JP4017764B2 - Reference position positioning method in wire cut electric discharge machining - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  According to the present invention, a wire electrode is stretched between a pair of guides arranged at an interval to travel in the axial direction, and a workpiece is disposed opposite to the wire electrode via a minute discharge gap, and the discharge While intermittently applying a voltage pulse between the wire electrode and the workpiece with the machining fluid interposed in the gap to repeatedly generate a discharge pulse, the relative distance in the direction substantially perpendicular to the axial direction of the wire electrode is generated between the two. In wire-cut electric discharge machining that cuts a desired contour shape by giving a specific machining feed, the wire is placed on the machining reference position of the workpiece relative to the wire electrode or on the machining table surface on which the workpiece is placed The vertical reference position of the pair of guides that vertically stretch the electrode is moved between the wire electrode and the workpiece or between the wire electrode and the vertical extraction jig while the wire electrode is moved at a predetermined tension and speed. Contact It relates positioning method of determining by detecting.
[0002]
[Prior art]
  FIG. 11 is a configuration diagram showing an outline of a wire cut electric discharge machining apparatus. 1 is a bed, 2 is an XY cross table provided on the bed 1 so as to be movable in the X and Y axis directions orthogonal to each other, and 3 and 4 are X-axis and Y-axis drive motors for moving the XY cross table 2, 5 and 6 are rotary encoders for detecting the rotation angles of the motors 3 and 4, and 7 is a mounting table fixed on the XY cross table 2. A processing table surface for mounting the workpiece 8 is formed on the mounting table 7 in parallel with the XY biaxial plane. The XY cross table 2, the motors 3 and 4, and the encoders 5 and 6 constitute a machining feed mechanism. If necessary, the encoders 5 and 6 detect the amount of movement of each axis and perform feedback control.
[0003]
  Reference numeral 9 denotes a column provided upright on the bed 1, and reference numerals 10 and 11 denote a pair of upper and lower upper and lower arms provided on the XY cross table 2 extending from the column 9. Reference numerals 12 and 13 denote a pair of upper and lower nozzle devices for injecting a processing liquid to the processing portion, and a pair of dice-shaped guides 15 and 16 for positioning the wire electrode 14 of the processing portion facing the workpiece are provided in the nozzle device 12. , 13 are fixedly supported. Reference numeral 17 denotes a Z-axis moving mechanism orthogonal to the XY biaxial plane provided on the upper arm 10. The distal end of the Z-axis moving mechanism 17 has a U-axis parallel to the X-axis and a V-axis direction parallel to the Y-axis. A UV cross table 18 is movably provided. The upper nozzle device 12 is fixedly supported on the table 18, and the lower nozzle device 13 is fixedly supported on the tip of the lower arm 11. Accordingly, 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 that moves the UV cross table 18 in the Z-axis direction, 20 is a rotary encoder that detects the rotation angle of the motor 19, and 21 and 22 are U-axis drive motor and V-axis drive motor of the UV cross table 18. , 23 and 24 are rotary encoders for detecting the rotation angle of each of the motors 21 and 22, and the amounts of movement of the respective axes are detected by the respective encoders 20, 23 and 24 as necessary, and are feedback-controlled.
[0004]
  At the time of processing, the wire electrode 14 is fed from the supply reel 25, guided by the roller 26, inserted from the upper guide 15 through the processing start hole of the workpiece 8, passes through the lower guide 16, passes through the roller 27, and is collected in 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 machining power source. An output terminal is connected to the workpiece 8 provided in contact with the wire electrode 14 and the workpiece 8, and predetermined pulse conditions (τon, τoff, Ip between the workpiece 8 and the wire electrode 14 are connected. Etc.) are intermittently applied, and the generated discharge state is monitored.
[0005]
  A computer 33 includes a CPU 33a, a ROM 33b, a RAM 33c, an input interface 33d, and an output interface 33e. Reference numeral 34 denotes an NC device that numerically controls the operations of the motors 3, 4, 19, 21, and 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. The input device 37 is used for various processing conditions such as voltage pulse conditions, wire electrode tension, speed and other running conditions, machining fluid flow rate, fluid pressure and other processing conditions, and Various other set values, initial values, etc. are input and set. Reference numeral 38 denotes a display device such as a CRT, which is the current position coordinate value of each axis of X, Y, Z, U, and V, various machining conditions set by the input device 37, set values, initial values, etc., and the progress of machining. The situation etc. is displayed numerically or graphically.
