KR102143901B1 - Helical Groove Attached Drill Bit - Google Patents

Abstract

In the present invention, a fine groove is formed in the land portion of a drill bit for general CFRP hole processing, and has a twist angle considerably larger than that of the chip discharge groove, and the edge of the tool tip side of the spiral groove formed in this way has an acute angle. By providing, there is a feature of having a drill bit structure additionally including a helical blade formed so that residual burrs can be removed when the drill bit is retracted after passing through the hole, and CFRP hole processing quality is improved without changing or adding a process. Can be improved.

Description

Helical Groove Attached Drill Bit}

The present invention relates to a hole processing and deburring tool for carbon fiber composite CFRP.

The content described in this section merely provides background information on the present embodiment and does not constitute the prior art.

Carbon Fiber Reinforced Plastic (CFRP) composites have excellent mechanical properties and provide lighter weight compared to conventional metal materials, so they are being applied to the fields of aviation, automobiles and sports and leisure. CFRP, especially used as a structural material, contains a very large number of holes for connection with other components.

On the other hand, CFRP is characterized by a high tool wear rate as it contains carbon fiber, a material with very high rigidity. As the demand for CFRP increases, the cutting quality of CFRP is improved by a dedicated tool that considers cutting characteristics or a CVD coating tool to increase tool life, but rapid initial wear of the tool edge is caused by the tool life cycle. It can also cause hole processing defects inside.

In the case of aircraft CFRP parts, it has been reported that deburring processing costs account for 30% of the total parts manufacturing cost, so hole processing defects account for the largest portion of the total manufacturing cost. For example, in the case of the Boeing 747, there are 300 million holes for connecting various parts, and in the case of the Boeing 787, where carbon composites are fully applied, the number of holes related to CFRP is 100,000. The cost of the material itself is high for CFRP, but not only the machining time required for drilling holes, but also the tool cost is considerable.

The types of defects that occur in the hole processing of CFRP include uncut fiber, frying, chipping, uncut resin, spalling and delamination. Etc. The high stiffness of carbon fiber, bonding resin whose physical properties rapidly change at high temperatures, low heat transfer rate of CFRP, and local defects inherent in the CFRP molding process are the causes of such defects.

It is an object of the present invention to provide a drill bit structure capable of reducing burrs including non-cut fibers among defects generated in CFRP hole processing.

In order to solve the above problems, the helical blade drill according to an embodiment of the present invention includes a plurality of first cutting blades formed at the tip of the cylindrical cutting part; A plurality of first grooves formed spirally from the first cutting edge and having a first twist angle on the outer peripheral surface of the cutting portion; A first land disposed between adjacent first grooves; A second groove formed in a spiral shape on the first land with a second twist angle greater than the first twist angle; A second land disposed between adjacent second grooves; And a third cutting edge disposed in a direction of a rear end of the cutting portion among the spiral edges of the second land and formed to remove burrs when the cutting portion is transferred in the rear end direction.

In addition, among the spiral edges of the second land, the first edge located in the front end direction of the cutting part has an obtuse angle, the second edge located in the rear end direction of the cutting part among the spiral edges of the second land, and the third cutting edge has an acute angle. , The helical-edged drill is characterized in that it is formed to remove the burr when retreating after forming a through hole in the workpiece.

In addition, the second twist angle is characterized in that the range of 70 to 80 degrees.

In addition, the width of the second groove is characterized in that the range of 0.5 mm to 1.5 mm.

In addition, the depth of the second groove is characterized in that the range of 1 mm to 2 mm.

In addition, the first edge has an angular size of 120 degrees to 140 degrees with respect to the outer circumferential surface, and the second edge has an angular size of 65 degrees to 85 degrees with respect to the outer circumferential surface.

