A twist drill with milling cutting edge

Abstract

The application discloses a twist drill with milling edges, which comprises a shank and a cutting part. The cutting part is provided with a plurality of long helical chip removal grooves extending to the shank along the central axis direction of the twist drill and a guide edge band. The front end of the long helical chip removal groove is provided with a main cutting edge and a transverse edge. The side of the long helical chip removal groove is provided with a taper milling area. The taper milling area comprises a plurality of blade petals. The blade petals are provided with a taper helical long edge, a taper helical short edge and a short helical chip removal groove. The short helical chip removal groove has the same rotation direction as the long helical chip removal groove. The taper helical long edge comprises N groups of micro milling edges connected in series along the helical direction of the taper helical long edge. The taper helical short edge comprises N groups of micro milling edges connected in series along the helical direction of the taper helical short edge. N is greater than or equal to 2. The micro milling edges are provided with a chip separation groove opposite to the rotation direction of the long helical chip removal groove. The application has the advantages of being applicable to composite material drilling, high drilling efficiency, high machining precision, good quality and the like.

Description

Technical Field

[0001] This invention relates primarily to the field of composite material cutting and machining, and more particularly to a twist drill with milling edges. Background Technology

[0002] Composite materials typically possess excellent specific strength and specific modulus, along with superior fatigue resistance, corrosion resistance, vibration damping, and thermal stability, making them promising candidates for applications in high-tech fields such as aerospace. Fiber-reinforced polymer (FRP) composites, in particular, are widely used in military aircraft, unmanned combat aerial vehicles, missiles, rockets, and satellites. However, due to the unique manufacturing process of FRP, its mechanical properties exhibit anisotropy, and its interlaminar strength is low. Currently, most FRP hole-making processes still employ drilling, reaming, boring, and countersinking techniques, which easily lead to delamination, burrs, and tearing at the hole entrance and exit sides. These defects reduce the strength of the workpiece and, in severe cases, can render it unusable. These processing defects significantly hinder the promotion and application of FRP.

[0003] Studies have shown that when machining FRP with conventional drill bits used for machining regular metals, phenomena such as material delamination, hole tearing, and fiber pull-out from the hole wall surface are easily generated, making conventional drill bits unsuitable for machining this type of material. Furthermore, with increasing demands for processing efficiency across industries, high-feed machining is also being applied to FRP hole drilling, which makes hole defects even more likely to occur.

[0004] Chinese patent document CN210254406U discloses a three-pointed fine-toothed drilling and milling composite tool. The milling part is located between the drill tip and the tool holder and includes 4 to 6 helical cutting edges. The helical cutting edges are divided into several fine teeth by chip breaking grooves with the same direction of rotation and larger helix angle. In the processing of carbon fiber composite materials, the method of drilling first and then milling is adopted. The fine teeth of the milling part are used to greatly reduce the cutting amount and cutting force and remove the defects generated by drilling. However, although the three-pointed drill bit has the advantages of fast hole making speed and less likely to produce burrs or cracks, it is only suitable for large openings due to the limitation of the head shape. Moreover, it is easy to generate large friction and heat during the drilling process.

