Grinding machine and grinding method

Abstract

To provide a technology that enables execution of both rough grinding and finish grinding without exchanging a grinding wheel mounted on a grinding machine.SOLUTION: The grinding machine includes a first grinding wheel, a second grinding wheel with a lower elastic modulus than the first grinding wheel, a grinding wheel shaft to which both the first grinding wheel and the second grinding wheel are mounted, a grinding wheel shaft motor that rotates the grinding wheel shaft, and a controller that grinds a workpiece by controlling the rotational speed of the grinding wheel shaft. When the rotational speed is a first speed, a diameter of the second grinding wheel is smaller than a diameter of the first grinding wheel; when the rotational speed is a second speed faster than the first speed, the diameter of the second grinding wheel is larger than the diameter of the first grinding wheel. The controller grinds the workpiece by switching between the first speed and the second speed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a grinding machine and a grinding method. [Background technology]

[0002] Patent Document 1 discloses a numerically controlled grinding machine equipped with multiple grinding wheels. When forming multiple tapers on a workpiece, this grinding machine calculates the amount of correction for the grinding wheels according to the rotation angle of the wheel head, and corrects the grinding wheels by an amount equivalent to the amount of correction, thereby creating steps in the grinding wheels. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Publication number 6-27334 Summary of the Invention [Problem to be solved by the invention]

[0004] In grinding workpieces, rough grinding is generally performed followed by finish grinding. Conventionally, it has been necessary to change the grinding wheel attached to the grinding machine between rough grinding and finish grinding, which has been a time-consuming process. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to a first aspect of the present disclosure, there is provided a grinding machine including a first grinding wheel, a second grinding wheel having a lower elastic modulus than the first grinding wheel, a grinding wheel spindle to which the first grinding wheel and the second grinding wheel are attached, a grinding wheel spindle rotation motor for rotating the grinding wheel spindle, and a control unit for controlling the rotation speed of the grinding wheel spindle to grind a workpiece, wherein when the rotation speed is a first speed, the diameter of the second grinding wheel is smaller than that of the first grinding wheel, and when the rotation speed is a second speed faster than the first speed, the diameter of the second grinding wheel is larger than that of the first grinding wheel, and the control unit switches between the first speed and the second speed to grind the workpiece. According to this type of grinding machine, a workpiece can be ground using the first grinding wheel and the second grinding wheel with different elastic moduli without replacing the grinding wheels attached to the grinding machine, thereby reducing the time and effort required for the user to replace the grinding wheels attached to the grinding machine. (2) The grinding machine of the above embodiment may further include a dresser that performs grinding wheel dressing of the first grinding wheel and the second grinding wheel, and in the grinding wheel dressing, the control unit sets the rotational speed to a grinding wheel dressing speed that is faster than the first speed and slower than the second speed, and the control unit may use the dresser to dress at least one of the first grinding wheel and the second grinding wheel so that the diameter of the first grinding wheel and the diameter of the second grinding wheel are equal when the rotational speed is at the grinding wheel dressing speed. According to the grinding machine of this type, the diameter of the first grinding wheel and the diameter of the second grinding wheel can be made equal at a specific rotation speed. (3) In the grinding machine of the above aspect, the control unit may set the rotation speed during rough grinding of the workpiece to the first speed, and set the rotation speed during finish grinding of the workpiece to the second speed. According to this type of grinding machine, the workpiece can be ground for rough grinding and finish grinding without changing the grinding wheel attached to the grinding machine. (4) According to a second aspect of the present disclosure, there is provided a method for grinding a workpiece using a first grinding wheel and a second grinding wheel attached to a grinding wheel spindle, the method comprising: a first grinding step in which the first grinding wheel grinds the workpiece when the rotational speed of the grinding wheel spindle is the first speed; According to this grinding method, the workpiece can be ground using the first grinding wheel and the second grinding wheel having different elastic moduli without replacing the grinding wheel attached to the grinding wheel spindle, thereby reducing the user's effort to replace the grinding wheel attached to the grinding wheel spindle. (5) The grinding method of the above embodiment may further include a grinding wheel adjustment step of adjusting the diameter of at least one of the first grinding wheel and the second grinding wheel so that the diameter of the first grinding wheel and the diameter of the second grinding wheel are equal to each other, while the rotation speed is at a grinding wheel adjustment speed that is faster than the first speed and slower than the second speed. According to the grinding method of this embodiment, the diameter of the first grindstone and the diameter of the second grindstone at a specific rotation speed can be made equal. (6) In the grinding method of the above embodiment, after the grinding wheel adjustment process is performed, the grinding process including the first grinding process and the second grinding process may be repeatedly performed multiple times, and in the grinding process, the second grinding process may be performed after the first grinding process. According to this grinding method, it is possible to prevent the grindstone adjustment step from being performed every time the grinding step is performed, and after rough grinding of the workpiece with the first grindstone having a high elastic modulus, finish grinding of the workpiece with the second grindstone having a low elastic modulus can be performed. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is an explanatory diagram showing a schematic configuration of a grinding machine. [Figure 2]Process diagram of the grinding process for a workpiece. [Figure 3] FIG. 10 is a diagram illustrating the diameters of the first grinding wheel and the second grinding wheel after the grinding wheel dressing process has been performed. [Figure 4] FIG. 10 is a diagram showing the relationship between the rotation speed of the grinding wheel and the amount of expansion. [Figure 5] FIG. 4 is a diagram illustrating the diameters of the first grinding wheel and the second grinding wheel when the rotation speed of the grinding wheel spindle is a first speed. [Figure 6] FIG. 6 is a diagram illustrating the diameters of the first grinding wheel and the second grinding wheel when the rotation speed of the grinding wheel spindle is a second speed. [Figure 7] FIG. 10 is a process diagram of a grinding process for a workpiece in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. First embodiment: FIG. 1 is an explanatory diagram showing the schematic configuration of a grinding machine 100. FIG. 1 shows arrows representing three mutually orthogonal coordinate axes, the X, Y, and Z axes. The Z and X axes are coordinate axes parallel to the horizontal plane. The Y axis is a coordinate axis parallel to the vertical direction. The arrows representing the X, Y, and Z axes in FIG. 1 and the arrows representing the X, Y, and Z axes in other figures point in the same direction. When specifying the direction, positive and negative signs are used in combination to indicate the direction, with "+" indicating the positive direction, which is the direction indicated by the arrow, and "-" indicating the negative direction, which is the opposite direction to the direction indicated by the arrow.

