JP2000107945A - Positioning method of reference position in wire cut electrical discharge machining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely position a reference position by storing the coordinate value of each time when the approaching movement is stopped and when the separating movement is stopped, and calculating the average coordinate value. SOLUTION: In a contact state, the operation of continuing separating movement is repeated also for the following segment time after a segment time is ended (step S108), and when non-contact state is judged, a motor is stopped after the segment time is ended (step S109), and the X-axial coordinate value at that time is stored (step S110). When reaching N-value, the contact detecting operation is ended (step S113). The average coordinate value of a number of stored X-axial coordinate values is calculated, the calculated average coordinate value is taken as the X-axial coordinate value of machining reference position (step 3114), and the positioning operation of the reference position related to X-axis is ended.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a workpiece which is stretched between a pair of guides spaced apart from each other and travels in the axial direction by moving the workpiece through a small discharge gap. And a discharge pulse is generated by applying an intermittent voltage pulse between the wire electrode and the workpiece in a state in which the machining fluid is interposed in the discharge gap, and a discharge pulse is generated between the wire electrode and the workpiece. In wire-cut electric discharge machining in which a relative machining feed in a direction substantially orthogonal to the direction is given to perform cutting of a desired contour shape, a machining reference position of the workpiece with respect to the wire electrode or the workpiece is placed. The vertical reference position of the pair of guides for vertically extending the wire electrode with respect to the processing table surface is moved between the wire electrode and the workpiece or the wire electrode while the wire electrode is moved at a predetermined tension and speed. It relates positioning method of determining detects the contact between the verticality jig and.

[0002]

2. Description of the Related Art FIG. 11 is a schematic view showing the construction of a wire electric discharge machine, in which reference numeral 1 denotes a bed, and 2 denotes an X provided on the bed 1 so as to be movable in X and Y axes orthogonal to each other.
Y cross tables, 3 and 4, X-axis and Y-axis drive motors for moving the XY cross table 2, 5, 6 rotary encoders for detecting the rotation angles of the motors 3, 4, 7
It is a mounting table fixedly provided on the Y cross table 2,
A processing table surface on which the workpiece 8 is mounted is formed on the mounting table 7 in parallel with the XY biaxial plane. These XY cross table 2, motors 3, 4 and encoders 5, 6
A machining feed mechanism is formed by the encoder, and each encoder 5 and 6 detects the amount of movement of each axis and performs feedback control as necessary.

[0003] 9 is a column provided upright on the bed 1,
Reference numerals 10 and 11 denote a pair of upper and lower arms that extend from the column 9 on the XY cross table 2 and are provided.
Reference numerals 12 and 13 denote a pair of upper and lower nozzle devices for injecting and supplying a processing liquid to the processing portion, and a pair of dice-shaped guides 15 for positioning the wire electrodes 14 of the processing portion facing the workpiece.
16 are fixedly supported in the nozzle devices 12 and 13, respectively. Reference numeral 17 denotes a Z-axis moving mechanism provided on the upper arm 10 and orthogonal to the XY biaxial plane. The Z-axis moving mechanism 17 has a distal end in a U-axis parallel to the X-axis and a V-axis parallel to the Y-axis. A UV cross table 18 is provided so as to be movable. The upper nozzle device 12 is fixedly supported by the table 18, and the lower nozzle device 13 is fixedly supported by the tip of the lower arm 11. Therefore, the upper guide 15 is movable in the U, V, and Z axis directions, and the lower guide 16 is in a fixed state. 19 is a Z-axis drive motor for moving the UV cross table 18 in the Z-axis direction, 20 is a rotary encoder for detecting a rotation angle of the motor 19, 21 and 22 are U-axis drive motor and V-axis drive motor of the UV cross table 18 , 23,
Reference numeral 24 denotes a rotary encoder for detecting the rotation angle of each of the motors 21 and 22.
The amount of movement of each axis is detected by 3, 24, and feedback control is performed.

At the time of processing, the wire electrode 14 is fed from a supply reel 25, guided by a roller 26, inserted through a processing start hole of the workpiece 8 from the upper guide 15, passes through the lower guide 16, and passes through a roller 27. It is stretched on a traveling route to the collection container 28 and travels with a predetermined tension and speed by the operation of the pulling drive mechanism 29 and the brake mechanism 30. Reference numeral 31 denotes a processing power source, an output terminal is connected to a conductive electrode 32 provided in contact with the wire electrode 14 and the workpiece 8, and a predetermined pulse condition (τon, τoff, Ip) is applied between the workpiece 8 and the wire electrode 14. ) Is intermittently applied, and the generated discharge state is monitored.

Reference numeral 33 denotes a computer, and a CPU 33
a, a ROM 33b, a RAM 33c, an input interface 33d, and an output interface 33e. Numeral 34 denotes an NC device that numerically controls the operation of each of the motors 3, 4, 19, 21, 22 by distributing pulses to the XY axis drivers 35 and the UVZ axis drivers 36 in accordance with instructions from the CPU 33a. Reference numeral 37 denotes an input device such as a keyboard, and various processing conditions such as pulse conditions of a voltage pulse, running conditions such as tension and speed of a wire electrode, supply conditions such as a flow rate of a working fluid, and a fluid pressure, and the like; , Other various set values, initial values, and the like are input and set. 38 is CRT
And the like, and the current position coordinate values of the X, Y, Z, U, and V axes, various processing conditions set by the input device 37, set values, initial values, and the progress of processing are displayed. Numeric display or graphic display.

