A special tool for composite material helical milling

Abstract

The application discloses a special tool for composite material spiral hole milling, and relates to the technical field of special tools for spiral hole milling, which comprises a cutting part, a neck part and a tool bar which are sequentially connected, the cutting part comprises an end edge milling area and a side edge finishing area, the radius of the end edge milling area is smaller than that of the side edge finishing area, the end edge milling area is provided with a plurality of same teeth which are uniformly distributed in the circumferential direction, the front end of each tooth is provided with a groove, the side edge finishing area is provided with a plurality of side edges which are connected with the rear end of each tooth, the neck part is provided with a chip pocket which is smoothly connected with each side edge, and the neck part is connected with the tool bar. By changing the structure of the end edge and the side edge, the application optimizes the process of traditional spiral hole milling, further reduces the axial force generated during hole making, and improves the hole making quality.

Description

Technical Field

[0001] This invention relates to the field of special tools for spiral milling, and in particular to a special tool for spiral milling of composite materials. Background Technology

[0002] Carbon fiber reinforced polymer (CFRP) composites possess advantages such as low density, high specific strength, high specific modulus, high temperature resistance, corrosion resistance, wear resistance, and low cost, leading to their widespread application in the aerospace industry. However, CFRPs are typical difficult-to-machine materials for aerospace applications, exhibiting extremely poor machinability. Traditional drilling techniques are prone to producing technical problems such as delamination and burrs, resulting in poor machining quality.

[0003] In helical milling using traditional end mills, the tool rotates at high speed while feeding along a helical trajectory, machining a circular hole with a diameter larger than the tool itself in the material. Compared to traditional drilling, this method offers the following advantages: 1) Higher machining quality, reduced delamination at the composite material exit, and improved dimensional accuracy. 2) Shorter process flow and higher machining efficiency compared to the traditional drilling-reaming-reaming method. 3) By changing the eccentricity during helical milling, a single tool can machine multiple hole diameters, reducing tooling costs. 4) The smaller tool diameter compared to the hole facilitates chip removal during helical milling.

[0004] The core of spiral milling technology is the spiral milling tool. Due to the different hole-making methods, spiral milling tools are very different from traditional tools.

[0005] For example, patent document CN112453532A discloses a special composite tool for spiral milling of carbon fiber composite materials and its processing method. This tool, belonging to the category of spiral milling tools, solves the problems of severe workpiece material damage and accelerated tool wear when machining carbon fiber composite materials with existing spiral milling tools. The cutting section includes a front milling area, a transition reaming area, and a rear cutting area connected in sequence. The diameter of the front milling area is smaller than that of the rear cutting area, and a smooth transition reaming area is used between the front milling area and the rear cutting area. The front milling area is an end mill structure, equipped with multiple bottom cutting edges that feed along the tool axis. The outer surfaces of the transition reaming area and the rear cutting area are respectively equipped with transition cutting edges and side cutting edges of the same number and smoothly connected in sequence as the bottom cutting edges. First, a hole is machined by the bottom cutting edges. Then, as the tool feeds axially, the transition cutting edges continuously enlarge the diameter of the hole, and finally, the side cutting edges machine the hole to the final diameter. However, this tool is limited in that the lead of the helical milling path is less than 50% of the length of the transition reaming zone, and the part of the end edge that does not participate in the cutting will also cause extrusion on the carbon fiber composite material, generating axial force, and hole-making damage still exists.

[0006] For example, patent document CN111408777A discloses a stepped bidirectional end mill for spiral milling of carbon fiber composite materials and its grinding method, relating to the field of cutting tool technology. The specific solution is as follows: A stepped bidirectional end mill for spiral milling of carbon fiber composite materials includes a cutter head and a shank. The top of the cutter head is provided with two pairs of centrally symmetrically distributed two-segment zigzag cutting edges I. Four spiral grooves with the same helical direction are evenly distributed along the axial direction on the outer circumference of the cutter head. The spiral plate between each adjacent spiral groove is divided from top to bottom into a forward cutting zone, a transition zone, and a reverse cutting zone. The forward cutting zone is provided with a cutting edge II. The transition zone is a concave arc shape. The reverse cutting zone is a convex arc shape and is provided with a cutting edge III. The reverse cutting zone is connected to the shank. However, this tool has two cutting processes: forward cutting and reverse cutting. Furthermore, the eccentricity needs to be adjusted again before reverse machining, resulting in low machining efficiency.

