JP2004268232A - Grinding attachment and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately grind a workpiece by improving grinding efficiency by shortening time required for dressing and reducing a frequency for dressing grinding wheels, in a grinding attachment and its control method when extra-precisely grinding the work such as glass of an optical part and a semiconductor silicon wafer. <P>SOLUTION: A double-ended grinding attachment 20 is provided with grinding main spindle rotating means 35a and 35b, normal component force detecting means 36a and 36b, and a control means 37. The control means 37 determines whether the cutting quality of the grinding wheels 32a and 32b is reduced on the basis of a variation in normal component force detected by the normal component force detecting means 36a and 36b. The grinding main spindle rotating means 35a and 35b grind the work 33 by switching the rotational direction of the cutting quality-reduced grinding wheels 32a and 32b in the opposite direction. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a grinding apparatus and a control method therefor, and more particularly to a grinding apparatus and a control method therefor when a workpiece such as glass of an optical component or a semiconductor silicon wafer is ultra-precisely ground.
[0002]
[Prior art]
2. Description of the Related Art In a conventional grinding apparatus, a grinding process is generally performed by bringing a rotated grindstone into contact with a work. When the grindstone used for this grinding is ground for a predetermined time, clogging, blinding, falling off of abrasive grains, etc. may occur, and the sharpness of the grindstone may be reduced. If the work is ground in a state where the sharpness of the grindstone is reduced, there is a problem that the processing accuracy of the work is reduced.
[0003]
A double-headed grinding device, which is one of the grinding devices, has two opposed grinding wheels, and when performing grinding of a workpiece in a state where the sharpness of one of the grinding wheels is reduced, two grinding wheels are used. There is a problem in that the roughness of the two ground surfaces of the workpiece after the grinding process is different due to the difference in sharpness, and the workpiece is warped.
[0004]
Therefore, conventionally, when the sharpness of a grindstone has been reduced, the sharpness of the grindstone has been recovered by dressing the grindstone using a dressing board or a dressing grindstone (for example, see Patent Document 1).
[0005]
[Patent Document 1]
JP-A-2000-6019
[0006]
[Problems to be solved by the invention]
However, since the sharpness of a grindstone decreases when the work is ground for a predetermined time, it is necessary to dress the grindstone every time the work is ground for a predetermined time, and dressing the grindstone reduces the grinding efficiency of the grinding device. Note that the frequency of dressing depends on the grinding wheel, grinding conditions, and the like.
[0007]
Therefore, the present invention has been made in view of the above circumstances, and reduces the frequency of dressing a grindstone, shortens the time required for dressing, improves the grinding efficiency, and provides a grinding method capable of grinding a workpiece with high accuracy. It is an object to provide an apparatus and a control method thereof.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is characterized by taking the following means.
[0009]
According to the first aspect of the present invention, there is provided a grinding device capable of switching a rotation direction of a grindstone between two directions, a rotation driving unit for rotating the grindstone to grind a workpiece, and detecting a decrease in sharpness of the grindstone. The problem can be solved by a grinding apparatus comprising: a detecting unit; and a control unit that switches a rotating direction of the grinding wheel to an opposite direction when a decrease in sharpness of the grinding wheel is detected by the detecting unit.
[0010]
According to the above invention, when the detecting means detects a decrease in the sharpness of the grindstone, the control means switches the rotation direction of the grindstone to the opposite direction, recovers the sharpness of the grindstone, and accurately grinds the workpiece. Can be. Further, the grinding efficiency can be improved as compared with the case where dressing of the grindstone is performed.
[0011]
In the invention according to claim 2, the control unit terminates the grinding of the workpiece during the grinding when the detection unit detects a decrease in the sharpness of the grindstone during the grinding of the workpiece. The problem can be solved by the grinding device according to claim 1, wherein the direction of rotation of the grindstone is switched to an opposite direction later.
[0012]
According to the above invention, when the detection means detects a decrease in the sharpness of the grindstone, the control means switches the rotation direction of the grindstone to the opposite direction after the grinding of the work being ground is completed. It is possible to prevent the accuracy from decreasing.
[0013]
In the invention according to claim 3, the detecting means detects a change in grinding resistance generated when the sharpness of the grinding wheel is reduced during the grinding of the work, and the control means detects a change in the grinding resistance. The method according to claim 1 or 2, wherein the rotation direction of the whetstone is switched to the opposite direction based on the above.
[0014]
According to the invention, the control means can detect that the sharpness of the grindstone has decreased by the detection means detecting the fluctuation of the grinding resistance. Therefore, the control means can switch the rotation direction of the grinding wheel to the opposite direction based on the fluctuation of the grinding resistance.
[0015]
In the invention according to claim 4, a fluctuation value of the grinding resistance when the sharpness of the grinding wheel is reduced is set as a threshold value, and the control unit reverses the rotation direction of the grinding wheel based on the threshold value. The direction can be changed by the grinding device according to any one of claims 1 to 3.
[0016]
According to the above invention, by setting the fluctuation value of the grinding resistance when the sharpness of the grindstone is reduced as the threshold value, when the fluctuation of the grinding resistance exceeds the threshold value, the control means controls the sharpness of the grindstone. , The direction of rotation of the grindstone can be switched to the opposite direction.