In such a wire-cut electric discharge machine, the wire electrode 14 is moved with a predetermined tension and speed, and while the machining fluid is injected and supplied from the nozzles 12 and 13 into the discharge gap, the wire electrode 14 is connected to the workpiece 8. A voltage pulse is intermittently applied between the wire electrodes 14 to repeatedly generate a discharge,
A machining feed is provided between the two by the drive control of the motors 3 and 5, thereby cutting the predetermined contour shape. The machining feed is controlled by the CPU 33a in accordance with a machining program stored in the ROM 33b in advance. During the machining, the discharge state is monitored, and the quality of the machining state is determined based on the detected signal. , Or the change of the running condition of the wire electrode and the supply condition of the working fluid are performed.

On the other hand, in order to perform good machining at a predetermined position on the workpiece 8, an upper guide 15 for positioning the wire electrode 14 vertically (parallel to the Z axis) with respect to the machining table surface prior to the start of machining. Of the workpiece 8 with respect to the wire electrode 14 with the upper guide 15 disposed at the determined vertical reference position. 2 is required to be obtained by drive control. The positioning accuracy of the vertical reference position depends on the vertical error of the processing surface or the inclination error of the processing surface when performing the taper processing. Since the above processing position error is affected, it is important to accurately determine these reference positions. As a method of obtaining the vertical reference position, a method of detecting the contact between the vertical electrode jig installed on the processing table and the wire electrode is used, and a method of obtaining the processing reference position is as follows. In general, a method of detecting the contact between the wire electrode and the reference side surface or the inner surface of the reference hole is generally used.

In order to obtain each reference position by such a contact detection method, a contact detection device 39 is provided as shown in FIG. 11, and first, a jig for vertical setting is placed on a working table,
The contact detection device 39 is connected to the vertical setting jig and the communication line 32 to position the vertical reference position, and then the workpiece 8 is placed on the processing table in place of the vertical setting jig.
The contact detection device 39 is connected to the workpiece 8 and the communication line 32 to position the processing reference position.

Positioning of each reference position by the contact detection method is performed by a command from the CPU 33a according to a vertical reference position positioning program and a processing reference position positioning program stored in the ROM 33b in advance. In this aspect, various methods having different operation procedures have been conventionally proposed and are various, and detailed description thereof is omitted since the method becomes redundant. In the state where a low voltage (several volts to several tens of volts) of DC or AC voltage is applied between the wire electrode 14 and the wire electrode 14, first, the X-axis motor 3 is controlled to perform normal rotation driving to detect contact. Moving the object close to the wire electrode 14,
A contact is detected based on the output that is determined to decrease the detection voltage to a predetermined value or less, and a contact detection signal is sent to the computer 33.
After returning the motor 3 to the non-contact state by controlling the reverse rotation, the operation of detecting the contact by moving the motor 3 again again is performed a plurality of times.
5 is moved by a predetermined distance in the U-axis direction to tilt the wire electrode 14, or by further controlling the motor 19 to move the upper guide 15 by a predetermined distance in the Z-axis direction to perform the contact detection. X when contact is detected
The axis coordinate value or the X-axis coordinate value detected at every predetermined sampling period is taken into the computer 33 and stored in the RAM 3.
3c, the contact detection signal data and the coordinate value data are arithmetically processed by the CPU 33a according to the respective reference position positioning programs to calculate the vertical reference position on the U-axis or the processing reference position on the X-axis. In addition, in the case of repeated operation of contact detection by controlling the Y-axis motor 4 to rotate forward and reverse, or in the case of vertical positioning, the upper guide 15 is moved in the V-axis direction by a predetermined distance by drive control of the motor 22 during this contact detection operation. Or, furthermore, an operation of moving the motor 19 in the Z-axis direction by a predetermined distance by drive control, and taking in the detected Y-axis coordinate values, calculating the vertical reference position of the V-axis or the processing reference position of the Y-axis, In many cases, the UV coordinate values of the obtained vertical reference position and the XY coordinate values of the processing reference position are displayed on the display device 38.

FIG. 11 shows a configuration in which the stage 7 on which the contact detection target is placed is moved in the X-axis and the Y-axis to detect the contact with the wire electrode 14, but the present invention is not limited to this configuration. Instead, for example, the stage 7 may be fixedly provided on the bed 1, the column 9 may be provided on the XY cross table 2 provided on the bed 1, and the wire electrode 14 may be moved in the X-axis and the Y-axis. good. Further, the motors 3, 4, 19, 21,
As the motor 22, an AC motor, a DC motor, a stepping motor, or the like is used as appropriate.

