Patent Publication Number: US-2021178500-A1

Title: Control device and recording medium encoded with program

Description:
This application is based on and claims the benefit of priority from Japanese Patent Application 2019-225253, filed on 13 Dec. 2019, the content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a control device and a recording medium encoded with a program. 
     Related Art 
     Conventionally, a wire electrical discharge machine has been known which machines a workpiece by generating an electrical discharge at the electrode gap between a wire electrode and a workpiece. With the wire electrical discharge machine, the relative position of the wire electrode and workpiece is changed by operation of a servomotor, at the same time as the generation of electrical discharge. The wire electrical discharge machine can thereby machine the workpiece into a desired shape. 
     Upon machining of a workpiece, positioning of the wire electrode and workpiece is conducted. As a device which conducts such positioning of the wire electrode and workpiece, a contact detection apparatus for the wire electrical discharge machine has been proposed which conducts positioning by detecting contact between the wire electrode and workpiece, for example (refer to Patent Document 1). 
     Patent Document 1: Japanese Unexamined Patent Application, Publication. No. 2013-226612 
     SUMMARY OF THE INVENTION 
     In Patent Document 1, a detection voltage is applied to the electrode gap of the wire electrode and workpiece. In addition, in Patent Document 1, contact is decided based on a change in detection voltage due to contact between the wire electrode and workpiece. The relative position (end surface of workpiece) between the wire electrode and workpiece is thereby detected. Then, with Patent Document 1, the machining of the workpiece is started with the detected position as a reference position. 
     However, since the wire electrode slightly oscillates, the electrical discharge occurs in response to the oscillation at the electrode gap when the wire electrode approaches the workpiece. The ware electrode receives the repulsive force from the electrical discharge and comes to oscillate more greatly. By the oscillations becoming greater, the number of times of electrical discharge occurring at the electrode gap between the wire electrode and workpiece increases. As a result thereof, since the craters in the workpiece surface increase, the detection precision has deteriorated. Therefore, it is ideal if able to improve the contact detection precision between the wire electrode and workpiece, since the precision of the relative position between the wire electrode and workpiece can be improved. 
     A first aspect of the present disclosure relates to a control device which controls a wire electrical discharge machine having a movement drive unit causing a wire electrode and a workpiece to relatively move, the control device measuring a relative position of the wire electrode and the workpiece by detecting contact between the wire electrode and the workpiece which had been made to relatively move, the control device including: a cycle setting unit which sets a pulse cycle of a detection voltage applied to an electrode gap between the wire electrode and the workpiece; a voltage application unit which applies the detection voltage to the electrode gap at a set cycle; a movement speed control unit which controls relative movement speed by way of the movement drive unit; and a contact detection unit which detects contact between the wire electrode and the workpiece, based on a change in the detection voltage applied; in which the contact detection unit, after executing a first detection operation of contact between the wire electrode and the workpiece at a first relative movement speed and a first pulse cycle, executes a second detection operation of contact between the wire electrode and the workpiece, at a second relative movement speed which is slower than the first relative movement speed, and at a second pulse cycle which is longer than the first pulse cycle, and the movement speed control unit, after execution of the first detection operation, and prior to execution of the second detection operation, causes the wire electrode and the workpiece to relatively move in a distancing direction. 
     In addition, a second aspect of the present disclosure relates to a recording medium encoded with a program which causes a computer to function as control device which controls a wire electrical discharge machine having a movement drive unit causing a wire electrode and a workpiece to relatively move, the control device measuring a relative position of the wire electrode and the workpiece by detecting contact between the wire electrode and the workpiece which had been made to relatively move, the program causing the computer to function as: a cycle setting unit which sets a pulse cycle of a detection voltage applied to an electrode gap between the wire electrode and the workpiece; a voltage application unit which applies the detection voltage to the electrode gap at a set cycle; a movement speed control unit which controls relative movement speed by way of the movement drive unit; and a contact detection unit which detects contact between the wire electrode and the workpiece, based on a change in the detection voltage applied; in which the contact detection unit, after executing a first detection operation of contact between the wire electrode and the workpiece at a first relative movement speed and a first pulse cycle, executes a second detection operation of contact between the wire electrode and the workpiece, at a second relative movement speed which is slower than the first relative movement speed, and at a second pulse cycle which is longer than the first pulse cycle, and the movement speed control unit, after execution of the first detection operation, and prior to execution of the second detection operation, causes the wire electrode and the workpiece to relatively move in a distancing direction. 