[0006]
  In such a wire cut electric discharge machining apparatus, the workpiece 8 and the wire electrode 14 are moved while the wire electrode 14 is moved and moved at a predetermined tension and speed, and the machining liquid is jetted and supplied from the nozzles 12 and 13 to the discharge gap. A voltage pulse is intermittently applied in the meantime to repeatedly generate a discharge, and a machining feed by driving control of the motors 3 and 5 is given between them to cut a 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, the discharge state is monitored during machining, the quality of the machining state is determined by the detected signal, the application of the voltage pulse is stopped, the pulse condition Or control such as changing the wire electrode running condition and machining fluid supply condition.
[0007]
  On the other hand, in order to perform good processing on a predetermined position of the workpiece 8, prior to the start of processing,
A vertical reference position of the upper guide 15 for positioning the wire electrode 14 perpendicularly to the processing table surface (parallel to the Z axis) is determined by driving the UV cross table 18 and the upper side of the determined vertical reference position is It is necessary to determine the machining reference position of the workpiece 8 with respect to the wire electrode 14 by driving the XY cross table 2 with the guides 15 disposed, and the vertical reference position positioning accuracy depends on the machining surface perpendicularity error or taper. It is important to obtain these reference positions with high accuracy because the machining surface tilt error when machining is affected and the positioning accuracy of the machining reference position affects the machining position error on the workpiece.
  As a method for obtaining the vertical reference position, a method for obtaining the vertical reference position by detecting the contact between the vertical alignment jig placed on the machining table and the wire electrode, and a method for obtaining the machining reference position include the workpiece. Generally, a method for obtaining the contact by detecting the contact between the reference side surface or the inner surface of the reference hole and the wire electrode is commonly used.
[0008]
  In order to obtain each reference position by such a contact detection method, as shown in FIG. 11, a contact detection device 39 is provided. First, a vertical jig is placed on the processing table, and the contact detection device 39 is placed vertically. The vertical reference position is positioned by connecting to the feeding jig and the electronic device 32, and then the workpiece 8 is placed on the machining table in place of the vertical jig, and the contact detection device 39 is machined. The processing reference position is positioned by connecting to the object 8 and the electronic device 32.
[0009]
  Positioning of each reference position by the contact detection method is performed according to a command from the CPU 33a according to a vertical reference position positioning program and a machining reference position positioning program stored in advance in the ROM 33b. Various methods with different operation procedures have been proposed in the past, and the method is redundant and redundant. Therefore, detailed description of each method is omitted. In a state where a low voltage (several V to several tens V) 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 rotate forward to detect contact. The object is moved close to the wire electrode 14, contact is detected based on the output of which the detection voltage has been reduced to a predetermined value or less, a contact detection signal is sent to the computer 33, and the motor 3 is driven in reverse to control the non-contact state. After returning to the position, the operation of detecting the contact by moving again again is performed a plurality of times. In the case of vertical alignment, the motor 21 is driven and the upper guide 15 is moved in the U-axis direction by a predetermined distance to tilt the wire electrode 14. Operation, there is Further, the contact detection is performed by combining the operation of driving the motor 19 to move the upper guide 15 in the Z-axis direction by a predetermined distance, and the X-axis coordinate value when the contact is detected or every predetermined sampling period. The detected X-axis coordinate value is taken into the computer 33 and stored in the RAM 33c, and the contact detection signal data and the coordinate value data are processed by the CPU 33a according to each reference position positioning program to process the vertical reference position of the U axis or the processing of the X axis. The reference position is calculated, and the Y-axis motor 4 is rotated in the forward / reverse direction and the contact detection is repeated, and the upper guide 15 is moved during the contact detection operation. An operation for moving the motor 22 in a predetermined distance in the V-axis direction by drive control, or further moving the motor 19 in a direction of a predetermined distance in the Z-axis direction by drive control; Then, the detected Y-axis coordinate value is taken in and calculated to calculate the V-axis vertical reference position or the Y-axis processing reference position, and the obtained UV reference value of the vertical reference position and the processing reference position XY There are many methods performed in such a manner that each axis coordinate value is displayed on the display device 38.
[0010]
  Moreover, in FIG. 11, although it is the structure which moves the mounting base 7 in which a contact detection target object is mounted to a X-axis and a Y-axis, and detects a contact with the wire electrode 14, it is not restricted to this structure, for example, The stage 7 may be fixed on the bed 1 and the column 9 may be provided on the XY cross table 2 provided on the bed 1 to move the wire electrode 14 side to the X axis and the Y axis. As the motors 3, 4, 19, 21, and 22, an AC motor, a DC motor, a stepping motor, or the like is appropriately used as necessary.
