JP2020104213A - Grinding method and grinding device - Google Patents

Abstract

To reduce wear volumes by a grinding stone.SOLUTION: During grinding of a work-piece W using a grinding stone 740, an air source 231 and a cylinder 21 are controlled to be switched into a communicated state by control means 9 at prescribed timing, a table 22 is energized from below to be protruded above the cylinder 21 by pressure of air generated by the air source 231, so that a dress grindstone 200 arranged on the table 22 is contacted with the grinding stone 740 overhung from the work-piece W to dress the grinding stone. When the grinding stone 740 is dressed so as to restore grinding capability, the suction source 230 and the cylinder 21 are switched into the communicated state by the control means 9, so that the dress grindstone 200 is separated from the grinding stone 740. When the switching control is performed by the control means 9, the dress grindstone 200 can be contacted with the grinding stone 740 intermittently, only when dressing is needed, which can reduce wear volumes of the grinding stone 740.SELECTED DRAWING: Figure 4

Description

The present invention relates to a grinding method and a grinding device for a workpiece.

When grinding a work piece using a grinding machine, if the work piece is made of a soft resin, etc., the grinding process may cause the resin, etc. to enter the gaps in the grinding wheel and cause the grinding wheel to become clogged. You need to dress with a whetstone. In addition, when the work piece is made of a hard-to-cut material having high hardness, the grinding wheel grinds, and in this case also, it is necessary to dress the grinding wheel. For example, as shown in Patent Document 1, by using a grinding device that can perform dressing of a grinding wheel and grinding of a workpiece in parallel, dressing of the grinding wheel is performed while grinding the workpiece, thereby performing a grinding process. The lower surface of the grinding wheel can be maintained in a shaped state even after the grinding is performed. In the grinding process using this grinding device, the work piece is continuously processed without the trouble of stopping the grinding process and separately dressing the grinding wheel to eliminate the clogging caused by the grinding process. It can be ground.

JP, 2005-020250, A

However, in the parallel execution of the grinding process and the dressing of the grinding wheel mentioned above, the dressing wheel is continuously applied to the grinding wheel during the grinding of the work piece, so that the dressing wheel is dressed more than necessary and the grinding wheel Is exhausted and is uneconomical. The problem to be solved by the present invention is to reduce the amount of wear of a grinding wheel due to dressing.

The present invention relates to a method of grinding a workpiece, which grinds a workpiece using a grinding wheel, including a holding step of holding the workpiece on a chuck table and rotating the workpiece held by the chuck table. A grinding step of contacting a part of the lower surface of an annular grinding wheel to grind a workpiece, and a dressing process is performed on the lower surface of the grinding wheel that overhangs from the workpiece and does not contact the workpiece during the grinding step. And a dressing step of dressing the grinding stone by intermittently contacting the grinding stone.

In the dressing step provided in the above grinding method, when the load current value of the motor for rotating the grinding wheel exceeds a preset first allowable value, a contact step of bringing the dressing wheel into contact with the grinding wheel, A step of separating the dressing grindstone from the grinding grindstone when the load current value falls below a second allowable value which is smaller than the preset first allowable value, the contacting step and the separating step. It is desirable to repeat and.

The grinding whetstone used for grinding by the above grinding method is one in which the grain size of the abrasive grains is #3000 to #4000, and the abrasive grains are bonded by vitrified bond. Is preferably formed by combining abrasive grains with a metal bond or formed by electrodepositing abrasive grains on a base material.

The present invention is a grinding apparatus capable of carrying out the above-described grinding method, wherein a chuck table for holding a workpiece and a ring-shaped grinding wheel are rotatably mounted to grind the workpiece held by the chuck table. Grinding means, a motor for rotating the grinding wheel, a load current value measuring section for measuring a load current value of the motor, the dressing wheel contacting the grinding wheel overhanging from the workpiece and the grinding Dressing means including an elevating mechanism for separating the dressing stone from the grindstone, and control means for controlling the elevating mechanism according to the load current value measured by the load current value measuring unit, and the control means, When the load current value exceeds a preset first allowable value, the dress grindstone is brought into contact with the grinding stone, and the load current value falls below a preset second allowable value which is smaller than the preset first allowable value. This is a grinding device that separates the dress grindstone from the grinding grindstone.