[0009] The grinding machine 100 is configured as a cylindrical grinding machine that rotates a cylindrical workpiece W about an axis RX of the workpiece W and approaches the rotating grinding wheel 33 in a cutting direction that intersects with the axis RX, thereby grinding the outer circumferential surface of the workpiece W with the grinding wheel 33. More specifically, the grinding machine 100 grinds the outer circumferential surface of the workpiece W by bringing the grinding wheel 33 into contact with the workpiece W and moving the workpiece W and the grinding wheel 33 relative to each other. In this embodiment, the cutting direction is the -X direction. The axis RX is also along the Z axis. The workpiece W is made of, for example, metal or ceramic. The workpiece W may have any shape that has a cylindrical portion.

[0010] The grinding machine 100 includes a bed 10, a support unit 20, a wheel head 30, a table moving device 40, a wheel head moving device 50, a dresser 60, a control unit 70, and drive circuits 81, 82, and 83.

[0011] The bed 10 supports the support part 20, the wheel head 30, the table moving device 40, and the wheel head moving device 50. The bed 10 is made of, for example, cast iron. On the upper surface of the bed 10, a sliding surface is formed for the support part 20 to move along the Z-axis direction, and a sliding surface is formed for the wheel head 30 to move along the X-axis direction.

[0012] The support unit 20 includes a table 21, a spindle unit 22, and a tailstock 28. The support unit 20 supports the workpiece W so that the workpiece W can rotate about an axis RX.

[0013] The table 21 is disposed on the upper surface of the bed 10. On the upper surface of the table 21, a spindle unit 22 and a tailstock 28 are attached.

[0014] The spindle device 22 is disposed on the −Z direction side of the workpiece W. The spindle device 22 applies a rotational force to the workpiece W. The spindle device 22 includes a headstock 23, a spindle 24, a chuck 25, and a spindle rotation motor 26.

