KR0166125B1 - Method of controlling servos in a wire cut electric spark machine - Google Patents

Abstract

The present invention relates to a servo control method of a wire cut electric discharge machine, by means of an interpolation voltage sensing / distance control unit (60) which detects an interpolation voltage between a wire and a work piece, converts it into a digital, and generates interpolation information by comparing the set reference values. The interpolation information generation process to be performed, the following control process performed by the processing control unit 70 to control the position of the servo by inputting the interpolation information generated during the interpolation control information generation process, and activated by the following control process It is possible to flexibly determine the servo control command by changing the parameter by including a parameter adjusting step of changing the parameter of the inter-pole control information generation process.

Description

Servo control method of wire cut electric discharge machine

1 is a block diagram showing a general wire cut electric discharge machine.

2 is a detailed block diagram of the interpolar voltage sensing / distance control of FIG.

3 is a servo control flowchart of a conventional wire cut electric discharge machine.

4 is a block diagram showing a wire cut electric discharge machine according to the present invention.

5 to 8 are flowcharts showing the servo control operation of the wire cut electric discharge machine according to the present invention.

* Explanation of symbols for main parts of the drawings

10: wire electrode 20: workpiece

30: processing power part 40: processing power control part

50: inter-pole information adjustment unit 60: inter-pole voltage detection / distance control unit

70: processing control part 80: main processing part

90: servo drive unit

TECHNICAL FIELD The present invention relates to a servo control method in a wire cut electric discharge machine. In particular, a servo for controlling the inter-pole distance (hereinafter referred to as a 'machining gap' or simply 'gap') to an optimum machining state regardless of a machining environment is always maintained. It relates to a control method.

In general, a wire cut electric discharge machine applies a pulsed processing voltage between a thin wire electrode having a thickness of 0.05 to 0.3 mm and a workpiece, generates an electrical discharge through a processing liquid, and melts the workpiece by energy at this time. It is an apparatus to process. At this time, the wire electrode maintains a proper gap with the workpiece, thereby achieving stable discharge. The technology for such a wire cut electric discharge machine is disclosed in Korean Patent Publication No. 94-2877 (Notice date: April 6, 1994) and Korean Publication No. 92-6510 (Notification date: August 8, 7, 2012).

1 is a block diagram showing a general wire cut electric discharge machine, the wire electrode 10, the processing power supply unit 30, the processing power control unit 40, the inter-pole voltage sensing / distance control unit 60, the processing control unit 70, It consists of the main processing part 80, the servo drive part 90, etc., and discharge-processes the to-be-processed object 20. FIG. The workpiece 20 is placed on the cross table 96, and the cross table 96 is freely moved in the horizontal plane by the X-axis servo motor 92 and the Y-axis servo motor 94. . Hereinafter, the X-axis and Y-axis servomotors are simply referred to as servos.

Referring to the operation of the electric discharge machine configured as described above, the wire electrode 10 and the workpiece 20 are opposed to each other while injecting the processing liquid processing power supply unit 30 is the wire electrode 10 and the workpiece 20 A pulsed processing voltage is applied between them to cause a discharge between them to make the work piece 20 melted by the energy released to form a fine powder (called a chip), and to remove them while cooling the processing liquid. It is.

At this time, the high frequency pulse generated from the processing power supply unit 30 is variable in magnitude and duty ratio of the voltage according to the control of the processing power control unit 40, the processing power control unit 40 for the pulse control from the processing control unit 70 Receive control information.

The main processor 80 analyzes the machining program, calculates a shape path for the machining, and transmits the shape path to the machining controller 70. In consideration of the servo information input from the distance control unit 60, the processing voltage pulse and the servo are controlled to achieve the optimum processing.

The inter-pole voltage detection / distance control unit 60 detects the inter-pole voltage according to the processing state between the wire electrode 10 and the workpiece 20 and converts the analog voltage to digital, and then, within the inter-pole voltage detection / distance control unit 60. In the one-chip microcomputer implementing the sensed value processor 64, the quantized detection voltage is compared with the set reference voltage to determine the servo track, pause, retreat, and then the process control unit 70. Output

Machining control unit 70 is implemented as a main microprocessor (MAIN CPU) servo drive unit 90 according to the shape control information input from the main processing unit 80 by using the servo information input from the voltage detection / distance control unit 60 between the poles. ), The servo is advanced, retracted, paused, and the processing power control unit 40 is controlled to control the duty ratio and magnitude of the pulse voltage applied between the wire electrode and the workpiece.