[0011]
  In the positioning method performed in such a manner, there are various servo mechanisms for controlling the relative proximity or separation movement between the contact detection object and the wire electrode, for example,
  (1) While the voltage is constantly detected, the relative proximity movement between the contact detection object and the wire electrode is continued until the detection voltage drops below a predetermined value and contact is detected. Stop the movement and memorize the axis coordinate value at that time. Then, after separating the two by a predetermined distance, start the approach again and detect the contact and repeat the operation to memorize the axis coordinate value at that time. When contact is detected, an average of a large number of stored coordinate values is taken as a reference position.
  (2) While the wire electrode is running as in the processing, the voltage is detected at a predetermined sampling period (for example, 10 μsec) while the contact detection object and the wire electrode are moved relatively close to or apart from each other. Whether the contact state or non-contact state is determined, the contact state determination output and the non-contact state determination output are separately counted and the contact state determination output count reaches a predetermined preset value (for example, 100, 1000, etc.). Then, the axis is moved by a unit length (for example, 1 μm) in the direction to separate them, and both counters are cleared. When the count value of the non-contact state determination output reaches a predetermined preset value, the units are moved in the direction in which they are brought close to each other. Continue the control to move the shaft by the length and clear both counters, and keep the contact detection object and the wire electrode without attaching them. Storing the axial coordinate values detected in the axial coordinate value or every predetermined time during determination (e.g. 100 msec), the average of the stored multiple-axis coordinate value by performing arithmetic processing, such as taking a reference position. (See JP-A-9-136220)
  Various servo mechanisms are employed in the positioning method by the contact detection method.
[0012]
[Problems to be solved by the invention]
  Positioning by the servo mechanism of (1) is a method that is generally used, but when positioning with the wire electrode running, the wire electrode approaches the contact detection object in a vibrating state. Since the position of the vibration amplitude of the wire electrode is unknown when contact is detected, the axis position at the time when contact is detected does not indicate the surface position of the contact detection target, and contact detection Even if averaging processing of a large number of axis coordinate values detected every hour does not indicate the surface position of the contact detection object.
[0013]
  On the other hand, according to the positioning by the servo mechanism of (2), since the detected axial coordinate value gradually converges to the vibration center of the wire electrode, the wire electrode was run under the same conditions as during processing. In this state, the reference position can be positioned with high accuracy without reducing the positioning accuracy due to the vibration of the wire electrode.
  However, in the positioning method using the servo mechanism (2), the contact state determination output and the non-contact state determination output determined by detecting the voltage are counted by separate counters, and the preset value is reached first. Since it is a mechanism for moving the axis by the unit length by the counter output, the number of voltage sampling for contact / non-contact state discrimination becomes enormous, requiring a memory with a large capacity and increasing the data processing time. In addition, if the number of samplings exceeds a certain threshold, it is determined that the state is unstable, and an error display is issued. For example, the computer operation becomes unstable. Also, at the time of positioning by the contact detection method, although it is lower than the applied voltage at the time of machining, a voltage of around 10V is applied, and a weak discharge is generated at the time of contact / separation, so a large number of voltage samplings (relatively) If the number of times of contact is large), the surface of the contact detection object is damaged, or a chip due to electric discharge adheres to the surface, thereby reducing the positioning accuracy. Therefore, in order to shorten the time required for data processing, stabilize the computer operation by avoiding errors, and prevent deterioration of positioning accuracy due to damage to the surface of the contact detection target object or chip adhesion, the number of voltage sampling It is desirable to reduce as much as possible.
  In view of such problems, the present invention can accurately determine the reference position by determining the contact / non-contact state with a small number of voltage samplings while the wire electrode is running under the same conditions as in the processing. An object of the present invention is to provide a positioning method based on a contact detection method that can be used.
[0014]
[Means for Solving the Problems]
  To achieve this object, the present inventionThe basic principle technology used in the implementation ofA motor that operates a moving mechanism that gives a relative proximity movement or separation movement in the X-axis and Y-axis directions between the wire electrode and the workpiece or between the wire electrode and the vertical jig is set to a certain segment time. And the movement distance of the proximity movement and the separation movement that move during the segment time is set to be the same, and the voltage between both of the predetermined voltage application states is detected using the segment time as a sampling period to determine whether the contact state is not First, with regard to the X axis, the proximity movement of the segment time is continuously repeated for the X axis while the non-contact state is determined for each sampling period during the proximity movement by the forward rotation of the motor. If the contact state is determined during movement, the motor is stopped at the end of the segment time, and reversely driven to start remote movement, and sampled during remote movement. While the contact state is determined for each period, the segment time separation is repeated and continued, and when the non-contact state is determined during the separation movement, the motor is stopped at the end of the segment time and driven forward to move closer. The contact detection operation is performed in such a manner that the contact movement is started, the X-axis coordinate value at each time point when the proximity movement is stopped and the time point when the separation movement is stopped is stored, and the contact detection is performed by the output of the device that determines the end of the contact detection operation X axis used to end the operation, calculate the average coordinate value of a large number of stored X axis coordinate values, use the calculated average coordinate value as the X axis coordinate value of the machining reference position, or obtain the vertical reference position The coordinate value is set, and then the same operation is performed on the Y axis to obtain the Y axis coordinate value used for obtaining the Y axis coordinate value or the vertical reference position of the machining reference position.It is to make.
