Ultrasonic-assisted additive manufacturing device for metal workpiece

Abstract

The invention discloses a device for ultrasonic-assisted additive manufacturing of a metal workpiece, and relates to the field of laser additive manufacturing, the device comprises a circular base plate, a plurality of transducers, a synchronous stretching mechanism, a supporting box, a vibration isolation mechanism, a bearing air cylinder, a first driving motor and an ultrasonic generator, the supporting box is rotationally installed on the vibration isolation mechanism, the first driving motor is used for driving the supporting box and the circular base plate fixed to the supporting box to rotate, and the bearing air cylinder is installed on the equipment base and located on the inner side of the vibration isolation mechanism. The piston end of the bearing air cylinder penetrates through the supporting box and then is connected with the synchronous stretching mechanism through a thrust bearing, the energy converter is installed at the movable end of the synchronous stretching mechanism through a floating constant force connector, and the energy converter is connected with an ultrasonic generator through a high-frequency coaxial cable. The mechanical property of the annular rotary part during laser additive manufacturing can be improved by synchronously changing the position of the transducer.

Description

Technical Field

[0001] This invention belongs to the field of laser additive manufacturing, and specifically relates to an apparatus for ultrasonic-assisted additive manufacturing of metal workpieces. Background Technology

[0002] Metal additive manufacturing technology, particularly selective melting and direct energy deposition (DED) using lasers as energy sources, has shown great application potential in aerospace, biomedicine, and other fields due to its ability to achieve near-net-shape forming of complex structural parts. However, the inherent rapid melting and solidification process of this technology results in formed parts typically possessing a coarse columnar crystal microstructure with significant elemental segregation. This microstructure characteristic often leads to additively manufactured components exhibiting lower overall mechanical properties, particularly ductility, fatigue strength, and fracture toughness, compared to traditional forgings, thus limiting their widespread application in critical load-bearing components.

[0003] To improve the microstructure of additively manufactured metals, researchers have introduced external field-assisted techniques, among which ultrasonic vibration is considered an effective method. The cavitation and acoustic flow effects generated by ultrasound in the molten pool can effectively break up dendrites and promote nucleation, thereby refining grains, reducing segregation, and obtaining an equiaxed fine-grained structure, which is expected to comprehensively improve the mechanical properties of parts.

[0004] However, existing technologies face significant challenges when applying ultrasonic vibration to additive manufacturing of toroidal rotary parts. First, scanning the toroidal path typically requires rotation of the substrate or laser head, and traditional ultrasonic transducer mounting methods struggle to ensure a uniform and stable sound field across the entire toroidal molten pool during rotation. Second, for toroidal parts of varying diameters, there is a lack of effective techniques to precisely focus ultrasonic energy on the molten pool region, resulting in uneven ultrasonic processing and poor consistency in part microstructure and properties. Furthermore, if the microstructure of large toroidal components is substandard after forming, subsequent modification processes such as heat treatment are costly, time-consuming, or even impossible, severely hindering the industrial application of large, high-performance toroidal components.

[0005] Therefore, how to provide an ultrasonic-assisted additive manufacturing device for metal workpieces suitable for ring-shaped and rotating parts has become a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides an apparatus for ultrasonic-assisted additive manufacturing of metal workpieces. By synchronously changing the position of the transducer, the present invention enables ultrasonic energy to always act precisely below the moving molten pool formed by laser scanning, which significantly improves the comprehensive mechanical properties of annular and rotating parts.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: An apparatus for ultrasonic-assisted additive manufacturing of metal workpieces includes a circular substrate, several transducers, a synchronous extension mechanism, a support box, a vibration isolation mechanism, a load-bearing cylinder, a first drive motor, and an ultrasonic generator. The vibration isolation mechanism is mounted on a base, and the support box is rotatably mounted on the vibration isolation mechanism. The first drive motor drives the support box and the circular substrate fixed on the support box to rotate. The load-bearing cylinder is mounted on the base and located inside the vibration isolation mechanism. The piston end of the load-bearing cylinder passes through the support box and is connected to the synchronous extension mechanism via a thrust bearing. The transducers are mounted on the movable end of the synchronous extension mechanism via floating constant force connectors. The synchronous extension mechanism can drive several transducers thereon to move synchronously along the radial direction of the circular substrate. The transducers are connected to the ultrasonic generator via high-frequency coaxial cables.

