Segmented orbital drill

Abstract

Segmented orbital drill (10), comprising: a segmented part (18) comprising a pre-machining cutting part (40) and several finishing cutting parts (42), wherein the pre-machining cutting part (40) has a diameter (44) that differs from a diameter (46) of the several finishing cutting parts (42); and a cutting neck section (26) between the segmented section (18) and a shaft (22); characterized in that the segmented orbital drill (10) has a guide part (14) between the segmented part (18) and an end (16) of the segmented orbital drill (10) and an undercut (20) between the guide part (14) and the segmented part (18), wherein the guide part (14) has a diameter (30) which is smaller than the diameter (32) of the segmented part (18).

Description

[0001] The invention relates to a segmented orbital drill according to the preamble of claim 1. Furthermore, the invention relates to a method for machining a workpiece using a segmented orbital drill.

[0002] Fiber-reinforced plastics (FRPs) are widely used in the aerospace industry due to their high specific strength and stiffness. FRPs are composite materials consisting of a soft resin matrix and high-strength fiber reinforcement. Typical fiber reinforcements include carbon fibers (CFRP), glass fibers (GFRP), Kevlar fibers, and the like. FRPs are often processed into a laminated structure. FRPs exhibit excellent in-plane strength but low interlaminar strength.

[0003] Multifunctional end effectors, portable orbital machines and CNC machines produce orbital (spirally expanded) holes and / or conventionally drilled holes in composite stack materials.

[0004] The main problem with machining composite stack materials is the accelerated wear at the tool edges. Tool life is very short, even with advanced substrates and coatings.

[0005] DE 101 62 430 A1 shows a milling cutter for circular milling of a threaded hole into solid material without pre-drilling a core hole.

[0006] Furthermore, milling tools are known from DE 93 17 312 U1, DE 36 27 798 A1, DE 197 39 370 A1 and US 4 411 563 A.

[0007] DE 699 26 067 T2 describes a method for creating a hole in a composite material workpiece.

[0008] JP 2005-120 984 A shows a cutting tool for producing a valve seat surface and a valve guide opening in a cylinder head.

[0009] The US 2010 / 0 183 383 A1, the US 2008 / 0 069 656 A1 and the US 7 431 538 B1 show end mills for orbital drilling.

[0010] The problem of accelerated wear of tool edges during the machining of composite stack materials is solved by providing a segmented orbital drill that uses geometric shapes to extend tool life.

[0011] According to one aspect, a segmented orbital drill comprises a segmented part containing a pre-machining cutting section and at least one finishing cutting section, wherein the pre-machining cutting section has a diameter different from the diameter of the at least one finishing cutting section; and a clearance neck section between the segmented part and a shank. The segmented orbital drill further comprises a guide section between the segmented part and an end of the segmented orbital drill, as well as an undercut between the guide section and the segmented part. The guide section has a diameter smaller than the diameter of the segmented part.

[0012] According to another aspect, a method for machining a workpiece using a segmented orbital drill, comprising a guide part, a segmented part, and a clearance neck between the segmented part and a shank, includes drilling a hole in a first layer of material with the segmented part of the segmented orbital drill; drilling a hole in a second layer of material with the guide part while the hole in the first layer of material is being drilled with the segmented part, until the segmented part has completely drilled through the first layer of material; and drilling a hole in a third layer of material with the segmented part without using the guide part, until the segmented part has completely drilled through the third layer of material.

[0013] Although various embodiments of the invention are presented, the particular embodiments shown should not be interpreted as limiting the claims. It is expected that various changes and modifications can be made without departing from the scope of protection of this invention. Fig. Figure 1 is a top view of an exemplary embodiment of a segmented orbital drill according to an embodiment of the invention; Fig. Figure 2 is an enlarged cross-sectional view of the segmented part of the orbital drill along line 2-2 of Fig. 1; and Fig. Figures 3(a) - (f) are an isometric view of a method for machining a workpiece having an upper layer of CFRP material and a lower layer of metallic material, using the cutting tool according to the invention.

[0014] The following are descriptions and explanations of one version of a combination cutting tool and a method for machining a workpiece. It should be noted, however, that the combination cutting tool and the machining method can be configured to suit a specific application and are not limited to the illustrated example.

[0015] On the Fig. Referring to Figures 1-3, in which the same reference numerals represent the same elements, a segmented orbital drill for performing a machining operation on a workpiece is generally shown at Figure 10. In one embodiment, the workpiece is ( Fig. 3) a composite stack material with an upper layer 62, a middle layer 64, and a lower layer 66. The upper and lower layers 62, 66 can, for example, comprise a metal such as titanium and the like. The middle layer 64 can comprise a different material than the upper and lower layers 62, 66. For example, the middle layer 64 can comprise a carbon fiber reinforced plastic (CFRP) material and the like. As used here, “upper” refers to the first material to be machined by the orbital drill 10, “middle” refers to the second material to be machined by the orbital drill 10, and “lower” refers to the third material to be machined by the orbital drill 10 during the machining operation.