In the present invention, during the grinding process in which a part of the grinding wheel is brought into contact with the workpiece to perform grinding, the dressing wheel is intermittently brought into contact with the lower surface of the grinding wheel that is not in contact with the workpiece, so the grinding wheel The risk of excessive wear due to excessive dressing is reduced.

Also, when the load current value rises due to clogging of the grinding wheel, the dressing wheel is brought into contact with the grinding wheel to eliminate the clogging of the grinding wheel, and the clogging of the grinding wheel is eliminated to reduce the load current value. Since the dressing grindstone is separated from the grinding grindstone when it is lowered, the grinding grindstone can be dressed at an appropriate timing and for an appropriate time. Therefore, the time during which the grinding wheel is in contact with the dressing wheel can be reduced, and the wear amount of the grinding wheel can be reduced.

It is a perspective view showing the whole grinding device. It is a sectional view of a grinding device at the time of starting grinding. It is a sectional view of a grinding device when a grinding whetstone is in contact with a dress whetstone. It is a sectional view of a grinding device when a dress grindstone is separated from a grinding grindstone. It is a graph which shows the load current value which changes with grinding and dressing.

1 Configuration of Grinding Device The grinding device 1 shown in FIG. 1 is a grinding device that grinds the workpiece W held on the chuck table 30 by the grinding means 7. The workpiece W is a substantially disk-shaped work, and the upper surface Wa of the workpiece W has a center Wo. A chuck table 30, a cover 31 surrounding the chuck table 30 from below, and a bellows cover 32 connected to the cover 31 are arranged on the base 10 of the grinding device 1. The chuck table 30 includes a suction unit 300 formed of a porous member and a frame 301 that supports the suction unit 300. A suction source 36 is connected below the chuck table 30, and the workpiece W placed on the holding surface 300 a, which is the upper surface of the suction unit 300, is held by the suction force generated by the suction source 36. The surface 300a is suction-held. Further, the chuck table 30 is supported by a bottomed cylindrical casing 34, and during grinding, is driven by a rotating means 33 arranged inside the casing 34 to rotate around a rotating shaft 35.

The horizontal moving means 4 is provided on the internal base 100 arranged inside the base 10 of the grinding apparatus 1. The horizontal moving means 4 includes a ball screw 40 having a rotation shaft 45 in the Y-axis direction, a pair of guide rails 41 arranged in parallel to the ball screw 40, and a ball screw 40 connected to the ball screw 40 to rotate the ball screw 40 around the rotation shaft 45. It has a motor 42 for moving it, and a movable plate 43 whose inner nut is screwed onto the ball screw 40 and whose bottom is in sliding contact with the guide rail 41. When the motor 42 rotates the ball screw 40 around the rotation shaft 45, the movable plate 43 is guided by the guide rail 41 and relatively moves in the horizontal direction (Y-axis direction), and accordingly, the movable plate 43 has a casing. The chuck table 30 supported via 34 reciprocates in the Y-axis direction together with the cover 31. Further, when the cover 31 moves in the Y-axis direction, the bellows cover 32 expands and contracts.

A column 11 is erected on the rear side (+Y direction side) above the base 10 of the grinding device 1. The grinding means 7 and the grinding means 7 are arranged in the Z-axis direction on the side surface of the column 11 on the −Y direction side. A grinding feed means 5 for moving up and down is provided. The grinding means 7 is connected to a rotary shaft 70 having an axis 75 in the Z-axis direction, a housing 71 that rotatably supports the rotary shaft 70, a motor 72 that rotationally drives the rotary shaft 70, and a lower end of the rotary shaft 70. And a grinding wheel 74 detachably connected to the lower surface of the mount 73. The grinding wheel 74 includes a base 741 and a plurality of substantially rectangular parallelepiped grinding wheels 740 arranged in a ring shape on the lower surface 741 a of the base 741. The grinding stone 740 is formed by fixing abrasive grains with a binder or the like, and its lower surface 740a is a grinding surface for grinding the workpiece W.

