A five-axis machining center for metal working

Abstract

This invention relates to a five-axis machining center for metal processing, belonging to the field of metal processing equipment, and aims to solve the problems of clamping force attenuation, vibration, and inconvenience in disassembling and assembling the milling head during high-speed milling in existing equipment. It includes a machine tool body, a milling spindle, and a milling head. The end of the milling spindle is equipped with a hydraulically clamped milling head fixing mechanism, comprising a closed hydraulic expansion chamber, multiple sets of tilting embedded centrifugal compensation cylinders, and a milling vibration reduction assembly. The locking bushing within the hydraulic expansion chamber can radially elastically deform to grip the milling head shank. The counterweight piston within the centrifugal compensation cylinder generates centrifugal force with the rotational speed, linking a hydraulic linkage circuit to achieve dynamic compensation of the clamping force. Simultaneously, the milling vibration reduction assembly absorbs energy through damping springs and dissipates vibration through energy-dissipating sliders. This invention balances high-speed clamping stability, vibration resistance, and automation adaptability, extending the life of equipment and tools, and improving the high-speed precision machining capability and automation level of the machining center.

Description

Technical Field

[0001] This invention relates to the field of metal processing equipment, specifically to a five-axis machining center for metal processing. Background Technology

[0002] Five-axis machining centers are core equipment for precision metal milling. The milling head clamping structure of the milling spindle is a key component that determines machining accuracy, operational stability, tool life, and the overall machining capacity. In high-speed metal milling, the milling spindle needs to drive the milling head to rotate at tens of thousands of revolutions per minute, placing extremely high demands on the high-speed adaptability, clamping reliability, and vibration resistance of the clamping structure. Currently, the mainstream five-axis machining center spindle milling head clamping solution adopts a traditional conical clamping structure. This structure relies on the spindle's built-in spindle puller mechanism to clamp the conical shank section of the milling head tool holder. The conical surface engagement achieves radial positioning of the milling head and transmission of machining torque. Some solutions supplement this with a static hydraulic clamping structure to increase clamping force.

[0003] However, the existing structure still has certain shortcomings in practical applications of high-speed milling.

[0004] First, when the milling spindle rotates at high speed, the mounting hole of the milling spindle undergoes radial expansion deformation under centrifugal force. This causes a sharp drop in the contact area between the tool holder and the milling spindle, resulting in a significant decrease in the clamping force provided by static preload. Consequently, this leads to radial runout and axial movement of the milling head tool holder, directly causing out-of-tolerance machining form and position accuracy and surface quality degradation, which is particularly prominent in high-speed machining scenarios using milling spindles. Existing static clamping structures cannot achieve dynamic compensation of clamping force with changes in rotational speed, severely limiting the high-speed precision machining capabilities of five-axis machining centers.

[0005] Secondly, the clearance caused by centrifugal force will induce severe forced vibrations in the milling spindle and milling head system under the alternating cutting loads of metal milling. This vibration will not only further amplify the clearance and exacerbate impact wear and fatigue damage to the mating surfaces, but will also cause the milling cutter to chip and the milling spindle bearings to fail prematurely, creating a vicious cycle of widening clearance, intensified vibration, accelerated wear, and continuous deterioration of positioning accuracy. Existing clamping structures cannot simultaneously achieve dynamic compensation of clamping force and synchronous suppression of milling vibration at high speeds, making it difficult to balance clamping reliability and operational stability in high-speed machining.

[0006] The purpose of this invention is to design a five-axis machining center for metal processing to address the problems existing in the prior art. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides a five-axis machining center for metal processing, which can effectively solve at least one of the problems existing in the prior art.

[0008] The technical solution of this invention is:

[0009] A five-axis machining center for metal processing includes a machine tool body, a milling spindle mounted on the machine tool body via a three-dimensional motion mechanism, and a milling head mounted on the milling spindle. Driven by a drive motor, the milling spindle rotates at high speed to drive the milling head to rotate for milling operations. The end of the milling spindle is provided with a hydraulically clamped milling head fixing mechanism to secure the milling head on the milling spindle. The milling head fixing mechanism includes:

[0010] A closed hydraulic expansion chamber, wherein a locking bushing that can elastically deform along its radial direction is provided inside the hydraulic expansion chamber for gripping the tool holder of the milling head to achieve positioning and locking;

[0011] Multiple sets of centrifugal compensation cylinders are evenly arranged around the circumference of the milling spindle. Each set of centrifugal compensation cylinders is equipped with a counterweight piston that can slide in a direction close to or away from the hydraulic expansion chamber. The outer end of the counterweight piston away from the hydraulic expansion chamber forms a pressurization zone with the centrifugal compensation cylinder and is connected to the hydraulic expansion chamber through the oil passage built into the milling spindle, forming a closed hydraulic linkage circuit. The hydraulic linkage circuit is filled with hydraulic oil.

[0012] The milling vibration reduction assembly includes a vibration damping spring and an energy dissipation slider coaxially disposed in a centrifugal compensation cylinder. The energy dissipation slider is connected to the inner end face of the counterweight piston through the vibration damping spring, and is used to reduce the vibration generated during milling to maintain the stability of milling.

[0013] As a further improvement, the centrifugal compensation cylinder is inclined at the end away from the milling head along the axial direction of the milling spindle, and a sliding cavity is formed therein for the counterweight piston to slide. The pressurization zone is located on the side of the sliding cavity away from the hydraulic expansion cavity and is connected to the hydraulic linkage circuit. The extension line of the central axis of the sliding cavity intersects the central axis of the milling spindle.