[0015]
  Therefore, this project that uses the above-mentioned technology as a basic technology.Ming is driven by setting the proximity movement distance to be Lg and the separation movement distance to be Lb and moving the motor at a certain segment time as a unit time and the voltage between the two in a predetermined voltage application state. The segment time is detected as a sampling period to determine whether it is in a contact state or a non-contact state, and the storage of the X-axis coordinate value is separated from the X-axis coordinate value at each time when the proximity movement is stopped and the separation movement is stopped. Other than making it memorize separately for each X-axis coordinate value at each time pointIn the case of the basic technology mentioned aboveThe same contact detection operation was performed, and after the operation was completed, the average coordinate values of the stored X-axis coordinate values at the time of stopping the proximity movement and the X-axis coordinate values at the time of stopping the separation movement were calculated and calculated. The coordinate value obtained by adding Dm (Lb−Lg) / 2 (Lb + Lg) to the coordinate value of the middle point of both average coordinate values, where Dm is the distance between both average coordinate values, is the X-axis coordinate value of the machining reference position. Or the X-axis coordinate value used for obtaining the vertical reference position, and then performing the same operation on the Y-axis to obtain the Y-axis coordinate value or the vertical reference position of the machining reference position. It is characterized in that it is requested.
[0016]
  In the present invention, the voltage is sampled once during a certain segment time to determine the contact / non-contact state, and the non-contact state is determined during the remote movement until the contact state is determined during the proximity movement. Until then, 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 at which the voltage is sampled, 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 point. Regarding the motor stop control, 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 when the determination is performed. In addition to the mode of stopping, the motor may be stopped at the end of the segment time next to the segment time.
  In such a servo mechanism, since the command value for the motor is given as a distance L (μm) that moves in a certain segment time, if the segment time is Ta (msec), the shaft moving speed V = L / Ta (Μm / msec) is proportional to the set distance L, and is determined by the set distance L for the resolution of the axis movement.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
  In FIG. 1, the contact detection operation is performed by setting the proximity movement speed Vg and the separation movement speed Vb to be the same.An example of the basic technique of the present invention described aboveIt is a flowchart which shows the operation procedure. 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, and the stored coordinate value number N value are set, the coordinate value storage count n to be counted is cleared to 0, and then reset. The shaft motor 3 is driven forwardly to start proximity movement and segment time measurement is started (step S101), and a voltage is sampled at a predetermined time point in the segment time to determine a contact / non-contact state ( Step S102), in the case of non-contact, waits for the end of the segment time (Step S103), repeats the operation of continuing the proximity movement for the next segment time, and if the contact state is determined in Step S102, the segment time (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 reverse to start the separation movement and the measurement of the segment time is started (step S106), and the voltage is sampled at a predetermined point in the segment time to make contact / non-contact The state is discriminated (step S107), and in the case of the contact state, the end of the segment time is awaited (step S108), and the operation of continuing the separation movement is repeated for the next segment time, and the non-contact state is discriminated in step S107. In the case where the segment time is over (step S109), the motor is stopped and the X-axis coordinate value at that time is stored in the RAM 33c (step S110), and 1 is added to the count number n (step S111). Then, it is determined whether or not the count number n has reached the set value N (step S112), and has not yet reached the N value. If the repeated operation of steps S101 to S112, if it reaches the N value to terminate the contact sensing operation (step S113).
[0018]
  Here, an example of the contact detection operation performed in such a procedure will be described with reference to FIG.
  FIG. 2 shows that the segment time Ta = 2 msec, the distance L to move to the segment time = 1 μm, the voltage is sampled at an intermediate time point of each segment with a sampling period of 2 msec, and the contact / non-contact state is determined. It is a graph which shows typically the mode of an axis movement at the time of performing contact detection of an axial direction, a vertical axis shows axis coordinates (micrometer) of an X axis, and a horizontal axis shows time (msec).
  First, the motor 3 is driven forward from a sufficiently separated position to start proximity movement (advance). In the case of this graph, no contact is made in each segment until the movement of the fifth segment is completed (10 msec has elapsed). The state is determined and the vehicle continues moving forward. The contact state is determined by the voltage sampled at the intermediate time of the sixth segment (at the time when 11 msec has elapsed). Stop.