[0007] For example, patent document CN113441774A discloses a ball end mill, including a shank and a cutting head machining section located at one end of the shank. The cutting head machining section has a ball-shaped tip and includes an end main cutting edge and side cutting edges. An end chip evacuation groove is provided between the end main cutting edges, and a side chip evacuation groove is provided between adjacent side cutting edges. There are two end main cutting edges, and a smooth arc-shaped chisel edge is provided between the two end main cutting edges, so that the two end main cutting edges transition smoothly through the arc-shaped chisel edge. This tool does not improve the ball end mill from the perspective of composite material machining quality and does not solve the problem of low side edge utilization. Summary of the Invention

[0008] The purpose of this invention is to provide a special tool for spiral milling of composite materials, which solves the problems of low side edge utilization, poor hole quality and inability to guarantee accuracy when machining composite materials.

[0009] To achieve the above objectives, the present invention provides the following solution:

[0010] This invention provides a special tool for spiral milling of composite materials, comprising a cutting section, a neck, and a tool holder connected in sequence. The cutting section includes an end-cutting milling area and a side-cutting finishing area. The radius of the end-cutting milling area is smaller than the radius of the side-cutting finishing area. The end-cutting milling area has a plurality of identical cutting teeth evenly distributed circumferentially, and the front end of each cutting tooth forms a groove. The side-cutting finishing area has a plurality of side edges connected to the rear end of each cutting tooth. The neck is provided with a chip-receiving groove that is smoothly connected to each side edge. The neck is connected to the tool holder.

[0011] Preferably, each of the cutting teeth includes an inner cutting edge, a middle cutting edge, and an outer cutting edge connected in sequence. The inner cutting edge and the middle cutting edge intersect at the cutting edge inflection point, the middle cutting edge and the outer cutting edge intersect at the middle cutting tip point, and the outer cutting edge and the side cutting edge intersect at the outer cutting tip point. The front end of each inner cutting edge forms a conical groove.

[0012] Preferably, the inner cutting edge is a straight edge, the middle cutting edge is a curved edge, and the outer cutting edge is a straight edge.

[0013] Preferably, the front ends of each of the internal cutting edges intersect the axis of the composite material spiral milling tool.

[0014] Preferably, the inner cutting edge, the middle cutting edge, and the outer cutting edge are all double flank faces. The first flank face of the inner cutting edge is a curved surface, the first flank face of the middle cutting edge is a curved surface, the first flank face of the outer cutting edge is a plane, and the second flank faces of the inner cutting edge, the second flank faces of the middle cutting edge, and the second flank faces of the outer cutting edge form the same curved surface.

[0015] Preferably, the radial projection of the side-edge finishing area is arc-shaped and tangent to the axial direction of the composite material spiral milling tool.

[0016] Preferably, the parameters of each side cutting edge near the end cutting edge milling area are consistent with the parameters of each side cutting edge near the neck.

[0017] Preferably, a spiral groove is provided between adjacent side blades, and the spiral groove is in communication with the chip-receiving groove.

[0018] Preferably, the radius of the neck is smaller than the radius of the side-edge finishing area.

[0019] Preferably, the radius of the neck is smaller than the radius of the tool holder.

[0020] The present invention achieves the following technical effects compared to the prior art:

[0021] This invention relates to a special spiral milling tool for composite materials. First, it mills carbon fiber composite materials using an end-edge milling zone composed of straight and curved cutting edges. This structure results in smaller, more easily removed chips. Then, as the tool feeds axially, a side-edge finishing zone continuously removes material from the hole wall until the final hole diameter is reached. This side-edge finishing zone is also composed of curved cutting edges, which improves side-edge utilization. The curved side edges gradually enlarge the hole wall as the tool feeds. This invention further reduces the axial force generated by the end-edge, minimizing delamination and tearing damage in the composite material and improving hole quality. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the composite material spiral milling tool of the present invention;

