A titanium alloy screw step-by-step rolling equipment

Abstract

The present application relates to the technical field of screw rolling, and discloses a titanium alloy screw step-by-step rolling equipment, which comprises a bed body support, the two sides of the bed body support are provided with synchronously and reversely rotating thread rolling wheels, and further comprises a center distance adjusting mechanism, a workpiece material supporting mechanism and a rotary driving mechanism; the rotary driving mechanism comprises a driving belt arranged at the bottom of the bed body support and having adjustable rotation direction, a driving wheel and an extrusion roller are arranged above the driving belt, and the driving wheel and the extrusion roller alternately abut against the driving belt. The driving wheel and the extrusion roller in the rotary driving mechanism are alternately arranged to abut against the driving belt which continuously operates in one direction, so that the fast forward and reverse switching of the thread rolling wheels is realized without commutation of the rotary motor, thereby performing the circumferential micro-reverse rotation relief action after each radial feeding, effectively releasing the circumferential shear residual stress of the titanium alloy thread tooth profile and weakening the work hardening effect.

Description

Technical Field

[0001] This invention relates to the field of screw rolling technology, specifically a step-by-step rolling device for titanium alloy screws. Background Technology

[0002] Thread rolling is a chipless forming process that uses a rolling roller to plastically deform the surface of a workpiece to form threads. It is widely used in fastener manufacturing due to its advantages such as high material utilization, continuous thread fibers, and good surface strength. In existing technologies, for metals with good plasticity such as carbon steel, a single-pass rolling process is typically used. This involves the rolling roller being fed radially to a preset depth in one pass, allowing the workpiece material to flow radially and circumferentially under the pressure of the rolling roller teeth, thus completing thread formation within one processing cycle. However, with the increasing demands for fastener material performance in aerospace, medical devices, and other fields, the demand for titanium alloy screws is growing due to their excellent specific strength, corrosion resistance, and biocompatibility. Currently, for thread rolling of titanium alloy screws, the industry generally uses traditional rolling equipment. After rolling, the rolling roller is controlled to retract radially, allowing the workpiece to achieve a certain degree of elastic distortion recovery in the radial direction, in order to improve the thread forming quality.

[0003] Titanium alloys inherently possess characteristics such as high hardness, poor plasticity, significant work hardening tendency, and high springback due to low elastic modulus. During single-pass high-feed rolling, insufficient material flowability easily leads to folding and internal folding defects in the thread crest region, which become fatigue crack initiation points under alternating loads, severely threatening connection reliability. A more prominent problem is that existing rolling equipment only uses a simple radial retraction action to detach the rolling wheel from the workpiece. While this allows for some radial elastic recovery of the workpiece, it provides no effective means of releasing or correcting circumferential distortion—the distortion of the thread profile in the circumferential direction. Because titanium alloys also experience significant elastic stress accumulation in the circumferential direction during rolling, the residual circumferential deformation after radial retraction cannot be orderly restored, resulting in large fluctuations in the thread pitch diameter, asymmetrical thread profile, and excessive cumulative pitch error, severely affecting thread fit accuracy and service performance. Therefore, there is an urgent need for a rolling equipment capable of performing step-by-step rolling of titanium alloy screws while simultaneously controlling radial and circumferential distortion. Summary of the Invention

[0004] The purpose of this invention is to provide a step-by-step rolling device for titanium alloy screws to solve the technical problem of thread circumferential distortion in the prior art.

[0005] A step-by-step rolling device for titanium alloy screws includes a bed support, with synchronously counter-rotating thread rolling wheels on both sides of the bed support, and also includes a center distance adjustment mechanism, a workpiece support mechanism, and a rotary drive mechanism.

[0006] The center distance adjustment mechanism includes a fixed side beam and a movable side beam disposed on both sides of the bed support. The ends of the fixed side beam and the movable side beam are provided with side plates, and the side plates are rotatably connected to a main shaft coaxially disposed with the thread rolling wheel.

[0007] A workpiece support mechanism is used to support the screw blank to be rolled between the two thread rolling wheels;

[0008] The rotary drive mechanism includes a drive belt located at the bottom of the bed support and with an adjustable rotation direction. A drive wheel and a pressing roller are arranged above the drive belt. The drive wheel and the pressing roller alternately abut against the drive belt. The drive wheel and the thread rolling wheel rotate synchronously. When the pressing roller abuts against the drive belt, the pressing roller abuts against the drive wheel and rotates synchronously.

[0009] In a preferred embodiment of the present invention, a driven gear is provided at the end of the spindle. A fixed block is fixedly connected to the side of the bed support near the fixed side beam. An input shaft is rotatably connected to the fixed block. A drive gear is fixedly connected to the end of the input shaft. The drive gear meshes with the driven gear near the fixed side beam. One end of a second connecting rod is rotatably connected to the spindle near the movable side beam. The other end of the second connecting rod is rotatably connected to one end of a first connecting rod. The other end of the first connecting rod is rotatably connected to the input shaft. A transmission gear is provided at the rotation center of the first and second connecting rods and is rotatably connected to the side of the second connecting rod. One side of the transmission gear meshes with the driven gear near the movable side beam, and the other side of the transmission gear meshes with the drive gear. The two driven gears rotate at the same speed.

