High-precision machining device for medical parts

Abstract

The invention belongs to the technical field of precision machining, and discloses a high-precision machining device for medical parts, which comprises a device shell and a cutter clamping head, a vibration generating assembly is arranged in the device shell, and the vibration generating assembly is connected with the cutter clamping head through linkage of a planetary gear train and a surface cam. The rotary motion of a machine tool spindle is converted into the reciprocating motion of a tool clamping head in the axial direction, the frequency range of the reciprocating motion is 500 Hz to 2000 Hz, the amplitude range is 5 micrometers to 20 micrometers, the structure enables a tool to cut a workpiece intermittently in a high-frequency impact mode, and continuous accumulation of heat is restrained from the physical source. Compared with the prior art, under the condition of not depending on high-pressure cooling, the thermal deformation rejection rate can be reduced from 6.2% to 0.8%, meanwhile, the material removal rate is increased by more than 210%, the service life of a tool is remarkably prolonged, the structure is reliable, and high-efficiency and high-precision machining of materials difficult to machine can be achieved with low cost.

Description

Technical Field

[0001] This invention relates to the field of precision machining technology, and more specifically, to a machining apparatus, particularly suitable for machining difficult-to-machine materials such as titanium alloys and nickel-based high-temperature alloys used in fields such as medical implants and key aerospace components. Background Technology

[0002] In high-end manufacturing fields such as medical implants and aero engines, difficult-to-machine materials such as titanium alloys are widely used.

[0003] However, the physical properties of these materials pose a significant challenge to machining. The core problem lies in their extremely low thermal conductivity, which is only 1 / 5 to 1 / 7 that of ordinary carbon steel. In traditional continuous cutting, the enormous cutting heat cannot be effectively dissipated and is highly concentrated in the cutting zone, resulting in local instantaneous temperatures reaching 800-1000°C. This high temperature not only accelerates tool wear but also causes uneven thermal expansion and enormous residual stress inside the workpiece. After the part is machined and cooled, the release of residual stress leads to unpredictable micro-warping and dimensional shrinkage, i.e., post-cooling deformation. For medical parts with stringent precision requirements, this factor alone can cause a scrap rate of 5% to 8% due to dimensional deviations. To address this problem, existing technologies generally adopt a force-controlled shape-water-controlled temperature paradigm, which involves enhancing the system's rigidity to counteract cutting forces and using ultra-high pressure internal cooling technology for powerful cooling.

[0004] However, this paradigm failed to solve the problem of heat accumulation at its physical source, leading the industry into a high-cost efficiency paradox: on the one hand, companies need to invest in expensive heavy machine tools and high-pressure cooling systems, and bear high energy consumption and cutting fluid treatment costs; on the other hand, in order to ensure yield, the process is forced to adopt conservative parameters of low speed, shallow layer and slow feed, resulting in extremely low material removal rate and low production efficiency.

[0005] In addition, although there has been exploration of ultrasonic-assisted machining (VAM) technology based on piezoelectric ceramics in this field, it has failed to become a universal and reliable industrial solution due to its inherent defects such as fragile actuators, inability to withstand heavy impacts, limited energy conversion efficiency, and complex and expensive systems. In summary, existing technologies fail to decouple the strong correlation between material removal and heat accumulation from the physical core of the cutting process, forcing companies to make ineffective trade-offs between high scrap costs and low production efficiency. Therefore, there is an urgent need in this field for a disruptive technological solution that can fundamentally change the cutting mechanism and synergistically achieve high efficiency and high precision. Summary of the Invention

[0006] The purpose of this invention is to provide a high-precision machining device for medical parts, which aims to overcome the problems of low machining accuracy, high scrap rate and low production efficiency caused by the accumulation of cutting heat in the prior art. By changing the cutting physical mechanism, heat generation is suppressed from the source, thereby achieving high-efficiency and high-precision machining in a coordinated manner.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A high-precision machining device for medical parts includes a device housing and a tool holder head. One end of the device housing is adapted to be connected to a machine tool spindle. The tool holder head is rotatably and axially reciprocatingly disposed within the device housing for holding a tool. The device also includes a vibration generating component disposed within the device housing. The vibration generating component is configured to convert the rotational motion of the machine tool spindle into the reciprocating motion of the tool holder head along its axial direction. The frequency range of the reciprocating motion is 500Hz to 2000Hz, and the amplitude range is 5μm to 20μm, thereby enabling the tool to perform high-frequency impact intermittent cutting on the workpiece while rotating.

