A valve stem thread rolling auxiliary device

Abstract

The application discloses a valve rod thread rolling auxiliary device, and relates to the technical field of machining, which is arranged between two thread rolling wheels of a two-shaft thread rolling machine and comprises a bottom plate arranged between the two thread rolling wheels, a fixed placement plate arranged on the upper side of the bottom plate and capable of being lifted, a load sensor arranged on the bottom plate and used for bearing the fixed placement plate, a second electromagnet arranged on the bottom plate and used for adjusting the lifting of the fixed placement plate, and a sliding placement plate arranged on the upper side of the fixed placement plate and capable of being steadily slid in the same direction as the moving direction of a valve rod to be thread rolled.

Description

Technical Field

[0001] This invention relates to the field of machining technology, and in particular to a valve stem thread rolling auxiliary device. Background Technology

[0002] Twin-axis thread rolling machines are widely used for convenient thread rolling of valve stem raw materials. During the axial thread rolling process, simply start the twin-axis thread rolling machine and manually place the valve stem to be rolled between the two rolling wheels to make contact with the two rolling wheels. As the valve stem is rolled, the threaded engagement will push the valve stem forward to increase the rolling length. When the valve stem reaches the preset length, the worker will manually remove it.

[0003] However, in order to save costs, small and medium-sized machining plants currently install a push rod between the two thread rolling wheels to limit the length of the valve stem thread rolling. Although it can limit the length of the thread rolling, the valve stem still needs to be removed manually after the thread rolling is completed. On the one hand, it is not possible for a person to remove the valve stem immediately when it touches the push rod, which can easily damage the valve stem by the thread rolling machine. On the other hand, when the valve stem material is put down manually, the unprocessed end is far away from the thread rolling machine, which is relatively safe. However, after the thread rolling is completed, the part that can be held becomes much smaller, and there is a certain probability of danger if the person uses their hand to approach the thread rolling equipment. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to solve the technical problems in the prior art and provide a valve stem thread rolling auxiliary device.

[0005] Technical solution: This application proposes a valve stem thread rolling auxiliary device, disposed between the two thread rolling wheels of a two-shaft thread rolling machine, comprising:

[0006] The base plate is installed between the two thread rolling wheels;

[0007] A fixed placement plate is mounted on the upper side of a base plate and can be raised and lowered. A load-bearing sensor for supporting the fixed placement plate and a second electromagnet for adjusting the raising and lowering of the fixed placement plate are placed on the base plate.

[0008] The sliding plate is located on the upper side of the fixed plate and can slide steadily, and the sliding direction is consistent with the moving direction when the thread-rolling valve stem is rolled.

[0009] A telescopic rod is fixedly installed on one side of a vertical plate on one end of the base plate. A spring is fixedly fitted on the outside of the telescopic rod. One end of the spring is connected to a first magnetic ring. A first electromagnet connected to the vertical plate is provided on one side of the magnetic ring.

[0010] The base plate is also provided with a strip resistor. The lower side of the telescopic rod near the sliding placement plate is connected to a sliding rod. The bottom end of the sliding rod is provided with a contact assembly that can slide outside the strip resistor to obtain the current through the contact to one end of the strip resistor, so as to control the switching of the second electromagnet and adjust the magnetic force of the first electromagnet located at one end of the telescopic rod through an adaptive algorithm.

[0011] Preferably, multiple load cells and a second electromagnet are connected and installed on the base plate, and the load cells are connected to the fixed placement plate via elastic telescopic rods;

[0012] The bottom of the fixed placement plate is connected to a magnetic component corresponding to the position of the second electromagnet.

[0013] Preferably, a slider is provided at the bottom of the sliding placement plate, and multiple slide rails are provided on the upper side of the fixed placement plate so that the slider can slide in cooperation with the slide rails, and a limiting block is provided at the end of the slide rail away from the vertical plate.

[0014] Preferably, the spring is connected to a fixed plate at a point away from the first magnetic ring, one side of the fixed plate is rotatably connected to a rotating plate via a bearing, and the bottom of the fixed plate is connected to the top of the sliding rod.

