Position Detection Method for Cutting Tool

Abstract

The present invention provides a method for detecting the position of a cutting tool, reducing the amount of workpieces used for detecting the position of the cutting tool. This method uses a cutting device to detect the lower end position of the cutting tool. The cutting device has a holding table and a cutting unit. The holding table holds the workpiece, and the cutting unit mounts the cutting tool that cuts the workpiece held by the holding table in a rotatable state. The method for detecting the position of the cutting tool has the following steps: a groove forming step of further cutting the cutting tool into a workpiece having a first groove to form a second groove on the workpiece, wherein the first groove is formed by cutting the cutting tool into the workpiece, and one end portion in the width direction of the second groove does not overlap with the first groove and the other end portion in the width direction overlaps with the first groove; and a calculating step of calculating the lower end position of the cutting tool based on the length of one end portion in the width direction of the second groove formed in the workpiece.

Description

Technical Field

[0001] The present invention relates to a method for detecting the position of a cutting tool that cuts a workpiece (workpiece to be processed). Background Art

[0002] In the manufacturing process of device chips, a wafer is used in which devices such as ICs (Integrated Circuits) and LSIs (Large Scale Integrations) are respectively formed in a plurality of regions divided by a plurality of dividing predetermined lines (scribe lines) arranged in a grid pattern. By dividing the wafer along the dividing predetermined lines, a plurality of device chips each having a device can be obtained. The device chips are mounted on various electronic devices represented by mobile phones, personal computers, and the like.

[0003] In the division of a wafer, for example, a cutting device is used. The cutting device includes: a holding table that holds the wafer; and a cutting unit that is equipped with an annular cutting tool for cutting the wafer. By rotating the cutting tool and cutting into the wafer, the wafer is cut and divided.

[0004] In addition, in recent years, with the miniaturization of electronic devices, thinning of device chips has been required. Therefore, sometimes a process of thinning the wafer is performed before dividing the wafer. For example, by performing a grinding process on the back side of the wafer before division, the wafer is thinned. By dividing the wafer after thinning it, a thinned device chip can be obtained.

[0005] In addition, a so-called chamfering process is performed on the wafer, that is, the outer peripheral portion of the wafer is ground so that the shape of the outer peripheral edge (side surface) of the wafer becomes arc-shaped. When the wafer on which the chamfering process has been performed is ground to be thinned, the outer peripheral portion of the wafer becomes a sharp shape (blade shape). When the outer peripheral portion of the wafer becomes a blade shape, it is easy to generate notches or cracks in the outer peripheral portion of the wafer, and the wafer may be damaged.

[0006] Therefore, before grinding the wafer to thin it, the outer peripheral edge of the wafer is cut in a ring shape from the front side using a cutting tool, and a process called edge trimming for forming a stepped portion in the outer peripheral portion of the wafer is performed (for example, refer to Patent Document 1). If this edge trimming is performed, when the back side of the wafer is then ground to thin the wafer, the outer peripheral portion of the wafer will not become a blade shape. Thereby, damage to the wafer is prevented.

[0007] In the above-described edge trimming, it is sometimes required to precisely adjust the cutting depth of the cutting tool into the wafer (the distance from the front surface of the wafer to the lower end of the cutting tool). However, the cutting depth sometimes slightly varies depending on the material of the wafer, processing conditions, the operating state of the cutting device, etc. If only the value of the desired cutting depth is input to the cutting device, the wafer may not be cut at the desired cutting depth.

[0008] Therefore, the following inspection is sometimes carried out: The cutting tool is made to cut into a test workpiece (workpiece to be machined) to form a groove (cutting groove) on the workpiece, and the lower end position of the cutting tool is calculated based on the length of this groove (for example, refer to Patent Document 2). By carrying out this inspection before cutting the wafer with the cutting tool, the cutting depth of the cutting tool can be adjusted according to the actual lower end position of the cutting tool, thereby improving the accuracy of the cutting depth.

[0009] Patent Document 1: Japanese Patent Laid-Open No. 2000-173961

[0010] Patent Document 2: Japanese Patent Laid-Open No. 2002-59365

[0011] As described above, when machining a workpiece with a cutting tool, an inspection for detecting the lower end position of the cutting tool is carried out. This inspection includes the following steps: The cutting tool is made to cut into a test workpiece (workpiece for forming a cutting groove) to form a cutting groove on the workpiece for forming a cutting groove. Moreover, in order to save the workpiece for forming a cutting groove, multiple inspections are carried out using a single workpiece for forming a cutting groove. In this case, multiple cutting grooves are formed on the workpiece for forming a cutting groove.

[0012] Here, in the above-described inspection, the profile of the groove formed in the workpiece for forming a cutting groove is confirmed, and the lower end position of the cutting tool is calculated based on the length of this groove. Therefore, in the case of carrying out multiple inspections using a single workpiece for forming a cutting groove, the newly formed cutting groove is formed so as not to overlap with the cutting grooves already formed in the workpiece for forming a cutting groove. As a result, the number of cutting grooves that can be formed on a single workpiece for forming a cutting groove is limited, and the workpiece for forming a cutting groove needs to be frequently replaced.

[0013] In particular, in the above-described edge trimming, a relatively thick cutting tool with a width of about 1 mm to 3 mm is mostly used. When detecting the position of such a cutting tool, the width of the cutting groove formed in the workpiece for forming a cutting groove also becomes larger, and the number of cutting grooves that can be formed on a single workpiece for forming a cutting groove is further limited. As a result, the usage amount of the workpiece for forming a cutting groove increases and the cost rises. Summary of the Invention

[0014] The present invention has been completed in view of the above problems, and an object thereof is to provide a method for detecting the position of a cutting tool that can reduce the amount of workpieces used in detecting the position of the cutting tool.

[0015] According to one aspect of the present invention, there is provided a method for detecting the position of a cutting tool, which uses a cutting device to detect the lower end position of the cutting tool. The cutting device includes a holding table for holding a workpiece and a cutting unit for rotatably mounting the cutting tool for cutting the workpiece held by the holding table. The method for detecting the position of the cutting tool includes the following steps: a groove forming step of further cutting the cutting tool into the workpiece having a first groove to form a second groove in the workpiece, where the first groove is formed by cutting the cutting tool into the workpiece, and one end portion in the width direction of the second groove does not overlap with the first groove and the other end portion in the width direction overlaps with the first groove; and a calculating step of calculating the lower end position of the cutting tool based on the length of one end portion in the width direction of the second groove formed in the workpiece.

