JP2004098250A - Double head grinding device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve grinding efficiency by shortening the predetermined time of a grinding cycle at a workpiece and to prevent the breakage of the workpiece and a double head grinding device by detecting the abnormality of the double head grinding device with regard to the double head grinding device where both sides of the workpiece such as the glass of an optical part and a semiconductor silicone wafer are ultraprecisely ground. <P>SOLUTION: A thrust pressure generated when the workpiece 110 is firmly fixed with the warp and deflection of the workpiece 110 absorbed is detected by two opposite grindstones 101 with the double head grinding device having a thrust static pressure pad 150, a thrust directional force detecting means 220 and a grinding spindle moving speed control means 221, the moving speed of the grinding spindle 140 is changed from fast-feed to grinding-feed by a grinding spindle moving means 180 to perform grinding. In addition, grinding can be suspended if an abnormality occurs by monitoring a thrust directional force from a grinding operation start time, thereby the breakage of the workpiece 110 and the double grinding device can be prevented. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a double-ended grinding apparatus, and more particularly to a double-ended grinding apparatus for grinding both surfaces of a workpiece such as glass of an optical component or a semiconductor silicon wafer with ultra-precision.
[0002]
[Prior art]
In a conventional double-headed grinding machine, from the viewpoint of improving the grinding efficiency, it is generally practiced to use a grinding wheel contact detection device to rapidly feed a grinding spindle provided with a grinding wheel until it comes into contact with a grinding surface of a work. Has been done. As a related art of such a grinding wheel contact detection device, a grinding wheel contact detection device using a vibration sensor, a sound wave sensor, and a rotational load sensor is disclosed (for example, see Patent Document 1).
[0003]
FIG. 1 shows a perspective view of a configuration of a grinding wheel contact detection device using a conventional vibration sensor.
[0004]
As shown in the figure, the grindstone contact detection device generally includes a moving frame 53 of a work holding mechanism and a vibration sensor 75.
[0005]
A mechanism (not shown) for fixing the work 17 is provided at the center of the moving frame 53 of the work holding mechanism. Further, the vibration sensor 75 as a detecting means is disposed on the upper surface on one side of the moving frame 53 of the work holding mechanism in the direction facing the grindstone 16. At the start of the grinding operation, the grindstone 16 provided on the grinding spindle 13 is rapidly moved toward the work 17 and comes into contact with the surface of the work 17.
[0006]
Thereafter, the vibration sensor 75 detects the mechanical vibration of the work 17 generated due to the contact, and outputs a signal. The detection signal is input to a CPU (not shown), and a grinding spindle movement control unit (not shown) ), A rotation speed switching signal is output. As a result, the feed movement of the grinding spindle 13 is switched from rapid feed to grinding feed.
[0007]
In this way, the grinding wheel contact detection device is provided in the double-headed grinding machine, and the grinding spindle is rapidly traversed from the start of the grinding operation until the workpiece comes into contact with the grinding wheel, thereby shortening the time required for the grinding cycle of the workpiece. As a result, the grinding efficiency can be improved.
[0008]
[Patent Document 1]
JP-A-10-277896.
[0009]
[Problems to be solved by the invention]
However, in the case of performing grinding using a double-headed grinding device, it is difficult to perform a suitable grinding process because the workpiece bends and the workpiece itself is warped.
[0010]
FIG. 2 is a diagram showing a positional relationship between the grindstone and the work when the conventional grindstone contact detection device detects the contact between the grindstone and the work.
[0011]
When switching the moving speed of the grinding spindle 140 using this grinding wheel contact detection device, as shown in FIG. 2, a time when a pair of grinding wheels 101 facing the work 110 are locally contacted is detected and grinding is performed. The moving speed of the spindle 140 is switched from rapid feed to grinding feed. At this time, since the work 110 is only in contact with the pair of grinding stones 101 facing each other, the work 110 is bent or warped. Further, since the work 110 is not firmly sandwiched between the pair of opposed grindstones 101, there is a space between the opposed pair of grindstones 101 for the work 110 to move.
FIG. 3 is a diagram showing a state in which the work is firmly sandwiched between a pair of grindstones facing each other in a state in which the warp, deflection, and the like of the work are absorbed.
[0012]
FIG. 4 is a diagram showing a change in the grinding time and the thickness of the workpiece after grinding with respect to the positional relationship between the grinding wheel and the workpiece. A shown by an arrow in the drawing indicates the thickness of the work 110. In addition, B shown by an arrow in the drawing indicates the cutting speed of the grindstone.
[0013]
In the figure, T ₁ The time indicated by, from the point in time when the work 110 locally contacts the grindstone 101, is firmly sandwiched between a pair of opposed grindstones 101 in a state in which the warp or deflection of the work 110 as shown in FIG. It shows the elapsed time during the contact processing until it is performed. FIG. ₂ The time indicated by is the time after Tx shown in FIG. 4 at which the work 110 is firmly sandwiched between the pair of grinding stones 101 in a state where the warp or the bending of the work 110 is absorbed as shown in FIG. This shows the elapsed time during actual machining.
[0014]
As shown in FIG. ₁ In the contact processing, the work 110 and the grindstone 101 are only in local contact with each other, so that the reduction amount of the thickness A of the work 110 with respect to the cutting speed B of the grindstone 101 is small, and sufficient grinding cannot be performed. . On the other hand, time T ₂ During actual machining, the workpiece 110 is firmly sandwiched between the grindstones 101, so that the cutting speed B of the grindstone 101 and the reduction amount of the thickness A of the workpiece 110 substantially match, and the desired grinding can be performed efficiently. You can see that.
[0015]
Further, the moving speed of the grinding spindle 140 is changed from a state in which the work 110 and the grindstone 101 are in contact as shown in FIG. 2 to a state in which the work 110 and the grindstone 101 are firmly sandwiched as shown in FIG. Performing this time by grinding feed not only reduces the amount of grinding described above, but also reduces the grinding cycle of the work 110. Furthermore, since the above-mentioned grindstone contact detecting device merely detects the contact between the grindstone 101 and the work 110, it cannot detect the abnormality of the work 110 or the double-headed grinding device during the grinding process.
[0016]
Accordingly, the present invention has been made in view of the above circumstances, and improves the grinding efficiency by shortening the time required for a work grinding cycle, and also detects an abnormality of a double-headed grinding device to damage the work and the double-headed grinding device. It is an object of the present invention to provide a double-headed grinding device that can also prevent the occurrence of the double-sided grinding.