The grain size of the abrasive grains used for the grinding wheel 740 is set according to the material of the workpiece W. For example, when the workpiece W is made of epoxy resin, the grain size is preferably #3000 to #4000, and the binder in this case is preferably vitrified bond.

The grinding feed means 5 includes a ball screw 50 having an axis in the Z-axis direction, a pair of guide rails 51 arranged parallel to the ball screw 50, a motor 52 connected to the upper end of the ball screw 50 to rotate the ball screw 50. The motor 52 is provided with a lifting plate 53 whose inner nut is screwed into the ball screw 50 and whose side portion is in sliding contact with the guide rail 51, and a holder 54 which is connected to the lifting plate 53 and holds the grinding means 7. When the is rotated, the elevating plate 53 is guided by the guide rails 51 and moves up and down in the Z-axis direction, and the grinding means 3 held by the holder 54 moves in the Z-axis direction perpendicular to the holding surface 300a. It is configured to be ground and fed.

The grinding device 1 is provided with a control means 9 for controlling each part of the grinding device 1 by an electric signal, and the control means 9 is provided with a load current value measuring part 90. The load current value measuring unit 90 includes an ammeter (not shown) that measures the value of the load current applied to the motor 72 and is connected to the motor 72. Further, the load current value measuring unit 90 can store a first allowable value that is an upper limit value and a second allowable value that is a lower limit value of the load current value. The second allowable value, which is the lower limit allowable value, is smaller than the first allowable value, which is the upper limit allowable value of the load current value.

The dressing means 2 is arranged on the cover 31 adjacent to the chuck table 30. The dressing means 2 is provided with a table 22 and a cylinder 21 for accommodating the table 22, and on the table 22, a base material 201 to which a dress grindstone 200 is fixed is detachably arranged. ..

The grain size of the abrasive grains forming the dress grindstone 20 is set according to the material of the workpiece W. For example, when the workpiece W is made of an epoxy resin, the abrasive grains having a grain size of about #2000 are bonded by a metal bond, or the grain size is similar. The abrasive grains are preferably formed by electrodeposition.

An elevating mechanism 23 for moving the table 22 up and down is disposed below the table 22, and the elevating mechanism 23 includes a suction source 230, an air source 231, and a valve 232. The suction source 230 and the air source 231 are connected to the cylinder 21 via a valve 232, and a signal is sent by the control means 9 to control the valve 232, whereby the suction source 230 and the air source 231 are moved to the cylinder 21. Is communicated alternatively. When the suction source 230 is in communication with the cylinder 21, the gas inside the cylinder 21 is sucked by the suction force generated by the suction source 230, so that the table 22 can be sucked from below and housed in the cylinder 21. .. Further, when the air source 231 is in communication with the cylinder 21, by supplying air from the air source 231 to the inside of the cylinder 21, the table 22 accommodated in the cylinder 21 is urged from below and above the cylinder 21. Can be projected.

2 Operation of Grinding Device The operation of the grinding device 1 when performing grinding using the grinding device 1 having the above-described configuration and dressing the grinding wheel 740 using the dressing wheel 20 will be described. The workpiece W is assumed to be made of epoxy resin.

(Holding process)
The workpiece W is placed on the holding surface 300a of the chuck table 30 of the grinding apparatus 1 shown in FIG. 1 and suction-held by the suction force exerted by the suction source 36.

Then, the ball screw 40 is rotated around the rotation shaft 45 by the driving force of the motor 42, and the movable plate 43 is moved in the Y-axis direction along the guide rail 41, thereby supporting the movable plate 43 via the casing 34. The chuck table 30 being moved is moved in the Y-axis direction. As a result, the chuck table 30 and the dressing means 2 move below the grinding wheel 740, the workpiece W held by the chuck table 30 and the grinding wheel 740 are aligned in the Y-axis direction, and the dressing means 2 is moved. Positioning with the grinding wheel 740 in the Y-axis direction is performed.