     According to the present disclosure, it is possible to provide a control device and a recording medium encoded with a program which can improve measurement precision of a relative position of a wire electrode and a workpiece, by improving the contact detection precision between the wire electrode and the workpiece. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a control device according to an embodiment of the present disclosure; and 
         FIG. 2  is a schematic diagram showing an outline of detecting contact by way of the control device of the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, a control device  1  and program according to an embodiment of the present disclosure will be explained by referencing  FIGS. 1 and 2 . First, before explaining the control device  1  and program of the embodiment, a wire electrical discharge machine  100  controlled by the control device  1  will be explained. 
     The wire electrical discharge machine  100 , for example, is a device which machines a workpiece  102  by applying a working voltage at the electrode gap between a wire electrode  101  and workpiece  102 , as shown in  FIG. 1 . The wire electrical discharge machine  100  has a movement drive unit  103  which causes the wire electrode  101  and workpiece  102  to relatively move. The movement drive unit  103  is configured by a plurality of servomotors (not shown) arranged on the respective axes of the wire electrode  101  and workpiece  102 , for example. The movement drive unit  103  machines the workpiece  102  to a predetermined shape by causing the wire electrode  101  and workpiece  102  to relatively move. The movement drive unit  103 , for example, relatively moves the wire electrode  101  and workpiece  102 , by causing an electrically-conductive table  104  on which the workpiece  102  is placed, and the wire electrode  101  to move. It should be noted that, in order to simplify explanation in the following embodiment, an example in which the movement drive unit  103  moves the wire electrode  101  relative to the workpiece  102  will be explained. 
     Next, measurement of the relative position between the wire electrode  101  and workpiece  102  in the wire electrical discharge machine  100  will be explained. In the wire electrical discharge machine  100 , upon starting machining of the workpiece  102 , measurement of the relative position between the wire electrode  101  and workpiece  102  is conducted. In the measurement of the relative position, first, a pulse-like detection voltage of a level lower than the working voltage is applied at the electrode gap between the wire electrode  101  and workpiece  102 . Then, the wire electrode  101  and workpiece  102  are relatively moved in an approaching direction. A change in the detection voltage is detected by the wire electrode  101  and workpiece  102  making contact. It is thereby possible to measure the positions of the wire electrode  101  and workpiece  102 . Then, the wire electrical discharge machine  100  can machine the workpiece  102  to a predetermined shape, with the measured position as a reference position. 
     Next, the control device  1  and program according to the first embodiment of the present disclosure will be explained by referencing  FIGS. 1 and 2 . The control device  1  is a device which controls the wire electrical discharge machine  100 . The control device  1  measures the relative position between the wire electrode  101  and workpiece  102 , by detecting contact between the wire electrode  101  and workpiece  102  which were made to relatively move. In the present embodiment, the control device  1  detects twice in the order of a first detection operation and a second detection operation the contact between the wire electrode  101  and workpiece  102 . The control device  1  includes a cycle setting unit  11 , a voltage application unit  12 , a movement speed control unit  13 , and a contact detection unit  14 , as shown in  FIG. 1 . 
     The cycle setting unit  11 , for example, is realized by a CPU operating. The cycle setting unit  11  sets a pulse cycle of the detection voltage applied at the electrode gap between the wire electrode  101  and workpiece  102 . The cycle setting unit  11  can change the pulse cycle of the detection voltage, based on the pulse frequency inputted from the outside, for example. In the present embodiment, the cycle setting unit  11 , as shown in  FIG. 2 , sets different pulse cycles, at the first detection operation (act 1 ) and the second detection operation (act 3 ). More specifically, the cycle setting unit  11  sets the second pulse cycle T 2  in the second detection operation to be longer than the first pulse cycle T 1  set in the first detection operation. The cycle setting unit  11  sets the second pulse cycle T 2  set in the second detection operation to 1.5 times or more than the first pulse cycle T 1  set in the first detection operation, for example. 
