Liquid nitrogen internal cooling type T-shaped milling cutter

Abstract

The application provides a liquid nitrogen internal cooling type T-shaped milling cutter and relates to the technical field of cutting processing. The liquid nitrogen internal cooling type T-shaped milling cutter comprises a handle transition zone main channel for passing in liquid nitrogen, a radial multilayer variable cross-section channel in a cutter head, a plurality of multistage diffusion composite outlets, the multistage diffusion composite outlets are correspondingly communicated with variable cross-section lateral C-shaped branch channels, and the multistage diffusion composite outlets are arranged at the edges where the bottoms of the chip flutes of the T-shaped milling cutter meet the flank faces of the side edges. The multistage diffusion composite outlets make the liquid nitrogen uniformly distribute in the circumferential direction and be radially drained to the rear of the side edges, meanwhile, the flow characteristics are optimized by using the channel design that the inner diameter first increases and then decreases, and the precise cooling diffusion is realized by cooperating with the multistage diffusion composite outlets, the problems of uneven cooling and insufficient structural strength caused by the "thin handle-wide head" structure of the T-shaped milling cutter are effectively overcome, the direct cooling of the cutting area can be realized, the cutting temperature is significantly reduced, and thus the cooling efficiency is improved, the tool life is prolonged, and the cutting stability is ensured.

Description

Technical Field

[0001] This invention relates to the field of cutting technology, and more specifically, to a liquid nitrogen internally cooled T-slot milling cutter. Background Technology

[0002] Currently, flat-end mills often use a center hole or radial holes along the helical groove to deliver cooling media such as liquid nitrogen to the vicinity of the cutting edge, thereby achieving efficient cooling and reducing tool wear. However, this type of design is mainly for the structural characteristics of end mills with constant diameter, and their internal channels usually extend linearly along the axial direction or follow the direction of the helical groove, forming a relatively simple flow channel layout.

[0003] However, this layout cannot be directly adapted to the special structure of T-slot end mills because T-slot end mills have a significant "narrow shank-wide head" characteristic, meaning the shank portion has a smaller diameter while the head portion has a larger diameter, resulting in extremely limited head space and a complex geometry. In T-slot end mills, if an axial straight hole design is used, liquid nitrogen cannot diffuse evenly to all side cutting edge areas of the head, causing insufficient local cooling.

[0004] Furthermore, existing liquid nitrogen delivery tools mostly rely on topology-optimized multi-layer network channels and multi-stage outlets. These channels are primarily axially extended, with branch channels distributed along the helical grooves. The outlets are concentrated at the bottom of the helical grooves and the transition fillet area between the flank face and the cutter. However, the chip flutes of T-slot end mills are usually straight or have a very small helical angle, and the side cutting edges are evenly distributed along the circumference. Therefore, cooling channels are required to guide liquid nitrogen from the center shank to the rear of the circumferential side cutting edges radially or circumferentially. This means that existing cooling systems cannot effectively solve the cooling problem of T-slot end mills, resulting in excessively high cutting temperatures and shortened tool life. Summary of the Invention

[0005] The problem this invention addresses is how to reduce the cutting temperature of a T-slot milling cutter, thereby improving cooling efficiency, extending tool life, and ensuring cutting stability.

[0006] To address the above problems, the present invention provides a liquid nitrogen internally cooled T-type end mill, comprising: The shank transition zone main channel for introducing liquid nitrogen passes through the shank of the T-slot cutter along the axial direction of the T-slot cutter and extends into the cutter head; The radial multi-layer variable cross-section channel located within the cutter head includes an annular collection cavity and multiple variable cross-section lateral C-shaped branch channels. The annular collection cavity surrounds the main channel of the shank transition area along the circumference of the cutter head and communicates with the main channel of the shank transition area. The multiple variable cross-section lateral C-shaped branch channels are distributed along the circumference of the annular collection cavity. One end of each variable cross-section lateral C-shaped branch channel communicates with the annular collection cavity, and the other end extends radially along the cutter head to directly behind the rear face of the cutting edge. The inner diameter of each variable cross-section lateral C-shaped branch channel first increases and then decreases along the liquid nitrogen flow direction. Multiple multi-stage diffusion composite outlets are provided, and each of the multi-stage diffusion composite outlets is connected to the variable cross-section lateral C-shaped branch channel. The multi-stage diffusion composite outlets are arranged at the bottom of the chip removal groove of the T-type milling cutter and the edge where the side cutting edge meets the back face.

[0007] Optionally, the inner diameter of the main channel in the shank transition area gradually increases toward the cutting head.

[0008] Optionally, the main channel of the handle transition area is provided with low thermal conductivity microtexture.

[0009] Optionally, at least two annular collection cavities are provided, and the two annular collection cavities are distributed at an axial interval along the main channel of the handle transition area. Each annular collection cavity is connected to multiple variable cross-section lateral C-shaped branch channels.