[0008] Furthermore, the synchronous extension mechanism includes a circular base plate, a gear ring, a sliding mounting plate, a long gear, and a second drive motor. The circular base plate has a central hole in its center. The upper surface of the circular base plate has an outer ring protrusion and an inner ring protrusion concentrically arranged. An annular groove is provided on the inner side of the outer ring protrusion. The gear ring is rotatably disposed in the annular groove. The outer ring protrusion and the inner ring protrusion are respectively provided with a sliding groove along the circumference of the center of the circular base plate. The sliding mounting plate is slidably limited in the sliding groove. The floating constant force connector is fixed on the sliding mounting plate. A rack is provided on one side of the sliding mounting plate. The long gear is rotatably disposed on the circular base plate and meshes with the gear ring and the sliding mounting plate respectively. The second drive motor is installed at the bottom of the circular base plate and is used to drive the rotation of any long gear.

[0009] Furthermore, it also includes a limiting mechanism, which includes several limiting shafts and heavy-duty linear bearings. The limiting shafts are circumferentially fixed to the lower surface of the circular base plate, and the heavy-duty linear bearings are installed on the outer edge of the circular base plate corresponding to the limiting shafts. The limiting shafts are inserted into the heavy-duty linear bearings.

[0010] Furthermore, the floating constant force connector includes a housing base, a preload spring, a floating shaft, a spherical washer assembly, and an elastic vibration damping ring; the housing base is fixed to the sliding mounting plate; the floating shaft is axially slidably confined within the housing base via a linear bearing; the preload spring is disposed within the housing base and its two ends abut against the housing base and the floating shaft respectively, providing a constant upward pre-lift force for the floating shaft; a stud is provided at the upper end of the floating shaft, and the spherical washer assembly and the elastic vibration damping ring are sequentially sleeved on the stud and tightened by a lock nut; the transducer is fixedly connected to the metal mounting surface of the elastic vibration damping ring.

[0011] Furthermore, it also includes a displacement sensor, which is mounted on a sliding mounting plate on one side of the floating constant force connector, for monitoring the displacement of the transducer.

[0012] Furthermore, the piston rod of the load-bearing cylinder is connected to a stepped shaft at its top end. The center of the stepped shaft has a through hole. The thrust bearing is sleeved on the stepped shaft, its seat ring is connected to the stepped shaft, and its shaft ring is connected to the synchronous extension mechanism.

[0013] Furthermore, it also includes a conductive slip ring, the rotor end of which is coaxially fixed to and rotates with the central part of the synchronous extension mechanism, and the stator end of which is fixed to the stepped shaft; the high-frequency coaxial cable of the transducer is connected to the rotor end of the conductive slip ring, and the ultrasonic generator is connected to the stator end of the conductive slip ring via a cable.

[0014] Furthermore, it also includes a cooling mechanism, which includes an annular cooling water jacket, a braided hose, and a multi-channel rotary joint. The annular cooling water jacket is made of copper and is fitted onto the transducer. It is connected to the multi-channel rotary joint via the braided hose. The multi-channel rotary joint is installed in the middle of the synchronous extension mechanism and fitted onto the stepped shaft. The multi-channel rotary joint is connected to the cooling system fixed to the equipment base.

[0015] Furthermore, the vibration isolation mechanism includes an external toothed crossed roller slewing bearing, a circular vibration isolation base, and several rubber vibration isolators. The outer ring of the external toothed crossed roller slewing bearing is fixedly connected to the support box, and the inner ring of the external toothed crossed roller slewing bearing is fixedly connected to the circular vibration isolation base. The several rubber vibration isolators are evenly arranged circumferentially. The lower end of each rubber vibration isolator is fixed to the equipment base, and the upper end is fixed to the circular vibration isolation base. The first drive motor and the reducer connected thereto are fixedly installed on the circular vibration isolation base. The output end of the reducer is provided with a drive gear that meshes with the gear ring on the outer ring of the external toothed crossed roller slewing bearing.

[0016] The present invention has the following significant beneficial effects: 1. This invention uses a load-bearing cylinder to tightly press the transducer assembly against a circular substrate, and a first drive motor to drive the substrate to rotate, thereby naturally causing all transducers to rotate synchronously. This ensures that ultrasonic energy is always precisely applied directly below the moving molten pool formed by laser scanning. Combined with a radially adjustable extension mechanism, regardless of the diameter of the annular part, the ultrasonic field can be uniformly covered throughout the forming path, effectively promoting grain nucleation and refinement within the molten pool, successfully transforming coarse columnar crystals into uniform equiaxed fine crystals, significantly improving the overall mechanical properties and isotropy of the part, and achieving precise, uniform, and efficient ultrasonic treatment of the molten pool of annular parts.

