Twist drill with milling edges

Abstract

The twist drill comprises a cutter handle and a cutting part, the cutting part is provided with a plurality of long spiral chip grooves and guide edge strips which extend towards the cutter handle in the direction of the central axis of the twist drill, the front ends of the long spiral chip grooves are provided with main cutting edges and chisel edges, and the side portions of the long spiral chip grooves are provided with taper milling areas. The taper milling area comprises a plurality of blade sections, taper spiral long blades, taper spiral short blades and short spiral chip grooves are arranged on the blade sections, the short spiral chip grooves and the long spiral chip grooves have the same rotation direction, the taper spiral long blades comprise N groups of micro milling blades which are connected in series along the spiral direction of the taper spiral long blades, the taper spiral short blade comprises N groups of micro-milling blades which are connected in series in the spiral direction of the taper spiral short blade, and the condition that N is larger than or equal to 2 is met, and the micro-milling blades are provided with chip dividing grooves with the spiral direction opposite to that of the long spiral chip discharging grooves, and the composite material drill bit has the advantages of being capable of being used for composite material drilling machining, high in drilling efficiency, high in machining precision, good in quality and the like.

Description

Technical Field

[0001] The invention mainly relates to the field of composite material cutting and processing, and in particular to a twist drill with a milling edge. Background Art

[0002] Composite materials usually have very excellent specific strength and specific modulus, and have excellent fatigue resistance and corrosion resistance, good shock absorption performance and thermal stability. They have very broad application prospects in high-tech fields such as aerospace, especially fiber reinforced composite materials (FRP), which are widely used in military aircraft, unmanned fighters, missiles, rockets, satellites, etc. However, due to the special preparation process of FRP, its mechanical properties are anisotropic and the interlaminar strength is low. At present, most FRP hole making processes still use drilling, expansion, reaming, countersinking and other methods, which are very easy to produce processing defects such as delamination, burrs, and tearing on the hole exit and entrance sides, reducing the strength of the workpiece. In severe cases, it will cause the workpiece to be scrapped. These processing defects have seriously restricted the promotion and application of FRP.

[0003] Research shows that when processing FRP with ordinary drill bits used for processing conventional metal materials, material delamination, hole tearing, fiber pullout on the hole wall surface, etc. are likely to occur, and ordinary drill bits are not suitable for processing such materials. As various industries have higher requirements for processing efficiency, high-feed processing is also applied to FRP hole making, which makes hole defects more likely to occur.

[0004] Chinese patent document CN210254406U discloses a three-pointed and fine-toothed drilling and milling composite tool, in which the milling part is located between the drill tip and the tool handle, and includes 4 to 6 spiral blades, and the spiral blades are divided into a number of fine teeth by chip breakers with the same rotation direction and a larger spiral angle. In the processing of carbon fiber composite materials, the method of drilling first and then milling is adopted, and the fine-tooth milling of the milling part is used to greatly reduce the cutting amount and cutting force, and remove the defects caused by drilling. However, although the three-pointed drill bit has the advantages of fast hole making speed and not easy to produce burrs or cracks, it is only suitable for large holes due to the limitation of the head shape, and it is easy to generate large friction and heat during the drilling process.

[0005] Chinese patent document CN107030319B discloses a milling and drilling composite tool having a drill tip and a tapered milling edge, and a spiral groove is provided on the back of the tapered milling edge. The tapered milling edge can significantly reduce the chip thickness during processing, change the distribution state of the drilling force, and suppress the defects at the hole exit. At the same time, multiple milling edges can reduce the feed per tooth, which is suitable for large feed processing. However, in large feed processing, when more grooves are provided on the back of the milling edge, the milling edge will inevitably be thinner and prone to chipping. In addition, the increase in milling edges will also increase the friction, which is not conducive to reducing the axial force, but increases the defects of the processed hole. Summary of the invention

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

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A twist drill with a milling blade comprises a shank and a cutting portion, the cutting portion being provided with a plurality of long spiral chip grooves and guide blade bands extending toward the shank along the central axis direction of the twist drill, the front end portion of the long spiral chip groove being provided with a main cutting edge and a transverse edge, the side portion of the long spiral chip groove being provided with a tapered milling area, the tapered milling area comprising a plurality of blade petals, the blade petals being provided with a tapered spiral long blade, a tapered spiral short blade and a short spiral chip groove, the short spiral chip groove having the same rotation direction as the long spiral chip groove, the tapered spiral long blade comprising M groups of micro-milling blades connected in series along the spiral direction of the tapered spiral long blade, the tapered spiral short blade comprising N groups of micro-milling blades connected in series along the spiral direction of the tapered spiral short blade, and satisfying: M≥2, N≥2, the micro-milling blade being provided with a chip dividing groove having a rotation direction opposite to that of the long spiral chip groove.