[0017]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is characterized by taking the following means.
[0018]
In the invention according to claim 1, a grindstone, a feeding unit that moves the grindstone toward the work at a changed speed, and a detecting unit that detects a change in a processing force of the work by the grindstone in an actual processing state. Control means for changing the moving speed of the feed means to a second speed lower than the first speed when the detecting means detects a change in the working force in the actual working state. It can be solved by the device.
[0019]
According to the above invention, a change in the processing force in the actual processing state, which is a processing state in which the workpiece is firmly sandwiched by the grindstone, is detected, and the speed of the feeding means is set to the second speed in the actual processing state lower than the first speed. Since the speed can be changed, high-precision grinding can be performed and the grinding cycle can be improved.
[0020]
In the invention according to claim 2, the detection means is provided with an actual machining detection level, and the fluctuation of the machining force in the actual machining state of the work by the grindstone is detected to exceed the actual machining detection level. In this case, the double-head grinding apparatus according to claim 1, further comprising: the control means for changing a moving speed of the feed means to the second speed lower than the first speed.
[0021]
According to the invention described above, by providing the actual machining detection level in the detection means, when the variation in the machining force of the workpiece by the grindstone exceeds the actual machining detection level, it is determined that the grindstone and the workpiece are in the actual machining state. be able to. Thereby, when the fluctuation of the processing force of the work by the grindstone exceeds the actual processing detection level, the control means changes the moving speed of the feeding means to a second speed lower than the first speed, thereby changing the work speed. Can be ground with high precision and the grinding cycle can be improved.
[0022]
In the invention according to claim 3, the detecting means is provided with an excessive processing force level, and the fluctuation of the processing force in the actual processing state of the work by the grinding wheel is detected to exceed the excessive processing force level. In this case, the problem can be solved by the double-headed grinding device according to claim 1 or 2, wherein the feed means is stopped by the control means.
[0023]
According to the above invention, a large change in the processing force that occurs when an abnormality occurs in the work or the double-headed grinding device is detected by providing an excessively high processing force level, and the work or the double-ended grinding is stopped by stopping the feeding means. The device can be prevented from being damaged.
[0024]
According to a fourth aspect of the present invention, there is provided a double-head grinding apparatus according to any one of the preceding claims, wherein the detecting means detects a change in a thrust force in the actual machining state. it can.
[0025]
According to the above-mentioned invention, the actual machining state can be detected from the fluctuation of the thrust direction force. Further, from the fluctuation in the thrust direction force, it is possible to detect an abnormality occurring in the work being processed or the double-head grinding device.
[0026]
In the invention according to claim 5, the detecting means detects the change in the actual machining state using a fluid pressure on a fluid bearing surface of a grinding spindle. Solvable.
[0027]
According to the above invention, the thrust force can be detected by using the fluid pressure on the fluid bearing surface of the grinding spindle.
[0028]
In the invention according to claim 6, the detecting means detects the variation in the thrust direction force in the actual machining state using one element selected from the group consisting of an elastic body, a magnetostrictive element, a piezoelectric element, and a load cell. The problem can be solved by the double-headed grinding device according to the fourth aspect.
[0029]
According to the invention, an elastic body, a magnetostrictive element, a piezoelectric element, a load cell, or the like can be used as the thrust direction force detecting means.
[0030]
According to a seventh aspect of the present invention, there is provided a double-sided grinding apparatus according to any one of the first to third aspects, wherein the detecting means detects a change in a radial force in the actual machining state. it can.
[0031]
According to the above invention, a change in the actual machining state can be detected by using the radial force.
[0032]
According to an eighth aspect of the present invention, there is provided a double-headed grinding apparatus according to the seventh aspect, wherein the detection means uses an electric signal from a rotary motor for a grinding spindle.
[0033]
According to the above invention, the radial force can be detected by using the change in the electric signal from the grinding spindle rotating motor.
[0034]
According to the ninth aspect of the present invention, a whetstone, feed means for moving the whetstone at a different speed toward a work, and detecting a fluctuation of an output of a vibration sensor in an actual processing state of the work by the whetstone. Detecting means, after the first variation due to the contact state of the grinding wheel and the work is detected by the detecting means, when the actual machining state is detected as the second variation, the moving speed of the feed means The problem can be solved by a double-ended grinding device including a control means for changing the speed to a second speed lower than the first speed.
[0035]
According to the above invention, it is possible to determine whether or not the workpiece is in the actual machining state based on the detection of the second variation, which is the actual machining state, instead of the first variation due to the contact state between the grindstone and the work. In addition, since the moving speed of the feeding means can be switched to the second speed lower than the first speed in the actual machining state, highly accurate grinding can be performed, and the grinding cycle can be improved.
[0036]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings.
[0037]
FIG. 5 is a schematic diagram when the fluid pressure of the hydrostatic thrust pad according to the embodiment of the present invention is applied to a double-ended grinding device. X shown in FIG. ₁ X ₂ The direction indicates the thrust direction which is the moving direction of the grindstone 101. Also, Y ₁ Y ₂ Direction is X ₁ X ₂ A radial direction which is a plane direction orthogonal to the direction is shown.
[0038]
First, an outline of the double-ended grinding device will be described with reference to FIG.
[0039]
As shown in the figure, the double-headed grinding apparatus is roughly described, and a pair of opposed grinding spindles 140, grinding spindle moving means 180, saddle 170, gantry 200, thrust direction force detecting means 220, grinding spindle movement And speed control means 221.
[0040]
A grindstone 101 is provided at one end of a pair of grinding spindles 140 facing each other, and a saddle 170 is provided at the other end. The saddle 170 is movably provided on the gantry 200.
[0041]
Grinding spindle moving means 180 is provided on the side of the saddle 170 opposite to the side on which the grinding spindle 140 is provided. The grindstone 101, the grinding spindle 140, and the saddle 170 move integrally on the gantry 200 in the direction of the arrow shown in FIG. The thrust direction force detecting means 220 is connected to the thrust static pressure pad 150 provided inside the grinding spindle 140 by the wiring 210 by the wiring 210. The grinding spindle moving speed control means 221 is connected to the thrust direction force detecting means 220 and the grinding spindle moving means 180.