[0014] As a further improvement, the energy dissipation slider slides into the sliding cavity, and the end face of the counterweight piston extends coaxially into a hollow cylindrical extension. The damping spring is located in the hollow area of ​​the extension, and the end face of the extension is used to contact the end face of the energy dissipation slider to form a stop structure.

[0015] As a further improvement, the energy dissipation slider is cylindrical and slides with the sliding cavity, and the energy dissipation slider has several interconnected balance air holes on both ends of its axial direction.

[0016] As a further improvement, the bottom end of the milling spindle forms a milling head fixing hole. The milling head fixing hole includes a tapered positioning section, a cylindrical fitting section, and a pull claw section with its opening facing the inside of the milling spindle. The milling head includes a coaxially arranged pull claw end, a cylindrical tool holder, a tapered shank end, a flange, a milling cutter connecting end, and a milling cutter body. The pull claw end cooperates with the pull claw structure provided in the pull claw section for pre-tightening the entire milling head. The hydraulic expansion chamber is annular and coaxially located on the milling head. Within the cylindrical fitting section of the fixed hole, the locking bushing is an annular thin-walled structure and is located on the side of the hydraulic expansion chamber near the center of the cylindrical fitting section. The inner diameter of the locking bushing in its free state is consistent with the bore diameter of the cylindrical fitting section and flush with the bore wall of the cylindrical fitting section. The outer diameter of the locking bushing facing the hydraulic expansion chamber is larger than the bore diameter of the cylindrical fitting section. The milling spindle is provided with a connecting oil passage, which connects the hydraulic expansion chamber and the pressurization zone to form a closed hydraulic linkage circuit.

[0017] As a further improvement, the locking bushing is integrally formed with the body of the milling spindle, constituting part of the hole wall of the cylindrical fitting section, or it is an independent annular thin-walled structure located in the hydraulic expansion cavity of the cylindrical fitting section.

[0018] As a further improvement, the locking bushing has a support protruding on one side near the hydraulic expansion chamber, and the end of the support extends to the side wall of the hydraulic expansion chamber opposite it with a gap.

[0019] As a further improvement, the hydraulic linkage circuit is provided with a one-way hydraulic control valve that is unilaterally open towards the centrifugal compensation cylinder. The valve core of the one-way hydraulic control valve is provided with a counterweight structure so as to drive the valve core to move in the reverse direction during the rotation of the spindle used for milling to open the one-way hydraulic control valve.

[0020] As a further improvement, the hydraulic linkage circuit is equipped with an overflow valve.

[0021] As a further improvement, the centrifugal compensation cylinder is provided with at least three cylinders, which are evenly arranged circumferentially around the spindle used for milling.

[0022] Therefore, the present invention provides the following effects and / or advantages:

[0023] The existing milling head clamping schemes for milling spindles in five-axis machining centers mostly adopt the traditional conical tensioning and static hydraulic clamping structure. When the milling spindle rotates at high speed, the mounting hole of the milling spindle undergoes radial expansion deformation under the action of centrifugal force, which causes a sharp drop in the contact area between the milling head holder and the milling spindle. The clamping force provided by the static preload is significantly reduced, which in turn causes radial runout and axial movement of the milling head holder, directly resulting in out-of-tolerance machining form and position accuracy and deterioration of surface quality. This is particularly prominent in high-speed machining scenarios for milling spindles. The existing static clamping structure cannot achieve dynamic compensation of clamping force with changes in rotation speed, which seriously limits the high-speed precision machining capability of five-axis machining centers. To address this issue, the present invention uniformly arranges multiple sets of centrifugal compensation cylinders circumferentially on the milling spindle. The centrifugal force generated by the counterweight piston as the spindle speed changes links the closed hydraulic linkage circuit built into the spindle, driving the locking bushing in the hydraulic expansion chamber to undergo radial elastic deformation and clamp the milling head tool holder. This achieves adaptive dynamic compensation of the milling head clamping force as the spindle speed changes, completely solving the problem of clamping force attenuation due to radial expansion of the spindle under high-speed conditions. It effectively suppresses radial runout and axial movement of the tool holder, ensuring the dimensional accuracy and surface finish of high-speed milling, and raising the upper limit of high-speed precision machining in five-axis machining centers.

[0024] Existing clamping structures cannot simultaneously achieve dynamic compensation of clamping force and synchronous suppression of milling vibration at high speeds. The clearance caused by centrifugal force will induce severe forced vibration of the milling spindle and milling head system under the alternating cutting load of metal milling. This vibration will not only further amplify the clearance and exacerbate impact wear and fatigue damage to the mating surfaces, but also cause chipping of the milling cutter body and premature failure of the milling spindle bearings, forming a vicious cycle of widening clearance, intensified vibration, accelerated wear, and continuous deterioration of positioning accuracy. To address this, the present invention synchronously sets up a milling vibration reduction component consisting of a damping spring and an energy dissipation slider in the centrifugal compensation cylinder. Sharing the same cylinder body with the centrifugal compensation structure, it eliminates the need for additional independent vibration reduction devices. While achieving dynamic compensation of clamping force, it can simultaneously absorb the alternating vibration load generated by milling, realizing a synergistic effect of clamping force compensation and vibration suppression, breaking the vicious cycle of accuracy deterioration, balancing clamping reliability and operational stability in high-speed machining, and effectively extending the service life of the milling cutter and the milling spindle bearings.