In the positioning method performed in such an embodiment, there are various servo mechanisms for controlling the relative approach or separation movement between the contact detection target and the wire electrode. While the detected voltage drops below a predetermined value and the contact is detected, the relative proximity movement between the contact detection target and the wire electrode is continued, and when the contact is detected, the proximity movement is stopped and the current movement is stopped. After storing the axis coordinate values and then separating them by a predetermined distance, the operation of starting approach movement again and detecting the contact and storing the axis coordinate value at that time is repeated. The average of a number of axis coordinate values obtained is taken as a reference position. While the wire electrode is running in the same manner as in the processing, while moving the contact detection target and the wire electrode relatively close to or away from each other, a predetermined sampling cycle (for example, 10 μm) is performed.
) to determine whether the contact state or the non-contact state, the contact state determination output and the non-contact state determination output are separately counted, and the count of the contact state determination output is a predetermined preset value ( (For example, 100, 1000, etc.), the axes are moved by a unit length (for example, 1 μm) in a direction to separate them, and both counters are cleared. When the count number of the non-contact state determination output reaches a predetermined preset value, The axes are moved by the unit length in the direction in which they are brought close to each other, and the control to clear both counters is continued, so that the contact detection target and the wire electrode are not separated and kept in a state where they are not separated from each other. An axis coordinate value at the time of state determination or an axis coordinate value detected at predetermined time intervals (for example, 100 msec) is stored, and arithmetic processing such as averaging a large number of stored axis coordinate values is performed to determine a reference position. You. (JP-A-9-136220)
Various types of servo mechanisms have been adopted for the positioning method based on the contact detection method.

[0012]

The above-described positioning by the servo mechanism is a commonly used method.
If positioning is performed with the wire electrode running, the wire electrode will approach the contact detection target in a vibrating state, and it is unknown where the wire electrode is at the vibration amplitude when contact is detected. Therefore, the axis position at the time when the contact is detected does not indicate the surface position of the contact detection target, and even if the averaging process of a large number of axis coordinate values detected at each time of the contact detection is performed, It does not indicate the surface position of.

On the other hand, according to the positioning by the servo mechanism, the axis coordinate values detected one after another gradually converge on the center of vibration of the wire electrode. In this state, the reference position can be positioned with high accuracy without lowering the positioning accuracy due to the vibration of the wire electrode. However, in the positioning method using the servo mechanism, the contact state determination output and the non-contact state determination output determined by detecting the voltage are counted by separate counters, respectively, and the counter output that reaches the preset value first is used. Since the mechanism moves the axis by the unit length, the number of voltage samplings for discriminating the contact / non-contact state becomes enormous, a memory having a large capacity is required, and the data processing time becomes longer. If the number of samplings exceeds a certain threshold, the operation of the computer becomes unstable, such as determining that the state is unstable and displaying an error. Also, at the time of positioning by the contact detection method, although it is lower than the applied voltage at the time of processing, 10 V
Since the voltage before and after is applied and a weak discharge occurs at the time of contact / separation, if the number of voltage samplings becomes large (the number of contacts is relatively large), the surface of the contact detection target may be damaged or the chip due to discharge may be damaged. For example, it may adhere to the surface and reduce the positioning accuracy. Therefore, in order to shorten the time required for data processing, to stabilize the operation of the computer by avoiding the occurrence of errors, and to prevent damage to the surface of the contact detection target and deterioration of the positioning accuracy due to chip attachment, the number of voltage samplings is reduced. Is desirably as small as possible. The present invention has been made in view of such a problem, and in a state in which a wire electrode is run under the same conditions as during processing, a contact / non-contact state is determined with a small number of voltage samplings to accurately position a reference position. It is an object of the present invention to provide a positioning method using a contact detection method that can be performed.

[0014]

In order to achieve this object, a first aspect of the present invention is to provide an X-axis and Y-axis direction between a wire electrode and a workpiece or between a wire electrode and a vertical jig. A motor that operates a movement mechanism that provides relative proximity movement or separation movement is driven by setting the movement distance of the proximity movement and the separation movement to be the same as a certain segment time as a unit time and the same distance, and A voltage between both of the predetermined voltage application states is detected by using the segment time as a sampling period to determine whether the contact state is a contact state or a non-contact state. Each time the non-contact state is determined, the proximity movement of the segment time is repeated and continued, and if the contact state is determined during the proximity movement, the segment time ends. The motor is stopped and the motor is driven in reverse to start the separation movement, and the separation movement of the segment time is repeated while the contact state is determined for each sampling cycle during the separation movement, and the non-contact state is determined during the separation movement When the segment time is over, the motor is stopped at the end of the segment time and the contact detection operation is performed in such a manner that the motor is driven forward to start the proximity movement, and the X axis coordinates at each time when the proximity movement is stopped and at each time when the separation movement is stopped. The value is stored, the contact detection operation is terminated by the output of the device for judging the termination of the contact detection operation, the average coordinate value of many stored X-axis coordinate values is calculated, and the calculated average coordinate value is used as a processing reference. The X-axis coordinate value of the position or the X-axis coordinate value used for obtaining the vertical reference position, and then the same operation is performed for the Y-axis to obtain the Y-axis coordinate value of the machining reference position or the vertical reference position. Characterized in that so as to obtain a Y-axis coordinate value used for.