[0017] 2. This invention precisely controls the synchronous extension mechanism via a second drive motor, enabling rapid and accurate adjustment of the radial positions of multiple transducers. This adapts to the manufacturing needs of annular, sector-shaped, and even eccentric parts of varying diameters. The introduction of displacement sensors allows for real-time monitoring of transducer float, providing a data foundation for closed-loop process control. This flexible design eliminates the need for custom-designed tools for different parts, making it highly suitable for modern production models involving multiple product types and small batches.

[0018] 3. The floating constant force connector of this invention integrates constant force application, universal self-alignment, and vibration damping, ensuring stable and reliable physical contact between the transducer and the substrate while effectively isolating high-frequency vibrations from being transmitted to precision mechanical components. An independent vibration isolation mechanism decouples the entire rotary table from the equipment base, preventing ultrasonic vibrations from affecting the accuracy of the laser optical path, powder feeding system, and other equipment. The integrated cooling mechanism and conductive slip ring design effectively solve the problems of energy transmission and thermal management during rotation, ensuring the system can operate stably for extended periods. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the main structure of the present invention; Figure 2 This is a schematic diagram of the internal structure of the device of the present invention; Figure 3 for Figure 2 The front view; Figure 4 This is a schematic diagram of the synchronous extension mechanism of the present invention; Figure 5 for Figure 3 Enlarged view of a portion of point A in the middle; Figure 6 This is a schematic diagram of the sliding mounting plate structure of the present invention; Figure 7 This is a schematic diagram of the floating constant force connector structure of the present invention; Figure 8 This is a cross-sectional view of the floating constant force connector of the present invention.

[0020] In the diagram: 1. Circular substrate; 2. Transducer; 3. Support box; 4. Load-bearing cylinder; 5. First drive motor; 6. Equipment base; 7. Thrust bearing; 8. Laser head; 9. Ring-shaped part; 10. Circular base plate; 11. Gear ring; 12. Sliding mounting plate; 13. Long gear; 14. Second drive motor; 15. Outer ring protrusion; 16. Inner ring protrusion; 17. Limiting shaft; 18. Heavy-duty linear bearing; 19. Housing base; 20. Preload spring; 21. Floating shaft; 22. Spherical washer assembly; 23. Elastic vibration damping ring; 24. Locking nut; 25. Displacement sensor; 26. Stepped shaft; 27. Conductive slip ring; 28. External toothed crossed roller slewing bearing; 29. ​​Circular vibration isolation base; 30. Rubber vibration isolator; 31. Drive gear. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0022] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "horizontal," "inner," "outer," and "one side," 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. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] Example 1

[0024] like Figure 1-8As shown, this embodiment discloses an apparatus for ultrasonic-assisted additive manufacturing of metal workpieces, including a circular substrate 1, several transducers 2, a synchronous extension mechanism, a support box 3, a vibration isolation mechanism, a load-bearing cylinder 4, a first drive motor 5, and an ultrasonic generator. The vibration isolation mechanism is mounted on the equipment base 6, and the support box 3 is rotatably mounted on the vibration isolation mechanism. The first drive motor is used to drive the support box 3 and the circular substrate 1 fixed on the support box to rotate. The circular substrate 1 is made of titanium alloy (TC4) or high-temperature nickel-based alloy, which has low acoustic impedance, high propagation efficiency, and can withstand the thermal cycle of the laser head 8 processing the ring-shaped part 9. The load-bearing cylinder 4 is mounted on the equipment base 6. The base 6 is located on the inner side of the vibration isolation mechanism. The piston end of the load-bearing cylinder 4 passes through the support box 3 and is connected to the synchronous extension mechanism through the thrust bearing 7. The transducer 2 is installed on the movable end of the synchronous extension mechanism through a floating constant force connector. The synchronous extension mechanism can drive several transducers 2 on it to move synchronously along the radial direction of the circular substrate 1. The transducer 2 is connected to the ultrasonic generator through a high-frequency coaxial cable. This invention organically combines rotational motion, radial adjustment and ultrasonic treatment, realizing comprehensive and uniform ultrasonic assistance for metal workpieces. It is particularly suitable for additive manufacturing of large or complex shaped workpieces and helps to improve the mechanical properties and dimensional stability of the workpiece.

