JPH0691527A - Grinding device - Google Patents

Abstract

PURPOSE:To prevent poor working beforehand by detecting the contact of a grinding wheel with a work at multiple different positions to detect the abnormality of the work surely. CONSTITUTION:A drive means 100 is controlled by a control means 140 every time a work W is indexed at a contact detection position by an indexing means 130 to make a grinding wheel 20 in contact with the work W, a difference in relative position data detected by a position detection means 120 between a wheel spindle stock and the work W is calculated by a calculation processing means 150 every time a contact detection means 110 detects the contact between the work W and the grinding wheel 20 and, when the difference is within the allowable limit, the work W is judged acceptable and, when it is out of the limit, it is judged defective.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grinding machine used for chamfering a groove of a valve spool, and more particularly to a grinding machine capable of grasping a distance between a workpiece and a grinding wheel by contact detection.

[0002]

2. Description of the Related Art In a grinding machine for chamfering the groove of a valve spool, one method for accurately grasping the distance between the valve spool, which is a workpiece, and the outer circumference of the grinding wheel is AE (Acoustic Emission). A contact detection method using a sensor is known. In this contact detection method, the grinding wheel head is advanced toward the workpiece, the ultrasonic vibration generated when the outer periphery of the grinding wheel contacts the workpiece is detected by the AE sensor, and the wheel head at the time when this detection signal is generated The distance between the outer periphery of the grinding wheel and the workpiece is determined from the position of, and the chamfering of the groove is performed based on this distance. Further, by using such a contact detection method, it is possible to prevent the thermal displacement from affecting the chamfering accuracy of the workpiece, even if the thermal displacement of the grindstone or other parts is caused by the temperature change of the lubricating oil or the like. .

By the way, a shift in the X-axis direction between the workpiece W and the grinding wheel S due to thermal displacement of the grinding wheel head or the like appears as a 7 to 8 times change in the chamfered width after machining (see FIG. 7). The chamfering processing accuracy decreases and processing defects occur. Therefore, in order to prevent the thermal displacement of the grinding wheel head and the like from affecting the processing accuracy, it is necessary to strictly grasp the distance between the workpiece and the outer peripheral surface of the grinding wheel. Further, the positioning accuracy in the X-axis direction (see FIG. 7) between the workpiece and the grinding wheel by the contact detection using the AE sensor is about ± 0.002φ, and high positioning accuracy can be secured.

[0004]

By the way, the conventional AE
When the distance between the workpiece and the outer circumference of the grinding wheel is grasped by the contact detection using the sensor, the outer circumference of the grinding wheel is contacted only once with the predetermined outer circumference of the workpiece. Therefore, as shown in FIG. 8A, when there is a protrusion P such as a burr or a deformation on the contact portion of the workpiece W with which the grinding wheel S contacts, the distance between the workpiece and the grinding wheel is set. I don't know exactly.

That is, in FIG. 8A, the workpiece W is
The center O1 of the workpiece and the center O2 of rotation of the spindle are aligned, and the workpiece W
When the spindle is securely held on the spindle and the tailstock, the grinding wheel S located at a position apart from the rotation center O2 of the spindle by A with the rotation center of the spindle as the origin moves forward to the protrusion P of the workpiece W. When touching, a touch detection signal is generated at this point,
The position of the whetstone base is a1. On the other hand, the diameter of the workpiece W is b1, and the accurate position of the grinding wheel head obtained when contact is detected at a position other than the protrusion P is b1. The position a1 of the whetstone is a value larger than b1.
If the grindstone is controlled to be fed on the basis of 1, the problem that the chamfering of the workpiece is not accurately performed occurs.

