Blade tip shaping method
By grinding the rake face of a used cutting tool to maintain a larger contact area and applying a hard coating, the method addresses the inefficiencies of wet blasting, effectively reducing chipping and wear on gear skiving cutters at a lower cost.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- JTEKT CORP
- Filing Date
- 2024-12-26
- Publication Date
- 2026-07-08
AI Technical Summary
Existing methods to suppress chipping and wear on gear skiving cutters, such as wet blasting, are costly and inefficient, and there is a need for a more economical method to shape the cutting edge that reduces chipping and wear.
A method involving grinding the rake face of a used cutting tool to maintain a larger contact area with the workpiece, optionally combined with a hard coating, to enhance support and reduce stress concentrations.
The method effectively suppresses chipping and wear on the cutting edge by maintaining a wider contact area and applying a hard coating, reducing the likelihood of tool breakage and abrasive wear at a lower processing cost.
Smart Images
Figure 2026113944000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a cutting edge forming method.
Background Art
[0002] Patent Document 1 describes a technique related to regrinding the cutting edge of a gear skiving cutter used for gear skiving machining. Regrinding the cutting edge is an operation to sharpen the cutting edge by grinding the rake face adjacent to the end of the cutting edge according to the wear amount of the end of the cutting edge.
[0003] Generally, crater wear is known as wear that occurs on a gear skiving cutter. The rake face near the cutting edge is damaged by receiving frictional force and pressure due to contact with chips during cutting. Crater wear is formed in a concave shape due to this damage. Therefore, a step is formed in a portion corresponding to the edge of crater wear on the rake face near the cutting edge.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] The inventors had developed a technology to suppress chipping of skiving cutters due to the progression of crater wear. As crater wear progresses, larger steps are formed on the cutting edge. The inventors found that as the step size increases, chipping is more likely to occur near the cutting edge, starting from the step. Furthermore, by analyzing the stress generated in the skiving cutter, the inventors found that this chipping was caused by tensile stress generated in the step. The step is a part of the rake face near the cutting edge where the shape changes locally. Therefore, stress tends to concentrate in the step. Consequently, chipping was more likely to occur near the cutting edge.
[0006] Furthermore, the inventors discovered that applying a round honing process to the cutting edge reduces the likelihood of chipping. Round honing shapes the cutting edge into a rounded form. As a result, a cutting edge with round honing makes wider contact with the workpiece surface than a cutting edge without round honing. More specifically, the larger the radius of curvature of the cutting edge, the larger the flank side of the cutting edge makes contact with the workpiece surface. Therefore, the flank side of the cutting edge is more easily supported by the workpiece during cutting. Consequently, compressive stress is generated on the rake face near the cutting edge. As a result, chipping of the skiving cutter is suppressed.
[0007] The inventors were considering using wet blasting to round the cutting edge. However, wet blasting requires extra steps to shape the cutting edge. Therefore, wet blasting increases the cost of processing due to the increased number of steps. Thus, there was a need for a method to shape the cutting edge that would suppress chipping of the skiving cutter at a low cost. [Means for solving the problem]
[0008] This disclosure can be implemented in the following forms:
[0009] (1) According to one embodiment of the present disclosure, a method for shaping the cutting edge of a cutting tool used to perform cutting on a workpiece is provided. This cutting edge shaping method includes: a preparation step of preparing a used cutting tool which has been used in the cutting process and in which the contact portion between the tip of the cutting edge connecting the rake face and the flank face and the workpiece is larger than the contact portion of an unused cutting tool that has not been used in the cutting process; and a grinding step of grinding at least one of the rake face side portion and the flank face side portion of the tip such that, in a cross section showing the shape of the tip perpendicular to the tip portion and the rake face, a portion of the contact portion of the used cutting tool remains on the tip portion which is larger than the size of the contact portion of the unused cutting tool. In this configuration, a portion of the contact area that was in contact with the workpiece remains on the tip of the ground cutting tool. This portion of the contact area is larger than the contact area of the unused cutting tool. As a result, the contact area of the ground cutting tool contacts the workpiece over a wider area than the contact area of the unused cutting tool. In