[0042]
Next, the grinding spindle 140 will be described.
[0043]
The grinding main shaft 140 is roughly composed of an outer member 120 and an inner member 130. The driving means for driving the outer member 120 and the inner member 130 may be any driving means as long as the driving means has sufficient accuracy with respect to a desired removal amount of the work 110.
[0044]
The outer member 120 has the grindstone 101 on one end surface. A grinding operation surface 190 is provided on a surface where the grindstone 101 contacts the work 110. The outer member 120 is configured to be rotatable with respect to the inner member 130 existing inside. Therefore, as the outer member 120 rotates toward the work 110, the work 110 is ground by the grinding operation surface 190.
[0045]
The inner member 130 is supported by a saddle 170, and the saddle 170 is fixed to the gantry 200 and cooperates with the outer member 120 to contribute to infeed or outfeed to the work 110. The inner member 130 is provided with a thrust static pressure pad 150, which is a fluid bearing of an opposed type in the thrust direction, and a radial static pressure pad 160 for supporting in the radial direction.
[0046]
The thrust static pressure pad 150 is connected to the thrust direction force detecting means 220 by a wiring 210. Further, the thrust direction force detecting means 220 is connected to the grinding spindle moving speed control means 221.
[0047]
Next, the thrust direction force detecting means 220 will be described.
[0048]
In the thrust direction force detecting means 220, an actual machining detection level and an excessive machining force level are set in advance as set values. The actual processing detection level is a set value for determining that the grindstone 101 and the work 110 are in the actual processing state. The excessive machining force level is a set value for stopping the moving speed of the grinding spindle 140 when a greater machining force is detected, for example, when there is an abnormality in the work 110 or the double-ended grinding device. is there.
[0049]
The thrust direction force detection means 220 determines that the change in the thrust direction force after the start of the grinding operation exceeds the actual processing detection level, and determines that the state is the actual processing state. I do. These determination results are sent to the grinding spindle moving speed control means 221 as detection signals.
[0050]
Next, the grinding spindle moving speed control means 221 will be described.
[0051]
The grinding spindle moving speed control means 221 is a means for causing the grinding spindle moving means 180 to change the moving speed of the grinding spindle 140 based on a detection signal from the thrust direction force detecting means 220. When the variation in the thrust direction force is determined to be in the actual machining state, the grinding spindle moving speed control unit 221 controls the grinding spindle moving unit 180 to set the moving speed of the grinding spindle 140 lower than the first speed (hereinafter, fast-forward movement). Switch to the second speed (hereinafter, grinding feed movement).
[0052]
When the thrust direction force detecting means 220 determines that the fluctuation of the thrust direction force exceeds the excessive processing force level, the grinding spindle moving speed control means 221 causes the grinding spindle moving means 180 to stop the grinding spindle 140. .
[0053]
Next, the thrust force and the radial force required to determine the actual machining state in the present embodiment will be described.
[0054]
When the force for processing the work 110 is defined as a processing force, the processing force is defined by a thrust direction force acting in a thrust direction, a radial direction force acting in a radial direction (rotation direction), and a work rotation direction force (feed component force). It can be divided into three.
[0055]
The thrust direction force is also referred to as the back force, more correctly the main shaft rotation axis direction force. The radial force is also referred to as the main component force, more correctly the main shaft rotational force.
[0056]
The thrust direction force refers to each of the forces applied to the grinding spindle 140 in an actual machining state in which the workpiece 110 is firmly sandwiched and ground by a pair of opposed grindstones 101 in a state where the bending and warpage of the workpiece 110 is absorbed. This is the reaction force in the direction opposite to the moving direction of the whetstone. On the other hand, the radial direction force is a reaction force applied to the grinding spindle 140 in the actual machining state in a direction opposite to the rotation direction of each grindstone 101.
[0057]
The processing force is not generated when the grindstone 101 and the work 110 are in contact. This is a force generated in an actual processing state in which the work 110 is firmly sandwiched and ground by a pair of grindstones 101 in a state where the bending and warpage of the work 110 are absorbed. Therefore, when the actual machining state is determined using the machining force, it can be determined whether or not the initial change in the thrust direction force exceeds the actual machining detection level.
[0058]
Further, the working force in the actual working state changes at a substantially constant value when the working is performed normally, but the working force increases when there is an abnormality in the work 110 or the double-headed grinding device. Accordingly, when the processing force exceeds the processing force excess level by setting the processing force excess level, the grinding spindle 140 can be stopped to protect the work 110 or the double-headed grinding device from damage.
[0059]
In the present embodiment, the variation in the thrust direction force received by the thrust hydrostatic pad 150 from the start to the end of the grinding operation is monitored, and when the thrust direction force exceeds the actual machining detection level, the grinding spindle 140 It controls the movement speed (switching, stopping, etc.). Therefore, the thrust static pressure pad 150 and the thrust direction force detecting means 220 constitute a detecting means described in claims. The control of the moving speed of the grinding spindle 140 can also be performed based on whether or not the radial force exceeds the actual processing start level.
[0060]
With this configuration, the thrust direction force detection means 220 detects the actual machining state when the variation in the thrust direction force received by the thrust static pressure pad 150 exceeds the actual machining start level, and moves the grinding spindle. A detection signal of the start of actual machining is sent to the speed control means 221, and the grinding spindle movement speed control means 221 can switch the movement speed of the grinding spindle 140 to a grinding feed movement slower than the rapid movement by the grinding spindle movement means 180. . If the machining force exceeds the excessive machining force level by setting the excessive machining force level in the thrust direction force detecting means 220, the grinding spindle 140 is stopped to protect the work 110 or the double-ended grinding device from damage. Can be.
[0061]
Next, the actual machining state when the machining force is used is defined.
[0062]
FIG. 6 shows the transition of the processing force during the normal grinding operation.
[0063]
T in FIG. ₀ Is idle, T ₁ Is a contact state where the work 110 and the grindstone 101 are in contact (hereinafter, a contact state T) ₁ ), T ₂ Is the actual machining state (hereinafter, actual machining state T) ₂ ) And C indicate the time when the machining force reaches the actual machining detection level (hereinafter, time C), and D indicates the variation (variation D) in the actual machining state.