[0024] Figure 2 This is a top view of the end-cutting milling area of ​​the present invention;

[0025] Figure 3 for Figure 2 AA section view;

[0026] Figure 4 This is a front view of the cutting part of the present invention;

[0027] Figure 5 This is a three-dimensional schematic diagram of the cutting part of the present invention;

[0028] Figure 6 This diagram illustrates the machining process using the composite material spiral milling tool of the present invention. Figure 1 ;

[0029] Figure 7 This diagram illustrates the machining process using the composite material spiral milling tool of the present invention. Figure 2 ;

[0030] Figure 8 This diagram illustrates the machining process using the composite material spiral milling tool of the present invention. Figure 3 ;

[0031] Figure 9 This diagram illustrates the machining process using the composite material spiral milling tool of the present invention. Figure 4 ;

[0032] Figure 10 This diagram illustrates the machining process using the composite material spiral milling tool of the present invention. Figure 5 ;

[0033] Among them: 100. Special tool for spiral milling of composite materials, 1. End milling zone, 2. Side finishing zone, 3. Chip removal groove, 4. Neck, 5. Tool holder, 6. Tapered groove, 7. Inner cutting edge, 8. Middle cutting edge, 9. Outer cutting edge, 10. First flank face of side cutting edge, 11. Axis, 12. Side cutting edge, 13. First turning point of cutting edge, 14. Second turning point of cutting edge, 15. Outer tool tip, 16. Bottom end point of side cutting edge, 17. First flank face of inner cutting edge, 18. First flank face of middle cutting edge, 19. First flank face of outer cutting edge, 20. Second flank face, 21. Second flank face of side cutting edge, 22. Midpoint of tool in end milling zone, 23. Workpiece, 24. End and side cutting edge junction point, 25. Midpoint of side cutting zone, 26. Full entry point of side cutting edge, 27. Tool finishing point. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] The purpose of this invention is to provide a special tool for spiral milling of composite materials, which solves the problems of low side edge utilization, poor hole quality and inability to guarantee accuracy when machining composite materials.

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] like Figures 1 to 5As shown: This embodiment provides a special tool 100 for spiral milling of composite materials, including a cutting section, a neck 4, and a tool holder 5 connected in sequence. The length of the cutting section is 10mm, the length of the neck 4 is 15mm, and the length of the tool holder 5 is 40mm. The cutting section includes an end-cutting milling area 1 and a side-cutting finishing area 2. The length of the end-cutting milling area 1 is 2mm, and the length of the side-cutting finishing area 2 is 8mm. The radius of the end-cutting milling area 1 is smaller than the radius of the side-cutting finishing area 2, which can improve the utilization rate of the side cutting edge 12. The hole wall is machined using the side cutting edge 12 of the side-cutting finishing area 2, thereby improving the hole quality. The radius of the neck 4 is smaller than the radius of the side-edge finishing area 2, and the radius of the neck 4 is smaller than the radius of the tool holder 5, which facilitates the holding of the tool holder 5. The end-edge milling area 1 has four identical cutting teeth evenly distributed circumferentially, and the front end of each cutting tooth forms a groove, preferably a conical groove 6, so that the center of the tool does not participate in cutting, reducing the axial force generated in the central area. The side-edge finishing area 2 has four side edges 12 connected to the rear end of each cutting tooth. The neck 4 is provided with four spiral chip removal grooves 3 smoothly connected to each side edge 12, which facilitates the removal of chips generated in the side-edge finishing area 2. The rear end of the neck 4 is connected to the tool holder 5. This embodiment optimizes the traditional spiral milling process by changing the structure of the end edge and side edges 12, further reducing the axial force generated during hole making, thereby improving the hole making quality.