[0005] Chinese patent document CN107030319B discloses a milling-drilling composite tool with a drill tip and a tapered milling edge, and a spiral groove on the back of the tapered milling edge. The tapered milling edge can significantly reduce the chip thickness during machining, change the drilling force distribution, and suppress hole exit defects. At the same time, multiple milling edges can reduce the feed per tooth, making it suitable for high-feed machining. However, in high-feed machining, when there are many grooves on the back of the milling edge, the milling edge will inevitably become thinner and more prone to chipping. In addition, the increase in the number of milling edges will also increase the friction, which is not conducive to reducing axial force and instead increases the defects of the machined hole. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a twist drill with milling edges that can be used for drilling composite materials, can reduce axial cutting force and avoid defects such as delamination, splitting and burrs at the exit of the machined hole.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A twist drill with milling edges includes a shank and a cutting section. The cutting section has multiple long helical chip removal grooves and guide cutting edges extending towards the shank along the central axis of the twist drill. The front end of each long helical chip removal groove has a main cutting edge and a chisel edge. The side of each long helical chip removal groove has a tapered milling area, which includes multiple cutting edges. Each cutting edge has a tapered helical long cutting edge, a tapered helical short cutting edge, and a short helical chip removal groove. The short helical chip removal groove has the same helical direction as the long helical chip removal groove. Each tapered helical long cutting edge includes M sets of micro-milling edges connected in series along the helical direction of the tapered helical long cutting edge. Each tapered helical short cutting edge includes N sets of micro-milling edges connected in series along the helical direction of the tapered helical short cutting edge, satisfying: M≥2, N≥2. Each micro-milling edge has chip-breaking grooves with the opposite helical direction to the long helical chip removal grooves.

[0009] As a further improvement to the above technical solution:

[0010] The blade is provided with a tapered helical long blade and multiple tapered helical short blades. The tapered helical long blade is located between the long helical chip removal groove and the first short helical chip removal groove, and is connected to the guide blade. The tapered helical short blade is located between two adjacent short helical chip removal grooves or between the last short helical chip removal groove and the next long helical chip removal groove.

[0011] The taper angle of the tapered milling area is α, and satisfies: 6°≤α≤35°.

[0012] The axial length of the tapered milling area is L, the small end diameter is d1, and the large end diameter, i.e. the cutting diameter of the twist drill, is d2, and satisfies: L=0.5(d2-d1) / tanα, 0.5d2≤d1≤0.8d2.

[0013] The tapered helical long cutting edge is connected to the main cutting edge and the guide cutting edge at both ends. The axial length of the tapered helical long cutting edge is L1, and the axial length of the tapered helical short cutting edge is L2, and the following conditions are met: L1>L2, L1=L.

[0014] The micro-milling edge is formed by the interference of the chip-breaking groove and the tapered portion of the cutting edge, and the micro-milling edge is evenly distributed along the helical direction on the tapered helical long edge and the tapered helical short edge.

[0015] The long spiral chip removal groove and the short spiral chip removal groove are clockwise, and the chip separation groove is counterclockwise.

[0016] The length of the micro-milling cutting edge along the tangential direction of the short helical chip removal groove is L3, the width along the normal direction of the short helical chip removal groove is L4, and it has a planar back angle γ along the radial direction of the twist drill, satisfying: L3=0.1d2~0.14d2, L4=0.04d2~0.07d2, 3°≤γ≤12°.

[0017] The radial depth of the chip-dispersing groove is half the radial depth of the short spiral chip-discharging groove, and the spiral angle of the chip-dispersing groove is β, satisfying: 15°≤β<90°.

[0018] Compared with the prior art, the advantages of the present invention are as follows:

[0019] The present invention relates to a twist drill with milling edges, wherein the side of the long helical chip removal groove is provided with a tapered milling area. The tapered milling area includes multiple cutting edges, each with a tapered helical long cutting edge, a tapered helical short cutting edge, and a short helical chip removal groove. The short helical chip removal groove has the same helical direction as the long helical chip removal groove. The tapered helical long cutting edge includes M groups of micro-milling edges connected in series along the helical direction of the tapered helical long cutting edge, and the tapered helical short cutting edge includes N groups of micro-milling edges connected in series along the helical direction of the tapered helical short cutting edge, satisfying: M≥2, N≥2. The micro-milling edges are provided with chip-breaking grooves with the opposite helical direction to the long helical chip removal groove. That is, the multiple cutting edges of the cutting part are located in the tapered milling area, have a taper angle, and the tapered helical long cutting edge and the tapered helical short cutting edge on the cutting edge are all formed by several micro-milling edges connected in series along the helical direction. This structure, on the one hand, because the milling area has a taper angle much smaller than the drill tip angle, can significantly reduce the chip thickness and effectively reduce the axial component of the drilling force, thereby suppressing delamination, splitting, and burrs at the hole exit. The occurrence of burrs; on the other hand, because the milling area has multiple micro-milling edges arranged in a tapered spiral, multiple micro-milling edges can effectively reduce the feed per tooth and reduce the cutting load of a single tooth, so it can be applied to working conditions with large feed rates, improving cutting efficiency. The interlaced micro-milling edges can be regarded as an orderly arrangement of abrasive grains, integrating drilling and grinding, and can achieve a grinding effect, improving the surface quality of the machined hole. The micro-milling edges are provided with chip-separating grooves with the opposite direction of the long spiral chip removal groove, thus forming micro-milling edges, which can also improve chip removal performance and cooling effect. At the same time, the sharp micro-milling edges cut the machined surface multiple times during drilling, which can further reduce hole delamination, splitting and burr formation, improve the quality of the machined hole, and the cutting force is large during the processing of composite materials, and the cutting heat is not easy to transfer, which can easily cause the machined material to burn or soften and the tool to wear severely. The interlaced mesh grooves facilitate the flow of cutting fluid, facilitate heat dissipation during processing, and reduce damage to tools and workpieces. Attached Figure Description

[0020] Figure 1This is a schematic diagram of the structure of the first embodiment of the twist drill with milling edge of the present invention.

[0021] Figure 2 yes Figure 1 A-direction view.

[0022] Figure 3 This is a schematic diagram of the cutting part of the first embodiment of the twist drill with milling edge of the present invention.

[0023] Figure 4 This is a schematic diagram of the micro-milling edge of the first embodiment of the twist drill with milling edge of the present invention.

[0024] Figure 5 This is a radial cross-sectional view of the micro-milling edge of the first embodiment of the twist drill with milling edge of the present invention.

[0025] Figure 6 This is a schematic diagram of the second embodiment of the twist drill with milling cutting edge of the present invention.

[0026] Figure 7 yes Figure 6 View B.

[0027] Figure 8 This is a schematic diagram of the third embodiment of the twist drill with milling cutting edge of the present invention.

[0028] Figure 9 yes Figure 8 The C-direction view.

[0029] The labels in the diagram represent:

[0030] 1. Tool holder; 2. Cutting section; 3. Long spiral chip flute; 4. Guide cutting edge; 5. Main cutting edge; 6. Chisel edge; 7. Cutting edge; 71. Tapered spiral long cutting edge; 72. Tapered spiral short cutting edge; 73. Short spiral chip flute; 8. Micro-milling edge; 81. Chip divider; 9. Tapered milling area; 10. Central axis. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "horizontal", "inner", "outer", "top", "bottom", etc., which indicate orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and are not intended to 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 a limitation of this invention.