[0016] In general, the orbital drill 10 comprises a main body 12 and a guide part 14 at one end 16 of the orbital drill 10. The guide part 14 is optional and depends on the composite stack material to be machined by the orbital drill 10. In one example, the guide part 14 can be used as a first cutting element for drilling the layer 64 of CFRP material, if present in the workpiece 60.

[0017] The orbital drill 10 further comprises a segmented section, generally shown at 18, with several cutting edges, and an undercut 20 between the guide section 14 and the segmented section 18. The orbital drill 10 also includes a shank 22 at the other, opposite end 24. Furthermore, the orbital drill 10 includes a clearance collar 26 between the segmented section 18 and the shank 22. The purpose of the clearance collar 26 is to allow the orbital drill 10 to be cleared of debris during a machining operation. The clearance collar 26 is also located where the chips are ejected. The clearance collar 26 is dimensioned such that its length is greater than the total thickness of the workpiece 60. Fig. 3) Furthermore, the orbital drill 10 contains a central longitudinal axis 28 that runs along the entire length of the orbital drill 10. Coolant holes 38 ( Fig. 2) can be positioned near the guide part 14 to assist in cooling the orbital drill 10. The guide part 14, the segmented part 18, and part of the clearance neck part 26 of the orbital drill 10 can include one or more (not shown) chip flutes of a type well known in the art to assist in chip removal.

[0018] In general, the guide part 14 has a diameter 30 that is smaller than the overall diameter 32 of the segmented part 18. The diameter 30 of the guide part 14, which is optional, is dimensioned for drilling the CFRP material in the workpiece 60 and is specific to a particular application. Various parameters for the diameter 30 include, but are not limited to, the end hole size, the orbital offset, the diameter of the main body 12 of the drill 10, and the amount of composite stack material to remain in the hole to be drilled.

[0019] The free-cutting neck section 26 has a diameter 34, which is slightly smaller than the overall diameter 32 of the segmented section 18, but larger than the diameter 30 of the guide section 14. The overall diameter 32 of the segmented section 18 of the orbital drill 10 is essentially equal to the final diameter of the hole 68 ( Fig. 3), which is to be drilled by the orbital drill 10. In the illustrated embodiment, the shank 22 has a diameter 36 that is larger than the clearance neck section 26 and the guide section 14 and approximately equal to the overall diameter 32 of the segmented section 18. It is understood that the invention is not limited by the specific diameter and that the invention can be implemented with any desired diameter, depending on the design parameters of the orbital drill 10.

[0020] Now on Fig. 2. Referring to this, one aspect of the invention is that the segmented part 18 of the orbital drill 10 contains several cutting elements. In particular, the segmented part 18 contains a pre-machining cutting element 40 and several finishing cutting elements 42. In the illustrated embodiment, the segmented part 18 of the orbital drill 10 contains a total of three (3) finishing cutting elements 42. However, it is understood that the invention is not limited by the number of finishing cutting elements 42 and that the invention can be exercised with any desired number of finishing cutting elements 42, depending on the application of the orbital drill 10.

[0021] As mentioned above, the segmented part 18 has an overall diameter of 32. This is because the pre-machining cutting part 40 has a different diameter than the finishing cutting parts 42. Specifically, the pre-machining cutting part 40 has a diameter 44 that is slightly smaller than the diameter 46 of the finishing cutting parts 42. For example, the pre-machining cutting part 40 may have a diameter 44 of approximately 0.390 inches (9.9 mm), and the finishing cutting parts 42 may have a diameter 46 of approximately 0.394 inches (10.0 mm). The diameter 44 of the pre-machining cutting part 40 determines the chip size for the finishing cutting parts 42.

[0022] It is understood that the invention is not limited by the relative diameters between the pre-machining cutting element 40 and the finishing cutting elements 42, and that the invention can be implemented with any desired relative diameter depending on the application of the orbital drill 10. Furthermore, it is understood that the invention is not limited to a single pre-machining cutting element 40, and that the invention can be implemented with any desired number of pre-machining cutting elements depending on the application of the orbital drill 10. For example, the invention can be implemented with two or three pre-machining cutting elements, each having a different diameter that may differ from the diameter 46 of the finishing cutting elements 42.

