VERTICAL-EDGE DOUBLE-STEP SAWTOOTH CUTTER FOR PREPARING HIGH-QUALITY HOLES OF COMPOSITE MATERIAL AND HYBRID STACK STRUCTURE THEREOF

Abstract

A vertical-edge double-step sawtooth cutter for preparing high-quality holes of composite material and thereof hybrid stack structure, and has three parts which are a major cutting edge region A, a minor cutting edge region B and a shank region C. The minor cutting edge region B comprises a step vertical-edge region D and a sawtooth cutting region E. This has the step structure and the sawtooth structure which is distributed in the first step, has a recutting function at the inlet and a reverse cutting function at the outlet in the direction opposite to the main cutting motion. The cutter has the vertical edge structure distributed in the second step, and the angle of the second step is a negative value, thereby realizing chip breaking and crushing, reducing scratch to the upper-layer composite material and metal hole walls.

Claims

1. A vertical-edge double-step sawtooth cutter for preparing high-quality holes of composite material and hybrid stack structure thereof, comprising three parts which are a major cutting edge region, a minor cutting edge region and a shank region, wherein the minor cutting edge region comprises a step vertical-edge region and a sawtooth cutting region; a major cutting edge of the major cutting edge region partially thins an initial cutting face to obtain a second cutting face; the initial cutting face and the second cutting face form a double-vertex angle structure, wherein a first vertex angle n.sub.1 is 100 to 106 and a second vertex angle n.sub.2 is 90 to 95; a double-step structure is distributed on the minor cutting edge region; a first step is near a point side and a second step is near a shank side; the minor cutting edge region has two chip grooves and forms two minor cutting edges; a helix rake angle .sub.1 of the minor cutting edges is 14 to 16; the width c of the chip grooves is 0.6-0.8 time of a first step diameter d of the cutter; margin width a of a vertical chip breaking edge and margin width b of the minor cutting edges are 1-1.5 mm, and the margin width a of the vertical chip breaking edge is larger than the margin width b of the minor cutting edges; the step vertical-edge region adopts a double-step negative-step angle structure, and an included angle n.sub.3 between a second step major cutting edge and a cutter axis is larger than 90; a vertical chip breaking edge is thinned on each minor cutting edge; the axial length e of the vertical chip breaking edge is at least 2 times of feed per tooth of the cutter; a helix rake angle .sub.2 of the vertical chip breaking edge is 13 to 15; the sawtooth cutting region is located between the step vertical-edge region and the major cutting edge region and is composed of a plurality of sawteeth and tooth spaces which are distributed on a drill cutting edge; the sawteeth and the tooth spaces are spiral around a drill axis; a helix angle of the sawtooth is an acute angle larger than 60; upper edges of the sawtooth are used as the cutting edges, and the upper edges of the sawteeth are thinned to form a rake angle; the width W.sub.g of the tooth spaces of the sawteeth is not less than the thickness of two layers of prepreg of processed fiber-reinforced material and is at least 0.3 mm; the tooth width W.sub.t of the sawteeth is at least 0.5 mm; the depth D.sub.t of the tooth spaces is at least 0.8 mm; and the sum of twice the depth D.sub.t of the tooth spaces and the thickness of a drill core is less than the diameter d of the cutter in this position in order to achieve the purpose of shear machining of the sawteeth without affecting the stiffness of the drill core.

Description

DESCRIPTION OF DRAWINGS

[0013] FIG. 1 is a main view of a vertical-edge double-step sawtooth cutter for preparing high-quality holes of composite material and hybrid stack structure thereof.

[0014] FIG. 2 is a partial enlarged drawing of a sawtooth cutting region E in FIG. 1.

[0015] In the figures: 1 major cutting edge; 2 tooth space; 3 sawtooth; 4 vertical chip breaking edge; 5 minor cutting edge; 6 chip groove;

[0016] 7 cutter axis; 8 initial cutting face; 9 second cutting face; 10 second step major cutting edge;

[0017] 11 upper edge of the sawtooth; A major cutting edge region; B minor cutting edge region; C shank region; D step vertical-edge region; E sawtooth cutting region;

[0018] a margin width of vertical chip breaking edge 4; b margin width of minor cutting edge 5; c width of chip groove;

[0019] d first step diameter; e axial length of vertical chip breaking edge 4; n.sub.1 first vertex angle of major cutting edge 1;

[0020] n.sub.2 second vertex angle of major cutting edge 1; n.sub.3 included angle between second step major cutting edge and cutter axis 7;

[0021] .sub.1 helix rake angle of minor cutting edge 5; .sub.2 helix rake angle of vertical chip breaking edge 4; W.sub.t sawtooth width;

[0022] W.sub.g width of tooth space; D.sub.t depth of tooth space; and helix angle of sawtooth.