[0025] Existing hydraulically assisted clamping spindle clamping structures for milling machining are mostly static clamping designs with fixed pressure. This results in a lack of stable preload reference for dynamic compensation, and the expansion of hydraulic oil due to high-speed operation easily leads to circuit pressure overload and structural cracking, posing serious safety hazards. To address this, this invention adds a one-way hydraulic control valve with a counterweight structure and an overflow valve to the hydraulic linkage circuit. The one-way hydraulic control valve achieves full-condition adaptability for static pressure holding preload and reverse conduction dynamic compensation during rotation, while the overflow valve automatically relieves circuit pressure overload. This ensures stable auxiliary clamping force under static conditions and a stable pressure reference for dynamic compensation, while completely avoiding the structural damage risks caused by high-speed temperature rise and pressure overload, significantly improving the operational safety of the mechanism.

[0026] Furthermore, this invention features a centrifugal compensation cylinder that is inclined and embedded along the axial direction of the milling spindle towards the end furthest from the milling head. The extended line of the central axis of its sliding cavity intersects with the central axis of the milling spindle. After the milling spindle stops, the counterweight piston and energy dissipation slider can automatically fall back to the low position of the sliding cavity by their own weight, automatically reducing the pressure in the pressurization zone. This allows the residual high pressure in the hydraulic expansion chamber to be automatically released into the pressurization zone of multiple centrifugal compensation cylinders through pressure difference, achieving fully automatic pressure relief of the circuit. The milling head can be easily disassembled and assembled without manual assistance. It can also be adapted to the automatic tool changer of the machine tool to achieve a fully automatic tool change process, greatly improving the automation efficiency of the machining center. The embedded inclined design also eliminates the wind resistance and dynamic balance problems caused by the protrusion of the outer wall of the milling spindle, avoids additional vibration and noise caused by high-speed rotation, and further improves the stability of the milling spindle during high-speed operation.

[0027] Existing spindle vibration damping structures for milling generally suffer from slow vibration damping response and poor energy absorption and dissipation effects. The high-frequency alternating vibrations generated during milling cannot be quickly absorbed and dissipated. At the same time, the damping springs are prone to over-compression due to excessive vibration amplitude, resulting in plastic fatigue or even fracture failure. When the energy dissipation slider slides, it is easy to generate air pressure resistance, which further reduces the vibration damping response speed, resulting in a significant reduction in the vibration damping effect and a substantial shortening of the mechanism's service life. To address this, the present invention coaxially connects the energy-dissipating slider to the inner end face of the counterweight piston via a damping spring, and extends a hollow cylindrical extension coaxially from the end face of the counterweight piston, housing the damping spring within the hollow region of the extension. During milling, the alternating vibration load generated by the tool holder and the milling spindle is synchronously transmitted to the centrifugal compensation cylinder. Firstly, the elastic deformation of the damping spring rapidly absorbs the peak energy of the vibration impact, suppressing the transmission and amplification of the vibration to the spindle system. Simultaneously, it drives the energy-dissipating slider to reciprocate axially within the sliding cavity. This is achieved through frictional damping between the energy-dissipating slider and the inner wall of the sliding cavity, and the balance air holes on the energy-dissipating slider. Airflow damping continuously dissipates remaining vibration energy, achieving efficient energy absorption and dissipation of milling broadband vibrations, significantly reducing vibration amplitude. Meanwhile, the hollow cylindrical extension on the counterweight piston forms a rigid stop with the end face of the energy dissipation slider when the vibration amplitude is too large or the compression of the damping spring exceeds the limit. This precisely limits the maximum compression stroke of the damping spring, preventing plastic fatigue failure due to over-compression. At the same time, it limits the sliding stroke of the energy dissipation slider, preventing it from sliding off track. This ensures stable and reliable operation of the vibration damping components under full speed and full vibration conditions, further improving the anti-vibration performance and long-term service life of the spindle system.

[0028] To avoid uneven circumferential deformation and uneven clamping force during high-pressure clamping of hydraulic expansion locking bushings, which can lead to misalignment between the tool holder and the milling spindle, reduced repeatability, and excessive radial deformation under high pressure, causing plastic damage and clamping force failure, thus compromising long-term stable clamping performance, this invention provides a support portion protruding from the side of the locking bushing near the hydraulic expansion chamber. The end of the support portion extends to the sidewall of the opposite hydraulic expansion chamber with a gap. During the process of hydraulic oil pressurizing and driving the locking bushing to radially deform and clamp the milling head tool holder, the circumferentially provided support portion can... The radial deformation of the locking bushing is uniformly limited circumferentially, ensuring that the deformation at all points in the circumference of the locking bushing remains consistent. This guarantees that the locking bushing forms a uniform, full-circumferential enveloping grip on the milling head shank, preventing tool shank skew caused by uneven circumferential gripping force. This achieves high-precision coaxial center positioning between the tool shank and the milling spindle, significantly improving the repeatability and coaxiality of the milling head installation. Simultaneously, when the radial deformation of the locking bushing reaches a set threshold, the support portion can form a rigid support with the sidewall of the hydraulic expansion chamber, preventing plastic damage to the locking bushing due to excessive deformation. This ensures the long-term consistency of the gripping action and the service life of the clamping structure.

[0029] In summary, this invention achieves dynamic compensation of the milling head clamping force through a speed-adaptive centrifugal hydraulic linkage structure, solving the core problem of clamping force attenuation under high-speed conditions. Simultaneously, relying on the synergy of centrifugal compensation and vibration reduction functions, it simultaneously achieves efficient energy absorption and dissipation of clamping force compensation and milling vibration, breaking the vicious cycle of precision degradation. Through the tilting centrifugal compensation cylinder design, it achieves fully automatic pressure relief of the circuit after machine shutdown, adapting to fully automatic tool changing processes and improving the machine tool's automated machining efficiency. This invention balances the clamping stability, operational safety, ease of operation, and long service life of the mechanism, while also enhancing the high-speed precision machining capability, operational stability, and automated machining level of the five-axis machining center.

[0030] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained through the structures particularly pointed out in the description and the drawings.