[0064]
The maximum processing force shown in FIG. 4 is a processing force when the cutting speed B of the grindstone 101 shown in FIG. Further, as described above, the actual machining detection level is a set value for determining the actual machining state, and the excessive machining force level stops the moving speed of the grinding spindle 140 when a greater machining force is detected. This is the set value for
[0065]
Actual machining state T ₂ Is the contact state T in which the grindstone 101 and the work 110 are in contact with each other. ₁ Later, the grindstone 101 is further moved toward the work 110, and the work 110 is firmly sandwiched by the grindstone 101.
[0066]
As shown in FIG. 6, after the start of the grinding operation, there is an idle running state in which the work 110 and the grindstone 101 are not in contact with each other, and no processing force is generated during this state. Next, a contact state T in which the work 110 and the grindstone 101 are in contact with each other. ₁ In, the machining force changes almost without load, but the actual machining state T ₂ In this case, the work force is generated by firmly sandwiching the work 110 between the grindstones 101. Thereby, the contact state T is obtained by using the processing force. ₁ And actual machining state T ₂ And can be clearly distinguished. In the actual machining state, the machining force substantially maintains the value of the maximum machining force. Thereafter, in the state where the movement of the grinding spindle 140 is stopped, the grinding force of the work 110 is continued by the working force filled by the movement of the grinding spindle 140 so far, and the working force gradually decreases as shown in FIG. .
[0067]
In the present embodiment, the actual machining state is detected by the thrust direction force detecting means 220 because the actual machining state T shown in FIG. ₂ Is the timing of the time C at which the variation D of the machining force in the step S1 exceeds the actual machining detection level. When it is determined by the thrust direction force detecting means 220 that the workpiece is in the actual machining state, the grinding spindle moving speed control means 221 can switch the grinding spindle 140 to a grinding feed movement slower than the rapid moving movement of the grinding spindle 140 by the grinding spindle moving means 180. Become.
[0068]
By setting the value of the actual machining detection level to, for example, 0.2 to 0.5 times the maximum machining force, it is possible to distinguish the contact state between the workpiece 110 and the grindstone 101 and the actual machining state. it can. The no-load operation state is a state where there is no machining force. The processing power excess level is a level for stopping the processing and stopping the movement of the grinding spindle when there is an abnormality after the start of the grinding operation.
[0069]
The value of the excessive working force level can be set, for example, to a value between 1.1 and 2.0 times the maximum working force. When the set value of the excessive working force level is set lower, it can be detected that the grinding performance of the grindstone 101 has been reduced. Since the grinding performance of the grindstone 101 affects the processing shape of the work 110, it is effective when high-precision processing of the work 110 is required. In addition, when the set value of the excessive processing force level is set higher, it is possible to prevent the work 110 and the double-ended grinding device from being damaged.
[0070]
With this configuration, conventionally, the grinding spindle 140 has been moved by grinding feed from a contact state (hereinafter, a contact state) in which the work 110 has contacted the grindstone 101, but in the present invention, from the contact state to the start of actual machining. , The moving speed of the grinding spindle 140 can be rapidly moved. Therefore, the grinding cycle can be shortened, and the productivity is improved. Further, since the thrust direction force in the actual machining state changes at a substantially constant value, by monitoring the thrust direction force from the start to the end of the grinding operation, the work 110 or the double-sided grinding device during grinding is monitored. Abnormality can be recognized. Thus, when an abnormality occurs during the grinding, the grinding process can be stopped, and the work 110 and the double-ended grinding device can be prevented from being damaged.
[0071]
Next, another embodiment of the above embodiment will be described with reference to FIGS. 7 to 11, the same components as those shown in FIG. 5 are denoted by the same reference numerals, and the description thereof will be omitted. Further, X shown in FIGS. ₁ X ₂ The direction indicates the thrust direction which is the moving direction of the grindstone 101. Y ₁ Y ₂ Direction is X ₁ X ₂ A radial direction which is a plane direction orthogonal to the direction is shown.
[0072]
The configuration described with reference to FIG. 5 uses the thrust static pressure pad 150 as a means for detecting the thrust direction force. However, other means for detecting the thrust direction force can be used.
[0073]
FIG. 7 shows an embodiment in which an elastic body and an elastic mechanism for detecting a thrust direction force are applied to a double-ended grinding device.
[0074]
The double-headed grinding apparatus shown in FIG. 1 is characterized by using an elastic body for detecting a thrust direction force, an elastic mechanism 231 and a displacement measurement unit 230 as means for detecting a thrust direction force.
[0075]
That is, the double-headed grinding apparatus according to the present embodiment includes the grinding spindle moving speed control means 221, and the X-axis between the grinding spindle 140 and the grinding spindle moving means 180. ₁ X ₂ The direction is supported by an elastic body and an elastic mechanism 231, and the saddle is provided with a displacement measuring unit 230.
[0076]
The displacement measuring means 230 measures the displacement of the elastic body and the elastic mechanism 231. Further, when the detected thrust direction force exceeds the actual machining detection level set in advance in the displacement measuring unit 230, the displacement measuring unit 230 detects the start of the actual machining state. The detection signal indicating the start of the actual machining state is sent from the displacement measuring means 230 to the grinding spindle moving speed control means 221. Then, the grinding spindle moving speed control unit 221 sends a moving speed change command to the grinding spindle moving unit 180, and the moving speed of the grinding spindle 140 is changed from the rapid feed movement to the grinding feed movement.
[0077]
Further, when the thrust direction force exceeds the excessive working force level set in advance by the displacement measuring means 230, a detection signal of excessive working force is sent from the displacement measuring means 230 to the grinding spindle moving speed control means 221. Then, the grinding spindle moving speed control means 221 sends a command to stop the movement to the grinding spindle moving means 180, and the movement of the grinding spindle 140 is stopped.
[0078]
FIG. 8 shows an embodiment in which a load cell for detecting a thrust direction force is applied to a double-headed grinding device.
[0079]
The double-headed grinding apparatus shown in FIG. 1 is characterized in that a load cell 240 for detecting a thrust direction force and a load cell load measuring means 241 are used as means for detecting a thrust direction force. That is, the double-headed grinding apparatus according to the present embodiment includes the grinding spindle moving speed control means 221, and the X-axis between the grinding spindle 140 and the grinding spindle moving means 180. ₁ X ₂ The direction is supported by the load cell 240.