[0016] In the method for detecting the position of a cutting tool according to one aspect of the present invention, the cutting tool is further cut into the workpiece on which the first groove has already been formed to form a second groove in the workpiece. One end portion in the width direction of the second groove does not overlap with the first groove and the other end portion in the width direction overlaps with the first groove. Thus, more grooves can be formed on one workpiece, thereby reducing the amount of workpieces used. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a perspective view showing the cutting device.

[0018] Figure 2 is a front view showing the holding table and the cutting unit.

[0019] Figure 3 (A) of is a top view showing a part of the workpiece cut by the first cutting tool, Figure 3 and (B) of is a top view showing a part of the workpiece cut by the second cutting tool.

[0020] Figure 4 (A) of is a top view showing the workpiece formed with the first groove, Figure 4 and (B) of is a top view showing the workpiece formed with the second groove, Figure 4 and (C) of is a top view showing the workpiece formed with the third groove.

[0021] Figure 5 is a flowchart showing the operation of the control unit.

[0022] Figure 6It is a top view of a workpiece after detecting the lower end position of a cutting tool multiple times.

[0023] Figure 7 (A) thereof is a top view of a workpiece formed with a first groove, Figure 7 (B) thereof is a top view of a workpiece formed with a second groove, Figure 7 (C) thereof is a top view of a workpiece formed with a third groove, Figure 7 (D) thereof is a top view of a workpiece formed with a fourth groove.

[0024] Figure 8 (A) thereof is a top view of a workpiece formed with a third groove in a manner overlapping with the first and second grooves, Figure 8 (B) thereof is a top view of a workpiece formed with a fourth groove in a manner overlapping with the first and second grooves.

[0025] Reference Numeral Explanation

[0026] 11: Workpiece (Workpiece to be Machined); 11A: Upper Workpiece; 11B: Lower Workpiece; 13: Device; 15: Stacked Workpiece; 21: Workpiece (Workpiece to be Machined); 21a: Front Face; 23A, 23B: Grooves (Cutting Grooves); 23Aa, 23Ab, 23Ba, 23Bb: End Portions (End Edges); 2: Cutting Device; 4: Base; 6: Moving Mechanism; 8: X-Axis Guide Rail; 10: X-Axis Moving Worktable; 12: X-Axis Ball Screw; 14: X-Axis Pulse Motor; 16: Worktable Base; 18: Holding Worktable (Chuck Worktable); 18a: Holding Surface; 20: Support Table; 22: Holding Worktable (Sub-Chuck Worktable); 22a: Holding Surface; 24: Water Tank; 26: Support Structure; 28: Moving Mechanism (Moving Unit); 30: Y-Axis Guide Rail; 32: Y-Axis Moving Plate; 34: Y-Axis Ball Screw; 36: Y-Axis Pulse Motor; 38: Z-Axis Guide Rail; 40: Z-Axis Moving Plate; 42: Z-Axis Ball Screw; 44: Z-Axis Pulse Motor; 46A, 46B: Cutting Units; 48: Imaging Unit (Camera); 50: Housing; 52: Spindle (Rotating Shaft); 54A, 54B: Cutting Tools; 54Aa, 54Ab, 54Ba, 54Bb: Side Surfaces (End Portions); 56: Nozzle; 58: Display Unit (Display Device); 60: Control Unit (Control Unit); 62: Processing Unit; 64: Storage Unit. Detailed Embodiment

[0027] Hereinafter, an embodiment of one aspect of the present invention will be described with reference to the drawings. First, a structural example of a cutting device for a method of detecting the position of a cutting tool that can be used in the present embodiment will be described. Figure 1 It is a perspective view showing the cutting device 2.

[0028] The cutting device 2 has a base 4 on which each structural element constituting the cutting device 2 is mounted, and a moving mechanism (moving unit) 6 is provided on the upper surface side of the base 4. The moving mechanism 6 has a pair of X-axis guide rails 8 arranged along the X-axis direction (machining feed direction, front-rear direction), and an X-axis moving table 10 is mounted on the pair of X-axis guide rails 8 in a state capable of sliding along the X-axis guide rails 8.

[0029] A nut portion (not shown) is provided on the lower surface (back surface) side of the X-axis moving table 10, and an X-axis ball screw 12 arranged along the pair of X-axis guide rails 8 is screwed onto the nut portion. In addition, an X-axis pulse motor 14 is connected to one end of the X-axis ball screw 12. When the X-axis ball screw 12 is rotated by the X-axis pulse motor 14, the X-axis moving table 10 moves in the X-axis direction along the X-axis guide rails 8. In addition, a detector (not shown) is provided on the moving mechanism 6, and this detector detects the position of the X-axis moving table 10 in the X-axis direction.

[0030] A cylindrical worktable base 16 is provided on the upper surface (front surface) side of the X-axis moving table 10. In addition, a holding worktable (chuck worktable) 18 is provided on the upper part of the worktable base 16, and this holding worktable 18 holds a workpiece (workpiece to be machined) 11 which is an object to be machined by the cutting device 2.

[0031] The upper surface of the holding worktable 18 constitutes a holding surface 18a for holding the workpiece 11. The holding surface 18a is formed substantially parallel to the X-axis direction and the Y-axis direction (indexing feed direction, left-right direction), and is connected to a suction source such as an ejector (not shown) via a flow path (not shown) formed inside the holding worktable 18 and the like.

[0032] The X-axis moving table 10 is moved in the X-axis direction by the moving mechanism 6, whereby the machining feed of the holding worktable 18 is performed. In addition, the holding worktable 18 is connected to a rotational drive source such as a motor (not shown), and this rotational drive source rotates the holding worktable 18 about a rotation axis substantially parallel to the Z-axis direction (vertical direction, up-down direction). In addition, a transfer mechanism (not shown) for transferring the workpiece 11 onto the holding worktable 18 is provided near the holding worktable 18.

[0033] A plate-shaped support table 20 is fixed to the worktable base 16 so as to surround the worktable base 16. Moreover, a holding worktable (sub-chuck worktable) 22 for holding a workpiece (workpiece to be machined) 21 is provided on the upper surface side of the support table 20. The workpiece 21 is a workpiece for forming a cutting groove used when detecting the lower end positions of the cutting tools 54A and 54B described later.

