METHOD FOR MACHINING DRILL WITH TILTING BLADE SLOT STRUCTURES FOR COMPOSITE MACHINING

Abstract

A method for machining a drill with tilting blade slot structures for composite machining is provided. In the machining method, a face of the drill produces a downward component force for the inlet material to inhibit the inlet material from turning up; and a cutting edge inclination of an end surface at an outer turning point in a corner region of the drill is a positive value. The face and a flank are firstly partially ground in the corner region of the drill. The face at the outer turning point is ground with a grinding wheel to obtain two tilting blade slot structures. After grinding, a new face and a new cutting edge are obtained; and the cutting edge inclination on the end surface formed by the new cutting edge and a reference plane is a positive angle.

Claims

1. A method for machining a drill with tilting blade slot structures for composite machining, comprising the following steps: firstly, grinding a drill with the following features by using a hard alloy bar: grinding to ensure that the width W.sub.1 of a chip space in a minor cutting edge region B is 0.8-0.9 time of the drilling diameter d.sub.2 of a tool, wherein an angle formed by the chip space (3) and a tool axis (1), i.e., a helix angle n.sub.1 of the chip space, is 30°-45°; then, partially grinding a face and a flank of the drill to reduce the friction between the tool and the material and achieve a good heat dissipation effect; grinding the face (9) near a chisel edge at a corner region (C) to obtain a ground face (10), wherein a rake angle n.sub.5 is ground as 10°-20° herein; partially grinding the flank (5) to obtain a ground flank (6), wherein a clearance angle n.sub.6 is 10°-20°; finally, machining tilting blade slot structures (D) in the corner region (C), i.e., grinding the face (9) herein with a grinding wheel at an outer turning point (11) of a major cutting edge (7) of the corner region (C), to obtain two tilting blade slot structures (D); grinding to obtain a new face (8) and a new cutting edge (12), wherein a cutting edge inclination n.sub.7 on an end surface formed by the new cutting edge (12) and a reference plane (13) is a positive angle, i.e., 20°-35°; a tilting blade slot angle n.sub.8 formed on the end surface by the tilting blade slot structures (D) is 80°-100°, and the length L.sub.3 of the new cutting edge (12) is 0.9-1.2 mm; a rake angle n.sub.4 at a machined tilting blade slot on the outer turning point (11) is a negative angle, i.e., 0° to 15°; the clearance angle n.sub.3 at the tilting blade slot is unchanged, and the clearance angle n.sub.3 at the tilting blade slot is the same as the clearance angle n.sub.6, i.e., 10°-20°.

Description

DESCRIPTION OF DRAWINGS

[0012] FIG. 1 is a main view of a drill with tilting blade slot structures for composite machining.

[0013] FIG. 2 is an enlarged view of a corner region of FIG. 1.

[0014] FIG. 3 is an enlarged view of K direction of FIG. 1.

[0015] FIG. 4 is an inlet hole for machining a fiber reinforced plastic by the drill.

[0016] FIG. 5 is an outlet hole for machining a fiber reinforced plastic by the drill.

[0017] In the figures: A shank region; B minor cutting edge region; C corner region; D tilting blade slot structure;

[0018] 1 tool axis; 2 land; 3 chip space; 4 minor cutting edge; 5 flank; 6 ground flank; 7 major cutting edge; 8 new face; 9 face; 10 ground face; 11 outer turning point; 12 new cutting edge; 13 reference plane;

[0019] W.sub.1 width of chip space; W.sub.2 land width;

[0020] n.sub.1 chip space helix angle; n.sub.2 angle between major cutting edge and tool axis; n.sub.3 clearance angle at tilting blade slot; n.sub.4 rake angle at tilting blade slot; n.sub.5 ground rake angle; n.sub.6 clearance angle; n.sub.7 cutting edge inclination on end surface; n.sub.8 tilting blade slot angle;

[0021] L.sub.1 clamping length; L.sub.2 cutting edge length; L.sub.3 new cutting edge length; L.sub.4 chisel edge length;

[0022] d.sub.1 clamping diameter; d.sub.2 drilling diameter.

DETAILED DESCRIPTION

[0023] Detailed description of the present invention is described below in detail in combination with accompanying drawings and the technical solution.

[0024] As shown in FIG. 1, FIG. 2 and FIG. 3, a drill with tilting blade slot structures in the present invention is composed of three parts: a shank region A of a tool clamping part, a minor cutting edge region B of a drill body part and a corner region C of a main cutting part of drilling. The minor cutting edge region B of the drill has two chip spaces 3 and two lands 2; the lands 2 have minor cutting edges 4; the width W.sub.1 of the chip spaces is 0.8-0.9 time of the diameter d.sub.2 of the tool; land width W.sub.2 is 2.5-3.4 mm; and an angle n.sub.1 formed by the chip spaces 3 and a tool axis 1 is 30°-45°. The tool diameter d.sub.2 and cutting edge length L.sub.2 can be set according to the diameter and depth of a drilling hole; and the length L.sub.1 of the tool clamping part can also be set according to the diameter of the drill, which is generally 30-50 mm. The clamping diameter d.sub.1 is generally Φ4 mm, Φ6 mm, Φ8 mm, etc.

