Processing method of workpiece

Abstract

A method for processing a workpiece is provided, which can prevent processing defects. A method for processing a workpiece using a cutting tool to cut the workpiece comprises the following steps: an outer diameter calculation step, calculating the outer diameter of the cutting tool that is worn by cutting the workpiece while the cutting tool rotates at a predetermined circumferential speed; a rotation speed calculation step, calculating the rotation speed of the worn cutting tool so that the difference between the predetermined circumferential speed and the circumferential speed of the worn cutting tool is less than a predetermined value based on the outer diameter of the cutting tool calculated in the outer diameter calculation step; and a cutting step, causing the worn cutting tool to rotate at a rotation speed corresponding to the rotation speed calculated in the rotation speed calculation step to cut into the workpiece and cut the workpiece.

Description

Technical Field

[0001] The present invention relates to a method for machining a workpiece, in which the workpiece is cut using a cutting tool. Background Art

[0002] A plurality of device chips each having a device are manufactured by dividing a semiconductor wafer having a plurality of devices such as IC (Integrated Circuit) and LSI (Large Scale Integration). In addition, a plurality of packaged devices each having a device chip covered with a molding resin are manufactured by dividing a package substrate formed by covering a plurality of device chips mounted on a substrate with a sealing material (molding resin) composed of a resin.

[0003] In the division of the workpiece represented by the above-mentioned semiconductor wafer and package substrate, for example, a cutting device is used. The cutting device has a chuck table for holding the workpiece and a spindle (rotating axis) for mounting a circular ring-shaped cutting tool for cutting the workpiece. When the spindle is rotated in a state where the cutting tool is mounted on the front end of the spindle, the cutting tool rotates. Then, the workpiece is cut by causing the rotating cutting tool to cut into the workpiece held by the chuck table (for example, refer to Patent Document 1).

[0004] As a cutting tool used for cutting a workpiece, for example, an electrocast hub tool is used, which has an annular cutting edge formed by fixing abrasive grains composed of diamond or the like with a plating layer composed of nickel or the like. When the workpiece is continuously cut using the cutting tool, the plating layer is worn and the exposed abrasive grains fall off, and new abrasive grains are exposed from the plating layer. This effect is called self-sharpening, and the cutting function of the cutting tool is maintained by self-sharpening.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2010-129623

[0006] When the workpiece is cut by the cutting tool, the rotation speed of the spindle on which the cutting tool is mounted is kept constant. On the other hand, when the cutting tool is inserted into the workpiece for cutting, the outer peripheral portion (front end portion) of the cutting tool is worn and the outer diameter of the cutting tool becomes smaller. Therefore, if the workpiece is cut continuously by the cutting tool, the speed of the outer peripheral edge (circumferential speed) of the cutting tool gradually decreases.

[0007] When the peripheral speed of the cutting tool is reduced, the load (machining load) applied to the workpiece when the cutting tool cuts into the workpiece increases. As a result, processing defects such as chipping (defects) or cracks may occur on the workpiece, thereby reducing the quality of the workpiece. Summary of the invention

[0008] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for processing a workpiece that can prevent the occurrence of processing defects.

[0009] According to one embodiment of the present invention, a method for processing a workpiece is provided, wherein the workpiece is cut by a cutting tool, wherein the method for processing the workpiece has the following steps: an outer diameter calculation step, calculating the outer diameter of the cutting tool that is worn by cutting the workpiece while the cutting tool rotates at a specified circumferential speed; a rotational speed calculation step, calculating the rotational speed of the worn cutting tool so that the difference between the specified circumferential speed and the circumferential speed of the worn cutting tool is less than a specified value based on the outer diameter of the cutting tool calculated in the outer diameter calculation step; and a cutting step, causing the worn cutting tool to rotate at a rotational speed corresponding to the rotational speed calculated in the rotational speed calculation step so as to cut into the workpiece and cut the workpiece.

[0010] Furthermore, in the above-mentioned method for machining a workpiece, it is preferable that the outer diameter calculation step, the rotation speed calculation step, and the cutting step are performed a plurality of times to machine the workpiece.