[0034] The upper surface of the holding table 22 constitutes a holding surface 22a for holding the workpiece 21. The holding surface 22a is formed substantially parallel to the X-axis direction and the Y-axis direction, and is connected to a suction source (not shown) such as an ejector via a flow path (not shown) formed inside the holding table 22 and the like.

[0035] A water tank 24 is provided around the X-axis moving table 10. The water tank 24 temporarily stores waste liquid such as waste liquid of cutting fluid (pure water, etc.) for cutting. The waste liquid stored inside the water tank 24 is discharged to the outside of the cutting device 2 via a drain pipe (not shown) and the like.

[0036] In addition, a gantry support structure 26 is disposed on the upper surface side of the base 4 so as to straddle the moving mechanism 6. A pair of moving mechanisms (moving units) 28 are provided at the upper part of the front surface side of the support structure 26. Specifically, a pair of Y-axis guide rails 30 are fixed along the Y-axis direction on the front surface side of the support structure 26, and flat plate-shaped Y-axis moving plates 32 respectively included in the pair of moving mechanisms 28 are mounted on the pair of Y-axis guide rails 30 in a state capable of sliding along the Y-axis guide rails 30. In addition, a pair of Y-axis ball screws 34 are provided along the Y-axis guide rails 30 between the pair of Y-axis guide rails 30.

[0037] A nut portion (not shown) is provided on the rear surface (back surface) side of the Y-axis moving plate 32, and the Y-axis ball screw 34 is screwed onto the nut portion. In addition, Y-axis pulse motors 36 are respectively connected to one end portions of the pair of Y-axis ball screws 34. When the Y-axis ball screw 34 is rotated by the Y-axis pulse motor 36, the Y-axis moving plate 32 moves in the Y-axis direction along the Y-axis guide rail 30. In addition, a detector (not shown) is provided on the moving mechanism 28, and the detector detects the position of the Y-axis moving plate 32 in the Y-axis direction.

[0038] A pair of Z-axis guide rails 38 are respectively disposed along the Z-axis on the front surface (front surface) side of the Y-axis moving plate 32. A flat plate-shaped Z-axis moving plate 40 is mounted on the Z-axis guide rails 38 in a state capable of sliding along the Z-axis guide rails 38. In addition, a Z-axis ball screw 42 is provided along the Z-axis guide rails 38 between the pair of Z-axis guide rails 38.

[0039] A nut portion (not shown) is provided on the rear surface (back surface) side of the Z-axis moving plate 40, and the Z-axis ball screw 42 is screwed onto the nut portion. In addition, one end portion of the Z-axis ball screw 42 is connected to a Z-axis pulse motor 44. When the Z-axis ball screw 42 is rotated by the Z-axis pulse motor 44, the Z-axis moving plate 40 moves in the Z-axis direction along the Z-axis guide rail 38.

[0040] A cutting unit 46A for cutting the workpiece 11 is fixed to the lower part of the Z-axis moving plate 40 of one moving mechanism 28. In addition, a cutting unit 46B for cutting the workpiece 11 is fixed to the lower part of the Z-axis moving plate 40 of the other moving mechanism 28. Imaging units (cameras) 48 are respectively provided at positions adjacent to the cutting units 46A and 46B, and the imaging units 48 image the workpiece 11 held by the holding table 18 or the workpiece 21 held by the holding table 22.

[0041] By moving the Y-axis moving plate 32 in the Y-axis direction, the cutting units 46A and 46B and the imaging units 48 move in the Y-axis direction. In addition, by moving the Z-axis moving plate 40 in the Z-axis direction, the cutting units 46A and 46B and the imaging units 48 move up and down, moving in a direction substantially perpendicular to the holding surfaces 18a of the holding table 18 and the holding surfaces 22a of the holding table 22.

[0042] Figure 2 is a front view showing the holding tables 18 and 22 and the cutting units 46A and 46B. In addition, in Figure 2 for ease of explanation, the holding table 18 and the holding table 22 are shown at separate positions.

[0043] The cutting units 46A and 46B respectively have cylindrical housings 50 supported by the moving mechanism 28 (see Figure 1 ). A main shaft (rotating shaft) 52 arranged in the Y-axis direction is housed in the housing 50. The front end portion (one end side) of the main shaft 52 projects to the outside of the housing 50. In addition, the base end portion (the other end side) of the main shaft 52 is connected to a rotation drive source such as an electric motor (not shown), and the rotation drive source rotates the main shaft 52 about a rotation axis substantially parallel to the Y-axis direction.

[0044] A ring-shaped cutting tool 54A (first cutting tool) is mounted on the front end portion of the main shaft 52 of the cutting unit 46A. In addition, a ring-shaped cutting tool 54B (second cutting tool) is mounted on the front end portion of the main shaft 52 of the cutting unit 46B. The cutting tools 54A and 54B are arranged to face each other.

[0045] The cutting tool 54A mounted on the cutting unit 46A has: a side surface (end portion) 54Aa, which is located on the side of the cutting unit 46A opposite to the housing 50 and the main shaft 52 (the side of the cutting unit 46B, Figure 2 the right side in Figure 2 ); and a side surface (end portion) 54Ab, which is located on the side of the housing 50 and the main shaft 52 of the cutting unit 46A (

[0046] In addition, the cutting tool 54B mounted on the cutting unit 46B has: a side surface (end portion) 54Ba, which is located on the side of the cutting unit 46B opposite to the housing 50 and the main shaft 52 (the cutting unit 46A side, Figure 2 the left side in the figure); and a side surface (end portion) 54Bb, which is located on the housing 50 and main shaft 52 side of the cutting unit 46B ( Figure 2 the right side in the figure).

[0047] As the cutting tools 54A and 54B, for example, hub-type cutting tools in which a ring-shaped base formed of metal or the like and a ring-shaped cutting edge formed along the outer peripheral edge of the base are integrally formed are used. The cutting edge of the hub-type cutting tool is constituted by an electroformed grinding tool, and abrasive grains formed of diamond or the like are fixed to the electroformed grinding tool by a bonding material such as a nickel plating layer.

[0048] However, the material of the abrasive grains and the bonding material of the cutting tools 54A and 54B, the particle size of the abrasive grains, etc. are not limited, and are appropriately selected according to the material of the workpieces 11 and 21 to be processed, the processing conditions, etc. In addition, the cutting tools 54A and 54B may also be washer-type cutting tools constituted by a ring-shaped cutting edge in which abrasive grains are fixed by a bonding material formed of metal, ceramic, resin, or the like.