[0033] Figures 1 to 5This invention illustrates a first embodiment of a twist drill with milling edges. The twist drill includes a shank 1 and a cutting section 2. The cutting section 2 has two long spiral chip-removing grooves 3 extending towards the shank 1 along the central axis 10 of the twist drill, and two guide blades 4. The guide blades 4 are cylindrical. The front end of the long spiral chip-removing grooves 3 has two main cutting edges 5 and one chisel edge 6. The long spiral chip-removing grooves 3 are mainly used to accommodate chips formed during cutting by the main cutting edges 5 and the chisel edge 6, and to provide a channel for chip removal. The guide blades 4 serve a guiding function, and also... The drill bit can compress the inner wall of the hole to improve the surface quality and dimensional accuracy. To ensure the stability of the drilling process, the long spiral chip flute 3 and the guide blade 4 are usually designed to be symmetrical about the drill bit axis. The main cutting edge 5 and the chisel edge 6 are used to drill a round hole slightly smaller than the finished hole size, thereby reducing the cutting depth of the milling edge. At the same time, the chisel edge 6 has a centering function to ensure the positional accuracy of the machined hole. The side of the long spiral chip flute 3 is provided with a tapered milling area 9, which includes two cutting edges 7. One cutting edge 7 is provided with a tapered spiral long cutting edge 71 and two tapered spiral short cutting edges 72 (i.e., Figure 1 72a and 72b) and two short spiral chip removal grooves 73 (i.e. Figure 1In sections 73a and 73b), the short spiral chip removal groove 73 and the long spiral chip removal groove 3 have the same spiral direction. The tapered spiral long cutting edge 71 includes M groups of micro-milling cutting edges 8 connected in series along the spiral direction of the tapered spiral long cutting edge 71. The tapered spiral short cutting edge 72 includes N groups of micro-milling cutting edges 8 connected in series along the spiral direction of the tapered spiral short cutting edge 72, and satisfies: M≥2, N≥2. In this embodiment, M and N are both equal to 6. The micro-milling cutting edge 8 is provided with chip-separating grooves 81 with the opposite spiral direction to the long spiral chip removal groove 3. That is, the two cutting edges 7 of the cutting part 2 have a taper angle in the tapered milling area, and the tapered helical long edge 71 and tapered helical short edge 72 on the cutting edge 7 are all formed by several micro-milling edges 8 connected in the helical direction. This structure, on the one hand, because the milling area has a taper angle much smaller than the drill tip angle, can significantly reduce the chip thickness and effectively reduce the axial component of the drilling force, thereby suppressing the occurrence of delamination, splitting and burr phenomena at the hole exit; on the other hand, because the milling area has multiple micro-milling edges arranged in a tapered helical pattern... The milling blades 8, with multiple micro-milling blades 8, can effectively reduce the feed per tooth and lower the cutting load on a single tooth. Therefore, they can be applied to working conditions with large feed rates, improving cutting efficiency. The staggered micro-milling blades 8 can be regarded as an orderly arrangement of abrasive grains, integrating drilling and grinding, achieving a grinding effect and improving the surface quality of the machined hole. The micro-milling blades 8 are provided with chip-splitting grooves 81 with the opposite rotation direction to the long spiral chip removal grooves 3, thus forming the micro-milling blades 8. At the same time, it can improve chip removal performance and cooling effect. Meanwhile, the sharp micro-milling blades 8 perform multiple cuts on the machined surface during drilling, which can further reduce hole delamination, splitting, and burr formation, improving the quality of the machined hole. Moreover, since the cutting force of composite materials is large during processing, the cutting heat is not easy to dissipate, which can easily cause the machined material to burn or soften and the tool to wear severely. In this embodiment, the staggered and interconnected mesh grooves formed by the chip-splitting grooves 81 and the long spiral chip removal grooves 3 facilitate the inflow of cutting fluid, facilitate heat dissipation during processing, and reduce damage to the tool and workpiece.

[0034] In this embodiment, the taper angle of the taper milling region 9 is α (e.g., ...). Figure 3 As shown, in order to avoid making the taper milling area 9 too long, which would limit the application range of the twist drill, and to avoid thickening the chips and increasing the cutting force, which would be detrimental to reducing the axial cutting force, the following conditions should be met: 6°≤α≤35°. In this embodiment, α=10°.

[0035] In this embodiment, the axial length of the taper milling region 9 is L, the small end diameter is d1, and the large end diameter, i.e., the cutting diameter of the twist drill, is d2. After the taper angle α of the taper milling region 9 is determined, in order to ensure that the axial length of the milling region does not affect the axial cutting force of the drill bit, the following should be satisfied: L=0.5(d2-d1) / tanα, 0.5d2≤d1≤0.8d2. In this embodiment, d2=6mm, d1=0.7d2, and L=5.1mm.