[0008] Preferably, the vibration generating component includes: a power input component for receiving rotational power from the machine tool spindle; a vibration generating component, which is connected to the power input component for converting rotational motion into axial periodic thrust; a thrust transmission component that contacts the vibration generating component and is connected to the tool holder head; and an elastic reset component for applying a preload to the thrust transmission component to make it abut against the vibration generating component.

[0009] Preferably, the power input component is a planetary gear system, the central gear of which rotates synchronously with the machine tool spindle, the planet carrier is fixed on the device housing, and the vibration generating component is one or more face cams, the input shaft of each face cam is connected to the output shaft of a planet gear of the planetary gear system, and the end face of the face cam has multiple continuous wavy protrusions.

[0010] Preferably, the thrust transmission component is a thrust bearing ring, and the elastic reset component is a set of disc springs.

[0011] Preferably, the frequency range of the axial high-frequency reciprocating motion of the tool holder head is 500Hz to 2000Hz, and the amplitude range is 5 micrometers to 20 micrometers.

[0012] Preferably, the surface cam is made of cemented carbide with an ultra-hard coating, and the contour curve of the wavy protrusion is a cycloidal contour to achieve smooth acceleration and deceleration impact.

[0013] Compared with the prior art, the present invention has the following beneficial effects: This invention fundamentally solves the core technical problem caused by heat accumulation by changing the cutting physical mechanism, and thus generates a series of synergistic and significant technical benefits. High-frequency intermittent cutting introduces a microscopic time window for the tool to detach from the workpiece in each cutting cycle. During this window, the chips can be smoothly broken off and discharged, and the coolant can instantly penetrate between the tool tip and the workpiece to achieve direct quenching of the heat source, thereby avoiding the continuous accumulation of heat. This subversion of the mechanism directly brings about a simultaneous and significant improvement in machining quality, efficiency and tool life.

[0014] This invention achieves excellent processing performance while exhibiting high economic efficiency and industrial applicability. Its pure mechanical vibration generation structure is composed of mature and reliable industrial components such as planetary gear trains, face cams, thrust bearings, and disc springs. The structure is robust and fully adaptable to harsh workshop environments, with reliability far exceeding that of solutions based on precision components such as piezoelectric ceramics.

[0015] This invention reduces reliance on external cooling systems from a mechanistic perspective, making expensive ultra-high pressure cooling systems no longer necessary. This not only significantly lowers the investment threshold for the system, but also significantly reduces the overall energy consumption of single-piece processing by shutting down the high-pressure pump, a major energy consumer. While significantly reducing manufacturing costs, it is fully in line with the trend of green manufacturing. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of a high-precision machining device for medical parts according to the present invention. Figure 2 This is a core cross-sectional view of the internal structure of a high-precision machining device for medical parts according to the present invention. Figure 3 This is an exploded view of the vibration generation component in a high-precision machining device for medical parts according to the present invention. Figure 4 for Figure 2 Enlarged view of the fit between the mid-face cam and the thrust bearing ring at the beginning of the impact stroke.

[0017] Figure 5 for Figure 2 Enlarged view of the fit between the mid-face cam and the thrust bearing ring at the end of the impact stroke.

[0018] In the figure: 1-device housing; 2-tool clamping head; 3-vibration generating component; 31-power input component; 32-vibration generating component; 33-thrust transmission component; 34-elastic reset component. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] Example 1 Reference Figure 1 and Figure 2 As shown, the present invention provides a high-precision machining device for medical parts. The device includes a device housing 1 as a base. The rear end of the device housing 1 has a standard tapered shank, which is suitable for precision connection with the machine tool spindle of a machining center to receive rotational motion and torque from the machine tool spindle.

[0021] Inside the housing 1 of the device, there is a tool holder 2. The front end of the tool holder 2 is used to hold standard end mills and other tools by means of spring clips, etc. The tool holder 2 is designed to be able to rotate synchronously with the spindle at high speed inside the housing 1 of the device, and can also perform small-amplitude, high-frequency reciprocating linear motion along its own axis.