[0031] It should be understood that the above summary and the following detailed description of the invention are exemplary and explanatory, and are intended to provide further explanation of the invention as claimed. Attached Figure Description

[0032] Figure 1 This is a three-dimensional structural diagram of Embodiment 1 of the present invention.

[0033] Figure 2 This is a schematic diagram of the overall structure of Embodiment 1 of the present invention.

[0034] Figure 3 This is a partial cross-sectional view of Embodiment 1 of the present invention.

[0035] Figure 4 This is one of the three-dimensional structural schematic diagrams of the spindle used for milling in Embodiment 1 of the present invention.

[0036] Figure 5 This is the second three-dimensional structural schematic diagram of the spindle used for milling in Embodiment 1 of the present invention.

[0037] Figure 6 This is one of the cross-sectional structural schematic diagrams of the spindle used for milling in Embodiment 1 of the present invention.

[0038] Figure 7 This is a schematic diagram of the overall structure of the milling head in Embodiment 1 of the present invention.

[0039] Figure 8 This is the second cross-sectional view of the spindle used for milling in Embodiment 1 of the present invention.

[0040] Figure 9This is a three-dimensional structural diagram highlighting the four sets of centrifugal compensation cylinders in Embodiment 1 of the present invention.

[0041] Figure 10 This is an exploded structural diagram of the centrifugal compensation cylinder in Embodiment 1 of the present invention.

[0042] Figure 11 This is a schematic diagram of the exploded and cross-sectional structure of the centrifugal compensation cylinder in Embodiment 1 of the present invention.

[0043] Figure 12 This is a schematic diagram of the oil circuit connection of the hydraulic linkage circuit in Embodiment 1 of the present invention.

[0044] Figure 13 This is a three-dimensional structural diagram highlighting the automatic tool changer in Embodiment 1 of the present invention.

[0045] Figure 14 This is a cross-sectional view of the spindle used for milling in Embodiment 2 of the present invention.

[0046] In the picture:

[0047] 100. Machine tool body; 110. Spindle box; 120. Worktable; 200. Five-axis linkage feed mechanism; 210. X-axis mechanism; 211. Moving seat; 220. YZ-axis mechanism; 230. Bidirectional rotation mechanism; 231. Cradle mechanism; 232. Rotation mechanism; 300. Milling spindle; 310. Milling head mounting end; 320. Milling head fixing hole; 321. Tapered positioning section; 322. Cylindrical fitting section; 323. Puller section; 330. Hydraulic linkage circuit; 340. Extension section; 341. Opening surface; 342. Sealing locking cover; 400. Drive motor; 500. Milling head; 510. Puller end; 520. Tool holder; 5 30. Tapered shank end; 540. Flange; 550. Milling cutter connection end; 560. Milling cutter body; 600. Milling head fixing mechanism; 610. Hydraulic expansion chamber; 620. Locking bushing; 621. Support part; 630. Centrifugal compensation cylinder; 631. Sliding chamber; 632. Pressurization zone; 640. Counterweight piston; 641. Piston body; 642. Counterweight block; 643. Sealing ring; 644. Extension part; 650. One-way hydraulic control valve; 660. Overflow valve; 700. Milling vibration damping assembly; 710. Vibration damping spring; 720. Energy dissipation slider; 721. Balance air hole; 722. Positioning groove; 730. Hook structure; 800. Automatic tool changer. Detailed Implementation

[0048] To facilitate understanding by those skilled in the art, the structure of the present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0049] Example 1

[0050] refer to Figure 1-13 This embodiment discloses a five-axis machining center for metal processing, including a machine tool body 100, a five-axis linkage feed mechanism 200 set on the machine tool body 100 and formed based on a three-dimensional motion mechanism, a milling spindle 300, a drive motor 400, and a milling head 500 adapted to be installed on the milling spindle 300.

[0051] The five-axis linkage feed mechanism 200 is based on a three-dimensional motion mechanism and is used to drive the milling spindle 300 to generate a five-axis linkage relative feed motion between it and the workpiece. Specifically, it includes an X-axis mechanism 210 for linear feed (first axis) mounted on the machine tool body 100, a YZ-axis mechanism 220 for bidirectional planar feed above the X-axis mechanism 210, and a bidirectional rotation mechanism 230. In this embodiment, the YZ-axis mechanism 220 is a gantry-type dual-axis moving mechanism. The milling spindle 300 is mounted on a spindle box 110, which is fixed to the moving feed end of the YZ-axis mechanism 220, achieving dual-axis feed in the YZ plane following the YZ-axis mechanism 220. The X-axis mechanism 210 and the YZ-axis mechanism 220 constitute the first, second, and third axes of the machining center. The X-axis mechanism 210 has a moving feed end with a moving seat 211. The moving seat 211 is equipped with a boat-shaped cradle mechanism 231 that can rotate up and down along the YZ axis. The center of the cradle mechanism 231 is additionally equipped with a rotation mechanism 232 that can rotate along its own axis. The rotation output end of the rotation mechanism 232 is equipped with a worktable 120 for fixing the workpiece to be processed. The cradle mechanism 231 and the rotation mechanism 232 are combined to form a bidirectional rotation mechanism 230, which constitutes the fourth axis of the fourth degree of freedom and the fifth axis of the fifth degree of freedom of the machining center. The metal workpiece to be processed is clamped and fixed on the worktable 120. By using the five degrees of freedom formed by the above five-axis drive, the milling spindle 300 and the corresponding milling head 500 can perform milling on the workpiece relatively freely. This is the prior art and will not be described in detail here.