[0080]
Then, by measuring the load of the load cell 240, the load cell load measuring means 241 detects the start of the actual machining state. The detection signal indicating the start of the actual machining state is sent from the load cell load measuring means 241 to the grinding spindle moving speed control means 221. Then, the grinding spindle moving speed control unit 221 sends a moving speed change command to the grinding spindle moving unit 180, and the moving speed of the grinding spindle 140 is changed.
[0081]
If the thrust force exceeds the excessive machining force level preset in the load cell load measuring means 241, a detection signal of excessive machining force is sent from the load cell load measuring means 241 to the grinding spindle moving speed control means 221. . Then, the grinding spindle moving speed control means 221 sends a command to stop the movement to the grinding spindle moving means 180, and the movement of the grinding spindle 140 is stopped.
[0082]
Although the load cell 240 is used in the figure, the actual machining state can be similarly detected by measuring the displacement using a magnetostrictive element or a piezoelectric element instead of the load cell 240.
[0083]
FIG. 9 shows an embodiment in which the driving force detecting means for detecting the thrust direction force is applied to a double-head grinding device.
[0084]
The double-ended grinding apparatus shown in FIG. 1 is characterized in that a driving force detecting means 250 for detecting a thrust direction force is used as a means for detecting a thrust direction force. That is, the double-headed grinding apparatus according to the present embodiment includes the grinding spindle moving speed control means 221, and the driving force detecting means 250 is connected to the grinding spindle moving means 180.
[0085]
Then, by measuring the driving force of the grinding spindle moving means 180, the driving force detecting means 250 detects the start of the actual machining state. A detection signal indicating the start of the actual machining state is sent from the driving force detection means 250 to the grinding spindle moving speed control means 221. Then, the grinding spindle moving speed control unit 221 sends a moving speed change command to the grinding spindle moving unit 180, and the moving speed of the grinding spindle 140 is changed.
[0086]
When the thrust direction force exceeds the excessive machining force level set in advance in the driving force detection means 250, a detection signal of excessive machining force is sent from the driving force detection means 250 to the grinding spindle moving speed control means 221. . Then, the grinding spindle moving speed control means 221 sends a command to stop the movement to the grinding spindle moving means 180, and the movement of the grinding spindle 140 is stopped.
[0087]
FIG. 10 shows an embodiment in which a grinding spindle rotating motor stator for detecting a radial direction force, a grinding spindle rotating motor rotor, and current measuring means are applied to a double-head grinding apparatus.
[0088]
The double-headed grinding apparatus shown in FIG. 1 uses a grinding spindle rotating motor stator 260 for detecting radial force, a grinding spindle rotating motor rotor 261, and a current measuring means 271 as means for detecting radial force. It is characterized by the following.
[0089]
That is, the double-headed grinding device according to the present embodiment includes the grinding spindle moving speed control means 221, and a gap exists between the grinding spindle rotating motor stator 260 attached to the outer member and the grinding spindle rotating motor stator 260. It is composed of a grinding spindle rotating motor rotor 261 formed so as to surround it in a state where it has been formed, and a current measuring means 271 connected to the grinding spindle rotating motor stator 260.
[0090]
Then, the current measuring means 271 detects the start of the actual machining state by using the radial force generated by the rotation of the grinding spindle 140 by the current displacement of the grinding spindle rotating motor rotor 261. The detection signal indicating the start of the actual machining state is sent from the current measuring means 271 to the grinding spindle moving speed control means 221. Then, the grinding spindle moving speed control unit 221 sends a command for changing the moving speed to the grinding spindle moving unit 180, and the moving speed of the grinding spindle 140 is changed.
[0091]
When the radial force exceeds the excessive machining force level preset in the current measuring unit 271, a detection signal of excessive machining force is sent from the current measuring unit 271 to the grinding spindle moving speed control unit 221. Then, the grinding spindle moving speed control means 221 sends a command to stop the movement to the grinding spindle moving means 180, and the movement of the grinding spindle 140 is stopped.
[0092]
As described above, the radial force is generated by the rotation of the grinding spindle 140 and is generated in the radial direction (Y ₁ Y ₂ Direction). The radial processing force can also detect the actual machining state. Therefore, after detecting the actual machining state, the moving speed of the grinding spindle 140 can be switched from fast-forward to grinding-feed.
[0093]
Therefore, the grinding cycle can be shortened, and the productivity is improved. Further, the radial force during grinding also changes substantially constant during the actual machining state, similarly to the thrust force. Therefore, by utilizing the radial force, when an abnormality occurs during grinding and the radial force exceeds the excessive processing force level, the movement of the grinding spindle 140 is stopped, and the work 110 and the double-ended grinding device are stopped. Can be prevented from being damaged.
[0094]
FIG. 11 shows an embodiment in which a grinding spindle rotation reaction force measuring means for detecting a radial force is applied to a double-head grinding apparatus when a direct drive grinding spindle rotation motor is employed.
[0095]
The double-headed grinding device shown in FIG. 6 includes a grinding spindle rotating motor stator 260, a grinding spindle rotating motor rotor 261 as means for detecting a reaction force signal of a motor mounting portion when a direct drive grinding spindle rotating motor is employed. The present invention is characterized in that a grinding spindle rotation reaction force measuring means 280 is used.
[0096]
That is, the double-headed grinding apparatus according to the present embodiment includes the grinding spindle moving speed control means 221 and has a gap between the grinding spindle rotating motor stator 260 attached to the outer member and the grinding spindle rotating motor stator 260. It is composed of a grinding spindle rotating motor rotor 261 formed so as to surround it in a state where it has been formed, and a grinding spindle rotating reaction force measuring means 280 fixed to the saddle 170.
[0097]
Then, the grinding spindle rotation reaction force measuring means 280 detects the start of the actual machining state based on the radial force generated by the rotation of the grinding spindle 140 by the reaction force signal of the grinding spindle rotation motor rotor 261. The detection signal indicating the start of the actual machining state is sent from the grinding spindle rotation reaction force measuring means 280 to the grinding spindle moving speed control means 221. Then, the grinding spindle moving speed control unit 221 sends a command for changing the moving speed to the grinding spindle moving unit 180, and the moving speed of the grinding spindle 140 is changed.