other words, the flank side portion of the tip is more easily supported by the workpiece during cutting. As a result, the cutting edge is less likely to break. The cutting edge shaping method of this disclosure achieves a cutting edge shape that suppresses cutting tool breakage by grinding. As a result, the cutting edge shaping method of this disclosure can shape the cutting edge with fewer steps than the method of shaping the cutting edge by wet blasting. In other words, the cutting edge shaping method of this disclosure can achieve a cutting edge shape that suppresses cutting tool breakage at a lower processing cost than wet blasting. (2) In the above-described method for shaping the cutting edge, the grinding step may be performed by grinding the rake face portion without grinding the relief face portion. In this configuration, the flank-side portion of the contact area of the used cutting tool remains on the ground cutting tool. That is, a portion of the contact area remaining on the cutting tool takes on a shape that conforms to the surface of the workpiece. Therefore, the tip of the cutting tool is more easily supported by the workpiece than a cutting tool that has a portion of its contact area that does not conform to the surface of the workpiece. Thus, the cutting edge shaping method of this disclosure can further suppress chipping of the cutting tool. (3) In the cutting edge shaping method of the above embodiment, the cutting tool is a gear skiving cutter, and the grinding step may be performed such that, in the cross section, the length from the perpendicular line of the rotation axis of the cutting tool that passes through the vertex on the tip side of the rake face, in the direction perpendicular to the line, to the vertex on the tip side of the relief face, is greater than 5 μm. (4) In the above-described method for forming the cutting edge, a coating step may be included after the grinding step, in which a hard film is applied to the surface of the tip. In this embodiment, a hard coating is applied to the cutting edge surface. Abrasive wear occurs at the contact area between the cutting edge and the workpiece due to friction during cutting. The contact area along the surface of the workpiece is prone to wear because it is more susceptible to load from the workpiece. However, by applying a hard coating to the contact area, friction at the cutting edge is suppressed. Therefore, the cutting edge shaping method of this disclosure can suppress the progression of abrasive wear. [Brief explanation of the drawing]
[0010] [Figure 1] This is a perspective view showing the entire cutting tool. [Figure 2] This is an explanatory diagram showing a magnified view of the radial end of the rake face. [Figure 3] This is a cross-sectional view showing a first example of the shape of the cutting edge. [Figure 4] This is a cross-sectional view showing a second example of the blade tip shape. [Figure 5] This is a cross-sectional view of the tip to show the amount of wear on the flank surface. [Figure 6] This is a flowchart showing the cutting edge shaping method of the first embodiment. [Figure 7] This is a cross-sectional view of the tip to show the amount of wear on the flank surface after the grinding process. [Figure 8] This is a flowchart showing a cutting edge shaping method according to a second embodiment. [Modes for carrying out the invention]
[0011] A. First Embodiment: A-1. Overall configuration of cutting tools: FIG. 1 is a perspective view showing the entirety of a cutting tool 10. The cutting tool 10 is a tool for performing gear cutting. Specifically, the cutting tool 10 is a gear skiving cutter.
[0012] In the following description, for ease of understanding of the technology, a direction parallel to the central axis CL of the cutting tool 10 is set as the Z-axis. Note that the central axis CL of the cutting tool 10 is also the rotation axis CL of the gear skiving cutter. When specifying a direction, the positive direction is denoted as “+” and the negative direction as “-”, and positive and negative signs are used in combination in the direction notation. A central axis direction Dcl is set as the direction along the central axis CL, and a circumferential direction Dc is set as the direction around the central axis CL. Further, a radial direction Dr of the central axis CL and a radial direction Drr which is the direction away from the central axis CL among the radial directions Dr are set.
[0013] The cutting tool 10 is cylindrical and is formed by machining to form a spiral groove on the outer surface of a blank. The blank is a cemented carbide and high-speed steel whose outer shape is formed into a substantially rotating body. Also, the side surface in the spiral groove is the flank relief surface 102s described later. The cutting tool 10 includes a plurality of cutting edges 100 and a shaft portion 200.
[0014] The shaft portion 200 supports the plurality of cutting edges 100. The shaft portion 200 is provided coaxially with the plurality of cutting edges 100. The shaft portion 200 is a cylindrical portion integrally provided on the end surface on the opposite side in the Z-axis direction from the rake face 101 of each of the plurality of cutting edges 100.