[0015] The headstock 23 is fixed on the table 21 and supports the spindle 24 rotatably about the axis RX. The chuck 25 is fixed to the tip of the spindle 24 and grips the end of the workpiece W on the -Z direction side. The spindle rotation motor 26 rotates under the control of the control unit 70 and drives the spindle 24 to rotate. The rotation of the spindle 24 causes the workpiece W to rotate about the axis RX. The rotation speed of the spindle 24 is controlled by controlling the rotation speed of the spindle rotation motor 26. The spindle rotation motor 26 has a spindle encoder 27. A rotation speed signal of the spindle encoder 27 is fed back to the drive circuit 81.

[0016] The tailstock 28 is disposed opposite the headstock 23 in the Z-axis direction with the workpiece W sandwiched therebetween. The tailstock 28 includes a center 29. The center 29 supports the end of the workpiece W on the +Z direction side so that the workpiece W can rotate around the axis RX.

[0017] The wheel head 30 is disposed on the upper surface of the bed 10. The wheel head 30 includes a first grindstone 31, a second grindstone 32, a grindstone spindle 34, and a grindstone spindle rotation motor 35.

[0018] The first grinding wheel 31 and the second grinding wheel 32 rotate about their respective axes to grind the outer peripheral surface of the workpiece W. The first grinding wheel 31 and the second grinding wheel 32 are attached to a grinding wheel shaft 34 so that their respective axes coincide. Hereinafter, when the first grinding wheel 31 and the second grinding wheel 32 are referred to interchangeably, they will simply be referred to as grinding wheels 33.

[0019] The grinding wheel 33 has a core and a grinding wheel layer. The core is disk-shaped and made of metal such as iron. The core is detachably connected to the grinding wheel spindle 34 by bolts or the like. The grinding wheel layer is disk-shaped and provided on the outer periphery of the core. The grinding wheel layer is formed by mixing abrasive grains and a binder and baking the mixture. The abrasive grains used are, for example, cubic boron nitride (CBN) or diamond. The grinding wheel layer comes into contact with the workpiece W, thereby grinding the outer periphery of the workpiece W.

[0020] The binder of the second grinding wheel 32 is made of a material with a lower elastic modulus than the binder of the first grinding wheel 31. The binder of the first grinding wheel 31 may be, for example, a metal such as Ti (titanium), Cr (chromium), Fe (iron), Co (cobalt), Ni (nickel), Cu (copper), Ag (silver), Sn (tin), or workpiece W (tungsten), or an alloy containing at least a portion of these metals. The binder of the second grinding wheel 32 may be, for example, a thermosetting resin such as phenol resin, epoxy resin, or polyimide resin. In other words, the elastic modulus of the second grinding wheel 32 is lower than that of the first grinding wheel 31. The second grinding wheel 32 is also called an elastic grinding wheel.

[0021] The grinding wheel spindle 34 supports the first grinding wheel 31 and the second grinding wheel 32 rotatably around their axes. The grinding wheel spindle 34 is rotatably supported on the grinding wheel head 30 via bearings (not shown). The first grinding wheel 31 and the second grinding wheel 32 are attached to the grinding wheel spindle 34 so that the axis of the first grinding wheel 31, the axis of the second grinding wheel 32, and the grinding wheel rotation axis BX, which is the axis of the grinding wheel spindle 34, are aligned. The direction of the grinding wheel rotation axis BX is parallel to the Z axis.

[0022] The grinding wheel spindle rotation motor 35 is built into the grinding wheel head 30 coaxially with the grinding wheel spindle 34. The grinding wheel spindle rotation motor 35 drives the grinding wheel spindle 34 to rotate around the grinding wheel rotation axis BX. The rotation speed of the grinding wheel spindle rotation motor 35 is controlled by the control unit 70. As the grinding wheel spindle 34 is driven to rotate, the first grinding wheel 31 and the second grinding wheel 32 are driven to rotate around the grinding wheel rotation axis BX.

[0023] The table moving device 40 is connected to the table 21 and moves the table 21 along the Z-axis direction. The table moving device 40 has a table moving motor 41. The table moving motor 41 generates a driving force for moving the table 21 under the control of the control unit 70, and controls the position of the table 21. The table moving motor 41 has a table encoder 42. A position signal of the table encoder 42 is fed back to the drive circuit 82.

