JPH068112A - Noncontact tracer control method - Google Patents

Abstract

PURPOSE:To prevent loss of measurement of a distance produced when feed is moved from clamp tracer to model copying. CONSTITUTION:A distance L between optical distance sensors 5a and 5b and a model 6 is measured while the optical distance sensors 5a and 5b are moved relatively at a clamp copying speed along a clamp limit LCZ set vertically on a table placed on the model 6. When the measured value L becomes smaller than a preset comparison value L0, it is considered that the optical distance sensors 5a and 5b nears a switchover point P4 between clamp copying and model copying. Then a relative feed rate of the optical distance sensors 5a and 5b is reduced to prevent a relative follow-up delay of a tracer head and also prevent loss of measurement of a distance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a non-contact copying control method.

[0002]

2. Description of the Related Art As a method of copying control using a model,
The stylus slides directly onto the model by horizontally feeding it to the table on which the model is placed, and the contact-type scanning control detects the shape of the model by the vertical movement of the stylus. A non-contact copying control is known in which the distance between the two is measured and the feeding control of each axis of the machine tool is controlled so that the measured value becomes a constant value, thereby performing the copying control. In addition, in this type of copying control, a so-called clamp that sets a clamp limit in the direction perpendicular to the table on which the model is placed and feeds the table in the horizontal direction while the actual copying control is suspended. In some cases, the copying control is started after the stylus or non-contact sensor is brought close to the model by copying. However, in the case of contact-type copying control in which the shape of the model is detected by the vertical movement of the stylus, the stylus does not come into contact with the model while performing clamp copying, so the switching point at which the transition from clamp scanning to model scanning is performed beforehand. It was not possible to predict and reduce the table feed rate, and as a result, the stylus collided with the model during the transition from clamp copying to model copying, and the table was fed as it was, so the stylus Vertical movement of the table may not follow the feed of the table, which may cause overshoot in measurement, so-called bite.In addition, when the vertical movement of the stylus is detected when the vertical movement of the stylus is detected after shifting from clamp scanning to model scanning. The mechanical impact is likely to be large because the feed in the direction perpendicular to the There was.

[0003]

Further, as a non-contact scanning control method for accurately performing distance measurement, the applicant of the present invention has proposed that two sets of optical system are provided in a tracer head rotatably arranged with respect to a vertical axis. The distance sensor is arranged at a fixed angle, and the normal vector of the model surface is obtained by sampling processing by this optical distance sensor so that the optical axis of the optical distance sensor is substantially coincident with the normal vector of the model surface. A non-contact copying control device that controls the rotation angle of a tracer head to a position to perform distance measurement while always maintaining a fixed positional relationship between an optical distance sensor and a model surface. 194500, Japanese Patent Application No. 1-32877
It has already been proposed as No. 7 and Japanese Patent Application No. 3-208814. However, in these cases, it is necessary to strictly detect the rotation angle of the tracer head, the current position of each axis of the table, etc. to obtain the normal vector, and the table moves at a high speed as in the case of clamp scanning, If the distance between the optical distance sensor and the model surface changes drastically due to a step on the surface, etc., the rotation angle of the tracer head and each axis of the table obtained in the previous and current sampling processing due to the operation delay of the tracer head, etc. There is a case where the data such as the current position of is inconsistent. In addition, since the measurement control is switched at the time of transition from the clamp copying to the model copying, as with the contact-type copying control described above, it is often the case that the tracer head follows a delay or the data in the sampling process is inconsistent. This may cause a bite in measurement. Therefore, an object of the present invention is to eliminate these drawbacks of the prior art, prevent the measurement from penetrating even in the case of transition from the clamp copying to the model copying, and to prevent an accidental impact on the machine tool mechanism. Another object of the present invention is to provide a non-contact copying control method that does not cause

[0004]

A non-contact copying control method according to the present invention measures a distance between a sensor and a model by a non-contact sensor, and each machine tool is controlled so that the measured value becomes a constant value. In the non-contact copying control method in which the axis feed is drive-controlled to perform the copying control, the non-contact sensor is clamped along a clamp limit set in a direction perpendicular to the table on which the model is mounted. When the measurement is performed by relatively moving at the scanning speed, the clamp scanning speed is decelerated when the measurement value becomes smaller than a preset comparison value, and when the sensor measurement value becomes the constant value, the scanning speed is changed. The above object was achieved by performing the copying control.