[0098]
If the radial force exceeds the excessive machining force level preset in the grinding spindle rotation reaction force measuring means 280, the grinding spindle rotation reaction force measuring means 280 sends the machining power excessive control to the grinding spindle movement speed control means 221. Is sent. Then, the grinding spindle moving speed control means 221 sends a command to stop the movement to the grinding spindle moving means 180, and the movement of the grinding spindle 140 is stopped.
[0099]
As described above, also in the above-described configurations of FIGS. 7 to 11, since the thrust force or the radial force can be detected, the actual machining state can be detected. After the actual machining state is detected, the moving speed of the grinding spindle 140 is rapidly moved ( It is possible to switch from the first speed) to the grinding feed movement (second speed).
[0100]
With such a configuration, conventionally, the grinding spindle 140 is moved by the grinding feed from the contact state in which the pair of grindstones 101 facing the work 110 are in contact with each other. During this, the grinding spindle 140 can be rapidly moved. Therefore, the cycle can be shortened, and the productivity is improved. Further, since the thrust direction force and the radial direction force during the grinding change substantially constant, an abnormality during the grinding can be known from the fluctuation of the thrust direction force and the radial direction force. Thus, if an abnormality occurs during the grinding, the grinding can be stopped, and the work 110 and the double-ended grinding device can be prevented from being damaged.
[0101]
In the double-headed grinding apparatus shown in FIGS. 6 to 11, the means for detecting the thrust force or the radial force and the control means for the grinding spindle 140 are provided on only one of the two opposed grinding spindles 140. However, the same means as the one shown may be provided on the side of the grinding spindle 140 not shown in the figure. Further, the various detection means shown in FIGS. 6 to 11 may be provided on both sides. With such a configuration, the same operation and effect as those described above can be obtained.
[0102]
Next, a description will be given of a change in the processing force when an abnormality is found after the start of the grinding operation and a measure to be taken in that case.
[0103]
FIG. 12 shows an example of a change in the machining force when an abnormality occurs when the actual machining state is detected. In the figure, E indicates a change in the machining force (hereinafter, a change E) when an abnormality occurs when the actual machining state is detected.
[0104]
The state as shown in the figure is, for example, a case where the workpiece 110 is ground as it is in the rapid traverse movement after the actual processing start detection is delayed. In such a case, it is determined that the state is abnormal because the machining force suddenly increases and the variation E exceeds the excessive machining force level. Then, the grinding is stopped, and the movement of the grinding spindle 140 is stopped. By setting the excessive processing force level in this way, it is possible to prevent the work 110 and the double-ended grinding device from being damaged during the grinding operation.
[0105]
FIG. 13 shows an example of a change in the processing force when an abnormality occurs during the actual processing state. In the figure, E is a change in the machining force when an abnormality occurs during the actual machining state.
[0106]
The state shown in the figure is, for example, a case where the grinding wheel 101 is clogged and the grinding performance is reduced, or a case where the moving speed of the grinding spindle 140 is excessive. In such a case, since the processing force increases and exceeds the excessive processing force level, it is determined that the state is abnormal, and the grinding is stopped and the movement of the grinding spindle 140 is stopped. By setting the excessive processing force level in this way, it is possible to prevent the work 110 and the double-ended grinding device from being damaged during the grinding operation.
[0107]
Next, a case in which a vibration sensor is provided in the double-ended grinding device to detect an actual machining state will be described.
[0108]
First, the configuration of a double-headed grinding device provided with a vibration sensor will be described.
[0109]
By providing a vibration sensor in the double-headed grinding device near the mounting portion of the roller for holding the work of the work holder, the actual machining state can be detected based on the output from the vibration sensor.
[0110]
In addition, the method of measuring the output from the vibration sensor is performed by taking a voltage signal from an amplifier provided in the vibration sensor into a computer via an A / D converter.
[0111]
For example, an AE sensor can be used as the vibration sensor.
[0112]
The voltage signal (hereinafter, voltage signal data) taken into the computer is data in which the power level is not stable, so that it is difficult to determine the contact state and the actual processing state. Therefore, a process of averaging the voltage signal data is performed.
[0113]
In this embodiment, an exponential averaging method is used as a method for averaging the voltage signal data. The exponential averaging processing method is represented by the following equation when the data before processing is A (n) and the data after processing is B (n).
[0114]
B (1) = A (1), B (n) = k * A (n) + (1-k) * B (n-1)
In the above formula, n ≧ 2 is used for the range of n, and 0 <k <1 is used for the range of the averaging parameter value k. Actually, the value of the averaging parameter value k is appropriately set in consideration of the averaging effect and signal delay.
[0115]
In the case of the present embodiment, for example, the voltage signal data can be sufficiently averaged by setting the value of the averaging parameter value k to 0.02.
[0116]
Next, a method of detecting the actual machining state based on the voltage signal data averaged by the above exponential averaging processing method will be described.
[0117]
FIG. 14 shows the transition of the output value of the vibration sensor during a normal grinding operation when using a double-head grinding device provided with a vibration sensor.
[0118]
T in FIG. ₀ Indicates the idle running state (hereinafter, idle running state T) ₀ ), T ₁ Is a contact state where the work 110 and the grindstone 101 are in contact (hereinafter, a contact state T) ₁ ), T ₂ Is the actual machining state (hereinafter, actual machining state T) ₂ ) And H represent a first variation (hereinafter variation H) occurring in the contact state, and I represents a second variation (hereinafter variation I) occurring in the actual machining state.
[0119]
The output of the vibration sensor shown in the figure is the voltage signal data described above, and the average of the output of the vibration sensor by the exponential averaging processing method is the averaged vibration sensor output.
[0120]
Further, as shown in the figure, a contact state detection level for detecting a first variation in which the work 110 is in contact with the grindstone 101 is provided. The value of the contact state detection level can be, for example, 1.5V.
[0121]
As shown in the figure, since the averaged vibration sensor output value of the vibration sensor fluctuates between the contact state and the actual machining state in the same manner as the spindle motor current value, even when the vibration sensor is used, The processing state can be detected.
[0122]
As shown in the figure, after the start of the grinding operation, the idle running state T in which the workpiece 110 and the rotating grindstone 101 are not in contact with each other. ₀ There is. Next, a contact state T in which the workpiece 110 and the rotating grindstone 101 are in contact with each other. ₁ Then, the contact state between the workpiece 110 and the grindstone 101 is detected when the change H, which is the first change, exceeds the contact state detection level. Also, the contact state T ₁ In, vibration occurs when the rotating grindstone 101 comes into contact with the uneven portions existing on both surfaces of the work 110 before grinding, so that the averaged vibration sensor output gradually increases.