According to a second aspect of the present invention, the motor is driven by setting the approach movement distance to Lg and the separation movement distance to Lb while moving the motor at a fixed segment time as a unit time and moving at the segment time. In the predetermined voltage application state, the voltage between the two is detected by using the segment time as a sampling period to determine whether the state is the contact state or the non-contact state, and the storage of the X-axis coordinate value is performed at each time when the proximity movement is stopped. The contact detection operation is performed in the same manner as in the first invention, except that the X-axis coordinate value of the first embodiment and the X-axis coordinate value at each time when the separation movement is stopped are stored separately. The calculated average coordinate values of the X-axis coordinate values at the time of stopping the close movement and the X-axis coordinate values at the time of the separation movement stop are calculated, and the calculated coordinate values of the middle point of the average coordinate values are added to the two coordinate values. D is the distance between the average coordinate values As, Dm (Lb-Lg) / 2
The coordinate value obtained by adding (Lb + Lg) is used as the X-axis coordinate value of the processing reference position or the X-axis coordinate value used for obtaining the vertical reference position, and then the same operation is performed for the Y axis to obtain the processing reference position. , Or a Y-axis coordinate value used for obtaining a vertical reference position.

In the present invention, the sampling of the voltage is performed once during a certain segment time to determine the contact / non-contact state, and the non-contact state is determined during the close movement until the contact state is determined during the close movement. Until determined, the operation of driving the X-axis motor 3 or the Y-axis motor 4 for the segment time is repeated. As a time point for sampling the voltage, an intermediate time point of the segment time, or an appropriate time point in the first half or the second half can be set as the sampling time. Regarding the stop control of the motor, when the contact state is determined during the proximity movement, and when the non-contact state is determined during the separation movement, the motor is stopped at the end of the segment time in which the determination is performed. The motor is not limited to being stopped, but may be stopped at the end of the segment time following the segment time. Further, in such a servo mechanism, the command value for the motor is given as a distance L (μm) for moving at a constant segment time. Therefore, assuming that the segment time is Ta (msec), the axis moving speed V = L / Ta
(Μm / msec) is proportional to the set distance L, and the resolution of the axial movement is determined by the set distance L.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a flow chart showing an operation procedure of an embodiment of the first invention in which a contact detection operation is performed by setting a speed Vg of a proximity movement and a speed Vb of a separation movement to be the same. S101 to S114 indicate step numbers. First, the segment time Ta, the moving distance L of the proximity movement and the separation movement moving at the segment time, the number N of stored coordinate values are set, and the number n of stored coordinate values is cleared to 0 and reset. The shaft motor 3 is driven to rotate forward to start the proximity movement and start measuring the segment time (step S101). At a predetermined time during the segment time, the voltage is sampled to determine the contact / non-contact state ( (Step S102) In the case of non-contact, the operation of waiting for the end of the segment time is repeated (Step S103), and the operation of continuing the proximity movement for the next segment time is repeated. If the contact state is determined in Step S102, the segment time is determined. (Step S104), the motor is stopped, and the X-axis coordinate value at that time is stored in the RAM 33c (step S104). 05) Then, the X-axis motor 3 is driven in the reverse direction to start the separation movement and to start the measurement of the segment time (step S106), and the voltage is sampled at a predetermined time during the segment time to make contact / non-contact. The state is determined (step S107). If the state is the contact state, the end of the segment time is waited (step S10).
8) The operation of continuing the separation movement for the next segment time is repeated, and if the non-contact state is determined in step S107, the end of the segment time is waited (step S107).
109) Stop the motor and store the X-axis coordinate value at that time in the RAM 33c (step S110), add 1 to the count number n (step S111), and check whether the count number n has reached the set value N. Is determined (step S
112), if the N value has not yet been reached, step S
The operations from 101 to S112 are repeated, and when the N value is reached, the contact detection operation is terminated (step S113).

Here, an example of a contact detection operation performed in such a procedure will be described with reference to FIG. FIG. 2 shows that the segment time Ta is set to 2 msec, the distance L to be moved during the segment time is set to 1 μm, and a voltage is sampled at an intermediate point in each segment at a sampling period of 2 msec to determine the contact / non-contact state. It is a graph schematically showing the mode of axis movement when performing contact detection in the axial direction,
The vertical axis indicates the X-axis coordinate (μm), and the horizontal axis indicates time (msec). First, the motor 3 is driven to rotate forward from a sufficiently distant position to start a proximity movement (forward movement). In the case of this graph, non-contact is made in each segment until the movement of the fifth segment is completed (elapse of 10 msec). The state is discriminated and the vehicle continues to move forward. The contact state is discriminated by the voltage sampled at the intermediate point in time of the sixth segment (11 msec elapse), and at time a (end of the sixth segment), the motor stops and the proximity movement starts. Stop.

The stop of the motor is controlled by a logical product output of a contact / non-contact state discrimination output signal which outputs "1" in a contact state and "0" in a non-contact state, and a segment time end signal. At the time of proximity movement, the logical product output stops at "1", and at "0", motor driving is continued. At the time of remote movement, the logical product output stops at "0", and at "1", motor driving continues. Is done.