[0052] Furthermore, the rotor of the drive motor 400 is connected to the milling spindle 300 for high-speed rotation, thereby driving the milling head 500 to perform high-speed precision milling on the workpiece. The lower end of the milling spindle 300 protrudes from the spindle box 110 and forms the milling head mounting end 310. The milling spindle 300 integrates a hydraulic milling head fixing mechanism 600 with adaptive speed dynamic compensation function, which is the core improved structure of this embodiment. It is used to achieve reliable clamping of the milling head 500 on the milling spindle 300, dynamic compensation of clamping force under high-speed conditions, and synchronous suppression of milling vibration.

[0053] Specifically, the milling head mounting end 310 of the milling spindle 300 has a milling head fixing hole 320 coaxially provided. The milling head fixing hole 320 faces the inside of the milling spindle 300 along its opening and includes a tapered positioning section 321, a cylindrical fitting section 322 and a pull claw section 323 coaxially arranged.

[0054] Correspondingly, combined Figure 7 The milling head 500 includes, along its axial direction, a pull claw end 510, a cylindrical tool holder 520, a tapered shank end 530, a flange 540, a milling cutter connecting end 550, and a milling cutter body 560. During installation, the tapered shank end 530 engages with the tapered positioning section 321 to achieve initial radial positioning. The pull claw end 510 engages with the spindle pull claw mechanism within the pull claw section 323 to achieve axial pre-tightening of the entire milling head 500. The tool holder 520 and the cylindrical engagement section 322 are coaxially aligned, providing a reference for hydraulic clamping and ensuring the coaxial installation accuracy of the milling head 500 and the spindle. The flange 540 abuts against the bottom end face of the milling head mounting end 310 to achieve axial positioning of the milling head 500 along the milling spindle 300.

[0055] During initial tightening, the pull claw structure inside the milling spindle 300 is used to tighten the pull claw end 510 of the milling head 500, so that the tool holder 520 is embedded in the cylindrical fitting section 322, and the conical surface of the tapered shank end 530 is in contact with the conical surface of the tapered positioning section 321. The flange 540 then abuts against the bottom end face of the milling head mounting end 310, thereby achieving overall pre-tightening of the milling head 500 structure.

[0056] The core clamping execution unit of the milling head fixing mechanism 600 is an annular closed hydraulic expansion cavity 610 coaxially arranged in the cylindrical fitting section 322, and a locking bushing 620 that can elastically deform in the radial direction. The hydraulic expansion cavity 610 is coaxially annularly disposed within the side wall of the cylindrical fitting section 322. In this embodiment, the locking bushing 620 is an annular thin-walled structure, disposed on the side of the hydraulic expansion cavity 610 near the center of the cylindrical fitting section. The inner diameter of the locking bushing 620 in its free state is consistent with the bore diameter of the cylindrical fitting section 322, so as to form a flush state with the bore wall of the cylindrical fitting section 322, facilitating the insertion of the end of the milling head 500. Its outer diameter on the side facing the hydraulic expansion cavity 610 is larger than the bore diameter of the cylindrical fitting section 322. In addition, the upper and lower sides of the locking bushing 620 are in close contact with the upper and lower end faces of the hydraulic expansion cavity 610 to form a seal. On the side of the locking bushing 620 near the hydraulic expansion cavity 610, a plurality of support portions 621 are uniformly and integrally protruding along the circumference. The ends of the support portions 621 extend to the inner side wall of the hydraulic expansion cavity 610 directly opposite them, and a set deformation gap is left between them. During the process of hydraulic oil driving the locking bushing 620 to radially deform and clamp the milling head 500 and tool holder 520, the circumferentially uniformly arranged support part 621 can circumferentially limit the radial deformation of the locking bushing 620, so that the deformation of the locking bushing 620 at each point in the circumference remains highly consistent. This ensures that the locking bushing 620 forms a 360° full-circumferential uniform enclosure and clamping of the milling head 500 and tool holder 520, avoiding the tool holder 520 from deflection due to uneven circumferential clamping force. This achieves high-precision coaxial center positioning of the milling head 500 and the milling spindle 300, greatly improving the repeatability and clamping coaxiality of the milling head 500 installation. At the same time, when the locking bushing 620 radially deforms to a set threshold, the end of the support part 621 forms a rigid support with the inner wall of the hydraulic expansion chamber 610, preventing the locking bushing 620 from plastic damage due to excessive deformation, and ensuring the long-term consistency of the clamping action and the service life of the structure.

[0057] To achieve adaptive dynamic compensation of clamping force under high-speed operating conditions, the milling head fixing mechanism 600 also includes multiple sets of centrifugal compensation cylinders 630 uniformly embedded in the circumference of the milling spindle 300, as well as a closed hydraulic linkage circuit 330 built into the milling spindle 300 (not shown in the figure). In this embodiment, four sets of centrifugal compensation cylinders 630 are provided, which are evenly distributed around the central axis of the milling spindle 300. Each set of centrifugal compensation cylinders 630 is inclined towards the end away from the milling head 500 along the axial direction of the milling spindle 300. A sliding cavity 631 for the counterweight piston 640 to slide and extend is formed coaxially inside each set of centrifugal compensation cylinders 630. The extension line a of the central axis of each sliding cavity 631 intersects the central axis b of the milling spindle 300. A counterweight piston 640 is coaxially slidably installed in the sliding cavity 631 of each set of centrifugal compensation cylinders 630. The outer end face of the counterweight piston 640 away from the hydraulic expansion cavity 610 and the end wall of the sliding cavity 631 form a pressurization zone 632. The milling spindle 300 has a connecting oil passage (not shown in the figure) inside its body. The connecting oil passage connects the hydraulic expansion chamber 610 to the pressurization zone 632 of each set of centrifugal compensation cylinders 630 in sequence, forming a completely closed hydraulic linkage circuit 330. The hydraulic linkage circuit 330 is filled with anti-wear hydraulic oil. Specifically, there are various ways to implement the connecting oil passage. For example, a split-type milling spindle 300 can be used, with oil passage grooves opened on the joint end faces of each of its parts. After they are assembled, they form the corresponding connecting oil passage. Alternatively, the milling spindle 300 with specific connecting oil passages can be integrally printed using 3D printing. The forming ideas of the locking bushing 620 and the hydraulic expansion chamber 610 can also refer to the above methods, or use optional forming methods within the scope of existing technology, which will not be elaborated here.