Although not shown in detail in the drawings as the wire electrode 10 is a consumable, the wire electrode 10 is collected from the wire winding reel through the lower guide through the upper guide and the workpiece 20.

FIG. 2 is a detailed block diagram of the inter-pole voltage sensing / distance controller of FIG. 1, wherein the inter-pole voltage sensing / distance controller 60 detects the inter-pole voltage between the wire electrode 10 and the workpiece 20 and digitalizes it. The detection unit 62 and the detection value processing unit 64 for comparing the detected inter-pole voltage with a preset reference voltage to determine forward, backward, and pause, and output servo information to the processing control unit 70. At this time, the detection value processor 64 is implemented as a one-chip microcomputer.

The processing control unit 70 includes a servo control unit 100 for position control, which processes the inter-pole information input from the sensed value processing unit 64 according to a predetermined algorithm to control the advance, retreat, and pause of the servo. In addition, through the processing power control unit 40 to control the pulse voltage generated in the processing power supply 30. That is, the inter-pole voltage sensing / distance controller 60 provides the servo information to the machining controller 70 to control the servo driver 90 according to the difference between the average inter-pole voltage and the reference voltage. Meanwhile, the gap GAP between the wire electrode 10 and the workpiece 20 generally ranges from about ten microns to tens of microns.

3 is a flowchart showing a conventional servo control flow by the wire cut electric discharge machine.

Referring to FIG. 3, after initializing the system, the inter-pole voltage detected by the inter-pole voltage sensing / distance controller 60 is read (steps 200 and 210). Next, the read interpolar voltage is compared with a preset reference voltage (step 220). As a result of comparison, if the inter-pole voltage is greater than the forward reference voltage, the forward temporary variable is increased by one (step 230).

Next, the inter-pole voltage read in step 240 is compared with the retreat reference voltage. As a result of comparison, if the interpolar voltage is less than the retreat reference voltage, the retreat temporary variable is increased by one (step 250). Otherwise, in step 260 the pause temporary variable is increased by one.

Next, in step 270, the number of valid detections is decreased by one, and in step 280, it is determined whether the current validity detection count exceeds the preset valid detection number (reference number).

If the current validity detection count exceeds the reference number in step 280, the forward reference number and the forward temporary variable are compared in step 290. If the forward temporal variable is greater than the forward reference number, it is determined as servo advance in step 300. Otherwise, in step 310, the retreat reference number and the retreat temporary variable are compared. As a result of the comparison, if the retreat temporary variable is greater than the retreat reference number, the servo retreat is determined in step 320, and if it is not, the servo pause is determined in step 330.

However, in the case of processing by servo control of the conventional wire cut electric discharge machine, in the case of controlling the servo according to the difference between the inter-pole voltage and the reference voltage due to the processing gap, the forward, retreat and pause of the servo are determined according to the fixed ratio. Therefore, there is a problem in that the lack of flexibility to adapt adaptively depending on the workpiece and processing conditions.

That is, in discharge processing, abnormal discharge is likely to occur due to the accumulation of chips since the flow of the upper and lower processing liquids is offset near the center of the workpiece. If an abnormality occurs in the machining gap, the wire will often retreat to the previous position in the opposite direction of the machining, and repetition of this phenomenon may cause instability in the machining, causing disconnection of the wire if proper servo control is not performed. There is a problem.

Accordingly, an object of the present invention is to provide a servo control method of a wire cut electric discharge machine capable of adjusting inter-pole control information parameters according to processing conditions and processing conditions in order to solve the above problems.