[0049] Nozzles 56 for supplying a cutting fluid such as pure water to the cutting tools 54A and 54B are respectively provided on the cutting units 46A and 46B (refer to Figure 1 ). When the workpieces 11 and 21 are cut using the cutting tools 54A and 54B, the cutting fluid is supplied from the nozzles 56. As a result, the workpieces 11 and 21 and the cutting tools 54A and 54B are cooled, and the chips (cutting chips) generated by cutting are washed away.

[0050] Figure 1 and Figure 2 The cutting device 2 shown has two sets of cutting units 46A and 46B, and is a so-called face-to-face biaxial cutting device in which a pair of cutting tools 54A and 54B are arranged facing each other. However, the number of cutting units provided in the cutting device 2 may also be one set.

[0051] A display unit (display device) 58 for displaying various information related to the cutting device 2 is provided on the front surface side of the cutting device 2. For example, the display unit 58 is a display, and displays information related to the processing of the workpieces 11 and 21 (processing conditions, processing status, etc.), images of the workpieces 11 and 21 before, during, or after processing, etc.

[0052] In addition, the display unit 58 may also be a touch panel. In this case, the touch panel also functions as an input unit (input device) for inputting various information to the cutting device 2. Moreover, operation keys (such as a keyboard and numeric keys) are displayed together with information related to the cutting device 2 on the touch panel. An operator can input information such as machining conditions to the cutting device 2 through touch operations on the touch panel.

[0053] Furthermore, the cutting device 2 has a control unit (control unit) 60, which is connected to each structural element (the moving mechanism 6, the holding table 18, the holding table 22, the moving mechanism 28, the cutting units 46A and 46B, the imaging unit 48, the display unit 58, etc.) that constitutes the cutting device 2. The control unit 60 controls the operations of the respective structural elements of the cutting device 2.

[0054] For example, the control unit 60 is composed of a computer, which includes: a processing unit 62 that performs various processes (such as operations) required for the operation of the cutting device 2; and a storage unit 64 that stores various information (data, programs, etc.) for the processing by the processing unit 62. The processing unit 62 is configured to include a processor such as a CPU (Central Processing Unit). In addition, the storage unit 64 is composed of memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory). The processing unit 62 and the storage unit 64 are connected to each other via a bus.

[0055] The workpiece 11 is machined by the cutting device 2. The workpiece 11 is, for example, a disk-shaped silicon wafer. The workpiece 11 is divided into a plurality of regions by dividing predetermined lines (scribe lines) arranged in a grid pattern in a crosswise manner, and devices 13 such as ICs and LSIs are formed on the upper surface (front side) of each region.

[0056] However, there are no restrictions on the material, shape, structure, size, etc. of the workpiece 11. For example, the workpiece 11 may also be a wafer of any shape formed of a semiconductor other than silicon (such as GaAs, InP, GaN, SiC, etc.), glass, ceramic, resin, metal, etc. In addition, there are no restrictions on the type, number, shape, structure, size, arrangement, etc. of the devices 13, and the devices 13 may not be formed on the workpiece 11. Furthermore, the workpiece 11 may also be a packaged substrate formed by covering a plurality of device chips mounted on a rectangular substrate with a sealing material (molding resin) formed of resin.

[0057] When the cutting tool 54A or the cutting tool 54B is inserted into the workpiece 11 and the workpiece 11 is divided along the division predetermined line, a plurality of device chips each having the device 13 are formed. In addition, when the workpiece 11 before division is thinned by performing grinding or lapping on the workpiece 11, the device chips obtained by dividing the workpiece 11 later can be thinned.

[0058] In addition, the so-called chamfering process is performed on the workpiece 11 (refer to Figure 2 ), that is, the outer peripheral portion of the workpiece 11 is ground so that the shape of the outer peripheral edge (side surface) of the workpiece 11 becomes an arc shape. When the workpiece 11 subjected to this chamfering process is ground to be thinned, the outer peripheral portion of the workpiece 11 becomes a shape (blade shape) that is sharp toward the outside in the radial direction of the workpiece 11. Moreover, when the outer peripheral portion of the workpiece 11 becomes a blade shape, damage such as notches or cracks is likely to occur in the outer peripheral portion of the workpiece 11.

[0059] Therefore, before the workpiece 11 is ground to be thinned, a process called edge trimming is performed in which the outer peripheral edge of the workpiece 11 is cut in a ring shape. If this edge trimming is performed, when the workpiece 11 is ground to be thinned later, the outer peripheral portion of the workpiece 11 will not become a blade shape. Thereby, damage to the outer peripheral portion of the workpiece 11 is suppressed.

[0060] Edge trimming is performed by cutting the outer peripheral portion of the workpiece 11 using the cutting tool 54A or the cutting tool 54B. Hereinafter, as an example, the case of performing edge trimming using the cutting tool 54A on the upper workpiece 11A in the laminated workpiece 15 (refer to Figure 2 ) obtained by laminating two workpieces 11 (upper workpiece 11A and lower workpiece 11B) will be described. In this case, as the cutting tool 54A, for example, a cutting tool having a cutting edge thickness of 1 mm or more and 3 mm or less is used.

[0061] When processing the laminated workpiece 15, as Figure 2 shown, the laminated workpiece 15 is held by the holding table 18. Specifically, the laminated workpiece 15 is arranged on the holding table 18 such that the upper surface side of the upper workpiece 11A is exposed upward and the lower surface side of the lower workpiece 11B faces the holding surface 18a. In this state, when the negative pressure of the suction source acts on the holding surface 18a, the laminated workpiece 15 is attracted and held by the holding table 18.

[0062] Next, the outer peripheral portion of the upper workpiece 11A is cut using the cutting tool 54A. Specifically, first, the height of the cutting unit 46A is adjusted by the moving mechanism 28 (refer to Figure 1 ) so that the lower end of the cutting tool 54A is disposed at the same height as the boundary between the upper workpiece 11A and the lower workpiece 11B.

[0063] In addition, the position of the cutting unit 46A in the Y-axis direction (indexing feed direction) is adjusted by the moving mechanism 28 (see Figure 1 ) so that the cutting tool 54A overlaps with the outer peripheral portion of the upper workpiece 11A in the front view. Then, while rotating the cutting tool 54A, the holding table 18 is moved in the X-axis direction (machining feed direction) (machining feed), and the holding table 18 and the cutting tool 54A are relatively moved. Thereby, the cutting tool 54A cuts into a part of the outer peripheral portion of the upper workpiece 11A.