[0010] As a preferred embodiment of the present invention, a suspension frame is fixedly connected to the side of the bed support near the movable side crossbeam, a sliding rod is slidably connected to the suspension frame, a driven pulley is rotatably connected to the side of the sliding rod near the movable side crossbeam, a return spring is sleeved on the outside of the sliding rod to drive the sliding rod to move toward the movable side crossbeam, a rotary motor is provided at the bottom of the fixed side crossbeam, a drive pulley is fixedly connected to the output shaft of the rotary motor, and the drive belt is tensioned between the drive pulley and the driven pulley.

[0011] As a preferred embodiment of the present invention, a rotating seat is provided at the end of the suspension frame, and a deflection arm is rotatably connected to the rotating seat. The extrusion roller is rotatably connected to the end of the deflection arm.

[0012] As a preferred embodiment of the present invention, the fixed side crossbeam is fixedly connected to the bed support, the movable side crossbeam is slidably connected to the bed support, and a radial feed assembly for driving the movable side crossbeam to move is provided at one end of the bed support near the movable side crossbeam.

[0013] As a preferred embodiment of the present invention, the radial feed assembly includes a drive mounting plate fixedly connected to the bed support, a crossbeam suspension mounting plate is provided at the bottom of the drive mounting plate, a lead screw nut seat is rotatably connected to the middle of the crossbeam suspension mounting plate, a transverse lead screw is threadedly connected to the middle of the lead screw nut seat, and a push plate fixedly connected to the movable side crossbeam is rotatably connected to the end of the transverse lead screw.

[0014] As a preferred embodiment of the present invention, guide rods that are slidably connected to the crossbeam suspension mounting plate are provided on both sides of the push plate, and a buffer spring sleeved on the outside of the guide rod is provided between the push plate and the crossbeam suspension mounting plate. A feed servo motor is provided in the middle of the drive mounting plate, and the output shaft of the feed servo motor is connected to the lead screw nut seat through a belt transmission device.

[0015] As a preferred embodiment of the present invention, the workpiece support mechanism is located on the side of the bed support away from the rotary drive mechanism. The workpiece support mechanism includes a sliding block slidably connected to the bed support, a fixed rod is provided on the sliding block, a lifting sleeve is slidably connected on the fixed rod, an extension frame is fixedly connected to the end of the lifting sleeve, a support plate is provided at one end of the extension frame near the center of the bed support, the upper surface of the support plate is higher than the upper surface of the extension frame, and a step is formed at the connection between the support plate and the extension frame for positioning the screw blank.

[0016] As a preferred embodiment of the present invention, a fixed bracket is provided on the side of the bed support, and a mounting bracket is provided above the fixed bracket. A nozzle for blowing high-speed airflow toward the screw blank is provided on the mounting bracket near the middle of the two thread rolling wheels.

[0017] By adopting the above technical solution, the present invention has the following beneficial effects:

[0018] 1. This invention achieves rapid forward and reverse switching of the thread rolling wheel by alternately abutting the drive wheel and the extrusion roller against the unidirectional continuously rotating drive belt without the need for the rotary motor to reverse, thereby completing the circumferential micro-reverse pressure relief action. Combined with radial multi-pass feed, it constructs a composite step-by-step rolling process of "radial progressive deformation + circumferential stress release", which effectively releases the circumferential shear residual stress of the titanium alloy thread profile, weakens the work hardening effect, and reduces the thread folding and micro-crack defect rate by more than 80% compared with the traditional single-pass process.

[0019] 2. The adaptive articulated transmission structure composed of the first connecting rod, the second connecting rod and the transmission gear maintains a constant transmission ratio between the drive gear, the transmission gear and the corresponding driven gear throughout the entire stroke of the radial sliding adjustment of the center distance of the movable side beam. The speed difference of the double thread rolling wheels is controlled within 0.1%, which completely avoids transmission asynchrony caused by changes in center distance and ensures the accuracy of thread pitch and tooth profile symmetry.

[0020] 3. High-pressure atomized airflow is used to cool and lubricate the rolling area and apply downward uniform dynamic pressure to suppress radial bounce of the workpiece in a non-contact manner. No rigid parts contact the thread forming surface throughout the process, eliminating defects such as titanium alloy sticking and tooth surface scratches from the root.

[0021] 4. The radial feed assembly is driven by a servo motor and a precision lead screw and nut pair. It can accurately program multiple feed speeds, feed depths and holding times, and supports customized process parameters for pre-rolling, main forming and finishing. It meets the flexible processing needs of titanium alloy screws of different specifications and grades. The thread pitch diameter accuracy can reach 4h level, and the batch consistency is excellent. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of a step-by-step rolling device for titanium alloy screws.

[0024] Figure 2 This is a front view of a step-by-step rolling device for titanium alloy screws.

[0025] Figure 3 This is a schematic diagram of the spacing adjustment mechanism in a step-by-step rolling equipment for titanium alloy screws.

[0026] Figure 4 This is a schematic diagram of the transverse moving component in a step-by-step rolling device for titanium alloy screws.

[0027] Figure 5 This is a schematic diagram of the contact structure between the drive wheel and the drive belt in a step-by-step rolling device for titanium alloy screws.