As shown in FIG. 2, when the alignment is completed, the center Wo of the circle of the upper surface Wa of the workpiece W is positioned below the lower surface 740a of the grinding wheel 740, and the grinding wheel 740 is fed by grinding. When the grinding stone 740 and the workpiece W come into contact with each other, the workpiece W is positioned so that the rotation trajectory of the grinding stone 740 passes through the rotation center Wo of the workpiece W. At this time, a part of the plurality of grinding wheels 740 is located in the area A above the workpiece W, and the other grinding wheels 740 are located in the area B on the table 22 side that is not above the workpiece W. ing. That is, the region B on the table 22 side of the grinding wheel 740 that overhangs from the workpiece W is in a state of protruding relatively to the right (+X direction side) from the workpiece W, and the dressing means 2 The grinding wheel 740 is positioned below the overhung area B.

(Grinding process)
As the rotary shaft 70 is driven by the motor 72 and rotates about the axis 75 in the Z-axis direction, the grinding wheel 740 of the grinding wheel 74 connected to the rotary shaft 70 via the mount 73 has the same axis. Rotate around 75. In the holding step, some of the plurality of grinding wheels 740 are located in the area A above the work W, and the other grinding wheels 740 are located in the area B on the table 22 side that is not above the work W. Therefore, the plurality of grinding wheels 740 rotate while alternately passing through the regions A and B. Further, the chuck table 30 is driven by the rotating means 33 to rotate around the rotary shaft 35, and accordingly, the workpiece W held on the chuck table 30 rotates around the rotary shaft 35. In this state, the ball screw 50 is rotationally driven by the motor 52 of the grinding feed means 5, and the lifting plate 53 is lowered along the guide rail 51 in the −Z direction at a predetermined speed. As the lifting plate 53 descends, the holder 55 supported by the lifting plate 53 descends, and as shown in FIG. 3, the grinding wheel 740 rotates and contacts the workpiece W suction-held on the chuck table 30. Contact. Further, a part of the lower surface 740a of the ring-shaped grinding wheel 740 which rotates by continuously lowering the grinding wheel 740 that rotates in the −Z direction at a predetermined grinding feed speed is held on the chuck table 30 so that the rotating workpiece W is held. The workpiece W is ground by being brought into contact with the upper surface Wa.

At this time, with respect to the dressing means 2, the gas inside the cylinder 21 is sucked by the suction force exerted by the suction source 230, so that the table 22 is sucked from below and is housed in the cylinder 21. The upper surface 200a of the dressing grindstone 200 arranged on the table 22 is separated from the lower surface 740a of the grinding grindstone 740.

(Dressing process)
For example, after a lapse of a predetermined time from the start of grinding, a control signal is sent from the control means 9 to the valve 232 in order to dress the grinding wheel 740 for the purpose of eliminating clogging of the grinding wheel 740 that has occurred during grinding. .. When a control signal is sent from the control means 9 to the valve 232, the valve 232 is switched and controlled, and the state in which the suction source 230 and the cylinder 21 are in communication is switched to the state in which the air source 231 and the cylinder 21 are in communication. When the air source 231 and the cylinder 21 are communicated with each other, as shown in FIG. 4, the pressure of the air supplied from the air source 231 to the cylinder 21 urges the table 22 from below to move it above the cylinder 21. Project. When the table 22 projects above the cylinder 21, the dress grindstone 200 arranged on the table 22 comes into contact with the region B of the overhanging grinding grindstone 740 and grinds in parallel with the grinding of the workpiece W. The dressing of the grindstone 740 is performed.

Further, a control signal is sent from the control means 9 to the valve 232 at a timing when the grinding wheel 740 is dressed and the grinding ability of the grinding wheel 740 is considered to be sufficiently recovered, for example, after a predetermined time has elapsed from the start of dressing. The valve 232 is switched and controlled by the control signal sent from the control means 9, and the state in which the air source 231 and the cylinder 21 are in communication is switched to the state in which the suction source 230 and the cylinder 21 are in communication as shown in FIG. Then, the table 22 is sucked from below the cylinder 21 again by the suction force exerted by the suction source 230, descends in the −Z direction, and is housed in the cylinder 21. When the table 22 is lowered, the dressing grindstone 200 is separated from the grinding grindstone 740, and the grinding grindstone 740 is no longer dressed.