[0064] Moreover, in a state where the cutting tool 54A cuts into a part of the outer peripheral portion of the upper workpiece 11A, the movement (machining feed) of the holding table 18 is stopped, and the holding table 18 is rotated. As a result, the outer peripheral portion of the upper workpiece 11A is cut in a ring shape by the cutting tool 54A and removed. As a result, the side surface of the upper workpiece 11A is machined into a planar shape substantially parallel to the thickness direction of the upper workpiece 11A, and edge trimming is performed on the upper workpiece 11A.

[0065] In addition, in the above, an example of machining the workpiece 11 with the cutting tool 54A mounted on the cutting unit 46A has been described, but the order is the same when machining the workpiece 11 with the cutting tool 54B mounted on the cutting unit 46B. In addition, the content of machining using the cutting tools 54A and 54B is not limited to the division and edge trimming of the workpiece 11.

[0066] Here, the cutting depth of the cutting tools 54A and 54B may vary slightly depending on the material of the workpiece 11, machining conditions, operating conditions of the cutting device 2, etc. If only the value of the desired cutting depth is input to the cutting device 2, the workpiece 11 may not be cut at the desired cutting depth. Here, in the cutting device 2, the cutting tools 54A and 54B are made to cut into the test workpiece 21 held by the holding table 22 (see Figure 2 ), and an inspection for confirming the lower end position (cutting depth) of the cutting tools 54A and 54B is performed. Then, based on the result of this inspection, the height position (cutting depth) of the cutting tools 54A and 54B is adjusted.

[0067] The workpiece 21 is, for example, a member formed in a rectangular parallelepiped shape and is made of a material that can be cut by the cutting tools 54A and 54B. However, the shape of the workpiece 21 is not limited. In addition, examples of the material of the workpiece 21 are the same as those of the workpiece 11.

[0068] When detecting the lower end position of the cutting tool 54A, first, adjust the position of the cutting unit 46A so that the cutting tool 54A is disposed directly above the workpiece 21. Then, while rotating the cutting tool 54A, lower the cutting unit 46A to a specified height position to cause the cutting tool 54A to cut into the front surface 21a side of the workpiece 21. Then, raise the cutting unit 46A to separate the cutting tool 54A from the workpiece 21.

[0069] Figure 3 (A) of FIG. is a plan view showing a part of the workpiece 21 cut by the cutting tool 54A. When the workpiece 21 is cut by the cutting tool 54A, a groove (cutting groove) 23A having a specified depth is formed on the front surface 21a side of the workpiece 21. Figure 3 (A) of FIG. shows an example in which a groove 23A having a rectangular shape in plan view is formed on the workpiece 21.

[0070] The width of the groove 23A corresponds to the width of the front end portion (cutting edge) of the cutting tool 54A. In addition, the groove 23A includes end portions (end edges) 23Aa, 23Ab in the width direction ( Figure 3 the left - right direction in (A) of FIG.) of the groove 23A. The end portion 23Aa corresponds to the area cut by the side surface 54Aa of the cutting tool 54A (refer to Figure 2 ), and the end portion 23Ab corresponds to the area cut by the side surface 54Ab of the cutting tool 54A (refer to Figure 2 ).

[0071] On the other hand, when inspecting the lower end position of the cutting tool 54B, cut the workpiece 21 with the cutting tool 54B in the same order. Figure 3 (B) of FIG. is a plan view showing a part of the workpiece 21 cut by the cutting tool 54B. When the workpiece 21 is cut by the cutting tool 54B, a groove (cutting groove) 23B having a specified depth is formed on the front surface 21a side of the workpiece 21.

[0072] The width of the groove 23B corresponds to the width of the front end portion (cutting edge) of the cutting tool 54B. In addition, the groove 23B includes end portions (end edges) 23Ba, 23Bb in the width direction ( Figure 3 the left - right direction in (B) of FIG.) of the groove 23B. The end portion 23Ba corresponds to the area cut by the side surface 54Ba of the cutting tool 54B (refer to Figure 2 ), and the end portion 23Bb corresponds to the area cut by the side surface 54Bb of the cutting tool 54B (refer to Figure 2 ).

[0073] When the cutting tools 54A and 54B cut into the workpiece 21, the lower end positions of the cutting tools 54A and 54B can be calculated respectively according to the lengths of the grooves 23A and 23B. Specifically, when the radii of the cutting tools 54A and 54B are set as R A and R B respectively, and the lengths of the grooves 23A and 23B are set as L A and L B respectively, the lower end position D A (the cutting depth of the cutting tool 54A, the depth of the groove 23A) and the lower end position D B (the cutting depth of the cutting tool 54B, the depth of the groove 23B) are represented by Mathematical Formula (1) and Mathematical Formula (2) respectively.

[0074]

Mathematical Formula 1

[0075]

[0076]

Mathematical Formula 2

[0077]

[0078] Therefore, by forming the grooves 23A and 23B on the workpiece 21 and measuring the lengths L A and L B , the lower end positions D A and D B of the cutting tools 54A and 54B can be calculated. Then, according to the calculated lower end positions of the cutting tools 54A and 54B, the height positions of the cutting tools 54A and 54B when cutting the workpiece 11 which is the original machining object are adjusted, so that the accuracy of the cutting depth can be improved.

[0079] As the lengths L A and L B used to calculate the lower end positions D A and D B , the lengths at any positions in the width directions of the grooves 23A and 23B can be used. Therefore, the lower end position of the cutting tool 54A can be calculated according to the length L A (refer to (A) of Figure 3 ) of the end 23Aa of the groove 23A, and the lower end position of the cutting tool 54B can be calculated according to the length L B (refer to (B) of Figure 3 ) of the end 23Ba of the groove 23B.

[0080] In particular, in the case of performing edge trimming on the workpiece 11, the side surface 54Aa side of the cutting tool 54A or the side surface 54Ba side of the cutting tool 54B cuts into the outer peripheral portion of the workpiece 11. Therefore, the values of the cutting depths of the end portion 23Aa of the groove 23A and the end portion 23Ba of the groove 23B are particularly important.