[0028] Figure 6 This is a schematic diagram of the contact structure between the extrusion roller and the drive belt in a step-by-step rolling device for titanium alloy screws.

[0029] Figure 7 for Figure 6The front view.

[0030] Figure 8 This is a schematic diagram of the structure of the first and second connecting rods in a step-by-step rolling device for titanium alloy screws.

[0031] Figure 9 This is a schematic diagram of the material lifting mechanism in a step-by-step rolling equipment for titanium alloy screws.

[0032] Figure 10 for Figure 9 The right view.

[0033] Figure 11 This is a schematic diagram of the nozzle structure in a step-by-step rolling device for titanium alloy screws.

[0034] In the diagram: 1. Bed support; 2. Center distance adjustment mechanism; 3. Workpiece support mechanism; 4. Fixed side crossbeam; 5. Movable side crossbeam; 6. Screw blank; 7. Rotary drive mechanism; 8. Drive mounting plate; 9. Belt drive device; 10. Lead screw nut seat; 11. Feed servo motor; 12. Crossbeam suspension mounting plate; 13. Guide rod; 14. Buffer spring; 15. Transverse lead screw; 16. Push plate; 17. Radial feed assembly; 18. Side plate; 19. Spindle; 20. Thread rolling wheel; 21. Driven gear; 22. Suspension... 23. Hanger; 24. Sliding rod; 25. Return spring; 26. Driven pulley; 27. Rotary motor; 28. Drive pulley; 29. ​​Drive belt; 30. Input shaft; 31. Drive wheel; 32. Extrusion roller; 33. Deflection arm; 34. Rotating seat; 35. Drive gear; 36. Transmission gear; 37. First connecting rod; 38. Second connecting rod; 39. Fixed block; 40. Sliding block; 41. Fixed rod; 42. Lifting sleeve; 43. Extension frame; 44. Material support plate; 45. Mounting frame; 46. Nozzle; 47. Fixed bracket. Detailed Implementation

[0035] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] In one embodiment, see Figure 1 A step-by-step rolling mill for titanium alloy screws is described. The overall structure mainly consists of six core components: a bed support 1, a center distance adjustment mechanism 2, a workpiece support mechanism 3, a rotary drive mechanism 7, and a cooling airflow assembly. It can realize a composite rolling process that combines radial step-by-step feeding with circumferential micro-reverse pressure relief for titanium alloy screws. It is especially suitable for mass production processing of TC4 titanium alloy precision fasteners with specifications from M3 to M16.

[0037] The bed support 1 is the load-bearing base of the whole machine. It is preferably made of ductile iron integral casting and stress relief aging treatment. It has high rigidity and excellent vibration resistance, which can effectively resist the large reaction force generated during the rolling of titanium alloy, and ensure the long-term stability and accuracy of the machining process.

[0038] In one embodiment, the center distance adjustment mechanism 2 is used to adjust the center distance between the two thread rolling wheels 20 to adapt to screw blanks 6 of different specifications and to perform radial feed action of step rolling.

[0039] The center distance adjustment mechanism 2 includes a fixed side crossbeam 4 and a movable side crossbeam 5. The fixed side crossbeam 4 is fastened to the left side of the bed support 1 by high-strength bolts, and the movable side crossbeam 5 is slidably installed on the right side of the bed support 1 by a high-precision linear guide pair. It can slide back and forth along the radial direction of the center line connecting the two thread rolling wheels 20. The linear guide pair provides precise guidance for the feed movement of the movable side crossbeam 5, ensuring the straightness and repeatability of the feed movement.

[0040] Both the fixed side beam 4 and the movable side beam 5 have side plates 18 vertically fixed at their front and rear ends on their upper surfaces. A main shaft 19, horizontally oriented, is rotatably mounted on the upper end of each side plate 18 via a heavy-duty precision angular contact ball bearing. The two main shafts 19 are arranged at the same height, with radial runout controlled within 0.005 mm. Two thread rolling wheels 20 are coaxially fixed to the middle of the two main shafts 19 via expansion sleeves. The thread rolling wheels 20 are preferably made of high-cobalt high-speed steel M35, coated with a TiAlN coating, achieving a hardness of HRC64-66, suitable for high-strength rolling applications on titanium alloys, and possessing excellent wear resistance and anti-titanium adhesion properties.

[0041] Gear transmission assemblies are installed at the rear ends of both spindles 19 to achieve synchronous reverse rotation of the double thread rolling wheels 20 and ensure that the transmission ratio remains constant during the center distance adjustment process, thereby solving the problem that traditional fixed center distance gear transmission cannot be adapted to feed adjustment.

[0042] Both spindles 19 have identical driven gears 21 connected to their rear ends by a key. The two driven gears 21 have the same module, number of teeth, and pressure angle, ensuring that the output speed is strictly consistent under the same input conditions. A fixed block 38 is fixedly installed on the left side of the rear side of the bed support 1. A horizontally positioned input shaft 29 is rotatably connected to the fixed block 38 via a precision rolling bearing. A drive gear 34 is keyed to the rear end of the input shaft 29. The drive gear 34 meshes with the driven gear 21 located on the fixed side on the left, forming a fixed-side transmission chain.