[0123]
Thereafter, in a state where the work 110 and the grindstone 101 are in contact with each other, the grindstone 101 further moves toward the work 110, and the work 110 is slightly ground, so that uneven portions existing on both surfaces of the work 110 before grinding are removed. It becomes smaller and reaches the actual machining state. Actual machining state T ₂ In this case, since the uneven portions existing on both surfaces of the work 110 are gradually smoothed, the value of the averaged vibration sensor output decreases accordingly.
[0124]
By detecting the variation I, which is the second variation, due to the decrease in the output value of the averaged vibration sensor, it is determined that the workpiece is in the actual machining state, and the moving speed of the grinding spindle 140 is changed from the first speed, rapid traverse. Can be switched to the second speed, the grinding feed.
[0125]
In the above embodiment, the actual processing state is detected by using the exponential averaging processing method. However, a method of processing the voltage signal data by using a digital filter (low-pass, band-pass) provided in the computer. Also, even when a method of processing a voltage signal before being taken into a computer by using an analog filter (low-pass, band-pass) provided in the computer is used, the actual processing state can be detected. is there. In this embodiment, the actual machining state is determined using the vibration sensor. However, the actual machining state can be similarly detected by using a sound wave sensor instead of the vibration sensor.
[0126]
With this configuration, the actual machining state can be detected, and the moving speed of the grinding spindle 140 can be switched from rapid traverse to grinding traverse. Therefore, the grinding cycle can be shortened, and the productivity is improved.
[0127]
Next, a description will be given of a grinding process performed by the double-ended grinding device in the present embodiment.
[0128]
FIG. 15 is a flowchart showing the grinding process.
[0129]
Normally, before starting the grinding operation, a standby position of the grinding spindle 140 and an assumed contact position assumed to be in contact with the workpiece 110 are input to the double-head grinding device. Thereafter, the grinding spindle 140 is started from the standby position and performs the assumed contact position movement (step 311).
[0130]
At this time, the moving speed of the grinding spindle 140 is set to be higher than the grinding feed during the grinding, for example, 1 mm / min or more. When the distance between the standby position and the assumed contact position is 0.01 mm to 1 mm or more, the robot moves at a high speed of 1 mm / min to 10 mm / min or more up to 0.01 mm to 1 mm before the assumed contact position. After that, the speed is reduced to about 0.01 mm / min to 10 mm / min and moves to the assumed contact position. Thus, it is possible to shorten the grinding cycle and prevent troubles caused by excessive movement of the grinding spindle 140 when the actual machining state is detected. As described above, the moving speed of the grinding spindle 140 may be divided into multiple stages.
[0131]
When the grinding spindle 140 moves from the standby position to the assumed contact position by the process of step 311, the process proceeds to step 321. In step 321, an abnormality is determined in the actual machining state. This abnormality determination is made based on, for example, whether or not the machining force has exceeded the excessive machining level after the machining force has exceeded the actual machining detection level as shown in FIG.
[0132]
If it is determined in step 321 that there is an abnormality, the process proceeds to step 391, in which the movement of the grinding spindle 140 is stopped, and the machining is terminated halfway. As described above, by setting the excessive working force level, it is possible to prevent the work 110 and the double-ended grinding device from being damaged during the grinding operation.
[0133]
On the other hand, if it is determined in step 321 that the state is normal, the process proceeds to step 331, and a determination process of the actual machining state is performed. The process of determining the actual machining state is determined based on whether the machining force has normally exceeded the actual machining detection level.
[0134]
If the actual machining state is not detected in step 331, the process returns to between step 311 and step 321, and steps 321 and 331 are repeated.
[0135]
On the other hand, if the actual machining state is detected in step 331, the process proceeds to step 341, the moving speed of the grinding spindle 140 is switched to the grinding feed, the actual machining is started, and the process proceeds to step 351. In this manner, by setting the grinding spindle 140 to the grinding feed movement after the detection of the actual machining state, the speed of the grinding feed movement and the removal amount of the work 110 can be made substantially equal. Therefore, the work 110 can be efficiently ground. Further, since the time for the grinding feed movement can be shortened, the grinding cycle can be improved and the productivity can be improved.
[0136]
Next, if it is determined in step 351 that there is an abnormality, the process proceeds to step 391, in which the movement of the grinding spindle 140 is stopped, and the grinding is terminated halfway. In this way, by setting the excessive working force level, it is possible to prevent the workpiece 110 and the double-ended grinding device from being damaged in the actual working state.
[0137]
On the other hand, if it is determined in step 351 that it is normal, the process proceeds to step 361, and it is determined whether or not the actual machining has been completed.
[0138]
If the actual machining state is not detected in step 361, the process returns to between step 341 and step 351, and steps 351 and 361 are repeated.
[0139]
On the other hand, if it is determined in step 361 that the desired grinding process has been completed, the actual machining is completed, and the process proceeds to step 371, where the grinding spindle 140 moves to the standby position, and proceeds to step 381 to grind the workpiece 110. Processing ends normally.
[0140]
In the processing of the workpiece 110, various processes exist before and after the grinding. When processing a plurality of workpieces 110 in succession, the above processes may be combined so that the processing time is minimized.
[0141]
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.
[0142]
【The invention's effect】
According to the first aspect of the present invention, a change in the processing force in the actual processing state in which the workpiece is firmly sandwiched by the grindstones is detected, and the speed of the feeding means is set to a value lower than the first speed. Can be changed to the second speed, so that highly accurate grinding can be performed and the grinding cycle can be improved.
[0143]
According to the second aspect of the present invention, by providing the actual machining detection level to the detection means, when the fluctuation of the machining force of the work by the grindstone exceeds the actual machining detection level, the grindstone and the workpiece are brought into the actual machining state. It can be determined that there is. Thereby, when the fluctuation of the processing force of the work by the grindstone exceeds the actual processing detection level, the control means changes the moving speed of the feeding means to a second speed lower than the first speed, thereby changing the work speed. Can be ground with high precision and the grinding cycle can be improved.
[0144]
According to the invention as set forth in claim 3, a large change in the processing force that occurs when an abnormality occurs in the work or the double-headed grinding device is detected by providing an excessively high processing force level, and the feeding means is stopped. The work and the double-headed grinding device can be prevented from being damaged.