At the time point a, the X-axis coordinate position of the axis (the X-axis coordinate position of a portion facing the contact detection object of a straight line connecting the upper and lower guides) has not yet reached the contact detection object surface position. The wire electrode in the running state is several Hz to several K.
Since the frequency of Hz and the amplitude of several μm are constantly vibrating, there is a possibility that the contact is detected if the surface of the contact detection target falls within the range of the vibration amplitude of the wire electrode. However, since the position of the wire electrode in the amplitude at the time of voltage sampling is uncertain, contact is not always detected even if the contact detection target surface is within the range of the vibration amplitude of the wire electrode. However, the probability that the contact state is determined in a state where the coordinate position of the axis exactly matches the surface position of the contact detection target is approximately 50%.

Next, at time point a, the motor is controlled to rotate in the reverse direction to start the separation movement, and the non-contact state is determined based on the voltage sampled at the intermediate time point of the seventh segment (13 msec elapse). At the end point), the motor stops and the separation movement stops. Then
The motor is controlled to rotate in the forward direction, and the proximity movement starts again,
Until the movement of the tenth segment is completed (elapse of 20 msec), the non-contact state is determined in each segment, and the forward movement is continued. The contact state is determined by the voltage sampled at the intermediate time of the eleventh segment (elapse of 21 msec). Then, at time point c (end point of the eleventh segment), the motor stops and the proximity movement stops. Then, the motor is controlled to rotate in the reverse direction and the separation movement is started again. Until the movement of the thirteenth segment is completed (elapse of 26 msec), the contact state is determined in each segment and the backward movement is continued. At the time point (27 msec elapse time), the non-contact state is determined based on the voltage sampled. At time d (14th segment end time point), the motor is stopped and the separation movement is stopped. Proximity movement is started. Thereafter, similarly, each time point e, g, i,
At k and m, the proximity movement is stopped and the separation movement is started,
Further, at each of the time points f, h, j, and l, the contact detection operation changes so that the separation movement is stopped and the proximity movement is started.

Further, while performing such a contact detection operation, each coordinate value of the X axis at each of the points a to m (motor stop point) is taken into the computer 33 and RA
It is stored in M33c.

A count is performed each time the separation movement is stopped.
The count number is a predetermined preset value (N value, for example, 50
(0, 1000, etc.), the contact detection operation is terminated by the counter output. Alternatively, the above-mentioned Japanese Patent Application Laid-Open No. 9-1
As described in Japanese Patent Publication No. 36220, the X-axis coordinate value stored in the RAM 33c is divided into valid coordinate data and invalid coordinate data as appropriate in consideration of the amplitude of the wire electrode, and is stored as a standard. The effective coordinate data rate may be obtained by fuzzy inference based on the deviation and the number of effective coordinate data, and the contact detection operation may be terminated when the effective coordinate data rate reaches a predetermined value.

When the contact detection operation is completed in step S113 in this way, the CPU 33a causes the RAM 3
An average coordinate value of a large number of X-axis coordinate values stored in 3c (or an average coordinate value of effective coordinate values when classified into an effective coordinate value and an invalid coordinate value) is calculated, and the calculated average coordinate value is used as a machining reference position. Or the X-axis coordinate value used for obtaining the vertical reference position (step S114), the positioning operation of the reference position with respect to the X-axis ends.

When the positioning operation for the X axis is completed,
The same operation is performed for the Y axis, the Y axis coordinate value of the processing reference position or the Y axis coordinate value used for obtaining the vertical reference position is obtained, and the positioning of the reference position is completed.

FIG. 3 is a graph obtained by averaging the axial movements which repeat the approaching (forward) and separating (retreating) movements as shown in FIG. 2. Xg is the average coordinate of each X-axis coordinate value at the time of stopping the approaching movement. The value Xb indicates the average coordinate value of each X-axis coordinate value at the time when the separation movement is stopped, and the surface of the contact detection target exists between the average coordinate values Xg and Xb. Further, since the number of coordinate values stored in the RAM 33c is large, the distance Dm between the average coordinate values Xg and Xb substantially matches the average stroke of the axial movement. On the other hand, in the present invention, since the motor is driven with a fixed segment time as a unit time, the time from when the contact state is determined by the voltage sampling to the contact state at the time of the close movement and the non-contact state at the time of the separation movement is determined until the motor stops. Hereinafter, this will be referred to as a motor stop delay time), but the axis position will be too long. However, the motor stop delay time during the close movement and the separation movement are equal, and in the first invention, the close movement speed Vg and the separation movement Since the speed Vb is equal, the overshoot amount Dg at the time of approaching movement is equal to the overshoot amount Db at the time of separating movement, and the same overshoot amount at the time of forward movement and at the time of backward movement makes a large part of the average stroke Dm. Form. As described above, in the first invention, the proximity movement and the separation movement are performed under the same conditions, and the surface of the contact detection target is moved forward from the coordinate point Dg away from the point Xg and from the point Xb. In this case, the surface position (reference position) of the contact detection target is located at the middle point between the average coordinate values Xb and Xg, that is, the proximity movement stop time stored in the RAM 33c. It can be regarded as an average coordinate value of a large number of X-axis coordinate values at the time of the movement stop, and by setting the axis movement amount L of the segment time small, it is possible to increase the resolution and improve the positioning accuracy. According to the present invention, the reference position can be positioned with high accuracy by controlling the contact detection operation with a small number of voltage samplings.