[0010] Optionally, the liquid nitrogen internally cooled T-type end mill further includes a liquid nitrogen inlet for liquid nitrogen access. The liquid nitrogen inlet is located at the end of the main channel of the shank transition area away from the cutter head. The inner diameter of the liquid nitrogen inlet gradually decreases towards the cutter head and communicates with the main channel of the shank transition area. The inner wall of the liquid nitrogen inlet is provided with a pulse solenoid valve interface for closed-loop flow regulation.

[0011] Optionally, the multi-stage diffusion composite outlet includes a throttling buffer cavity and a porous diffusion surface structure, wherein the inner diameter of the throttling buffer cavity is larger than the inner diameter of the variable cross-section lateral C-shaped branch channel, and the porous diffusion surface structure is arranged on the edge.

[0012] Optionally, the number of the variable cross-section lateral C-shaped branch channels is the same as the number of the side blades.

[0013] Optionally, the liquid nitrogen internally cooled T-slot cutter further includes a PVD wear-resistant coating covering the side cutting edge and the rake face of the chip removal groove.

[0014] Optionally, the liquid nitrogen internally cooled T-type end mill further includes a reinforcing rib disposed inside the cutter head, one end of which is connected to the outer wall of the main channel of the shank transition area, and the other end extends radially along the cutter head.

[0015] Optionally, the T-shaped end mill is made of ultrafine grain WC-Ni cemented carbide, wherein the WC grain size is 0.2 to 0.4 μm and the Ni binder content is 10 to 12 wt%.

[0016] Compared with the prior art, the liquid nitrogen internally cooled T-slot cutter of the present invention, when using liquid nitrogen to cool the T-slot cutter, passes through the shank transition zone main channel along the axial direction of the T-slot cutter and extends into the cutter head. The shank transition zone main channel guides the flow of liquid nitrogen, realizing the axial delivery of liquid nitrogen into the cutter head. The liquid nitrogen then passes through an annular collection chamber around the shank transition zone main channel along the circumference of the cutter head and communicates with the shank transition zone main channel, allowing the liquid nitrogen delivered into the cutter head to be buffered by the annular collection chamber. After being stabilized and initially distributed by the annular collection chamber, the liquid nitrogen is then guided through multiple variable cross-section lateral C-shaped branch channels to the rear of the back face of each side cutting edge on the circumference. The inner diameter of the C-shaped branch channel increases and then decreases along the direction of liquid nitrogen flow. The multi-stage diffusion composite outlet is connected to the variable cross-section lateral C-shaped branch channel. The multi-stage diffusion composite outlet is located at the bottom of the chip vent of the T-slot milling cutter and the edge where it intersects with the back face of the side cutting edge. This allows the liquid nitrogen to be evenly distributed circumferentially and radially guided to the back of the side cutting edge. At the same time, the channel design with an inner diameter that increases and then decreases optimizes the flow characteristics. Combined with the multi-stage diffusion composite outlet, it achieves precise cooling diffusion, effectively overcoming the problems of uneven cooling and insufficient structural strength caused by the "narrow shank-wide head" structure of the T-slot milling cutter. It can achieve direct cooling of the cutting area, significantly reduce the cutting temperature, thereby improving cooling efficiency, extending tool life, and ensuring cutting stability. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the main channel of the handle transition area, the annular collection cavity, the variable cross-section lateral C-shaped branch channel, and the reinforcing ribs in an embodiment of the present invention. Figure 2 This is a schematic diagram of the liquid nitrogen internally cooled T-type end mill in an embodiment of the present invention; Figure 3 This is a schematic diagram of the variable cross-section lateral C-shaped branch channel in an embodiment of the present invention; Figure 4 This is a cross-sectional view of the liquid nitrogen internally cooled T-type end mill in an embodiment of the present invention; Figure 5 This is a cross-sectional view of the reinforcing rib in an embodiment of the present invention; Figure 6 This is a schematic diagram of the liquid nitrogen inlet in an embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of the multi-stage diffusion composite outlet in an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures: 1-Main channel of shank transition area; 2-T-type end mill; 21-Tool holder; 22-Tool head; 23-Edge; 3-Radial multi-layer variable cross-section channel; 31-Annular collection cavity; 32-Variable cross-section lateral C-shaped branch channel; 4-Multi-stage diffusion composite outlet; 41-Throttling buffer cavity; 42-Porous diffusion surface structure; 5-Liquid nitrogen inlet; 51-Pulse solenoid valve interface; 6-Reinforcing rib. Detailed Implementation

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0020] In the attached figures, the X-axis represents left and right positions, with the positive direction of the X-axis representing the right side and the negative direction representing the left side; the Y-axis represents front and back positions, with the positive direction of the Y-axis representing the front and the negative direction representing the back; and the Z-axis represents up and down positions, with the positive direction of the Z-axis representing the top and the negative direction representing the bottom. It should be noted that the aforementioned representations of the X, Y, and Z axes are merely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0021] It should be noted that the terms "first," "second," etc., used in the specification and claims of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein.

