A stepped drilling tool applicable to the processing of carbon fiber composite materials

Abstract

The present invention discloses a stepped drilling tool suitable for the processing of carbon fiber composite materials, which relates to the technical field of drilling tools. The tool body includes a tool body, which is divided into a primary drilling area, a finishing and enlarging area, and a clamping area from bottom to top. A hollow groove is provided in the primary drilling area, and the primary drilling area is equally spaced into three serrated pilot cutting edges; between the pilot cutting edges is a spiral first chip evacuation groove, and the first chip evacuation groove communicates with the hollow groove; the outer diameter of the finishing and enlarging area is larger than that of the primary drilling area, and the transition connection between the two is a conical reaming cone surface; four spiral second chip evacuation grooves are equally spaced on the outer wall of the finishing and enlarging area, and the spiral angle of the second chip evacuation groove is smaller than that of the first chip evacuation groove, and finishing and reaming cutting edges are provided at their lower ends; the rake angle of the finishing and reaming cutting edge is larger than that of the pilot cutting edge, and the apex angle of the finishing and enlarging area is smaller than that of the primary drilling area; this tool enables the entire drilling process to be completed in stages, solving the problems of low drilling accuracy and short tool life of existing tools.

Description

Technical Field

[0001] The invention relates to the technical field of drilling tools, and in particular to a stepped drilling tool suitable for machining carbon fiber composite materials. Background Art

[0002] Carbon fiber reinforced resin composites (CFRP) have been widely used in aerospace, rail transportation and other fields due to their high specific strength, excellent fatigue resistance and designability. However, the low interlaminar strength and significant anisotropy of CFRP make it very easy to produce defects such as delamination damage, hole wall tearing and exit burrs during drilling. Statistics show that the scrap rate of CFRP components caused by delamination defects is as high as 60%, which seriously restricts the demand for high-precision assembly.

[0003] Most existing drilling tools follow the traditional metal processing tool structure, which has significant limitations: most traditional tools have chisel edges, which are generally considered to be the main cause of increased axial force; and most traditional tools have a single overall structure and cannot repair damage caused during processing. In addition, the differentiated thermal conductivity of CFRP and metal materials makes it difficult to effectively dissipate cutting heat, accelerates tool wear and induces thermal degradation of the resin matrix. The paper "Novel drill structure for damage reduction in drilling CFRP composites" points out that the axial thrust generated by the drilling tool is an important cause of delamination, and when the axial thrust is greater than the critical thrust, the resulting delamination damage will be uncontrollable.

[0004] Although there have been improved designs such as step drills and multi-edge drills in recent years, there are still problems such as delamination due to inappropriate chisel edge parameters, low drilling accuracy due to inappropriate tool structure and various parameters, and short tool life and low cutting efficiency due to the single existing tool structure and drilling method that cannot adapt to new materials. Therefore, how to innovate tool structure and drilling principles to achieve low-damage CFRP processing has become a technical bottleneck that needs to be broken through in the field of advanced manufacturing. Summary of the invention

[0005] The purpose of the present invention is to provide a stepped drilling tool suitable for machining carbon fiber composite materials in view of the defects in the prior art.

[0006] The technical solution of the present invention is: a stepped drilling tool suitable for processing carbon fiber composite materials, including a tool body. The tool body is divided into a primary drilling area, a finishing and enlarging area, and a clamping area from bottom to top. A hollow groove extending to the finishing and enlarging area is provided in the primary drilling area, and the primary drilling area is equally divided into three serrated pilot cutting edges at equal intervals; a spiral first chip removal groove is arranged between the pilot cutting edges, and the first chip removal groove is communicated with the hollow groove;

[0007] The outer diameter of the finishing and enlarging area is larger than that of the primary drilling area, and the transition connection between the two is a conical reaming cone surface; four spiral second chip removal grooves are equally spaced on the outer wall of the finishing and enlarging area. The spiral angle of the second chip removal groove is smaller than that of the first chip removal groove, and their spiral directions are the same; finishing and enlarging cutting edges are provided at the lower ends of the second chip removal grooves. The rake angle of the finishing and enlarging cutting edge is larger than that of the pilot cutting edge, and the apex angle of the finishing and enlarging area is smaller than that of the primary drilling area.

[0008] Preferably, both the pilot cutting edge and the finishing and enlarging cutting edge adopt an arc flank angle design. The tip of the pilot cutting edge is composed of three curved surfaces and a flat surface, namely the conical surface where the apex angle is located, the curved surface connected to the first chip removal groove, the cylindrical surface of the hollow groove, and the flat surface generated during grinding.

[0009] Preferably, the rake angle γ of the pilot cutting edge A = 15° - 21°, the flank angle α A = 12° - 16°, and the tip grinding angle Ω = 9° - 13°; the rake angle γ of the finishing and enlarging cutting edge B = 25° - 29°, the flank angle α B = 16° - 20°.