On the other hand, in the contact detection operation, the speed at the time of forward movement and the speed at the time of retreat are not always set to the same speed. In the case of FIG. 2 of FIG.
msec), it is not preferable to prolong the short-circuit state after the contact because the contact detection target may be damaged or the wire electrode may be disconnected. Therefore, the separation moving speed Vb is moved close to the short-circuit state as soon as possible. The speed may be set faster than the speed Vg. The second invention is an invention relating to a method of positioning a reference position when the approach speed Vg and the separation speed Vb are different from each other.

An embodiment of the second invention will be described.
FIG. 4 is a flowchart showing an operation procedure according to an embodiment of the second invention, and S201 to S214 show step numbers. The difference between the flowchart of FIG. 4 and the flowchart of FIG. 1 is that, in the initial setting, the distance moved during the segment time Ta is the movement distance Lg during the proximity movement (forward) and the movement distance during the separation movement (retreat). Lb and separately set, and each coordinate value at the time of stopping the proximity movement and each coordinate value at the time of stopping the separation movement are separately stored in the RAM 33c (memory A).
And B) (steps S205 and S210), and the content of the data arithmetic processing in step S214 is different. Other operation procedures are the same as those in FIG. Then, in step S214 in FIG. 4, the CPU 33a stores the average coordinate value Xg (or Yg) of the X-axis (or Y-axis) coordinate values at the time of stopping the proximity movement stored in the memory A and the memory B. The stored X-axis (or Y-axis) at the time of the separation movement stop
The average coordinate value Xb (or Yb) of the coordinate values is calculated (if the effective coordinate value and the invalid coordinate value are classified, the average coordinate value of the effective coordinate values is calculated), and the calculated average coordinate values Xg (or Yg) are calculated. ), The coordinate value of the midpoint of Xb (or Yb) is Dm
An arithmetic process of adding (Lb−Lg) / 2 (Lb + Lg) is performed, and the obtained coordinate value is used as the X-axis (or Y-axis) coordinate value of the machining reference position, or the X-axis used to determine the vertical reference position (Or Y axis) coordinate values.

Here, in the second invention, an example of a contact detection operation when Vg <Vb will be described with reference to FIG.
FIG. 5 shows that the segment time Ta is set to 2 msec, the distance Lg to move to the segment time at the time of proximity movement is set to 1 μm, and the distance to move to the segment time at the time of separation movement Lb is set to 5 μm. FIG. 6 is a graph schematically showing an aspect of axis movement when contact detection in the X-axis direction is performed while determining a contact / non-contact state by sampling a voltage at a time point, and a vertical axis represents an axis coordinate of the X axis ( μm), and the horizontal axis indicates time (msec). In the case of FIG. 5 as well, the contact detection operation is performed in the same procedure as in FIG. 2, the approach movement is stopped at each of the time points a, c, e, and g, and the separation movement is started, and each of the time points b and d. , F, h, the separation movement is stopped and the proximity movement is started. Further, each coordinate value at the time of stopping the proximity movement is stored in the memory A (step S205),
Each coordinate value at the time when the separation movement is stopped is stored in the memory B (step S210). In this case, Vg: Vb
= Lg: Lb = 1: 5, the proximity and separation movements are performed, so that the time required for the separation movement is shorter than the time required for the proximity movement by 1/5 on average, and Vg = Vb. Contact (short circuit) is eliminated more quickly than in the case of 2.

FIG. 7 shows that Vg> in the second invention.
It is a graph which shows an example of the contact detection operation in the case of Vb,
The segment time Ta = 2 msec, the distance Lg = 5 μm to move at the segment time when moving close, and the distance Lb = 1 μm to move at the segment time when moving away, 2 msec
The voltage is sampled at the midpoint of each segment at the sampling cycle of X to determine the contact / non-contact state.
7 schematically shows an aspect of axial movement when contact detection in the axial direction is performed. In the case of FIG. 7 as well, the contact detection operation is performed in the same procedure as in FIG. 2, the approach movement is stopped at each of the time points a, c, e, g, and i, and the separation movement is started. , D,
The separation movement is stopped at f and h, and the proximity movement is started. Further, the respective coordinate values at the time of stopping the proximity movement are stored in the memory A (step S205), and the respective coordinate values at the time of stopping the separation movement are stored in the memory B (step S210).