The servo control method of the present invention for achieving the above object is performed by the inter-pole voltage sensing / distance control unit that detects the inter-pole voltage between the wire electrode and the workpiece, converts it to digital, and generates servo information in comparison with the set reference values. The servo information generation process, the following control process performed by the processing controller to control the position of the servo by receiving the servo information generated in the servo information generation process, and activated by the following control process to generate the servo information. A servo control method of a wire cut discharge machine having a parameter adjusting process of changing a parameter of the process, the servo information generating process comprising: a first step of initializing parameters of an inter-pole voltage sensing / distance controller; Reading the detected inter-pole voltage when the set inter-pole voltage disregard time elapses; A third step of comparing the read-out interpolation voltage with the forward reference voltage and increasing the forward temporary variable by one if the interpolar voltage is higher than the reference voltage; A fourth step of comparing the read-out interpolation voltage with the retreat reference voltage and increasing the retreat temporary variable by one if the interpolar voltage is lower than the reference voltage; A fifth step of increasing the temporary temporary variable if the interpolar voltage read is not lower than the retreat reference voltage or higher than the forward reference voltage; A sixth step of repeating the second step to the fifth step if the accumulated count number does not exceed the set reference number after performing the second step to the fifth step and counting the effective detection number once; A seventh step of determining servo advance by comparing the forward reference number with the forward temporary variable value when the count number exceeds the reference number in the sixth step; An eighth step of determining a servo retraction by comparing the retraction reference number with the retreat temporary variable value; And a ninth step of determining servo pause if not servo advance and servo retraction. The tracking control process may include: reading servo information generated in the servo information generation process; Reprocessing the read servo information to generate a servo command; Determining whether the control parameter adjustment variable between poles is 1 when the accumulated number of the servo commands exceeds a set value and activating the parameter adjustment process if it is 1; And outputting a servo position control command according to the servo command, wherein the parameter adjusting process is activated by the following control process to enable forward temporal variable (FORE_PERCENT), backward temporal variable (BACK_PERCENT) and forward reference voltage (FORE_LEVEL). , And the retreat reference voltage BACK_LEVEL.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, the main parameters required for servo control according to the present invention are shown in Table 1 below.

In Table 1, FORE_PERCENT is a parameter indicating the number of times the forward reference voltage is exceeded during the unit time, BACK_PERCENT is a parameter indicating the number of times the retrace reference voltage is exceeded during the unit time, and FORE_LEVEL is a forward reference voltage BACK_LEVEL indicates the retreat reference voltage, SENSING_CNT indicates the total number of detections during the unit time, and EFFECR_CNT indicates the number of effective detections during the unit time. In addition, MAIN_SERVO_CNT is a parameter indicating the accumulated information count of the machining control unit 70, MAIN_FORE_PERCENT represents the number of forward reference set from the machining control unit 70, MAIN_BACK_PERCENT represents the retraction reference number set from the machining control unit 70. In addition, CHANGE_PARA is a parameter indicating whether to adjust the values of FORE_PERCENT, BACK_PERCENT, FORE_LEVEL, and BACK_LEVEL in Clauses 1 to 4 of Table 1, for example, if 1, the parameters of the above 1 to 4 are changed, and if 0, Do not change parameter values.

In the servo control method of the wire cut electric discharge machine according to the present invention, by setting various parameters as shown in Table 1 above, the voltage detected by the inter-pole voltage sensing / distance controller 60 is compared with the set reference voltage, and the result is accumulated in units. The servo is advanced, paused or retracted by the parameters calculated in time.

In other words, in order to solve the instability caused by the chips accumulated in the processing gap, to reduce the amount of chips, the width of the current pulse supplied by the processing power is reduced, the discharge pause width is increased, or the servo is temporarily removed to increase the chip removal capability. It is necessary to increase the flow of the processing liquid by retreating to the stop or the previous position, in the present invention, to improve the removal ability of the chip generated, the distance between the poles is automatically and automatically adjusted constantly regardless of the processing environment such as material and thickness.

In this case, conventionally, the servo control unit 100 of the processing control unit processes the difference between the average processing gap voltage and the reference voltage according to a fixed ratio to determine the advance, pause, retreat, etc. of the servo. As shown in the interstitial information adjusting unit 50 is added to maintain an optimum processing gap without changing various processing environments and processing conditions.