[0015] The plurality of cutting edges 100 are arranged in an annular shape. Each of the plurality of cutting edges 100 protrudes in the radial direction Drr. More specifically, the plurality of cutting edges 100 are formed in a helical gear shape in which a ridge line extends in the central axis direction Dcl.
[0016] The tool edge 100 includes, as outer surfaces, a front relief surface 102f at the tip, a pair of side relief surfaces 102s on the side surfaces, and a rake face 101. Hereinafter, the front relief surface 102f and the pair of side relief surfaces 102s are collectively referred to as the relief surface 102.
[0017] The front relief surface 102f constitutes an outer surface facing the side in the radial direction Drr of the tool edge 100. The pair of side relief surfaces 102s face the grooves of the plurality of tool edges 100 and are the side surfaces on the circumferential direction Dc side of the tool edge 100. Each of the pair of side relief surfaces 102s is connected to the front relief surface 102f. That is, the pair of side relief surfaces 102s are connected via the front relief surface 102f.
[0018] The rake face 101 constitutes one end face of the tool edge 100 in the central axis direction Dcl. More specifically, the rake face 101 constitutes an end face opposite to the shaft portion 200 in the Z-axis direction.
[0019] FIG. 2 is an explanatory diagram showing an enlarged view of the end portion of the rake face 101 in the radial direction Drr. That is, in FIG. 2, the portion surrounded by the broken line in FIG. 1 is shown. As shown in FIG. 2, the contour of the rake face 101 is composed of one side of each of the pair of side relief surfaces 102s and one side of the front relief surface 102f.
[0020] The tool edge 100 further includes, as a part, a cutting edge portion 110. Note that the cutting edge portion is also simply referred to as the "cutting edge".
[0021] The cutting edge portion 110 is a portion that connects the rake face 101 and the relief surface 102 in the tool edge 100. More specifically, the cutting edge portion 110 includes a central cutting edge 110c that is the intersection line of the rake face 101 and the front relief surface 102f, and a side cutting edge 110s that is the intersection line of the rake face 101 and the side relief surface 102s. That is, the cutting edge portion 110 cuts the workpiece W by the central cutting edge 110c and the side cutting edge 110s.
[0022] Furthermore, the cutting edge portion 110 comprises a tip portion 111 and a portion near the tip 112.
[0023] Figure 3 is a cross-sectional view showing a first example of the shape of the cutting edge portion 110. In Figure 3, a cross-section showing the shape of the tip portion 111 is illustrated perpendicular to the rake face 101. The first example of shape is an example showing the shape of the tip portion 111 of an unused cutting tool 10n that is not used in the cutting tool 10. More specifically, in the first example of shape, the tip portion 111 is rounded. More specifically, in the unused cutting tool 10n, the tip portion 111 has a curved shape that is tangent to the rake face 101 and the relief face 102f. Furthermore, in the first example of shape, a crater wear portion Cr is not formed. The crater wear portion Cr will be explained later.
[0024] The tip portion 111 includes a contact area Ct in the cross-section shown in Figure 3. More specifically, the tip portion 111 is the portion of the cutting edge portion 110 defined by the central cutting edge 110c. The contact area Ct is the portion of the cutting edge portion 110 that contacts the workpiece W. More specifically, in this specification, the contact area Ct is the portion that will come into contact with the workpiece W during cutting, or the portion that was in contact with the workpiece W during cutting.
[0025] The tip 111 of an unused cutting tool 10n may be flat. For example, the tip 111 of an unused cutting tool 10n may be flattened by chamfering, or it may have a flat shape due to grinding by the cutting edge shaping method described later.
[0026] During cutting, the tip portion 111 bites into the workpiece W, causing a portion of the machined surface Ws to be removed. This removed portion flows through the rake face 101 of the cutting edge portion 110 and is eventually discharged from the rake face 101. In other words, this removed portion is a chip.