[0019]
  The motor stop is controlled by the logical product output of the contact / non-contact state discrimination output signal that outputs “1” in the contact state and “0” in the non-contact state and the end signal of the segment time. The logical product output stops at “1”, and the motor drive is continued at “0”. During the remote movement, the logical product output stops at “0”, and the motor drive is continued at “1”.
[0020]
  Further, at the time point a, the X-axis coordinate position of the axis (the X-axis coordinate position of the portion facing the linear contact detection target object connecting the upper and lower guides) has not yet reached the contact detection target surface position, but the running state Since the wire electrode in FIG. 1 constantly vibrates with a frequency of several Hz to several KHz and an amplitude of several μm, contact may be detected if the surface of the object to be detected falls within the vibration amplitude range of the wire electrode. There is. However, since the position of the wire electrode at the time of voltage sampling is uncertain, contact is not always detected even if the surface of the contact detection object is within the vibration amplitude range of the wire electrode. First, the probability that the contact state is determined is approximately 50% when the coordinate position of the axis is exactly the same as the surface position of the contact detection target.
[0021]
  Next, at time point a, the motor is driven in reverse rotation to start separation movement, and the non-contact state is determined by the voltage sampled at the intermediate time point of the seventh segment (13 msec elapsed time point), and time point b (seventh segment end time point) The motor stops and the remote movement stops. Next, the motor is controlled to rotate forward and the proximity movement is started again. Until the movement of the tenth segment is completed (20 msec), the non-contact state is determined in each segment, and the forward movement is continued. The contact state is discriminated based on the voltage sampled at the intermediate time (21 msec), and the motor stops at the time c (end of the eleventh segment) to stop the proximity movement. Next, the motor is controlled to rotate in reverse and the separation movement is started again. Until the movement of the thirteenth segment is completed (26 msec has elapsed), the contact state is determined in each segment and the retraction is continued. The non-contact state is determined based on the voltage sampled at the time (27 msec), the motor stops at the time d (end of the 14th segment), the separation movement is stopped, and then the motor is controlled to rotate forward and again. Proximity movement is started.
  Thereafter, similarly, at each time point e, g, i, k, m, the proximity movement is stopped and the separation movement is started, and at each time point f, h, j, l, the separation movement is stopped and the proximity movement is started. The contact detection operation changes as it is.
[0022]
  Further, while performing such a contact detection operation, each coordinate value of the X axis at each time point a to m (motor stop time) is taken into the computer 33 and stored in the RAM 33c.
[0023]
  Also, the count is performed every time the remote movement stops, and the count number is a predetermined preset value.
When it reaches (N value, for example, 500, 1000, etc.), the contact detection operation is terminated by the counter output. Alternatively, as described in the above-mentioned JP-A-9-136220, the X-axis coordinate value stored in the RAM 33c is appropriately divided into effective coordinate data and invalid coordinate data in consideration of the amplitude of the wire electrode, and stored. An effective coordinate data rate is obtained by fuzzy inference based on the standard deviation of all stored coordinate data and the number of effective coordinate data, and the contact detection operation is terminated when the effective coordinate data rate reaches a predetermined value. good.
[0024]
  In this manner, when the contact detection operation is completed in step S113, the CPU 33a calculates an average coordinate value of a large number of X-axis coordinate values stored in the RAM 33c (in the case of classifying the effective coordinate value and the invalid coordinate value, the effective coordinate value). (Average coordinate value) is calculated, and the calculated average coordinate value is used as the X-axis coordinate value of the machining reference position or as the X-axis coordinate value used for obtaining the vertical reference position (step S114). End the positioning operation.
[0025]
  When the positioning operation with respect to the X-axis is completed, the same operation is performed with respect to the Y-axis to obtain the Y-axis coordinate value used for obtaining the Y-axis coordinate value or the vertical reference position of the machining reference position, and the positioning of the reference position is finished. .