Further, when the work is held by the headstock and tailstock, the center of the work is deviated, or the work is not securely held, as shown in FIG. 8 (b). The center O1 of the workpiece W and the center O2 of rotation of the spindle.
There is a gap between them. In this state, the grinding wheel S located at a position apart from the rotation center O2 of the spindle by A advances to move the workpiece W.
When touching, the contact detection signal is generated at this point, so the position of the wheel head is a2. Position a2 of this whetstone
Is a value smaller than b1, and if the grindstone base is feed-controlled based on this a2, the problem that the chamfering of the workpiece is not performed accurately occurs, as in the case of the protrusion. Such a protrusion or the center deviation of the work piece is extremely small, about 3 to 4 μm, and cannot be detected by visual inspection or the like, so that the work piece is chamfered while the wrong distance is grasped, resulting in a defective work piece. There was a problem that occurs.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to detect the abnormality of a workpiece by detecting the contact of the grinding wheel with the workpiece twice or more at different positions. The object of the present invention is to provide a grinding device capable of reliably detecting the occurrence of defects and preventing machining defects.

[0008]

The present invention will be described with reference to FIG. 1, which is a diagram corresponding to claims. The present invention is based on a grinding wheel base 13 having a grinding wheel 20 that is driven to rotate, and the grinding wheel 2 described above.
The workpiece W to be ground by 0 and the grinding wheel 20 come into contact with the grinding wheel 20 and the driving means 100 that relatively moves the grinding wheel base 13 and the workpiece W in the direction in which they approach and separate from each other. Contact detection means 11 for detecting that
0, and position detection means 120 for detecting the relative movement position of the grindstone 13 and the workpiece W by the drive means 100.
An indexing means 130 for rotating the workpiece W to index the contact detection position of the workpiece W with respect to the grinding wheel 20 into a plurality of positions; and the workpiece W and the grinding wheel 20 by the indexing means 130. The drive means 1 each time it is indexed to the contact detection position.
00 for operating the grinding wheel 20 and the workpiece W to contact each other, and the contact detecting means 110 detects the contact between the grinding wheel 20 and the workpiece W at each indexing position. The difference between the relative position data of the grindstone 13 and the workpiece W detected by the position detecting means 120 is calculated, and when the difference is within the allowable value range, the workpiece is regarded as a non-defective product and outside the allowable value range. An arithmetic processing unit 150 for determining a defective work is provided.

[0009]

Each time the workpiece W is indexed by the indexing means 130 to the contact detection position with the grinding wheel 20, the driving means 100 is operated by the control means 140 to bring the grinding wheel 20 and the workpiece W into contact with each other. Then, the contact detection means 110 is the work W.
The position detecting means 12 each time the contact between the wheel and the grinding wheel 20 is detected.
The difference between the relative position data detected at 0 is calculated by the arithmetic processing means 150, and from the calculated difference, the quality of the workpiece W,
Determine the defect. Therefore, the abnormality of the workpiece can be reliably detected, and the machining defect of the workpiece can be eliminated.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 2 is an overall configuration diagram of a grinding apparatus according to the present invention, and FIG. 3 is a plan view showing details of a peripheral portion of a workpiece. In FIG. 2, 10 is a grinder for chamfering the groove of the workpiece W, and 40 is a numerical controller for controlling the grinder 10.

The grinder 10 includes a work table 12 and a bed 1 which are installed on a bed 11 so as to be movable in the Z-axis direction.
A grindstone base 13 is provided on the workpiece 1 so as to be movable in the X-axis direction perpendicular to the workpiece table 12.

The work table 12 is designed to be moved in the Z-axis direction by a servo motor and a feed screw (not shown), and on the work table 12, there is a headstock 15 for bearing a main shaft 14. The tailstocks 16 are located on the left and right and are opposed to each other. As shown in FIG. 2, both ends of the workpiece W are supported by the centers 14a and 16a provided on the spindle 14 and the tailstock 16, respectively, and the left end of the workpiece W is a rotation transmitting member provided on the spindle 14. 17 is engaged so that the workpiece W can be rotated integrally with the spindle 14. Further, the spindle headstock 15 has a spindle 1
A servo motor 18 that rotationally drives 4 is integrally assembled, and an encoder 19 that detects the rotation angle of the spindle 14 from the rotation of the servo motor 18 is attached to the servo motor 18. The detection signal of the encoder 19 is input to the numerical controller 40.