[0027] Figure 4 is a cross-sectional view showing a second example of the shape of the cutting edge portion 110. In Figure 4, as in Figure 3, a cross-section showing the shape of the tip portion 111 is illustrated perpendicular to the tip portion 111 and the rake face 101. However, the second example of the shape in Figure 4 is an example showing the shape of the tip portion 111 in a used cutting tool 10u that has been used in cutting. More specifically, in the second example of the shape, the contact portion Ct of the tip portion 111 is flat along the machined surface Ws of the workpiece W. This shape is formed by the tip portion 111 being shaved along the machined surface Ws due to abrasive wear during cutting. Furthermore, in the second example of the shape, a crater wear portion Cr is formed. Note that a crater wear portion Cr is not always formed in a used cutting tool 10u. The tip vicinity portion 112 will be explained using Figure 4.
[0028] The tip-preserving portion 112 is the part of the rake face 101 that is on the tip-preserving portion 111 side, excluding the tip-preserving portion 111. More specifically, the tip-preserving portion 112 is the part that is easily subjected to force from chips. In other words, it is also the part where crater wear portions Cr are easily formed on the rake face 101. Specifically, it is located at a position of about 10 to 100 μm from the tip-preserving portion 111.
[0029] The crater wear area Cr is formed when the rake face 101 is damaged by friction and pressure from contact with the chip. The crater wear area Cr is formed in a concave shape due to this damage. More specifically, the chip is cut off by the tip 111 and then begins to flow across the rake face 101. As a result, friction is concentrated at a position away from the tip 111 on the cutting edge 110. This causes the crater wear area Cr to form at a position away from the tip 111. Specifically, the crater wear area Cr tends to form at a distance of about 10 to 100 μm from the tip 111. Due to the formation of the crater wear area Cr, a step Crs is formed on the rake face 101 of the cutting edge 110 at the portion corresponding to the edge of the crater wear area Cr. The height of the step Crs is about 5 μm.
[0030] Figure 5 is a cross-sectional view of the tip portion 111 to show the flank wear amount L. In Figure 5, the tip portion 111 from Figure 4 is enlarged. For ease of understanding the technology, the tip portion 111 is shown at the top of the page. As abrasive wear progresses during cutting, the area of the contact portion Ct expands. As a result, the contact portion Ct becomes flat, as shown in Figure 5. The magnitude of this wear is called the "flank wear amount." That is, the size of the contact portion Ct is expressed by the flank wear amount L. In the cross-section of Figure 5, the flank wear amount L is the length from the perpendicular line Lv of the rotation axis CL of the cutting tool 10 in the vertical direction to the vertex P102 on the tip portion 111 side of the flank surface 102. The perpendicular line Lv of the rotation axis CL of the cutting tool 10 is a straight line passing through the vertex P101 on the tip portion 111 side of the rake surface 101. The flank wear amount L is used as a guideline for replacing the cutting tool 10. For example, in gear skiving, if the flank wear amount L of the cutting tool 10 reaches about 100 μm, the cutting tool 10 may need to be replaced. The flank wear amount L is measured, for example, based on an image taken along a perpendicular line Lv by a camera.
[0031] A2. Blade tip shaping method: Figure 6 is a flowchart of the cutting edge shaping method of the first embodiment. In the cutting edge shaping method, a preparation step S1 is performed first. Preparation step S1 prepares a used cutting tool 10u that has been used in cutting. Specifically, the used cutting tool 10u is a cutting tool 10 that has already been used in gear skiving. That is, preparation step S1 prepares a used cutting tool 10u in which the contact area Ct is larger than the contact area Ct of an unused cutting tool 10. For example, the used cutting tool 10 is a cutting tool 10 in which the flank surface wear amount L has reached about 100 μm.
[0032] In the grinding process S2 shown in Figure 6, grinding is performed so that a portion Ctp of the contact area of the used cutting tool 10u remains on the tip portion 111, which is larger than the size of the contact area Ct of the unused cutting tool 10n. However, the grinding process S2 grinds the portion of the tip portion 111 on the rake face 101 side, without grinding the portion on the flank face 102 side. The grinding is performed, for example, by a tool grinding machine.
