diagram of the three-dimensional structure of a thread rolling device with adjustable thread rolling die stroke according to an embodiment of the present invention.

[0034] Figure 3 A top view of a thread rolling device with adjustable thread rolling die stroke according to an embodiment of the present invention;

[0035] Figure 4 This is a front structural diagram of a thread rolling device with adjustable thread rolling die stroke according to an embodiment of the present invention;

[0036] Figure 5 A three-level control architecture diagram of a motion controller according to an embodiment of the present invention;

[0037] Figure 6 This is a front view of the thread rolling die and the workpiece in operation according to an embodiment of the present invention;

[0038] Figure 7 For the embodiment of the present invention Figure 6 Cross-sectional view along the A axis.

[0039] In the figure: 1- thread rolling die; 2- workpiece; 3- motion control mechanism; 4- fixture.

[0040] 31- drive module; 32- linear guide; 33- ball screw transmission system. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described in detail below through the accompanying drawings and embodiments as a further explanation of the present invention. However, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the scope of the present invention. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0042] See also Figure 1 , a thread rolling method with adjustable thread rolling die stroke, the principle of the scheme is as follows: by allowing the thread rolling die 1 to produce additional movement relative to the workpiece 2 during the thread rolling process, the linear speed difference is used to supplement the lack of effective stroke. Assume that the speed of the thread rolling die 1 is n1, the diameter is D1, and its linear speed v1 = π*D1*n1; the speed of the workpiece 2 is n2, the diameter is D2, and its linear speed v2 = π*D2*n2. When v1≠v2, relative motion will occur, and this relative motion can be used to extend the rolling length.

[0043] Specifically, by controlling the rotation speed n1 of the thread rolling die 1 and the rotation speed n2 of the workpiece 2, the linear speed difference V between the thread rolling die 1 and the workpiece 2 is obtained. L =π*D1*n1-π*D2*n2, and the total length of rolling thread L Z =L Y +ΔL, where L Y is the effective stroke of the thread rolling die 1 itself, ΔL is the motion compensation stroke, and specifically includes the following steps:

[0044] S1. Start the whole device, keep the relative rotation between the thread rolling die 1 and the workpiece 2 to roll the thread of the workpiece 2, and complete the effective stroke L of the thread rolling die 1 itself Y Thread rolling work inside.

[0045] S2. Using the linear velocity difference V between the thread rolling die 1 and the workpiece 2 L To achieve motion compensation stroke; at the same time, a motion control mechanism 3 capable of accurately controlling the movement of the thread rolling die 1 or the workpiece 2 is installed, and the motion control mechanism 3 is installed on the thread rolling die 1 or the fixture 4 of the workpiece 2. During the thread rolling process, according to the requirements of the thread rolling length, the thread rolling die 1 or the workpiece 2 is driven by the motion control mechanism 3 to move axially to extend the thread rolling length.

[0046] S3. Establish an axial compensation speed model: Va = (n1-n2)·P·tanθ / (2π), where P is the theoretical pitch and θ is the helix angle; synchronously control the speed n1 of the thread rolling die 1 and the speed n2 of the workpiece 2 through the motion controller; dynamically adjust the compensation speed Va according to the real-time detected rolling pressure Fz.

[0047] The compensation speed Va indicates the speed that needs to be additionally applied or adjusted in the axial direction during the spiral motion process in order to ensure that the spiral structure obtained by processing meets the theoretical requirements. By adjusting the compensation speed, the parameters such as the lead and tooth profile of the thread can be ensured to meet the design standards.

[0048] As a further explanation of this embodiment, an adaptive control algorithm based on Lyapunov stability is introduced in S3:

[0049] The kinetic equation is as follows:

[0050]

[0051] Among them, τ is the torque of the control input, J is the inertia matrix, q is the generalized coordinate, is the generalized speed, is the generalized acceleration vector, is the Coriolis force and centrifugal force matrix, G(q) is the gravity vector, e is the tracking error, K p , K i is the adaptive gain matrix, K p , K i Adaptive adjustment based on the Lyapunov function V.

[0052] As a further explanation of this embodiment, the Lyapunov function V is defined as:

[0053]

[0054] Where e is the tracking error.

[0055] is the gain error vector, which is usually defined as the difference between the actual gain and the expected gain, that is, Where K is the actual gain matrix used (such as K p or K i ), K d is the desired gain matrix.

[0056] Γ is a positive definite symmetric matrix, which is usually used to adjust the convergence speed of the adaptive law. -1 is the inverse matrix of Γ.

[0057] By taking the derivative of the Lyapunov function V and designing a suitable adaptive law based on the Lyapunov stability theory to adjust Kp and K i , so that the system meets the stability requirements and ensures that the system error e eventually converges to zero or a bounded region.