[0017]
In the invention as set forth in claim 5, the grindstone is composed of two opposed grindstones, and the control means controls the rotation directions of the two grindstones independently, and the control means controls the grinding resistance. 5. When the variation value of the grinding wheel is detected to exceed the threshold value, the rotation direction of the grinding wheel on the side where the variation value of the grinding resistance exceeds the threshold value is switched to the opposite direction. The problem can be solved by the grinding device described in (1).
[0018]
According to the above invention, the control means independently controls the rotation directions of the two grindstones. Therefore, when it is detected that the fluctuation value of the grinding resistance exceeds the threshold, the grindstone on the side where the sharpness of the grindstone has decreased is detected. By switching the rotation direction to the opposite direction, the processing accuracy of the work can be improved.
[0019]
In the invention according to claim 6, the control means switches the rotation directions of the two grindstones to opposite directions when it is detected that the fluctuation value of the grinding resistance exceeds the threshold value. The problem can be solved by the grinding device according to the fifth aspect.
[0020]
According to the invention, the control means switches the rotation directions of the two grindstones to opposite directions when it is detected that the fluctuation value of the grinding resistance exceeds the threshold value, so that the sharpness of the two grindstones is made equal. Can be. Therefore, the processing accuracy of the work can be further improved.
[0021]
In the invention according to claim 7, there is provided a grinding device in which the rotation direction of the grindstone can be switched between two directions, and a rotation driving means for rotating the grindstone to grind the workpiece, and the sharpness of the grindstone is reduced in advance. Storage means for storing the operation amount of the grindstone, detection means for detecting the operation amount of the whetstone, and the actual operation amount of the whetstone detected by the detection means, the operation amount of the whetstone stored in the storage means, A control device for switching the direction of rotation of the grinding wheel to the opposite direction when it exceeds the distance can be solved by a grinding device.
[0022]
According to the above invention, when the operation amount of the grindstone exceeds the operation amount of the grindstone at which the sharpness of the grindstone decreases, the control means switches the rotation direction of the grindstone to the opposite direction, so that the workpiece can be accurately ground. Can be. Further, by switching the rotation direction of the grindstone, the sharpness of the grindstone can be recovered, and the grinding efficiency can be improved as compared with the case where dressing is performed.
[0023]
In the invention according to claim 8, there is provided a method of controlling a grinding device for controlling a rotation direction of a grindstone in two directions, wherein the sharpness of the grindstone is reduced during a grinding process in which the grindstone is rotated to grind a workpiece. Is detected, and when a decrease in the sharpness of the grindstone is detected, control is performed to switch the rotation direction of the grindstone to the opposite direction.
[0024]
According to the above invention, when the sharpness of the grindstone is reduced during the grinding process, the control means can switch the rotating direction of the grindstone to the opposite direction, and accurately grind the workpiece.
[0025]
9. The method according to claim 8, wherein the rotation direction of the grindstone is switched after the grinding of the workpiece being ground is completed.
[0026]
According to the above invention, when a decrease in the sharpness of the grindstone is detected, after the grinding of the work being ground is completed, the rotation direction of the grindstone is switched to the opposite direction, so that the processing accuracy of the work is reduced. Can be prevented.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings. Embodiments of the present invention will be described by taking as an example a case where a double-headed grinding device in a grinding device is used.
[0028]
FIG. 1 is a schematic view of a double-headed grinding apparatus according to an embodiment of the present invention. The X1 and X2 directions shown in the figure indicate the thrust direction which is the moving direction of the grindstone. The Y1 and Y2 directions indicate radial directions which are plane directions orthogonal to the X1 and X2 directions.
[0029]
First, an outline of a double-headed grinding apparatus will be described with reference to FIG. Since the left and right sides of the double-headed grinding device 20 shown in FIG. 1 have the same configuration, the configuration on the left side in FIG. , The description of the configuration shown on the left side in the figure will be mainly given by adding the reference b, and the description of the configuration added by the reference b will be omitted.
[0030]
As shown in the figure, the double-headed grinding device 20 generally includes grinding spindles 24a and 24b, saddles 23a and 23b, grinding spindle moving means 22a and 22b, and grinding spindle rotating means 35a and 35b as rotation driving means. Gantry 21, normal component force detecting means 36a and 36b as detecting means, and controlling means 37.
[0031]
First, the grinding spindle 24a will be described. The grinding main shaft 24a is roughly composed of an outer member 25a and an inner member 26a. The outer member 25a has a whetstone 32a formed at one end and a saddle 23a formed at the other end. A grinding operation surface 34a is formed on a surface of the grindstone 32a that contacts the work 33. A grinding spindle rotating motor rotor 41a is formed on the outer member 25a. The grinding spindle rotating motor rotor 41a is surrounded by the grinding spindle rotating motor rotor 41a in a state where there is a gap with respect to the grinding spindle rotating motor rotor 41a. A motor stator 39a is formed on the saddle 23a.
[0032]
The outer member 25a is configured to be rotatable with respect to the inner member 26a existing inside. Accordingly, the outer member 25a is rotated toward the workpiece 33 by the grinding spindle rotating means 35a and the grinding spindle moving means 22a, so that the grinding operation surface 34a contacts the workpiece 33 and the workpiece 33 is ground. . The work 33 is rotatably held by a work holder (not shown).
[0033]
The inner member 26a is supported by the saddle 23a and cooperates with the outer member 25a to contribute to infeed or outfeed to the work 33. The inner member has a thrust static pressure pad 27a, which is an opposed-type fluid bearing in the thrust direction (X1, X2 direction), and supports in the radial direction (Y1, Y2 direction, which is a plane direction orthogonal to the X1, X2 direction). Are formed. The thrust static pressure pad 27a is connected to the conduit 31a.
