Stepped drilling tool suitable for processing carbon fiber composite material

Abstract

The invention discloses a stepped drilling tool suitable for processing a carbon fiber composite material, and relates to the technical field of drilling tools, the stepped drilling tool comprises a tool main body, the tool main body is divided into a primary drilling area, a fine expanding area and a clamping area from bottom to top, a hollow groove is formed in the primary drilling area, and the primary drilling area is divided into three zigzag pilot cutting edges at equal intervals; a spiral first chip groove is formed between the pilot cutting edges and is communicated with the hollow groove; the outer diameter of the fine reaming area is larger than that of the initial drilling area, and the transition joint of the fine reaming area and the initial drilling area is a conical reaming conical surface; four spiral second chip grooves are formed in the outer wall of the fine expanding area at equal intervals, the spiral angles of the second chip grooves are smaller than those of the first chip grooves, and fine expanding cutting edges are arranged at the lower ends of the second chip grooves; the front angle of the fine reaming cutting edge is larger than that of the pilot cutting edge; the vertex angle of the fine reaming area is smaller than that of the initial drilling area; according to the cutter, the whole drilling process is completed in stages, and the problems that an existing cutter is not high in drilling precision and short in service life are solved.

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, comprising a tool body, the tool body is divided into a preliminary drilling area, a fine expansion area and a clamping area from bottom to top, a hollow groove extending to the fine expansion area is opened in the preliminary drilling 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 grooves are evenly spaced on the outer wall of the fine expansion zone, the helix angle of the second chip groove is smaller than the helix angle of the first chip groove, and the spiral directions of the two are consistent; the lower end of the second chip groove is 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 top angle of the fine expansion zone is smaller than the top angle of the initial drilling zone.

[0007] Preferably, the pilot cutting edge and the finishing cutting edge both adopt a circular arc back angle design, and 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 curved surface connected to the first chip groove, the cylindrical surface of the hollow groove, and the plane generated during grinding.

[0008] Preferably, 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°.

[0009] Preferably, the first chip flute helix angle β 1 =38°-46°, the second chip flute helix angle β 2 =26°-35°.

[0010] Preferably, the top angle of the initial drilling area is 60°, and the top angle of the fine expansion area is 40°.

[0011] Compared with the prior art, the present invention has the following advantages: This tool eliminates the chisel edge on the basis of the traditional twist drill and uses three pilot cutting edges in the initial drilling area instead, avoiding the problem that the chisel edge will cause an increase in axial force; This tool is a stepped drilling tool. The initial drilling area and the fine expansion area work successively, so that the entire drilling process is completed in stages, which reduces the pressure on the workpiece and the tool during the drilling process and solves the problem of short tool life. The tool achieves effective control of CFRP machining damage by rationally configuring the geometric parameters of the two stages, avoids significant machining defects in the final hole, and solves the problem of low drilling accuracy of existing tools. This tool not only significantly improves the processing quality and efficiency of CFRP drilling, but also helps related companies reduce hole-making costs. It has broad market application prospects and significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A perspective view of the present invention; Figure 2 It is a front view of the present invention; Figure 3 is a cross-sectional view of the pilot cutting edge; Figure 4 This is a cross-sectional view of the precision-expanded cutting edge; Figure 5 This is a three-dimensional picture of the initial drilling area; Figure 6 A cross-sectional view of the present invention as a whole; Figure 7 Schematic diagram of the blade tip grinding angle in the initial drilling area.

[0013] In the figure: A, initial drilling area, B, fine expansion area, C, clamping area, 1, hollow groove, 2, pilot cutting edge, 3, first chip groove, 4, expansion cone surface, 5, second chip groove, 6, fine expansion cutting edge. DETAILED DESCRIPTION

[0014] The present invention is further described below with reference to the accompanying drawings and embodiments. Embodiment 1

[0015] Reference Figure 1-7 As shown, a stepped drilling tool suitable for processing carbon fiber composite materials includes a tool body, which is divided into an initial drilling area A, a fine expansion area B and a clamping area C from bottom to top. A hollow groove 1 extending to the fine expansion area B is opened in the initial drilling area A, and the depth of the hollow groove 1 is L 0 The thickness of the carbon fiber composite material sheet to be processed can be changed; the initial drilling area A is divided into three serrated pilot cutting edges 2 at equal intervals, and between the pilot cutting edges 2 is a spiral first chip groove 3, which is connected to the hollow groove 1.

[0016] The pilot cutting edge 2 adopts a circular back angle design. The tip of the pilot cutting edge 2 consists of three curved surfaces and one plane, namely the conical surface where the vertex is located, the curved surface connected to the first chip groove 3, the cylindrical surface of the hollow groove 1, and the plane generated during grinding. The three pilot cutting edges 2 work together to efficiently cut 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 allows the plate to remain in the hollow groove 1 area after drilling through the material. The plate remaining in the hollow groove 1 loses its rotational power, thereby reducing the relative speed with the tool, effectively alleviating the problem of heat accumulation and solving the problem of thermal damage in CFRP processing.

