CN113844064B - CFRP low-damage sliding cutting method and drilling bit - Google Patents

Abstract

The invention discloses a CFRP low-damage sliding cutting method, wherein any point on a cutting edge moves along a composite cutting direction and slides along a tangential direction of the cutting edge at the point so as to finish CFRP cutting under the extrusion action of a cutter point and the sliding shearing action of the cutting edge. Under the cutting method, the fiber is not only extruded by the knife tip which is the same as the conventional right angle/oblique angle cutting, but also is mainly subjected to the sliding shearing action of the cutting edge, the fiber is more easily cut off under the combined action of the extrusion and the sliding shearing action of the knife tip, the deformation of the fiber before fracture is reduced, the fracture point is closer to the theoretical position, the higher machining surface precision is finally achieved, the subsurface damage is effectively controlled, and the fracture position of the fiber is closer to the expected position. The invention also provides a CFRP low-damage hole drilling bit which can carry out sliding cutting of the CFRP, solves the problem of subsurface damage of the hole wall, improves the hole diameter precision and improves the machining quality of the CFRP.

Description

A CFRP low-damage sliding cutting method and hole-making drill bit

technical field

The invention belongs to the field of mechanical processing, and relates to a CFRP material hole-making process, in particular to a CFRP low-damage sliding cutting method and a hole-making drill bit.

Background technique

CFRP (full name: Carbon Fiber Reinforced Polymer) is the English abbreviation of carbon fiber reinforced resin-based composite materials.

CFRP laminated structures have been widely used in the aerospace field. For the hole-making process of CFRP materials, the existing methods mainly use tools such as twist drills, dagger drills or other improved drills. Taking the twist drill as an example, its structure is shown in Figure 1-2. Under the main motion and feed motion, the cutting edge spirals downward to remove material. Each layer of CFRP is anisotropic. If a section perpendicular to the axis of the drill bit is made during the drilling process, the main cutting edge is discretely divided into a series of cutting microelements. When the length of each microelement is equivalent to the fiber diameter, it can be Approximately, it is considered to make a square or bevel cut as shown in Figure 2 (right). All the cutting micro-elements constitute the entire cutting edge, and its function is essentially to cut off the fiber and the matrix at the expected position, and each cutting edge cooperates with each other to complete the hole-making action. The material removal process of other existing drill bits is similar to that of twist drills. Both the fiber and the matrix are removed under the right angle or oblique cutting of the cutting edge. This process is the typical basic behavior of drilling.

As shown in Figures 1 and 2, due to the significant anisotropy of the CFRP laminated structure, when the existing twist drill or dagger drill is used for processing, due to the above-mentioned right-angle or oblique cutting of the main cutting edge, the The hole-making quality varies greatly with different fiber directions. Define the angle θ between the main motion and the fiber as the fiber direction angle (as shown in Figure 2). When 0°<θ<90°, the fiber is squeezed by the cutting edge and breaks, the actual break point is not much different from the theoretical break point, and the bending deformation of the fiber is small, so it will not affect the machined surface (hole wall) and Severe damage to the subsurface (the material inside the hole walls). However, when 90°<θ<180°, the fibers are mainly bent due to the pushing of the rake face, and the actual fracture points are scattered and distributed due to the different bending degrees of the fibers, which is far from the theoretical fracture point. Deformation, large-area cracking at the fiber-matrix interface, and the cracks continue to expand along the fiber direction, resulting in a sharp increase in the roughness of the processed surface and frequent occurrence of subsurface cracks. However, the tool has to cut with a large fiber orientation angle (ie 90°<θ<180°) during the hole making cycle, which has become the main defect and bottleneck of the prior art.

Contents of the invention

The purpose of the present invention is to provide a CFRP low-damage sliding cutting method and hole-making drill bit to solve the problems of poor surface quality, sub-surface damage and micro-crack damage caused by cutting with large fiber direction angles in the above-mentioned traditional hole-making technology And other issues, can further improve the quality of CFRP processing.