[0022] The device housing 1 is also equipped with a purely mechanical vibration generating component 3. The vibration generating component 3 has a compact structure and is completely encapsulated in the device housing 1. Its function is to convert the single, continuous rotational motion received from the machine tool spindle into a composite motion of synchronous rotational motion and axial high-frequency reciprocating motion of the tool holder head 2.

[0023] Reference Figure 2 and Figure 3 As shown, the internal structure and working principle of the vibration generating component 3 are described in detail: the vibration generating component 3 is composed of a power input component 31, a vibration generating component 32, a thrust transmission component 33, and an elastic reset component 34 working together. In this embodiment, the power input component 31 is preferably a precision planetary gear system, which includes a central gear, multiple planet gears, and a planet carrier. The central gear is fixedly connected to the input end of the device housing 1 and rotates synchronously with the machine tool spindle. The planet carrier is firmly fixed on the stationary device housing 1. According to the kinematic principle of planetary transmission, when the central gear rotates at an angular velocity ω_sun, due to the fixed planet carrier, there is a fixed high transmission ratio between the rotational angular velocity ω_planet of the planet gears and the angular velocity ω_sun of the central gear. It is by utilizing this kinematic characteristic that the rotational speed of the spindle is effectively increased through the planetary system, thereby providing a stable and powerful power source for the subsequent generation of high-frequency vibration. The vibration generating component 32 is directly connected to the output end of the power input component 31 and is the core of realizing the motion form conversion. In this embodiment, the vibration generating component 32 is composed of three face cams evenly distributed at 120 degrees. The input shaft of each face cam is rigidly connected to the output shaft of a planetary gear and rotates synchronously at high speed with the planetary gear.

[0024] like Figure 4 and Figure 5 As shown, the working end face of each cam is not flat, but is machined to have multiple continuous, smooth, wavy protrusions. To achieve smooth acceleration and deceleration impacts under high-speed operation and reduce impacts and vibrations, the contour curve of the wavy protrusions is preferably a cycloidal contour. From a kinematic perspective, the characteristic of cycloidal motion is that its displacement, velocity, and acceleration curves are continuous and smooth throughout the entire motion cycle. Especially at the beginning and end of the motion, its acceleration value is zero, thus theoretically eliminating rigid impacts. Rigid impacts, i.e., abrupt changes in acceleration, are also called infinite jumps. This is crucial for ensuring the smoothness of high-frequency motion, reducing noise, and extending the life of the mechanism. To ensure wear resistance and service life under long-term high-frequency impacts, the material of the cam is preferably WC-Co cemented carbide, and treated with a superhard coating such as TiAlN. The thrust transmission component 33 serves as a bridge for motion transmission. In this embodiment, it is preferably a high-rigidity thrust bearing ring. The thrust bearing ring is in direct contact with the wavy end faces of all face cams and is rigidly connected to the rear end of the tool holder head 2. Using a thrust bearing ring can effectively reduce the relative rotational friction between the face cams and the tool holder head, ensuring efficient energy transmission.

[0025] The elastic reset component 34 is used to provide strong preload and motion recovery force. In this embodiment, it is preferably a set of disc springs with extremely strong preload. The disc springs are precisely calculated and selected, and the preload they provide must be designed to be always greater than the maximum axial cutting force generated when machining difficult-to-machine materials at the maximum cutting depth and feed. This ensures that under any working condition, there will be no separation or gap between the thrust bearing ring 33 and the face cam 32 due to the reaction of the cutting force. This is a prerequisite for ensuring the rigidity and impact effectiveness of motion transmission.

[0026] The actual complete workflow of this invention is as follows: When the machine tool spindle starts, it drives the housing 1 and all internal components of the device to rotate together. At the same time, the rotation of the spindle drives the central gear of the planetary gear system to rotate. Since the planet carrier is fixed on the housing 1, the planet gears are forced to rotate at high speed. The high-speed rotation of the planet gears drives the face cam 32 connected to it to rotate at the same speed.

[0027] Reference Figure 4As shown, when the wave-shaped protrusion of the face cam rotates to its highest point, it pushes the thrust bearing ring 33, overcoming the huge preload of the disc spring assembly 34, thereby forcing the entire tool holder head 2, which is rigidly connected to the thrust bearing ring 33, to produce a small axial forward stroke, wherein the small axial forward stroke can specifically be 5 micrometers to 20 micrometers.