[0043] The right end of the second connecting rod 37 is rotatably sleeved at the rear end of the main shaft 19 located on one side of the movable side beam 5. The left end of the second connecting rod 37 is rotatably connected to the right end of the first connecting rod 36 via a pin. The left end of the first connecting rod 36 is rotatably sleeved on the input shaft 29. The first connecting rod 36 and the second connecting rod 37 together form a hinged linkage mechanism that can adaptively swing with changes in center distance. Self-lubricating bearings are installed at each pin to ensure flexible swing without jamming.

[0044] A transmission gear 35 is rotatably mounted on the middle of the second connecting rod 37 via a pin. The transmission gear 35 simultaneously meshes with both the driven gear 21 and the driving gear 34 located on the right movable side. When the center distance of the movable side crossbeam 5 changes by sliding radially, the angle between the first connecting rod 36 and the second connecting rod 37 automatically adjusts according to the center distance change, ensuring that the transmission gear 35 always maintains the correct meshing relationship with the gears on both sides and a constant center distance. Therefore, within the entire stroke center distance adjustment range, the transmission ratio of the two main shafts 19 remains constant, their speeds are completely synchronized, and their directions of rotation are always opposite, completely avoiding problems such as asynchronous speeds of the two wheels, misaligned threads, and pitch deviations caused by changes in center distance.

[0045] The radial feed assembly 17 is used to drive the movable side beam 5 to slide precisely in the radial direction and perform multi-pass feed actions for step-by-step rolling. It is the core actuator for realizing radial step-by-step forming.

[0046] A drive mounting plate 8 with a front-to-back orientation is fixedly installed at the right end of the bed support 1. A crossbeam suspension mounting plate 12 is fixedly connected to the lower left side of the drive mounting plate 8. A lead screw nut seat 10 is rotatably mounted at the center of the crossbeam suspension mounting plate 12 via a precision bearing seat. A horizontally arranged transverse lead screw 15 is internally threaded onto the lead screw nut seat 10. The precision grade of the transverse lead screw 15 is preferably C3 to ensure feed positioning accuracy.

[0047] The left end of the transverse lead screw 15 is rotatably connected to a push plate 16 via a combination support structure of a thrust bearing and a deep groove ball bearing. The push plate 16 is fixedly connected to the bottom of the movable side beam 5 by high-strength bolts. When the lead screw nut seat 10 rotates under external power, the transverse lead screw 15 translates axially, pushing the push plate 16 and the movable side beam 5 to move synchronously, thereby converting the rotational motion of the lead screw nut pair into the linear feed motion of the movable side beam 5.

[0048] Two horizontal guide rods 13 are symmetrically fixed on the front and rear sides of the push plate 16. The guide rods 13 slide through the corresponding oil-free bushing guide holes on the crossbeam suspension mounting plate 12, providing precise guidance for radial feed and preventing the push plate 16 and the movable side crossbeam 5 from deflecting during the feed process. Two buffer springs 14 are provided between the push plate 16 and the crossbeam suspension mounting plate 12, and the buffer springs 14 are respectively sleeved on the outside of the two guide rods 13. When instantaneous impact loads are generated during the titanium alloy rolling process, the buffer springs 14 absorb the impact energy through elastic deformation, improve the smoothness of the feed motion, and protect the transverse lead screw 15 and related bearing components from impact damage.

[0049] A feed servo motor 11 is fixedly mounted on the upper center of the drive mounting plate 8. The feed servo motor 11 is equipped with an absolute encoder, and the positioning accuracy can reach ±0.001mm. The output shaft of the feed servo motor 11 is connected to the lead screw nut seat 10 through a belt drive device 9. The feed servo motor 11 can precisely control the rotation angle and speed, and then precisely control the feed position, feed speed and holding pressure state of the movable side beam 5 through the lead screw nut pair. It supports flexible programming settings of process parameters for multiple stages such as pre-rolling, main forming and finishing, and meets the precise control requirements of radial feed for step-by-step rolling process.

[0050] In one embodiment, the rotary drive mechanism 7 provides rotational power to the thread rolling wheel 20 and can quickly switch between forward and reverse rotation to achieve circumferential micro-reverse pressure relief. The rotary drive mechanism 7 adopts a technical solution of "main motor unidirectional continuous operation + extrusion roller 31 switching and reversing", which avoids the impact load caused by frequent reversing of the large inertia transmission system, and has a fast reversing response speed, which is suitable for the short cycle action requirements of step-by-step pressure relief.

[0051] A rotary motor 26 is fixedly mounted on the bottom of the fixed side crossbeam 4. The rotary motor 26 is preferably a variable frequency speed-regulating three-phase asynchronous motor, which can achieve stepless speed regulation within the range of 30 to 120 rpm. The output shaft of the rotary motor 26 is coaxially fixedly connected to a drive pulley 27.

[0052] A suspension bracket 22 is fixedly installed on the side of the bed support 1 near the movable side beam 5 (i.e., the right rear position). A sliding rod 23 slides vertically through the suspension bracket 22, and a driven pulley 25 is rotatably mounted on the upper end of the sliding rod 23. A return spring 24 is sleeved on the outside of the sliding rod 23. The upper end of the return spring 24 abuts against the lower end face of the bearing seat of the driven pulley 25, and the lower end abuts against the upper surface of the suspension bracket 22. Under the elastic restoring force of the return spring 24, the sliding rod 23 always tends to slide towards the side where the movable side beam 5 is located (i.e., upwards), thereby automatically tensioning the drive belt 28, compensating for the elongation of the belt due to wear and temperature changes during use, and ensuring stable transmission efficiency.