[0011] In a method for processing a workpiece according to one embodiment of the present invention, the rotation speed of the worn cutting tool is controlled according to the outer diameter of the worn cutting tool so that the difference in the peripheral speed of the cutting tool before and after the wear is less than a predetermined value. Thus, the increase in the processing load caused by the reduction in the peripheral speed of the cutting tool is suppressed, and the occurrence of processing defects of the workpiece is prevented. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a perspective view showing a cutting device.

[0013] Figure 2 (A) is a side view showing the cutting tool before wear, Figure 2 (B) is a side view showing the cutting tool after wear.

[0014] Figure 3 is a schematic diagram showing a rotation control system.

[0015] Figure 4 (A) is a schematic diagram showing the peripheral speed of the cutting tool when the rotation speed of the cutting tool is constant. Figure 4 (B) is a schematic diagram showing the peripheral speed of the cutting tool when the rotation speed of the cutting tool is changed.

[0016] Description of symbols

[0017] 11: workpiece; 13: belt (slicing belt); 15: frame; 2: cutting device; 4: base; 6: X-axis moving mechanism; 8: X-axis guide rail; 10: X-axis moving table; 12: X-axis ball screw; 14: X-axis pulse motor; 16: table base; 18: chuck table (holding table); 18a: holding surface; 20: fixture; 22: water tank; 24: support structure; 26: moving unit (moving mechanism); 28: Y-axis guide rail; 30: Y-axis moving plate; 32: Y-axis ball screw; 34: Y-axis pulse motor; 36: Z-axis guide rail; 38: Z-axis moving plate; 40: Z Axis ball screw; 42: Z-axis pulse motor; 44: cutting unit; 46: shooting unit (camera); 48: housing; 50: spindle; 52: cutting tool; 52a: cutting tool before wear; 52b: cutting tool after wear; 54: nozzle; 56: control unit (control unit); 60: rotation control system; 62: sensor unit; 64: detector; 64a: support unit; 64b: light projecting unit; 64c: light receiving unit; 66: light source; 68: photoelectric conversion unit; 70: position detection unit; 72: outer diameter calculation unit; 74: rotation speed calculation unit; 76: storage unit; 78: rotation control unit. DETAILED DESCRIPTION

[0018] Hereinafter, an embodiment of one mode of the present invention will be described with reference to the drawings. First, a configuration example of a cutting device that can be used for a method for processing a workpiece according to the present embodiment will be described. Figure 1 It is a perspective view showing the cutting device 2 .

[0019] The cutting device 2 has a base 4 on which various components constituting the cutting device 2 are mounted, and an X-axis moving mechanism 6 is provided on the upper surface of the base 4. The X-axis moving mechanism 6 has a pair of X-axis guide rails 8 arranged along the X-axis direction (processing feed direction, front-back direction), and an X-axis moving table 10 is mounted on the X-axis guide rails 8 in a manner that allows sliding along the X-axis guide rails 8 in the X-axis direction.

[0020] A nut portion (not shown) is provided on the lower surface (back side) of the X-axis movable table 10, and the nut portion is screwed with the X-axis ball screw 12 arranged along the X-axis guide rail 8. 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 movable table 10 moves in the X-axis direction along the X-axis guide rail 8. In addition, an X-axis measuring unit (not shown) for measuring the position of the X-axis movable table 10 in the X-axis direction can also be provided in the X-axis moving mechanism 6.

[0021] A cylindrical table base 16 is provided on the upper surface (front) side of the X-axis movable table 10. In addition, a chuck table (holding table) 18 for holding the workpiece 11 is provided on the upper portion of the table base 16. Also, four clamps 20 for holding and fixing the annular frame 15 supporting the workpiece 11 from all sides are provided around the chuck table 18.

[0022] The workpiece 11 is, for example, a disc-shaped semiconductor wafer made of a semiconductor such as silicon. The workpiece 11 is divided into a plurality of regions by predetermined dividing lines (spacers) arranged in a grid pattern in a mutually intersecting manner, and devices such as IC (Integrated Circuit) and LSI (Large Scale Integration) are formed on the upper surface (front) side of each region. However, there is no limitation on the type, number, shape, structure, size, and arrangement of the devices.