[0022] Combination Figures 1 to 6 As shown, an embodiment of the present invention provides a liquid nitrogen internally cooled T-type end mill, comprising: The main channel 1 of the shank transition area is used for introducing liquid nitrogen. The main channel 1 of the shank transition area passes through the shank 21 of the T-slot milling cutter 2 along the axial direction of the T-slot milling cutter 2 and extends into the cutter head 22. The radial multi-layer variable cross-section channel 3 located inside the cutter head 22 includes an annular collection cavity 31 and multiple variable cross-section lateral C-shaped branch channels 32. The annular collection cavity 31 surrounds the main channel 1 of the shank transition area along the circumference of the cutter head 22 and is connected to the main channel 1 of the shank transition area. The multiple variable cross-section lateral C-shaped branch channels 32 are distributed along the circumference of the annular collection cavity 31. One end of each variable cross-section lateral C-shaped branch channel 32 is connected to the annular collection cavity 31, and the other end extends radially along the cutter head 22 to the rear of the back face of the cutting edge. The inner diameter of each variable cross-section lateral C-shaped branch channel 32 first increases and then decreases along the direction of liquid nitrogen flow. Multiple multi-stage diffusion composite outlets 4 are connected one-to-one with the variable cross-section lateral C-shaped branch channels 32. The multi-stage diffusion composite outlets 4 are arranged at the bottom of the chip removal groove of the T-type milling cutter 2 and the edge 23 where the side cutting edge meets the back face.

[0023] Specifically, such as Figure 4 As shown, the T-slot end mill includes a shank 21 and a cutter head 22 distributed from top to bottom, with the diameter of the cutter head 22 being larger than the diameter of the shank 21. The main channel 1 in the shank transition area is the main channel inside the T-slot end mill 2 for axial delivery of liquid nitrogen. The main channel 1 in the shank transition area runs from top to bottom through the shank 21 along the axial direction of the T-slot end mill 2 and extends to the bottom of the cutter head 22. The main channel 1 in the shank transition area does not penetrate the cutter head 22.

[0024] A radially multi-layered variable cross-section channel 3 is located inside the cutter head 22, comprising an annular collection cavity 31 and variable cross-section lateral C-shaped branch channels 32. The annular collection cavity 31 can be constructed as a single annular space, arranged inside the cutter head 22 around the axis of the main channel 1 in the shank transition zone. The inner wall of the annular collection cavity 31 is connected to the outer wall of the main channel 1 in the shank transition zone through multiple channels to deliver liquid nitrogen into the annular collection cavity 31. The variable cross-section lateral C-shaped branch channels 32 can be designed as several independent flow channels, with at least one variable cross-section lateral C-shaped branch channel 32 allocated within each cutting edge.

[0025] Multiple variable cross-section lateral C-shaped branch channels 32 are uniformly led out circumferentially from the annular collection chamber 31. Each variable cross-section lateral C-shaped branch channel 32 extends radially along the cutter head 22 until it reaches directly behind the flank face of the cutting edge. The inner diameter of each variable cross-section lateral C-shaped branch channel 32 can be designed to be smaller at the inlet, gradually expanding towards the middle section, and then gradually contracting towards the multi-stage diffusion composite outlet 4. The variable cross-section lateral C-shaped branch channels 32 form a Venturi effect structure to optimize the flow rate and pressure of liquid nitrogen. For example, the cross-section of the variable cross-section lateral C-shaped branch channel 32 first increases and then gradually contracts along the flow direction: the inlet section (near the annular collection chamber 31) has a φ1.0mm circular hole, the middle section gradually transitions to a rectangle with a width of 1.6mm and a height of 1.0mm, and the outlet section contracts to a φ0.8mm circular hole. The channel shape is generated as a smooth S-shaped curve through topology optimization and does not follow the linear direction of the chip removal groove. The multi-stage diffusion composite outlet 4 is connected to the end of the variable cross-section lateral C-shaped branch channel 32. The multi-stage diffusion composite outlet 4 is arranged on the edge 23 where the bottom of the chip vent of the T-slot milling cutter 2 intersects with the side cutting edge.

[0026] Therefore, in this embodiment, when using liquid nitrogen to cool the T-shaped end mill 2, the main channel 1 of the shank transition area passes through the shank 21 of the T-shaped end mill 2 along the axial direction and extends into the end mill 22. The main channel 1 of the shank transition area guides the flow of liquid nitrogen, realizing the axial delivery of liquid nitrogen into the end mill 22. The liquid nitrogen is then transported around the main channel 1 of the shank transition area along the circumference of the end mill 22 through the annular collection cavity 31 and communicates with the main channel 1 of the shank transition area. This allows the liquid nitrogen delivered into the end mill 22 to be buffered by the annular collection cavity 31. After being stabilized and initially distributed by the annular collection cavity 31, the liquid nitrogen is then guided to the rear of the back face of each side cutting edge on the circumference through multiple variable cross-section lateral C-shaped branch channels 32. The inner diameter of the C-shaped branch channel 32 increases and then decreases along the direction of liquid nitrogen flow. The multi-stage diffusion composite outlet 4 is connected to the variable cross-section lateral C-shaped branch channel 32. The multi-stage diffusion composite outlet 4 is arranged at the bottom of the chip groove of the T-end mill 2 and the edge 23 where it intersects with the back face of the side cutting edge. This allows the liquid nitrogen to be evenly distributed circumferentially and radially guided to the back of the side cutting edge. At the same time, the channel design with an inner diameter that increases and then decreases optimizes the flow characteristics. Combined with the multi-stage diffusion composite outlet 4, it achieves precise cooling diffusion, effectively overcoming the problems of uneven cooling and insufficient structural strength caused by the "narrow shank-wide head" structure of the T-end mill. It can achieve direct cooling of the cutting area, significantly reduce the cutting temperature, thereby improving cooling efficiency, extending tool life and ensuring cutting stability.