[0033] Figure 7 is a cross-sectional view of the tip portion 111 showing the amount of flank wear L2 after grinding step S2. The amount of flank wear L1 before grinding step S2 is shown in Figure 5. Specifically, grinding step S2 in Figure 7 grinds the portion of the tip portion 111 on the rake face 101 side so that the amount of flank wear L remains at 6 μm. Grinding step S2 includes grinding the area near the tip 112. In Figure 7, the area enclosed by the dashed line Pg represents the portion that has been ground from the used cutting tool 10u.
[0034] As a result of the grinding process S2, a portion of the contact area Ctp remains on the tip portion 111. More specifically, of the contact area Ct of the used cutting tool 10, the portion on the flank surface 102 side remains on the ground cutting tool 10. In other words, the portion of the contact area Ctp remaining on the cutting tool 10 takes on a shape that conforms to the surface of the workpiece W.
[0035] Upon completion of the grinding process S2, the cutting tool 10 is reshaped to a state where it can be used again for cutting.
[0036] In this configuration, a portion of the contact area Ctp that was in contact with the workpiece W remains on the tip 111 of the ground cutting tool 10. This portion Ctp is larger than the size of the contact area Ct of the unused cutting tool 10n. As a result, the contact area Ct of the ground cutting tool 10 contacts the workpiece W over a wider area than the contact area Ct of the unused cutting tool 10n. In other words, the portion of the tip 111 on the flank side 102 is more easily supported by the workpiece W during cutting. Therefore, compressive stress is generated on the rake face 101 near the cutting edge 110.
[0037] As a result, the cutting edge portion 110 becomes less prone to chipping. The cutting edge shaping method of this embodiment achieves a cutting edge shape that suppresses chipping of the cutting tool 10 by grinding. Thus, the cutting edge shaping method of this embodiment can shape the cutting edge portion 110 with fewer steps than the method of shaping the cutting edge portion 110 by wet blasting. In other words, the cutting edge shaping method of this embodiment can achieve a cutting edge shape that suppresses chipping of the cutting tool 10 at a lower processing cost than wet blasting.
[0038] Furthermore, in this configuration, the portion of the contact area Ct of the used cutting tool 10 that is on the flank surface 102 side remains on the ground cutting tool 10. That is, a portion of the contact area Ctp remaining on the cutting tool 10 takes on a shape that conforms to the surface of the workpiece W. Therefore, the tip portion 111 is more easily supported by the workpiece W than a cutting tool 10 having a contact area Ct that does not conform to the surface of the workpiece W. Thus, the cutting edge shaping method of this disclosure can further suppress damage to the cutting tool 10.
[0039] B. Second Embodiment: Figure 8 is a flowchart showing the cutting edge shaping method of the second embodiment. In the cutting edge shaping method of the second embodiment, the preparation step S1 and the grinding step S2 are the same as in the first embodiment. In the cutting edge shaping method of the second embodiment, a coating step S3 is further performed. The coating step S3 applies a hard film to the surface of the tip portion 111. For example, the coating is performed by physical vapor deposition. The hard film is, for example, a film made of titanium nitride. The hard film may also be other films such as carbon-titanium nitride or diamond-like carbon.
[0040] In this embodiment, a hard coating is applied to the surface of the cutting edge portion 110. Abrasive wear occurs at the contact area Ct between the cutting edge portion 110 and the workpiece W due to friction during cutting. The contact area Ct along the surface of the workpiece W is susceptible to wear because it is easily subjected to load from the workpiece W. However, by applying a hard coating to the contact area Ct, friction of the cutting edge portion 110 is suppressed. Therefore, the cutting edge forming method of this embodiment can suppress the progression of abrasive wear.
[0041] C. Other embodiments: (C1) In the above embodiment, the cutting tool 10 is a gear skiving cutter. However, the cutting tool 10 may also be a hob cutter used for bobbing or a shaper cutter used for shaping.
[0042] (C2) In the above embodiment, grinding step S2 grinds the portion of the tip 111 on the rake face 101 side without grinding the portion on the flank face 102 side. However, grinding step S2 only needs to grind at least one of the portion of the tip 111 on the rake face 101 side and the portion on the flank face 102 side. That is, grinding step S2 may grind the portion of the tip 111 on the flank face 102 side without grinding the portion on the rake face 101 side. Furthermore, grinding step S2 may grind both the portion of the tip 111 on the rake face 101 side and the portion on the flank face 102 side.