To achieve the above object, the present invention provides the following scheme:

The invention provides a CFRP low-damage sliding cutting method, comprising:

In addition to moving along the composite cutting direction, any point on the cutting edge also slides along the direction tangent to the point of the cutting edge, so as to complete the CFRP cutting under the extrusion action of the tip and the sliding shearing action of the cutting edge processing.

Optionally, any point on the cutting edge has:

Velocity v _s1 along the cutting direction resulting from the main motion and the feed motion;

Sliding cutting speed v _s2 tangential to the cutting edge.

The present invention proposes a CFRP low-damage drilling bit, comprising:

A drill body, the end of the drill body is provided with a tip structure, and the tip structure is used to provide extrusion force along the drilling feed direction;

Sliding cutting edge, the sliding cutting edge is arranged on the outer wall of the drill body, and a plurality of sliding cutting edges are arranged at intervals along the axial direction of the drill body; Sliding shear force in the tangential direction of the cutting edge;

The secondary edge of the drill, the secondary edge of the drill is arranged at intervals along the axial direction of the drill body, and any one of the secondary edges of the drill is connected with one of the sliding cutting edges to form a margin; the secondary edge of the drill is used for It is used to remove the hole wall fiber and matrix during the drilling process. The auxiliary edge of the drill bit can cut off the fiber of the hole wall multiple times to obtain higher hole diameter accuracy.

Optionally, the drill bit body is provided with a first cutting zone, a second cutting zone and a third cutting zone in sequence along the reverse direction of its drilling feed; the sliding cutting edge is set on the second cutting zone and the The third cutting zone and the first cutting zone are only provided with the drill bit chisel edge, the main cutting edge and the drill bit secondary edge.

Optionally, the diameter of the drill bit body gradually increases along the opposite direction of its drilling feed.

Optionally, the rake angle range of any of the sliding cutting edges is 10°-30°, and the rear angle range is 2°-5°.

Optionally, a cutting groove is formed between any two adjacent margins; the groove depth of the cutting groove is 1-1.5mm, and the groove width is 1-1.5mm.

Optionally, the width of any of the margins is 1-1.5 mm.

Optionally, any of the sliding cutting edges are located in a plane perpendicular to the axial direction of the drill bit.

Optionally, the sliding cutting edges of the second cutting zone and the third cutting zone are prepared in the form of ring grooves, and any ring grooves have a spiral tendency, and correspondingly, any of the sliding cutting edges also have spiral trend.

Compared with the prior art, the present invention has achieved the following technical effects:

The CFRP low-damage sliding cutting method proposed by the present invention, in order to avoid excessive damage to the material around the hole caused by cutting with a large fiber direction angle, the fiber and matrix in CFRP are cut by sliding cutting. The fiber is not only affected by the existing right angle/oblique angle The same extrusion effect of the cutting edge is more mainly affected by the sliding shearing effect of the cutting edge. Due to the high brittleness of the fibers in CFRP, the tool slides and shears the fibers by friction, which increases the stress concentration in the local contact area. Therefore, under the combined action of the extrusion and sliding shear of the knife tip, the fibers are more likely to be cut. The deformation before fracture is reduced, and the fracture point is closer to the theoretical position, which ultimately achieves higher machining surface accuracy, and the subsurface damage is also effectively controlled so that the fiber fracture position is closer to the expected position.

The present invention also proposes a CFRP low-damage hole-making drill bit, which can be used for sliding cutting of CFRP. The extrusion force in the same direction and multiple sliding cutting edges work together to gradually remove the material around the hole, which also solves the problem of subsurface damage on the hole wall, improves the hole diameter accuracy, and can further improve the CFRP processing quality.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

Fig. 1 is the schematic diagram of cutting form of traditional drilling process;

Fig. 2 is A-A sectional view among Fig. 1;

Fig. 3 is a schematic diagram of right-angle or oblique-angle cutting performed by main cutting edge elements in the existing hole-making process;

Fig. 4 is an analysis diagram of the sliding cutting principle disclosed in the embodiment of the present invention;

Fig. 5 is a three-dimensional schematic diagram of a CFRP low-damage hole-making drill bit disclosed by an embodiment of the present invention;