[0015] Preferably, the contact assembly includes two arc-shaped contact pieces and a roller. The two arc-shaped contact pieces are fixedly disposed at the bottom of both sides of the sliding rod, the roller is disposed at the bottom of the sliding rod, and the arc-shaped contact pieces are disposed on both sides of the roller.

[0016] Preferably, the fixed placement plate is provided with a strip-shaped hole so that the sliding rod can slide within the strip-shaped hole.

[0017] Preferably, it further includes a control unit configured to execute the adaptive algorithm, including:

[0018] Real-time acquisition of gravity signals from load cells The current from the contact to the end of the strip resistor furthest from the sliding plate. A pre-set threshold current based on the valve stem thread length. ;

[0019] The formula for calculating the starting current of the first electromagnet is as follows:

[0020] ;

[0021] in, K is the equivalent coefficient of the spring. To compensate for the gain of the electromagnet, The starting current for the first electromagnet. For safe saturation current.

[0022] Preferably, the formula for calculating the equivalent coefficient K of the spring is as follows:

[0023] ;

[0024] Where n is the total number of calibration groups, and j is the experiment number. Let the mass of the weights used in the j-th experiment be . This is the input current measured when the device is pushed to the trigger position during the j-th experiment.

[0025] Preferably, the electromagnet compensates for the gain. The calculation formula is as follows:

[0026] ;

[0027] in, To let The minimum electromagnet output current required for the object to bounce back up. This is the minimum starting current.

[0028] Preferably, the switch for controlling the second electromagnet includes:

[0029] Current Greater than or equal to the threshold current The second electromagnet is activated at a preset time.

[0030] Beneficial effects:

[0031] This system enables automatic ejection of the valve stem after thread rolling, improving safety. When the valve stem advances to a preset length under the action of the thread rolling wheels, the sliding placement plate is pushed to the trigger position. The contact assembly at the bottom of the sliding rod slides to the corresponding position on the strip resistor. After the control unit detects that the current has reached the threshold current, it automatically controls the second electromagnet to be energized, driving the fixed placement plate to spring upward and eject the valve stem from between the thread rolling wheels. The entire process requires no manual material handling, completely eliminating the safety hazard of operators' hands being close to the operating equipment.

[0032] This invention achieves differentiated auxiliary thrust for valve stems of varying weights through an adaptive algorithm. It uses a load cell to acquire the valve stem's weight in real time and calculates the equivalent weight the spring can bear at the trigger position by combining the spring's equivalent coefficient and threshold current. When the valve stem weight exceeds the spring's bearing capacity (Δ>0), the control unit automatically calculates the compensation current required by the first electromagnet, providing additional electromagnetic thrust for the spring to extend. For valve stems of different weights and lengths, the system can adaptively adjust the magnitude of the auxiliary thrust: for lightweight but long valve stems, the spring is fully compressed and its own elasticity is sufficient, requiring no force from the electromagnet; for heavy but short valve stems, the spring compression is small and its own elasticity is insufficient, requiring the electromagnet to automatically output a larger current for compensation.

[0033] This invention employs a multi-point calibration least squares method to improve system accuracy and robustness. Through multi-point calibration experiments, the least squares method is used to fit the spring's equivalent coefficient K and the electromagnet's compensation gain, effectively eliminating the effects of sliding rheostat nonlinearity, mechanical backlash error, and random errors from single measurements. Compared to the traditional two-point calibration method, the calibration results of this invention are more repeatable in engineering and environmentally adaptable. Even if the spring undergoes fatigue softening after long-term use, accuracy can be restored simply by recalibrating.

[0034] With its simple structure and low cost, this invention is suitable for widespread application in small and medium-sized machine processing plants. It only requires adding a base plate, a fixed placement plate, a sliding placement plate, a telescopic rod, a spring, a strip resistor, and corresponding electromagnets and sensors between the two rolling wheels of an existing dual-shaft thread rolling machine. Compared to expensive fully automatic loading and unloading equipment, this device has a compact structure and low modification costs, making it ideal for small and medium-sized machine processing plants with limited funds to upgrade their equipment. Attached Figure Description

[0035] Figure 1 This is a three-dimensional schematic diagram of an embodiment of the present invention;

[0036] Figure 2 This is a top view schematic diagram of an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of one side of an embodiment of the present invention;

[0038] Figure label:

[0039] 1. Base plate; 2. Fixed placement plate; 3. Load cell; 4. Second electromagnet; 5. Sliding placement plate; 6. Telescopic rod; 7. Spring; 8. Strip resistor; 9. Sliding rod; 10. Control unit; 11. First electromagnet; 12. Magnetic component; 13. Slider; 14. Slide rail; 15. Limiting block; 16. First magnetic ring; 17. Fixed plate; 18. Rotating plate; 19. Arc-shaped contact piece; 20. Roller; 21. Strip hole; 22. Elastic telescopic rod. Detailed Implementation

[0040] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] Example 1:

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "including" and similar expressions used herein mean that the element or object preceding the term covers the element or object listed after the term and its equivalents, but do not exclude other elements or objects.

[0043] Example 1: Addressing the problems existing in the prior art, such as Figure 1-3 As shown, a valve stem thread rolling auxiliary device is proposed, which is disposed between the two thread rolling wheels of a two-shaft thread rolling machine, and includes:

[0044] The base plate 1 is installed between the two thread rolling wheels; in specific implementation, it is convenient to fix the base plate to the two thread rolling wheel brackets of the existing twin-shaft thread rolling machine. This application can be integrated into a single product, which can be installed conveniently without the need for complex modifications to the existing equipment.

[0045] A fixed placement plate 2 is located on the upper side of the base plate 1 and can be raised and lowered. A load-bearing sensor 3 for supporting the fixed placement plate 2 and a second electromagnet 4 for adjusting the raising and lowering of the fixed placement plate 2 are placed on the base plate 1.

[0046] The sliding plate 5 is located on the upper side of the fixed plate 2 and can slide stably, and the sliding direction is consistent with the moving direction when the thread-rolling valve stem is rolled.

[0047] Telescopic rod 6 is fixedly installed on one side of the vertical plate on one end of the base plate 1. A spring 7 is fixedly sleeved on the outside of the telescopic rod 6. One end of the spring 7 is connected to the first magnetic ring 16. A first electromagnet 11 connected to the vertical plate is provided on one side of the magnetic ring.

[0048] The base plate 1 is also equipped with a strip resistor 8. A sliding rod 9 is connected to the lower side of the telescopic rod 6 near the sliding placement plate 5. The bottom end of the sliding rod 9 is equipped with a contact assembly that can slide outside the strip resistor 8 to obtain current flowing through the contact to one end of the strip resistor 8. This controls the switching of the second electromagnet 4 and adjusts the magnetic force of the first electromagnet 11 located at one end of the telescopic rod 6 using an adaptive algorithm. When the valve stem, after thread rolling, is pushed out, a conveyor belt can be installed on one side of the thread rolling machine. The force of pushing out the valve stem is adjusted using an adaptive algorithm to control its fall onto the leather conveyor belt. The pushing force is adjusted by gravity and length to avoid excessive or insufficient force.

[0049] In some specific embodiments, a plurality of load-bearing sensors 3 and a second electromagnet 4 are connected and installed on the base plate 1, and the load-bearing sensors 3 are connected to the fixed placement plate 2 via elastic telescopic rods 22;

[0050] The bottom of the fixed placement plate 2 is connected to a magnetic component 12 corresponding to the position of the second electromagnet 4.

[0051] In some specific embodiments, a slider 13 is provided at the bottom of the sliding placement plate 5, and multiple slide rails 14 are provided on the upper side of the fixed placement plate 2 so that the slider 13 can slide in cooperation with the slide rails 14. A limiting block 15 is provided at the end of the slide rail 14 away from the vertical plate so that the sliding placement plate 5 can slide stably. The sliding is more stable through the action of the slider 13 and the slide rails 14, and a certain limit is provided by the limiting block 15.

[0052] In some specific embodiments, the spring 7 is connected to a fixed plate 17 at a section away from the first magnetic ring 16. One side of the fixed plate 17 is rotatably connected to a rotating plate 18 via a bearing. The bottom of the fixed plate 17 is connected to the top of the sliding rod 9. When the valve stem is moved by the thread rolling, the top of the valve stem can rotate to drive the rotating plate 18 to rotate, thus avoiding scratching one end of the valve stem.