[0026]
  FIG. 3 is a graph obtained by averaging axial movements that repeat proximity (advance) and separation (retreat) movements as shown in FIG. 2, and Xg is an average coordinate value of each X-axis coordinate value at the time of proximity movement stop, 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 coincides with the average stroke of the axis movement. on the other hand, Take this bookDepartureWith the technology that is the basis of MingSince the motor is driven with a certain segment time as a unit time, the time from when the contact state is determined during proximity movement to the non-contact state during separate movement is determined by voltage sampling until the motor stops (hereinafter referred to as motor stop) This is referred to as the delay time), but the axis position goes too far, but the motor stop delay time is the same for close movement and remote movement.A specific example of basic technologySince the proximity movement speed Vg and the separation movement speed Vb are equal to each other, the overshoot amount Dg at the time of the proximity movement is equal to the overshoot amount Db at the time of the separation movement. Many parts of the average stroke Dm are formed. In this way, proximity movement and separation movement are performed under the same conditions.IfSince the surface of the contact detection object is between the coordinate point that is Dg away from the Xg point in the backward direction and the coordinate point that is Db away from the Xb point in the forward direction, the surface position of the contact detection object is (Reference position) can be viewed as the middle point of each average coordinate value Xb and Xg, that is, the average coordinate value of a large number of X-axis coordinate values stored in the RAM 33c at the time of close movement stop and the time of remote movement stop. It is possible to improve the positioning accuracy by increasing the resolution by setting the axis movement amount L small., The basic technology On the technical principle ofTherefore, the reference position can be positioned with high accuracy by controlling the contact detection operation with a small number of voltage samplings.
[0027]
  On the other hand, in the contact detection operation, the forward speed and the backward speed are not always set to be the same. For example, when approaching to detect contact, the speed is approached carefully at a relatively low speed (see FIG. 2 described above). In this case, both the forward and backward movements are 0.5 μm / msec.) Prolonging the short-circuit state after contact is not preferable because it may cause damage to the contact detection target or disconnection of the wire electrode. In order to eliminate as soon as possible, the separation movement speed Vb may be set faster than the proximity movement speed Vg.. So this departureAs you can see, the proximity movement speed Vg and the separation movement speed VbAre the same and differentIfRegardless ofIssues related to the sub-position positioning methodIt is effective as a lightis there.
[0028]
  NextA clear example will be described.
  FIG.FromIt is a flowchart which shows the operation procedure of one clear example, and S201-S214 shows a step number.
  4 is different from the flowchart of FIG. 1 in the initial setting.
The distance traveled during the segment time Ta is set separately for the proximity travel (forward) travel distance Lg and the separate travel (backward) travel distance Lb. Each coordinate value at the time of stopping the separation movement is separately stored in the RAM 33c (memory A and B) (step S205 and step S210), and the contents of the data calculation processing in step S214 are different. , Other operating proceduresIs the figure aboveSame as 1.
  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 stored in the memory A and stored in the memory A in the memory B. Calculates the average coordinate value Xb (or Yb) of the stored X-axis (or Y-axis) coordinate values at the time of stopping the separated movement (if the coordinate values are classified into valid coordinate values and invalid coordinate values, the average of the valid coordinate values) The coordinate value is calculated), and Dm (Lb−Lg) / 2 (Lb + Lg) is added to the coordinate value of the middle point of the calculated average coordinate values Xg (or Yg) and Xb (or Yb). The obtained coordinate value is set as the X-axis (or Y-axis) coordinate value of the machining reference position, or the X-axis (or Y-axis) coordinate value used for obtaining the vertical reference position.
[0029]
  hereV for the present inventionAn example of the contact detection operation in the case of g <Vb will be described with reference to FIG.
  FIG. 5 shows that the segment time Ta = 2 msec, the distance Lg to move to the segment time at the close movement, Lg = 1 μm, the distance Lb to move to the segment time at the remote movement, Lb = 5 μm, and the middle of each segment at the sampling period of 2 msec It is a graph which shows typically the mode of an axis movement at the time of performing contact detection of an X-axis direction, sampling a voltage at the time and discriminating a contact / non-contact state, and a vertical axis is an axis coordinate (X axis ( μm), and the horizontal axis represents time (msec).
  In the case of FIG. 5, the contact detection operation is performed in the same procedure as in FIG. 2, the proximity movement is stopped and the separation movement is started at each time point a, c, e, g, and each time point b, d. , F, h, the separation movement is stopped and the proximity movement is started. Further, each coordinate value at the time when the proximity movement is stopped is stored in the memory A (step S205), and each coordinate value when the separation movement is stopped is stored in the memory B (step S210). In this case, since the proximity and separation movements are performed at a speed ratio of Vg: Vb = Lg: Lb = 1: 5, the time required for the separation movement is shorter than the time required for the proximity movement on average by 1/5. Thus, contact (short circuit) is eliminated more quickly than in the case of FIG. 2 where Vg = Vb.
[0030]
  In addition, FIG., The present invention described above, VIt is a graph which shows an example of the contact detection operation | movement in case of g> Vb, segment time Ta = 2msec, distance Lg = 5micrometer which moves to the segment time at the time of proximity | contact movement, distance Lb = 1micrometer which moves to the segment time at the time of separation movement The mode of axis movement is shown schematically when contact detection in the X-axis direction is performed while sampling the voltage at an intermediate time point of each segment with a sampling period of 2 msec to determine the contact / non-contact state. .
