A non-standard thread milling cutter for medical use and a preparation process thereof

Abstract

This application relates to a non-standard thread milling cutter for medical use and its manufacturing process, belonging to the technical field of medical device machining tools, including a tool bar and thread machining. This application has the effect of improving tool life and thread machining accuracy. The left end of the tool bar has multiple sets of thread teeth, the thread teeth have asymmetrical first half angle and second half angle, the thread teeth have unloading grooves at the bottom of the thread teeth, and the thread teeth surface is coated with a composite coating. The manufacturing process includes precision grinding, sandblasting pretreatment, coating deposition, cutting edge polishing and scale calibration. It relies on non-standard staggered angles to compensate for workpiece springback, and the allowance layer combined with the scale achieves multiple tool compensations. The double coating improves wear resistance. It has high fit and good tooth profile consistency when machining titanium alloy and PEEK orthopedic implant threads, and significantly improves tool life.

Description

Technical Field

[0001] This application relates to the technical field of cutting tools for medical device processing, and in particular to a non-standard thread milling cutter for medical use and its manufacturing process. Background Technology

[0002] Orthopedic implant thread forming relies on thread milling cutters for cutting. The thread milling cutter uses carbide rods as the base material and mills the external thread profile through the outer helical tooth shape. The coating on the tooth surface of the cutter can reduce cutting friction and improve wear resistance. The finished implant thread directly determines the stability of bone integration. The industry standard thread milling cutter adopts a symmetrical tooth structure and is suitable for thread milling of general metal materials.

[0003] Traditional medical thread milling cutters lack crossover compensation angles. When machining titanium alloys and PEEK materials, thread springback causes large meshing gaps, and there is no reserved radial grinding allowance. After wear, they cannot be repaired and must be scrapped. The single-layer wear-resistant coating has insufficient wear resistance. After batch processing, the tooth profile angle offset is large, and the finished threads need to be polished. Both the processing consistency and production cost are difficult to meet the high standard production requirements of medical implants. Summary of the Invention

[0004] The purpose of this application is to provide a non-standard thread milling cutter for medical use and its manufacturing process, so as to solve the problems in the background art mentioned above.

[0005] This application provides a non-standard thread milling cutter for medical use, which adopts the following technical solution: it includes a tool bar, and the left end of the tool bar is provided with a machining thread;

[0006] The machining thread includes a thread tooth, a first half angle, a second half angle, and an unloading groove. The outer left end of the tool bar is provided with no less than two sets of thread teeth. The left end of the thread tooth is the first half angle, the right end is the second half angle, and the bottom end of the thread tooth is provided with an unloading groove. The outer side of the machining thread is provided with a composite coating.

[0007] By adopting the above technical solution, medical threads can be milled by using the machining thread on the left end of the tool bar. The first half angle and the second half angle on both sides of the thread teeth and the unloading groove at the bottom end can effectively improve the milling efficiency. The composite coating on the outer side of the machining thread improves the wear resistance of the tooth surface, and the simultaneous cutting of multiple sets of thread teeth improves the machining efficiency.

[0008] Preferably, the composite coating includes a base layer and an outer layer, wherein the base layer is coated on the outside of the machined thread, and the outer layer is provided on the outside of the base layer.

[0009] By adopting the above technical solution, the bottom layer adheres to the surface of the machined thread to enhance the coating adhesion, and the outer layer directly contacts the workpiece for cutting, which greatly improves the tool's wear resistance and high temperature resistance, and extends the service life of a single machining operation.

[0010] Preferably, the tool bar stock is made of ultra-fine grain cemented carbide.

[0011] By adopting the above technical solutions, the matrix of the tool bar stock has high hardness and fine grains, and the cutting edge is not prone to plastic deformation during the cutting process. It can stably maintain the thread profile angle during long-term machining, thus meeting the high-precision batch machining requirements of medical implants.

[0012] Preferably, the thread profile of the machined thread is a non-standard staggered angle design.

[0013] By adopting the above technical solutions, the non-standard staggered angle design can offset the elastic rebound after cutting medical materials such as titanium alloy and PEEK, allowing the machined threads to mesh tightly with the matching parts and reducing micro-motion wear during the use of implants.

[0014] Preferably, the first half-angle α = 29.8° ± 0.2°, the second half-angle β = 30.2° ± 0.2°, forming an interlacing angle of 0.4° ± 0.1°, and the thread tip adopts a rounded transition.