[0017] More detailed, the leading cutting edge 2 rake angle γ A =15°-21° (preferably 18°), back angle α A =12°-16° (preferably 12°), its tip grinding angle Ω=9°-13° (preferably 9°); the first chip groove 3 helix angle β 1 =38°-46° (preferably 46°), 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 mounted by welding or bonding.

[0018] The outer diameter of the fine expansion area B is larger than that of the initial drilling area A, and the transitional connection between the two is a conical expansion cone surface 4; four spiral second chip grooves 5 are evenly spaced on the outer wall of the fine expansion area B, and the helix angle of the second chip groove 5 is smaller than that of the first chip groove 3, and the spiral directions of the two are consistent; the lower end of the second chip groove 5 is provided with a fine expansion cutting edge 6, and the fine expansion cutting edge 6 also adopts a circular arc back angle design, and its front angle is larger than the front angle of the pilot cutting edge 2; the top angle of the fine expansion area B is smaller than the top angle of the initial drilling area A. More specifically, the front angle γ of the fine expansion cutting edge 6 B =25°-29° (preferably 25°), back angle α B =16°-20° (preferably 16°); helix angle of second chip flute 5 β 2 =26°-35° (preferably 26°), the top angle of the fine expansion zone B is 40° (half top angle P 2 =20°). In addition, the fine-expanded cutting edge 6 is coated with diamond (thickness 2-5 μm).

[0019] Five key parameters of the fine expansion area B were optimized relative to the initial drilling area A: 1. Increasing the number of cutting edges to improve cutting performance; 2. Reducing the helix angle of the chip groove to improve cutting accuracy; 3. Increasing the rake angle of the cutting edge to reduce cutting resistance; 4. Enlarging the diameter size to ensure complete removal of the machining damage caused by the initial drilling area A; 5. Reducing the top angle design to reduce axial force and inhibit delamination damage. These optimized designs enable the fine expansion area B to effectively remove the burrs and tearing damage caused by the initial drilling area A, and significantly improve the hole wall quality through progressive machining. In particular, the smaller top angle design effectively reduces the axial force. As the drilling depth increases, the fine expansion area B can gradually remove the delamination damage caused by the initial drilling area A, achieving continuous improvement in machining quality.

[0020] In terms of chip removal system design, since the initial drilling area A is a rough processing area with a large processing volume, it is necessary to increase the helix angle to improve the chip removal capacity; the initial drilling area A adopts a large helix angle chip removal groove design to ensure efficient chip removal and effectively avoid the problem of scratches on the processing surface caused by chip accumulation. The fine expansion area B is a fine processing area, so the processing volume of the fine expansion area B is smaller than that of the initial drilling area A, and the chips processed will not be too many, so the chip removal effect does not need to be too good. At the same time, reducing the helix angle of the chip removal groove can improve the rigidity of the tool, thereby improving the processing accuracy, which meets the requirements of fine processing; the fine expansion area B adopts a chip removal groove design with a relatively small helix angle, which ensures the chip removal effect while maintaining the processing accuracy to the maximum extent. This innovative structural design not only significantly improves the processing efficiency, but also ensures the processing quality. It is particularly suitable for high-precision hole processing of difficult-to-process materials such as CFRP.

[0021] In summary, based on the traditional twist drill, the tool eliminates the transverse edge and adopts three leading cutting edges 2 in the initial drilling area A instead, thus avoiding the problem that the transverse edge will cause the axial force to increase; the tool is a stepped drilling tool, and the initial drilling area A and the fine expansion area B work successively, so that the whole drilling process is completed in stages, which reduces the pressure of the drilling process on the workpiece and the tool and solves the problem of short tool life; the tool realizes effective control of CFRP processing damage by reasonably configuring the geometric parameters of the two stages, avoids significant processing defects in the final hole, and solves the problem of low drilling accuracy of existing tools; the tool not only significantly improves the processing quality and efficiency of CFRP drilling, but also helps related companies reduce hole making costs, and has broad market application prospects and significant economic benefits.

[0022] The present invention is not limited to the above-mentioned embodiments. Various changes can be made within the knowledge scope of those skilled in the art without departing from the spirit of the present invention. The changed contents still fall within 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 grooves are evenly spaced on the outer wall of the fine expansion zone, the helix angle of the second chip groove is smaller than the helix angle of the first chip groove, and the spiral directions of the two are consistent; the lower end of the second chip groove is 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 top angle of the fine expansion zone is smaller than the top angle of the initial drilling zone.

2. A stepped drilling tool suitable for machining carbon fiber composite materials according to claim 1, characterized in that: 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, a conical surface where the vertex is located, a curved surface connected to the first chip removal groove, a cylindrical surface of the hollow groove, and a plane generated during grinding.

3. A stepped drilling tool suitable for machining carbon fiber composite materials according to claim 2, 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°.

4. 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°.

5. 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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