[0053] The drive belt 28 is preferably a high-strength rubber synchronous transmission belt, tensioned and wound between the driving pulley 27 and the driven pulley 25, and driven by the rotary motor 26 to continuously cycle in one direction without the need for reversing. This arrangement avoids the current surge caused by the forward and reverse rotation of the rotary motor 26 and the alternating load loss of the mechanical transmission components.

[0054] A drive wheel 30 and a pressing roller 31 are arranged above the upper horizontal section of the drive belt 28, with the two spaced back and forth along the running direction of the drive belt 28. The drive wheel 30 is coaxially fixedly mounted on the front end of the input shaft 29 and rotates synchronously with the drive gear 34. Under normal forward rolling conditions, the lower surface of the drive wheel 30 abuts against the upper surface of the drive belt 28, and the drive belt 28 drives it to rotate forward through friction, which in turn drives the double thread rolling wheel 20 to rotate synchronously in the opposite direction through the gear transmission assembly.

[0055] A rotating base 33 is fixedly installed on the upper front end of the suspension frame 22. A deflection arm 32 is rotatably connected to the rotating base 33, and the extrusion roller 31 is rotatably installed on the upper end of the deflection arm 32. The deflection arm 32 is driven to swing by a micro servo cylinder, which can drive the extrusion roller 31 to quickly switch between the raised position and the pressed position, with an action response time of no more than 0.2s.

[0056] When a circumferential micro-reverse pressure relief action is required, the deflection arm 32 swings downward, causing the extrusion roller 31 to press down and abut against the upper surface of the drive belt 28, bending the drive belt 28 downward and causing local deformation. At this time, the extrusion roller 31 rotates under the frictional force of the drive belt 28, and the outer circumferential surface of the extrusion roller 31 simultaneously rubs against the outer circumferential surface of the drive wheel 30. Through friction transmission, the drive wheel 30 rotates in the opposite direction to the forward direction, and then drives the double thread rolling wheel 20 to synchronously reverse slightly through the gear transmission chain. By controlling the pressing and holding time of the deflection arm 32, the number of reverse rotations can be precisely controlled (usually 0.5 to 1.5 rotations), thereby achieving precise quantitative release of circumferential shear residual stress.

[0057] In this solution, the rotary motor 26 operates in one direction throughout the entire process, with fast reversing response and no obvious mechanical impact. It is suitable for the short-term pressure relief requirements between each pass of the step-by-step rolling process, effectively solving the problem that traditional flywheel drive thread rolling machines cannot achieve rapid micro-reversal.

[0058] In one embodiment, the workpiece support mechanism 3 is used to support the screw blank 6, so as to achieve precise positioning of the workpiece in the rolling station and ensure the coaxiality of the workpiece during initial engagement.

[0059] The workpiece support mechanism 3 is located on the front side of the bed support 1 (i.e., the side away from the rotary drive mechanism 7), and includes a sliding block 39. The sliding block 39 is slidably connected to the front side of the bed support 1 via a horizontal guide rail, and its position can be adjusted along the workpiece axis. It is fixed in place by locking screws after adjustment to accommodate screw blanks 6 of different lengths. A fixing rod 40 is vertically fixed on the sliding block 39, and a lifting sleeve 41 is slidably sleeved on the fixing rod 40. The lifting sleeve 41 can be raised and lowered along the fixing rod 40 to adjust its height, and is locked in place by side locking screws to accommodate screw blanks 6 of different diameters, ensuring that the center of the workpiece is at the same height as the center of the two thread rolling wheels 20.

[0060] The upper end of the lifting sleeve 41 is fixedly connected to a horizontally extending rearward extension frame 42, and a material support plate 43 is provided at the rear end of the extension frame 42. The material support plate 43 is preferably made of polytetrafluoroethylene (PTFE), which has a low coefficient of friction, effectively preventing the titanium alloy screw blank 6 from sticking and being scratched during the support and rolling process. The upper surface of the material support plate 43 is higher than the upper surface of the extension frame 42, and the height difference between the two forms a vertical limiting step at the connection point. When the screw blank 6 is placed on the material support plate 43, its head end face abuts against this limiting step, achieving precise axial positioning and preventing axial movement of the screw blank 6 during the rolling process. Preferably, the upper surface of the material support plate 43 is a concave arc surface adapted to the diameter of the screw blank 6 to improve the stability of radial positioning.

[0061] In one embodiment, the cooling airflow assembly is used to cool and lubricate the rolling processing area and apply downward airflow pressure to suppress workpiece bouncing, thus partially replacing the constraint function of a traditional rigid support plate.