The grindstone base 13 is a grindstone wheel 20 such as a CBN grindstone for chamfering the groove W _a of the workpiece W, and the grindstone wheel 20.
The support member 22 that supports the rotating shaft 21 on which the wheel is mounted, the motor 24 that rotationally drives the grinding wheel 20 via the rotation transmitting mechanism 23 such as the rotating shaft 21 and the belt, and the grinding wheel base 13 are moved in the X-axis direction. It has a servo motor 25. A feed screw 26 is connected to the servo motor 25, and the feed screw 26 is rotated by the servo motor 25 to move the grindstone base 13 in the X-axis direction. Also, the servo motor 2
An encoder 27 that detects the amount of movement of the grindstone 13 from the number of rotations of the servo motor 25 is attached to the unit 5.
The detection signal of the encoder 27 is input to the numerical controller 40.

In FIGS. 2 and 3, 28 is a tailstock 1.
6 is an AE sensor attached to the center support member 16b of No. 6, and the AE sensor 28 has a workpiece W on the outer periphery of the grinding wheel 20.
When the ultrasonic vibration is detected, a signal for contact detection is output, and the contact detection signal is transmitted via the waveform shaping circuit 29 to the numerical controller 40. Entered in.

Reference numeral 30 is a distance sensor for detecting the distance from the reference signal to the outer peripheral surface of the workpiece W and the bottom of the groove. The distance signal detected by this distance sensor 30 is numerically controlled via the AD converter 31. Input to the device 40.

The numerical controller 40 is a central processing unit (hereinafter CPU) that controls and manages the entire grinding machine as shown in FIG.
41), a memory 42 connected to the CPU 41, C
An interface 43 for exchanging data with the outside connected to the PU 41, and pulse generation circuits 44, 45 for transmitting drive pulses in response to a command from the CPU 41 are provided.

An operation panel 46 having a display section 46a, an AD converter 31, and a waveform shaping circuit 29 are connected to the interface 43. A servomotor 18 for the spindle is connected to the pulse generation circuit 44 via a drive circuit 47, and a servomotor 25 for the grinding wheel head is connected to the pulse generation circuit 45 via a drive circuit 48. The memory 42 stores a machining program for chamfering the workpiece W, groove center data, grindstone position data A, B, E with respect to the workpiece W, a contact detection program, and the like.

In FIG. 2, reference numeral 50 is a robot for loading and unloading the workpiece W, and the robot 50 is controlled by a robot controller 51. In addition, the robot controller 51 exchanges signals with the CPU 41. Reference numeral 52 is a conveyer for aligning and transferring an unprocessed work piece and a completed work piece, and 53 is a work storage place for mounting a defective work piece.

In the correspondence between the present embodiment and the claims, the servomotor 25 is the drive means 100, the AE sensor 28 is the contact detection means 110, and the encoder 27 is the position detection means 1.
20, CPU 41, memory 42, pulse generation circuit 44
And the servo motor 18 causes the indexing means 130 to operate on the CPU 4
1, the memory 42 and the pulse generation circuit 45 are control means 1
40, CPU 41 and memory 42 are arithmetic processing means 1
50 are respectively configured.

Next, the operation of this embodiment configured as described above will be described with reference to the flow charts shown in FIGS. When the machining start button on the operation panel 46 is pressed, the numerical controller 40 operates and the robot controller 51
A work load command is given to. When the robot 50 is operated by the robot controller 51 accordingly, the workpiece W transferred by the conveyor 52 is gripped and loaded onto the central axis between the spindle 14 and the tailstock 16, and both centers 1
Both ends of the workpiece W are center-supported by 4a and 16a, and the rotation transmitting member 17 is engaged with the left end portion of the workpiece W to couple the workpiece W to the spindle 14 (step S1).

When the workpiece W is set between the headstock 15 and the tailstock, the process proceeds to step S2, where the CPU 41 gives a pulse rotation command to the pulse generation circuit 44 to generate a pulse signal from the pulse generation circuit 44. By applying this pulse signal to the servo motor 18 through the drive circuit 47, the servo motor 18 is rotated and the main shaft is rotated.