[0058] Specifically, by establishing an axial compensation speed model, the motion controller synchronously controls the rotation speed of the thread rolling die 1 and the rotation speed of the workpiece 2, and dynamically adjusts the compensation speed Va according to the real-time detected rolling pressure Fz, so as to ensure the coordination between the axial movement speed of the thread rolling die 1, the rotation speed of the thread rolling die 1 and the rotation speed of the workpiece 2 in real time, thereby ensuring the quality of the rolled thread.

[0059] Furthermore, in step S3, time control is also critical. It is necessary to accurately grasp the time point when the thread rolling die 1 starts to move axially and the time point when it stops. This time point is usually related to the end point of the effective stroke of the thread rolling die 1 itself and the rolling length requirement. By setting a suitable timer in the thread rolling machine control system or using a sensor to detect the position of the thread rolling die 1, accurate time control can be achieved.

[0060] During the movement of the thread rolling die 1, the contact pressure between the thread rolling die 1 and the workpiece 2 needs to remain stable. Therefore, this embodiment dynamically adjusts the compensation speed Va through the real-time detection of the rolling force Fz, and ensures the coordination between the axial movement speed of the thread rolling die 1, the rotation speed of the thread rolling die 1 and the rotation speed of the workpiece 2 in real time, so as to ensure the quality of the rolled thread. In addition, this can be applied to the structural design and material selection of the thread rolling die 1. The material of the thread rolling die 1 must have sufficient hardness and wear resistance to ensure that the rolling quality will not be affected by wear during the mobile rolling process. For example, commonly used thread rolling die 1 materials include cemented carbide (such as YG6, YG8, etc.), whose hardness can reach HRA89-92.5 and can withstand higher rolling pressure.

[0061] The size and shape of the thread rolling die 1 must also be compatible with the moving scheme. For example, the outer diameter of the thread rolling die 1 must match the fixture and transmission components of the thread rolling machine to ensure that there is no interference during the movement; the inner diameter of the thread rolling die 1 must be able to be easily installed on the shaft of the moving mechanism and ensure concentricity, which is generally required to be controlled within 0.01-0.03mm.

[0062] As a further explanation of this embodiment, in S3, see Figure 5 , the motion controller adopts a three-level control architecture, including host computer, EtherCAT master station, motion controller, servo drive and PLC control module:

[0063] (a) The host computer generates the processing path planning and sends it to the EtherCAT master station, which transmits it to the motion controller via the EtherCAT Ethernet network protocol data;

[0064] (b) The motion controller executes the CANopen protocol to control the servo drive, and the motion controller executes the Profinet protocol to control the PLC control module;

[0065] (c) The servo driver realizes dual closed-loop control of the speed loop and the position loop, controls the operation of the servo motor for axial movement, the rotating motor for the thread rolling die 1 and the rotating motor for the workpiece 2, and the PLC control module controls the operation of the hydraulic drive device and the sensor group.

[0066] It should be further explained that, in the present embodiment, the driving module of the motion control mechanism 3 is a servo motor or a hydraulic driving device. When the driving module of the motion control mechanism 3 is a servo motor, the servo driver controls the axial movement of the servo motor. When the driving module of the motion control mechanism 3 is a hydraulic driving device, the PLC control module controls the hydraulic driving device.

[0067] It needs to be further explained that, in this embodiment, the above-mentioned sensor group includes a laser ranging sensor, a temperature sensor, etc., wherein the laser ranging sensor is respectively provided on the thread rolling die 1 and the working fixture, and the temperature sensor is installed on the ball screw transmission system of the motion control mechanism 3.

[0068] As a further explanation of this embodiment, the motion control mechanism 3 includes a drive module 31, a linear guide 32 and a ball screw transmission system 33, wherein the linear guide 32 is used to drive the thread rolling die 1 or the workpiece 2 to move linearly in the horizontal direction, and the ball screw is used to convert the rotational motion of the drive module 31 into the linear motion of the thread rolling die 1; the drive module 31 includes a servo motor or a hydraulic drive device, which is used to drive the axial movement of the thread rolling die 1 or the workpiece 2.

[0069] Specifically, the design of the motion control mechanism 3 is critical. It is necessary to design a stable and high-precision motion control mechanism 3. Figure 2-Figure 4 , Figure 6-7 For example, a high-precision linear guide 32 and a ball screw transmission system 33 are used. The linear guide 32 must ensure the straightness of the thread rolling die 1 during movement. The pitch accuracy of the ball screw directly affects the movement accuracy of the thread rolling die 1. Generally, the accuracy level of the ball screw can reach C0-C7, and C0 has the highest accuracy. When designing, the appropriate accuracy level should be selected according to the rolling accuracy requirements, which can effectively improve the axial stiffness of the ball screw and reduce vibration during movement.

[0070] At the same time, the compatibility of the motion control mechanism 3 and the thread rolling machine needs to be considered. It is necessary to ensure that the mechanism can be easily installed on the existing thread rolling die 1 and will not interfere with the original functions of the thread rolling die 1 (such as the rotation drive of the thread rolling die 1, the clamping of the workpiece 2, etc.), so as to design a suitable connection method.