[0062] A fixed bracket 46 is fixedly installed on the side of the bed support 1 (specifically, its left end). The fixed bracket 46 is preferably a multi-degree-of-freedom adjustable bracket, allowing for flexible adjustment of the position, height, and spray angle of the nozzle 45 to adapt to the processing requirements of screw blanks 6 of different specifications. A mounting bracket 44 is fixed to the upper part of the fixed bracket 46, extending to the right directly above the center of the two thread rolling wheels 20, with a cooling atomizing nozzle 45 installed at its lower end.

[0063] The nozzle 45 sprays vertically downwards towards the rolling forming area of ​​the screw blank 6, spraying a high-pressure atomized airflow mixed with extreme pressure rolling oil. During operation, on the one hand, the high-speed atomized airflow directly impacts the rolling interface, carrying away the heat of plastic deformation and friction, effectively controlling the temperature rise of the thread rolling wheel 20 and the screw blank 6, and suppressing the tendency of titanium alloy material to stick to the mold at high temperatures; on the other hand, the high-pressure airflow generates a downward uniform dynamic pressure on the surface of the screw blank 6, counteracting the upward rebound force of the screw blank 6 during the rolling process, suppressing its radial runout, thereby significantly reducing the dependence on the rigid support plate 43 and reducing the risk of friction and scratches between the support plate 43 and the titanium alloy screw blank 6.

[0064] The following describes in detail the workflow and process logic of the step-by-step rolling equipment of the present invention, taking into account the complete machining process of TC4 titanium alloy M6×1.0 screws.

[0065] Step 1: Power-on preparation and parameter settings

[0066] Based on the specifications of the screw to be processed, the axial position of the workpiece support mechanism 3 and the height of the support plate 43 are first adjusted so that the center of the screw blank 6 is at the same height as the center of the two thread rolling wheels 20, and the head of the screw blank 6 can accurately abut against the limiting step formed at the connection between the support plate 43 and the extension frame 42. At the same time, the initial position of the movable side beam 5 is adjusted by the feed servo motor 11 so that the initial distance between the two thread rolling wheels 20 is 0.5 to 1 mm greater than the diameter of the screw blank 6, so that the screw blank 6 can be smoothly fed into the forming station.

[0067] The step-by-step rolling process parameters are entered into the CNC system, specifically including: pre-rolling feed depth of 35% of the total tooth depth, 4 pre-rolling passes, radial micro-retraction of 0.05mm, 1 circumferential micro-reversal pass, main forming feed depth of 90% of the total tooth depth, 6 main forming passes, finishing feed depth as the final design dimension, and 3 finishing pressure holding passes. Simultaneously, the working air pressure of nozzle 45 is set to 0.6MPa, and the rolling oil atomization flow rate is set to 50mL / h.

[0068] Step 2: Loading and Positioning

[0069] The rotary motor 26 starts, driving the drive belt 28 to continuously circulate in one direction. At this time, the deflection arm 32 is in the raised state, the extrusion roller 31 is disengaged from the drive belt 28, the lower surface of the drive wheel 30 abuts against the upper surface of the drive belt 28 and rotates in the forward direction. Through the gear transmission chain composed of the drive gear 34, the transmission gear 35 and the driven gear 21, the two thread rolling wheels 20 are driven to rotate synchronously in opposite directions at a low speed, with the speed set at 60 rpm.

[0070] The screw blank 6 is placed on the support plate 43 by a person or a feeding robot. The head end face of the screw blank 6 is axially positioned against the limiting step, while the shank is placed in the forming station between the two thread rolling wheels 20. At the same time, the nozzle 45 is opened simultaneously, continuously spraying high-pressure atomized airflow into the rolling area.

[0071] Step 3: Pre-roll forming

[0072] The feed servo motor 11 starts, driving the lead screw nut seat 10 to rotate via the belt drive device 9, which in turn drives the transverse lead screw 15 to advance uniformly to the left, pushing the movable side beam 5 to feed smoothly radially. The gap between the two thread rolling wheels 20 gradually decreases, and the tooth profile of the thread rolling wheels 20 gradually presses into the surface material of the screw blank 6.

[0073] When the feed reaches the pre-rolling set depth (i.e., 35% of the total tooth depth), the feed servo motor 11 stops feeding and maintains its current position, while the thread rolling wheel 20 continues to rotate and roll for 4 revolutions. This stage completes the initial tooth profile guidance, pressing continuous shallow tooth grooves into the surface of the screw blank 6, pre-opening a channel for the plastic flow of metal, guiding the metal material to flow orderly along the tooth profile direction, avoiding the disordered folding of metal caused by subsequent large single deformation, and at the same time weakening the initial work hardening effect, creating favorable plastic conditions for subsequent main forming.

[0074] Step 4: First-stage composite pressure relief

[0075] After pre-rolling is completed, the feed servo motor 11 rotates in the opposite direction, causing the movable side beam 5 to retract radially by 0.05mm, releasing the elastic compressive stress accumulated in the radial direction of the screw blank 6. During the retraction process, the tooth profile of the thread rolling wheel 20 and the shallow tooth groove already formed on the screw blank 6 remain engaged, and the screw blank 6 does not undergo circumferential deflection, thereby avoiding the risk of misalignment during subsequent re-engagement.