[0034]
Next, the saddle 23a, the grinding spindle rotating means 35a, and the grinding spindle moving means 22a will be described in this order. The saddle 23a is formed on the gantry 21 so as to be movable in the X1 and X2 directions. The grinding spindle moving means 22a is formed on the saddle 23a on the side opposite to the side on which the grinding spindle 24a is formed. The grinding spindle moving means 22a integrally moves the grindstone 32a, the outer member 25a, the grinding spindle rotating means 35a, and the saddle 23a in the X1 and X2 directions.
[0035]
Here, the grinding resistance used in the present invention will be described. The grinding force is a force for grinding the work 33, and the grinding force includes a normal component force and a main component force. The normal component force is a force acting in the thrust direction (X1, X2 directions). The main component force is a force acting in the radial direction (Y1, Y2 directions which are plane directions orthogonal to the X1, X2 directions).
[0036]
Next, a description will be given of the normal component force detecting means 36a as the detecting means. The normal component force detecting means 36a is connected to the control means 37 and the thrust static pressure pad 27a via the conduit 31a, and detects a change in the normal component force from the thrust static pressure pad 27a. It is for. The fluctuation of the normal component force is transmitted from the normal component force detection means 36a to the control means 37.
[0037]
Next, the control means 37 will be described. The control means 37 controls the rotation and the direction of rotation of the grinding spindle 24a by the grinding spindle rotating means 35a based on the fluctuation of the normal component force from the normal component force detecting means 36a. In the control means 37, a rotation direction switching level and a normal component excess level which are threshold values are set in advance. The rotation direction switching level is for determining that the sharpness of the grindstone 32a has been reduced. Further, the excessive normal component force level is, for example, when the load suddenly rises due to some abnormality or when there is an abnormality in the double-ended grinding device, the rotation of the grinding spindle 24a is stopped and the grinding of the work 33 is stopped. belongs to.
[0038]
The control means 37 determines that the sharpness of the grindstone 32a has decreased when the fluctuation of the normal component of the grindstone 32a in the grinding state exceeds the rotation direction switching level. When the variation of the normal component force exceeds the rotation direction switching level, the control means 37 sets the rotation direction of the grinding spindle 24a in the opposite direction by the grinding spindle rotating means 35a after the grinding of the workpiece 33 during the grinding is completed. Switch. In addition, since the grinding spindle 24a and the grindstone 32a rotate integrally, by switching the rotation direction of the grinding spindle 24a, the rotation direction of the grindstone 32a is also switched, and the sharpness of the grindstone 32a can be restored. When the normal component force detecting means 36a determines that the variation of the normal component force exceeds the excessive normal component force level, the control means 37 causes the grinding spindle rotating means 35a to rotate the grinding spindle 24a. The work is stopped and the grinding of the work 33 is stopped.
[0039]
Next, a method of switching the rotation direction of the grindstone 32a with the reduced sharpness will be described, taking as an example a case where the sharpness of one grindstone 32a of the double-head grinding device 20 is reduced. FIG. 2 is a diagram showing a transition of a normal component force of a grindstone having reduced sharpness, and FIG. 3 is a diagram showing a transition of a normal component force when an abnormality occurs during grinding. A to D shown in FIGS. 2 to 3 indicate A in a no-load operation state, B indicates a maximum normal component force, C indicates a rotation direction switching level, and D indicates an excessive normal component force level. T1 indicates an idle running state, and T2 indicates a grinding state.
[0040]
E shown in FIG. 2 indicates the fluctuation of the normal component force when the rotation direction switching level C is exceeded (hereinafter, fluctuation E), and T3 indicates that the fluctuation E of the normal component force is the rotation direction switching level C. (Time T3). In addition, T4 indicates a range of time (hereinafter, time zone T4) in which the rotation direction of the grindstone 32a with reduced sharpness can be switched. F shown in FIG. 3 indicates a fluctuation of the normal component force when the normal component force excess level D is exceeded (hereinafter, fluctuation F), and T5 indicates a method when there is an abnormality during grinding. The time when the fluctuation F of the line force exceeds the excessive line force level D (hereinafter, time T5) is shown. As shown in the range of the time T2 in FIG. 2, the grindstone 32b whose sharpness is not reduced can sufficiently grind the work 33. Therefore, the normal component force in the actual machining state is the maximum normal component force. Maintain the value of B.
[0041]
On the other hand, as shown in FIG. 2, the grindstone 32a having reduced sharpness cannot sufficiently grind the work 33, and therefore the fluctuation E of the normal component force of the grindstone 32a having reduced sharpness increases. Therefore, by setting the rotation direction switching level C in the control means 37, when it is detected that the fluctuation of the normal component force exceeds the rotation direction switching level C, the rotation direction of the grindstone 32a having reduced sharpness is reversed. You can switch to the direction. Switching of the rotation direction of the grindstone 32a having reduced sharpness can be performed during the time period T4, that is, after the grinding of the workpiece 33 in the grinding state is completed and before the next workpiece 33 is started. . By setting the rotation direction switching level C to, for example, a value that is 1.3 to 2.0 times the maximum normal component force B, it is possible to detect that the sharpness of the grindstone 32a has decreased.