[0036] In this embodiment, the tapered helical long cutting edge 71 is connected to the main cutting edge 5 and the guide cutting edge 4 at its ends. The axial length of the tapered helical long cutting edge 71 is L1, and the axial length of the tapered helical short cutting edge 72 is L2. Since the back face of the main cutting edge 5 has lag, in order to ensure that the micro milling edge is distributed within the tapered milling area 9, the axial length L2 of the tapered helical short cutting edge 72 must be shorter than the axial length L1 of the tapered helical long cutting edge 71. It should satisfy: L1>L2, L1=L. In this embodiment, L1=5.1mm, L2=3.9mm.

[0037] In this embodiment, the micro-milling blade 8 is formed by the interference of the chip-breaking groove 81 and the tapered portion of the blade 7. The micro-milling blade 8 is evenly distributed along the helical direction on the tapered helical long blade 71 and the tapered helical short blade 72.

[0038] In this embodiment, the long spiral chip removal groove 3 and the short spiral chip removal groove 73 are rotated in the right direction, and the chip separation groove 81 is rotated in the left direction.

[0039] In this embodiment, the length of the micro-milling edge 8 along the tangential direction of the short helical chip removal groove 73 is L3. If the tangential length of the micro-milling edge 8 along the short helical chip removal groove 73 is too long, it will increase the friction between the back face and the machined surface, which is not conducive to reducing the axial cutting force. If it is too short, it will reduce the strength of the cutting edge and the milling ability. It should satisfy: L3 = 0.1d2 ~ 0.14d2. The width along the normal direction of the short helical chip removal groove 73 is L4. In order to ensure the strength of the cutting edge and the chip sorting ability of the short helical chip removal groove 73, it should satisfy: L4 = 0.04d2 ~ 0.07d2. It has a planar clearance angle γ along the radial direction of the twist drill. In order to ensure that the radial planar clearance angle of the micro-milling edge 8 does not affect the milling ability and the strength of the cutting edge, it should satisfy: 3° ≤ γ ≤ 12°. In this embodiment, L3 = 0.71mm, L4 = 0.36mm, and γ = 8°.

[0040] The radial depth of the chip-breaking groove 81 is half the radial depth of the short helical chip-removing groove 73. The helix angle of the chip-breaking groove 81 is β. To ensure that the micro-milling edge 8 has a good grinding effect, it should satisfy: 15°≤β<90°. When the helix angle β of the chip-breaking groove 81 is less than 15°, the rear cutting edge of the micro-milling edge 8 formed in the taper milling area 9 will form a thin sharp angle, which is easy to chip during the machining process and thus damage the machined surface. At the same time, the angle between the chip-breaking groove 81 and the feed direction is too small, which is not conducive to chip removal. When β>90°, the chip-breaking groove 81 will have the same spiral direction as the long helical chip-removing groove 3, which cannot achieve the technical effect of this embodiment. In this embodiment, β=70°.

[0041] Figure 6 and Figure 7This invention illustrates a second embodiment of the twist drill with milling edges, which is essentially the same as the first embodiment, except that in this embodiment, each cutting edge 7 in the taper milling region 9 includes three sets of short helical chip removal grooves 73, i.e. Figure 7 Types 73a, 73b, and 73c, correspondingly, contain three tapered helical short blades 72, i.e. Figure 7 Examples 72a, 72b, and 72c are provided. This embodiment is suitable for twist drills with a larger diameter (d2 ≥ 10 mm) and a larger cutting edge 7 width. In this embodiment, α = 10°, d2 = 10 mm, d1 = 0.7d2, L = 8.5 mm, L1 = 8.5 mm, L2 = 6.6 mm, L3 = 1.18 mm, L4 = 0.6 mm, γ = 8°, and β = 70°.

[0042] Figure 8 and Figure 9 A third embodiment of the twist drill with milling edges of the present invention is shown. This embodiment is basically the same as the first embodiment, except that: in this embodiment, the tapered milling area 9 includes three cutting edges 7, each cutting edge 7 including a short helical chip removal groove 73, and correspondingly, contains a tapered helical short cutting edge 72. This embodiment is more suitable for high-efficiency machining. In this embodiment, α = 10°, d2 = 6mm, d1 = 0.7d, L = 5.1mm, L1 = 5.1mm, L2 = 3.9mm, L3 = 0.71mm, L4 = 0.36mm, γ = 8°, β = 70°.