[0024] The wheel head moving device 50 is connected to the wheel head 30 and moves the wheel head 30 along the X-axis direction. The wheel head moving device 50 has a wheel head moving motor 51. The wheel head moving motor 51 generates a driving force for moving the wheel head 30 under the control of the control unit 70, and controls the position of the wheel head 30. The wheel head moving motor 51 has a wheel head encoder 52. A position signal from the wheel head encoder 52 is fed back to the drive circuit 83.

[0025] The dresser 60 is a device for conditioning the first grinding wheel 31 and the second grinding wheel 32. Here, grinding wheel conditioning refers to truing. Note that grinding wheel conditioning may include not only truing but also dressing. The dresser 60 is, for example, a single-element dresser or a multi-element dresser equipped with a single diamond element for conditioning the outer peripheral surface of the grinding wheel 33. The dresser 60 is guided and supported on a guard rail provided on the support unit 20 so that the dresser 60 can move along the Z direction. The dresser 60 is positioned so that the portion of the dresser 60 that contributes to grinding wheel conditioning, such as the single diamond element, can come into contact with the outer peripheral surface of the grinding wheel 33 when moved along the guard rail in the Z direction. The dresser 60 is driven by a table movement motor 41 to move in the Z direction. When grinding wheel dressing is not being performed, the dresser 60 is placed in an area around the workpiece W other than the area where the grinding wheel 33 and the workpiece W face each other and grinding is performed, as shown in FIG.

[0026] The control unit 70 controls the operation of the grinding machine 100. The control unit 70 includes a CPU 71 and a memory unit 72. The memory unit 72 stores a program for operating the grinding machine 100. More specifically, the memory unit 72 stores a program for executing a processing process, for example, grinding the workpiece W. The CPU 71 executes the program stored in the memory unit 72, thereby causing the control unit 70 to realize various functions. The control unit 70 may include a display unit formed of a liquid crystal display or the like, and an input unit formed of a keyboard and buttons.

[0027] The control unit 70 controls the rotation speed of the grinding wheel spindle 34, i.e., the rotation speed of the grinding wheel 33, by controlling the rotation speed of the grinding wheel spindle rotation motor 35. The control unit 70 outputs drive commands to drive circuits 81, 82, and 83. The drive circuit 81 controls the operation of the spindle rotation motor 26 in response to a command from the control unit 70. The drive circuit 82 controls the operation of the table movement motor 41 in response to a command from the control unit 70. The drive circuit 83 controls the operation of the wheel head movement motor 51 in response to a command from the control unit 70.

[0028] 2 is a process diagram of the grinding process of the workpiece W. The process shown in FIG. 2 realizes the method of grinding the workpiece W using the first grinding wheel 31 and the second grinding wheel 32. First, in step S10, the control unit 70 sends a command to the grinding wheel spindle rotation motor 35 to rotate the grinding wheel spindle 34 around the grinding wheel rotation axis BX at a predetermined grinding wheel dressing speed. As a result, the first grinding wheel 31 and the second grinding wheel 32 rotate around the grinding wheel rotation axis BX at the grinding wheel dressing speed.

[0029] In step S20, first, the control unit 70 controls the wheel head movement motor 51 via the drive circuit 83 to move the wheel head 30 in the X-axis direction to a position where the portion of the dresser 60 contributing to wheel dressing can come into contact with the first grinding wheel 31 and the second grinding wheel 32 in the X-axis direction. Next, the control unit 70 moves the dresser 60 in the Z-axis direction so that the dresser 60 comes into contact with the first grinding wheel 31 and the second grinding wheel 32 without changing the relative positions of the dresser 60 and the wheel head 30 in the X-axis direction, thereby dressing the diameters of the first grinding wheel 31 and the second grinding wheel 32. At this time, the control unit 70 uses the dresser 60 to dress the diameters of the first grinding wheel 31 and the second grinding wheel 32 so that they are equal. Hereinafter, the diameter of the first grinding wheel 31 will also be referred to as the first diameter R1, and the diameter of the second grinding wheel 32 will also be referred to as the second diameter R2. The control unit 70 may adjust the diameter of either the first grinding wheel 31 or the second grinding wheel 32 so that the diameter of the first grinding wheel 31 is equal to the diameter of the second grinding wheel 32. Steps S10 and S20 are also referred to as a grinding wheel adjustment process.