[0023] The orbital drill 10 includes a tapered surface 48 between the guide part 14 and the segmented part 18. The purpose of the tapered surface 48 is to allow the segmented part 18 of the orbital drill 10 to easily enter the metal layer 66 of the workpiece 60 after a pilot hole has been drilled into the CFRP material 64 by the guide part 14. Furthermore, the tapered surface 48 can be used to remove any burr from the hole 68 of the workpiece 60 ( Fig. 3) in a spiral widening process or a circular process, if required. In the illustrated embodiment, the tapered surface 48 is formed at an angle 50 of approximately ten (10) degrees with respect to an axis 52 perpendicular to the longitudinal axis 28 of the orbital drill 10. However, it is understood that the invention is not limited by the angle at which the tapered surface 48 is formed and that the invention can be exercised with any desired angle that allows for easy transition of the cutting tool between the guide part 14 and the segmented part 18 of the orbital drill 10.

[0024] The finishing cutting section 42 of the segmented part 18 contains several segments or sections 42a, 42b, and 42c, separated by substantially V-shaped grooves 54a, 54b, and 54c. The orbital drill 10 may have a radius 53 for the transition between section 42c and the clearance neck section 26. Each section 42a, 42b, and 42c of the finishing section 42 has approximately the same diameter 46, which differs from the diameter 44 of the pre-finishing section 40. The groove 54a separates section 42a from the pre-finishing cutting section 40, the groove 54b separates section 42a from section 42b, and the groove 54c separates section 42b from section 42c. Each groove 54a, 54b and 54c has a front wall 55, a back wall 56 and a radius 57 in between. The back wall 56 forms a cutting edge for the orbital drill 10.

[0025] In the illustrated embodiment, the front wall 55 and the rear wall 56 form an angle 58 of approximately ninety (90) degrees with respect to each other. However, the front wall 55 forms an angle 55a with respect to the axis 52, which differs from the angle 56a formed by the rear wall 56 with respect to the axis 52. In particular, the angle 55a formed by the front wall 55 with respect to the axis 52 is larger than the angle 56a formed by the rear wall 56 with respect to the axis 52. It is understood that the invention is not limited by the relative angle between the front wall 55 and the rear wall 56 and that the invention can be implemented with any desired angle, depending on the application of the orbital drill 10.

[0026] The sections 42a, 42b, and 42c of the segmented orbital drill 10 according to the invention serve several different purposes. First, the sections 42a, 42b, and 42c result in less contact with the workpiece 60, thereby reducing energy consumption and minimizing deflection of the orbital drill 10. Second, the grooves 54a, 54b, and 54c between the sections 42a, 42b, and 42c allow a fresh cutting edge (i.e., the back wall 56) to be exposed when the orbital drill 10 is worn in the axial direction (along the longitudinal axis 28), for example, at position 49 on the leading edge of the pre-machining cutting part 40. Thirdly, the fresh cutting edges are better suited for chip formation than the worn edges when the orbital drill 10 moves in the direction of arrow 51 during a machining operation ( Fig. 2) moved forward. Fourth, chipping or damage to a cutting edge (i.e., the back wall 56) of a preceding section, for example, section 42a, does not affect the other sections (42b and 42c) due to the grooves 54a, 54b, and 54c separating each section 42a, 42b, and 42c. Fifth, the service life of the orbital drill 10 is extended because damage that can propagate along the grooves 54a, 54b, and 54c is better controlled compared to conventional orbital drills.

[0027] Now to the Fig. 3(a) - (f) With reference to this, a method for machining a composite workpiece 60 comprising an upper layer 62 of metal, a middle layer 64 of CFRP material, and a lower layer 66 of metal is described below. In the Fig. 3(a) - (f) For the sake of clarity, the orbital drill 10 is shown as a solid and the workpiece 60 in cross-section. It is understood that the composite workpiece 60, which is machined by the orbital drill 10, serves only illustrative purposes and that the basic principles of the invention can also be applied to the machining of workpieces with one or more layers of materials, which may be different or have different material properties.

[0028] Fig. Figure 3(a) shows a cross-section of the orbital motion of the tool and represents a double drill, illustrating the extent of the full revolution of the orbital drill 10. Fig. Figures 3(b) - (g) show the orbital drill 10 in the leftmost position in the hole 68 to be drilled. Fig. 3(b) The orbital drill 10 is inserted into a pre-drilled hole 70 and uses an orbital drilling cycle (spiral expansion or circular) to begin drilling a hole 68 into the upper layer 62 of metal with the pre-finishing cutting portion 40 of the orbital drill 10. At this point in the machining cycle, the central longitudinal axis 28 of the orbital drill 10 is moved in a spiral or circular direction around the central axis 72 of the hole 68. In other words, the central longitudinal axis 28 of the orbital drill 10 is moved in a spiral or circular motion a total distance 74 around the central axis 68 of the hole 68. The hole 68 may have the full diameter only at the inlet, or it may be fully finished to the full diameter, or it may have some finishing material on the inner diameter (ID) of the hole 68.