FIG. 6 is a graph obtained by averaging the axis movement shown in FIG. 5, and FIG. 8 is a graph obtained by averaging the axis movement shown in FIG. 7. The average coordinate value Xg of each X-axis coordinate value at the time of stopping the proximity movement is shown.
And the surface of the contact detection target exists between the average coordinate values Xb of the X-axis coordinate values at the time when the separation movement is stopped, and the distance Dm between the average coordinate values Xg and Xb is substantially equal to the average stroke of the axial movement. Therefore, the motor stop delay time at the time of approach movement and the time of separation movement are equal. The operation up to this point is the same as that of the first invention in which Vg = Vb. However, since the overshoot amount is proportional to the speed of the axis movement, in the second invention in which Vg ≠ Vb (Lg ≠ Lb), the overshoot amount Dg at the time of approaching movement and the overshoot amount at the time of separation movement are provided. Db is different, and the ratio of the overtravel amount Dg at the time of forward movement and the overtravel amount Db at the time of retreat is Lg / Lb.
A large part of the average stroke Dm of the axial movement is formed by the respective overshoot amounts at the time of the forward movement and the backward movement. Therefore, the surface position (reference position) of the contact detection target is set at a speed ratio (Lg / L) from the middle point between the points Xg and Xb (average stroke Dm).
b), the deviation between points Xg and Xb
A coordinate point obtained by internally dividing m in a ratio of Lg: Lb can be regarded as a reference position. In the second invention, the subdivision point is obtained by adding Dm (Lb−Lg) / 2 (Lb + Lg) as the correction amount Rx to the coordinate value of the midpoint between the points Xg and Xb. By adding the correction amount Rx, the error of the deviation corresponding to the speed ratio generated when the midpoint between the points Xg and Xb is set as the reference position as in the first invention is eliminated, and the accuracy is improved. Enables positioning. In the present invention, the positive and negative directions of the coordinate of the axial movement are defined as the positive direction in which the wire electrode approaches the contact detection target.

As described above, according to the second aspect, even when the approaching speed Vg and the separating speed Vb are different, the contact detection operation is controlled with a small number of voltage samplings, and the average coordinate value of the stored coordinate values is obtained. An error between (the midpoint between the Xg point and the Xb point) and the surface position of the contact detection target can be corrected, and the reference position can be positioned with high accuracy. Further, the positioning accuracy can be improved by setting the axis movement amounts Lg and Lb of the segment time small and increasing the resolution. In addition, in the example of FIGS. 5 and 6, when 5Lg = Lb,
In the examples of FIGS. 7 and 8, the case where Lg = 5 Lb has been described, but the speed ratio between forward and backward is not limited to this, and an appropriate speed ratio such as 10 Lg = Lb, Lg = 10 Lb is adopted. Is done.

FIG. 9 shows an example using the method of the second invention and FIG.
Error of the value measured by detecting the contact of the diameter of the pin gauge of 2.5 mmφ from both sides of the pin gauge with the wire electrode of 0.2 mmφ at the seven speed ratios A to G shown in (1). Is a graph showing the error when the middle point of each of the average coordinate values Xg and Xb is set as the pin gauge surface position, and the square mark shows the correction amount Rx according to the second invention.
Are added to correct the error. 3mm
/ min axis movement speed is 0.1 in 2msec segment time.
It means the speed of moving μm. From FIG. 9, Xg point and Xb
Assuming that the midpoint of the point is the pin gauge surface position, the error increases as the speed ratio between the forward speed Vg and the backward speed Vb increases, and the correction amount Rx is added to the midpoint. It can be seen that the tendency of the error to increase due to the increase in the speed ratio between the forward and backward movements is eliminated, and that any of the speed ratios A to G has a substantially constant error. Therefore, according to the second aspect of the invention, by adding the correction amount Rx to the middle point, it is possible to eliminate an error caused by a difference in speed between when moving forward and when moving backward, and perform highly accurate positioning.

[0034]

As described above in detail, according to the first aspect of the present invention, when the moving speed Vg at the time of approaching movement and the moving speed Vb at the time of moving away from each other are equal, the contact detection operation can be performed with a small voltage sampling number. , And the reference position can be positioned with high accuracy. Further, according to the second aspect of the present invention, when the moving speed Vg at the time of approaching movement and the moving speed Vb at the time of moving away from each other are different, the contact detection operation is appropriately controlled with a small number of voltage samplings and stored. An error between the average coordinate value of the coordinate values and the surface position of the contact detection target can be corrected, and the reference position can be positioned with high accuracy.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an operation procedure according to an embodiment of the first invention.

FIG. 2 is a graph schematically showing an aspect of axial movement when contact detection is performed according to the first invention.

FIG. 3 is a graph obtained by averaging the axial movement shown in FIG. 2;

FIG. 4 is a flowchart showing an operation procedure according to an embodiment of the second invention.

FIG. 5 is a graph schematically showing an aspect of axial movement when contact detection is performed according to the second invention.

FIG. 6 is a graph obtained by averaging the axis movement shown in FIG. 5;

FIG. 7 is a graph schematically showing an aspect of axial movement when contact detection is performed according to the second invention.

FIG. 8 is a graph obtained by averaging the axis movement shown in FIG. 7;

FIG. 9 is a graph showing experimental results.

FIG. 10 is a table showing conditions of speed and speed ratio at the time of forward and backward movement in the graph of FIG. 9;

FIG. 11 is a configuration diagram schematically showing a wire electric discharge machine.