[0030] 3 is a diagram illustrating the diameter of the first grinding wheel 31 and the diameter of the second grinding wheel 32 after the grinding wheel dressing process has been performed. As shown in FIG. 3, by performing the grinding wheel dressing process, the first diameter R1 and the second diameter R2 become equal when the rotation speed of the grinding wheel spindle 34 is the grinding wheel dressing speed.

[0031] 2, the control unit 70 sends a command to the grinding wheel spindle rotation motor 35 to rotate the grinding wheel spindle 34 around the grinding wheel rotation axis BX at a first speed. The first speed is slower than the grinding wheel dressing speed. As a result, the first grinding wheel 31 and the second grinding wheel 32 rotate around the grinding wheel rotation axis BX at the first speed.

[0032] FIG. 4 shows the relationship between the rotation speed and the amount of expansion of the grinding wheel 33. The horizontal axis of FIG. 4 represents the rotation speed of the grinding wheel 33 around the grinding wheel rotation axis BX. The vertical axis of FIG. 4 represents the increase in the diameter of the grinding wheel 33 from a stationary state. When the grinding wheel 33 rotates around the grinding wheel rotation axis BX, the diameter of the grinding wheel 33 increases due to centrifugal force. Hereinafter, the increase in the diameter of the grinding wheel 33 from a stationary state is referred to as the amount of expansion of the grinding wheel 33. In FIG. 4, the amount of expansion of the first grinding wheel 31 is shown by a solid line, and the amount of expansion of the second grinding wheel 32 is shown by a dashed line. Because the elastic modulus of the second grinding wheel 32 is smaller than that of the first grinding wheel 31, the increase in the amount of expansion of the grinding wheel 33 with respect to the increase in the rotation speed of the grinding wheel 33 is greater for the second grinding wheel 32 than for the first grinding wheel 31.

[0033] 5 is a diagram illustrating the diameters of the first grinding wheel 31 and the second grinding wheel 32 when the rotational speed of the grinding wheel spindle 34 is the first speed. Because the elastic modulus of the second grinding wheel 32 is smaller than that of the first grinding wheel 31, when the rotational speed of the grinding wheel spindle 34 is reduced from the grinding wheel dressing speed to the first speed, the second diameter R2 decreases more than the first diameter R1. As described above, in the grinding wheel dressing process, the diameter of the grinding wheel 33 is dressed so that the first diameter R1 and the second diameter R2 are equal when the rotational speed of the grinding wheel spindle 34 is the grinding wheel dressing speed. Therefore, when the rotational speed of the grinding wheel spindle 34 is the first speed, the second diameter R2 is smaller than the first diameter R1.

[0034] In step S40 of Fig. 2, the control unit 70 controls the wheel head moving motor 51 via the drive circuit 83 to move the wheel head 30 in the -X direction, bringing the first grinding wheel 31 into contact with the workpiece W, and grinding the workpiece W with the first grinding wheel 31. The first grinding wheel 31 grinds the workpiece W, thereby performing rough grinding of the workpiece W. Steps S30 and S40 are also referred to as a first grinding step. In this embodiment, steps S30 and S40 are also referred to as a rough grinding step.

[0035] In step S50, the control unit 70 controls the wheel head moving motor 51 via the drive circuit 83 to move the wheel head 30 in the +X direction, thereby separating the first grinding wheel 31 and the workpiece W.

[0036] In step S60, the control unit 70 sends a command to the grinding wheel spindle rotation motor 35 to rotate the grinding wheel spindle 34 around the grinding wheel rotation axis BX at a second speed. The second speed is faster than the grinding wheel dressing speed. This causes the first grinding wheel 31 and the second grinding wheel 32 to rotate around the grinding wheel rotation axis BX at the second speed.