[0058] In the hydraulic linkage circuit 330, at the inlet of the pressurization zone 632 corresponding to each set of centrifugal compensation cylinders 630, a one-way hydraulic control valve 650 (not shown in the figure) is provided, which is unilaterally conductive towards the centrifugal compensation cylinder 630. By setting a counterweight structure (not shown in the figure) on the control valve core of the one-way hydraulic control valve 650, and designing the overall orientation of the one-way hydraulic control valve 650 to be radially distributed along the milling spindle 300, the control valve core can extend and retract radially along the milling spindle 300. When the milling spindle 300 rotates, the centrifugal force generated by the valve core counterweight structure can drive the valve core to move, overcoming the elastic force of its built-in spring, and realizing the reverse conduction of the one-way hydraulic control valve 650, thereby enabling the one-way hydraulic control valve 650 to conduct in the milling process. During the rotation of the working spindle 300, the oil pressure generated by the centrifugal force of the counterweight piston 640 and / or the energy dissipation slider 720 in the pressurization zone 632 is compensated to the hydraulic expansion chamber 610 through the reverse-connected hydraulic linkage circuit 330, which enhances the pressure of the locking bushing 620 and further presses it against the tool holder 520 of the milling head 500, thereby completing the full-condition adaptation of static pressure holding and dynamic compensation. At the same time, a miniature relief valve 660 is also installed on the main oil line of the hydraulic linkage circuit 330. The opening pressure of the relief valve 660 is set to the highest safe pressure of the circuit. When the circuit pressure exceeds the threshold due to high-speed temperature rise or abnormal working conditions, the relief valve 660 automatically opens to relieve pressure, avoiding structural cracking and damage, and ensuring the safe operation of the mechanism. When the milling spindle 300 rotates, the counterweight piston 640 rotates synchronously with the milling spindle 300, generating centrifugal force. This force overcomes the spindle's own weight and slides along the sliding cavity 631 away from the center of the milling spindle 300, applying pressure to the volume of the compression and pressurization zone 632. Due to the incompressibility of hydraulic oil, the hydraulic oil pressure in the circuit increases synchronously with the rotational speed. The high-pressure hydraulic oil is transmitted to the hydraulic expansion chamber 610, driving the locking bushing 620 to produce radial elastic deformation. This compensates for the radial expansion of the mounting hole when the milling spindle 300 rotates at high speed, achieving adaptive dynamic compensation of the milling head 500's clamping force with rotational speed and solving the problem of clamping force attenuation under high-speed conditions. The problem is that when the milling spindle 300 stops, its speed drops to zero, the centrifugal force of the counterweight piston 640 disappears, and under its own gravity, it automatically falls back to the low position along the inclined sliding cavity 631. The volume of the pressurization zone 632 expands, the circuit pressure automatically decreases, and the residual high pressure in the hydraulic expansion chamber 610 is automatically released to each pressurization zone 632 through the pressure difference (pressure difference on both sides of the one-way hydraulic control valve 650), realizing the fully automatic pressure relief of the hydraulic linkage circuit 330. With the release of the spindle puller mechanism, the milling head 500 can be automatically unlocked, thus enabling convenient disassembly and assembly of the milling head 500 without manual assistance. It can be perfectly adapted to the automatic tool changer 800 of the machine tool (in conjunction with...). Figure 13 This enables a fully automated tool changing process, significantly improving the automated machining efficiency of machining centers.

[0059] In this embodiment, the automatic tool changer 800, the one-way hydraulic valve 650, and the overflow valve 660 are all conventional components in the art, and their structures and principles are well known to those skilled in the art. This embodiment only utilizes their inherent properties to achieve the corresponding technical effects, and will not elaborate further here. In particular, in this embodiment, the orientation of the overflow valve 660 is set to be parallel to the axis of the milling spindle 300 to avoid the influence of high-speed rotation on it.

[0060] Furthermore, in this embodiment, the counterweight piston 640 includes a cylindrical piston body 641, a counterweight block 642, and an oil-resistant sealing ring 643. Three sealing grooves (not shown in the figure) are uniformly formed along the axial direction of the piston body 641. A sealing ring 643 is embedded in each sealing groove, enabling smooth sliding between the piston body 641 and the sliding cavity 631, and sealing the pressurized area 632. An installation groove (not shown in the figure) is formed on the end face of the piston body 641, and the counterweight block 642 is secured within the installation groove, thus completing the overall structure of the counterweight piston 640. The bottom of the sliding cavity 631 is also connected to the central channel of the milling spindle 300 or directly to the external environment via a corresponding air passage (not shown in the figure), thereby preventing internal air pressure from affecting the sliding of the counterweight piston 640 and the energy dissipation slider 720.