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

[0010] The blade petal is provided with a tapered spiral long edge and a plurality of tapered spiral short edges, the tapered spiral long edge is located between the long spiral chip groove and the first short spiral chip groove and is connected to the guide blade band, and the tapered spiral short edge is located between two adjacent short spiral chip grooves or between the last short spiral chip groove and the next long spiral chip groove.

[0011] The taper angle of the taper 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, the large end diameter, i.e., the tool cutting edge diameter of the twist drill is d2, and the following conditions are satisfied: L=0.5(d2-d1) / tanα, 0.5d2≤d1≤0.8d2.

[0013] The tapered spiral long edge is connected to the main cutting edge and the guide edge band at its head and tail, the axial length of the tapered spiral long edge is L1, the axial length of the tapered spiral short edge is L2, and the following conditions are satisfied: L1>L2, L1=L.

[0014] The micro-milling edge is formed by the interference of the chip dividing groove and the tapered part of the edge petal, and the micro-milling edge is evenly distributed on the tapered spiral long edge and the tapered spiral short edge along the spiral direction.

[0015] The hand direction of the long spiral chip removal groove and the short spiral chip removal groove is right-handed, and the hand direction of the chip dividing groove is left-handed.

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

[0017] The radial depth of the chip dividing groove is half of the radial depth of the short spiral chip dividing groove, and the helix angle of the chip dividing groove is β, and satisfies: 15°≤β<90°.

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

[0019] The twist drill with milling blades of the present invention has a tapered milling area on the side of the long spiral chip groove, and the tapered milling area includes multiple blade petals, and the blade petals are provided with a tapered spiral long blade, a tapered spiral short blade and a short spiral chip groove, and the short spiral chip groove has the same rotation direction as the long spiral chip groove, and the tapered spiral long blade includes M groups of micro-milling blades connected in series along the spiral direction of the tapered spiral long blade, and the tapered spiral short blade includes N groups of micro-milling blades connected in series along the spiral direction of the tapered spiral short blade, and the following conditions are satisfied: M≥2, N≥2, and the micro-milling blade is provided with a chip dividing groove with a rotation direction opposite to that of the long spiral chip groove, that is, the multiple blade petals of the cutting part are located in the tapered milling area and have a taper angle, and the tapered spiral long blade and the tapered spiral short blade on the blade petal are both formed by connecting a number of micro-milling blades in series along the spiral direction. On the one hand, this structure can significantly reduce the chip thickness and effectively reduce the axial component of the drilling force because the milling area has a taper angle much smaller than the drill tip angle, thereby inhibiting the delamination, splitting and roughness of the hole outlet. The occurrence of burr phenomenon; on the other hand, because the milling area has multiple micro-milling blades arranged in a tapered spiral, multiple micro-milling blades 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 a large feed amount to improve cutting efficiency. The staggered micro-milling blades can be regarded as an orderly arrangement of abrasive particles, integrating drilling and grinding, which can achieve grinding effect and improve the surface quality of the processed hole. The micro-milling blade is provided with a chip groove with a rotation direction opposite to the long spiral chip groove, thereby forming a micro-milling blade, which can improve the chip removal performance and cooling effect. At the same time, the sharp micro-milling blade cuts the machined surface multiple times during drilling, which can further reduce the delamination, splitting and burr formation of the hole mouth, and improve the quality of the machined hole. In addition, the cutting force of the composite material is large during processing, and the cutting heat is not easy to be transmitted, which can easily cause the processed material to burn or soften and the tool to wear seriously. The staggered and interlaced mesh grooves are conducive to the inflow of cutting fluid, which is conducive to heat dissipation during processing and reduces damage to the tool and workpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1It is a schematic structural diagram of a first embodiment of a twist drill with a milling edge according to the present invention.

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

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

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

[0024] Figure 5 It 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 It is a schematic structural diagram of a second embodiment of a twist drill with a milling edge according to the present invention.

[0026] Figure 7 yes Figure 6 B view.

[0027] Figure 8 It is a schematic structural diagram of a third embodiment of a twist drill with a milling edge according to the present invention.

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

[0029] The symbols in the figure represent:

[0030] 1. Tool holder; 2. Cutting part; 3. Long spiral chip groove; 4. Guide edge band; 5. Main cutting edge; 6. Transverse edge; 7. Edge flap; 71. Tapered spiral long edge; 72. Tapered spiral short edge; 73. Short spiral chip groove; 8. Micro milling edge; 81. Chip dividing groove; 9. Tapered milling area; 10. Center axis. DETAILED DESCRIPTION