[0023] A circular tape (dicing tape) 13 having a diameter larger than that of the workpiece 11 is attached to the lower surface (back surface) of the workpiece 11. For example, the tape 13 is a soft film obtained by forming a rubber or acrylic adhesive layer (paste layer) on a base material composed of a resin such as polyolefin, polyvinyl chloride, or polyethylene terephthalate.

[0024] The outer periphery of the belt 13 is fixed to an annular frame 15 having an opening in the center with a diameter larger than that of the workpiece 11. Therefore, the workpiece 11 is supported by the frame 15 via the belt 13 while being arranged inside the opening of the frame 15.

[0025] In addition, the material, shape, structure, size, etc. of the workpiece 11 are not limited. For example, the workpiece 11 may be a wafer of any shape made of a semiconductor other than silicon (GaAs, InP, GaN, SiC, etc.), glass, ceramic, resin, metal, etc. In addition, the workpiece 11 may be a package substrate formed by covering a plurality of device chips mounted on a rectangular substrate with a package material (molding resin) made of resin.

[0026] The upper surface of the chuck table 18 constitutes a holding surface 18a for holding the workpiece 11. The holding surface 18a is formed to be 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 (not shown) such as an ejector via a flow path (not shown) formed inside the chuck table 18 and the table base 16.

[0027] The chuck table 18 is connected to a rotation drive source (not shown) such as a motor, and rotates around a rotation axis that is substantially parallel to the Z-axis direction (vertical direction, up and down direction). In addition, the X-axis moving table 10 is moved in the X-axis direction by the X-axis moving mechanism 6, thereby performing processing feeding of the chuck table 18.

[0028] A conveying mechanism (not shown) for conveying the workpiece 11 onto the chuck table 18 is provided near the chuck table 18. In addition, a water tank 22 for temporarily storing waste liquid such as cutting fluid (pure water, etc.) used for cutting is provided near the X-axis moving table 10. The waste liquid stored in the water tank 22 is discharged to the outside of the cutting device 2 via a drain pipe (not shown) or the like.

[0029] In addition, a gate-shaped support structure 24 is arranged on the upper surface of the base 4 so as to straddle the X-axis moving mechanism 6. Two sets of moving units (moving mechanisms) 26 are provided on the upper portion of the front surface of the support structure 24. The moving units 26 are slidably mounted on a pair of Y-axis guide rails 28 arranged on the front surface of the support structure 24 along the Y-axis direction. The Y-axis moving plate 30 constituting the moving unit 26 is mounted on the Y-axis guide rail 28 so as to be slidable along the Y-axis guide rail 28 in the Y-axis direction.

[0030] Nuts (not shown) are provided on the rear surface (back surface) of the Y-axis moving plate 30, and the nuts are screwed with Y-axis ball screws 32 arranged along the Y-axis guide rails 28. In addition, Y-axis pulse motors 34 are connected to one end of the pair of Y-axis ball screws 32, respectively.

[0031] When the Y-axis ball screw 32 is rotated by the Y-axis pulse motor 34, the Y-axis moving plate 30 moves in the Y-axis direction along the Y-axis guide rail 28. In addition, the moving unit 26 may be provided with a Y-axis measuring unit (not shown) for measuring the position of the Y-axis moving plate 30 in the Y-axis direction.

[0032] A pair of Z-axis guide rails 36 are disposed along the Z-axis on the front surface (front side) of the Y-axis moving plate 30. The Z-axis moving plate 38 is attached to the Z-axis guide rails 36 so as to be slidable in the Z-axis direction.

[0033] A nut portion (not shown) is provided on the rear surface (back side) side of the Z-axis moving plate 38, and the nut portion is screwed with the Z-axis ball screw 40 arranged along the Z-axis guide rail 36. A Z-axis pulse motor 42 is connected to one end of the Z-axis ball screw 40. When the Z-axis ball screw 40 is rotated by the Z-axis pulse motor 42, the Z-axis moving plate 38 moves along the Z-axis guide rail 36 in the Z-axis direction.

[0034] A cutting unit 44 for cutting the workpiece 11 is fixed to the lower part of the Z-axis moving plate 38. In addition, a photographing unit (camera) 46 for photographing the workpiece 11 is provided adjacent to the cutting unit 44. Figure 1 2 shows an example in which the cutting device 2 includes two sets of cutting units 44 , but the number of cutting units 44 included in the cutting device 2 may be one set.