[0037] 6 is a diagram illustrating the diameters of the first grinding wheel 31 and the second grinding wheel 32 when the rotation speed of the grinding wheel spindle 34 is the second speed. As described above, the elastic modulus of the second grinding wheel 32 is smaller than that of the first grinding wheel 31, and in the grinding wheel dressing process, the diameter of the grinding wheel 33 is dressed so that the first diameter R1 and the second diameter R2 are equal when the rotation speed of the grinding wheel spindle 34 is the grinding wheel dressing speed. Therefore, when the rotation speed of the grinding wheel spindle 34 is the second speed, which is faster than the grinding wheel dressing speed, the second diameter R2 is larger than the first diameter R1.

[0038] 2, the control unit 70 controls the wheel head moving motor 51 via the drive circuit 83 to move the wheel head 30 in the −X direction, bringing the second grinding wheel 32 into contact with the workpiece W, and grinding the workpiece W with the second grinding wheel 32. The second grinding wheel 32 grinds the workpiece W, thereby performing finish grinding of the workpiece W. Steps S60 and S70 are also referred to as a second grinding step. In this embodiment, steps S60 and S70 are also referred to as a finish grinding step.

[0039] In step S80, the control unit 70 controls the wheel head moving motor 51 via the drive circuit 83 to move the wheel head 30 in the +X direction, thereby separating the second grinding wheel 32 from the workpiece W. Steps S30 to S80 are also referred to as a grinding process.

[0040] In step S90, the control unit 70 determines whether grinding of the workpiece W is complete. If grinding of the workpiece W is complete, the control unit 70 terminates the grinding process of the workpiece W. If grinding of the workpiece W is not complete, the control unit 70 returns the process to step S30. This causes the grinding process to be repeated. Here, cases in which grinding of the workpiece W is not complete include, for example, when the surface roughness of the workpiece W has not reached its target value, or when the diameter of the workpiece W is larger than its target value. Whether grinding of the workpiece W is complete is determined based on, for example, the diameter of the workpiece W measured by a sizing device or the movement amount of the grinding wheel head moving device 50. In addition, when a plurality of workpieces W are ground in the grinding process of the workpieces W, the control unit 70 may determine in step S90 whether grinding of a predetermined number of workpieces W has been completed, and if grinding of the predetermined number of workpieces W has not been completed, the workpieces W may be replaced and the process may return to step S30. The grinding process of the workpieces W is performed as described above.

[0041] According to the first embodiment described above, the elastic modulus of the second grinding wheel 32 is smaller than that of the first grinding wheel 31. When the rotation speed of the grinding wheel spindle 34 is a first speed, the diameter of the second grinding wheel 32 is smaller than that of the first grinding wheel 31. When the rotation speed of the grinding wheel spindle 34 is a second speed faster than the first speed, the diameter of the second grinding wheel 32 is larger than that of the first grinding wheel 31. The control unit 70 grinds the workpiece W by switching between the first speed and the second speed. Specifically, the control unit 70 grinds the workpiece W using the first grinding wheel 31 when the rotation speed of the grinding wheel spindle 34 is the first speed, and grinds the workpiece W using the second grinding wheel 32 when the rotation speed of the grinding wheel spindle 34 is the second speed. Therefore, the workpiece W can be ground using two grinding wheels 33 with different elastic moduli without replacing the grinding wheel 33. This reduces the user's effort in replacing the grinding wheel 33 attached to the grinding machine 100.

[0042] Furthermore, in this embodiment, the control unit 70 adjusts at least one of the diameters of the first grinding wheel 31 and the second grinding wheel 32 using the dresser 60 so that the diameters of the first grinding wheel 31 and the second grinding wheel 32 are equal to each other when the rotation speed of the grinding wheel spindle 34 is at the grinding wheel adjustment speed. Therefore, the diameters of the first grinding wheel 31 and the second grinding wheel 32 at a specific rotation speed can be made equal to each other.

[0043] In this embodiment, the control unit 70 sets the rotational speed of the grinding wheel spindle 34 to a first speed during rough grinding of the workpiece W, and sets the rotational speed of the grinding wheel spindle 34 to a second speed during finish grinding of the workpiece W. Therefore, the workpiece W can be ground without changing the grinding wheel 33 between rough grinding and finish grinding of the workpiece W.