In this way, a control signal is sent from the control means 9 to the valve 232 at predetermined time intervals, and the suction source 230 and the cylinder 21 are in communication with each other (FIG. 3). The state (FIG. 4) in which the air source 231 and the cylinder 21 are in communication is alternately switched. As a result, the grinding wheel 740 can be intermittently dressed while the workpiece W is ground by the grinding wheel 740. It should be noted that the timing of sending the control signal from the control means 9 to the valve 232 is empirically determined such that the grinding ability of the grinding wheel 740 may be deteriorated due to clogging of the grinding wheel 740 caused by grinding, or the dressing of the grinding wheel 740 due to dressing. It is a timing at which the self-generated blade of the lower surface 740a is promoted and the grinding ability of the grinding wheel 740 becomes equal to that at the start of grinding. Further, the timing of starting the dress and the timing of ending the dress may be controlled according to the actual clogging situation and the like, as described below. In this case, the dressing process includes a contact process and a separation process described below.

(Contact process)
In the dressing process, the load current value measuring unit 90 connected to the motor 72 measures the value of the load current applied to the motor 72, and the load current value is the upper limit value stored in the load current value measuring unit 90. When the allowable value of 1 is exceeded, the control unit 9 controls the switching of the valve 232 to start dressing.

During the grinding of the workpiece W by the grinding wheel 740, grinding debris generated by grinding adheres to the lower surface 740a of the grinding wheel 740 and causes clogging, so that the load applied to the grinding wheel 740 is larger than that before grinding. Become. When the grinding wheel 740 rotates, electric power is continuously supplied to the motor 72 from a power source (not shown), and the motor 72 rotates the rotating shaft 70 at a constant rotation speed even when the load applied to the grinding wheel 740 becomes large. It is feedback controlled. Therefore, when grinding dust adheres to the lower surface 740a of the grinding wheel 740 due to grinding and the load applied to the grinding wheel 740 increases, the load current value applied to the motor 72 increases.

Therefore, a first allowable value is stored in advance in the load current value measuring unit 90 as an upper limit value of the load current value applied to the motor 72, and the load current value measuring unit 90 stores the load current value applied to the motor 72 during grinding. taking measurement. When the value of the load current measured by the load current value measuring unit 90 exceeds the first allowable value, a control signal is sent from the control means 9 to the valve 232 to perform switching control, and the suction source 230 and the cylinder 21 are connected. Is communicated with the air source 231 and the cylinder 21 is communicated with the cylinder 21 (FIG. 4).

When the air source 231 and the cylinder 21 are communicated with each other, the table 22 is urged by the pressure of the air supplied from the air source 231, and the dress grindstone 200 is overhung from the workpiece W in the region B of the grinding grindstone 740. And the grinding wheel 740 is dressed.

When the grinding wheel 740 is dressed, the lower surface of the grinding wheel 740 is scraped by the dressing wheel 200, and when the clogging or the like that has occurred on the lower surface 740a of the grinding wheel 740 is eliminated, the load applied to the grinding wheel 740 gradually. The load current value applied to the motor 72 that is reduced and feedback-controlled decreases.

(Separation process)
The load current measuring unit 90 stores a second allowable value, which is the lower limit value of the load current value, in advance. When the load current value applied to the motor 72 decreases and falls below the second allowable value, the control means is controlled. 9 sends a control signal to the valve 232 to control the switching of the valve 232, so that the suction source 230 and the cylinder 21 communicate with each other (from the state where the air source 231 and the cylinder 21 communicate with each other (FIG. 4 )). 3). Since the suction source 230 and the cylinder 21 are communicated with each other, the suction force exerted by the suction source 230 again causes the table 22 to be housed in the cylinder 21 by being sucked and lowered, and the upper surface of the dress grindstone 200. 200a is separated from the lower surface 740a of the grinding wheel 740 and dressing is stopped.