In the present invention, a fine groove is formed in the land portion of a drill bit for general CFRP hole processing, and has a twist angle considerably larger than that of the chip discharge groove, and the edge of the tool tip side of the spiral groove formed in this way has an acute angle. By providing, it relates to a drill bit structure that further includes a helical blade formed so that the residual burrs can be removed when the drill bit is retracted after passing through the hole, and the CFRP hole cutting quality can be improved without changing or adding a process. It can have an effect.

1 is a perspective view showing the structure of a drill with a helical blade according to an embodiment of the present invention.
Figure 2 is a side view showing the structure of a helical-edged drill according to an embodiment of the present invention.
3 is a front view showing the structure of a helical-edged drill according to an embodiment of the present invention.
4 is a side view showing a deburring process of a helical-edged drill according to an embodiment of the present invention.
5 is a conceptual diagram illustrating the concept of non-cutting fiber deburring using a helical-edged drill according to an embodiment of the present invention.
6 shows experimental conditions for comparing and verifying the CFRP hole processing performance of a helical-edged drill according to an embodiment of the present invention.
7 shows the results of a CFRP hole processing experiment using a general drill in two cases where the tip angles are 90 degrees and 118 degrees.
8 shows the results of a CFRP hole processing experiment using a helical-edged drill according to an embodiment of the present invention for both the tip angles of 90 degrees and 118 degrees.
9 is a result of measuring and comparing the inner surface roughness of the hole according to the processing experiment of FIGS. 7 and 8.
10 is a SEM image comparing the inner circumferential surface of a hole processed by a general drill and a helical-edged drill according to an embodiment of the present invention when the feed is changed at the same rotational speed.
11 is a SEM image comparing the inner circumferential surface of a hole processed by a general drill and a helical-edged drill according to an embodiment of the present invention when the rotational speed is changed at the same feed.
12 is a 3D laser scan image comparing the inner surface of the drill with a helical blade according to an embodiment of the present invention when the feed is changed at the same rotational speed.
13 is a 3D laser scan image comparing the inner surface of the drill with a helical blade according to an exemplary embodiment of the present invention when the rotational speed is changed at the same feed.

Hereinafter, some embodiments of the present invention will be described in detail through exemplary drawings. In adding reference numerals to elements of each drawing, it should be noted that the same elements have the same numerals as possible even if they are indicated on different drawings. In addition, in describing the present invention, when it is determined that a detailed description of a related known configuration or function may obscure the subject matter of the present invention, a detailed description thereof will be omitted.

In addition, in describing the constituent elements of the present invention, terms such as first, second, A, B, (a) and (b) may be used. These terms are only for distinguishing the component from other components, and the nature, order, or order of the component is not limited by the term. Throughout the specification, when a part'includes' or'includes' a certain element, it means that other elements may be further included rather than excluding other elements unless otherwise stated. . In addition, the'... Terms such as'sub' and'module' mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software.

1 is a perspective view showing the structure of a drill with a helical blade according to an embodiment of the present invention.

Figure 2 is a side view showing the structure of a helical-edged drill according to an embodiment of the present invention.

3 is a front view showing the structure of a helical-edged drill according to an embodiment of the present invention.

Referring to FIG. 1, the helical-edged drill bit 10 according to an embodiment of the present invention has a torsion angle considerably larger than the helix angle of a chip discharge groove (groove, flute) in the land portion in a general drill structure. The branch is characterized by the formation of a groove. The groove formed in the land portion has an acute angle at the tip side of the drill, and when the drill is retracted, the hole exit edge 820 and the non-cut fiber 700 of the hole inner wall are cut and removed to perform deburring.

Referring to Figures 2 and 3, the helical blade drill 10 according to an embodiment, a plurality of first cutting blades 100 formed on the tip 900 of the cutting part in a cylindrical shape; A plurality of first grooves 120 formed in a spiral form from the first cutting edge 100 with a first twist angle 210 on the outer peripheral surface 110 of the cutting part; A first land 220 disposed between adjacent first grooves 120; A second groove 340 formed in a spiral shape on the first land 220 with a second twist angle 310 greater than the first twist angle 210; A second land 390 disposed between adjacent second grooves 340; And a third cutting edge 300 disposed in the rear end direction 2 of the cutting portion among the spiral edges of the second land 390 and formed to remove burrs when the cutting portion is transferred in the rear end direction 2 do.