[0081] Therefore, in the present embodiment, the lower end position of the cutting tool 54A is calculated based on the end portion 23Aa of the groove 23A, and the lower end position of the cutting tool 54B is calculated based on the end portion 23Ba of the groove 23B. Hereinafter, a specific example of the operation of the cutting device 2 when detecting the lower end positions of the cutting tools 54A and 54B will be described. In addition, here, as an example, the case of detecting the lower end position of the cutting tool 54A will be described.

[0082] In the method for detecting the position of the cutting tool in the present embodiment, after detecting the lower end position of the cutting tool 54A based on the groove 23A formed in the workpiece 21, another groove 23A is further formed on the same workpiece 21, and the lower end position of the cutting tool 54A is detected. That is, the detection of the lower end position of the cutting tool 54A is performed multiple times using the same workpiece 21.

[0083] When detecting the lower end position of the cutting tool 54A, first, a groove 23A is formed in the workpiece 21 (groove forming step). Specifically, the cutting tool 54A is caused to cut into the front surface 21a side of the workpiece 21 in the above-described order, and the first groove 23A is formed on the front surface 21a side of the workpiece 21.

[0084] Figure 4 (A) shows a plan view of the workpiece 21 in which the first groove 23A (groove 23A1) is formed. The groove 23A1 includes: an end portion (end edge) 23Aa1, which corresponds to the side surface 54Aa of the cutting tool 54A (refer to Figure 2 ); and an end portion (end edge) 23Ab1, which corresponds to the side surface 54Ab of the cutting tool 54A (refer to Figure 2 ).

[0085] Next, the lower end position of the cutting tool 54A is calculated based on the length of the end portion 23Aa1 of the groove 23A1 (calculation step). In the calculation step, first, the front surface 21a side of the workpiece 21 held by the holding table 22 is photographed by the photographing unit 48 (refer to Figure 1 ). At this time, the holding table 22 is moved by the moving mechanism 6, and the photographing unit 48 is moved by the moving mechanism 28, so as to perform alignment between the workpiece 21 and the photographing unit 48. Moreover, the groove 23A1 is displayed in the image (photographed image) obtained by photographing.

[0086] Next, based on the captured image obtained by the imaging unit 48, the lower end position of the cutting tool 54A is detected. Specifically, the length of the end portion 23Aa1 of the groove 23A1 shown in the captured image is measured, and the lower end position of the cutting tool 54A is calculated based on the length of the end portion 23Aa1. For example, the processing unit 62 and the storage unit 64 (refer to Figure 1 ) included in the control unit 60 are used to measure the length of the end portion 23Aa1 and calculate the lower end position of the cutting tool 54A.

[0087] Figure 5 is a flowchart showing the operation of the control unit 60 when detecting the lower end position of the cutting tool 54A. When the workpiece 21 is imaged by the imaging unit 48, the image obtained by imaging (captured image) is output to the control unit 60 (step S1).

[0088] Then, based on the input captured image, the control unit 60 measures the length of the end portion 23Aa1 of the groove 23A1 formed in the workpiece 21 (step S2). The length of the end portion 23Aa1 is measured, for example, by performing image processing on the captured image. Specifically, the processing unit 62 performs edge detection processing on the captured image to determine the contour of the groove 23A1, and calculates the difference in coordinates of both ends of the end portion 23Aa1 of the groove 23A1 ( Figure 4 the upper end and the lower end in (A) of). Thereby, the length of the end portion 23Aa1 is obtained.

[0089] However, the method for measuring the length of the end portion 23Aa1 of the groove 23A1 is not limited. For example, the captured image including the groove 23A1 may be enlarged and displayed on the display unit 58 (refer to Figure 1 ), and the length of the end portion 23Aa1 may be actually measured.

[0090] Next, the control unit 60 calculates the lower end position of the cutting tool 54A based on the calculated length of the end portion 23Aa1 of the groove 23A1 (step S3). Specifically, the above mathematical formula (1) and the radius R of the cutting tool 54A are pre-stored in the storage unit 64 A . Then, when calculating the length of the end portion 23Aa1 of the groove 23A1, the processing unit 62 accesses the storage unit 64 and reads out the mathematical formula (1) and the radius R of the cutting tool 54A A . Then, the processing unit 62 executes the application of the radius R A and the length of the end portion 23Aa1 of the groove 23A1 (L A ) in the mathematical formula (1) to calculate the lower end position (D A ) of the cutting tool 54.

[0091] The calculated lower end position of the cutting tool 54 is displayed on the display unit 58, for example. Thus, the operator can confirm the lower end position of the cutting tool 54. In addition, when the calculated lower end position of the cutting tool 54 is an abnormal value, the control unit 60 may cause the display unit 58 to display that it is in an abnormal state.

[0092] The above calculation step is realized, for example, by the processing unit 62 executing a program stored in the storage unit 64. Specifically, a program describing a series of processes (steps S2, S3, etc.) performed in the calculation step is pre-stored in the storage unit 64. Then, when a captured image is input from the imaging unit 48 to the control unit 60 (step S1), the processing unit 62 reads the program from the storage unit 64 and executes it to calculate the length of the end 23Aa1 of the groove 23A1.

[0093] The detection of the lower end position of the cutting tool 54A is performed multiple times using the same workpiece 21. Therefore, when the lower end position of the cutting tool 54A is detected for the second and subsequent times, the cutting tool 54A cuts into the workpiece 21 in which the groove 23A1 has been formed again to form the second groove 23A (groove forming step). Then, the above-mentioned calculation step is performed using the second groove 23A.

[0094] Figure 4 (B) is a top view showing the workpiece 21 formed with the second groove 23A (groove 23A2). The groove 23A2 includes an end portion (end side) 23Aa2 which is aligned with the side surface 54Aa (refer to Figure 2 and an end portion (end edge) 23Ab2, which is connected to the side surface 54Ab of the cutting tool 54A (reference Figure 2 ) corresponds. Figure 4 In (B), the first groove 23A1 already formed in the workpiece 21 is indicated by a line thinner than the groove 23A2.

[0095] in addition, Figure 4 The end 23Ab2 shown by the dotted line in (B) is a virtual end of the groove 23A2 corresponding to the position of the side surface 54Ab of the cutting tool 54A when the second groove 23A2 is formed. Figure 4 In (B), the end 23Aa1 of the first groove 23A1 removed by forming the second groove 23A2 is virtually indicated by a dotted line. In the following, in other figures, the virtual end of the groove is similarly indicated by a dotted line.