[0038] Specifically, in this embodiment, each cutting tooth includes an inner cutting edge 7, a middle cutting edge 8, and an outer cutting edge 9 connected in sequence. The inner cutting edge 7 and the middle cutting edge 8 intersect at the cutting edge inflection point (first cutting edge inflection point 13), the middle cutting edge 8 and the outer cutting edge 9 intersect at the middle tool tip point (second cutting edge inflection point 14), and the outer cutting edge 9 and the side cutting edge 12 intersect at the outer tool tip point 15. The outer cutting edge 9 is smoothly connected to the first flank face 10 of the side cutting edge. The first flank face 10 and the second flank face 21 of the side cutting edge constitute a double flank face structure of the side cutting edge, which can increase the cutting edge strength, reduce wear between the cutting edge and the workpiece, and reduce the probability of chipping. In the end milling area 1, the radius of the middle cutting edge 8 is 5mm, the maximum radius of the end milling area 1 is 4mm and is equal to the minimum radius of the side finishing area 2, and the maximum radius of the side finishing area 2 is 5mm.

[0039] In this embodiment, the inner cutting edge 7 is a straight edge, the middle cutting edge 8 is a curved edge, and the outer cutting edge 9 is a straight edge, which can reduce the chip size and make the chips easier to remove. The inner cutting edge 7, the middle cutting edge 8, and the outer cutting edge 9 are all double flank faces. The first flank face 17 of the inner cutting edge is a curved surface, the first flank face 18 of the middle cutting edge is a curved surface, and the first flank face 19 of the outer cutting edge is a plane. The second flank face of the inner cutting edge, the second flank face of the middle cutting edge, and the second flank face of the outer cutting edge are a single curved surface, namely the second flank face 20.

[0040] In this embodiment, the front ends of each inner cutting edge 7 intersect the axis 11 of the composite material spiral milling tool 100, and the angle between the front end of each inner cutting edge 7 and the axis 11 of the composite material spiral milling tool 100 is 65°. The apex angle of the conical groove 6 formed by the four inner cutting edges 7 is 130°. The radius of the middle cutting edge 8 is the same as the radius of the composite material spiral milling tool 100. The angle between the outer cutting edge 9 and the tangent direction of the middle cutting edge 8 is 12°. The distance from the outer tip of the tool to the axis 11 of the composite material spiral milling tool 100 should be less than the distance from the bottom end of the side cutting edge 12 to the axis 11 of the composite material spiral milling tool 100.

[0041] In this embodiment, the radial projection of the side-edge finishing zone 2 (referring to the projection on the plane where the axis 11 of the composite material spiral milling tool 100 is located) is arc-shaped, i.e. Figure 3 The arc portion between the outermost tip 15 and the bottom endpoint 16 of the side cutting edge is tangent to the axis 11 of the composite material spiral milling tool 100, with the tangent point being the bottom endpoint of the side cutting edge 12. Figure 3 The bottom end point of the middle side blade is 16.

[0042] In this embodiment, each side blade 12 is a curved blade, and a spiral groove is provided between adjacent side blades 12. The spiral groove is connected to the chip removal groove 3. The parameters of each side blade 12 near the end milling area 1 (front angle, first clearance angle, second clearance angle, chip removal groove radius) are consistent with the parameters of each side blade 12 near the neck 4, so that the spiral groove between adjacent side blades 12 in the side blade finishing area 2 is smooth and easy to remove chips.

[0043] like Figures 4 to 5 As shown, the inner cutting edge 7 has a straight edge, the middle cutting edge 8 has a curved edge, and the outer cutting edge 9 has a straight edge, with multiple edge types combined. The distance between the first turning point 13 of the cutting edge and the axis 11 of the composite material spiral milling tool 100 is 1.0 mm, the distance between the second turning point 14 of the cutting edge and the axis 11 of the composite material spiral milling tool 100 is 2.5 mm, and the distance between the outer tip 15 and the axis 11 of the composite material spiral milling tool 100 is 4.0 mm.

[0044] like Figure 6 As shown, the end-cutting milling area 1 is approximated as an arc-shaped structure. The eccentricity e is the distance between the straight line containing the midpoint 22 of the tool in the end-cutting milling area and the axis 11. The end-cutting milling area 1 first contacts the workpiece 23 to perform initial hole machining, with a machining shape of arc. As the tool feeds axially, the end-cutting milling part completely enters the workpiece 23, that is, the end-cutting and side-cutting intersection point 24 contacts the workpiece 23, as shown. Figure 7 As shown. Simultaneously, the side cutting edge 12 of the side cutting edge finishing zone 2 begins to contact the workpiece 23, performing the finishing steps, as follows: Figure 8As shown, the midpoint 25 of the side cutting area contacts the workpiece 23.