[0005]

The non-contact sensor is relatively moved at the clamp scanning speed along the clamp limit set in the direction perpendicular to the table on which the model is placed, and the distance between the sensor and the model is measured. . When the non-contact sensor approaches the model and the measured distance value becomes smaller than the preset comparison value, the clamp scanning speed is decelerated to prevent the relative measurement operation of the non-contact sensor from being delayed. Suppress bite. Further, when the distance between the non-contact sensor and the model becomes a constant value and the start of copying for the model is confirmed, control is performed at the normal copying speed.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram schematically showing a configuration of a non-contact copying control device 1 of an embodiment to which a non-contact copying control method of the present invention is applied and a machine tool 3 which is drive-controlled by the control device 1. The machine tool 3 is roughly composed of a machining head unit 3
6 and a work rest part 37. The machining head part 36 includes a spindle motor (not shown) for driving a tool 34 such as an end mill, and the machining head part 36 as a whole relative to the work rest part 37. A moving Z-axis servo motor 32z is provided. A table 31 for placing the work 35 and the model 6 is provided on the work placing portion 37, and the table 31 is moved in the direction of each axis by the X-axis servo motor 32x and the Y-axis servo motor 32y. To be done. Further, a tracer head 4 forming a part of a non-contact sensor is provided on the lower surface of the processing head portion 36 along a vertical axis passing through the table 31, and an optical axis of irradiation light is provided at the tip of the tracer head 4. As a reference, each of the optical distance sensors 5a and 5b is fixed in parallel with the tracer head 4 at a constant angle. Each of the optical distance sensors 5a and 5b keeps a constant angle with the tracer head 4 around the C axis that constitutes the central axis of the tracer head 4 by driving the C axis servo motor 32c that rotationally drives the tracer head 4. Rotate integrally. The C axis is a vertical axis that passes through the table 31, is parallel to the Z axis, and moves up and down integrally with the processing head unit 36. The optical distance sensors 5a and 5b are ordinary optical distance sensors composed of an irradiation means such as a semiconductor laser or a light emitting diode and a light receiving element such as a CCD. The optical distance sensors 5a and 5b provide position data and irradiation angle of reflected light on the light receiving element. Based on this, the distance L from the tip of the tracer head 4 to the light receiving position on the model 6 is obtained.

Further, the non-contact copying control apparatus 1 has a microprocessor 11 as a control means, and the microprocessor 11 has various kinds of driving control of the machine tool 3 and tracing control by the tracer head 4. A ROM 12 storing a system program, a RAM 13 for temporarily storing data such as distance measurement values La ′ and Lb ′ from the optical distance sensors 5a and 5b, and various parameters and setting data such as a scanning direction and a table moving speed. A non-volatile memory 14 for storing data and an interface 1 to which an operation panel 2 as data input means is attached
5 and the like are connected via a bus 10.

In the relationship between the non-contact copying control device 1 and the machine tool 3, servomotors 32x, 32y, 32 for the respective axes are provided.
Each z is a D / A converter 17x, 17y, 17 for each axis.
The pulse coders 33x, 33y, 33z provided on the respective axes are rotationally driven by the servo amplifiers 18x, 18y, 18z of the respective axes by the speed commands Vx, Vy, Vz of the respective axes input from the microprocessor 11 via z. Feedback pulses FPx, FPy, FPz for each predetermined rotation of each axis
To output the current position registers 19x, 19y, 1 for each axis
Input to 9z, current position registers 19x, 19 for each axis
For y and 19z, feedback pulses FPx, FPy and FPz are cumulatively added or subtracted according to the rotation direction of each axis to store current position data Xa, Ya and Za of each axis, and these values are processed by a microprocessor. 11 is input. In addition, the optical distance sensors 5a and 5
b is a control circuit 21a, 21 for every predetermined sampling period.
Distance measurement is performed by a measurement command input from the microprocessor 11 via b, and each distance measurement value La '
And Lb 'are input to the microprocessor 11 via the A / D converters 16a and 16b, and the microprocessor 11 inputs the current position registers 19x and 19y for each axis every time the measurement results La' and Lb 'are input. , 19z
And the current rotation position of the tracer head 4, that is, the value of the current position register provided corresponding to the C-axis servomotor 32c, has a one-to-one correspondence with at least the latest two.
The sampling results of the batch are cyclically stored in the RAM 13.