[0035] The cutting unit 44 and the imaging unit 46 are indexed by moving the Y-axis moving plate 30 in the Y-axis direction. In addition, when the Z-axis moving plate 38 is moved in the Z-axis direction, the cutting unit 44 and the imaging unit 46 are raised and lowered and move in a direction substantially perpendicular to the holding surface 18a of the chuck table 18.

[0036] The cutting unit 44 has a cylindrical housing 48 supported by the moving unit 26. A spindle 50 (see FIG. 1 ) arranged substantially parallel to the Y-axis direction is accommodated in the housing 48. Figure 3 ).

[0037] The front end portion of one end side of the spindle 50 is exposed to the outside of the housing 48, and an annular cutting tool 52 is mounted on the front end portion. As the cutting tool 52, an electrocast hub tool having an annular cutting blade formed by fixing abrasive grains made of diamond or the like with a plating layer made of nickel or the like or a washer-type tool having an annular cutting blade formed by fixing abrasive grains made of metal, ceramic, resin or the like is used.

[0038] The other end of the spindle 50 is connected to a rotational drive source (not shown) such as a motor. The cutting tool 52 attached to the front end of the spindle 50 is rotated by the power of the rotational drive source transmitted through the spindle 50.

[0039] A nozzle 54 is provided near the cutting tool 52 to supply a cutting fluid such as pure water to the workpiece 11 or the cutting tool 52. When the workpiece 11 is cut by the cutting tool 52, the cutting fluid is supplied from the nozzle 54. Thus, the workpiece 11 and the cutting tool 52 are cooled, and the chips (cutting chips) generated by cutting are washed away.

[0040] Furthermore, a detector 64 for detecting the position (height) of the front end (lower end) of the cutting tool 52 in the Z-axis direction is provided below the cutting tool 52. The structure and function of the detector 64 will be described in detail later.

[0041] The components such as the X-axis moving mechanism 6, the chuck table 18, the moving unit 26, the cutting unit 44 and the imaging unit 46 are connected to the control unit (control part) 56. The control unit 56 controls the operation of each component constituting the cutting device 2 according to the processing conditions of the workpiece 11 and the like.

[0042] The workpiece 11 is cut by the cutting device 2. When the workpiece 11 is cut, the workpiece 11 is first held by the chuck table 18. Specifically, the tape 13 attached to the back side of the workpiece 11 is brought into contact with the holding surface 18a of the chuck table 18, and the frame 15 supporting the workpiece 11 is fixed by the clamp 20. In this state, the negative pressure of the suction source is applied to the holding surface 18a, and the workpiece 11 is sucked and held by the chuck table 18 in a state where the front side is exposed upward.

[0043] Next, the chuck table 18 is rotated so that the length direction of the predetermined dividing line coincides with the processing feed direction of the cutting device 2. In addition, the horizontal position of the cutting unit 44 is adjusted so that the cutting tool 52 is arranged on the extension line of the predetermined dividing line. Next, the height of the cutting unit 44 is adjusted so that the lower end of the cutting tool 52 is arranged at a position lower than the back surface of the workpiece 11.

[0044] Then, the chuck table 18 is moved in the machining feed direction while the cutting tool 52 is rotated at a predetermined rotation speed. As a result, the cutting tool 52 and the chuck table 18 move relative to each other, and the cutting tool 52 cuts into the workpiece 11 along the predetermined dividing line. Thus, the workpiece 11 is divided along the predetermined dividing line.

[0045] However, there is no limitation on the content of processing the workpiece 11 by the cutting tool 52. For example, the workpiece 11 may be cut by positioning the cutting tool 52 so that the lower end of the cutting tool 52 is arranged below the front surface of the workpiece 11 and above the back surface of the workpiece 11. In this case, a groove shallower than the thickness of the workpiece 11 is formed in the workpiece 11.

[0046] If the workpiece 11 is cut continuously using the cutting tool 52 , the outer peripheral portion (the tip portion) of the cutting tool 52 is worn. Figure 2 (A) is a side view showing the cutting tool 52a before wear, Figure 2 (B) is a side view showing the cutting tool 52b after wear.