[0043] (C3) In the above embodiment, the grinding step S2 grinds the tip portion 111 so that a flank wear amount L of 6 μm remains. However, in the grinding step S2, it is sufficient that a portion Ctp of the contact area of the used cutting tool 10u remains on the tip portion 111, and that this portion is larger than the size of the contact area Ct of the unused cutting tool 10n. Therefore, in the grinding step S2, grinding may be performed so that a flank wear amount L of about 4 μm remains, or so that a flank wear amount L of about 10 μm remains.
[0044] However, the inventors' stress analysis showed that when the flank wear amount L remains at approximately 6 μm, the tensile stress that causes chipping is reduced more effectively. For this reason, it is desirable that the grinding process S2 be performed such that the flank wear amount L is greater than 5 μm.
[0045] However, in grinding step S2, it is not necessary to grind the entire cross-section of the tip portion 111 so that the flank wear amount L is greater than 5 μm. In other words, the flank wear amount L may be 5 μm or less depending on the location of the cross-section being cut. More specifically, in grinding step S2, it is sufficient to grind the area of the tip portion 111 so that the flank wear amount L is greater than 5 μm in an area greater than half of the tip portion 111.
[0046] (C4) In the above embodiment, the tip portion 111 is defined by the central cutting edge 110c. However, the tip portion 111 may also be defined by the side cutting edges 110s. Therefore, in the grinding step S2, not only the central cutting edge 110c but also the side cutting edges 110s may be ground.
[0047] (C5) In the above embodiment, the expansion of the contact area Ct progresses due to abrasion. However, the expansion of the contact area Ct may also progress due to other forms of wear or damage.
[0048] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features of the embodiments corresponding to the technical features in each form described in the Summary of the Disclosure section can be replaced or combined as appropriate to solve some or all of the above problems, or to achieve some or all of the above effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of symbols]
[0049] 10…Cutting tool, 10n…Unused cutting tool, 10u…Used cutting tool, 100…Tool blade, 101…Rake face, 102…Flap face, 102f…Front flank face, 102s…Side flank face, 110…Cutting edge, 110c…Center cutting edge, 110s…Side cutting edge, 111…Tip, 112…Near tip, 200…Shaft, CL…Central axis, Cr…Crater wear area, Crs…Step, Ct…Contact area, Ctp…Part of contact area, Dc…Circumferential direction, Dcl…Central axis direction, Dr…Radial direction, Drr…Radial direction, L…Flap wear amount, L1…Flap wear amount before grinding, L2…Flap wear amount after grinding, Lv…Perpendicular line, P101, P102…Vertex, W…Workpiece, Ws…Machine surface
Claims
1. A method for shaping the cutting edge of a cutting tool used to perform cutting operations on a workpiece, A preparation step of preparing a used cutting tool that has been used in the aforementioned cutting process, wherein the contact area between the tip of the cutting edge connecting the rake face and the flank face and the workpiece is larger than the contact area of an unused cutting tool that has not been used in the aforementioned cutting process, A cutting edge shaping method, comprising: a grinding step of grinding at least one of the rake face side portion and the relief face side portion of the tip portion such that, in a cross section showing the shape of the tip portion perpendicular to the tip portion and the rake face portion, a portion of the contact area of the used cutting tool remains on the tip portion, and is larger than the size of the contact area of the unused cutting tool.
2. A method for shaping the cutting edge according to claim 1, The grinding step is a cutting edge shaping method in which the rake face portion is ground without grinding the relief face portion.
3. A method for shaping the cutting edge according to claim 2, The cutting tool is a gear skiving cutter, The grinding step is a cutting edge shaping method in which, in the cross-section, the length from the perpendicular line of the rotation axis of the cutting tool that passes through the vertex on the tip side of the rake face, in a direction perpendicular to the perpendicular line, is greater than 5 μm, to the vertex on the tip side of the relief face.
4. A cutting edge shaping method according to claim 3, further, A method for shaping a cutting edge, comprising a coating step of applying a hard film to the surface of the tip portion after the grinding step.