[0015] By adopting the above technical solution, the angles of the first half angle and the second half angle are defined to form a fixed staggered compensation angle. Combined with the arc transition structure at the tip of the thread tooth, the stress concentration caused by the sharp edge of the tooth tip is effectively eliminated. At the same time, the workpiece deformation is accurately compensated, the thread meshing fit is improved, and the workpiece does not need to be polished twice.

[0016] Preferably, the thread teeth are provided with a grinding allowance layer radially from the tooth tip to the tooth root, and each tooth is marked with a wear scale line axially.

[0017] By adopting the above technical solution, the grinding allowance layer, combined with the axially arranged wear scale lines, allows the radial wear amount to be determined based on the scale after the tool wears out. This supports multiple machine tool compensation corrections, extends the tool's service life, and reduces the cost of medical tool consumables.

[0018] This application provides a manufacturing process for a non-standard thread milling cutter for medical use, comprising the following steps:

[0019] S1: Precision grinding of the substrate: The tool bar is clamped in a five-axis CNC tool grinder and the tooth shape is processed by passing it through a rough grinding wheel and a fine grinding wheel in sequence;

[0020] S2: High surface roughness pretreatment: The ground tool is placed in an ultrasonic cleaner for 10 minutes and then subjected to micro-blasting treatment;

[0021] S3: Composite coating deposition: The bottom layer and the outer layer are deposited sequentially using a cathode arc ion plating device;

[0022] S4: Edge dulling and finishing: The tool is polished with a nylon brush, with the polishing direction perpendicular to the edge.

[0023] S5: Wear allowance calibration and inspection: A wear scale ring is marked on the tool shank using a laser marking machine, and the initial geometric accuracy of the tool is checked at the same time.

[0024] Preferably, in step S1, the coarse grinding wheel has a grit size of 120#, with a margin of 0.10mm, and then the final tooth shape is machined using a fine grinding wheel with a grit size of 800#.

[0025] By adopting the above technical solutions, the coarse grinding wheel can quickly remove excess matrix material, the fine grinding wheel can ensure the accuracy of the thread profile dimensions, and the combination of grinding wheel grit sizes takes into account both processing efficiency and forming accuracy.

[0026] Preferably, in step S2, 200-mesh alumina sand is used, the sandblasting pressure is 0.2 MPa, the distance is 100 mm, and the time is 30 seconds.

[0027] By adopting the above technical solution, a uniform micro-uneven structure is formed on the surface of the machined thread, providing anchoring points for the composite coating, improving the adhesion of the coating, and preventing the coating from falling off during the cutting process.

[0028] Preferably, the bottom layer is CrN, the argon flow rate is 200 sccm, the nitrogen flow rate is 400 sccm, the bias voltage is -150V, the target current is 80A, and the time is 10 minutes; the outer layer is AlTiN, the nitrogen flow rate is adjusted to 600 sccm, the bias voltage is -80V, the target current is 120A, and the time is 60 minutes.

[0029] By adopting the above technical solution, the deposition parameters corresponding to the bottom layer and the outer layer are limited, the coating thickness and internal crystal structure are precisely controlled, and the bottom layer and the outer layer work together to significantly improve the high temperature resistance and friction resistance of the cutting tool.

[0030] In summary, this application includes the following beneficial technical effects:

[0031] 1. This application utilizes a machining thread located on the left end of the tool bar. The machining thread includes a thread tooth, a first half-angle, a second half-angle, an unloading groove, and a composite coating. The outer side of the thread tooth is provided with a first half-angle and a second half-angle, and is combined with an unloading groove at the bottom of the thread tooth and an arc transition structure at the top of the thread tooth to form a non-standard staggered angle tooth profile. Compared with traditional symmetrical tooth profile tools, it can offset the elastic rebound of medical workpiece cutting, the unloading groove disperses cutting stress to avoid edge chipping, improves thread meshing fit, and achieves the required surface finish of the milled thread. It eliminates the need for a secondary polishing process and ensures uniform and stable thread dimensions in batch processing.