4 is a block diagram showing a wire cut discharge factory value according to the present invention, the wire 10, the processing power supply unit 30, the processing power control unit 40, the interpolation information adjustment unit 50, the interpolation voltage detection / distance control unit 60, the processing control unit 70, the main processing unit 80, the servo drive unit 90 and the like to discharge-process the workpiece 20, the processing control unit of the conventional electric discharge machining apparatus shown in FIG. Between the 70 and the inter-pole voltage sensing / distance controller 60, an inter-pole information adjusting unit 50 for adjusting the inter-pole information parameter is added. Referring to FIG. 4, the same components as those in FIG. 1 are given the same reference numerals, and further description thereof will be omitted. The inter-pole information adjusting unit 50 adjusts the inter-pole information parameter value of the inter-pole voltage sensing / distance control unit 60 by the main processor implementing the machining control unit 70. In fact, the inter-pole information adjusting unit 50 corresponds to the sensed value processing unit 64. It is an interrupt circuit to change the specific register value (ie parameter table value) of one chip microcomputer.

FIG. 5 is a flowchart illustrating a servo control flow of the wire cut discharge machine according to the present invention. The operation of the flowchart of FIG. 5 will be described with reference to Table 1 above.

Referring to FIG. 5, in the initialization step, values for registers and flags are set in order to operate the one-chip microcomputer in the pole voltage sensing / distance controller 60 in a desired mode (step 400). In the temporary variable initialization step, temporary variables for forward, backward, and pause shown in Table 1 are initialized (step 410). Subsequently, the inter-pole voltage sensing / distance controller 60 of FIG. 4 reads and detects and quantizes the inter-pole voltage (ie, processing gap voltage) (step 420).

In step 430, when the inter-pole voltage is compared with the forward reference voltage FORE_LEVEL of Table 1, when the inter-pole voltage exceeds the forward reference voltage value, in step 440, the value of the forward temporary variable FORE_PERCENT is increased by one. When the inter-pole voltage does not exceed the forward reference voltage FOR_LEVEL in operation 430, when the inter-pole voltage value is smaller than the retraction reference voltage BACK_LEVEL in operation 450, in operation 460. The retreat temporary variable BACK_PERCENT is increased by one, and in step 470, the pause variable PAUSE_PERCENT is increased by one.

Subsequently, when the processing for the one time interpolation voltage is completed by performing steps 420 to 470, the number of effective detections (EFFECT_CNT) during the unit time which is the sixth parameter of Table 1 in step 480 is reduced by one. In operation 490, it is determined whether the number of times of processing for the inter-pole voltage exceeds the effective detection frequency EFFECT_CNT. At this time, the effective detection frequency is set to a predetermined value in the initialization step and then decreases by 1 for every processing. Therefore, when the value becomes 0, it can be determined that the effective detection frequency has been exceeded.

If the effective detection frequency (EFFECT_CNT) is not exceeded in operation 490, the voltage detection / distance controller 60 detects the voltage between the poles in step 420 and then reads the voltage between the poles and compares them with a reference value (420 ˜ 480). .

When the number of valid detections (EFFECT_CNT) is exceeded in step 490, the forward temporary variable (FORE_PERCENT) and the forward reference number (MAIN_FORE_PERCENT) are compared in step 500, and when the forward temporary variable value (FORE_PERCENT) is greater than the forward reference number (MAIN_FORE_PERCENT), In step 510, the servo advance TRACK is determined. Otherwise, in step 520, when the retreat temporary variable BACK_PERCENT and the retreat reference number MAIN_BACK_PERCENT are compared, the retreat temporary variable value BACK_PERCENT is greater than the retreat reference number MAIN_BACK_PERCENT. In operation 530, the servo retreat (RETRACK) is determined. Otherwise, the servo pause is determined in operation 540.

6 is an interrupt service routine for adjusting inter-parameters, which is activated when the processing control unit 70 requests an interrupt to reset the parameters, reads the inter-parameter control parameters (step 550), and then adjusts the inter-control parameters. Save (step 560). This interrupt service routine may be generated at any time during the flow of FIG. 5, and if an interrupt occurs, it is restarted from the initialization phase of FIG. 5 after adjusting parameters.

FIG. 7 is a flow chart showing a flow performed by the main microprocessor of the machining control unit in relation to servo tracking, and receives the servo information obtained according to the flow of FIG. 5 without immediately generating a position control command to the servo driver 90. , Retreat the servo information such as retreating only in case of continuous retreat.