[0053] In some specific embodiments, the contact assembly includes two arc-shaped contacts 19 and a roller 20. The two arc-shaped contacts 19 are fixedly disposed at the bottom of both sides of the sliding rod 9, and the roller 20 is disposed at the bottom of the sliding rod 9. The arc-shaped contacts 19 are disposed on both sides of the roller 20. The two arc-shaped contacts 19 are conductive to each other and can simultaneously contact the strip resistor during sliding to improve conductivity. The roller 20 improves stability during sliding to a certain extent.

[0054] In some specific embodiments, the fixed placement plate 2 is provided with a strip hole 21 so that the sliding rod 9 can slide within the strip hole 21.

[0055] Example 2: Specific execution method of the adaptive algorithm:

[0056] Step 1: Parameter Calibration

[0057] In some specific embodiments, the equivalent coefficient K of the spring is calibrated as follows: with both the first electromagnet 11 and the second electromagnet 4 de-energized, n sets of known weights of different masses (n≥3) are placed sequentially, and the mass of each set of weights is recorded. and the corresponding input current The formula for calculating the equivalent coefficient K of the spring 7 is as follows:

[0058] ;

[0059] Where n is the total number of calibration groups, and j is the experiment number. Let the mass of the weights used in the j-th experiment be . This is the input current measured when the device is pushed to the trigger position during the j-th experiment.

[0060] In some specific embodiments, n sets of overweight weights (the weight of the weights exceeds the critical load-bearing capacity of spring 7) are selected. For each set of weights, the current of the first electromagnet 11 is gradually increased from zero until the weights are just bounced up, and the output current at this time is recorded. Simultaneously record the corresponding input current. The electromagnet compensates for the gain. The calculation formula is as follows:

[0061] ;

[0062] in, To let The minimum electromagnet output current required for the object to bounce back up. This is the minimum starting current.

[0063] Step Two: Real-time Operation

[0064] When the valve stem is placed between the two thread rolling wheels and on the upper side of the sliding plate 5, it overcomes the elastic telescopic rod 22 by gravity and moves downward. As the thread rolling continuously squeezes the rotating plate 18, it pushes the telescopic rod 6 to overcome the force of the spring 7.

[0065] In some specific embodiments, a control unit 10 is also included, the control unit 10 being configured to execute the adaptive algorithm, including:

[0066] Instantly acquire gravity signals from load cell 3 The current from the contact to the end of the strip resistor 8 away from the sliding plate 5 A pre-set threshold current based on the valve stem thread length. ;

[0067] The formula for calculating the starting current of the first electromagnet 11 is as follows:

[0068] ;

[0069] in, K is the equivalent coefficient of spring 7. To compensate for the gain of the electromagnet, The starting current for the first electromagnet 11, For safe saturation current.

[0070] In some specific embodiments, controlling the switch of the second electromagnet 4 includes:

[0071] Current Greater than or equal to the threshold current The second electromagnet 4 is turned on at a preset time.

[0072] During normal processing, the control unit 10 performs the following operations in real time:

[0073] (1) Real-time acquisition of the valve stem weight signal m detected by the load sensor 3, and the real-time current generated by the contact assembly sliding on the strip resistor 8 (the strip resistor can be implemented in various forms, one is a strip of metal with resistance value, and the other is a metal strip with resistance value wrapped on an insulating strip). ;

[0074] (2) Determine the current Has the preset threshold current been reached? :

[0075] As the telescopic rod 6 is compressed, the contact assembly slides on the strip resistor 8, and the control unit detects the current between the contact and the other end of the strip resistor. The further you go Figure 2 The more the right side pushes, the greater the current.

[0076] like < This indicates that the valve stem has not yet reached the preset thread rolling length. The first electromagnet 11 remains de-energized (Io=0), and the second electromagnet 4 also remains de-energized. Specifically... It corresponds one-to-one with the preset thread rolling length, and can be preset and adjusted in advance through the control unit;

[0077] like This indicates that the valve stem has reached the preset thread length (in actual use, the valve is triggered when the two values ​​are equal). equal The control unit 10 further calculates... :

[0078] If Δ≤0, it means the valve stem is relatively light, indicating that the spring force of spring 7 at the current position is sufficient to pop the valve stem out, and the first electromagnet 11 remains de-energized. );

[0079] If Δ>0, it means that the valve stem is too heavy, indicating that the spring force of the spring 7 is insufficient to pop the valve stem out. The control unit 10 calculates the required output current of the first electromagnet 11 and controls the first electromagnet 11 to output the current to assist the spring 7 in popping the valve stem out.