[0032] 2. This application achieves multiple precise tool replacements by setting a radial grinding allowance layer from the top to the bottom of the thread teeth, combined with the axial wear scale line and the composite coating on the outer side of the machined thread. Compared with traditional tools that have no wear allowance and are scrapped when worn, this application achieves multiple precise tool replacements with a base allowance of 0.12mm. In addition, the bottom layer of the composite coating can enhance the adhesion and the outer layer can delay the surface wear, which can significantly extend the tool life and reduce the cost of consumables for processing orthopedic implants.

[0033] 3. This application uses a tool bar made of ultra-fine grain cemented carbide material, and performs thread forming through standardized preparation processes in steps S1-S5. The ultra-fine grain matrix has high hardness and is not easily deformed by plasticity. Through a combination of five-axis grinding, ion plating coating, and cutting edge polishing, compared with existing ordinary processing technology, it can stably control the tooth profile angle, coating adhesion and cutting edge blunt roundness accuracy. The tooth profile angle changes very little after continuous processing, which can effectively meet the high-precision and high-consistency mass production specifications of medical devices.

[0034] 4. This application utilizes a composite coating applied to the outer side of the machined thread. The composite coating consists of a CrN base layer and an AlTiN outer layer. Combined with the micro-blasting pretreatment process in step S2, an anchoring microstructure is formed on the thread surface. Compared to the shortcomings of traditional single-layer coatings, which are prone to peeling and have poor high-temperature resistance, the base layer of this application can firmly adhere to the outer side of the thread, and the outer layer has high wear resistance and high-temperature resistance. The blasting pretreatment further strengthens the coating bonding strength. When cutting difficult-to-machine medical titanium alloys, the coating is not easy to peel off, thus ensuring the cutting performance of the tool. Attached Figure Description

[0035] Figure 1 This is a front view structural diagram of this application;

[0036] Figure 2 yes Figure 1 A magnified view of part A in the middle;

[0037] Figure 3 This is a schematic diagram of the machining thread structure of this application;

[0038] Figure 4 This is a schematic diagram of the composite coating structure of this application;

[0039] Figure 5 This is a schematic diagram of the preparation process of this application;

[0040] Explanation of reference numerals in the attached drawings: 1. Tool bar stock; 2. Machining thread; 21. Thread tooth; 22. First half angle; 23. Second half angle; 24. Unloading groove; 25. Composite coating; 251. Bottom layer; 252. Outer layer. Detailed Implementation

[0041] The following is in conjunction with the appendix Figure 1- Appendix Figure 5 This application will be described in further detail below.

[0042] A non-standard thread milling cutter for medical use, as shown in the reference. Figures 1-4 The tool bar 1 is made of ultra-fine grain cemented carbide with a grain size ≤0.4μm and an HRC hardness ≥92. This results in high matrix hardness and dense grains in the tool bar 1, making the cutting edge less prone to plastic deformation during cutting. Long-term machining allows for stable maintenance of the thread profile angle, meeting the high-precision batch processing requirements of medical implants. The left end of the tool bar 1 is machined with a thread 2. The thread profile of the machined thread 2 is a non-standard staggered angle design, which can counteract the elastic rebound after cutting medical materials such as titanium alloy and PEEK, ensuring a tight meshing between the machined thread and the matching part, reducing fretting wear during implant use. The machined thread 2 includes thread teeth 21, a first half-angle 22, a second half-angle 23, and a unloading groove 24. The outer left end of the tool bar 1 has at least two sets of thread teeth. The threaded tooth 21 has a first half-angle 22 at its left end and a second half-angle 23 at its right end. The first half-angle 22α=29.8°±0.2° and the second half-angle 23β=30.2°±0.2°, forming an alternating angle of 0.4°±0.1°. The top of the threaded tooth 21 is rounded with a radius of 0.05~0.10mm. The bottom of the threaded tooth 21 is provided with a relief groove 24, which is 0.10mm wide and 0.03mm deep. The radial clearance angle of the cutting tool is 8°±1° and the axial clearance angle is 5°±0.5°. The outer side of the machined thread 21 is provided with a composite coating 25. Furthermore, the threaded tooth 21 has a 0.12mm grinding allowance layer radially from the tooth tip to the tooth bottom, and each tooth is marked with a wear scale line along the axial direction, with each wear scale line being a division every 0.02mm.