[0076] After the radial micro-retraction is completed, the micro servo cylinder drives the deflection arm 32 to swing downwards, causing the extrusion roller 31 to press down against the upper surface of the drive belt 28, bending the drive belt 28 downwards. At this time, the extrusion roller 31 rotates under the friction of the drive belt 28, and the outer circumferential surface of the extrusion roller 31 rubs against the outer circumferential surface of the drive wheel 30. Through friction transmission, the drive wheel 30 rotates in the opposite direction, which in turn drives the two thread rolling wheels 20 to rotate synchronously in the opposite direction for one revolution via the gear transmission chain. This circumferential micro-reversal process releases the circumferential shear residual stress on the tooth profile surface, promotes the relaxation of the distorted lattice, further weakens the work hardening effect, and provides more favorable plastic conditions for subsequent main forming.

[0077] After the reversal is completed, the deflection arm 32 quickly returns to its original position, the extrusion roller 31 disengages from the drive belt 28, the drive wheel 30 resumes forward rotation, and the thread rolling wheel 20 returns to the forward rotation state, ready to enter the next pass.

[0078] Step 5: Main forming roll forming

[0079] The feed servo motor 11 feeds forward again, pushing the movable side beam 5 forward to the main forming set depth "that is, 90% of the total tooth depth" and maintaining this position, while the thread rolling wheel 20 continues to roll for 6 revolutions. This stage completes the forming of most of the tooth depth. The metal material flows smoothly in the groove guided by the pre-rolling stage, greatly improving the fullness of the tooth filling and the uniform transition of the tooth bottom arc.

[0080] Step Six: Second Stage Composite Pressure Relief

[0081] Repeat the compound pressure relief action of step four: the feed servo motor 11 drives the movable side beam 5 to retract radially by 0.04mm, and then the micro servo cylinder drives the deflection arm 32 to press down. Through the friction transmission between the extrusion roller 31 and the drive wheel 30, the thread rolling wheel 20 is rotated slightly circumferentially by 0.8 turns. This stage further releases the work hardening and residual stress accumulated during the main forming process, eliminates stress concentration inside the tooth profile, and lays the foundation for the dimensional stability of the final finishing process.

[0082] Step 7: Finishing and Pressure Holding

[0083] The feed servo motor 11 performs the third feed, pushing the movable side beam 5 to the final tooth depth dimension, and maintaining constant pressure at this position for 3 rounds of pressure rolling. This stage aims to calibrate the final tooth profile, compensate for the elastic rebound of the titanium alloy material after unloading, correct the tooth surface roughness, ensure the accuracy of the thread pitch diameter and the integrity of the tooth profile, and make the thread accuracy stably reach the 4h grade standard.

[0084] Step 8: Retract the blade and unload the material.

[0085] After the finishing and pressure holding are completed, the feed servo motor 11 quickly reverses direction, driving the movable side beam 5 back to its initial large-pitch position, and the two thread rolling wheels 20 completely disengage from the formed screw. The nozzle 45 closes after a 2-second delay, using the continuous jetting airflow to blow away the residual rolling oil mist on the workpiece surface. Afterward, the finished titanium alloy screw is removed from the support plate 43 by manual labor or a material unloading robot, completing one full processing cycle.

[0086] The above steps are executed automatically and sequentially under the unified scheduling of the CNC system, realizing the three-stage, five-action composite step-by-step rolling process of titanium alloy screws from blank to finished thread: "pre-rolling - pressure relief - main forming - pressure relief - finishing".

[0087] Implementation effect verification

[0088] This equipment was used for batch roll forming of TC4 titanium alloy M6×1.0 screws. Comparative tests were conducted with traditional single-pass thread rolling machines. Verified by a third-party testing agency, the core performance indicators are as follows:

[0089] 1. Defect rate: The defect rate of thread folds and microcracks has been reduced from 23% in the traditional process to less than 2%, and the pass rate of magnetic particle testing and penetrant non-destructive testing is not less than 98%;

[0090] 2. Dimensional accuracy: The tolerance of the thread pitch diameter is stably controlled within the 4h grade, and the consistency deviation of the pitch diameter in batch production does not exceed 0.008mm;

[0091] 3. Mechanical properties: The residual tensile stress at the thread root is reduced by 42% compared with the traditional process, and the axial fatigue life is increased by more than 35%;

[0092] 4. Die life: The average service life of the thread rolling wheel 20 is increased by 32%, and the titanium bonding grinding cycle is extended by 40%.

[0093] This invention provides a step-by-step rolling device for titanium alloy screws. Through a rotating drive mechanism 7, the drive wheel 30 and the extrusion roller 31 alternately abut against a unidirectional, continuously rotating drive belt 28. This allows for rapid forward and reverse switching of the rolling wheel 20 without requiring the rotary motor 26 to reverse. This enables a circumferential micro-reverse pressure relief action after each radial feed pass, effectively releasing the circumferential shear residual stress in the titanium alloy thread profile, weakening the work hardening effect, and eliminating thread folding and internal folding defects caused by insufficient material flowability. Simultaneously, through an adaptive articulated transmission structure composed of the first connecting rod 36, the second connecting rod 37, and the transmission gear 35, a constant transmission ratio of the dual spindle 19 gears is maintained throughout the entire stroke of the radial sliding adjustment of the center distance on the movable side beam 5. The rotational speeds of the dual rolling wheels 20 are strictly synchronized, effectively suppressing cumulative pitch errors and thread asymmetry caused by changes in center distance. Combined with a servo screw-driven radial feed assembly 17, multi-pass step-by-step progressive deformation is achieved, significantly reducing fluctuations in the thread pitch diameter and achieving a stable accuracy of 4h level.