[0027] Based on the above embodiments, the T-shaped end mill 2 in this embodiment is manufactured using a hybrid manufacturing process: the complex internal cavity section (handle 21 and end mill 22) is manufactured by selective laser melting additive manufacturing using WC-9%Co powder printing, with a layer thickness of 30μm and a laser power of 170W; the printed part is precisely spliced ​​with the shank (φ16mm) of a traditional cemented carbide bar through vacuum brazing, with a coaxiality ≤0.01mm; then, it undergoes hot isostatic pressing (1250°C, 120MPa, 2h), deep cryogenic treatment (immersion in liquid nitrogen at -196°C for 24h), and precision grinding of the cutting edge; finally, the cutting edge is coated with PVD and the exit micro-hole is laser-machined. In use, the T-shaped end mill of this embodiment is mounted on a machine tool that supports a liquid nitrogen delivery system, and liquid nitrogen at a pressure of 3.0 bar is introduced. Liquid nitrogen enters the multi-layered network channel system (annular collection chamber 31 and variable cross-section lateral C-shaped branch channel 32) of the T-head through the main channel 1 in the shank transition zone, forming a spray at the multi-stage diffusion composite outlet 4 behind each side edge to cool the cutting area. Machining parameters: spindle speed 2500 r / min, feed rate 150 mm / min, axial depth of cut 8 mm, radial depth of cut 6.5 mm.

[0028] Optionally, combined Figure 2 As shown, the inner diameter of the main channel 1 in the shank transition area gradually increases towards the cutting head 22 within the shank 21.

[0029] Specifically, the main channel 1 of the shank transition area is located at the center of the shank 21. The inlet diameter of the main channel 1 of the shank transition area is φ3.5mm. It extends downward along the axial direction of the T-type milling cutter 2 and gradually expands to the bottom of the cutter head 22. The diameter at the bottom of the cutter head 22 is φ5.0mm.

[0030] Thus, the inner diameter of the main channel 1 in the shank transition zone gradually increases towards the cutter head 22, allowing liquid nitrogen to undergo a smooth diffusion process as it enters the cutter head 22 from the shank 21. This reduces pressure loss during liquid nitrogen flow within the channel and avoids eddies and energy dissipation caused by abrupt changes in cross-section. This also appropriately reduces the flow velocity of liquid nitrogen before it enters the annular collection chamber 31 of the cutter head 22, resulting in a more uniform pressure distribution. This provides more stable and uniform flow and pressure conditions for subsequent liquid nitrogen entry into the annular collection chamber 31 and the multiple variable cross-section lateral C-shaped branch channels 32. This ensures that liquid nitrogen can be efficiently and evenly delivered to all cutting edge areas within the cutter head 22, significantly improving the overall internal cooling efficiency and uniformity of the T-slot milling cutter 2, thereby extending tool life and improving machining performance.

[0031] Optionally, the main channel 1 of the handle transition area is provided with a low thermal conductivity microtexture.

[0032] Specifically, low thermal conductivity microtextures can be achieved in various ways. For example, a series of micron-sized grooves, protrusions, holes, or rough surfaces can be formed on the inner wall of the main channel 1 in the shank transition region by means of laser processing, chemical etching, or mechanical processing. For example, a spiral microgroove with a width of 0.1 mm, a depth of 0.03 mm, and a spacing of 0.3 mm is etched on the inner wall of the main channel 1 in the shank transition region using a nanosecond laser to form a low thermal conductivity microtexture.

[0033] Thus, by setting low thermal conductivity microtextures on the inner wall of the main channel 1 in the shank transition zone, the rate at which liquid nitrogen absorbs external heat as it flows through the inside of the shank 21 is effectively reduced. This allows the liquid nitrogen to be delivered to the cutter head 22 in a more stable, liquid state, reducing cooling capacity loss due to premature vaporization. Simultaneously, the microtextures' perturbation effect on fluid flow helps optimize the flow field distribution within the channel, reducing heat generated by friction during liquid nitrogen delivery and further ensuring the quality and stability of liquid nitrogen delivery. Combined with the gradual increase in inner diameter of the main channel 1 towards the cutter head 22, the low thermal conductivity microtextures help maintain a stable liquid state of liquid nitrogen before entering the cutter head 22, laying a solid foundation for efficient and uniform cooling in the radially multi-layered variable cross-section channel 3 within the cutter head 22, thereby improving the overall cutting performance and tool life of the T-slot end mill 2.