[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 the present invention, it should be noted that terms such as "center", "up", "down", "horizontal", "inside", "outside", "top", and "bottom" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0033] Figures 1 to 5The first embodiment of the twist drill with milling edge of the present invention is shown. The twist drill with milling edge of the embodiment comprises a shank 1 and a cutting portion 2. The cutting portion 2 is provided with two long spiral chip grooves 3 and two guide lands 4 extending toward the shank 1 along the central axis 10 of the twist drill. The guide lands 4 are cylindrical. The front end of the long spiral chip groove 3 is provided with two main cutting edges 5 and a transverse edge 6. The long spiral chip groove 3 is mainly used to accommodate the chips formed in the cutting process of the main drilling cutting edge 5 and the transverse edge 6, and to provide a discharge channel for the chips. The guide lands 4 play a guiding role and at the same time, during the processing It can squeeze the inner wall of the hole to improve the surface quality and dimensional accuracy of the hole. In order to ensure the stability of the drilling process, the long spiral chip groove 3 and the guide edge band 4 are usually designed to be symmetrical about the axis of the drill bit. The main cutting edge 5 and the transverse edge 6 are used to drill a circular hole slightly smaller than the finished hole size, thereby reducing the cutting depth of the milling edge. At the same time, the transverse edge 6 has a centering effect to ensure the position accuracy of the processed hole. The side of the long spiral chip groove 3 is provided with a tapered milling area 9, and the tapered milling area 9 includes two edge petals 7. One edge petal 7 is provided with a tapered spiral long edge 71 and two tapered spiral short edges 72 (i.e. Figure 1 72a and 72b) and two short spiral chip removal grooves 73 (i.e. Figure 173a and 73b), the short spiral chip groove 73 has the same hand direction as the long spiral chip groove 3, the tapered spiral long edge 71 includes M groups of micro-milling edges 8 connected in series along the spiral direction of the tapered spiral long edge 71, and the tapered spiral short edge 72 includes N groups of micro-milling edges 8 connected in series along the spiral direction of the tapered spiral short edge 72, and satisfies: M≥2, N≥2. In this embodiment, M and N are both equal to 6, and the micro-milling edge 8 is provided with a chip dividing groove 81 having a hand direction opposite to that of the long spiral chip groove 3. That is, the two blade petals 7 of the cutting portion 2 have a taper angle in the taper milling area, and the taper spiral long edge 71 and the taper spiral short edge 72 on the blade petal 7 are both formed by a plurality of micro-milling edges 8 connected in series along the spiral direction. On the one hand, this structure can significantly reduce the chip thickness and effectively reduce the axial component of the drilling force because the milling area has a taper angle much smaller than the drill tip angle, thereby inhibiting the occurrence of hole exit delamination, splitting and burr phenomena; on the other hand, because the milling area has a plurality of micro-milling edges 8 arranged in a taper spiral, the milling area can be easily cut. Milling blade 8, multiple micro-milling blades 8 can effectively reduce the feed amount per tooth and reduce the cutting load of a single tooth, so it can be applied to working conditions with a large feed amount to improve cutting efficiency. The staggered micro-milling blades 8 can be regarded as an orderly arrangement of abrasive particles, integrating drilling and grinding, which can achieve grinding effect and improve the surface quality of the processed hole. The micro-milling blade 8 is provided with a chip groove 81 with a rotation direction opposite to the long spiral chip groove 3, thereby forming a micro-milling blade 8, which can improve the chip removal performance and cooling effect at the same time. At the same time, the sharp micro-milling blade 8 performs multiple cutting on the processed surface during drilling, which can further reduce the stratification, splitting and burr formation of the hole mouth, and improve the quality of the processed hole. Since the cutting force of the composite material is large during processing, the cutting heat is not easy to be transmitted, which can easily cause the processed material to burn or soften and the tool to wear seriously. In this embodiment, the staggered and interlaced mesh grooves formed by the chip grooves 81 and the long spiral chip grooves 3 are conducive to the inflow of cutting fluid, heat dissipation during processing, and reduce damage to the tool and workpiece.

[0034] In this embodiment, the taper angle of the taper milling area 9 is α (eg Figure 3 As shown), in order to avoid causing the taper milling area 9 to be too long, which limits the application range of the twist drill; and not thickening the chips and increasing the cutting force, which is not conducive to reducing the axial cutting force, it should meet the following requirements: 6°≤α≤35°. In this embodiment, α=10°.

[0035] In this embodiment, the axial length of the tapered milling area 9 is L, the small end diameter is d1, and the large end diameter, i.e., the tool cutting diameter of the twist drill, is d2. After the cone angle α of the tapered milling area 9 is determined, in order to ensure that the axial length of the milling area does not affect the axial cutting force of the drill bit, it should satisfy: 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 spiral long edge 71 is connected to the main cutting edge 5 and the guide edge band 4 at the head and tail respectively, the axial length of the tapered spiral long edge 71 is L1, and the axial length of the tapered spiral short edge 72 is L2. Since there is a lag on the back face of the main cutting edge 5, in order to ensure that the micro-milling edge is distributed in the tapered milling area 9, the axial length L2 of the tapered spiral short edge 72 must be shorter than the axial length L1 of the tapered spiral long edge 71, and should satisfy: L1>L2, L1=L. In this embodiment, L1=5.1mm, L2=3.9mm.