[0080] At the same time, when The control unit 10 controls the second electromagnet 4 to be energized and continuously for a preset time (e.g., 0.1s to 2s), driving the fixed placement plate 2 to spring upward. At this time, there is no engagement between the valve stem thread and the thread rolling wheel, and the valve stem is ejected from between the thread rolling wheels due to the loss of engagement resistance.

[0081] Step 3: Reset

[0082] After the valve stem is ejected, the control unit 10 controls the first electromagnet 11 and the second electromagnet 4 to be de-energized, the spring 7 returns to its natural state, and the sliding placement plate 5 is reset to its initial position under the action of the spring 7, waiting for the next processing.

[0083] Example 3: Adaptive adjustment effect under different operating conditions:

[0084] Operating Condition 1: Lightweight and long valve stem

[0085] When the valve stem is lightweight but long, it advances a greater distance during thread rolling, resulting in deeper compression of spring 7. At the actuated position, spring 7 stores a significant amount of elastic potential energy, effectively bearing the weight... Greater than the actual valve stem weight m, i.e. At this time, the control unit (10) determines that the spring force is sufficient, and the first electromagnet (11) remains de-energized. The valve stem can be ejected using only the elastic force of spring 7, thus achieving energy-saving operation.

[0086] Operating Condition 2: The valve stem is heavy and long.

[0087] When the valve stem is heavy and long, it advances a greater distance during thread rolling, resulting in deeper compression of spring 7, but also increasing the weight of the valve stem. In the actuated position, the equivalent load on spring 7 is... Less than the actual valve stem weight m, i.e. However, the difference is relatively small. At this time, the control unit 10 calculates a medium-sized output current for the first electromagnet 11, and the auxiliary spring 7 pops the valve stem out.

[0088] Operating Condition 3: Valve stem is heavy and short.

[0089] When the valve stem is heavy but short, it advances a small distance during thread rolling, resulting in shallow compression of spring 7 and less stored elastic potential energy. In the actuated position, the equivalent load-bearing weight of spring 7 is... Much smaller than the actual valve stem weight m, i.e. The value is a relatively large positive value. At this time, the output current of the first electromagnet 11 calculated by the control unit 10 is large; if it exceeds the safe saturation current... Then according to The output is provided by the electromagnet, which generates a repulsive force between the first electromagnet 11 and the magnetic component 12 to push the magnetic component 12 (in specific implementation, a slider can be set inside the magnetic component 12, and a groove can be set on the outermost outer shell of the elastic telescopic rod to achieve the effect of sliding stability, limiting and restricting the maximum thrust) to compress the spring 7, so as to ensure that the valve stem can be ejected smoothly.

[0090] Example 4: Specific Implementation of the Control Unit

[0091] The control unit 10 can be implemented using a microcontroller (such as the STM32 series), a programmable logic controller (PLC), or an embedded industrial computer. The control unit 10 includes:

[0092] The signal acquisition module is used to receive the gravity signal from the load cell 3 (average value from multiple gravity cells) and the current signal from the bar resistor 8, and perform analog-to-digital conversion.

[0093] The storage module is used to store the calibration parameters K, α, and α. , , And data such as preset duration;

[0094] The computation module is used to perform mathematical operations for the aforementioned adaptive algorithm;

[0095] The drive module is used to output the corresponding current to the first electromagnet 11 based on the calculation result.

[0096] And the second electromagnet 4.

[0097] The control unit 10 may also include a display module and an input module for displaying real-time operating parameters and receiving parameter setting instructions from the operator.

[0098] The above description is merely a specific implementation of the embodiments of the present invention, but the protection scope of the embodiments of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the embodiments of the present invention should be covered within the protection scope of the embodiments of the present invention. Therefore, the protection scope of the embodiments of the present invention should be determined by the protection scope of the claims.