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 and FIG. 2, a vertical-edge double-step sawtooth cutter for preparing high-quality holes of composite material and hybrid stack structure thereof in the present invention comprises three parts which are a major cutting edge region A, a minor cutting edge region B and a shank region C, wherein the minor cutting edge region. B comprises a step vertical-edge region D and a sawtooth cutting region E. A major cutting edge 1 of the major cutting edge region A partially thins an initial cutting face 8 to obtain a second cutting face 9 so as to form a double-vertex angle structure; progressive cutting can be realized, so as to reduce the axial force and improve the drilling quality of the composite material, wherein a first vertex angle n.sub.1 is 102 and a second vertex angle n.sub.2 is 90. The minor cutting edge region B has two chip grooves 6 and forms two minor cutting edges 5. A helix rake angle .sub.1 of the minor cutting edges 5 is 15. The nominal diameter of the cutter is 6 mm. The diameter d of the first step is 4.88 mm. The width c of the chip grooves is 3 mm. The ratio of the width c of the chip grooves to the diameter d of the first step of the cutter is 0.61, which can ensure that the rigidity of the cutter satisfies processing requirements. The margin width a of a vertical chip breaking edge 4 is 1.5 mm. The margin width b of the minor cutting edges 5 is 1 mm. The value of the margin width a of the vertical chip breaking edge 4 is larger, to ensure the strength of the vertical chip breaking edge 4.

[0025] The step vertical-edge region D adopts a double-step negative-step angle structure. The double-step structure is adopted to realize segmented cutting and reduce the axial force, so as to achieve the purpose of achieving the damage to the composite material. The second step adopts a negative step angle which can directly remove the metal outlet burr and outlet burr of the composite material from outlet roots. An included angle n.sub.3 between a second step major cutting edge 10 and a cutter axis 7 is 110. A vertical chip breaking edge 4 is thinned on each minor cutting edge 5 to change the original movement direction of metal chips to bend the metal chips and realize efficient chip breaking and crushing of the tam. Thus, the chips can be smoothly discharged along the chip grooves, thereby reducing the contact among the chips, the composite material and the metal hole walls and improving the finish degree of the hole walls and aperture accuracy. The axial length e of the vertical chip breaking edge 4 is 4 mm, which is much larger than feed per tooth of the cutter. A helix rake angle .sub.2 of the vertical chip breaking edge 4 is 13.

[0026] The sawtooth cutting region E is composed of a plurality of sawteeth 3 and tooth spaces 2 which are distributed on a drill cutting edge; the sawteeth 3 and the tooth spaces 2 are spiral around a drill axis; and a helix angle of the sawteeth is 79. Upper edges of the sawtooth 11 of the sawteeth are used as sawtooth cutting edges, and are thinned to form a rake angle which is 20. The sawtooth structure is located between the step vertical-edge region D and the major cutting edge region A. The quantity of the sawteeth 3 is three. The width W.sub.g of the tooth spaces of the sawteeth 3 is 0.7 mm. The width W.sub.t of the sawteeth 3 is 0.5 mm. The depth D.sub.t of the tooth spaces is 0.8 mm. The thickness of a drill core of the cutter is 2.2 mm. The sum of twice the depth D.sub.t of the tooth spaces and the thickness of the drill core is less than the diameter d of the cutter in this position. When the composite material is drilled, the generated burrs bounce back into the sawtooth structure at the outlet and the inlet of drilling. In the process of downward drilling, the burrs that bounce back into the sawtooth structure are cut, and sheared, so as to effectively remove the burrs at the outlet and the inlet in the drilling process, reduce the effect of a tear damage during formation of a final hole and substantially enhance the cutting ability of the cutter.

[0027] The vertical-edge double-step sawtooth cutter for preparing high-quality holes of composite material and hybrid stack structure thereof in the present invention has the step structure which can realize segmented cutting and reduce processing damage. Meanwhile, the step angle is a negative value. Metal outlet burr and outlet burr of the composite material are removed from roots, thereby improving outlet quality. The vertical-edge structure changes the original movement direction of the metal chips, can bend and break the metal chips and can reduce the scratch of the metal chips to the upper-layer composite material and the metal hole walls. The sawtooth structure can effectively inhibit damage of drilling inlet and outlet layering and burr of the composite material. Finally, high-quality and high-efficiency processing of preparing high-quality holes of the composite material and the hybrid stack structure thereof is realized.