[0043] Specifically, medical threads can be milled using the machining thread 2 on the left end of the tool bar 1. The thread teeth 21, in conjunction with the first half angle 22 and the second half angle 23 on both sides and the unloading groove 24 at the bottom, can effectively improve milling efficiency. The composite coating 25 on the outer side of the machining thread 2 enhances the wear resistance of the tooth surface. Simultaneous cutting of multiple sets of thread teeth 21 improves machining efficiency. At the same time, by limiting the angles of the first half angle 22 and the second half angle 23, a fixed staggered compensation angle is formed. Combined with the arc transition structure at the top of the thread teeth 21, stress concentration caused by the sharp edges of the tooth tip is effectively eliminated. At the same time, the workpiece deformation is accurately compensated, the thread meshing fit is improved, and the machined workpiece does not require secondary polishing. Furthermore, the grinding allowance layer, in conjunction with the axially arranged wear scale lines, allows the radial wear amount to be judged according to the scale after the tool wears. This supports multiple machine tool tool compensation corrections, extends the tool's service life, and reduces the cost of medical tool consumables.

[0044] Reference Figure 4The composite coating 25 includes a bottom layer 251 and an outer layer 252. The bottom layer 251 is CrN with a thickness of 0.5μm, which is deposited on the outside of the machined thread 2 by using a cathodic arc ion plating device. The outer layer 252 is AlTiN with a thickness of 2.0μm, which is deposited on the outside of the bottom layer 251. After coating, the surface roughness of the tool Ra is ≤0.04μm.

[0045] Specifically, the bottom layer 251 adheres to the surface of the machined thread 2 to enhance the coating adhesion, while the outer layer 252 directly contacts the workpiece for cutting, significantly improving the tool's wear resistance and high-temperature resistance, and extending its service life per machining cycle.

[0046] A manufacturing process for a non-standard thread milling cutter for medical use, referring to Figure 5 It includes the following steps:

[0047] S1: Precision grinding of the base material: The tool bar 1 is clamped in a five-axis CNC tool grinder. First, the thread tooth profile is ground out by a coarse grinding wheel with a grit of 120#, leaving a margin of 0.10mm. Then, the final tooth shape is machined by a fine grinding wheel with a grit of 800#. The deviation of the stagger angle is ≤±0.1°, and the deviation of the tooth tip radius is ≤0.01mm. During operation, the coolant pressure is ≥5MPa and the flow rate is ≥30L / min to ensure no burning.

[0048] S2: High surface roughness pretreatment: After grinding, the tool is placed in an ultrasonic cleaner and cleaned at 40kHz and 80℃ for 10 minutes. Then, it is micro-blasted with 200-mesh alumina abrasive particles at a blasting pressure of 0.2MPa, a distance of 100mm, and a time of 30 seconds. After blasting, the tool surface is uniformly matte with no residual grinding marks. Ra is controlled at 0.15~0.20μm to provide anchoring points for the coating.

[0049] S3: Composite Coating Deposition: Using a cathodic arc ion plating equipment, a CrN underlayer 251 was first deposited with an argon flow rate of 200 sccm, a nitrogen flow rate of 400 sccm, a bias voltage of -150V, a target current of 80A, and a time of 10 minutes. Then, an AlTiN outer layer 252 was deposited with the nitrogen flow rate adjusted to 600 sccm, a bias voltage of -80V, a target current of 120A, and a time of 60 minutes. At the same time, the furnace temperature was controlled at 450±10℃. The coating adhesion was measured to be ≥80N using the scratch method. The coating phase structure was determined by XRD to be single-phase with no other impurities.

[0050] S4: Edge passivation and finishing: After coating, the tool is polished with a nylon brush containing diamond micro powder with a particle size of 1μm. The brush speed is 2000rpm, the polishing direction is perpendicular to the edge, and each edge is polished for 5-8 seconds. After polishing, the blunt radius of the cutting edge is controlled at 5-8μm. The roughness Ra of the tool's rake face is measured with a white light interferometer and is ≤0.05μm. There are no micro-chips on the cutting edge, and no missing teeth larger than 2μm are found under a 200x microscope.

[0051] S5: Wear allowance calibration and inspection: A laser marking machine is used to mark wear scale rings on the tool shank, with each ring corresponding to a radial wear of 0.02mm. At the same time, a coordinate measuring machine is used to inspect the tooth profile accuracy, which is ±0.002mm and the tooth angle accuracy is ±0.2°.