[0029] In Fig. 3(c) The orbital drill 10 is moved in the direction of arrow 51, so that both the pre-machining cutting section 40 and the finishing cutting section 42 of the segmented part 18 engage the metal layer 62, and the guide section 14 drills a hole 76 into the middle layer 64 of CFRP material. It should be noted that during this cycle, the removal of the CFRP layer 64 is carried out solely by the use of the guide section 14 of the orbital drill 10, and that the segmented part 18 is not used at all. Thus, there is no wear on the segmented part 18 of the orbital drill 10 during this cycle.

[0030] In Fig. 3(d) the orbital drill 10 has finished drilling the upper layer 62 and continues drilling through the middle layer 64 using the guide part 14. In Fig. 3(e) The segmented part 18 and the guide part 14 of the orbital drill 10 continue drilling through the middle layer 64 of the workpiece 60. It should be noted that during the Fig. 3(d) and Fig. 3(e) In the drilling operations shown, the guide part 14 of the orbital drill 10 now acts as a “step drill” to drill a guide hole for the segmented part 18 of the orbital drill 10.

[0031] In Fig. 3(f) the segmented part 18 of the orbital drill 10 has almost completely drilled through the middle layer 64 and the guide part 14 is no longer used.

[0032] In Fig.3(g) The orbital drill 10 is moved in the direction of the arrow to drill completely through the lower layer 66 until the segmented part 18 of the orbital drill 10 has completely drilled through the workpiece 60. As can be seen, the clearance collar part 26 provides a gap between the orbital drill 10 and the workpiece 60. At this point, the orbital drilling operation is complete.

[0033] As described above, the segmented orbital drill 10 according to the invention offers many advantages compared to conventional cutting tools. For example, the segmented orbital drill 10 allows a fresh cutting edge (i.e., the back wall 56) to be exposed when the drill 10 is worn in the axial direction. Furthermore, the segmented orbital drill 10 causes less contact with the workpiece 60, thereby reducing energy consumption and minimizing deflection of the drill 10. Additionally, the service life of the drill 10 is extended because damage that can propagate along the grooves 54a, 54b, and 54c is better controlled compared to conventional orbital drills.

[0034] Although currently preferred embodiments have been described, the invention can also be implemented in other ways within the scope of protection of the attached claims.

Claims

[1] Segmented orbital drill (10), comprising: a segmented part (18) comprising a pre-machining cutting part (40) and several finishing cutting parts (42), wherein the pre-machining cutting part (40) has a diameter (44) that differs from a diameter (46) of the several finishing cutting parts (42); and a cutting neck section (26) between the segmented section (18) and a shaft (22); characterized by , that the segmented orbital drill (10) has a guide part (14) between the segmented part (18) and an end (16) of the segmented orbital drill (10) and an undercut (20) between the guide part (14) and the segmented part (18), wherein the guide part (14) has a diameter (30) which is smaller than the diameter (32) of the segmented part (18). [2] Segmented orbital drill (10) according to claim 1, wherein the diameter (44) of the pre-machining cutting part (40) is smaller than the diameter (46) of the multiple finishing cutting parts (42). [3] Segmented orbital drill (10) according to claim 1, wherein the pre-machining cutting part (40) and the multiple finishing cutting parts (42) are separated by a substantially V-shaped groove (54) formed by a front wall (55), a rear wall (56) and a radius (57) in between. [4] Segmented orbital drill (10) according to claim 3, wherein the rear wall (56) and the front wall (55) form an angle (55a, 56a) with respect to each other. [5] Segmented orbital drill (10) according to claim 4, wherein the angle (55a, 56a) is approximately ninety degrees. [6] Segmented orbital drill (10) according to claim 3, wherein an angle (55a) formed by the front wall (55) with respect to an axis (52) perpendicular to a mean longitudinal axis (28) of the segmented orbital drill (10) is greater than an angle (56a) formed by the rear wall (56) with respect to the axis (52) perpendicular to the mean longitudinal axis (28). [7] Segmented orbital drill (10) according to one of the preceding claims, further comprising a tapered surface (48) between the undercut (20) and the segmented part (18). [8] Method for machining a workpiece (60) using a segmented orbital drill (10) comprising a guide part (14) and a segmented part (18) and a clearance neck part (26) between the segmented part (18) and a shank (22), wherein the method comprises: Drilling a hole in a first layer of material (62) with the segmented part (18) of the segmented orbital drill (10); Drilling a hole in a second material layer (64) with the guide part (14), while the hole in the first material layer (62) is drilled with the segmented part (18) until the segmented part (18) has completely drilled through the first material layer (62); and Drilling a hole in a third material layer (66) with the segmented part (18) without using the guide part (14) until the segmented part (18) has completely drilled through the third material layer (66). [9] Method according to claim 8, further comprising the step of removing burr from the hole using a tapered surface (48) by using a spiral enlargement drilling operation or a circular drilling operation.

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