In the case of normal copying control according to the model 6,
The microprocessor 11 outputs speed commands Vx and Vy for each axis relating to the table 31 based on the scanning direction and the scanning speed set in the non-volatile memory 14, and the D / A converters 17x and 17y for each axis and the servo amplifier 18x. , 18y to drive and control the servo motors 32x, 32y for the respective axes to feed the table 31 in the XY plane. At the same time, the microprocessor 11 causes the optical distance sensors 5a and 5
The distance measurement values La ′ and Lb ′ by b are detected every predetermined sampling period to obtain the distance L from the tip of the tracer head 4 to the light receiving position on the model 6, and set between the model 6 and the tracer head 4. The difference between the determined constant value A (hereinafter referred to as clearance) and the distance measurement value L of the optical distance sensor based on the sampling result of this time is obtained, and this value is converted into the distance in the Z-axis direction to calculate the position deviation related to the clearance. At the same time as calculating, the speed command Vz to the Z-axis servomotor 32z is output based on this position deviation, and D /
The Z-axis servomotor 32z is driven and controlled via the A converter 17z and the servo amplifier 18z, and the machining head 36 is moved up and down relatively with respect to the table 37 to move the distance L between the surface of the model 6 and the tracer head 4. Is always set to a constant value A, and the work 34 is cut into the same shape as the model 6 by the tool 34.

At this time, the microprocessor 11 causes the sampling data for the previous time and the current time stored in the RAM 13, ie, the distance measurement values La 'and Lb' of the optical distance sensors 5a and 5b, to be stored at every predetermined sampling period.
And the values of the current position registers 19x, 19y, and 19z of each axis, the current rotation position of the tracer head 4, the offset data between the optical distance sensors 5a and 5b, and the like, and read the optical type at the time of the previous sampling and the current sampling. The coordinate data of the light receiving position on the model 6 by the distance sensors 5a and 5b is calculated, the normal vector of the current light receiving position on the surface of the model 6 is calculated based on the coordinate data of these light receiving positions, and the normal vector is stored in a table. 31 X
-A rotation command sc for rotating the tray facer head 4 to a position projected on the Y plane is output, and the C-axis servomotor 32c is output via the D / A converter 17c and the servo amplifier 18c.
To drive. Then, the tray hair head 4 is driven to the projection position of the normal vector, and the optical distance sensor 5a,
The tracer is moved so that the optical axis of the irradiation light of 5b approximates the normal vector, and the optical axis of the irradiation light of the optical distance sensors 5a and 5b always substantially coincides with the normal vector of the surface of the model 6. The rotation position of the head 4 is controlled and the model 6
By keeping the clearance L between the surface of the tracer head 4 and the tracer head 4 at a constant value A at all times, the light receiving position on the model 6 by the irradiation light can be changed to the optical distance sensor 5a, It should be within the range detectable by the light receiving element 5b. However, when performing clamp scanning, the Z-axis position is fixed and the table 31 is fixed.
In the meantime, since the process related to the distance measurement is not executed during this time, the tracer head 4 is rotated to the optimum position when the distance measurement is started from the clamp copying to the model copying. In the case of contact-type copying control using a stylus, there is a delay in calculating the coordinate data of the light receiving position based on the current rotation position of the tracer head 4 and the offset data between the optical distance sensors 5a and 5b. Similar to the above, there was a case where the distance measurement cuts into the distance measurement at the switching point where the clamp copying shifts to the model scanning.

FIG. 2 is a flow chart showing the outline of the scanning control applied by the present embodiment in order to solve such a problem. Hereinafter, referring to the principle of operation shown in FIG. 3 and the flow chart of FIG. The processing operation of the non-contact copying control device 1 in this embodiment will be described.

First, when the model 6 is placed on the table 31, the clamp limit LCZ is set with respect to the Z axis perpendicular to the table 31, and the machining start key is operated, the microprocessor 11 causes the tip of the tracer head 4 to move. In accordance with the trace starting point LCZ + A of the clamp limit LCZ, the table 31 is fed in the XY plane at the clamp scanning speed according to the control program of the ROM 12 to start the clamp scanning control of the machine tool 3, as shown in FIG. Such processing is repeatedly executed every predetermined period.

The microprocessor 11, which fixed the Z axis and started the scanning control, firstly, the optical distance sensors 5a and 5a.
Whether the distance measurement by b is possible, that is, the light receiving position on the model 6 by the irradiation light is the optical distance sensor 5
It is determined whether or not it is within the detectable range of the light receiving elements a and 5b (step S1), but at a stage immediately after starting the clamp scanning control, for example, the optical distance sensor 5a,
In the state where 5b is located at the point P1 in FIG. 3,
Since the optical distance sensors 5a and 5b and the surface of the model 6 are widely separated from each other and the distance measurement by the optical distance sensors 5a and 5b is impossible, the microprocessor 11
Continues the clamp scanning control of the machine tool 3 by feeding the table 31 in the XY plane at the clamp scanning speed as it is (step S10). Thereafter, the microprocessor 11 keeps the Z axis fixed until the optical distance sensors 5a and 5b and the surface of the model 6 come close to each other by the feeding of the table 31 and the distance measurement by the optical distance sensors 5a and 5b becomes possible. The processing of step S1 and step S10 is repeatedly executed to feed the table 31 in the XY plane at the clamp scanning speed.