Fig. 6 is an axial schematic diagram of the CFRP low-damage drilling drill bit disclosed by the embodiment of the present invention;

Fig. 7 is a side view of the CFRP low-damage drilling drill bit disclosed by the embodiment of the present invention;

Fig. 8 is a schematic diagram of the setting position of the sliding cutting edge in the CFRP low-damage hole-making drill bit disclosed by the embodiment of the present invention;

Fig. 9 is a schematic diagram of the movement track in one cycle of the CFRP low-damage hole-making drill bit disclosed by the embodiment of the present invention;

Fig. 10 is a schematic diagram of partitions of the CFRP low-damage hole-making drill bit disclosed by the embodiment of the present invention.

Wherein, the reference signs are: 1, CFRP; 2, tool; 21, tip; 3, substrate; 4, fiber; 5, drill body; 51, sliding cutting edge; 52, secondary edge of drill; 53, margin; 54. Cutting edge groove;

C _z1 , the first cutting zone; C _z2 , the second cutting zone; C _z3 , the third cutting zone.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

One of the purposes of the present invention is to provide a CFRP low-damage sliding cutting method to solve the problems of poor surface quality, subsurface damage and microcrack damage caused by cutting with large fiber direction angles in traditional hole making technology, The processing quality of CFRP can be further improved.

Another object of the present invention is to provide a CFRP low-damage drilling drill, which can be used for sliding cutting of CFRP.

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Embodiment one

This embodiment provides a low-damage sliding cutting method for CFRP, specifically: in addition to feeding along the composite cutting direction, any point on the cutting edge also slides along a direction tangent to the cutting edge to squeeze The CFRP drilling process is completed under the action of sliding and shearing of the cutting edge. Among them, the "synthetic cutting direction" refers to the cutting direction synthesized along the main motion and the feed motion.

In this embodiment, any point on the cutting edge has the cutting velocity v _s1 along the cutting direction synthesized by the main movement and the feed movement and the sliding cutting velocity v _s2 in the direction tangential to the cutting edge.

In this embodiment, when the CFRP low-damage sliding cutting method is used to drill CFRP, it is preferable that the cutting direction (feeding direction) is perpendicular to any layer in CFRP. Drilling for other materials is also possible.

The specific implementation of the CFRP low-damage sliding cutting method in this embodiment will be described in detail below.

As shown in Figure 3, the right angle or bevel cutting performed by the main cutting edge micro-element in the existing hole making process is given. Its characteristic is that any point i _o on the cutting edge only moves in the direction of the same speed v _o as the cutting direction (the direction of drill bit feeding), and the fiber is squeezed by the tool tip 21. When the extrusion effect reaches a certain level, the The stress state can meet the fracture conditions. At this time, the fibers near the tool tip 21 will be deformed to different degrees, and then microcracks will be formed. The tool 2 continues to move forward, and the cracks will expand downward along the fiber direction, causing subsurface damage.

As shown in Figure 4, the principle analysis of sliding cutting using the CFRP low-damage sliding cutting method of this embodiment is given. Any point i _s on the cutting edge is along the synthetic cutting direction (same as the drill bit feed direction, but in fact the main movement The cutting direction synthesized with the feed motion) has the main motion speed v _s1 (the same speed as the aforementioned v _s1 ), and is also provided with a sliding cutting speed v _s2 tangential to the cutting edge (the same speed as the aforementioned v _s2 ). The beneficial effect is that the fibers are not only subject to the same extrusion action as the aforementioned (as shown in Figures 1-3) right angle/bevel cutting, but also more mainly subject to the sliding shear action of the cutting edge. Due to the specific high brittleness of the fiber, the tool 2 friction shears with the fiber due to sliding, which increases the stress concentration in the local contact area. As a result, under the combined action of extrusion and shearing of the knife tip 21, the fiber is more easily cut off, reducing its deformation before breaking, so the breaking point is closer to the theoretical position, and finally achieves a higher processing surface Precision, sub-surface damage can also be effectively controlled.