Among the spiral edges of the second land 390, the first edge 350 located in the tip direction (1) of the cutting part has an obtuse angle, and among the spiral edges of the second land 390, the first edge 350 located in the rear end direction (2) of the cutting part As the two corners 360, the third cutting edge 300 has an acute angle, so that the helical-edged drill 10 forms a through hole in the workpiece 800 and then is formed to remove the burr when retreating.

The first edge 350 of the second land 390 located opposite the tip 900 of the cutting part has an obtuse angle, so when the drill descends in the tool tip direction 1 to perform hole processing, the first edge 350 ) Can be prevented from adding unnecessary cutting load or being damaged.

The second groove 340 is formed in the first land 220 of the drill with a second twist angle 310, and may be formed as many as a plurality of rotations along the outer circumferential surface 110, and in one embodiment, about 3 The case of rotation is illustrated. A second land 390 is disposed between the adjacent second grooves 340.

In one embodiment, the second twist angle 310 may be 70 degrees, and the second twist angle 310 may range from 70 degrees to 80 degrees.

It is preferable that the second land 390 has a sufficient cross-sectional size to prevent the stiffness of the drill tool from deteriorating. That is, the cross-section of the second groove 340 is advantageous as it is smaller in order to prevent the rigidity of the drill tool from deteriorating, and sufficient depth and width are secured to remove burrs by cutting the non-cutting fiber 700, etc. It is necessary to do. This may be selected in consideration of the basic specifications of the drill or the burr generation characteristics of CFRP, which is the workpiece 800. In one embodiment, the entrance side width 370 of the second groove 340 is 1 mm, the depth 380 is 1.5 mm, and the second edge 360 on the side of the tool tip 900 of the second groove 340 is The drill outer circumferential surface 110 is formed with a sharp edge having an acute angle of 75 degrees, and the first edge 350 of the second groove 340 opposite the tool tip 900 is set to an obtuse angle of 130 degrees. The width 370 and the depth 380 of the second groove 340 were selected by referring to the fact that the non-cutting fiber 700 is generated with a maximum length of about 2.5 mm in the case of an embodiment.

The third cutting edge 300 formed in the tool rear end direction 2 of the second land 390 does not participate in cutting when the drill forms a hole in the workpiece 800, and after the drill penetrates the hole, the tool rear end Cutting is performed only when retreating in the direction 2, that is, when machining burrs that may occur in the hole exit edge 820 and the hole inner circumferential surface 810. The third cutting edge 300 can prevent damage or rapid wear of the drill cutting edge by performing cutting in this manner. The third cutting edge 300 has a positive rake angle so that the non-cutting fiber 700, which may be degraded due to peeling of the fiber from the resin inside the hole of the CFRP, It can be removed by cutting sharply under low cutting load.

4 is a side view showing a deburring process of a helical-edged drill according to an embodiment of the present invention.

Referring to FIG. 4, the drill rotates in a counterclockwise direction (3) when viewed from the tip 900 side, and after the through hole is formed, the drill retreats upward, and the second cutting edge 200 and the third cutting edge ( 300) represents a concept in which the drill is separated from the hole after the hole inner peripheral surface 810 and the hole exit edge 820 are post-processed.

5 is a conceptual diagram illustrating the concept of non-cutting fiber deburring using a helical-edged drill according to an embodiment of the present invention.

Referring to FIG. 5, the non-cutting fiber 700 is accommodated in the second groove 340 while the drill rotates and retreats, and is cut and removed as the third cutting edge 300 rotates and advances. The third cutting edge 300 is involved in deburring only when the drill is retracted in the direction of the rear end of the tool 2, so that even though it has a positive cutting edge angle, the degree of wear can be low, so that the required tool life of the drill can be secured.