[0025] As a key component of this invention, the synchronous extension mechanism includes a circular base plate 10, a gear ring 11, a sliding mounting plate 12, a long gear 13, and a second drive motor 14. A central hole is provided in the middle of the circular base plate 10. An outer ring protrusion 15 and an inner ring protrusion 16 are concentrically arranged on the upper surface of the circular base plate 10. An annular groove is provided on the inner side of the outer ring protrusion 15, and the gear ring 11 is rotatably disposed within the annular groove. Sliding grooves are provided around the center of the circular base plate 10, corresponding to the outer ring protrusion 15 and the inner ring protrusion 16. The sliding mounting plate 12 is slidably confined within the sliding grooves. The floating constant force connector is fixed... The transducer 2 is fixed on the sliding mounting plate 12. A rack is provided on one side of the sliding mounting plate 12, and a limit protrusion is provided on the other side to prevent it from falling out of the groove. The long gear 13 is rotatably mounted on the circular base plate 10 and meshes with the gear ring 11 and the sliding mounting plate 12 respectively. The second drive motor 14 is mounted on the bottom of the circular base plate 10 and is used to drive the rotation of any long gear 13. Through the meshing transmission of the gear ring 11, the long gear 13 and the sliding mounting plate 12, all transducers 2 are ensured to move radially synchronously, avoiding uneven processing caused by asynchrony and improving the position control accuracy.

[0026] As a preferred embodiment of the present invention, a limiting mechanism is also included. The limiting mechanism includes a plurality of limiting shafts 17 and heavy-duty linear bearings 18. The limiting shafts 17 are circumferentially fixed on the lower surface of the circular substrate 1. The heavy-duty linear bearings 18 are installed on the outer edge of the circular base plate 10 corresponding to the limiting shafts 17. The limiting shafts 17 are inserted into the heavy-duty linear bearings 18. The limiting shafts 17 are fixed under the circular substrate 1 and cooperate with the heavy-duty linear bearings 18 to effectively prevent the circular substrate 1 from shifting or vibrating when rotating at high speed, thereby improving the rigidity of the system. This mechanism restricts the degree of freedom of the circular substrate 1, ensures its alignment with the synchronous extension mechanism, reduces vibration during operation, and thus ensures the accuracy and repeatability of the ultrasonic action.

[0027] In a preferred embodiment of the present invention, the floating constant force connector includes a housing base 19, a preload spring 20, a floating shaft 21, a spherical washer assembly 22, and an elastic vibration damping ring 23. The housing base 19 is fixed to the sliding mounting plate 12. The floating shaft 21 is axially slidably limited within the housing base 19 by a linear bearing. The preload spring 20 is disposed within the housing base 19 and its two ends abut against the housing base 19 and the floating shaft 21, respectively. The preload spring 20 provides a constant upward preload force to the floating shaft 21, ensuring that the amplitude transformer of the transducer 2 maintains a constant contact force with the workpiece surface. Even if the workpiece surface is uneven, it can ensure stable transmission of ultrasonic energy and avoid overload or poor contact. The linear bearing provides high-precision guidance to prevent the transducer 2 from shaking during rotation. A stud is provided at the upper end of the floating shaft 21, and the spherical washer assembly 23... The transducer 2 and the elastic vibration damping ring 23 are sequentially sleeved on the stud and tightened by the locking nut 24. The transducer 2 is fixedly connected to the metal mounting surface of the elastic vibration damping ring 23. The spherical washer group 22 provides angle compensation. When the end face of the transducer 2 is not absolutely parallel to the lower surface of the circular substrate 1, a small relative sliding can occur between the spherical washers, allowing the connecting flange of the transducer 2 to have a small angle deflection (e.g., ±2°) relative to the floating shaft 21, thereby ensuring that the end face of the radiating head of the transducer 2 is in "face contact" with the substrate. In this embodiment, the elastic vibration damping ring 23 is made of special rubber or polyurethane with a high damping coefficient. After the high-frequency vibration transmitted from the transducer 2 reaches the connecting flange, it will be absorbed by the elastic damping ring and converted into heat energy, which greatly reduces the transmission of vibration to the synchronous extension mechanism.

[0028] As a preferred embodiment of the present invention, a displacement sensor 25 is also included. The displacement sensor 25 is mounted on the sliding mounting plate 12 and located on one side of the floating constant force connector, and is used to monitor the displacement of the transducer 2.

[0029] The piston rod of the load-bearing cylinder 4 is connected to a stepped shaft 26 at its top. The center of the stepped shaft 26 is located at a through hole. The thrust bearing 7 is sleeved on the stepped shaft 26, and its seat ring is connected to the stepped shaft 26. Its shaft ring is connected to the synchronous extension mechanism.