[0061] To achieve efficient suppression of milling vibration, each set of centrifugal compensation cylinders 630 integrates a milling vibration damping assembly 700 in its sliding cavity 631. The milling vibration damping assembly 700 includes a damping spring 710 and an energy dissipation slider 720 arranged coaxially. The energy dissipation slider 720 has a cylindrical structure that slides with the inner wall of the sliding cavity 631. It is coaxially slidably disposed on one side of the sliding cavity 631 near the center of the milling spindle 300, and is fixedly connected to the inner end face of the counterweight piston 640 through the damping spring 710. At the same time, it is guided by the sealing ring 643. The inner end face of the counterweight piston 640 extends coaxially into a hollow cylindrical extension 644. The damping spring 710 is coaxially built into the hollow area of ​​the extension 644. In this embodiment, the damping spring 710 is fixedly connected to the extension 644 and the energy dissipation slider 720 through a hook structure 730 provided at the bottom of the extension 644 and on the energy dissipation slider 720. The end face of the extension 644 can contact the end face of the energy dissipation slider 720 to form a rigid stop structure. At the same time, the energy dissipation slider 720 has several interconnected balance air holes 721 on its two end faces along its axial direction to eliminate air pressure resistance when the energy dissipation slider 720 slides back and forth, thereby improving the damping response speed. Furthermore, the energy-dissipating slider 720 is recessed inward on the side facing the counterweight piston 640 to form a positioning groove 722. The hook structure 730 and the damping spring 710 are both located in the positioning groove 722. During the milling process, the alternating cutting load generated by the milling cutter body 560 cutting the workpiece is transmitted to the spindle system through the milling head 500, exciting the forced vibration of the milling spindle 300 and the milling head 500. This vibration load is synchronously transmitted to the centrifugal compensation cylinder 630. First, the peak energy of the vibration impact is quickly absorbed by the elastic deformation of the damping spring 710, suppressing the transmission and amplification of the vibration to the spindle system. Simultaneously, the energy-dissipating slider 720 is driven to reciprocate axially within the sliding cavity 631. The frictional damping of the inner wall and the airflow damping of the balance vent 721 continuously dissipate the remaining vibration energy, achieving efficient energy absorption and dissipation of milling broadband vibration, significantly reducing the vibration amplitude, and breaking the vicious cycle of widened gap, increased vibration, accelerated wear, and deteriorated precision. When the vibration amplitude is too large and the compression of the damping spring 710 exceeds the limit, the extension 644 on the counterweight piston 640 and the end face of the energy dissipation slider 720 form a rigid stop, precisely limiting the maximum compression stroke of the damping spring 710, avoiding plastic fatigue failure of the damping spring 710 due to over-compression, and at the same time limiting the sliding stroke of the energy dissipation slider 720 to prevent the energy dissipation slider 720 from sliding off the track, ensuring the stable and reliable operation of the vibration damping component under full speed and full vibration conditions.

[0062] Furthermore, in this embodiment, in order to accommodate the centrifugal compensation cylinder 630, the middle section of the milling spindle 300 extends outward to form an annular extension section 340. Near the top of the extension section 340, an annular and inclined opening surface 341 is formed. The sliding cavity 631 is formed by linear machining inward along the opening surface 341. The opening of the sliding cavity 631 is sealed by the sealing locking cover 342, which facilitates the installation of various components inside the centrifugal compensation cylinder 630 and the setting of the centrifugal compensation cylinder 630. At the same time, it can also prevent the centrifugal compensation cylinder 630 from protruding from the surface of the milling spindle 300 and generating additional resistance and noise during high-speed centrifugal operation.

[0063] The full-condition workflow of this embodiment is as follows: When installing the milling head 500, insert the milling head 500 into the milling head fixing hole 320 of the milling spindle 300. Axial pre-tightening is completed through the pull claw mechanism inside the milling spindle 300, and radial initial positioning is completed through the conical surface fit, realizing static auxiliary clamping of the milling head 500 tool holder 520; when the milling spindle 300 starts and accelerates to the machining speed, the one-way hydraulic control valve 650 is reverse-guided under the action of the centrifugal force of the valve core counterweight. The centrifugal force generated by the rotation of the counterweight piston 640 with the milling spindle 300 drives the pressure of the hydraulic linkage circuit 330 to increase synchronously with the speed, locking... The clamping force of the bushing 620 is increased synchronously, and the radial expansion within the milling spindle 300 is compensated in real time to achieve dynamic compensation of the clamping force. During high-speed milling, the milling vibration reduction component 700 integrated in the centrifugal compensation cylinder 630 absorbs and dissipates the alternating vibration generated by milling, ensuring the stability of the machining process. After the milling spindle 300 stops after machining, the counterweight piston 640 and the energy dissipation slider 720 automatically fall back along the inclined sliding cavity 631, the circuit pressure is automatically released, and the locking bushing 620 springs back to release the milling head 500. The milling head 500 can then be replaced manually or by the automatic tool changer 800.

[0064] This embodiment solves the problem of clamping force attenuation of the milling head 500 under high-speed conditions through a centrifugal hydraulic linkage structure with adaptive rotation speed; through centrifugal compensation and vibration reduction functions, it simultaneously achieves efficient suppression of clamping force compensation and milling vibration; through the design of the tilting centrifugal compensation cylinder 630, it realizes fully automatic pressure relief of the circuit after shutdown, adapting to the fully automatic tool change process; combined with the hydraulic circuit adapted to all working conditions and the high-precision positioning locking bushing 620 structure, it comprehensively takes into account the clamping accuracy, vibration resistance, operational safety and automation adaptability of the mechanism, and greatly improves the high-speed precision machining capability and long-term operational stability of the five-axis machining center.

[0065] Example 2

[0066] The difference between this embodiment and Embodiment 1 is that, referring to... Figure 13The locking bushing 620 is integrally formed with the body of the milling spindle 300, forming part of the cylindrical fitting section 322 hole wall, thereby adapting to different milling spindle 300 machining process requirements.