[0042]
As shown in FIG. 3, the fluctuation F of the normal component force when there is an abnormality during the grinding is larger than the fluctuation E of the normal component force when the sharpness of the grindstone 32a is reduced. Therefore, when the normal component force excess level D is set in the normal component force detection means 34a, and it is detected that the fluctuation of the normal component force exceeds the normal component force excess level D, the grinding spindle 24a By stopping the rotation, the work 33 or the double-ended grinding device 20 can be prevented from being damaged. By setting the excessive normal component force level D to a value, for example, about 2.5 times the maximum normal component force B, it is possible to prevent the work 33 or the double-ended grinding device 20 from being damaged.
[0043]
With this configuration, when the fluctuation of the normal component force of the grindstone 32a having reduced sharpness exceeds the rotation direction switching level C, the rotation direction of the grindstone 32a having reduced sharpness is switched to the opposite direction, and the grindstone is changed. By recovering the sharpness of 32a, the workpiece 33 can be accurately ground. In addition, the frequency of dressing performed when the sharpness of the grindstones 32a and 32b is reduced can be reduced, and the grinding efficiency of the double-head grinding device 20 can be improved. Further, when the fluctuation of the normal component force exceeds the excessive normal component force level D, the rotation of the grinding spindle 24a is stopped, the grinding of the work 33 is stopped, and the load suddenly increases due to some abnormality. Alternatively, the double-headed grinding device 20 can be protected from damage. In addition, when the fluctuation of the normal component force of the grindstone 32a having reduced sharpness exceeds the rotation direction switching level C, the rotation directions of the two grindstones 32a and 32b may be switched. By switching the rotation direction of the two grindstones 32a and 32b in this manner, the difference in sharpness between the two grindstones 32a and 32b can be reduced, and the work 33 can be ground with higher precision. In addition, when the abrasive grains 15 are detached from the grindstones 32a and 32b or when the abrasive grains 15 are crushed, it is necessary to dress the grindstones 32a and 32b as needed and dress the grindstones 32a and 32b. .
[0044]
Next, a case will be described in which the rotation direction of the grindstone with reduced sharpness is switched by using the fluctuation of the main component force to the fluctuation of the grinding resistance. FIG. 4 is a schematic view of a double-head grinding apparatus provided with a current detecting means for detecting a fluctuation of the main component force. In FIG. 4, the same components as those of the double-headed grinding device 20 shown in FIG. 1 described above are denoted by the same reference numerals and description thereof is omitted. Further, since the configuration shown on the left side and the right side of the double-headed grinding device 30 shown in FIG. 4 is the same configuration, reference numeral a is added to the configuration on the left side in FIG. 4 and the configuration on the right side in FIG. , The description of the configuration shown on the left side in the figure will be mainly given by adding the reference b, and the description of the configuration added by the reference b will be omitted.
[0045]
As shown in FIG. 4, the double-disc grinding apparatus 30 includes a current detecting means 42a connected to a grinding spindle rotating motor rotor 41a, and a control means 43. The control means 43 calculates the difference between the two main component forces based on the change in the two main component forces from the current detection means 42a, and uses the difference between the two main component forces to determine the rotational direction of the grinding spindles 24a and 24b. Are controlled independently of each other.
[0046]
Next, the current detecting means 42a as the detecting means will be described. The current detecting means 42a is for detecting a change in the main component force generated when the sharpness of the grindstone 32a is reduced from the displacement of the current of the grinding spindle rotating motor stator 39a. The fluctuation of the main component is transmitted to the control means 43. The change in the main component force that occurs when the sharpness of the grindstone 32b is reduced is also transmitted to the control unit 43. Therefore, the change in the two main component forces is transmitted to the control unit 43.
[0047]
Next, the control means 43 will be described. In the control means 43, a rotation direction switching level which is a threshold value is set in advance. The control unit 43 calculates the difference between the two main component changes based on the two main component changes transmitted from the current detection units 42a and 42b, and determines the difference between the main component changes as the rotation direction switching level. The rotation direction of the grindstones 32a, 32b is switched by controlling whether the grinding spindle rotating means 35a, 35b is determined or not.
[0048]
The rotation direction switching level is for determining that the sharpness of the grindstones 32a and 32b is reduced. When the control unit 43 determines that the difference between the fluctuations of the two main component forces of the grindstones 32a and 32b in the grinding state has exceeded the rotation direction switching level, the control unit 43 has finished the grinding of the workpiece being ground. Thereafter, the rotation direction of the grindstones 32a, 32b is switched to the opposite direction by controlling the grinding spindle rotating means 35a, 35b. As described above, by switching the rotation direction of the grindstones 32a and 32b having reduced sharpness, the sharpness of the grindstones 32a and 32b can be recovered.
[0049]
FIG. 5 is a diagram showing a change in the main component force of a grindstone having a reduced sharpness, and FIG. 6 is a diagram showing a change in the main component force of a normal grindstone having a low sharpness. FIG. 7 is a diagram showing a transition of a difference in fluctuation of a main component force between a grindstone having reduced sharpness and a grindstone having not reduced sharpness. A, G, and H shown in FIGS. 5 to 7 indicate A in a no-load operation state, G indicates a maximum main component, and H indicates a rotation direction switching level. Further, T1 indicates an idle running state, T2 indicates a grinding state, and T7 indicates a range of time (hereinafter, time zone T7) in which the rotation direction of the grindstone with reduced sharpness can be switched. In FIG. 7, I indicates the fluctuation of the main component force when the rotation direction exceeds the rotation direction switching level H (hereinafter, fluctuation I), and T6 indicates that the fluctuation I of the main component force exceeds the rotation direction switching level H. Time (hereinafter, time T6).