[0047] The cutting tool 52a before being worn corresponds to, for example, a cutting tool before cutting the workpiece 11 (an unused cutting tool). Figure 2In (A), the outer diameter of the cutting tool 52a before wear is represented by X. The rotation speed of the cutting tool 52 when machining the workpiece 11 is determined with reference to the value of the outer diameter X.

[0048] When the workpiece 11 is cut using the cutting tool 52, the rotating cutting tool 52 comes into contact with the workpiece 11, and the outer peripheral portion of the cutting tool 52 is worn, and the outer diameter of the cutting tool 52 is reduced. Figure 2 In (B), the outer diameter of the cutting tool 52b after wear is represented by x (x<X).

[0049] Here, if the workpiece 11 is continuously cut while the rotation speed of the cutting tool 52 is kept constant, the outer diameter of the cutting tool 52 gradually decreases, and as a result, the speed (peripheral speed) of the outer peripheral edge of the cutting tool 52 decreases. In addition, when the peripheral speed of the cutting tool 52 decreases, the load (machining load) applied to the workpiece 11 when the cutting tool 52 cuts into the workpiece 11 increases. As a result, processing defects such as chipping (defects) or cracks may occur on the workpiece 11, thereby reducing the quality of the workpiece 11.

[0050] Therefore, in the processing method of the workpiece of the present embodiment, the outer diameter x of the worn cutting tool 52b is detected, and the rotation speed of the worn cutting tool 52b is controlled according to the outer diameter x so that the difference in the peripheral speed of the cutting tool 52 before and after the wear is less than a predetermined value. Thus, the increase in the processing load caused by the decrease in the peripheral speed of the cutting tool 52 is suppressed, and the processing defects of the workpiece 11 are prevented.

[0051] The cutting device 2 is equipped with a rotation control system 60 that controls the rotation of the cutting tool 52 . Figure 3 2 is a schematic diagram showing a rotation control system 60. When the workpiece processing method of the present embodiment is used, the rotation speed of the cutting tool 52 is controlled by the rotation control system 60.

[0052] The rotation control system 60 has a sensor unit 62 for detecting the position of the front end (lower end) of the cutting tool 52. The sensor unit 62 has a detector 64 for detecting the position (height) of the front end (lower end) of the cutting tool 52 in the Z-axis direction. The detector 64 has a support portion 64a formed in a rectangular parallelepiped shape, and a light projecting portion 64b and a light receiving portion 64c protruding upward from the upper surface of the support portion 64a and facing each other in the Y-axis direction.

[0053] The light projecting unit 64b is connected to a light source 66 composed of an LED (Light Emitting Diode) or the like via an optical fiber or the like, and is configured to be able to irradiate light toward the light receiving unit 64c. The light irradiated from the light projecting unit 64b is received by the light receiving unit 64c. In addition, the light receiving unit 64c is connected to a photoelectric conversion unit 68 composed of a photoelectric conversion element or the like via an optical fiber or the like. The photoelectric conversion unit 68 generates an electrical signal (voltage) corresponding to the amount of light reaching the light receiving unit 64c from the light projecting unit 64b.

[0054] The detector 64 is arranged below the cutting unit 44. When the cutting unit 44 is arranged so that the cutting tool 52 overlaps with the area between the light projecting portion 64b and the light receiving portion 64c, the front end portion (lower end portion) of the cutting tool 52 is inserted between the light projecting portion 64b and the light receiving portion 64c when the cutting unit 44 is lowered by the moving unit 26.

[0055] When the cutting tool 52 is inserted between the light projecting part 64b and the light receiving part 64c while the light is being irradiated from the light projecting part 64b toward the light receiving part 64c, the light irradiated from the light projecting part 64b toward the light receiving part 64c is blocked according to the position (height) of the lower end of the cutting tool 52, and the amount of light reaching the light receiving part 64c is reduced. Therefore, the amount of light received by the light receiving part 64c corresponds to the position of the lower end of the cutting tool 52. Then, the amount of light received by the light receiving part 64c is converted into an electrical signal (voltage) by the photoelectric conversion part 68, and then output to the outer diameter calculation part 72 of the control unit 56.