Claims

1. A valve stem thread rolling auxiliary device, characterized in that, Located between the two thread rolling wheels of a two-shaft thread rolling machine, including: The base plate (1) is installed between the two thread rolling wheels; A fixed placement plate (2) is provided on the upper side of the base plate (1) and can be raised and lowered. A load-bearing sensor (3) for supporting the fixed placement plate (2) and a second electromagnet (4) for adjusting the raising and lowering of the fixed placement plate (2) are placed on the base plate (1). The sliding plate (5) is located on the upper side of the fixed plate (2) and can slide steadily, and the sliding direction is consistent with the moving direction when the thread-rolling valve rod is threaded. Telescopic rod (6) is fixedly installed on one side of the vertical plate at one end of the base plate (1). A spring (7) is fixedly fitted on the outside of the telescopic rod (6). One end of the spring (7) is connected to the first magnetic ring (16). A first electromagnet (11) connected to the vertical plate is provided on one side of the magnetic ring. Among them, a strip resistor (8) is also provided on the base plate (1), and a sliding rod (9) is connected to the lower side of one end of the telescopic rod (6) near the sliding placement plate (5). A contact assembly that can slide outside the strip resistor (8) is provided at the bottom end of the sliding rod (9) to obtain the current through the contact to one end of the strip resistor (8) so as to control the switch of the second electromagnet (4) and adjust the magnetic force of the first electromagnet (11) provided at one end of the telescopic rod (6) through an adaptive algorithm. Multiple load cells (3) and a second electromagnet (4) are connected and installed on the base plate (1). The load cells (3) are connected to the fixed placement plate (2) through an elastic telescopic rod (22). The bottom of the fixed placement plate (2) is connected to a magnetic component (12) corresponding to the position of the second electromagnet (4); The contact assembly includes two arc-shaped contact pieces (19) and a roller (20). The two arc-shaped contact pieces (19) are fixedly disposed at the bottom of both sides of the sliding rod (9), the roller (20) is disposed at the bottom of the sliding rod (9), and the arc-shaped contact pieces (19) are disposed on both sides of the roller (20). It also includes a control unit (10) configured to execute the adaptive algorithm, including: Real-time acquisition of gravity signals from load cell (3) The current from the contact to the end of the strip resistor (8) away from the sliding plate (5) A pre-set threshold current based on the valve stem thread length. ; The starting current of the first electromagnet (11) is calculated using the following formula: ； in, K is the equivalent coefficient of spring (7). To compensate for the gain of the electromagnet, The starting base current for the first electromagnet (11) is... For safe saturation current.

2. The valve stem thread rolling auxiliary device according to claim 1, characterized in that, The bottom of the sliding placement plate (5) is provided with a slider (13), and the upper side of the fixed placement plate (2) is provided with multiple slide rails (14) so ​​that the slider (13) can slide in cooperation with the slide rails (14). A limiting block (15) is provided at the end of the slide rail (14) away from the vertical plate.

3. The valve stem thread rolling auxiliary device according to claim 1, characterized in that, The spring (7) is connected to a fixed plate (17) at one end away from the first magnetic ring (16). One side of the fixed plate (17) is rotatably connected to a rotating plate (18) via a bearing. The bottom of the fixed plate (17) is connected to the top of the sliding rod (9).

4. The valve stem thread rolling auxiliary device according to claim 1, characterized in that, The fixed placement plate (2) is provided with a strip hole (21) so that the sliding rod (9) can slide in the strip hole (21).

5. The valve stem thread rolling auxiliary device according to claim 1, characterized in that, The formula for calculating the equivalent coefficient K of the spring (7) is as follows: ； Where n is the total number of calibration groups, and j is the experiment number. Let the mass of the weights used in the j-th experiment be . This is the input current measured when the device is pushed to the trigger position during the j-th experiment.

6. The valve stem thread rolling auxiliary device according to claim 5, characterized in that, The electromagnet compensates for the gain. The calculation formula is as follows: ； in, To let The minimum electromagnet output current required for the object to bounce back up. This is the minimum starting current.

7. The valve stem thread rolling auxiliary device according to claim 1, characterized in that, The switch for controlling the second electromagnet (4) includes: Current Greater than or equal to the threshold current The second electromagnet (4) is turned on for a preset time.

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