  This figureIn the case of FIG. 7, the contact detection operation is performed in the same procedure as in FIG. 2, the proximity movement is stopped and the separation movement is started at each time point a, c, e, g, i. At d, f, and h, the separation movement is stopped and the proximity movement is started. Further, each coordinate value at the time when the proximity movement is stopped is stored in the memory A (step S205), and each coordinate value when the separation movement is stopped is stored in the memory B (step S210).
[0031]
  6 is a graph in which the axial movements shown in FIG. 5 are averaged, and FIG. 8 is a graph in which the axial movements shown in FIG. 7 are averaged. The surface of the contact detection target object exists between the average coordinate values Xb of the respective X-axis coordinate values at the time of stopping, and the distance Dm between the average coordinate values Xg and Xb substantially coincides with the average stroke of the axis movement, and is close The motor stop delay time is the same when moving and separating. Up to here, Vg = VbOf the above-mentioned principle technologySame as the case.
  However, since the overshoot amount is proportional to the speed of the axial movement, in the second invention in which Vg ≠ Vb (Lg ≠ Lb), the overshoot amount Dg at the close movement and the overshoot amount at the distant movement. Db is different, and the ratio of the forward overtravel amount Dg and the reverse overtravel amount Db is Lg / Lb, and many portions of the average stroke Dm of the axial movement are excessive for each of the forward and reverse travels. Formed by quantity. Accordingly, the surface position (reference position) of the contact detection target object is biased according to the speed ratio (Lg / Lb) from the midpoint between the Xg point and the Xb point (average stroke Dm). A coordinate point obtained by internally dividing the point distance Dm by the ratio of Lg: Lb can be regarded as a reference position. In the second invention, the internal dividing point is obtained by adding Dm (Lb−Lg) / 2 (Lb + Lg) as the correction amount Rx to the coordinate value of the midpoint of the points Xg and Xb. By adding this correction amount Rx, the error of the deviation corresponding to the speed ratio that occurs when the midpoint between the Xg point and the Xb point is set as the reference position as in the first invention can be eliminated with high accuracy. Can be positioned. In the present invention, the positive / negative direction of the coordinate of the axis movement is defined as the positive direction when the wire electrode approaches the contact detection target.
[0032]
  in this way, This departureAccording to Ming, even when the proximity movement speed Vg and the separation movement 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 (the midpoint between the Xg point and the Xb point) ) And the position of the surface of the contact detection target object can be corrected, and the reference position can be positioned with high accuracy. In addition, the positioning accuracy can be improved by increasing the resolution by setting the axial movement amounts Lg and Lb of the segment time small.
  5 and 6, the case of 5Lg = Lb and the case of Lg = 5Lb in the examples of FIGS. 7 and 8 have been described. However, the speed ratio at the time of forward movement and the backward movement is limited to this. Instead, an appropriate speed ratio such as 10 Lg = Lb, Lg = 10 Lb, or the like is employed.
[0033]
  Figure 9,BookUsing the method of the invention, the error of the value measured by detecting the diameter of a pin gauge of 2.5 mmφ from both sides of the pin gauge with a 0.2 mmφ wire electrode at seven speed ratios A to G shown in FIG. (Measured value -2.5 mm), where ◇ indicates an error when the midpoint of each average coordinate value Xg and Xb is the pin gauge surface position, and □ indicates the midpoint according to the second invention. The error when correcting the error by adding the correction amount Rx is shown. Incidentally, the axis moving speed of 3 mm / min means a speed of moving by 0.1 μm in a segment time of 2 msec. From FIG. 9, when the midpoint of the Xg point and the Xb point is the pin gauge surface position, the error increases as the speed ratio between the forward speed Vg and the reverse speed Vb increases, and is corrected to the midpoint. By adding the amount Rx, it is understood that the error increase tendency due to the increase in the speed ratio at the time of forward and backward movement is eliminated, and the error ratio is substantially constant at any speed ratio of A to G. . Therefore, according to the second aspect of the invention, by adding the correction amount Rx to the midpoint, it is possible to eliminate the error caused by the difference in speed between the forward movement and the backward movement and perform high-accuracy positioning.