Then, the optical distance sensors 5a and 5b are set to X.
-By the feeding in the Y plane, the surface of the model 6 is approached to some extent and the distance measurement by the optical distance sensors 5a and 5b becomes possible, and when the distance measurement by the above-described sampling processing is started, the processing of step S1 and step S10 is performed. The microprocessor 11 that repeatedly executes the steps of the optical distance sensors 5a and 5b after the determination process of step S1 is completed.
It is determined whether or not the current position of the Z-axis indicating the position of is larger than LCZ + A, that is, whether or not the copying control for the model 6 is started and the Z-axis is moving upward (step S2). Immediately after the distance can be measured by the linear distance sensors 5a and 5b, for example, when the optical distance sensors 5a and 5b are at point P2 in FIG. 3, the tip of the tracer head 4 is set to the trace start point. LCZ
Table 31 at clamp scanning speed according to the height of + A
Since the process of applying the feed in the XY plane is continuously performed, the current position of the Z axis becomes equal to LCZ + A, and the determination result of step S2 becomes false.

Therefore, the microprocessor 11 further determines whether or not the flag F for storing the fact that the copying control for the model 6 is being executed is set (step S).
3) At this stage, since the flag F is not set, the microprocessor 11 determines whether the model 6 is to be used based on the distance measurement result L by the optical distance sensors 5a and 5b, the clamp limit LCZ, and the clearance A. It is determined whether or not the light receiving position of is located below the clamp limit LCZ (step S5). In this state, the light receiving position on the model 6 is located below the clamp limit LCZ (see point P2 in FIG. 3). Then, the microprocessor 11 moves from the tip of the tracer head 4 to the light receiving position on the model 6. Whether or not the distance L is smaller than a preset comparison value L0, that is, the height of the surface of the model 6 at this point is the clamp limit LC.
It is considerably close to Z, and it is determined whether or not the switching point P4 from the clamp copying to the model copying is approaching (step S7).

If the distance L from the tip of the tracer head 4 to the light receiving position on the model 6 is larger than a preset comparison value L0, and there is still a sufficient margin before shifting from the clamp copying to the model copying, the micro Processor 11
As it is, the Z axis is fixed and the table 31 is fed at the clamp scanning speed in the XY plane to continue the clamp scanning control of the machine tool 3 (step S10). Until it becomes smaller than the preset comparison value L0, the processes of steps S1 to S3 and steps S5, S7, and S10 are repeatedly executed in the same manner as described above.

In this way, the distance L from the tip of the tracer head 4 to the light receiving position on the model 6 is preset while the table 31 is being fed in the XY plane at the clamp scanning speed. When it becomes smaller than L0 and the switching point P4 from the clamp scanning to the model scanning approaches the approaching point, it is detected by the determination process of step S7 (see point P3 in FIG. 3), the microprocessor 11 Speed commands Vx, V to servo amplifiers 18x, 18y
y is changed to reduce the clamp scanning speed (step S
9), the feed rate of the table 31 and the surface shape change of the model 6, that is, the relative follow-up delay of the tracer head 4 with respect to the change of the slope and height of the model 6 are prevented and the latest two sampling results are obtained. The accuracy of distance measurement based on the above is improved to prevent the occurrence of measurement error and the penetration of measurement.
Until it is detected in the determination process of step S5 that it is projected above CZ, the same process as described above is performed in step S5.
1 to step S3 and step S5, step S7,
The process of step S9 is repeatedly executed to feed the table 31 with the Z-axis fixed and perform the clamp copying.

When the clamp scanning speed is reduced and the clamp scanning is executed, the determination result of step S5 becomes true and it is detected that the surface of the model 6 is projected above the clamp limit LCZ ( 3 (see P4 in FIG. 3), the microprocessor 11 sets a flag F for storing the fact that the copying control for the model 6 is being executed, and the copying control for the model 6, that is, the clearance L between the surface of the model 6 and the tracer head 4 is set. Is started at a constant value A (step S6), the speed commands Vx and Vy to the servo amplifiers 18x and 18y for the respective axes are changed again to set the feed speed of the table 31 to the normal value. The scanning speed is reset (step S8). As a result of starting the Z-axis drive control for keeping the clearance L between the surface of the model 6 and the tracer head 4 at a constant value A at all times, the value of the current position of the Z-axis indicating the positions of the optical distance sensors 5a and 5b becomes LCZ
The value becomes larger than + A, and thereafter, the processes of step S1, step S2, and step S8 are repeatedly executed, and during this period, the copying control for the model 6 is performed. When the shape data of the model 6 is digitized and collected by copying the model 6, the current position of the Z axis and the value of the clearance L and the current value register values of the X and Y axes. Based on, the light receiving position on the model 6, that is, the surface shape of the model 6 is sequentially calculated, and this value is sequentially stored in the RAM 13.