[0050]
As shown in the range of time T2 in FIG. 5, in the actual machining state before the sharpness of the grindstone 32a decreases, the fluctuation of the main component force on the grindstone 32a side maintains the maximum main component force G. When the sharpness of the grindstone 32a decreases, the fluctuation of the main component force on the grindstone 32a side becomes gradually smaller than the maximum main component force G in the actual machining state. On the other hand, as shown in FIG. 6, the fluctuation of the main component force of the normal grindstone 32b maintains the maximum main component force G in the actual machining state before the sharpness of the grindstone 32a decreases, but the sharpness of the grindstone 32a is reduced. In the actual machining state after the reduction, the maximum main component G gradually increases. Therefore, as shown in FIG. 7, the difference between the fluctuations of the two main component forces after the sharpness of the grindstone 32a is reduced gradually increases.
[0051]
Therefore, by setting the rotation direction switching level H, which is a threshold value, when the absolute value of the difference between the fluctuations of the two main component forces exceeds the rotation direction switching level H, grinding of the workpiece 33 during grinding is performed. After the completion of the rotation, the rotation direction of the grindstone 32a having reduced sharpness can be switched to the opposite direction. Switching of the rotation direction of the grindstone 32a having reduced sharpness is performed during the time period T7, that is, after the grinding of the work 33 in the grinding state is completed and before the next work 33 is started. Can be. Further, when the absolute value of the difference between the fluctuations of the two main component forces exceeds the rotation direction switching level H, the rotation directions of the two grindstones 32a and 32b may be switched. By switching the rotation direction of the two grindstones 32a and 32b to perform the grinding of the workpiece 33, the workpiece 33 can be ground with higher accuracy. Note that the rotation direction switching level H can be set to 0.1 to 0.8 times the maximum main component G.
[0052]
With this configuration, when the absolute value of the difference between the fluctuations of the two main component forces exceeds the rotation direction switching level H, the rotation directions of the grindstones 32a and 32b whose sharpness is reduced are switched in opposite directions, and the accuracy is improved. The work 33 can be well ground. In addition, the frequency of dressing performed when the sharpness of the grindstones 32a and 32b is reduced can be reduced, and the grinding efficiency of the double-head grinding device 30 can be improved. Further, when the absolute value of the difference between the fluctuations of the two main component forces exceeds the rotation direction switching level H, the rotation directions of the two grindstones 32a and 32b may be switched. By switching the rotation direction of the two grindstones 32a and 32b in this manner, the difference in sharpness between the two grindstones 32a and 32b can be reduced, and the work 33 can be ground with higher precision. By setting the upper and lower thresholds for the main component force of one of the grindstones in the control means 43, the rotation direction of the grindstones 32a and 32b can be switched. When the abrasive grains 15 are detached from the grindstones 32a and 32b or when the abrasive grains 15 are crushed, it is necessary to dress the grindstones 32a and 32b as needed to sharpen the grindstones 32a and 32b.
[0053]
Next, with reference to FIGS. 8 and 9, a flowchart of a process of switching the rotation direction of the grindstones 32a and 32b with reduced sharpness performed by the double-headed grinding device 20 using the variation of the normal component force as the variation of the grinding resistance. This will be described with reference to FIG. 8 and 9 are diagrams showing a flowchart of a switching process of the rotation direction of the grindstone.
[0054]
As shown in FIG. 8, in STEP 50, the rotation direction and the number of rotations of the grindstones 32 a and 32 b necessary for grinding the work 33, the standby positions of the grinding spindles 24 a and 24 b, and the grindstones 32 a and 32 b contact the work 33. The grinding conditions such as the assumed contact position (hereinafter, assumed contact position) and the number of workpieces Mmax to be processed are input to a computer (not shown) in the double-head grinding apparatus.
[0055]
Subsequently, in STEP 51, the numerical value of the counter is initialized (M = 1). In the next STEP 52, when the grinding spindles 24a and 23b are activated from the standby position and move to the assumed contact position, the processing proceeds to STEP 53. In STEP 53, the grinding of the work 33 is started by the grindstones 32a and 32b from the state where the work 33 is in contact with the two grindstones 32a and 32b. In STEP 54, the sharpness of the grindstones 32a and 32b is determined. This determination of sharpness reduction is made based on, for example, whether or not the fluctuation of the normal component force of each of the grindstones 32a and 32b exceeds the rotation direction switching level C, as shown in FIG. If it is determined in STEP 54 that the grindstones 32a and 32b are clogged (Yes), the process proceeds to (1).
[0056]
Here, with reference to FIG. 9, a process after it is determined in STEP 54 that the sharpness of the grindstones 32a and 32b has been reduced (Yes) will be described. If it is determined in STEP 54 that the sharpness of the grindstones 32a and 32b has decreased (Yes), the process proceeds to STEP62. In STEP 62, when the fluctuation of the normal component exceeds the rotation direction switching level C, the grinding of the workpiece 33 which has been being ground is continuously performed. Subsequently, in STEP 63, it is determined whether or not the grinding of the workpiece 33 has been completed. If it is determined in step 63 that the grinding process has not been completed (No), the process returns to step 62. When it is determined that the grinding process has been completed (Yes), the process proceeds to STEP64.
[0057]
In STEP 64, the grinding spindles 24a and 24b move away from the workpiece 33 to the standby position, and the process proceeds to STEP 65. Subsequently, in STEP 65, the rotation direction of the grindstones 32a, 32b having reduced sharpness is switched to the opposite direction, and the process proceeds to STEP 66.