[0034] Optionally, combined Figure 1 and Figure 2As shown, at least two annular collection cavities 31 are provided. The two annular collection cavities 31 are distributed at intervals along the axial direction of the main channel 1 of the handle transition area. Each annular collection cavity 31 is connected to multiple variable cross-section lateral C-shaped branch channels 32.

[0035] Specifically, in the height direction of the cutter head 22, two annular collecting cavities 31 are distributed at intervals along the axial direction of the main channel 1 of the shank transition area. Each annular collecting cavity 31 is connected to multiple variable cross-section lateral C-shaped branch channels 32. The number of variable cross-section lateral C-shaped branch channels 32 connected to each annular collecting cavity 31 is consistent with the number of cutting edges of the T-shaped milling cutter 2. For example, if the number of cutting edges is 6, then the number of variable cross-section lateral C-shaped branch channels 32 connected to each annular collecting cavity 31 is 6.

[0036] Thus, by arranging the annular collection chambers 31 at axial intervals, liquid nitrogen can be more precisely distributed to the side cutting edge regions at different heights, ensuring the uniformity of the cooling medium's spatial distribution. Each annular collection chamber 31 is independently connected to multiple variable cross-section lateral C-shaped branch channels 32, allowing liquid nitrogen to be simultaneously delivered from multiple axial levels to the radially outer side cutting edge face. This not only enhances the cooling coverage but also reduces the pressure load on a single variable cross-section lateral C-shaped branch channel 32 through multi-level distribution, avoiding excessive local stress caused by overly concentrated flow channels. This makes the liquid nitrogen flow path more scientific and rational, and enables all-round, multi-dimensional cooling of the side cutting edge region based on the geometric characteristics of the T-shaped end mill 2 head. This significantly improves the tool's thermal stability under high-temperature cutting conditions, thereby extending tool life and improving machining accuracy.

[0037] Optionally, combined Figure 4 and Figure 6 As shown, the liquid nitrogen internally cooled T-type end mill also includes a liquid nitrogen inlet 5 for liquid nitrogen access. The liquid nitrogen inlet 5 is located at the end of the main channel 1 of the shank transition area away from the cutter head 22. The inner diameter of the liquid nitrogen inlet 5 gradually decreases towards the cutter head 22 and is connected to the main channel 1 of the shank transition area. The inner wall of the liquid nitrogen inlet 5 is provided with a pulse solenoid valve interface 51 for closed-loop flow regulation.

[0038] Specifically, the liquid nitrogen inlet 5 can be a threaded interface or quick connector that directly connects to an external liquid nitrogen supply pipeline. A sealing gasket ensures a tight seal. The liquid nitrogen inlet 5 is located at the upper end of the main channel 1 in the shank transition area and communicates with it. The inner diameter of the liquid nitrogen inlet 5 gradually decreases towards the cutter head 22; that is, the inner diameter of the liquid nitrogen inlet 5 can gradually decrease in a tapered shape, forming a smooth contraction section to optimize hydrodynamic performance. Simultaneously, a pulse solenoid valve interface 51 is provided on the side wall of the liquid nitrogen inlet 5. The pulse solenoid valve interface 51 is a structure or reserved space for installing or connecting a pulse solenoid valve. For example, the pulse solenoid valve interface 51 can be a standard threaded hole for directly installing a miniature pulse solenoid valve; or, the pulse solenoid valve interface 51 can be a cavity integrated into the inner wall of the liquid nitrogen inlet 5 to accommodate the core components of the solenoid valve and connect to the control system via an external cable. During liquid nitrogen cooling, the system output (such as cutting temperature and liquid nitrogen flow rate) is monitored in real time and compared with the set value. The liquid nitrogen input (such as the opening or frequency of the pulse solenoid valve) is adjusted based on the deviation to ensure the cooling effect of the T-slot milling cutter 2. For example, a temperature sensor or flow sensor can be placed near the cutting area to feed real-time data back to the controller, which then adjusts the duty cycle or frequency of the pulse solenoid valve according to a preset algorithm. Alternatively, a preset cutting parameter database can be used to automatically find the corresponding liquid nitrogen flow rate based on the current cutting conditions (such as feed rate, depth of cut, and material type) and adjust it via the pulse solenoid valve.

[0039] Thus, the design of the liquid nitrogen inlet 5 gradually decreasing in diameter towards the cutter head 22 pre-accelerates and stabilizes the liquid nitrogen fluid entering the tool, ensuring good flow before the liquid nitrogen enters the main channel 1 of the shank transition zone. This provides stable input conditions for the pressure distribution in the subsequent flow channels, effectively reducing turbulence and pressure loss at the inlet. Furthermore, the pulse solenoid valve interface 51 allows the tool to coordinate with an external control system to adjust the on / off frequency and flow rate of liquid nitrogen in real time based on cutting load or temperature feedback, achieving closed-loop flow regulation. This ensures that the liquid nitrogen supply precisely matches the cooling requirements of the actual cutting conditions during liquid nitrogen cooling, avoiding liquid nitrogen loss due to excessive flow or cooling failure due to insufficient flow. This improves cooling response speed and adaptability, maintaining efficient and economical cooling throughout the cutting process.