6 shows experimental conditions for comparing and verifying the CFRP hole processing performance of a helical-edged drill according to an embodiment of the present invention.

In one embodiment, the experiment for comparative verification was conducted on a woven type of CFRP, but the helical bladed drill 10 according to an embodiment may have the same effect in the case of uni-directional (UD) CFRP. .

Referring to FIG. 6, in the case of a general drill tool, an example in which non-cut fibers having a length of about 2.5 mm are observed in all weaving directions under a given cutting condition.

7 shows the results of a CFRP hole processing experiment using a general drill in two cases where the tip angles are 90 degrees and 118 degrees.

8 shows the results of a CFRP hole processing experiment using a helical-edged drill according to an embodiment of the present invention for both the tip angles of 90 degrees and 118 degrees.

When comparing FIGS. 7 and 8, it can be seen that in the case of the helical bladed drill 10 according to an embodiment, very little remaining non-cutting fibers 700 remain. For reference, in the case of the comparative experiment, it was confirmed that the occurrence of burrs was less than when the tip angle of the drill was 90 degrees. The processing state of the hole exit edge 820 was also excellent in the case of the helical bladed drill 10 according to an embodiment.

9 is a result of measuring and comparing the inner surface roughness of the hole according to the processing experiment of FIGS. 7 and 8.

In addition, referring to FIG. 9, it was confirmed that not only the degree of burr generation, but also the surface roughness of the inner circumferential surface of the machined hole was generally excellent in the machining result by the helical-edged drill 10 according to an embodiment.

10 is a SEM image comparing the inner circumferential surface of a hole processed by a general drill and a helical-edged drill according to an embodiment of the present invention when the feed is changed at the same rotational speed.

Referring to FIG. 10, in the case of a general drill, it is observed that the fibers arranged in parallel with the circumferential direction of the hole inner circumferential surface 810 are exposed as they are without being cut, which is found to increase as the feed of the drill increases. When the drill descends for hole processing, a significant cutting load is applied to the first cutting edge 100 and the second cutting edge 200, and heat generated by the cutting process may accumulate in the processed material, and thus carbon fiber The temperature of the resin holding it rises and may not provide sufficient support for cutting the carbon fiber. As a result, not only the protruding burrs but also the non-cutting fibers 700 in parallel adjacent to the hole circumferential surface are protruded without being cut, and as a result, the surface roughness may be reduced.

On the other hand, in the drill according to an embodiment of the present invention, the third cutting edge 300 cuts the non-cutting fiber 700 while secondary processing the inner circumferential surface 810 of the hole when retreating in the tool rear end direction (2). You can get a good quality surface.

11 is a SEM image comparing the inner circumferential surface of a hole processed by a general drill and a helical-edged drill according to an embodiment of the present invention when the rotational speed is changed at the same feed.

Referring to FIG. 11, when the number of rotations is increased at the same feed, the surface quality is deteriorated due to factors such as cutting load and heat generation.It is observed both in the case of a general drill or in the case of the helical-edged drill 10 according to an embodiment. do. However, it was confirmed that the degree is less in the case of the helical bladed drill 10 according to an embodiment.

12 is a 3D laser scan image comparing the inner side surface of the drill with a helical blade according to an embodiment of the present invention when the feed is changed at the same rotational speed.

13 is a 3D laser scan image comparing the inner surface of the hole processing of a general drill and a helical-edged drill according to an embodiment of the present invention when the rotational speed is changed at the same feed.