[0145]
According to the fourth aspect of the invention, the actual machining state can be detected from the fluctuation of the thrust direction force. Further, from the fluctuation in the thrust direction force, it is possible to detect an abnormality occurring in the work being processed or the double-head grinding device.
[0146]
According to the fifth aspect of the invention, the thrust force can be detected by using the fluid pressure on the fluid bearing surface of the grinding spindle.
[0147]
According to the invention described in claim 6, an elastic body, a magnetostrictive element, a piezoelectric element, a load cell, or the like can be used as the thrust direction force detecting means.
[0148]
According to the seventh aspect of the invention, a change in the actual machining state can be detected by using the radial force.
[0149]
According to the eighth aspect of the invention, the radial force can be detected by using the change in the electric signal from the grinding spindle rotating motor.
[0150]
According to the ninth aspect of the invention, it is determined whether or not the workpiece is in the actual machining state based on the detection of the second variation, which is the actual machining state, instead of the first variation due to the contact state between the grindstone and the work. Can be. In addition, since the moving speed of the feeding means can be switched to the second speed lower than the first speed in the actual machining state, highly accurate grinding can be performed, and the grinding cycle can be improved.
[Brief description of the drawings]
FIG. 1 is a perspective view of a configuration of a grinding wheel contact detection device using a conventional vibration sensor.
FIG. 2 is a diagram illustrating a positional relationship between a grindstone and a work when a conventional grindstone contact detection device detects contact between the grindstone and the work.
FIG. 3 is a diagram showing a state in which the work is firmly sandwiched between a pair of grindstones facing each other in a state in which the warp, deflection, and the like of the work are absorbed.
FIG. 4 is a diagram showing a transition of a grinding time and a thickness of a work after grinding with respect to a positional relationship between a grindstone and a work.
FIG. 5 is a schematic diagram when a fluid pressure of a hydrostatic pad for thrust according to an embodiment of the present invention is applied to a double-head grinding device.
FIG. 6 shows a transition of a processing force during a normal grinding operation.
FIG. 7 is an embodiment in which an elastic body and an elastic mechanism for detecting a thrust direction force are applied to a double-ended grinding device.
FIG. 8 is an embodiment in which a load cell for detecting a thrust direction force is applied to a double-headed grinding device.
FIG. 9 is an embodiment in which a driving force detecting means for detecting a thrust direction force is applied to a double-head grinding device.
FIG. 10 is an embodiment in which a grinding spindle rotating motor stator for detecting a radial force, a grinding spindle rotating motor rotor, and current measuring means are applied to a double-head grinding apparatus.
FIG. 11 shows an embodiment in which a grinding spindle rotation reaction force measuring means for detecting a radial force is applied to a double-head grinding apparatus when a direct drive grinding spindle rotation motor is employed.
FIG. 12 is an example of a change in machining force when an abnormality occurs during detection of an actual machining state.
FIG. 13 is an example of a change in machining force when an abnormality occurs during the actual machining state.
FIG. 14 shows the transition of the output value of the vibration sensor during a normal grinding operation when using a double-head grinding device provided with a vibration sensor.
FIG. 15 is a flowchart showing a grinding process.
[Explanation of symbols]
13,140 Grinding spindle
16, 101 whetstone
17, 110 work
53 Moving frame of work holding mechanism
75 Vibration sensor
120 outer member
130 Inner member
150 Static pressure pad for thrust
160 Static pressure pad for radial
170 saddle
180 Grinding spindle moving means
190 Grinding operation surface
200 stand
210 Wiring
220 Thrust direction force detecting means
221 Grinding spindle moving speed control means
230 Displacement measuring means
231 Elastic body and elastic mechanism
240 load cell
241 Load cell load measuring means
251 Driving force detection means
260 Grinding spindle rotating motor stator
261 Grinding spindle rotating motor rotor
271 Current measuring means
280 Grinding spindle rotation reaction force measuring means
311 Movement of assumed contact position
321 Actual machining start abnormality judgment
331 Actual machining start judgment
341 Start of grinding feed movement
351 Actual machining abnormality judgment
361 Actual machining end judgment
371 Move to standby position
381 Successful completion
391 Ending prematurely

Claims (9)

Grinding stone, feed means for moving the grinding stone at a different speed toward the workpiece,
Detecting means for detecting a change in the processing force of the work by the whetstone in an actual processing state,
A control means for changing a moving speed of the feed means to a second speed lower than a first speed when the detecting means detects a change in the working force in the actual working state. . The detecting means is provided with an actual machining detection level, and when a change in the machining force in the actual machining state of the workpiece by the grindstone is detected to exceed the actual machining detection level, the moving speed of the feed means 2. The double-head grinding apparatus according to claim 1, further comprising: the control unit that changes the speed to the second speed lower than the first speed. The detection means is provided with an excessive processing force level, and when the fluctuation of the processing force in the actual processing state of the work by the grindstone is detected to exceed the excessive processing force level, the control means controls the feeding. 3. The double-head grinding apparatus according to claim 1, wherein the means is stopped. The double-head grinding apparatus according to any one of claims 1 to 3, wherein the detection unit detects a change in a thrust force in the actual machining state. 5. The double-head grinding apparatus according to claim 4, wherein the detection unit detects the change in the actual machining state using a fluid pressure on a fluid bearing surface of a grinding spindle. 6. 5. The method according to claim 4, wherein the detecting unit detects a change in the thrust force in the actual machining state by using one element selected from the group consisting of an elastic body, a magnetostrictive element, a piezoelectric element, and a load cell. The double-sided grinding device according to 1. The double-head grinding apparatus according to any one of claims 1 to 3, wherein the detection unit detects a change in a radial force in the actual machining state. The double-head grinding apparatus according to claim 7, wherein an electric signal from a grinding spindle rotating motor is used as the detection means. Grinding stone, feed means for moving the grinding stone at a different speed toward the workpiece,
Detecting means for detecting a change in the output of the vibration sensor in the actual processing state of the work by the grinding wheel,
After the first variation due to the contact state between the grinding wheel and the work is detected by the detection unit, when the actual machining state, which is the second variation, is detected, the moving speed of the feeding unit is set to the first speed. Control means for changing to a second speed lower than the second speed.

Images