[0058]
In STEP 66, the counter is incremented. When the processing in STEP 66 is completed, the processing proceeds to (2), the processing returns between STEP 51 and STEP 52 shown in FIG. 15, and the processing after STEP 52 is performed. In the processing after STEP 52, the rotation direction of the grindstones 32a and 32b having reduced sharpness is switched to the opposite direction, so that the work 33 can be ground with high accuracy.
[0059]
If it is determined in STEP 54 that the sharpness of the grindstones 32a and 32b is not reduced (No), the process proceeds to STEP55. Subsequently, in STEP 55, a grinding abnormality determination is performed. This grinding abnormality determination is made based on, for example, whether or not the variation F of the normal component force has exceeded the excessive normal component force level D, as shown in FIG. 9 described above. If it is determined in STEP 55 that the condition is abnormal (Yes), the rotation of the grindstones 32a and 32b is stopped, and the grinding of the workpiece 33 is terminated halfway. As described above, by setting the excessive normal component force level D, it is possible to prevent a sudden increase in the load due to some abnormality and breakage of the double-headed grinding device.
[0060]
In the next STEP 56, it is determined whether or not the grinding of the work 33 has been completed. When it is determined that the grinding process has been completed (Yes), the process proceeds to STEP 57. If it is determined that the grinding has not been completed (No), the process returns to between STEP53 and STEP54, and STEP54 and STEP55 are repeated. In the next STEP 57, the grinding spindles 24 a and 24 b move away from the work 33 to the standby position, and then proceed to STEP 58. In STEP 58, the counter is incremented.
[0061]
Subsequently, in STEP 59, the work 33 on which grinding has been completed is recovered from the work holder, and the work 33 before grinding is inserted into the work holder. In STEP60, it is determined whether or not the number of the ground workpieces 33 exceeds Mmax input in STEP50. If it is determined that Mmax has not been exceeded (Yes), the process returns between STEP51 and STEP52, and STEPS from STEP54 to STEP55 are repeated. If it is determined that Mmax has been exceeded (Yes), the grinding processing of the work 33 is terminated.
[0062]
Note that the determination of sharpness deterioration of the grindstones 32a and 32b does not depend on the determination of the grinding abnormality in STEP55, and therefore STEP55 may or may not be provided in the flow. When the flow shown in FIGS. 8 to 9 is performed in the double-headed grinding apparatus 30 using the fluctuation of the main component force as the fluctuation of the grinding resistance, the flowchart shown in FIG. Can be done similarly. It is also possible to determine whether the sharpness of the grindstones 32a and 32b has decreased by using both the fluctuation of the normal component force and the fluctuation of the main component force as the fluctuation of the grinding force. By using the fluctuation of the normal component force and the fluctuation of the main component force, it is possible to improve the accuracy of determining the sharpness reduction of the grindstones 32a and 32b.
[0063]
Next, a method of switching the rotation direction of the grindstones 32a and 32b based on the preset operation amounts of the grindstones 32a and 32b will be described. The operating amount of the grindstones 32a and 32b refers to, for example, the number of processed workpieces 33 that have been ground by the grindstones 32a and 32b in a certain period of time, and the time during which the grindstones 32a and 32b have processed the workpieces. Next, referring to FIG. 10, a method of switching the rotation direction of the grindstones 32a and 32b when the number of processed workpieces 33 that have been ground by the grindstones 32a and 32b for a fixed time is used as the operation amount of the grindstones 32a and 32b. explain. FIG. 10 is a schematic diagram of a double-headed grinding device that switches the direction of rotation of a grindstone every time a set number of grinding processes are performed. In FIG. 10, the same components as those of the double-headed grinding device 20 shown in FIG. 1 described above are denoted by the same reference numerals, and description thereof is omitted.
[0064]
As shown in FIG. 10, the double-ended grinding device 90 includes a storage unit 91, a counting unit 92, and a control unit 93. The storage means 91 is connected to the control means 93, and the counting means 92 as the detection means is connected to the control means 93 and a computer (not shown) in the double-ended grinding device 90. The control means 93 is connected to the storage means 91, the counting means 92, and the grinding spindle rotating means 35a, 35b. The storage unit 91 stores in advance the number of processed workpieces 33 whose sharpness of the grindstones 32a and 32b is reduced. The number of processed workpieces 33 whose sharpness of the grindstones 32a and 32b is reduced depends on the types of the grindstones 32a and 32b, the type of the work 33, the grinding amount of the work 33, and the like. Further, the number of processed workpieces 33 whose sharpness of the grindstones 32a and 32b is reduced is determined by actually grinding the workpiece 33 in advance and evaluating the grindstones 32a and 32b.
[0065]
The counting means 92 counts the number of workpieces 33 that have been ground by the double-head grinding device 90. The control means 93 determines whether or not the number of the workpieces 33 counted by the counting means 92 exceeds the number of processed pieces of the grindstones 32a and 32b stored in the storage means 91 which decrease the sharpness. Is for switching the rotation direction of the two grindstones 32a, 32b to opposite directions by the grinding spindle rotating means 35a, 35b.