[0028] Reference Figure 5 As shown, when the convex point rotates past the highest point and enters the trough, under the strong elastic force of the disc spring assembly 34, the tool clamping head 2 is instantly pulled back, completing a backward stroke.

[0029] Since the face cam 32 rotates at high speed and has multiple continuous protrusions on its end face, this push-back action will be repeated at an extremely high frequency. Specifically, the extremely high frequency can be in the frequency range of 500Hz to 2000Hz. Finally, a high-frequency, micro-amplitude axial reciprocating motion is successfully superimposed on the high-speed rotation of the tool holder head 2, so that the cutting edge of the tool contacts the workpiece in a cyclic manner of feed-cutting-retraction-idle stroke, transforming the traditional continuous cutting into high-frequency impact intermittent cutting. In a specific, non-limiting embodiment, the device is designed to generate an axial vibration frequency of 1200 Hz and an amplitude of 15 μm. The face cam 32 is made of WC-Co cemented carbide and treated with a TiAlN coating. The disc spring assembly 34 is precisely calculated and selected to provide a preload sufficient to overcome the maximum axial cutting force generated when machining titanium alloys, ensuring that the thrust bearing ring 33 will not disengage from the face cam 32 under any operating conditions. In a specific, non-limiting embodiment, the device is designed to generate an axial vibration frequency of 1200 Hz and an amplitude of 15 μm. The face cam 32 is made of WC-Co cemented carbide and treated with a TiAlN coating. The disc spring assembly 34 is precisely calculated and selected to provide a preload sufficient to overcome the maximum axial cutting force generated when machining titanium alloys, ensuring that the thrust bearing ring 33 will not disengage from the face cam 32 under any operating conditions.

[0030] Taking the experiment of machining TC4 titanium alloy using the device of the present invention as an example, the data shows that: the hot deformation scrap rate dropped sharply from 6.2% to 0.8%, a decrease of more than 87%; since heat is no longer a limiting factor, the material removal rate (MRR) can be increased from 15.6 cm³ / min to 48.5 cm³ / min, an increase of more than 210%; at the same time, due to the significant reduction in the peak temperature of the cutting zone from about 850°C to about 550°C and the improvement in chip breaking effect, the average tool life is extended by 133%.

[0031] Example 2 The core inventive concept of this invention lies in converting rotational motion into axial high-frequency vibration through a purely mechanical means. Embodiment 1 shows a preferred scheme based on planetary gear-face cam, but those skilled in the art should understand that the specific structure for achieving this function is not unique.

[0032] In this embodiment, a modified structure of the vibration generating component 3 is provided, which eliminates the planetary gear system and instead adopts a direct-drive motor-cylindrical cam scheme.

[0033] Specifically, inside the housing 1 of the device, a miniature high-speed brushless motor is integrated. The output shaft of the motor drives a cylindrical cam to rotate directly or through a small reducer. A continuous groove with a sine or cycloidal profile is machined on the circumference of the cylindrical cam. A driven roller extends radially from the rear end of the tool holder head 2 and engages with the groove. When the motor drives the cylindrical cam to rotate, the roller, constrained by the groove, drives the entire tool holder head 2 to reciprocate along the axial direction. Similarly, a set of disc springs is used to eliminate backlash and apply preload.

[0034] The advantage of this variant is that the vibration frequency and amplitude can be electrically adjusted independently of the machine tool spindle speed, making it more adaptable to different processes. The disadvantage is that the introduction of a motor and electrical control system increases the complexity of the device and potential failure points. Furthermore, it requires solving the power supply and signal transmission problems on the machine tool. The existence of this variant proves that the scope of protection of this invention should not be limited to a specific mechanical implementation method, but rather to the higher-level inventive concept of building a pure mechanical vibration generation component to achieve intermittent cutting.

[0035] Example 3 The core technical principle of this invention is to solve the thermal barrier problem of difficult-to-machine materials through high-frequency impact intermittent cutting. This is not limited to medical titanium alloy processing, but also has significant application value in other high-end manufacturing fields.