[0096] In the second groove forming step, the cutting tool 54A is caused to cut into the front surface 21a side of the workpiece 21 in such a manner that the side surface 54Aa of the cutting tool 54A does not overlap with the groove 23A (groove 23A1) already formed in the workpiece 21, and the side surface 54Ab of the cutting tool 54A overlaps with the groove 23A (groove 23A1) already formed in the workpiece 21. As a result, a groove 23A2 is formed in the workpiece 21, in which one end portion (end portion 23Aa2) in the width direction does not overlap with the groove 23A1 and the other end portion (end portion 23Ab2) in the width direction overlaps with the groove 23A1.

[0097] Next, a calculation step is performed to calculate the lower end position of the cutting tool 54A. Here, the lower end position of the cutting tool 54A is calculated based on the length of the end portion 23Aa2 of the groove 23A2. As shown in (B) of Figure 4 , the groove 23A2 is formed such that at least the end portion 23Aa2 does not overlap with the groove (groove 23A1) already formed in the workpiece 21, and thus the end portion 23Aa2 of the groove 23A2 is clearly imaged. Then, the control unit 60 calculates the lower end position of the cutting tool 54A based on the length of the end portion 23Aa2 (see Figure 5 ).

[0098] Then, in the case of further detecting the lower end position of the cutting tool 54A, the cutting tool 54A cuts into the workpiece 21 in which the grooves 23A1 and 23A2 have already been formed again to form a third groove 23A (groove forming step). Then, the above-described calculation step is performed using the third groove 23A.

[0099] Figure 4 (C) of Figure 2 shows a plan view of the workpiece 21 in which the third groove 23A (groove 23A3) is formed. The groove 23A3 includes an end portion (end edge) 23Aa3 that corresponds to the side surface 54Aa of the cutting tool 54A (see Figure 2 ); and an end portion (end edge) 23Ab3 that corresponds to the side surface 54Ab of the cutting tool 54A (see Figure 4 ). In (C) of

[0100] , the grooves 23A (grooves 23A1 and 23A2) already formed in the workpiece 21 are shown by lines thinner than the groove 23A3.In the third groove forming step, the cutting tool 54A is inserted into the front surface 21a side of the workpiece 21 in such a manner that the side surface 54Aa of the cutting tool 54A does not overlap with the grooves 23A (grooves 23A1 and 23A2) already formed in the workpiece 21, and the side surface 54Ab of the cutting tool 54A overlaps with the grooves 23A (grooves 23A1 and 23A2) already formed in the workpiece 21. As a result, a groove 23A3 is formed in the workpiece 21, in which one end portion (end portion 23Aa3) in the width direction does not overlap with the grooves 23A1 and 23A2, and the other end portion (end portion 23Ab3) in the width direction overlaps with the grooves 23A1 and 23A2.

[0101] Next, a calculation step is performed to calculate the lower end position of the cutting tool 54A. Here, the lower end position of the cutting tool 54A is calculated based on the length of the end portion 23Aa3 of the groove 23A3. As shown in (C) of Figure 4 , the groove 23A3 is formed such that at least the end portion 23Aa3 does not overlap with the grooves (grooves 23A1 and 23A2) already formed in the workpiece 21, so the end portion 23Aa3 of the groove 23A3 is clearly imaged. Then, the control unit 60 calculates the lower end position of the cutting tool 54A based on the length of the end portion 23Aa3 (see Figure 5 ).

[0102] As described above, in the present embodiment, the grooves 23A after the second one are formed in such a manner that a part thereof overlaps with the other grooves 23A already formed in the workpiece 21. Thereby, more grooves 23A can be formed in the workpiece 21, and thus the detection of the lower end position of the cutting tool 54A can be performed multiple times using a single workpiece 21. In addition, the detection of the lower end position of the cutting tool 54A after the fourth one is performed in the same order based on the length of the grooves 23A after the fourth one formed in the workpiece 21.

[0103] Figure 6 is a top view of the workpiece 21 after the detection of the lower end position of the cutting tool 54A has been performed multiple times. A plurality of grooves 23A are formed in the workpiece 21 in such a manner as to be connected to the other grooves 23A respectively. Therefore, compared with the case where there is a gap between two adjacent grooves 23A as in the past, more grooves 23A can be formed on a single workpiece 21. As a result, the usage amount of the workpiece 21 is reduced and the cost is lowered.

[0104] In addition, in the above description, the case of detecting the lower end position of the cutting tool 54A has been described. However, the detection of the lower end position of the cutting tool 54B can also be carried out in the same order. In this case, the cutting tool 54B is inserted into the front surface 21a side of the workpiece 21 in such a way that the side surface 54Ba of the cutting tool 54B does not overlap with the groove 23B already formed in the workpiece 21, and the side surface 54Bb of the cutting tool 54B overlaps with the groove 23B already formed in the workpiece 21. Then, the lower end position of the cutting tool 54B is calculated based on the length of the end portion 23Ba of the groove 23B.

[0105] As described above, in the method for detecting the position of the cutting tool according to the present embodiment, the cutting tools 54A and 54B are further inserted into the workpiece 21 in which the first groove (groove 23A or groove 23B) has already been formed, and the second groove (groove 23A or groove 23B) is formed on the workpiece 21 such that one end portion in the width direction does not overlap with the first groove and the other end portion in the width direction overlaps with the first groove. Thus, more grooves can be formed on a single workpiece 21, thereby reducing the usage amount of the workpiece 21.

[0106] In addition, in the present embodiment, the case where the lower end positions of the cutting tool 54A and the cutting tool 54B are detected separately has been described. However, the detection of the lower end positions of the cutting tool 54A and the cutting tool 54B can also be alternately carried out using the same workpiece 21, or carried out at the same timing. Hereinafter, an example of detecting the lower end positions of both the cutting tool 54A and the cutting tool 54B will be described.

[0107] First, the cutting tool 54A is inserted into the workpiece 21 to form the first groove (groove forming step). Figure 7 FIG. (A) is a top view of the workpiece 21 in which the first groove (groove 23A1) is formed. Then, the calculation step is carried out to detect the lower end position of the cutting tool 54A based on the length of the end portion 23Aa1 of the groove 23A1.

[0108] Next, the cutting tool 54B is inserted into the workpiece 21 to form the second groove (groove forming step). Figure 7 FIG. (B) is a top view of the workpiece 21 in which the second groove (groove 23B1) is formed. At this time, the groove 23B1 is formed such that one end portion (end portion 23Ba1) in the width direction does not overlap with the groove 23A1, and the other end portion (end portion 23Bb1) in the width direction overlaps with the groove 23A1. Then, the calculation step is carried out to detect the lower end position of the cutting tool 54B based on the end portion 23Ba1 of the groove 23B1.