12 and 13 illustrate the height of a partial curved portion of the hole inner circumferential surface 810 by three-dimensional scanning with a laser. Referring again to FIG. 6, it can be seen from the 3D laser scan image that the processed product 800 is a laminated form of woven carbon fibers. In FIGS. 12 and 13, the dark blue line segment shape can be seen between the carbon fibers parallel to the circumferential surface, and the line segment shape is a scan result of a region including a plurality of layer regions. In addition, the surface processed with a general tool includes a number of dot shapes, which can be seen as being caused by carbon fibers woven in a direction perpendicular to the scanned circumferential surface. For example, it can be interpreted that the carbon fiber perpendicular to the circumferential surface is cut and the resin part temporarily pressed due to elastic deformation rises after the type of processing, so that the cutting surface of the carbon fiber is lower than the resin surface.

Referring to FIG. 12, the helical bladed drill 10 according to an exemplary embodiment is also excellent in a state of processing a layer parallel to the scanned circumferential surface. In more detail, the images are compared and reviewed, and in particular, it can be seen that the processing state of the area where the carbon fiber is vertically woven on the circumferential surface has a very clean profile in the case of one embodiment and provides an excellent surface compared to the case of a general tool .

According to an embodiment of the present invention, the third cutting edge 300 additionally provided to the drill bit is characterized in that it provides a cutting edge in which cutting is performed when the tool is retracted in the rear end direction (2). When the drill is lowered for hole processing and cutting is performed, a correspondingly significant cutting load and cutting heat are applied, and the abrasion of the cutting edge can be accelerated by the discharged large number of high hardness carbon fiber chips. That is, assuming that the third cutting edge 300 is formed so that the edge far from the drill tip 900 of the second groove 340 is an acute angle to remove the burr when machining in the downward direction of the drill, Deburring efficiency may be deteriorated due to accumulated heat, and abrasion of a sharp cutting edge may be rapidly caused by a plurality of carbon fiber chips that are discharged. On the other hand, in the case of the third cutting edge 300 provided in the same form as in an embodiment of the present invention, it is relatively less affected by cutting chips and cutting heat, so that the drill tool life can be further extended. have.

The above description is merely illustrative of the technical idea of the present embodiment, and those of ordinary skill in the technical field to which the present embodiment belongs will be able to make various modifications and variations without departing from the essential characteristics of the present embodiment. Accordingly, the present embodiments are not intended to limit the technical idea of the present embodiment, but to explain, and the scope of the technical idea of the present embodiment is not limited by such an embodiment. The scope of protection of this embodiment should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present embodiment.

Claims (6)

A plurality of first cutting edges formed at the tip of the cutting portion having a cylindrical shape having a single diameter;
A plurality of first grooves formed spirally from the first cutting edge and having a first twist angle on the outer peripheral surface of the cutting part;
A first land disposed between the adjacent first grooves;
A second groove formed in a spiral shape on the first land with a second twist angle greater than the first twist angle;
A second land disposed between the adjacent second grooves; And
A third cutting edge disposed in a direction of a rear end of the cutting portion among the spiral edges of the second land and formed to remove burrs when the cutting portion is transferred in a rear end direction;
Containing
Helical bladed drill. The method of claim 1,
Among the spiral edges of the second land, the first edge located in the front end direction of the cutting portion has an obtuse angle,
As a second edge located in the rear end direction of the cutting part among the spiral edges of the second land, the third cutting edge has an acute angle,
The helical-edged drill is formed to remove the burr when retreating after forming a through hole in the workpiece
Helical bladed drill. The method of claim 1,
The second twist angle is in the range of 70 to 80 degrees
Helical bladed drill. The method of claim 1,
The width of the second groove is in the range of 0.5 mm to 1.5 mm
Helical bladed drill. The method of claim 1,
The depth of the second groove is in the range of 1 mm to 2 mm
Helical bladed drill. The method of claim 2,
The first corner has an angular size of 120 degrees to 140 degrees with respect to the outer peripheral surface,
The second edge has an angular size of 65 degrees to 85 degrees with respect to the outer circumferential surface.
Helical bladed drill.

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