It can be seen that the sliding cutting method for fibers and matrix in CFRP 1 proposed by the present invention is to provide sliding cutting speed (or sliding cutting force) in the lateral direction while the cutting edge is performing traditional right-angle or oblique cutting, so that the cutting The blade and the fiber produce a strong shearing effect to achieve a better cutting effect, that is, the fiber fracture position is closer to the expected position, and the precision of the drilling hole diameter is improved.

Embodiment two

As shown in Figures 5-10, this embodiment provides a CFRP low-damage hole-making drill, including a drill body 5, a sliding cutting edge 51 and a drill secondary edge 52, the sliding cutting edge 51 is arranged on the outer wall of the drill body 5, and slides The cutting edge 51 is provided with a plurality of intervals along the axial direction of the drill body 5; the sliding cutting edge 51 is used to provide a sliding shear force tangential to the sliding cutting edge 51; There are a plurality of them arranged at intervals along the axial direction of the drill body 5, and any secondary edge 52 of the drill is connected with a sliding cutting edge 51 to form a margin 53; the secondary edge 52 of the drill is used to provide extrusion along the feed direction force. The aforementioned CFRP low-damage drilling drill can be used to implement the CFRP low-damage sliding cutting method described in Embodiment 1.

In this embodiment, as shown in Figure 10, the drill body 5 is provided with a first cutting zone C _z1 , a second cutting zone C _z2 and a third cutting zone C _z3 sequentially along the opposite direction of its cutting feed; the sliding cutting edge 51 is set in the second cutting zone C _z2 and the third cutting zone C _z3 , and the first cutting zone C _z1 is only provided with the secondary cutting edge 52 of the drill.

In this embodiment, the diameter of the drill body 5 gradually increases along the opposite direction of its cutting feed.

In this embodiment, the range of the rake angle of any sliding cutting edge 51 is 10°-30°, and the range of the rear angle is 2°-5°.

In this embodiment, a cutting edge groove 54 is formed between any two adjacent margins 53; the groove depth of the cutting edge groove 54 is preferably 1-1.5 mm, and the groove width is preferably 1-1.5 mm.

In this embodiment, the width of any land 53 is preferably 1-1.5 mm.

Taking the non-damage sliding cutting of CFRP 1 as an example, the method and principle of using the CFRP low-damage hole-making drill bit in this embodiment will be further described.

During drilling, the feeding direction (or composite cutting direction) of the drill bit body 5 is perpendicular to the plane where any layer of layers in the CFRP 1 is located (CFRP has a multi-layer layer structure, and the layer structure is mostly a resin layer, The following fiber can be the carbon fiber with the CFRP inner layer laid between the two resin layers), and the way to realize sliding cutting is shown in Figure 8. The drill body 5 rotates downwards under the action of the main motion (shown in Figures 8 and 9) and the feed motion (shown in Figure 8) for cutting, as shown in Figure 8 is the position of the sliding cutting edge 51 on the drill body 5, the drill The movement trajectory of the main body 5 during one rotation cycle is shown in FIG. 9 , and the material cut by several sliding cutting edges 51 is gradually removed. As shown in Figure 10, it is a schematic partition diagram _of the drill bit structure 5. The drill bit diameter can be _6-12mm . The length ranges of the cutting zone C _z3 , the first cutting zone C _z1 , the second cutting zone C _z2 and the third cutting zone C _z3 are preferably 2-4 mm, 6-12 mm and 1-4 mm, respectively. The function of the first cutting zone C _z1 is exactly the same as that of the traditional drill bit, and there is no sliding cutting; the sliding cutting edge 51 is mainly concentrated in the second cutting zone C _z2 , and the aperture (diameter of the drilled hole) gradually increases under the action of the sliding cutting edge 51. Expand until the final hole diameter is reached. As shown in Figure 10, the scope of angle η wherein is in 2 °-5 °, drop h is calculated according to trigonometric function formula by the axial length of second cutting zone C _z2 and η; The rake angle γ _s of sliding cutting edge 51 The range is preferably 10°-30°, and the relief angle α is preferably in the range 2°-5°. In the second cutting zone _Cz2 and the third cutting zone _Cz3 , the width of the cutting edge groove 54 and the land 53 (that is, the length along the axial direction of the drill bit structure 5) can be preferably 1-1.5mm, and the cutting edge groove The depth of 54 (ie the length along the radial direction of the drill bit structure 5) may preferably be 1-1.5mm.