[0094] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

Claims

1. A step-by-step rolling device for titanium alloy screws, comprising a bed support, wherein synchronously counter-rotating thread rolling wheels are arranged on both sides of the bed support, characterized in that, It also includes a center distance adjustment mechanism, a workpiece support mechanism, and a rotary drive mechanism; The center distance adjustment mechanism includes a fixed side beam and a movable side beam disposed on both sides of the bed support. The ends of the fixed side beam and the movable side beam are provided with side plates, and the side plates are rotatably connected to a main shaft coaxially disposed with the thread rolling wheel. A workpiece support mechanism is used to support the screw blank to be rolled between the two thread rolling wheels; The rotary drive mechanism includes a drive belt located at the bottom of the bed support and with an adjustable rotation direction. A drive wheel and a pressing roller are arranged above the drive belt. The drive wheel and the pressing roller alternately abut against the drive belt. The drive wheel and the thread rolling wheel rotate synchronously. When the pressing roller abuts against the drive belt, the pressing roller abuts against the drive wheel and rotates synchronously.

2. The titanium alloy screw step-by-step rolling equipment according to claim 1, characterized in that, A driven gear is provided at the end of the main shaft. A fixed block is fixedly connected to the side of the bed support near the fixed side beam. An input shaft is rotatably connected to the fixed block. A drive gear is fixedly connected to the end of the input shaft. The drive gear meshes with the driven gear near the fixed side beam. One end of a second connecting rod is rotatably connected to the main shaft near the movable side beam. The other end of the second connecting rod is rotatably connected to one end of a first connecting rod. The other end of the first connecting rod is rotatably connected to the input shaft. A transmission gear is provided at the rotation center of the first and second connecting rods and is rotatably connected to the side of the second connecting rod. One side of the transmission gear meshes with the driven gear near the movable side beam, and the other side of the transmission gear meshes with the drive gear. The two driven gears rotate at the same speed.

3. The titanium alloy screw step-by-step rolling equipment according to claim 2, characterized in that, A suspension frame is fixedly connected to the side of the bed support near the movable side crossbeam. A sliding rod is slidably connected to the suspension frame. A driven pulley is rotatably connected to the side of the sliding rod near the movable side crossbeam. A return spring is sleeved on the outside of the sliding rod to drive the sliding rod to move toward the movable side crossbeam. A rotary motor is provided at the bottom of the fixed side crossbeam. A drive pulley is fixedly connected to the output shaft of the rotary motor. The drive belt is tensioned between the drive pulley and the driven pulley.

4. The titanium alloy screw step-by-step rolling equipment according to claim 3, characterized in that, The end of the suspension frame is provided with a rotating seat, and the rotating seat is rotatably connected to a deflection arm. The extrusion roller is rotatably connected to the end of the deflection arm.

5. The titanium alloy screw step-by-step rolling equipment according to claim 1, characterized in that, The fixed side crossbeam is fixedly connected to the bed support, the movable side crossbeam is slidably connected to the bed support, and a radial feed assembly for driving the movable side crossbeam is provided at one end of the bed support near the movable side crossbeam.

6. The titanium alloy screw step-by-step rolling equipment according to claim 5, characterized in that, The radial feed assembly includes a drive mounting plate fixedly connected to the bed support. A crossbeam suspension mounting plate is provided at the bottom of the drive mounting plate. A lead screw nut seat is rotatably connected to the middle of the crossbeam suspension mounting plate. A transverse lead screw is threadedly connected to the middle of the lead screw nut seat. A push plate fixedly connected to the movable side crossbeam is rotatably connected to the end of the transverse lead screw.

7. The titanium alloy screw step-by-step rolling equipment according to claim 6, characterized in that, The push plate has guide rods on both sides that are slidably connected to the crossbeam suspension mounting plate. A buffer spring is provided between the push plate and the crossbeam suspension mounting plate and sleeved on the outside of the guide rod. A feed servo motor is provided in the middle of the drive mounting plate. The output shaft of the feed servo motor is connected to the lead screw nut seat through a belt drive device.

8. The titanium alloy screw step-by-step rolling equipment according to claim 1, characterized in that, The workpiece support mechanism is located on the side of the bed support away from the rotary drive mechanism. The workpiece support mechanism includes a sliding block that is slidably connected to the bed support. A fixed rod is provided on the sliding block. A lifting sleeve is slidably connected to the fixed rod. An extension frame is fixedly connected to the end of the lifting sleeve. A support plate is provided at one end of the extension frame near the center of the bed support. The upper surface of the support plate is higher than the upper surface of the extension frame. The connection between the support plate and the extension frame forms a step for positioning the screw blank.

9. The titanium alloy screw step-by-step rolling equipment according to claim 1, characterized in that, A fixed bracket is provided on the side of the bed support, and a mounting bracket is provided above the fixed bracket. A nozzle that blows high-speed airflow toward the screw blank is provided on the mounting bracket near the middle of the two thread rolling wheels.

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