Referring to FIG. 7, step 600 reads servo information processed by the one-chip microcomputer of the inter-pole voltage sensing / distance controller 60 according to the flow of FIG. 5 and step 610 accumulates the servo information again. As a processing step, for example, the actual retraction command is output to the servo driver 90 only when retraction of the servo information is three or more times. Next, the servo command information, which is the result of reprocessing, is accumulated to maintain a record of the current machining state, and the cumulative result of a certain number of times is compared with the set value (step 620). In this case, it is determined whether the adjustment variable CHANGE_PARA as shown in 10 of Table 1 is 1 (step 630), and if it is 1, the inter-pole control parameter is corrected according to the flow shown in FIG. 8 (step 640), and then the servo command. (Step 650).

FIG. 8 is a detailed flowchart illustrating the flow of correction of the inter-pole control parameter shown in FIG. 7. When the number of forward reference of the machining control unit 70 is smaller than the number of advances (step 700), the processing controller 70 retreats. If the number is less than the number of retreat criteria (step 710), if it is not small, the adjustment variable is set to 0 so as not to adjust the adjustment variable (step 740). If small, FORE_PERCENT, BACK_PERCENT, FORE_LEVEL, and BACK_LEVEL, which are the parameters of items 1 to 4 of Table 1 above, are modified or FORE_LEVEL and BACK_LEVEL of 3 and 4 of Table 1 are fixed, and FORE_PERCENT and BACK_PERCENT of 1 and 2 are modified (720). In step 730, an external interrupt is generated (step 730) to activate the interrupt service routine of FIG.

As described above, the present invention maintains an optimum processing gap without changing various processing environments and processing conditions by controlling the servo with reference to the inter-parameter values, and prevents processing instability and effectively discharges even under somewhat unreasonable processing conditions. Since the increase and disconnection can be prevented, there is an effect to improve the processing efficiency.

Claims (1)

Servo information generation process performed by the inter-pole voltage sensing / distance control unit 60 which detects the inter-pole voltage between the wire electrode and the workpiece, converts it to digital, and generates servo information by comparing the set reference values with the servo information generation process. A follow-up control process performed by the machining control unit 70 to control the position of the servo by receiving the servo information generated in the step, and a parameter adjusting process that is activated by the following control process to change the parameter of the servo information generation process. In the servo control method of the wire-cut discharge processing machine equipped with the servo information generating process, the step of generating the servo information, the first step of initializing the parameters of the pole voltage detection / distance control unit; Reading the detected inter-pole voltage when the set inter-pole voltage disregard time elapses; A third step of comparing the read-out interpolation voltage with the forward reference voltage and increasing the forward temporary variable by one if the interpolar voltage is higher than the reference voltage; A fourth step of comparing the read-out interpolation voltage with the retreat reference voltage and increasing the retreat temporary variable by one if the interpolar voltage is lower than the reference voltage; A fifth step of increasing the temporary temporary variable if the interpolar voltage read is not lower than the retreat reference voltage or higher than the forward reference voltage; A sixth step of repeating the second step to the fifth step if the accumulated count number does not exceed the set reference number after performing the second step to the fifth step and counting the effective detection number once; A seventh step of determining servo advance by comparing the forward reference number with the forward temporary variable value when the count number exceeds the reference number in the sixth step; An eighth step of determining a servo retraction by comparing the retraction reference number with the retreat temporary variable value; And a ninth step of determining servo pause if not servo advance and servo retraction. The tracking control process may include: reading servo information generated in the servo information generation process; Reprocessing the read servo information to generate a servo command; Determining whether the control parameter adjustment variable between poles is 1 when the accumulated number of the servo commands exceeds a set value and activating the parameter adjustment process if it is 1; And outputting a servo position control command according to the servo command, wherein the parameter adjusting process is activated by the following control process to enable forward temporal variable (FORE_PERCENT), backward temporal variable (BACK_PERCENT), and forward reference voltage (FORE_LEVEL). , And a servo control method for a wire cut electric discharge machine, characterized in that for correcting the retreat reference voltage (BACK_LEVEL).