[0030] In a preferred embodiment of the present invention, a conductive slip ring 27 is also included. The rotor end of the conductive slip ring 27 is coaxially fixed to the central part of the synchronous extension mechanism and rotates therewith. The stator end of the conductive slip ring 27 is fixed to the stepped shaft 26. The high-frequency coaxial cable of the transducer 2 is connected to the rotor end of the conductive slip ring 27, and the ultrasonic generator is connected to the stator end of the conductive slip ring 27 via a cable. The conductive slip ring 27 solves the cable management problem in the rotating system, ensuring that the transducer 2 can work continuously during rotation without interruption. The high-frequency coaxial cable connection maintains the signal transmission quality and ensures stable output of ultrasonic energy.

[0031] As a preferred embodiment of the present invention, a cooling mechanism (not shown in the figure) is also included. The cooling mechanism includes an annular cooling water jacket, a braided hose, and a multi-channel rotary joint. The annular cooling water jacket is made of copper and is sleeved on the transducer 2. It is connected to the multi-channel rotary joint through the braided hose to achieve efficient heat exchange for the transducer 2, prevent the transducer 2 from overheating and being damaged, and maintain its optimal operating temperature. The multi-channel rotary joint is installed in the middle of the synchronous extension mechanism and sleeved on the stepped shaft 26 to avoid pipe kinking and achieve continuous cooling. The multi-channel rotary joint is connected to the cooling system fixed on the equipment base 6.

[0032] As a preferred embodiment of the present invention, the vibration isolation mechanism includes an external toothed crossed roller slewing bearing 28, a circular vibration isolation base 29, and several rubber vibration isolators 30. The rubber vibration isolators 30 can effectively attenuate the medium and high frequency vibrations transmitted from the support box 3, while also providing support to prevent it from overturning. The external toothed crossed roller slewing bearing 28 provides high-precision rotational support, bears radial and axial loads, and ensures that the support box 3 rotates smoothly. The outer ring of the external toothed crossed roller slewing bearing 28 is fixedly connected to the support box 3, and the inner ring of the external toothed crossed roller slewing bearing 28 is fixedly connected to the circular vibration isolation base 29. Several rubber vibration isolators 30 are evenly arranged circumferentially. The lower end of the rubber vibration isolator 30 is fixed to the equipment base 6, and the upper end is fixed to the circular vibration isolation base 29. The first drive motor 5 and the reducer connected thereto are fixedly installed on the circular vibration isolation base 29. The output end of the reducer is provided with a drive gear 31, which meshes with the gear ring on the outer ring of the external toothed crossed roller slewing bearing 28. The first drive motor 5 can drive the rotation of the support box 3 and the circular base plate 1 to complete the processing of the ring-shaped parts.

[0033] Example 2

[0034] The difference between this embodiment and Embodiment 1 is that this embodiment uses an internal gear cross roller slewing bearing, whose outer ring is fixedly connected to the circular vibration isolation base 29, and whose inner ring is fixedly connected to the support box 3. In this embodiment, the first drive motor 5 and the reducer are installed on the equipment base 6, located inside the circular vibration isolation base 29. The output end of the reducer is provided with a drive gear 31, which meshes with the gear ring on the inner ring of the internal gear cross roller slewing bearing. This avoids the exposed meshing gear pair and ensures the stability of gear meshing, avoiding noise, wear, or even tooth breakage caused by vibration.

[0035] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. An apparatus for ultrasonic-assisted additive manufacturing of metal workpieces, characterized in that, The device includes a circular substrate, several transducers, a synchronous extension mechanism, a support box, a vibration isolation mechanism, a load-bearing cylinder, a first drive motor, and an ultrasonic generator. The vibration isolation mechanism is mounted on a base, and the support box is rotatably mounted on the vibration isolation mechanism. The first drive motor drives the support box and the circular substrate fixed on the support box to rotate. The load-bearing cylinder is mounted on the base and located inside the vibration isolation mechanism. The piston end of the load-bearing cylinder passes through the support box and is connected to the synchronous extension mechanism via a thrust bearing. The transducers are mounted on the movable end of the synchronous extension mechanism via floating constant force connectors. The synchronous extension mechanism can drive several transducers on it to move synchronously along the radial direction of the circular substrate. The transducers are connected to the ultrasonic generator via high-frequency coaxial cables.