[0056] The moving unit 26 for controlling the position of the cutting unit 44 is connected to the position detecting unit 70. The position detecting unit 70 is connected to the moving unit 26 for controlling the position of the cutting unit 44 based on the Z-axis moving plate 38 (see Figure 1 ) in the Z-axis direction to detect the position of the cutting tool 52 in the Z-axis direction (for example, the position (height) of the center of the cutting tool 52). Then, the information on the position of the cutting tool 52 detected by the position detection unit 70 is output to the outer diameter calculation unit 72 of the control unit 56.

[0057] The control unit 56 includes an outer diameter calculation unit 72 that calculates the outer diameter of the cutting tool 52 mounted on the spindle 50 . The outer diameter calculation unit 72 first determines the position of the lower end of the cutting tool 52 based on the value of the voltage generated by the photoelectric conversion unit 68 .

[0058] For example, the outer diameter calculation unit 72 is connected to a storage unit 76 composed of a memory. The storage unit 76 stores information indicating the relationship between the voltage generated by the photoelectric conversion unit 68 and the position of the lower end of the cutting tool 52 acquired in advance. Then, the outer diameter calculation unit 72 determines the position of the lower end of the cutting tool 52 mounted on the spindle 50 based on the voltage input from the photoelectric conversion unit 68 and the information stored in the storage unit 76.

[0059] In addition, the position detection unit 70 calculates the outer diameter of the cutting tool 52 based on the position of the lower end of the cutting tool 52 and the information on the position of the cutting tool 52 detected by the position detection unit 70. For example, when the position of the center of the cutting tool 52 is detected by the position detection unit 70, the outer diameter of the cutting tool 52 is calculated based on the difference between the position of the center of the cutting tool 52 and the position of the lower end of the cutting tool 52.

[0060] The value of the outer diameter of the cutting tool 52 calculated by the outer diameter calculation unit 72 is input to the rotation speed calculation unit 74. Then, the rotation speed calculation unit 74 calculates the rotation speed of the cutting tool 52 suitable for cutting the workpiece 11.

[0061] As described above, if the cutting tool 52 is continuously used to cut the workpiece 11, the outer periphery of the cutting tool 52 wears and the outer diameter of the cutting tool 52 decreases. Therefore, when the rotation speed of the cutting tool 52 is kept constant, the peripheral speed of the cutting tool 52 decreases due to wear.

[0062] Figure 4 (A) is a schematic diagram showing the circumferential speed of the cutting tool 52 when the rotation speed of the cutting tool 52 is constant. Figure 4 (A) shows the cutting tool 52a before wear and the cutting tool 52b after wear, respectively, rotating by an angle θ per unit time.

[0063] If the outer diameter of the cutting tool 52a before wear is X and the outer diameter of the cutting tool 52b after wear is x (x<X), then when the rotation speed of the cutting tool 52 before and after wear is the same, the peripheral speed v of the cutting tool 52b after wear is smaller than the peripheral speed V of the cutting tool 52a before wear. Therefore, if the wear of the cutting tool 52 increases, the load applied to the workpiece 11 during cutting of the workpiece 11 increases, and processing defects of the workpiece 11 are likely to occur.

[0064] Therefore, in this embodiment, the rotation speed of the cutting tool 52 is changed according to the wear amount, that is, the change in the outer diameter of the cutting tool 52. This can make the peripheral speed of the cutting tool 52 equal before and after wear, and reduce the processing load of the workpiece 11.

[0065] Figure 4 (B) is a schematic diagram showing the peripheral speed of the cutting tool 52 when the rotation speed of the cutting tool 52 is changed. Figure 4 (B) shows that the rotation speed of the worn cutting tool 52b increases and the worn cutting tool 52b rotates by an angle θ+α per unit time. When the front end of the cutting tool 52 is worn, the rotation speed of the worn cutting tool 52b is appropriately increased to make the circumferential speed v of the worn cutting tool 52b close to the circumferential speed V of the cutting tool 52a before wear.