In this embodiment, the number of sliding cutting edges 51 in the second cutting zone _Cz2 is preferably set to 3-6, and the number of sliding cutting edges 51 in the third cutting zone _Cz3 is preferably set to 1-3.

It can be seen that the cutting drill structure designed by the present invention is based on the sliding cutting method. The drill body is divided into three cutting zones. hole. The second and third cutting areas adopt the form of ring grooves to prepare sliding cutting edges to ensure that the cutting edges and the fiber matrix will slide relative to each other under the main motion and feeding motion of the drill bit to achieve precise cutting; and multiple sliding cutting edges work together to gradually remove The material around the hole solves the problem of damage to the subsurface of the hole wall, which is conducive to improving the accuracy of the hole diameter.

It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. . Accordingly, the embodiments should be regarded in all points of view as exemplary and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and it is therefore intended that the scope of the invention be defined by the appended claims rather than by the foregoing description. All changes within the meaning and range of equivalents of the elements are embraced in the invention, and any reference sign in a claim shall not be construed as limiting the claim concerned.

In the present invention, specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only used to help understand the method and core idea of the present invention; meanwhile, for those of ordinary skill in the art, according to the present invention The idea of the invention will have changes in the specific implementation and scope of application. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims (7)

1. A CFRP low-damage drilling bit, is characterized in that, comprising: Drill body, the end of the drill body is equipped with a tip structure, the tip structure is used to provide extrusion force along the direction of drilling feed; the drill body is sequentially provided with a first cutting zone, a second cutting zone and a third cutting zone; Sliding cutting edge, the sliding cutting edge is arranged on the outer wall of the drill body, and a plurality of sliding cutting edges are arranged at intervals along the axial direction of the drill body; Sliding shear force in the tangential direction of the cutting edge; The secondary edge of the drill, the secondary edge of the drill is arranged at intervals along the axial direction of the drill body, and any one of the secondary edges of the drill is connected with one of the sliding cutting edges to form a margin; the secondary edge of the drill is used for It is used to remove the fiber and matrix of the hole wall during the drilling process; The sliding cutting edge is arranged in the second cutting zone and the third cutting zone, and the first cutting zone is only provided with the drill chisel edge, the main cutting edge and the drill secondary edge. 2. The CFRP low-damage hole-making drill according to claim 1, wherein the diameter of the drill body increases gradually along the opposite direction of the drilling feed. 3. The CFRP low-damage hole-making drill according to claim 1, wherein the rake angle of any of the sliding cutting edges ranges from 10° to 30°, and the rear angle ranges from 2° to 5°. 4. CFRP low-damage drilling drill according to claim 1, is characterized in that, a cutting groove is formed between any adjacent two described margins; the groove depth of the cutting groove is 1 ~ 1.5mm, and the groove width is 1~1.5mm. 5. The CFRP low-damage hole-making drill according to claim 1, wherein the width of any of the margins is 1-1.5 mm. 6. The CFRP low-damage hole-making drill bit according to claim 1, wherein any of the sliding cutting edges are located in a plane perpendicular to the axial direction of the drill bit. 7. A CFRP low-damage sliding cutting method, implemented by using the CFRP low-damage drilling drill described in any one of claims 1 to 6, characterized in that, comprising: In addition to moving along the composite cutting direction, any point on the cutting edge also slides along the direction tangent to the point of the cutting edge, so as to complete the CFRP cutting under the extrusion action of the tip and the sliding shearing action of the cutting edge machining; wherein any point on the cutting edge has: Speed vs ₁ along the cutting direction resulting from the main motion and feed motion; Sliding cutting speed vs ₂ in the direction tangential to the cutting edge.