[0025] In the present embodiment, firstly, a drill is ground to an original drill with the following features by using a hard alloy bar: grinding to ensure that the width W.sub.1 of the chip spaces in the minor cutting edge region B is 0.8-0.9 time of the tool diameter d.sub.2; d.sub.2 is 8 mm; W.sub.1 is 7.2 mm; and the angle n.sub.1 formed by the chip spaces 3 and the tool axis 1 is 30°. The thickness of a web is one-third of the tool drilling diameter d.sub.2. Proper thickness of the web and margin width can reduce the friction between the tool and the material, smoothly discharge the chips, and ensure that the tool rigidity meets the machining requirements. The length L.sub.1 of the tool clamping part can also be set according to the diameter of the drill, and is 50 mm; the clamping diameter d.sub.1 is a standard size of Φ8 mm; an angle n.sub.2 formed by a major cutting edge 7 and the tool axis is 59°; and the land width W.sub.2 is 2.5 mm.

[0026] Then, a face and a flank of the drill are partially ground to reduce the friction between the tool and the material and achieve a good heat dissipation effect. The face 9 near a chisel edge at the corner region C is ground to obtain a ground face 10, and a rake angle n.sub.5 is ground as 10° herein; the flank 5 is partially ground to obtain a ground flank 6, and a clearance angle n.sub.6 is 10°; chisel edge length L.sub.4 ground at the drill tip is 0.4 mm; and a short chisel edge can reduce the axial drilling force and reduce the delamination damage at the outlet.

[0027] Finally, tilting blade slot structures (D) are ground in the corner region (C) at the outermost circle of the major cutting edge 7 of the tool; and the face 9 herein is ground with a grinding wheel to obtain two tilting blade slot structures D. Meanwhile, after grinding, a new face 8 and a new cutting edge 12 are obtained; a rake angle n.sub.4 at the formed tilting blade slot is a negative angle, i.e., −15°; and the face produces a downward component force for the inlet material before drilling to inhibit the inlet material from turning up. Observing from the bottom, two edges of the tilting blade slot form a right angle n.sub.8 of the tilting blade slot; the cutting edge inclination n.sub.7 on the outer turning point of the drill is positive, i.e., 20°; and the length L.sub.3 of the new cutting edge is 1.2 mm to ensure that the depth of the tilting blade slot is not greater than the ground flank.

[0028] The tilting blade slot structure has the main functions of changing the drilling cutting edge inclination n.sub.7 at the outer turning point 11 to a positive value, making the corner and outer turning point 11 sharper, ensuring that the horizontal flow direction of the chips at the outer turning point is inward along the radial direction of the drill, generating no radial outward component for the fiber material on the edge of the hole, and effectively reducing the tear damage at the edge of the hole inlet.

[0029] An experimental platform uses a five-axis high precision machining center, and the drill is made of carbide without coating. Dry cutting is adopted without cooling. The spindle speed is 6000 rpm, the feed speed is 400 mm/min, and drilling is performed for three times. A machining workpiece is a fiber reinforced plastic laminate from Boeing with a thickness of 5 mm. The machining workpiece is used for the manufacture of Boeing aircraft, is easy to produce inlet burr during machining, is very representative and challenging, and can also embody the practicality of the present invention. FIG. 4 and FIG. 5 respectively show the quality of the inlet hole and the outlet hole machined by the drill. When the inlet surface and the outlet surface are carefully observed, the inlets of three machined holes have no burr and tear damage, and the quality is very good. When the first hole is machined, the outlet has no delamination and burr damage, and the quality is very good. When the third hole is machined, the outlet is still very good and has no delamination and burr damage. It can be seen that on the premise of ensuring the quality of the hole outlet, the drill can effectively inhibit the inlet damage during hole making of the composite and has good machining quality; and the tool has long service life.

[0030] The drill with tilting blade slot structures machined by the present invention can make the cutting edge inclination on the end surface of the outermost circle of the major cutting edge as a positive value, changes the cutting state of the fiber of the drilling inlet, inhibits the weakly constrained inlet surface material from spontaneously turning up, and reduces the tear damage at the inlet. The tilting blade slot structures make the outer turning point of the tool sharper, which is beneficial for cutting the fiber and reducing the burr damage at the inlet. Finally, high-quality and high-efficiency hole making for the fiber composite is realized.

[0031] The method for machining the drill with tilting blade slot structures for composite machining in the present invention is not limited to the structures of the above embodiments, and can be varied in many forms. In conclusion, all improvements without departing from the innovation scope of the patent of the present invention fall within the protection scope of the patent of the present invention.