[0066] therefore, Figure 3 The rotation speed calculation unit 74 shown calculates the rotation speed of the worn cutting tool 52b so that the difference between the circumferential speed V of the cutting tool 52a before wear and the circumferential speed v of the cutting tool 52b after wear is less than a predetermined value. For example, the rotation speed calculation unit 74 calculates the rotation speed of the worn cutting tool 52b so that the circumferential speed v is the same as the circumferential speed V.

[0067] Specifically, if the rotation speed of the cutting tool 52a before wear (the initial value of the rotation speed of the cutting tool 52) is Y and the rotation speed of the cutting tool 52b after wear is y, the peripheral speed V of the cutting tool 52a before wear is expressed by V=πXY and the peripheral speed v of the cutting tool 52b after wear is expressed by v=πxy. Therefore, the rotation speed of the cutting tool 52b after wear for making the peripheral speed v the same as the peripheral speed V is expressed by y satisfying πXY=πxy, that is, y=XY / x.

[0068] The rotation speed calculation unit 74 is connected to a storage unit 76, which stores parameters such as the outer diameter X and the rotation speed Y of the cutting tool 52a before wear. When the rotation speed calculation unit 74 calculates the rotation speed, the parameters required for the calculation are read from the storage unit 76 and input to the rotation speed calculation unit 74.

[0069] The rotation speed calculation unit 74 calculates the rotation speed y=XY / x of the worn cutting tool 52b based on the value of the outer diameter x input from the outer diameter calculation unit 72 and the values ​​of the outer diameter X and the rotation speed Y input from the storage unit 76. Then, the rotation speed y calculated by the rotation speed calculation unit 74 is input to the rotation control unit 78 that controls the rotation of the cutting tool 52.

[0070] In addition, in the above content, an example of calculating the rotational speed y in a manner that the circumferential speed V and the circumferential speed v are the same is described, but the rotational speed y is not limited to this. For example, the rotational speed y may be calculated in a manner that the circumferential speed V and the circumferential speed v are different within a range that does not cause processing defects on the workpiece 11. In this case, the allowable range of the difference between the circumferential speed V and the circumferential speed v is appropriately determined according to the materials of the workpiece 11 and the cutting tool 52 or the processing feed speed and other processing conditions.

[0071] The rotation control unit 78 controls the rotation drive source connected to the main shaft 50 so that the cutting tool 52 rotates at a rotation speed corresponding to the rotation speed y calculated by the rotation speed calculation unit 74. For example, the rotation control unit 78 sets the rotation speed of the main shaft 50 to y. As a result, the rotation speed of the worn cutting tool 52b is increased so that the difference between the circumferential speed of the cutting tool 52a before wear and the circumferential speed of the cutting tool 52b after wear converges within a predetermined range.

[0072] In addition, the rotation speed y calculated by the rotation speed calculation unit 74 may be different from the actual rotation speed of the cutting tool 52. For example, when the calculated rotation speed y is a decimal value and the rotation speed of the cutting tool 52 needs to be specified by an integer value, the rotation control unit 78 may set the rotation speed of the cutting tool 52 to a value obtained by rounding off the calculated rotation speed y. In addition, the rotation control unit 78 may set the rotation speed of the cutting tool 52 to a value different from the calculated rotation speed y within a range that does not cause processing defects on the workpiece 11, based on the specifications of the cutting device 2, etc.

[0073] Next, a specific example of a method for machining a workpiece 11 using the cutting device 2 having the above-described rotation control system 60 will be described.

[0074] First, the chuck table 18 (see Figure 1 ) sucks and holds the workpiece 11. Then, the workpiece 11 is cut by causing the cutting tool 52 rotating at a predetermined circumferential speed to cut into the workpiece 11. The rotation speed and circumferential speed of the cutting tool 52 at this time are respectively equivalent to the rotation speed Y and circumferential speed V of the cutting tool 52a before wear.

[0075] The specific content of the processing of the workpiece 11 is not limited. For example, the workpiece 11 may be cut by the cutting tool 52 or a groove may be formed on the front surface of the workpiece 11 by the cutting tool 52.