[0066]
With this configuration, the control unit 93 determines whether or not the number of ground workpieces 33 counted by the counting unit exceeds the number of processed grinding wheels 32 a and 32 b stored in the storage unit 91 that reduces the sharpness of the grindstones 32 a and 32 b. When the number of the ground workpieces 33 exceeds the number of processed workpieces stored in the storage unit 91, the rotation direction of the two grindstones 32a and 32b is switched to the opposite direction, and the workpiece 33 can be accurately determined. It can be ground. In addition, the frequency of dressing performed when the sharpness of the grindstones 32a and 32b is reduced can be reduced, and the grinding efficiency of the double-head grinding device 90 can be improved. In FIG. 10, the number of processed workpieces 33 is used as the operation amount of the grindstones 32 a and 32 b. However, the same applies when the time during which the grindstones 32 a and 32 b process the workpiece 33 is used instead of the number of processed workpieces 33. The effect of can be obtained. Further, when the abrasive grains 15 are detached from the grindstones 32a and 32b or when the abrasive grains 15 are crushed, it is necessary to dress the grindstones 32a and 32b as needed and sharpen the grindstones 32a and 32b. .
[0067]
Next, with reference to FIG. 11, a process of switching the rotation direction of the grindstones 32a and 32b performed by the double-head grinding device 90 will be described using a flowchart. FIG. 11 shows a flowchart for switching the rotation direction of the grindstone every time the set number of sheets is ground. As shown in FIG. 11, in STEP 73, the storage unit 91 stores the number Nx of processed workpieces 33 whose sharpness of the grindstones 32a and 32b is reduced. In the next STEP 74, the assumption is made that the rotation direction and the number of rotations of the grindstones 32a and 32b necessary for grinding the work 33, the standby positions of the grinding spindles 24a and 24b, and the grindstones 32a and 32b are brought into contact with the work 33. Grinding conditions such as a contact position (hereinafter, assumed contact position) and the number Nmax of processed workpieces 33 are input to a computer (not shown) in the double-disc grinding apparatus.
[0068]
In the following STEP75, the numerical value of the counter is initialized (M = 1). In the next STEP 76, the grinding spindles 24a and 24b are started from the standby position and moved to the assumed contact position. In STEP 77, the grinding of the work 33 is started by the grindstones 32a and 32b from the state where the work 33 is in contact with the two grindstones 32a and 32b, and in STEP78, the grinding of the subsequently drawn work 33 is performed.
[0069]
Next, in STEP 79, it is determined whether or not the grinding of the workpiece 33 has been completed. If it is determined in STEP 79 that the grinding processing has not been completed (No), the processing returns to between STEP 77 and STEP 78. If it is determined that the grinding process has been completed (Yes), the process proceeds to STEP80.
[0070]
In STEP80, the grinding spindles 24a and 24b move away from the workpiece 33 to the standby position, and the process proceeds to STEP81. In the following STEP 81, the counter is incremented. Subsequently, in STEP 82, the work 33 on which grinding has been completed is recovered from the work holder, and the work 33 before grinding is inserted into the work holder to replace the work 33, and the process proceeds to STEP 83.
[0071]
In STEP 83, it is determined whether or not the number of the ground workpieces 33 exceeds the number of processed pieces Nx input in STEP 73. If it is determined that it has exceeded (Yes), the process proceeds to STEP 85, in which the rotation direction of the two grindstones 32a and 32b is switched to the opposite direction, and the process proceeds between STEP 75 and STEP 76. If it is determined in STEP83 that the value does not exceed (No), the process proceeds to STEP84. Subsequently, in STEP 84, it is determined whether or not the value of the number N of the workpiece 33 that has been ground exceeds the Nmax input in STEP 74. If it is determined that the time has not exceeded (No), the process returns to between STEP75 and STEP76, and the process is performed. If it is determined in STEP 84 that it has exceeded (Yes), the grinding processing of the work 33 is terminated.
[0072]
As described above, the preferred embodiments of the present invention have been described in detail, but the present invention is not limited to such specific embodiments, and various modifications may be made within the scope of the present invention described in the appended claims. Deformation and modification are possible. Note that vibration, sound, or an optical microscope may be used as the detection means.
[0073]
【The invention's effect】
According to the first aspect of the present invention, when the detecting means detects a decrease in sharpness of the grindstone, the control means switches the rotation direction of the grindstone to the opposite direction to recover the sharpness of the grindstone, thereby accurately controlling the work. It can be ground. Further, the grinding efficiency of the grinding device can be improved as compared with the case where dressing of the grindstone is performed.
[0074]
According to the invention described in claim 2, when a decrease in sharpness of the grindstone is detected, the control means switches the rotation direction of the grindstone to the opposite direction after the grinding of the work being ground is completed. It is possible to prevent the processing accuracy from lowering.
[0075]
According to the third aspect of the invention, based on the fluctuation of the grinding resistance, the control means can detect that the sharpness of the grindstone has decreased, and switch the rotation direction of the grindstone to the opposite direction.
[0076]
According to the invention as set forth in claim 4, by setting the fluctuation value of the grinding resistance when the sharpness of the grindstone is reduced as the threshold value, when the fluctuation of the grinding resistance exceeds the threshold value, Upon determining that the sharpness has decreased, the control means can switch the rotation direction of the grindstone to the opposite direction.
[0077]
According to the fifth aspect of the present invention, since the control means independently controls the rotation directions of the two grinding wheels, the sharpness of the grinding wheel decreases when it is detected that the fluctuation value of the grinding resistance exceeds the threshold value. By switching the rotation direction of the grinding wheel on the opposite side to the opposite direction, the processing accuracy of the workpiece can be improved.