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

[0038] In this embodiment, the hand direction of the long spiral chip removal groove 3 and the short spiral chip removal groove 73 is right-handed, and the hand direction of the chip dividing groove 81 is left-handed.

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

[0040] The radial depth of the chip groove 81 is half of the radial depth of the short spiral chip groove 73, and the helix angle of the chip groove 81 is β. To ensure that the micro-milling blade 8 has a better grinding effect, it should satisfy the following conditions: 15°≤β<90°. When the helix angle β of the chip groove 81 is <15°, the rear end cutting edge of the micro-milling blade 8 formed within the range of the tapered milling area 9 will form a thin sharp angle, which is prone to chipping during machining and thus damaging the machined surface. At the same time, the angle between the chip groove 81 and the feed direction is too small, which is not conducive to chip removal. When β>90°, the chip groove 81 will have the same rotation direction as the long spiral chip groove 3, and the technical effect of this embodiment cannot be achieved. In this embodiment, β=70°.

[0041] Figure 6 and Figure 7The second embodiment of the twist drill with milling edge of the present invention is shown, which is basically the same as the first embodiment, except that: in this embodiment, each blade 7 in the tapered milling area 9 includes three groups of short spiral chip removal grooves 73, namely Figure 7 73a, 73b and 73c, respectively, contain three tapered spiral short blades 72, namely Figure 7 This embodiment is suitable for twist drills with larger diameters (d2 ≥ 10 mm) and larger blade widths. 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 Fig. 9 A third embodiment of the twist drill with a milling edge of the present invention is shown, which is basically the same as the first embodiment, with the only difference that: in this embodiment, the tapered milling area 9 includes three blade lobes 7, each blade lobe 7 includes a short spiral chip groove 73, and correspondingly, contains a tapered spiral short blade 72. This embodiment is more suitable for efficient 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] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the technical content disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should fall within the scope of protection of the technical solution of the present invention.

Claims

1. A twist drill with a milling edge, comprising a shank (1) and a cutting portion (2), wherein the cutting portion (2) is provided with a plurality of long spiral chip grooves (3) and guide edge bands (4) extending toward the shank (1) along the central axis (10) of the twist drill, wherein the front end of the long spiral chip groove (3) is provided with a main cutting edge (5) and a chisel edge (6), and wherein: A tapered milling area (9) is provided on the side of the long spiral chip groove (3), and the tapered milling area (9) includes a plurality of blade petals (7), and the blade petals (7) are provided with a tapered spiral long blade (71), a tapered spiral short blade (72) and a short spiral chip groove (73), and the short spiral chip groove (73) has the same hand direction as the long spiral chip groove (3), and the tapered spiral long blade (71) includes M groups of micro-milling blades (8) connected in series along the spiral direction of the tapered spiral long blade (71), and the tapered spiral short blade (72) includes N groups of micro-milling blades (8) connected in series along the spiral direction of the tapered spiral short blade (72), and the conditions are satisfied: M≥2, N≥2, and the micro-milling blade (8) is provided with a chip dividing groove (81) having a hand direction opposite to that of the long spiral chip groove (3).

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

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

4. The twist drill with a milling edge according to claim 3, characterized in that: The axial length of the tapered milling area (9) is L, the small end diameter is d1, the large end diameter, i.e. the tool edge diameter of the twist drill is d2, and the following conditions are satisfied: L=0.5(d2-d1) / tanα, 0.5d2≤d1≤0.8d2.

5. The twist drill with a milling edge according to claim 4, characterized in that: The tapered spiral long edge (71) is connected to the main cutting edge (5) and the guide edge band (4) at its head and tail, respectively; the axial length of the tapered spiral long edge (71) is L1, the axial length of the tapered spiral short edge (72) is L2, and the following conditions are satisfied: L1>L2, L1=L.

6. The twist drill with a milling edge according to any one of claims 1 to 5, characterized in that: The micro-milling edge (8) is formed by the interference of the chip dividing groove (81) and the tapered part of the edge flap (7), and the micro-milling edge (8) is evenly distributed on the tapered spiral long edge (71) and the tapered spiral short edge (72) along the spiral direction.

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

8. The twist drill with a milling edge according to claim 3 or 4, characterized in that: The micro-milling blade (8) has a tangential length L3 along the short spiral chip groove (73), a normal width L4 along the short spiral chip groove (73), and has a plane back angle γ along the radial direction of the twist drill, and satisfies: L3 = 0.1d2 ~ 0.14d2, L4 = 0.04d2 ~ 0.07d2, 3°≤γ≤12°.

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

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