[0076] If the workpiece 11 is continuously processed by the cutting tool 52, the outer peripheral portion of the cutting tool 52 is worn and the outer diameter of the cutting tool 52 is reduced. Therefore, when the processing time and number of processing times of the workpiece 11 by the cutting tool 52 reach a predetermined value, the following outer diameter calculation step is performed: Calculate the outer diameter of the cutting tool 52b after wear (refer to Figure 2 As described above, the outer diameter x of the worn cutting tool 52b is calculated based on Figure 3 The position information obtained by the sensor unit 62 and the position detection unit 70 is calculated by the outer diameter calculation unit 72 of the control unit 56 .

[0077] Next, the following rotation speed calculation step is performed: the rotation speed y of the worn cutting tool 52b is calculated based on the outer diameter x of the worn cutting tool 52b calculated in the outer diameter calculation step. The rotation speed y of the worn cutting tool 52b is calculated in such a way that the difference between the circumferential speed V of the cutting tool 52a before wear and the circumferential speed v of the worn cutting tool 52b is less than a predetermined value (for example, V=v). The calculation of the rotation speed y of the worn cutting tool 52b is performed by the rotation speed calculation unit 74 of the control unit 56. In addition, a specific example of the calculation method of the rotation speed y is as described above.

[0078] Next, a cutting step is performed in which the worn cutting tool 52 b is rotated at a rotation speed corresponding to the rotation speed y calculated in the rotation speed calculation step to cut into the workpiece 11 , thereby cutting the workpiece 11 .

[0079] In the cutting step, first, the worn cutting tool 52b is rotated at a rotation speed corresponding to the rotation speed y calculated in the rotation speed calculation step (for example, the same rotation speed as the rotation speed y). The rotation speed of the worn cutting tool 52b is controlled by the rotation control unit 78 of the control unit 56. As a result, the difference between the circumferential speed V of the cutting tool 52a before wear and the circumferential speed v of the cutting tool 52b after wear is less than a predetermined value.

[0080] Next, the worn cutting tool 52 whose rotation speed is controlled by the rotation control unit 78 is caused to cut into the workpiece 11. Thus, the machining of the workpiece 11 is resumed. At this time, since the workpiece 11 is cut by the worn cutting tool 52b in a state of increased peripheral speed, the machining load of the workpiece 11 is suppressed to be small.

[0081] As described above, in the processing method of the workpiece of the present embodiment, the rotation speed of the worn cutting tool 52b is controlled according to the outer diameter of the worn cutting tool 52b so that the difference in the peripheral speed of the cutting tool 52 before and after the wear is less than a predetermined value. Thus, the increase in the processing load caused by the decrease in the peripheral speed of the cutting tool 52 is suppressed, and the occurrence of processing defects of the workpiece 11 is prevented.

[0082] In addition, in the above content, an example of the outer diameter calculation step, the rotation speed calculation step, and the cutting step each being performed once is described, but the outer diameter calculation step, the rotation speed calculation step, and the cutting step may be performed multiple times to process the workpiece. That is, the rotation speed of the cutting tool 52 may be adjusted multiple times during the processing of one workpiece 11. Thus, the reduction in the circumferential speed of the cutting tool 52 caused by wear is more effectively suppressed, and poor processing of the workpiece 11 is less likely to occur.

[0083] In addition, the structure, method, etc. of the above-mentioned embodiment can be implemented with appropriate changes without departing from the scope of the purpose of the present invention.

Claims

1. A method for processing a workpiece, wherein the workpiece is cut by a cutting tool, wherein: The processing method of the workpiece has the following steps: an outer diameter calculation step of calculating an outer diameter of the cutting tool which is caused to wear by cutting the workpiece while the cutting tool, which rotates at a predetermined peripheral speed, cuts into the workpiece; a rotation speed calculation step of calculating, based on the outer diameter of the cutting tool calculated in the outer diameter calculation step, the rotation speed of the cutting tool after wear so that the difference between the prescribed circumferential speed and the circumferential speed of the cutting tool after wear is less than a prescribed value; as well as a cutting step of rotating the worn cutting tool at a rotation speed corresponding to the rotation speed calculated in the rotation speed calculation step to cut into the workpiece to cut the workpiece, The outer diameter calculation step, the rotation speed calculation step, and the cutting step are performed multiple times to machine the workpiece.

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