[0010] Preferably, the spiral angle β of the first chip removal groove 1 = 38° - 46°, and the spiral angle β of the second chip removal groove 2 = 26° - 35°.

[0011] Preferably, the apex angle of the primary drilling area is 60°, and the apex angle of the finishing and enlarging area is 40°.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] In this tool, the web is cancelled on the basis of the traditional twist drill and replaced by three pilot cutting edges in the primary drilling area, avoiding the problem that the web will cause an increase in axial force;

[0014] This tool is a stepped drilling tool. The primary drilling area and the finishing and enlarging area work successively, making the whole drilling process completed in stages, reducing the pressure on the workpiece and the tool during the drilling process, and solving the problem of short tool life;

[0015] By reasonably configuring the geometric parameters in two stages, this cutting tool effectively controls the machining damage of CFRP, avoids significant machining defects in the final hole, and solves the problem of low drilling accuracy of existing cutting tools.

[0016] This cutting tool not only significantly improves the machining quality and efficiency of CFRP drilling, but also helps related enterprises reduce the hole-making cost, with broad market application prospects and significant economic benefits. Brief Description of the Drawings

[0017] Figure 1 is a perspective view of the present invention;

[0018] Figure 2 is a front view of the present invention;

[0019] Figure 3 is a cross-sectional view of the pilot cutting edge;

[0020] Figure 4 is a cross-sectional view of the finishing reaming cutting edge;

[0021] Figure 5 is a perspective view of the initial drilling area;

[0022] Figure 6 is a cross-sectional view of the whole of the present invention;

[0023] Figure 7 is a schematic diagram of the edge tip grinding angle of the initial drilling area.

[0024] In the figure: A, initial drilling area; B, finishing reaming area; C, clamping area; 1, hollow groove; 2, pilot cutting edge; 3, first chip removal groove; 4, reaming conical surface; 5, second chip removal groove; 6, finishing reaming cutting edge. Detailed Embodiments

[0025] The following further describes the present invention in conjunction with the drawings and embodiments. Embodiment 1

[0026] Referring to Figure 1-7 as shown, a stepped drilling tool suitable for machining carbon fiber composite materials includes a tool body. The tool body is divided into an initial drilling area A, a finishing reaming area B, and a clamping area C from bottom to top. A hollow groove 1 extending to the finishing reaming area B is provided in the initial drilling area A, and the depth L of the hollow groove 1 0 can be changed according to the thickness of the carbon fiber composite material plate to be machined; the initial drilling area A is equally divided into three serrated pilot cutting edges 2 at equal intervals. The first chip removal groove 3 in a spiral shape is between the pilot cutting edges 2, and the first chip removal groove 3 communicates with the hollow groove 1.

[0027] The leading cutting edge 2 adopts a design with a circular arc flank angle. The tip of the leading cutting edge 2 is composed of three curved surfaces and a flat surface, namely the conical surface where the vertex angle is located, the curved surface connected to the first chip groove 3, the cylindrical surface of the hollow groove 1, and the flat surface generated during grinding. The three leading cutting edges 2 cooperate with each other to efficiently cut off the carbon fiber bundles in the CFRP, and its drilling efficiency is significantly better than that of traditional hollow drills. The unique hollow structure design can make the plate remain in the area of the hollow groove 1 after drilling through the material. The plate remaining in the hollow groove 1 loses the rotational power, thereby reducing the relative rotational speed with the tool and effectively alleviating the problem of heat accumulation, and solving the problem of thermal damage in CFRP processing.

[0028] More specifically, the rake angle γ of the leading cutting edge 2 A = 15° - 21° (preferably 18°), the flank angle α A = 12° - 16° (preferably 12°), and the tip grinding angle Ω = 9° - 13° (preferably 9°); the helix angle β of the first chip groove 3 1 = 38° - 46° (preferably 46°), and the vertex angle of the initial drilling area A is 60° (half vertex angle P 1 = 30°). In addition, the main cutting part of the leading cutting edge 2 is made of diamond material to ensure wear resistance and cutting efficiency, and is inlaid by means of connection such as welding or bonding.

[0029] The outer diameter of the fine reaming area B is larger than that of the initial drilling area A, and the transition connection between the two is a conical reaming cone surface 4; four spiral second chip grooves 5 are equally spaced on the outer wall of the fine reaming area B, and the helix angle of the second chip groove 5 is smaller than that of the first chip groove 3, and their spiral directions are the same; fine reaming cutting edges 6 are provided at the lower ends of the second chip grooves 5, and the fine reaming cutting edges 6 also adopt a design with a circular arc flank angle, and its rake angle is larger than that of the leading cutting edge 2. The vertex angle of the fine reaming area B is smaller than that of the initial drilling area A. More specifically, the rake angle γ of the fine reaming cutting edge 6 B = 25° - 29° (preferably 25°), the flank angle α B = 16° - 20° (preferably 16°); the helix angle β of the second chip groove 5 2 = 26° - 35° (preferably 26°), and the vertex angle of the fine reaming area B is 40° (half vertex angle P 2 = 20°). In addition, the fine reaming cutting edge 6 is coated with diamond (thickness 2 - 5 μm).