[0040] Optionally, combined Figure 7 As shown, the multi-stage diffusion composite outlet 4 includes a throttling buffer cavity 41 and a porous diffusion surface structure 42. The inner diameter of the throttling buffer cavity 41 is larger than the inner diameter of the variable cross-section lateral C-shaped branch channel 32, and the porous diffusion surface structure 42 is arranged on the edge 23.

[0041] Specifically, the throttling buffer cavity 41 connects the porous diffuser structure 42 and the variable cross-section lateral C-shaped branch channel 32. The inner diameter of the throttling buffer cavity 41 is designed to be larger than the inner diameter of the variable cross-section lateral C-shaped branch channel 32. This abrupt change in cross-sectional area creates an expansion region, causing the high-speed flowing liquid nitrogen to decelerate and recover pressure, thus playing a buffering role. The throttling buffer cavity 41 can be a simple enlarged cavity or a cavity with a specific internal geometry (e.g., a conical diffuser section, a stepped enlargement section) to optimize the dissipation of fluid kinetic energy and pressure stability. Its main function is to reduce the kinetic energy of liquid nitrogen flowing out of the branch channel 32, slow down flow velocity fluctuations, avoid the impact effect caused by excessively high flow velocity of liquid nitrogen, and provide a stable flow field environment for subsequent uniform injection.

[0042] The porous diffusion surface structure 42 can be implemented in various forms. For example, it can be formed into a regularly arranged array of micropores on a metal plate through laser micro-hole processing; or it can be made of porous materials such as sintered metal or ceramics to provide uniform penetration and diffusion effects. The porous diffusion surface structure 42 is arranged at the bottom of the chip evacuation groove of the T-slot milling cutter 2, at the edge 23 where it intersects with the side cutting edge. This position is the area where heat is most concentrated during cutting. At the same time, the axis of the porous diffusion surface structure 42 points towards the cutting area at a small angle of 5° to 15°, so that the vaporized nitrogen can be smoothly discharged along the straight groove chip evacuation groove, avoiding accumulation in the T-slot. In some embodiments, an auxiliary venturi groove with a diameter of 0.2 mm can also be added at the transition area between the bottom of the chip evacuation groove and the back cutting edge.

[0043] Thus, by making the inner diameter of the throttling buffer chamber 41 larger than the inner diameter of the variable cross-section lateral C-shaped branch channel 32, a pressure buffer zone is formed by the abrupt change in cross-sectional area. This causes the liquid nitrogen to transform from a single-phase liquid into a fine two-phase spray before flowing out, effectively reducing the kinetic energy of the liquid nitrogen as it flows out of the branch channel 32, slowing down flow velocity fluctuations, and avoiding the impact effect caused by excessively high flow velocity. This provides a stable flow field environment for subsequent uniform spraying. Furthermore, a porous diffusion surface structure 42 is arranged at the bottom of the chip removal groove of the T-slot end mill 2, at the edge 23 where it intersects with the side cutting edge. The porous diffusion surface structure 42 can refine and disperse the buffered liquid nitrogen, allowing the cooling medium to cover the edge 23 and surrounding area in a more uniform distribution. This not only enhances the cooling effect on the cutting edge but also avoids uneven local cooling caused by a single nozzle through porous diffusion, effectively mitigating thermal fatigue damage to the tool under high-temperature cutting, thereby significantly improving the cutting performance and tool life of the T-slot end mill 2 under liquid nitrogen cooling conditions.

[0044] Optionally, the number of variable cross-section lateral C-shaped branch channels 32 is the same as the number of side blades.

[0045] Specifically, the number of variable cross-section lateral C-shaped branch channels 32 connected to each annular collection cavity 31 is the same as the number of side cutting edges. For example, during tool manufacturing, advanced additive manufacturing technologies, such as selective laser melting (SLM) or electron beam melting (EBM), can be used to integrally form the variable cross-section lateral C-shaped branch channels 32, equal in number to the number of side cutting edges, inside the cutter head 22 of the T-type milling cutter 2, thereby ensuring the accuracy of the channel layout.

[0046] Thus, by ensuring that the number of variable-section lateral C-shaped branch channels 32 is the same as the number of side edges, when liquid nitrogen enters the same number of variable-section lateral C-shaped branch channels 32 as the side edges through the main channel 1 of the shank transition zone and the annular collection chamber 31, the liquid nitrogen can be evenly distributed to each branch channel and finally precisely sprayed onto the rear of the corresponding side edge's flank face through the multi-stage diffusion composite outlet 4. This effectively avoids localized cooling blind spots and overheating caused by insufficient or unevenly distributed cooling channels, thereby significantly improving the utilization efficiency of the liquid nitrogen cooling medium and reducing unnecessary waste. At the same time, because the thermal load of each side edge can be cooled evenly, the overall cutting stability of the tool is enhanced, effectively suppressing cutting edge wear and chipping, thereby extending the service life of the T-slot milling cutter 2 and ensuring machining accuracy under complex cutting conditions. In this way, while ensuring the cooling effect, it also avoids the adverse effects on the tool structure rigidity caused by opening too many or too few channels inside the cutter head 22.