[0078]
According to the invention described in claim 6, the control means switches the rotation directions of the two grinding wheels to opposite directions when it is detected that the variation value of the grinding resistance exceeds the threshold value, so that the sharpness of the two grinding wheels is changed. Can be made equal. Therefore, the processing accuracy of the work can be further improved.
[0079]
According to the invention described in claim 7, when the operation amount of the grindstone exceeds the operation amount of the grindstone at which the sharpness of the grindstone decreases, the control unit switches the rotation direction of the grindstone to the opposite direction, so that the work can be accurately performed. It can be ground. Further, by switching the rotation direction of the grindstone, the sharpness of the grindstone can be recovered, and the grinding efficiency can be improved as compared with the case where dressing is performed.
[0080]
According to the invention described in claim 8, when a decrease in sharpness of the grindstone is detected during the grinding processing, the rotation direction of the grindstone is switched to the opposite direction, and the work can be accurately ground.
[Brief description of the drawings]
FIG. 1 is a schematic view of a double-headed grinding apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a transition of a normal component force of a grindstone having reduced sharpness.
FIG. 3 is a diagram showing a transition of a normal component force when an abnormality occurs during grinding.
FIG. 4 is a schematic diagram of a double-headed grinding apparatus provided with a current detecting means for detecting a fluctuation of a main component force.
FIG. 5 is a diagram showing a change in fluctuation of a main component force of a grindstone with reduced sharpness.
FIG. 6 is a diagram showing a transition of a change in a main component force of a normal grindstone whose sharpness is not reduced.
FIG. 7 is a view showing a transition of a difference in fluctuation of a main component force between a grindstone having reduced sharpness and a grindstone having not reduced sharpness.
FIG. 8 is a diagram (part 1) illustrating a flowchart of a switching process of the rotation direction of the grindstone.
FIG. 9 is a diagram (part 2) illustrating a flowchart of a process of switching the rotation direction of the grindstone.
FIG. 10 is a schematic diagram of a double-headed grinding apparatus that switches the rotation direction of a grindstone every time a set number of sheets is ground.
FIG. 11 is a diagram showing a flowchart for switching the rotation direction of the grindstone every time a set number of sheets are ground.
[Explanation of symbols]
20, 30, 90 Double-head grinding machine
21 Stand
22a, 22b Grinding spindle moving means
23a, 23b Saddle
24a, 24b Grinding spindle
25a, 25b Outer member
26a, 26b Inner member
27a, 27b Static pressure pad for thrust
29a, 29b Radial static pressure pad
31a, 31b pipe
32a, 32b whetstone
33 Work
34a, 34b Grinding operation surface
35a, 35b Grinding spindle rotating means
36a, 36b Normal component force detecting means
37, 43, 93 control means
39a, 39b Grinding spindle rotating motor stator
41a, 41b Grinding spindle rotating motor rotor
42a, 42b Current measuring means
91 storage means
92 counting means

Claims (8)

A grinding device in which the rotation direction of the whetstone can be switched between two directions,
Rotation driving means for grinding the work by rotating the grindstone,
Detection means for detecting a decrease in the sharpness of the whetstone,
A grinding unit, comprising: a control unit that switches a rotation direction of the grinding wheel to an opposite direction when a decrease in sharpness of the grinding wheel is detected by the detection unit. The control means, when a decrease in the sharpness of the grindstone is detected by the detection means during the grinding of the work, after the grinding of the work being ground is completed, the rotation direction of the grindstone is changed. The grinding device according to claim 1, wherein the switching is performed in an opposite direction. The detecting means detects a change in grinding resistance generated when the sharpness of the grinding wheel is reduced during the grinding of the work, and the control means detects a rotation direction of the grinding wheel based on the change in the grinding resistance. The grinding device according to claim 1 or 2, wherein the direction is changed in the opposite direction. A variable value of the grinding resistance when the sharpness of the grinding wheel is reduced is set as a threshold value, and the control unit switches the rotation direction of the grinding wheel to an opposite direction based on the threshold value. The grinding device according to claim 1. The grindstone is composed of two opposing grindstones, the control means independently controls the rotation directions of the two grindstones, and the control means controls the variation value of the grinding resistance to the threshold value. 5. The grinding apparatus according to claim 4, wherein when it is detected that the value exceeds the threshold value, the rotation direction of the grinding wheel on the side where the fluctuation value of the grinding resistance exceeds the threshold value is switched to the opposite direction. The grinding device according to claim 5, wherein the control unit switches the rotation directions of the two grinding wheels to opposite directions when it is detected that the fluctuation value of the grinding resistance exceeds the threshold value. . A grinding device in which the rotation direction of the whetstone can be switched between two directions,
Rotation driving means for grinding the work by rotating the grindstone,
Storage means for storing in advance the operating amount of the grindstone at which the sharpness of the grindstone decreases,
Detecting means for detecting the operation amount of the whetstone,
When the actual operation amount of the grindstone detected by the detection means exceeds the operation amount of the grindstone stored in the storage means, control means for switching the rotation direction of the grindstone to the opposite direction is provided. Features grinding equipment. A method for controlling a grinding device that controls a rotation direction of a grindstone in two directions,
During the grinding process of grinding the work by rotating the grindstone,
Detecting a decrease in the sharpness of the whetstone,
A control method for a grinding device, comprising: performing control to switch a rotating direction of the grinding wheel to an opposite direction when a decrease in sharpness of the grinding wheel is detected.

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