[0030] Five key parameters of the fine expansion area B are optimized relative to the initial drilling area A: 1. Increase the number of cutting edges to improve cutting performance; 2. Reduce the helix angle of the chip flute to improve cutting accuracy performance; 3. Increase the rake angle of the cutting edge to reduce cutting resistance; 4. Enlarge the diameter size to ensure complete removal of the machining damage generated in the initial drilling area A; 5. Reduce the point angle design to reduce the axial force and suppress delamination damage. These optimized designs enable the fine expansion area B to effectively remove the burrs and tear damage generated in the initial drilling area A, and significantly improve the hole wall quality through progressive machining. In particular, the smaller point angle design effectively reduces the axial force. As the drilling depth increases, the fine expansion area B can gradually remove the delamination damage generated in the initial drilling area A, achieving continuous improvement of the machining quality.

[0031] In terms of the chip evacuation system design, since the initial drilling area A is a rough machining area with a large machining volume, it is necessary to increase the helix angle to improve the chip evacuation ability; the initial drilling area A adopts a chip flute design with a large helix angle to ensure efficient chip evacuation and effectively avoid the problem of machining surface scratches caused by chip accumulation. The fine expansion area B is a finishing area, so the machining volume of the fine expansion area B is smaller than that of the initial drilling area A, and the chips produced will not be too much. Therefore, the chip evacuation effect does not need to be too good. At the same time, after reducing the helix angle of the chip flute, the stiffness of the tool can be improved, thereby improving the machining accuracy, which exactly meets the requirements of finishing; the fine expansion area B adopts a chip flute design with a relatively small helix angle, which maximally maintains the machining accuracy while ensuring the chip evacuation effect. This innovative structural design not only significantly improves the machining efficiency but also ensures the machining quality, and is particularly suitable for high-precision hole machining of difficult-to-machine materials such as CFRP.

[0032] In summary, this tool cancels the web on the basis of the traditional twist drill and uses three pilot cutting edges 2 in the initial drilling area A to replace it, avoiding the problem of increased axial force caused by the web; this tool is a stepped drilling tool, and the initial drilling area A and the fine expansion area B work successively, making the entire drilling process completed in stages, reducing the pressure on the workpiece and the tool during the drilling process, and solving the problem of short tool life; this tool effectively controls the machining damage to CFRP by reasonably configuring the geometric parameters of the two stages, avoiding significant machining defects in the final hole, and solving the problem of low drilling accuracy of existing tools; this tool not only significantly improves the machining quality and efficiency of CFRP drilling, but also helps related enterprises reduce the hole-making cost, and has broad market application prospects and significant economic benefits.

[0033] The present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the gist of the present invention, and the changed content still belongs to the protection scope of the present invention.

Claims

1. A stepped drilling tool suitable for machining carbon fiber composite materials, comprising a tool body, characterized in that: The tool body is divided into a preliminary drilling area, a fine expansion area and a clamping area from bottom to top, the preliminary drilling area is provided with a hollow groove that can extend to the fine expansion area, and the preliminary drilling area is divided into three serrated pilot cutting edges at equal intervals; between the pilot cutting edges is a spiral first chip removal groove, and the first chip removal groove is connected to the hollow groove; The outer diameter of the fine expansion zone is larger than the outer diameter of the initial drilling zone, and the transition connection between the two is a conical expansion cone surface; four spiral second chip removal grooves are evenly spaced on the outer wall of the fine expansion zone, the helix angle of the second chip removal groove is smaller than the helix angle of the first chip removal groove, and the spiral directions of the two are consistent; the lower ends of the second chip removal grooves are each provided with a fine expansion cutting edge, the front angle of the fine expansion cutting edge is larger than the front angle of the pilot cutting edge, and the vertex angle of the fine expansion zone is smaller than the vertex angle of the initial drilling zone; The pilot cutting edge and the fine expansion cutting edge both adopt a circular arc back angle design. The tip of the pilot cutting edge consists of three curved surfaces and one plane, namely the conical surface where the vertex angle is located, the front cutting surface connected to the first chip removal groove, the cylindrical surface of the hollow groove, and the plane generated during grinding.

2. A stepped drilling tool suitable for machining carbon fiber composite materials according to claim 1, characterized in that: The leading cutting edge rake angle γ A =15°-21°, back angle α A =12°-16°, its blade tip grinding angle Ω=9°-13°; the precision cutting edge rake angle γ B =25°-29°, back angle α B =16°-20°.

3. The stepped drilling tool suitable for machining carbon fiber composite materials according to claim 1, characterized in that: The first chip removal groove helix angle β1=38°-46°, and the second chip removal groove helix angle β2=26°-35°.

4. The stepped drilling tool suitable for machining carbon fiber composite materials according to claim 1, characterized in that: The top angle of the initial drilling area is 60°, and the top angle of the fine expansion area is 40°.

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