[0109] Next, the cutting tool 54A is inserted into the workpiece 21 to form the third groove (groove forming step). Figure 7(C) is a top view showing the workpiece 21 in which the third groove (groove 23A2) is formed. At this time, the groove 23A2 is formed so as not to overlap with the other grooves (grooves 23A1, 23B1) already formed in the workpiece 21. Then, a calculation step is performed to detect the lower end position of the cutting tool 54A based on the end 23Aa2 of the groove 23A2.

[0110] Next, the cutting tool 54B is inserted into the workpiece 21 to form the fourth groove (groove forming step). Figure 7 (D) is a top view showing the workpiece 21 in which the fourth groove (groove 23B2) is formed. At this time, one end portion (end 23Ba2) in the width direction of the groove 23B2 is formed so as not to overlap with the other grooves (grooves 23A1, 23B1, 23A2) already formed in the workpiece 21, and the other end portion (end 23Bb2) in the width direction overlaps with the groove 23A2. Then, a calculation step is performed to detect the lower end position of the cutting tool 54B based on the end 23Ba2 of the groove 23B2.

[0111] In this way, when alternately detecting the lower end positions of the cutting tools 54A and 54B, the groove forming step is performed in such a manner that a part of the groove 23A formed by the cutting tool 54A overlaps with a part of the groove 23B formed by the cutting tool 54B. Thereby, the number of grooves that can be formed on one workpiece 21 is increased, and the usage amount of the workpiece 21 is reduced.

[0112] In addition, in the above, an example in which the detection of the lower end positions of the cutting tool 54A and the cutting tool 54B is performed independently is described, but the detection of the lower end positions of the cutting tool 54A and the cutting tool 54B can also be performed at the same timing. Specifically, it can also be that after the grooves 23A1 and 23B1 (grooves 23A2 and 23B2) are formed on the workpiece 21, the grooves 23A1 and 23B1 (grooves 23A2 and 23B2) are photographed simultaneously, thereby obtaining a single photographed image showing the grooves 23A1 and 23B1 (grooves 23A2 and 23B2).

[0113] In this case, the calculation step is performed using the photographed image showing the grooves 23A1 and 23B1 (grooves 23A2 and 23B2). Thereby, the lower end positions of the cutting tool 54A and the cutting tool 54B are calculated simultaneously.

[0114] In addition, the third groove (groove 23A2) and the fourth groove (groove 23B2) can also be formed in such a manner that a part of each overlaps with the first groove (groove 23A1) or the second groove (groove 23B1). Figure 8 (A) is a top view showing the workpiece 21 in which the third groove (groove 23A2) is formed in such a manner as to overlap with the first groove (groove 23A1) and the second groove (groove 23B1). In addition, Figure 8View (B) is a top view of workpiece 21 in which a fourth groove (groove 23B2) is formed so as to overlap with the first groove (groove 23A1) and the second groove (groove 23B1).

[0115] After detecting the lower end positions of the cutting tools 54A and 54B based on the grooves 23A1 and 23B1 formed in the workpiece 21 (see Figure 7 View (B)), the cutting tool 54A is inserted into the workpiece 21 to form a third groove (groove 23A2) (groove forming step). At this time, the groove 23A2 is formed such that one end portion (end portion 23Aa2) in the width direction does not overlap with the grooves (grooves 23A1 and 23B1) already formed in the workpiece 21, and the other end portion (end portion 23Ab2) in the width direction overlaps with the groove (groove 23A1 or groove 23B1) already formed in the workpiece 21 (see Figure 8 View (A)). Then, a calculation step is performed to detect the lower end position of the cutting tool 54A based on the length of the end portion 23Aa2 of the groove 23A2.

[0116] Next, the cutting tool 54B is inserted into the workpiece 21 to form a fourth groove (groove 23B2) (groove forming step). At this time, the groove 23B2 is formed such that one end portion (end portion 23Ba2) in the width direction does not overlap with the grooves (grooves 23A1, 23B1, and 23A2) already formed in the workpiece 21, and the other end portion (end portion 23Bb2) in the width direction overlaps with the groove (groove 23A1, groove 23B1, or groove 23A2) already formed in the workpiece 21 (see Figure 8 View (B)). Then, a calculation step is performed to detect the lower end position of the cutting tool 54B based on the end portion 23Ba2 of the groove 23B2.

[0117] As described above, by forming the grooves after the third groove so as to overlap with the other grooves already formed in the workpiece 21, the amount of the workpiece 21 used is further reduced. In addition, in the above case, it is also possible that after forming the grooves 23A2 and 23B2 in the workpiece 21 (see Figure 8 View (B)), the grooves 23A2 and 23B2 are photographed simultaneously to obtain a photographed image showing the grooves 23A2 and 23B2. In this case, the lower end positions of the cutting tool 54A and the cutting tool 54B are detected based on the same photographed image.

[0118] In addition, in the above-described embodiment, the case where the lower end positions of the cutting tools 54A and 54B are detected using the workpiece 21 held by the holding table 22 has been described. However, the workpiece 21 may be held by the holding table 18 and grooves may be formed in the workpiece 21. In addition, grooves may be formed in the outer peripheral portion (outer peripheral remaining area) of the workpiece 11 held by the holding table 18 where the device 13 is not formed, and the lower end positions of the cutting tools 54A and 54B may be detected.

[0119] In addition, the structures, methods, etc. of the above embodiments can be appropriately modified and implemented without departing from the scope of the object of the present invention.

Claims

1. A method for detecting the position of a cutting tool, which uses a cutting device to detect the lower end position of the cutting tool. The cutting device has a holding table and a cutting unit. The holding table holds a workpiece, and the cutting unit mounts the cutting tool for cutting the workpiece held by the holding table in a rotatable state. It is characterized in that, The method for detecting the position of the cutting tool has the following steps: A groove forming step of further cutting the cutting tool into the workpiece having a first groove to form a second groove on the workpiece. The first groove is formed by cutting the cutting tool into the workpiece. One end portion in the width direction of the second groove does not overlap with the first groove, and the other end portion in the width direction overlaps with the first groove; and A calculation step of calculating the lower end position of the cutting tool based on the length of one end portion in the width direction of the second groove formed in the workpiece.

Images