In the next step S3, the rotation speed of the spindle 14 detected by the encoder 19 is fetched by the CPU 41, and the distance signal output from the distance sensor 30 is A.
After being converted into a digital amount by the -D converter 31, it is taken into the CPU 41 through the interface 43 and further stored in a predetermined area of the memory 42. Then, in the next step S4, the CPU 41 determines whether or not the rotation speed of the spindle 14 has reached a preset rotation speed N. Here, when the rotation speed of the spindle 14 has not reached the set value N, the process returns to step S2, and the servo motor 18 is rotated until the rotation speed of the spindle 14 reaches the set value N. This allows
When it is determined that the rotation speed of the spindle 14 has reached the set value N, the process proceeds to step S5, and the spindle 14 is stopped. Then, in the CPU 41, the groove W of the workpiece W shown in step S6
the center of _a calculating on the basis of the distance data stored in the memory 42.

FIG. 6A shows a workpiece W to be chamfered.
And the distance sensor 30 is arranged.
As is apparent from FIG. 6A, when the workpiece W rotates in the arrow direction, the distance sensor 30 outputs a signal having the waveform shown in FIG. 6B according to the outer peripheral surface shape of the workpiece W. It Here, if the values of the rotation angle at the point where the reference value line and the output waveform cross are a and b, the center of each groove can be obtained from (a + b) / 2. The center data of the square groove W _a calculated in this way is stored in a predetermined area of the memory 42 (step S7), and the processing flow shown in FIG. 5 is entered.

FIG. 5 shows a contact detection cycle of the grinding wheel on the workpiece W. First, in step S11, a pulse signal is generated from the pulse generation circuit 45 by giving a grinding wheel head advance command to the pulse generation circuit 45 from the CPU 41, and this pulse signal is applied to the wheel head servo motor 25 through the drive circuit 48. The servomotor 25 is rotated and the feed screw 26 is rotated to move the grindstone base 13 forward. At this time, the grinding wheel 2
0 is rotating at a predetermined rotation speed.

When the outer peripheral surface of the grinding wheel 20 comes into contact with the workpiece W as the grinding wheel base 13 advances, the ultrasonic vibration generated by this contact is detected by the AE sensor 28. This detection signal is waveform-shaped by the waveform shaping circuit 29 and then taken into the CPU 41 through the interface 43 to determine whether or not there is a contact signal (step S12). The position of the workpiece W to the grinding wheel 20 during contact detection contacts are chamfered portion W _b of the groove on both sides shown in Figure 5 (a).

When it is determined that there is a contact signal when the grinding wheel comes into contact with the workpiece, the CPU 41 determines in step S13 that the grinding wheel base 13 for the workpiece W is present.
The advance position A of the
2 is stored in a predetermined area.

In the next step S14, the grindstone base 13 is retracted by a predetermined amount. Then, in the next step S15, the CPU 41 gives a spindle rotation command to the pulse generation circuit 44 to generate a pulse signal corresponding to the command value from the pulse generation circuit 44, and the pulse signal is generated through the drive circuit 47 through the servo motor 18. In addition, the servomotor 18 is rotated to rotate the spindle 14, that is, the workpiece W by 180 degrees.

When the workpiece W is rotated 180 degrees, the process proceeds to step S16, and the grindstone base 13 is advanced again. Then, in the next step S17, it is determined whether or not the contact signal is output from the AE sensor 28 due to the grinding wheel 20 contacting the workpiece W. Here, if there is no contact signal, the process returns to step S16, and the processes of steps S16 and S17 are repeatedly executed until there is a contact signal. And
If it is determined that there is a contact signal, the process proceeds to step S18,
The advance position B of the grindstone 13 with respect to the workpiece W is fetched from the encoder 27 and stored in the memory 42. Then, it progresses to step S19 and the whetstone base 13 is retracted a predetermined amount.

In step S20, the CPU 41 calculates the difference C = AB between the position data A and B of the grindstone 13 stored in the memory 42. And the next step S
At 21, it is determined whether the difference value C is within the range of the allowable value ± D. Here, when it is determined that the difference value C is within the allowable value range, the process proceeds to step S22, and the average value E of the grindstone position data A and B is calculated. The calculated average value E is stored in the memory 42 as a correct contact detection position of the grinding wheel 20 with respect to the workpiece W (step S23),
The process shifts to a normal machining cycle, and the workpiece is chamfered based on the position E of the grindstone.