Based on the comparison between the first and second allowable values stored in the load current value measuring unit 90 and the load current value applied to the motor 72 measured by the load current value measuring unit 90, the control means 9 By performing the switching control of the valve 232, the contact process and the separation process described above are repeatedly performed, and as shown in FIG. 5, the load current value applied to the motor 72 is increased or decreased. Since the grinding wheel 740 can be dressed intermittently according to the load current value measured by the load current value measuring unit 90, the time during which the upper surface 200a of the dressing wheel 200 contacts the lower surface 740a of the grinding wheel 740 is shortened. Therefore, it is possible to reduce the wear amount of the grinding wheel 740 due to the dress.

Even when the work piece is a difficult-to-cut material, the same control method can be used.

1: Grinding device 10: Base 100: Internal base 2: Dressing means 200: Dressing grindstone 200a: Dressing grindstone upper surface 201: Base material 21: Cylinder 22: Table 23: Lifting mechanism 230: Suction source 231: Air source 232: Valve 30: Chuck table 300: Suction part 300a: Holding surface 301: Frame 31: Cover 32: Bellows cover 33: Rotating means 34: Casing 35: Rotating shaft 36: Suction source 4: Horizontal moving means 40: Ball screw 41: Guide rail 42: motor 43: movable plate 45: rotary shaft 5: grinding feed means 50: ball screw 51: guide rail 52: motor 53: lift plate 55: holder 7: grinding means 70: rotary shaft 71: housing 72: motor 73: mount 74: Grinding wheel 740: Grinding grindstone 740a: Lower surface of the grinding grindstone 741: Base 75: Rotating shaft 9: Control means 90: Load current value measurement unit W: Workpiece Wa: Workpiece upper surface Wo: Workpiece Center of the upper surface of the grinding wheel A: Outer peripheral edge of the grinding wheel B: Overhung area of the grinding wheel

Claims (4)

A method of grinding a workpiece by grinding a workpiece using a grinding wheel,
A holding step for holding the workpiece on the chuck table,
A grinding step of grinding a workpiece by bringing a part of the lower surface of a rotating grinding wheel into contact with the workpiece held by the chuck table;
A dressing step of dressing the grinding grindstone by intermittently contacting the dressing grindstone with the lower surface of the grinding grindstone overhanging from the work piece and not in contact with the work piece during the grinding step .. The dressing process is
A contact step of bringing the dressing wheel into contact with the grinding wheel when the load current value of the motor for rotating the grinding wheel exceeds a preset first allowable value;
A separation step of separating the dress grindstone from the grinding grindstone when the load current value falls below a second permissible value that is smaller than the first permissible value set in advance,
The grinding method according to claim 1, wherein the contacting step and the separating step are repeated. The grinding wheel has a grain size of #3000 to #4000, and is formed by binding the grain by vitrified bond,
2. The grinding method according to claim 1, wherein the dress grindstone is formed by combining abrasive grains with a metal bond or is formed by electrodepositing abrasive grains on a base material. A grinding apparatus capable of carrying out the grinding method according to claim 1 or 2, comprising:
A chuck table that holds the workpiece,
A grinding means for rotatably mounting an annular grinding wheel and grinding the workpiece held by the chuck table;
A motor for rotating the grinding wheel,
A load current value measuring unit for measuring a load current value of the motor,
Dressing means provided with an elevating mechanism for contacting the dressing grindstone with the grinding grindstone overhanging from the workpiece and separating the dress grindstone from the grinding grindstone,
Control means for controlling the elevating mechanism according to the load current value measured by the load current value measuring section,
The control means is
When the load current value exceeds a preset first allowable value, the dress grindstone is brought into contact with the grinding grindstone,
A grinding device that separates the dressing grindstone from the grinding grindstone when the load current value falls below a second allowable value that is smaller than the preset first allowable value.

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