[0045] like Figure 9 As shown, the side cutting edge 12 fully contacts the workpiece 23, and the final hole is machined starting from the bottom of the side cutting edge 12. The bottom endpoint 16 of the side cutting edge coincides with the complete entry point 26 of the side cutting edge, removing the hole wall material. As the tool feeds axially, the hole wall material is gradually removed by the side cutting edge 12, effectively preventing the formation of burrs. As the side cutting edge finishing zone 2 removes the delamination caused by the axial force in the hole exit area, the hole-making process ends, and the bottom endpoint 16 of the side cutting edge coincides with the tool's machining completion point 27, as shown. Figure 10 As shown.

[0046] This embodiment modifies the structure of the tool's end cutting edge and side cutting edge 12, introducing a curved cutting edge. This allows the side cutting edge 12 to leverage its finishing advantages during milling, improving hole quality. The tapered groove 6 effectively reduces the compression of the composite material in the tool's central area, lowering the axial force generated during helical milling, thereby reducing delamination and burr formation. The inner cutting edge 7, middle cutting edge 8, and outer cutting edge 9 all employ a double flank face design, effectively increasing the strength of the cutting portion, expanding the heat dissipation area, and suppressing vibrations generated during cutting.

[0047] This specification uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A composite material helical hole-milling dedicated tool, characterized by: The composite material spiral hole milling special tool comprises a cutting part, a neck part and a tool bar which are sequentially connected, the cutting part comprises an end blade milling area and a side blade finishing area, the radius of the end blade milling area is smaller than the radius of the side blade finishing area, the end blade milling area is provided with a plurality of same teeth which are uniformly distributed in a circumferential direction, the front end of each tooth forms a groove, the side blade finishing area is provided with a plurality of side blades which are connected with the rear end of each tooth, the neck part is provided with a chip pocket which is smoothly connected with each side blade, and the neck part is connected with the tool bar. Each tooth comprises an inner cutting edge, a middle cutting edge and an outer cutting edge which are sequentially connected, the inner cutting edge and the middle cutting edge intersect at a cutting edge turning point, the middle cutting edge and the outer cutting edge intersect at a middle tooth tip point, the outer cutting edge and the side blade intersect at an outer side tooth tip point, and the front end of each inner cutting edge forms a conical groove.

2. The composite material helical milling dedicated tool according to claim 1, characterized in that: The inner cutting edge is a straight line, the middle cutting edge is a curved line, and the outer cutting edge is a straight line.

3. The composite material helical milling dedicated tool according to claim 1, characterized in that: The front end of each inner cutting edge intersects with the axis of the composite material spiral hole milling special tool.

4. The composite material helical milling dedicated tool according to claim 1, characterized in that: The inner cutting edge, the middle cutting edge and the outer cutting edge are all double clearance faces, the first clearance face of the inner cutting edge is a curved surface, the first clearance face of the middle cutting edge is a curved surface, the first clearance face of the outer cutting edge is a plane, the second clearance face of the inner cutting edge, the second clearance face of the middle cutting edge and the second clearance face of the outer cutting edge form a same curved surface.

5. The composite material helical milling dedicated tool according to claim 1, characterized in that: The radial projection of the side blade finishing area is in an arc shape and is tangent to the direction of the axis of the composite material spiral hole milling special tool.

6. The composite material helical milling dedicated tool according to claim 1, characterized in that: The parameters of each side blade close to the end blade milling area are consistent with the parameters of each side blade close to the neck part.

7. The composite material helical milling dedicated tool according to claim 1, characterized in that: A spiral groove is arranged between adjacent side blades, and the spiral groove is communicated with the chip pocket.

8. The composite material helical milling dedicated tool according to claim 1, characterized in that: The radius of the neck part is smaller than the radius of the side blade finishing area.

9. The composite material helical milling dedicated tool according to claim 1, characterized in that: The radius of the neck part is smaller than the radius of the tool bar.

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