[0047] Optionally, the liquid nitrogen internally cooled T-slot cutter also includes a PVD wear-resistant coating covering the side cutting edge and the rake face of the chip flute.

[0048] Specifically, PVD (Physical Vapor Deposition) wear-resistant coatings are a technology that deposits a thin film on the surface of a cutting tool using physical methods. The aim is to improve the tool's hardness, wear resistance, oxidation resistance, and reduce the coefficient of friction. Common PVD coating materials include TiN (titanium nitride), TiAlN (titanium aluminum nitride), and AlCrN (aluminum chromium nitride). For example, magnetron sputtering PVD technology can be used to deposit a TiAlN coating on the tool surface, forming a dense nanocrystalline structure to provide excellent wear resistance. In the T-slot milling cutter, the side cutting edge is the part that mainly bears the radial cutting force during the cutting process, directly contacting the workpiece material and enduring high pressure and friction. The rake face of the chip flute is the surface through which chips flow, and there is intense friction and adhesion between the chip and the rake face. These two areas are the parts of the tool that experience the most severe wear, the highest heat load, and are most prone to adhesion during the cutting process.

[0049] Thus, based on the effective reduction of the overall thermal load of the tool and maintenance of the tool substrate by the internal liquid nitrogen cooling system (including the main channel 1 of the shank transition zone, the radial multi-layer variable cross-section channel 3, and the multi-stage diffusion composite outlet 4), the T-slot milling cutter 2 is further protected by a PVD wear-resistant coating on its side cutting edge and chip groove rake face. The PVD wear-resistant coating acts as a physical barrier between the tool and the high-temperature chips, which can significantly reduce the coefficient of friction during the cutting process, reduce chip adhesion and wear on the tool surface, reduce the generation of cutting heat, and promote the smooth discharge of chips. This further reduces the thermomechanical load on the tool surface, thereby enhancing the tool's wear resistance and surface stability under complex cutting conditions in the low-temperature environment provided by liquid nitrogen cooling, effectively extending the service life of the T-slot milling cutter 2, and improving machining quality.

[0050] Optionally, combined Figure 1 and Figure 5 As shown, the liquid nitrogen internally cooled T-type end mill also includes a reinforcing rib 6 disposed inside the cutter head 22. One end of the reinforcing rib 6 is connected to the outer wall of the main channel 1 of the shank transition area, and the other end extends radially along the cutter head 22.

[0051] Specifically, the cross-sectional shape of the reinforcing rib 6 can be optimized based on mechanical analysis and spatial constraints, and can take various forms such as rectangle, triangle, T-shape, I-shape, or streamlined shape. Its thickness can be uniformly distributed or designed with varying thickness according to stress concentration areas to achieve optimal material utilization. In manufacturing, the reinforcing rib 6 can be integrally formed with the T-shaped end mill 2 body, for example, through additive manufacturing (such as selective laser melting, SLM) or precision casting; it can also be connected to the body through welding, sintering, or other methods. If integrally formed, its material is the same as the tool body, such as ultrafine-grained WC-Ni cemented carbide. If manufactured separately and then connected, materials compatible with the tool body and possessing high strength and rigidity can be selected, such as high-strength steel, ceramic composites, or carbon fiber reinforced composites, to ensure the overall structural mechanical properties.

[0052] Thus, by setting reinforcing ribs 6 inside the cutter head 22, with one end connected to the outer wall of the main channel 1 in the shank transition area and the other end extending radially along the cutter head 22, the reinforcing ribs 6 form a stable internal support skeleton, effectively mechanically connecting the central support structure of the tool (i.e., the main channel 1 in the shank transition area) with the peripheral head structure (cutter head 22). This allows the cutting force acting on the outer edge of the cutter head 22 during cutting to be transmitted more evenly to the wall of the main channel 1 in the center of the tool, thereby effectively dispersing the stress concentration of the cutter head 22 under high-speed rotation and cutting loads. Combined with the multiple axially spaced annular collection cavities 31 and variable cross-section lateral C-shaped branch channels 32 inside the cutter head 22, the presence of reinforcing ribs 6 ensures that the cutter head 22 can still maintain sufficient bending and torsional rigidity even with these internal openings, significantly improving the structural stability of the tool in complex machining environments, thereby extending the tool's service life and improving machining accuracy.

[0053] Optionally, the T-type end mill 2 is made of ultrafine grain WC-Ni cemented carbide, wherein the WC grain size is 0.2 to 0.4 μm and the Ni binder content is 10 to 12 wt%.