[0043] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A twist drill having a milling edge, comprising a shank (1) and a cutting portion (2), the cutting portion (2) being provided with a plurality of long helical flutes (3) extending in the direction of a central axis (10) of the twist drill towards the shank (1) and a guide edge band (4), a front end portion of the long helical flutes (3) being provided with a main cutting edge (5) and a cross edge (6), characterized in that: The side of the long spiral chip flute (3) is provided with a taper milling area (9), the taper milling area (9) comprises a plurality of blade petals (7), the blade petals (7) are provided with a taper spiral long blade (71), a taper spiral short blade (72) and a short spiral chip flute (73), the short spiral chip flute (73) has the same rotation direction as the long spiral chip flute (3), the taper spiral long blade (71) comprises M groups of micro milling blades (8) connected in series along the spiral direction of the taper spiral long blade (71), the taper spiral short blade (72) comprises N groups of micro milling blades (8) connected in series along the spiral direction of the taper spiral short blade (72), and M≥2, N≥2, the micro milling blade (8) is provided with a chip division groove (81) opposite in rotation direction to the long spiral chip flute (3).

2. A twist drill having a milling edge according to claim 1, characterized in that: The blade petals (7) are provided with a taper spiral long blade (71) and a plurality of taper spiral short blades (72), the taper spiral long blade (71) is located between the long spiral chip flute (3) and the first short spiral chip flute (73) and is connected with the guide blade band (4), and the taper spiral short blade (72) is located between adjacent two short spiral chip flutes (73) or between the last short spiral chip flute (73) and the next long spiral chip flute (3).

3. A twist drill having a milling edge according to claim 1, characterized in that: The taper angle of the taper milling area (9) is α, and 6°≤α≤35°.

4. A twist drill having a milling edge according to claim 3, characterised in that: The axial length of the taper milling area (9) is L, the small end diameter is d1, the large end diameter, that is, the tool blade diameter of the twist drill, is d2, and L=0.5(d2-d1) / tanα, 0.5d2≤d1≤0.8d2.

5. A twist drill having a milling edge according to claim 4, characterised in that: The taper spiral long blade (71) is connected with the main cutting edge (5) and the guide blade band (4) at the head and tail respectively, the axial length of the taper spiral long blade (71) is L1, the axial length of the taper spiral short blade (72) is L2, and L1>L2, L1=L.

6. Twist drill with a milling edge according to any one of claims 1 to 5, characterized in that: The micro milling blade (8) is formed by the interference of the chip division groove (81) and the taper part of the blade petal (7), and the micro milling blade (8) is uniformly distributed on the taper spiral long blade (71) and the taper spiral short blade (72) in the spiral direction.

7. Twist drill with a milling edge according to any one of claims 1 to 5, characterized in that: The rotation directions of the long spiral chip flute (3) and the short spiral chip flute (73) are right-handed, and the rotation direction of the chip division groove (81) is left-handed.

8. A twist drill having a milling edge according to claim 3 or 4, characterised in that: The length of the micro milling blade (8) in the tangential direction of the short spiral chip flute (73) is L3, the width of the micro milling blade (8) in the normal direction of the short spiral chip flute (73) is L4, the micro milling blade (8) has a planar relief angle γ in the radial direction of the twist drill, and L3=0.1d2-0.14d2, L4=0.04d2-0.07d2, 3°≤γ≤12°.

9. Twist drill with a milling edge according to any one of claims 1 to 5, characterized in that: The radial depth of the chip division groove (81) is half of the radial depth of the short spiral chip flute (73), and the spiral angle of the chip division groove (81) is β, and 15°≤β<90°.

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