2. The apparatus for ultrasonic-assisted additive manufacturing of metal workpieces according to claim 1, characterized in that, The synchronous extension mechanism includes a circular base plate, a gear ring, a sliding mounting plate, a long gear, and a second drive motor. The circular base plate has a central hole in its center. The upper surface of the circular base plate has an outer ring protrusion and an inner ring protrusion concentrically arranged. An annular groove is provided on the inner side of the outer ring protrusion. The gear ring is rotatably disposed in the annular groove. The outer ring protrusion and the inner ring protrusion are respectively provided with a sliding groove along the circumference of the center of the circular base plate. The sliding mounting plate is slidably limited in the sliding groove. The floating constant force connector is fixed on the sliding mounting plate. A rack is provided on one side of the sliding mounting plate. The long gear is rotatably disposed on the circular base plate and meshes with the gear ring and the sliding mounting plate respectively. The second drive motor is installed at the bottom of the circular base plate and is used to drive the rotation of any long gear.

3. The apparatus for ultrasonic-assisted additive manufacturing of metal workpieces according to claim 2, characterized in that, It also includes a limiting mechanism, which includes several limiting shafts and heavy-duty linear bearings. The limiting shafts are circumferentially fixed to the lower surface of the circular base plate, and the heavy-duty linear bearings are installed on the outer edge of the circular base plate corresponding to the limiting shafts. The limiting shafts are inserted into the heavy-duty linear bearings.

4. The apparatus for ultrasonic-assisted additive manufacturing of metal workpieces according to claim 2, characterized in that, The floating constant force connector includes a housing base, a preload spring, a floating shaft, a spherical washer assembly, and an elastic vibration damping ring. The housing base is fixed to the sliding mounting plate. The floating shaft is axially slidably confined within the housing base via a linear bearing. The preload spring is disposed within the housing base and its two ends abut against the housing base and the floating shaft, respectively, providing a constant upward preload force to the floating shaft. A stud is provided at the upper end of the floating shaft, and the spherical washer assembly and the elastic vibration damping ring are sequentially sleeved on the stud and tightened by a lock nut. The transducer is fixedly connected to the metal mounting surface of the elastic vibration damping ring.

5. The apparatus for ultrasonic-assisted additive manufacturing of metal workpieces according to claim 2, characterized in that, It also includes a displacement sensor, which is mounted on a sliding mounting plate on one side of the floating constant force connector, for monitoring the displacement of the transducer.

6. The apparatus for ultrasonic-assisted additive manufacturing of metal workpieces according to claim 1, characterized in that, The piston rod of the load-bearing cylinder is connected to a stepped shaft at its top. The center of the stepped shaft has a through hole. The thrust bearing is sleeved on the stepped shaft, its seat ring is connected to the stepped shaft, and its shaft ring is connected to the synchronous extension mechanism.

7. The apparatus for ultrasonic-assisted additive manufacturing of metal workpieces according to claim 6, characterized in that, It also includes a conductive slip ring, the rotor end of which is coaxially fixed to and rotates with the central part of the synchronous extension mechanism, and the stator end of which is fixed to the stepped shaft; the high-frequency coaxial cable of the transducer is connected to the rotor end of the conductive slip ring, and the ultrasonic generator is connected to the stator end of the conductive slip ring via a cable.

8. The apparatus for ultrasonic-assisted additive manufacturing of metal workpieces according to claim 6, characterized in that, It also includes a cooling mechanism, which includes an annular cooling water jacket, a braided hose, and a multi-channel rotary joint. The annular cooling water jacket is made of copper and is fitted onto the transducer. It is connected to the multi-channel rotary joint via the braided hose. The multi-channel rotary joint is installed in the middle of the synchronous extension mechanism and fitted onto the stepped shaft. The multi-channel rotary joint is connected to the cooling system fixed to the equipment base.

9. The apparatus for ultrasonic-assisted additive manufacturing of metal workpieces according to claim 1, characterized in that, The vibration isolation mechanism includes an external toothed crossed roller slewing bearing, a circular vibration isolation base, and several rubber vibration isolators. The outer ring of the external toothed crossed roller slewing bearing is fixedly connected to the support box, and the inner ring of the external toothed crossed roller slewing bearing is fixedly connected to the circular vibration isolation base. The several rubber vibration isolators are evenly arranged circumferentially. The lower end of each rubber vibration isolator is fixed to the equipment base, and the upper end is fixed to the circular vibration isolation base. The first drive motor and the reducer connected thereto are fixedly installed on the circular vibration isolation base. The output end of the reducer is provided with a drive gear that meshes with the gear ring on the outer ring of the external toothed crossed roller slewing bearing.

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