[0044] Furthermore, in this embodiment, after the grinding wheel dressing process is performed, the grinding process is repeatedly performed multiple times. Therefore, it is possible to prevent the grinding wheel dressing process from being performed every time the grinding process is performed. Furthermore, after the grinding wheel dressing is performed once, grinding of the workpiece W can be continued until grinding of the workpiece W is completed. Furthermore, when multiple workpieces W are ground in the grinding process of the workpiece W shown in FIG. 2, the multiple workpieces W can be ground after the grinding wheel dressing is performed once.

[0045] In the present embodiment, the second grinding step is performed after the first grinding step in the grinding process, so that after rough grinding of the workpiece W is performed with the first grinding wheel 31 having a high elastic modulus, finish grinding of the workpiece W can be performed with the second grinding wheel 32 having a low elastic modulus.

[0046] B. Second embodiment: The second embodiment differs from the first embodiment in the grinding process of the workpiece W. The configuration of each part of the grinding machine 100 in the second embodiment is the same as that in the first embodiment.

[0047] 7 is a process diagram of the grinding process of the workpiece W in the second embodiment. Note that the same reference numerals are used to denote parts in which the same processes as those in the grinding process of the workpiece W in the first embodiment are executed, and the description thereof will be omitted.

[0048] In step S110, the control unit 70 determines whether the first grinding wheel 31 or the second grinding wheel 32 requires grinding dressing. The control unit 70 determines that the first grinding wheel 31 or the second grinding wheel 32 requires grinding dressing, for example, when the sharpness of the first grinding wheel 31 or the second grinding wheel 32 has deteriorated or when a predetermined time has passed since the last grinding wheel dressing. If it is determined that grinding wheel dressing is required, steps S10 and S20 are executed. If it is determined that grinding wheel dressing is not required, step S30 is executed. Whether the sharpness of the grinding wheel 33 has deteriorated is determined based on a change in the diameter of the workpiece W measured by a sizing device or the like. For example, if the amount of workpiece W machined by the grinding wheel 33 remains the same but the time required for machining increases, it is determined that the sharpness of the grinding wheel 33 has deteriorated. Alternatively, whether the sharpness of the grinding wheel 33 has deteriorated may be determined based on the relationship between the movement amount of the grinding wheel head moving device 50 and the current of the grinding wheel spindle rotation motor 35. For example, if the current of the grinding wheel spindle rotation motor 35 increases even when the movement amount of the grinding wheel head moving device 50 is the same, it is determined that the sharpness of the grinding wheel 33 has deteriorated. Note that it may also be determined that the sharpness of the grinding wheel 33 has deteriorated if the drive power of each part of the grinding machine 100 increases. Whether a predetermined time has elapsed since the last grinding wheel dressing was performed is determined based on the processing time of the workpiece W, etc. Whether a predetermined time has elapsed since the last grinding wheel dressing was performed may also be determined taking into account the processing amount and material of the workpiece W, etc.

[0049] If grinding of the workpiece W is not completed in step S90, the control unit 70 returns the process to step S110.

[0050] According to the second embodiment described above, similarly to the first embodiment, the workpiece W can be ground using two grinding wheels 33 with different elastic moduli without replacing the grinding wheel 33. Furthermore, grinding wheel dressing of the first grinding wheel 31 or the second grinding wheel 32 can be performed only when grinding wheel dressing of the first grinding wheel 31 or the second grinding wheel 32 is necessary.

[0051] C. Other Embodiments: (C-1) In the above embodiment, the grinding machine 100 is equipped with the dresser 60. In contrast, the grinding machine 100 does not have to be equipped with the dresser 60. In this case, the grinding wheel adjustment process does not have to be performed in the grinding process of the workpiece W. Specifically, steps S10 and S20 in the grinding process of the workpiece W do not have to be performed.

[0052] (C-2) In the above embodiment, in the grinding process of the workpiece W, the grinding process is repeatedly executed after the grindstone adjustment process is executed. In contrast, in the grinding process of the workpiece W, the grinding process does not have to be repeatedly executed. Specifically, step S90 in the grinding process of the workpiece W does not have to be executed.

[0053] (C-3) In the above embodiment, the first grinding step is performed before the second grinding step is performed in the grinding process of the workpiece W. Alternatively, the second grinding step may be performed before the first grinding step.