[0052] This application provides a non-standard thread milling cutter for medical use and its manufacturing process. The non-standard staggered thread teeth 21, unloading grooves 24, and arc-shaped top structure on the tool bar 1 can offset workpiece springback, disperse cutting stress, and improve thread engagement accuracy. The finished product does not require secondary polishing. The thread teeth 21 are equipped with a radial grinding allowance layer and scale lines, combined with a double-layer composite coating 25, allowing for multiple tool repairs, delaying surface wear, extending tool life, and reducing machining material costs. The tool bar 1, made of ultra-fine grain cemented carbide, combined with a complete set of standardized manufacturing processes, is less prone to plastic deformation, ensuring stable tooth profile accuracy and adapting to high-precision batch processing of medical workpieces. The double-layer composite coating 25 on the outer side of the machined thread 2, combined with sandblasting pretreatment, results in strong coating adhesion, wear resistance, and high-temperature resistance, preventing it from peeling off when cutting titanium alloys and ensuring consistently stable cutting performance.

Claims

1. A non-standard thread milling cutter for medical use, characterized in that, Includes a cutting tool bar (1), the left end of which is provided with a machining thread (2); The machining thread (2) includes a thread tooth (21), a first half angle (22), a second half angle (23) and a load relief groove (24). The outer left end of the tool bar (1) is provided with no less than two sets of thread teeth (21). The left end of the thread tooth (21) is the first half angle (22) and the right end is the second half angle (23). The bottom end of the thread tooth (21) is provided with a load relief groove (24). The outer side of the machining thread (2) is provided with a composite coating (25).

2. The non-standard thread milling cutter for medical use according to claim 1, characterized in that, The composite coating (25) includes a base layer (251) and an outer layer (252). The base layer (251) is coated on the outside of the machined thread (2), and the outer layer (252) is provided on the outside of the base layer (251).

3. A non-standard thread milling cutter for medical use according to claim 1, characterized in that, The tool bar (1) is made of ultra-fine grain cemented carbide.

4. A non-standard thread milling cutter for medical use according to claim 1, characterized in that, The thread profile of the machining thread (2) is a non-standard staggered angle design.

5. A non-standard thread milling cutter for medical use according to claim 1, characterized in that, The first half angle (22) α = 29.8° ± 0.2°, the second half angle (23) β = 30.2° ± 0.2°, forming an interlacing angle of 0.4° ± 0.1°, and the top of the thread tooth (21) adopts a rounded transition.

6. A non-standard thread milling cutter for medical use according to claim 1, characterized in that, The thread tooth (21) has a grinding allowance layer radially from the tooth tip to the tooth bottom, and each tooth is marked with a wear scale line axially.

7. A manufacturing process for a non-standard thread end mill for medical use, characterized in that, Includes the following steps: S1: Precision grinding of the base material: The tool bar (1) is clamped in a five-axis CNC tool grinder and the tooth shape is processed by the coarse grinding wheel and the fine grinding wheel in sequence; S2: High surface roughness pretreatment: The ground tool is placed in an ultrasonic cleaner for 10 minutes and then subjected to micro-blasting treatment; S3: Composite coating deposition: The bottom layer (251) and the outer layer (252) are deposited sequentially using a cathode arc ion plating equipment. S4: Edge dulling and finishing: The tool is polished with a nylon brush, with the polishing direction perpendicular to the edge. S5: Wear allowance calibration and inspection: A wear scale ring is marked on the tool shank using a laser marking machine, and the initial geometric accuracy of the tool is checked at the same time.

8. The manufacturing process of a non-standard thread milling cutter for medical use according to claim 7, characterized in that, In step S1, the coarse grinding wheel has a grit size of 120#, with a margin of 0.10mm, and then the fine grinding wheel with a grit size of 800# is used to process the final tooth shape.

9. The manufacturing process of a non-standard thread milling cutter for medical use according to claim 7, characterized in that, In step S2, 200-mesh alumina sand is used, the sandblasting pressure is 0.2 MPa, the distance is 100 mm, and the time is 30 seconds.

10. The manufacturing process of a non-standard thread milling cutter for medical use according to claim 7, characterized in that, The bottom layer (251) is CrN, with an argon flow rate of 200 sccm, a nitrogen flow rate of 400 sccm, a bias voltage of -150V, a target current of 80A, and a time of 10 minutes. The outer layer (252) is AlTiN, with the nitrogen flow rate adjusted to 600 sccm, a bias voltage of -80V, a target current of 120A, and a time of 60 minutes.

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