[0034]
【The invention's effect】
  As detailed above, the present inventionTo the basic principle technology ofAccording to this, when the moving speed Vg at the time of proximity movement is equal to the moving speed Vb at the time of remote movement, the contact detection operation can be accurately controlled with a small number of voltage samplings, and the reference position can be positioned with high accuracy. it can. And this book using the basic principle technologyAccording to the invention, when the moving speed Vg at the time of proximity movement and the moving speed Vb at the time of remote movement are different, the contact detection operation is accurately controlled with a small number of voltage samplings, and the average coordinate value of the stored coordinate value and the contact The reference position can be positioned with high accuracy by correcting the error with respect to the detection target surface position.
[Brief description of the drawings]
[Figure 1]One of the basic techniques of the present inventionThe flowchart which shows the operation procedure of an example.
[Figure 2]In the same basic technologyThe graph which shows typically the aspect of the axis movement at the time of performing tactile detection.
FIG. 3 is a graph in which the axial movements shown in FIG. 2 are averaged.
[Fig. 4]Main departureThe flowchart which shows the operation procedure of one Example of a clear.
[Figure 5]Same departureThe graph which shows typically the aspect of the axis movement at the time of performing contact detection by light.
6 is a graph obtained by averaging the axial movements shown in FIG.
[Fig. 7]Same departureLightIn different connectionThe graph which shows typically the aspect of the axis movement at the time of performing tactile detection.
FIG. 8 is a graph in which the axial movements shown in FIG. 7 are averaged.
FIG. 9 is a graph showing experimental results.
FIG. 10 is a table showing speed and speed ratio conditions during forward and reverse movements in the graph of FIG. 9;
FIG. 11 is a configuration diagram showing an outline of a wire cut electric discharge machining apparatus.
[Explanation of symbols]
      1 ……………… Bed
      2 ……………… XY Cross Table
      3, 4 ………… X-axis and Y-axis drive motors
      5,6 ………… Rotary encoder
      7 ……………… Loading table
      8 ……………… Workpiece
      9 ……………… Column
      10, 11 …… Upper arm and lower arm
      12, 13 ... A pair of upper and lower machining fluid injection nozzle devices
      14 ………… Wire electrode
      15, 16 ... A pair of upper and lower guides
      17 ……………… Z-axis movement 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 reel
      26, 27 …… Laura
      28 ……………… Wire electrode collection container
      29 …………… Tensile drive mechanism
      30 ……………… Brake mechanism
      31 ……………… Processing power supply
      32 ………………
      33 ………… Computer
      34 ......... NC equipment
      35 ……………… XY axis driver
      36 ……………… UVZ axis driver
      37 ……………… Input device
      38 ……………… Display device
      39 …………… Contact detection device

Claims (1)

A pair of the above-described pair of wire electrodes extending perpendicularly to a processing reference position of a workpiece or a processing table surface on which the workpiece is placed with respect to a wire electrode stretched between a pair of spaced guides. Applying a voltage for contact detection between the wire electrode and the work piece or between the wire electrode and the vertical extraction jig while the wire electrode is moved at a predetermined tension and speed at the vertical reference position of the guide, Wire-cut electrical discharge machining determined by operating a moving mechanism that gives relative proximity movement or separation movement in the X-axis and Y-axis directions between the two and detecting contact / non-contact of both from the voltage level change In the positioning method of the reference position in
The motor for operating the moving mechanism is driven by setting a constant segment time as a unit time and the proximity movement distance moving to the segment time as Lg and a separation movement distance as Lb , and using the segment time as a sampling period. Detecting the voltage to determine whether it is in contact or non-contact;
First, with respect to the X axis, the non-contact state is repeatedly determined for each sampling period during the proximity movement by the forward rotation of the motor, and the proximity movement is continued for the segment time, and the contact state is determined during the proximity movement. When the segment time is over, the motor is stopped and reversely driven to start the separation movement, and the separation movement of the segment time is repeated while the contact state is determined for each sampling period during the separation movement. When the non-contact state is determined at the time of the separation movement, the contact detection operation is performed in a mode in which the motor is stopped at the end of the segment time and the forward movement is started by starting the proximity movement,
The approach movement of the X-axis coordinate value of each time point was stopped and the X-axis coordinate value of each time point of stopping the separation movement respectively divided and stored,
The contact detection operation is terminated by the output of the device that determines the end of the contact detection operation,
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 is calculated, and the coordinate value of the middle point of both calculated average coordinate values In addition, the distance between the two average coordinate values is Dm, and the coordinate value obtained by adding Dm (Lb−Lg) / 2 (Lb + Lg) is used as the X-axis coordinate value of the machining reference position, or the vertical reference position is obtained. X-axis coordinate value used for
Next, the same operation is performed with respect to the Y axis, and the Y axis coordinate value used for obtaining the Y axis coordinate value of the machining reference position or the vertical reference position is obtained.
A method for positioning a reference position in wire-cut electric discharge machining.

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