[0036] This embodiment demonstrates the application extension of the core device of the present invention in the processing scenario of key components of aero-engines. In the precision milling of the tenon part of aero-turbine blades, the material is usually a nickel-based high-temperature alloy such as Inconel 718, which is even more difficult to process than titanium alloys. This is mainly due to its extremely low thermal conductivity and severe work hardening tendency. Work hardening refers to the phenomenon that the surface hardness of a material increases significantly during the plastic deformation process of cutting, which leads to a surge in subsequent cutting forces and accelerates tool wear. The high-frequency impact cutting device of the present invention was applied to this scenario for contour finishing of blade tenons. Experiments show that, compared with the solution of high-speed continuous cutting using traditional ceramic tools, the device of the present invention can achieve excellent results even when using ordinary carbide tools. The high-frequency micro-impact can effectively suppress the formation depth of the work-hardened layer because each impact is like a micro-forging, but its action time is extremely short and accompanied by rapid cooling, thereby changing the formation dynamics of the hardened layer. At the same time, intermittent cutting improves the cooling effect and avoids surface burns caused by high temperature.

[0037] The final experimental results show that, taking Inconel 718 material as an example, using the solution of this invention, the residual stress on the machined surface of the blade tenon is transformed from harmful tensile stress to beneficial compressive stress, and the surface integrity is significantly improved; at the same time, the tool life is increased by about 50% compared with the traditional solution, and the processing efficiency is also improved by nearly 80%.

[0038] This application example once again demonstrates the universality and significant technical value of the technical principles of this invention in the entire field of precision machining of difficult-to-machine materials, rather than just a case-specific solution for a particular working condition.

[0039] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

[0040] For example, the specific implementation of the vibration generation component is not limited to the planetary gear-face cam structure, but can also adopt other purely mechanical structures, such as a cylindrical cam driven by an integrated micro motor, as long as it can realize the function of converting the spindle rotation motion into the axial high-frequency reciprocating motion of the tool holder head, it falls within the protection scope of this invention.

Claims

1. A high-precision machining device for medical parts, comprising: The device housing (1) has one end adapted to be connected to the machine tool spindle; A tool clamping head (2), which is rotatably and axially reciprocatingly disposed within the device housing (1) for clamping a tool; characterized in that it further comprises: The vibration generating component (3) is disposed inside the housing (1) of the device. The vibration generating component (3) is configured to convert the rotational motion of the machine tool spindle into a high-frequency reciprocating motion of the tool holder head (2) along its axial direction. The frequency range of the reciprocating motion is 500Hz to 2000Hz, and the amplitude range is 5 micrometers to 20 micrometers, so that the tool performs high-frequency impact intermittent cutting on the workpiece while rotating.

2. The high-precision machining device for medical parts according to claim 1, characterized in that, The vibration generating component (3) includes: A power input component (31) is used to receive the rotational power of the machine tool spindle; The vibration generating component (32) is connected to the power input component (31) for converting rotational motion into axial periodic thrust; The thrust transmission component (33) contacts the vibration generating component (32) and is connected to the tool holder head (32); The elastic reset component (34) is used to apply a preload to the thrust transmission component (33) so that it abuts against the vibration generating component (32).

3. The high-precision machining device for medical parts according to claim 2, characterized in that, The power input component (31) is a planetary gear system, the central gear of which rotates synchronously with the machine tool spindle, and the planet carrier is fixed on the device housing (1); the vibration generating component (32) is one or more face cams, the input shaft of each face cam is connected to the output shaft of a planetary gear of the planetary gear system, and the end face of the face cam has multiple continuous wavy protrusions.

4. The high-precision machining device for medical parts according to claim 3, characterized in that, The thrust transmission component (33) is a thrust bearing ring, and the elastic reset component (34) is a set of disc springs.

5. The high-precision machining device for medical parts according to claim 3, characterized in that, The surface cam is made of cemented carbide with an ultra-hard coating, and the contour curve of the wavy protrusion is a cycloidal contour.

6. A processing method using the high-precision processing apparatus for medical parts according to any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Connect the device housing (1) to the machine tool spindle and clamp the tool on the tool holder (2); Step 2: Start the machine tool spindle and drive the device housing (1) and all internal components to rotate. At the same time, the vibration generating component (3) converts the rotational motion of the machine tool spindle into the axial reciprocating motion of the tool holder (2), so that the tool performs intermittent cutting on the workpiece.

Images