[0054] Thus, using ultrafine-grained WC-Ni cemented carbide as the matrix material for the T-slot end mill 2 provides a robust and highly resilient physical carrier for the internal liquid nitrogen cooling system. Precisely controlling the WC grain size to 0.2 to 0.4 μm significantly improves the tool's hardness and wear resistance, ensuring a sharp cutting edge during cutting and reducing increased cutting forces due to wear. Simultaneously, the refined grain structure enhances the material's fracture toughness at the microscale, effectively mitigating the potential decrease in head rigidity after internal flow channel machining and strengthening its impact resistance. Furthermore, the introduction of 10 to 12 wt% Ni as a binder, compared to traditional binders, demonstrates superior toughness retention under the cryogenic conditions of liquid nitrogen. This effectively resists the thermal shock generated by the alternating high temperatures in the cutting zone and the low temperatures of liquid nitrogen, preventing microcracks from forming in the tool under drastic temperature changes. This material ratio not only ensures the structural integrity of the tool under high-speed cutting, but also optimizes the thermal conductivity and mechanical properties of the base material to form a highly efficient synergistic effect with the internal liquid nitrogen cooling channels such as the main channel 1 in the shank transition area, the radial multi-layer variable cross-section channel 3, and the multi-stage diffusion composite outlet 4. This ensures that the T-slot milling cutter 2 can achieve efficient cooling under extreme working conditions while maintaining good impact resistance and structural stability, thereby significantly extending the overall service life of the tool and improving machining efficiency and stability.

[0055] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A liquid nitrogen internally cooled T-type end mill, characterized in that, include: The shank transition zone main channel (1) for introducing liquid nitrogen passes through the shank (21) of the T-shaped milling cutter (2) along the axial direction of the T-shaped milling cutter (2) and extends into the cutter head (22); The radial multi-layer variable cross-section channel (3) located in the cutter head (22) includes an annular collection cavity (31) and multiple variable cross-section lateral C-shaped branch channels (32). The annular collection cavity (31) surrounds the main channel (1) of the shank transition area along the circumference of the cutter head (22) and is connected to the main channel (1) of the shank transition area. The multiple variable cross-section lateral C-shaped branch channels (32) are distributed along the circumference of the annular collection cavity (31). One end of each variable cross-section lateral C-shaped branch channel (32) is connected to the annular collection cavity (31), and the other end extends radially along the cutter head (22) to the rear of the blade face. The inner diameter of each variable cross-section lateral C-shaped branch channel (32) first increases and then decreases along the liquid nitrogen flow direction. Multiple multi-stage diffusion composite outlets (4) are connected one-to-one with the variable cross-section lateral C-shaped branch channel (32). The multi-stage diffusion composite outlets (4) are arranged at the bottom of the chip removal groove of the T-type milling cutter (2) and the edge (23) where the side cutting edge meets the back face of the cutting edge.

2. The liquid nitrogen internally cooled T-type end mill according to claim 1, characterized in that, The inner diameter of the main channel (1) in the transition area of ​​the handle (21) gradually increases toward the cutting head (22).

3. The liquid nitrogen internally cooled T-type end mill according to claim 2, characterized in that, The main channel (1) of the handle transition area is provided with low thermal conductivity microtexture.

4. The liquid nitrogen internally cooled T-type end mill according to claim 1, characterized in that, At least two annular collection cavities (31) are provided, and the two annular collection cavities (31) are distributed at an axial interval along the main channel (1) of the handle transition area. Each annular collection cavity (31) is connected to multiple variable cross-section lateral C-shaped branch channels (32).

5. The liquid nitrogen internally cooled T-type end mill according to claim 1, characterized in that, It also includes a liquid nitrogen inlet (5) for liquid nitrogen access. The liquid nitrogen inlet (5) is located at one end of the main channel (1) of the shank transition area away from the cutter head (22). The inner diameter of the liquid nitrogen inlet (5) gradually decreases toward the cutter head (22) and communicates with the main channel (1) of the shank transition area. The inner wall of the liquid nitrogen inlet (5) is provided with a pulse solenoid valve interface (51) for closed-loop flow regulation.

6. The liquid nitrogen internally cooled T-type end mill according to claim 1, characterized in that, The multi-stage diffusion composite outlet (4) includes a throttling buffer cavity (41) and a porous diffusion surface structure (42). The inner diameter of the throttling buffer cavity (41) is larger than the inner diameter of the variable cross-section lateral C-shaped branch channel (32). The porous diffusion surface structure (42) is arranged on the edge (23).

7. The liquid nitrogen internally cooled T-type end mill according to claim 1, characterized in that, The number of the variable cross-section lateral C-shaped branch channels (32) is the same as the number of the side blades.

8. The liquid nitrogen internally cooled T-type end mill according to claim 1, characterized in that, It also includes a PVD wear-resistant coating covering the side cutting edge and the rake face of the chip removal groove.

9. The liquid nitrogen internally cooled T-type end mill according to claim 4, characterized in that, It also includes a reinforcing rib (6) disposed inside the cutter head (22), one end of which is connected to the outer wall of the main channel (1) of the shank transition area, and the other end extends radially along the cutter head (22).

10. The liquid nitrogen internally cooled T-type end mill according to claim 1, characterized in that, The T-shaped end mill (2) is made of ultrafine grain WC-Ni cemented carbide, wherein the WC grain size is 0.2 to 0.4 μm and the Ni binder content is 10 to 12 wt%.

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