While the clearance L between the surface of the model 6 and the tracer head 4 is always kept at a constant value A, the servomotors 32x, 32y, 32z of the respective axes are drive-controlled and the optical distance is applied while the table 31 is fed. When the sensors 5a and 5b reach the crossing position between the model 6 and the clamp limit LCZ and the substantial copying of the model 6 is completed, the surface of the model 6 is again positioned below the clamp limit LCZ (see FIG. 3). (See the point P5 in FIG. 3), the microprocessor 11 that repeatedly executes the processes of steps S1, S2, and S8 detects the end of scanning for the model 6 in the determination process of step S2. Next, the microprocessor 11 determines whether or not the flag F storing the execution of the copying control for the model 6 is set (step S3). However, since the flag F is already set at this stage, the microprocessor 11 11
Clamps the tip of the tracer head 4 to the clamp limit LCZ
Trace start point LC of the same as the height of Z + A Z
The axis is fixed, and the flag F that stores the fact that the copying control for the model 6 is being executed is released (step S4). Next, the microprocessor 11 determines whether or not the distance L from the tip of the tracer head 4 to the light receiving position on the model 6 is smaller than a preset comparison value L0, but immediately after the substantial copying is completed. At the present time, the distance L to the light receiving position
Is smaller than the comparison value L0. Therefore, the microprocessor 11 again changes the speed commands Vx and Vy to the servo amplifiers 18x and 18y for the respective axes to decelerate the feed speed of the table 31 (step S9), and the tracer head 4 is moved in the same manner as when the copying control is started. To prevent the occurrence of measurement error and the measurement bite by improving the accuracy of the distance measurement based on the latest two sampling results, and the following steps S1 to S3 and step S5. The processes of steps S7 and S9 are repeatedly executed to perform low-speed clamp copying.

While continuing the low-speed clamp scanning, the distance L from the tip of the tracer head 4 to the light receiving position on the model 6 becomes larger than a preset comparison value L0, and the optical distance sensors 5a and 5b. Is sufficiently separated from the switching point P5 from the model copying to the clamp copying by the determination processing in step S7 (FIG. 3).
(See P6 point of No.), the microprocessor 11 again changes the speed commands Vx and Vy to the servo amplifiers 18x and 18y for each axis to reset the feed speed of the table 31 to the normal clamp copying speed, and the same as the conventional method. Then, the clamp copying is performed (step S10).

[0021]

According to the non-contact copying control method of the present invention, the distance between the sensor and the model is measured even when the copying is performed along the clamp limit, and the measurement is performed in advance at the stage of performing the clamping copying. The clamp scanning speed is decelerated by detecting the switching point to the model scanning based on the value, so that the relative operation delay of the non-contact sensor that occurs during the transition from the clamp scanning to the model scanning can be prevented. , The measurement data bite caused by the delay of the measurement operation is eliminated. In addition, as a result of the clamp copying speed being reduced, the vertical movement required to keep the distance between the sensor and the model constant when starting copying on the model becomes slow, and the impact of each part of the mechanism is reduced. Is alleviated.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing a configuration of a non-contact copying control device and a machine tool of an embodiment to which a non-contact copying controlling method of the present invention is applied.

FIG. 2 is a flowchart showing an outline of copying control by the non-contact copying control apparatus according to the embodiment.

FIG. 3 is an operation principle diagram showing an outline of copying control of the embodiment.

[Explanation of symbols]

 1 Non-contact Copying Control Device 3 Machine Tool 4 Tracer Head 5a Optical Distance Sensor 5b Optical Distance Sensor 6 Model 11 Microprocessor 12 ROM 31 Table

Claims (1)

[Claims] 1. A non-contact sensor is used to measure the distance between the sensor and the model, and the feed of each axis of the machine tool is drive-controlled so that the measured value becomes a constant value, thereby performing copying control. In the non-contact copying control method described above, the non-contact sensor is relatively moved at the clamp copying speed along the clamp limit set with respect to the direction perpendicular to the table on which the model is placed, and measurement is performed. When the measured value becomes smaller than a preset comparison value, the clamp scanning speed is decelerated, and when the measured value of the sensor reaches the constant value, scanning control is performed at the scanning speed. .