[0071] As a further illustration of this embodiment, the motion control mechanism 3 also includes a mounting structure, which is used for mounting and dismounting the motion control mechanism 3 and the thread rolling die 1 and ensures the axial and radial accuracy of the thread rolling die 1 after installation.

[0072] As a further explanation of this embodiment, the ball screw transmission system 33 is equipped with a temperature compensation module, and the compensation formula is:

[0073] ΔL comp =α·(T-T0)·L0+β·(dT / dt)·L0

[0074] Where, ΔL comp is the temperature compensation length, α is the thermal expansion coefficient, T is the current temperature, T0 is the reference temperature, L0 is the initial length of the ball screw transmission mechanism at the reference temperature T0, β is the coefficient related to the temperature change rate, and dT / dt is the temperature change rate.

[0075] The comparative effect of the above-mentioned thread rolling method and the original thread rolling method is shown in Table 1 below.

[0076] Table 1

[0077] Existing conventional equipment Embodiments of the present invention Thread rolling length 50mm 80-150mm Thread accuracy grade 8H 4H Mold change time (same specifications) 20min Within 10 minutes Effective stroke repeatability ±0.08mm ±0.015mm

[0078] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all included in the protection scope of the present invention.

Claims

1. A thread rolling method with adjustable thread rolling die stroke, characterized in that: By controlling the thread rolling die speed n1 and the workpiece speed n2, the linear speed difference V between the thread rolling die and the workpiece is obtained. L =π*D1*n1-π*D2*n2, and the total length of rolling thread L Z =L Y +ΔL, where L Y is the effective stroke of the thread rolling die itself, ΔL is the motion compensation stroke, and specifically includes the following steps: S1. Keep the relative rotation between the thread rolling die and the workpiece to roll the workpiece and complete the effective stroke L of the thread rolling die itself. Y Thread rolling work inside; S2. Using the linear speed difference V between the thread rolling die and the workpiece L To achieve motion compensation stroke; at the same time, the motion control mechanism drives the thread rolling die or workpiece to move axially to extend the thread rolling length; S3. Establish an axial compensation velocity model: Va = (n1-n2)·P·tanθ / (2π), where P is the theoretical pitch and θ is the helix angle; The thread rolling die speed n1 and the workpiece speed n2 are synchronously controlled by a motion controller; the compensation speed Va is dynamically adjusted according to the rolling pressure Fz detected in real time.

2. A thread rolling method with adjustable thread rolling die stroke according to claim 1, characterized in that: The adaptive control algorithm based on Lyapunov stability is introduced in S3: The kinetic equation is as follows: Where τ is the torque of the control input, J is the inertia matrix, q is the generalized coordinate, is the generalized speed, is the generalized acceleration vector, is the Coriolis force and centrifugal force matrix, G(q) is the gravity vector, e is the tracking error, K p , K i is the adaptive gain matrix, K p , K i Adaptive adjustment based on the Lyapunov function V.

3. A thread rolling method with adjustable thread rolling die stroke according to claim 1, characterized in that: In the S3, the motion controller adopts a three-level control architecture, including: (a) The host computer generates the machining path planning and transmits the data to the motion controller via the EtherCAT Ethernet network protocol; (b) The motion controller executes the CANopen protocol to control the servo drive, and the motion controller executes the Profinet protocol to control the PLC control module; (c) The servo drive realizes dual closed-loop control of the speed loop and position loop, and the PLC control module controls the operation of the hydraulic system and the sensor group.

4. A thread rolling method with adjustable thread rolling die stroke according to claim 1, characterized in that: The motion control mechanism is installed on the thread rolling die or on a fixture of the workpiece.

5. A thread rolling method with adjustable thread rolling die stroke according to claim 4, characterized in that: The motion control mechanism includes a drive module, a linear guide and a ball screw transmission system, wherein the linear guide is used to drive the thread rolling die or the workpiece to move linearly in the horizontal direction, and the ball screw is used to convert the rotational motion of the drive module into the linear motion of the thread rolling die; the drive module includes a servo motor or a hydraulic drive device, which is used to drive the axial movement of the thread rolling die or the workpiece.

6. A thread rolling method with adjustable thread rolling die stroke according to claim 4, characterized in that: The motion control mechanism also includes a mounting structure, which is used for mounting and dismounting the motion control mechanism and the thread rolling die, and ensures the axial and radial accuracy of the thread rolling die after mounting.

7. A thread rolling method with adjustable thread rolling die stroke according to claim 5, characterized in that: The ball screw transmission system is equipped with a temperature compensation module, and the compensation formula is: ΔL comp =a·(T-T0)·L0+b·(dT / dt)·L0 Where, ΔL comp is the temperature compensation length, α is the thermal expansion coefficient, T is the current temperature, T0 is the reference temperature, L0 is the initial length of the ball screw transmission mechanism at the reference temperature T0, β is the coefficient related to the temperature change rate, and dT / dt is the temperature change rate.

Images