[0067] It should be noted that any reference signs placed between parentheses in the claims should not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The invention can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0068] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0069] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0070] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A five-axis machining center for metal processing, comprising a machine tool body (100), a milling spindle (300) mounted on the machine tool body (100) via a three-dimensional motion mechanism, and a milling head (500) mounted on the milling spindle (300), wherein the milling spindle (300) rotates at high speed under the drive of a drive motor (400) to drive the milling head (500) to rotate for milling processing, characterized in that: The end of the milling spindle (300) is provided with a milling head fixing mechanism (600) that is hydraulically clamped to facilitate fixing the milling head (500) on the milling spindle (300). The milling head fixing mechanism (600) includes: A closed hydraulic expansion chamber (610) is provided with a locking bushing (620) that can elastically deform along its radial direction, for holding the tool holder (520) of the milling head (500) to achieve positioning and locking. Multiple sets of centrifugal compensation cylinders (630) are evenly arranged around the circumference of the milling spindle (300). Each set of centrifugal compensation cylinders (630) is provided with a counterweight piston (640) that can slide in a direction close to or away from the hydraulic expansion chamber (610). The outer end of the counterweight piston (640) away from the hydraulic expansion chamber (610) forms a pressurization zone (632) with the centrifugal compensation cylinder (630) and is connected to the hydraulic expansion chamber (610) through the oil passage built into the milling spindle (300), forming a closed hydraulic linkage circuit (330). The hydraulic linkage circuit (330) is filled with hydraulic oil. The milling vibration reduction assembly (700) includes a vibration damping spring (710) and an energy dissipation slider (720) coaxially disposed in a centrifugal compensation cylinder (630). The energy dissipation slider (720) is connected to the inner end face of a counterweight piston (640) through the vibration damping spring (710) to reduce the vibration generated during milling and maintain the stability of milling. The centrifugal compensation cylinder (630) is inclined along the axial direction of the milling spindle (300) toward the end away from the milling head (500), and a sliding cavity (631) is formed therein for the counterweight piston (640) to slide. The pressurization zone (632) is located on the side of the sliding cavity (631) away from the hydraulic expansion cavity (610) and is connected to the hydraulic linkage circuit (330). The extension line of the central axis of the sliding cavity (631) intersects the central axis of the milling spindle (300).

2. The five-axis machining center for metal processing according to claim 1, characterized in that: The energy dissipation slider (720) is slidably engaged with the sliding cavity (631), and the end face of the counterweight piston (640) extends coaxially into a hollow cylindrical extension (644). The damping spring (710) is located in the hollow area of ​​the extension (644), and the end face of the extension (644) is used to contact the end face of the energy dissipation slider (720) to form a stop structure.

3. The five-axis machining center for metal processing according to claim 1, characterized in that: The energy dissipation slider (720) is cylindrical and slides with the sliding cavity (631), and the energy dissipation slider (720) has a number of interconnected balance air holes (721) on both ends along its axial direction.

4. A five-axis machining center for metal processing according to claim 1, characterized in that: The bottom end of the milling spindle (300) forms a milling head fixing hole (320). The milling head fixing hole (320) includes a tapered positioning section (321), a cylindrical fitting section (322), and a pull claw section (323) with its opening facing the inside of the milling spindle (300). The milling head (500) includes a pull claw end (510), a cylindrical tool holder (520), a tapered shank end (530), a flange (540), a milling cutter connecting end (550), and a milling cutter body (560) arranged coaxially. The pull claw end (510) cooperates with the pull claw structure provided in the pull claw section (323) for pre-tightening the entire milling head (500). The hydraulic expansion chamber (610) is annular and coaxially arranged on the... Inside the cylindrical fitting section (322) of the milling head fixing hole (320), the locking bushing (620) is an annular thin-walled structure and is located on the side of the hydraulic expansion cavity (610) near the center of the cylindrical fitting section (322). The inner diameter of the locking bushing (620) in its free state is consistent with the hole diameter of the cylindrical fitting section (322) and flush with the hole wall of the cylindrical fitting section (322). The outer diameter of the locking bushing (620) facing the hydraulic expansion cavity (610) is larger than the hole diameter of the cylindrical fitting section (322). The milling spindle (300) is provided with a connecting oil passage, which connects the hydraulic expansion cavity (610) and the pressurization zone (632) to form a closed hydraulic linkage circuit (330).

5. A five-axis machining center for metal processing according to claim 4, characterized in that: The locking bushing (620) is integrally formed with the body of the milling spindle (300) and constitutes part of the hole wall of the cylindrical fitting section (322), or is an independent annular thin-walled structure located in the hydraulic expansion cavity (610) of the cylindrical fitting section (322).

6. A five-axis machining center for metal processing according to claim 4, characterized in that: The locking bushing (620) has a support portion (621) protruding on one side near the hydraulic expansion chamber (610), and the end of the support portion (621) extends to the side wall of the hydraulic expansion chamber (610) opposite it with a gap.

7. A five-axis machining center for metal processing according to claim 1, characterized in that: The hydraulic linkage circuit (330) is provided with a one-way hydraulic control valve (650) that is unilaterally open in the direction of the centrifugal compensation cylinder (630). The valve core of the one-way hydraulic control valve (650) is provided with a counterweight structure so as to drive the valve core to move in the reverse direction during the rotation of the spindle (300) used for milling to conduct the one-way hydraulic control valve (650).

8. A five-axis machining center for metal processing according to claim 1, characterized in that: The hydraulic linkage circuit (330) is equipped with an overflow valve (660).

9. A five-axis machining center for metal processing according to claim 1, characterized in that: The centrifugal compensation cylinders (630) are provided in at least three and are evenly arranged circumferentially around the milling spindle (300).

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