When it is determined in step S21 that the difference value C is outside the allowable value range, step S24
Then, the robot 50 automatically carries the defective work out of the grinder. That is, it is determined that the workpiece has a protrusion such as a burr as shown in FIG. 8A, or the workpiece W is decentered as shown in FIG. 8B. Note that the chamfering of the workpiece is performed in a known machining cycle, and thus its description is omitted.

In this embodiment as described above, FIG.
As is clear from the flowchart of FIG. 5, the contact detection between the workpiece W and the grinding wheel 20 is performed at two positions facing each other by 180 degrees, and the difference between the position data of the respective grinding wheels detected at these two positions is calculated, When the difference is within the allowable value range, it is judged as a good product, and when it is outside the allowable value range, it is judged as a defective workpiece and it is carried out of the machine, so the distance between the workpiece and the grinding wheel can be accurately grasped. At the same time, it is possible to reliably detect defective workpieces such as burrs and deformations, and prevent defective machining of workpieces.

The present invention is not limited to the configuration shown in the above embodiment, and various modifications can be made without departing from the scope of the claims. For example, the present invention can be applied not only to the chamfering of the groove of the valve spool described in the above embodiment but also to the grinding of other works.

[0033]

As described above, according to the present invention, the contact detection of the grinding wheel with respect to the workpiece is performed at a plurality of different positions, and the difference in the position data of the grinding wheel head at each contact detection point is within the allowable value range. If it is in the allowable value range, the workpiece is judged to be non-defective, and if it is outside the allowable value range, it is judged to be a defective workpiece. Therefore, the abnormality of the workpiece can be surely detected before the workpiece is ground, and the defective machining of the workpiece can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is an overall configuration diagram showing an example of a chamfering grinder to which the contact detection method of the present invention is applied.

FIG. 3 is a plan view showing details of a work surrounding in the present embodiment.

FIG. 4 is a flowchart showing an operation procedure of a phase detection cycle of a workpiece in this embodiment.

FIG. 5 is a flowchart showing an operation procedure of a contact detection cycle in this embodiment.

FIG. 6A is an explanatory diagram showing a positional relationship between a workpiece and a distance sensor, and FIG. 6B is an output waveform diagram from the distance sensor.

FIG. 7 is an explanatory diagram showing a positional relationship between a workpiece and a grinding wheel.

FIG. 8A is an explanatory diagram showing a contact detection state when a burr or the like is present on a workpiece portion where the grinding wheel comes into contact, and FIG. 8B is a diagram showing a center deviation or the like of the workpiece. It is explanatory drawing which shows a contact detection state.

[Explanation of symbols]

 10 Grinder 12 Worktable 13 Grindstone 14 Spindle 15 Spindle 16 Tailstock 18 Servomotor 19 Encoder 20 Grinding wheel 24 Grindstone drive motor 25 Servomotor 27 Encoder 28 AE sensor 30 Distance sensor 40 Numerical controller 41 CPU 42 Memory W Workpiece 100 Drive Means 110 Contact Detection Means 120 Position Detection Means 130 Indexing Means 140 Control Means 150 Arithmetic Processing Means

Claims (1)

[Claims] 1. A grindstone base having a grindstone wheel driven to rotate, and a drive means for relatively moving the grindstone mount and the workpiece in a direction in which a workpiece ground by the grindstone wheel and a grindstone wheel move toward and away from each other. , Contact detection means for detecting that the grinding wheel comes into contact with the workpiece, position detection means for detecting a relative movement position between the grindstone base and the workpiece by the driving means, and rotating the workpiece. Indexing means for indexing the contact detection position of the workpiece with respect to the grinding wheel into a plurality of positions, and operating the drive means each time the indexing means indexes the workpiece contact position with the grinding wheel. Control means for bringing the grinding wheel and the workpiece into contact with each other, and the wheel head detected by the position detecting means each time the contact between the grinding wheel and the workpiece is detected by the contact detecting means at each index position. With the workpiece And a processing unit that determines a workpiece as a non-defective product when the difference is within the allowable value range and determines that the workpiece is defective when the difference is within the allowable value range. And grinding equipment.