[0054] (C-4) In the above embodiment, the grinding step is performed after the grinding wheel dressing step is performed in the grinding process of the workpiece W. However, the grinding wheel dressing step may be performed after the grinding step is performed.

[0055] (C-5) In the above embodiment, the grinding machine 100 is provided with two grinding wheels 33 with different elastic moduli. However, the grinding machine 100 may be provided with three or more grinding wheels 33 with different elastic moduli.

[0056] (C-6) In the above embodiment, the grinding machine 100 is a cylindrical grinding machine. However, the grinding machine 100 may be an internal grinding machine, a centerless grinding machine, or a surface grinding machine.

[0057] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0058] 10...bed, 20...support part, 21...table, 22...spindle device, 23...headstock, 24...spindle, 25...chuck, 26...spindle rotation motor, 27...spindle encoder, 28...tailstock, 29...center, 30...grinding wheel head, 31...first grinding wheel, 32...second grinding wheel, 33...grinding wheel, 34...grinding wheel spindle, 35...grinding wheel spindle rotation motor, 40...table moving device, 41...table moving motor, 42...table encoder, 50...grinding wheel head moving device, 51...grinding wheel head moving motor, 52...grinding wheel head encoder, 60...dresser, 70...control part, 71...CPU, 72...storage part, 81...drive circuit, 82...drive circuit, 83...drive circuit, 100...grinding machine, BX...grinding wheel rotation axis, R1...first diameter, R2...second diameter, RX...axis, W...workpiece

Claims

1. A grinding machine comprising: A first grinding wheel; a second grinding stone having a lower elastic modulus than the first grinding stone; a grinding wheel spindle to which the first grinding wheel and the second grinding wheel are attached; a grinding wheel spindle rotating motor that rotates the grinding wheel spindle; a control unit that controls the rotation speed of the grinding wheel spindle to grind the workpiece, When the rotation speed is a first speed, the diameter of the second grinding wheel is smaller than the diameter of the first grinding wheel; When the rotation speed is a second speed that is faster than the first speed, the diameter of the second grindstone is larger than the diameter of the first grindstone, The control unit switches between the first speed and the second speed to grind the workpiece. Grinding machine.

2. 2. The grinding machine according to claim 1, a dresser for dressing the first grindstone and the second grindstone; In the grinding wheel correction, the control unit sets the rotation speed to a grindstone dressing speed that is faster than the first speed and slower than the second speed, the control unit adjusts a diameter of at least one of the first grinding wheel and the second grinding wheel using the dresser so that the diameter of the first grinding wheel and the diameter of the second grinding wheel become equal when the rotation speed is the grinding wheel adjusting speed. Grinding machine.

3. 2. The grinding machine according to claim 1, the control unit sets the rotation speed during rough grinding of the workpiece to the first speed, and sets the rotation speed during finish grinding of the workpiece to the second speed. Grinding machine.

4. A method for grinding a workpiece using a first grinding wheel and a second grinding wheel attached to a grinding wheel spindle, comprising: the elastic modulus of the second grinding stone is smaller than the elastic modulus of the first grinding stone, When the rotation speed of the grinding wheel spindle is a first speed, the diameter of the second grinding wheel is smaller than the diameter of the first grinding wheel; When the rotation speed is a second speed that is faster than the first speed, the diameter of the second grindstone is larger than the diameter of the first grindstone, The grinding method comprises: a first grinding step in which the first grinding wheel grinds the workpiece while the rotation speed is the first speed; a second grinding step in which the second grinding wheel grinds the workpiece while the rotation speed is the second speed. Grinding method.

5. 5. The grinding method according to claim 4, The method further includes a grindstone dressing step of dressing at least one of the first grindstone and the second grindstone so that the diameter of the first grindstone and the diameter of the second grindstone are equal to each other, while the rotation speed is at a grindstone dressing speed that is faster than the first speed and slower than the second speed. Grinding method.

6. 6. The grinding method according to claim 5, After the grindstone dressing step is performed, a grinding step including the first grinding step and the second grinding step is repeatedly performed a plurality of times; In the grinding step, the second grinding step is carried out after the first grinding step. Grinding method.

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