[Explanation of symbols]

 1 bed 2 XY cross table 3 4 X-axis and Y-axis drive motor 5 6 Rotary encoder 7 Table 8 Workpiece 9 Workpiece column 11, Upper arm and lower arm 12, 13 A pair of upper and lower working fluid jetting nozzle devices 14 Wire electrodes 15, a pair of upper and lower guides 17 Z-axis moving mechanism 18 UV cross table 19 Z-axis drive motor 20 Rotary encoder 21, 22 U-axis and V-axis drive motors 23, 24 Rotary encoder 25 Wire electrode supply reels 26, 27 Roller 28 Wire electrode collection container 29 Pull drive mechanism 30 …………… Brake mechanism 31 ………… … Processing power supply 32… Electrical communication 33 ………… Computer 34 …………………………………………………………………………… NC device 35 ………………… XY axis drivers 36 ………… UVZ axis drivers 37 …… ...... Input device 38 Display device 39 Contact detection device

Claims (2)

[Claims] 1. A wire electrode is stretched perpendicularly to a processing reference position of a workpiece with respect to a wire electrode stretched between a pair of spaced guides or a processing table surface on which the workpiece is placed. The vertical reference position of the pair of guides to be bridged is a state for detecting contact between the wire electrode and the workpiece or between the wire electrode and the vertical jig in a state where the wire electrode is traveled and moved with a predetermined tension and speed. A voltage is applied, and a moving mechanism for providing relative approach movement or separation movement between the two in the X-axis and Y-axis directions is operated, and the contact is determined by detecting the contact / non-contact between the two from the change in the voltage. In a method of positioning a reference position in wire-cut electric discharge machining, a motor that operates the moving mechanism is moved in a predetermined segment time as a unit time and the proximity time is moved in the segment time. At the same time, the moving distance and the moving distance are set to be the same and driven, and the segment time is used as a sampling period to detect the voltage to determine the contact state or the non-contact state. When the non-contact state is determined for each sampling period during the close movement by the forward rotation drive, the close movement of the segment time is repeated and continued, and when the contact state is determined during the close movement, the segment time ends. At the time, the motor is stopped and reversely driven to start the separation movement, and during the separation movement, while the contact state is determined for each sampling cycle, the separation movement of the segment time is repeated and continued. When the contact state is determined, the motor is stopped at the end of the segment time, and the contact detection operation is performed in such a manner that the motor is driven forward and the approach movement is started. Storing the X-axis coordinate values at each time point at which the approaching movement is stopped and at each time point at which the separating movement is stopped, and terminating the contact detection operation by an output of a device for determining the end of the contact detection operation; An average coordinate value of a large number of stored X-axis coordinate values is calculated, and the calculated average coordinate value is used as an X-axis coordinate value of the machining reference position, or as an X-axis coordinate value used for obtaining the vertical reference position. Next, the same operation is performed on the Y axis to obtain the Y axis coordinate value of the machining reference position or the Y axis coordinate value used for obtaining the vertical reference position. Positioning method of the reference position. 2. A wire electrode is stretched perpendicularly to a working reference position of a workpiece with respect to a wire electrode stretched between a pair of spaced guides or a working table surface on which the workpiece is placed. The vertical reference position of the pair of guides to be bridged is a state for detecting contact between the wire electrode and the workpiece or between the wire electrode and the vertical jig in a state where the wire electrode is traveled and moved with a predetermined tension and speed. A voltage is applied, and a moving mechanism for providing relative approach movement or separation movement between the two in the X-axis and Y-axis directions is operated, and the contact is determined by detecting the contact / non-contact between the two from the change in the voltage. In a method of positioning a reference position in wire-cut electric discharge machining, a motor that operates the moving mechanism is moved in a predetermined segment time as a unit time and the proximity time is moved in the segment time. The driving distance is set to Lg, the separation moving distance is set to Lb, and the driving is performed. The segment time is used as a sampling cycle to detect the voltage to determine whether the contact state or the non-contact state. When the non-contact state is determined for each sampling period during the proximity movement by the forward rotation drive of the motor, the proximity movement of the segment time is repeated and continued, and when the contact state is determined during the proximity movement, the segment time is determined. At the end, the motor is stopped and reversely driven to start the separation movement, and during the separation movement, while the contact state is determined for each sampling cycle, the separation movement of the segment time is repeated and continued, and at the time of the separation movement When the non-contact state is determined, the contact detection operation is performed in a mode in which the motor is stopped at the end of the segment time and the motor is driven forward to start the approach movement. The X-axis coordinate value at each time when the proximity movement is stopped and the X-axis coordinate value at each time when the separation movement is stopped are separately stored, and the output of the device for determining the end of the contact detection operation The contact detection operation is terminated by calculating the average coordinate value of each of the stored X-axis coordinate values at the time of stopping the proximity movement and the X-axis coordinate value at the time of stopping the separation movement. The distance between the two average coordinate values is defined as Dm, and the distance between the two average coordinate values is defined as Dm (L
The coordinate value obtained by adding (b−Lg) / 2 (Lb + Lg) is used as the X-axis coordinate value of the machining reference position or the X-axis coordinate value used for obtaining the vertical reference position. Performing an operation to determine a Y-axis coordinate value of the machining reference position or a Y-axis coordinate value used for determining the vertical reference position. A method of positioning a reference position in wire-cut electric discharge machining.