     The voltage application unit  12 , for example, is realized by a CPU controlling a power source (not shown) that applies the detection voltage. The voltage application unit  12  applies the detection voltage to the electrode gap at the set cycle. The voltage application unit  12 , for example, applies the detection voltage of the pulse cycle set by the cycle setting unit  11  at the electrode gap. The voltage application unit  12 , for example, applies the detection voltage of the first pulse cycle T 1  in the first detection application to the electrode gap between the wire electrode  101  and workpiece  102 , as shown in  FIG. 2 . In addition, the voltage application unit  12  applies the detection voltage of the second pulse cycle T 2  in the second detection operation to the electrode gap between. the wire electrode  101  and workpiece  102 . 
     The movement speed control unit  13 , for example, is realized by a CPU operating. The movement speed control unit  13  controls the relative movement speed by the movement drive unit  103 . The movement speed control unit  13 , for example, controls the relative movement speed between the wire electrode  101  and workpiece  102  (table  104 ). In addition, the movement speed control unit  13  can change the relative movement speed based on the relative movement speed inputted from outside, for example. In the present embodiment, the movement speed control unit  13  controls different relative movement speeds in the first detection operation and the second detection operation. More specifically, the movement speed control unit  13  controls the second relative movement speed V 2  in the second detection operation to be slower than the first relative movement speed V 1  in the first detection operation. In addition, the movement speed control unit  13 , after execution of the first detection operation, causes the wire electrode  101  and workpiece  102  to relatively move (act 2  in  FIG. 2 ), before execution of the second detection operation. 
     The contact detection unit  14 , for example, is realized by a CPU controlling a sensor (not shown). The contact detection unit  14  detects contact between the wire electrode  101  and workpiece  102 , based on a change in the applied detection voltage. The contact detection unit  14 , for example, detects the contact between the wire electrode  101  and workpiece  102 , by detecting the disappearance of the peak voltage. In addition, the contact detection unit  14  measures the positions of the wire electrode  101  and the position of the workpiece  102 , by detecting the contact. In the present embodiment, the contact detection unit  14 , after executing the first detection operation of contact between the wire electrode  101  and workpiece  102  at the first relative movement speed V 1  and first pulse cycle T 1 , executes the second detection operation of contact between the wire electrode  101  and workpiece  102 , at the second relative movement speed V 2  which is slower than the first relative movement speed V 1 , and at the second pulse cycle T 2  which is longer than the first pulse cycle T 1 . 
     Next, operation of the control device  1  according to the present embodiment will be explained using  FIG. 2 . First, the cycle setting unit  11  sets the first pulse cycle T 1  upon executing the first detection operation. Next, the movement speed control unit  13  sets the first relative movement speed V 1 . 
     Then, the voltage application unit  12  applies the detection voltage set in the first pulse cycle T 1  to the electrode gap between the wire electrode  101  and workpiece  102 . Next, the movement speed control unit  13  causes the wire electrode  101  to move (relatively move) in the approaching direction at the first relative movement speed V 1 , in relation to an end surface S of the workpiece  102 . 
     Then, the contact detection unit  14  detects contact between the wire electrode  101  and the workpiece  102 . The contact detection unit  14  measures the relative position between the wire electrode  101  and workpiece  102 . The first detection operation thereby ends. Next, the movement speed control unit  13  moves (relatively moves) the wire electrode  101  in a direction distancing from the workpiece  102 . The movement speed control unit  13  distances the wire electrode  101  from the workpiece  102  at a shorter distance than a relative movement distance of the wire electrode  101  and workpiece  102  in the first detection operation, for example. 
     Next, the cycle setting unit  11  sets the second pulse cycle T 2 , upon executing the second detection operation. Then, the movement speed control unit  13  sets the second relative movement speed V 2 . 
     Next, the voltage application unit  12  applies the detection. voltage set in. the second pulse cycle T 2  to the electrode gap between the wire electrode  101  and workpiece  102 . Then, the movement speed control unit  13  causes the wire electrode  101  to move (relatively move) in the approaching direction at the second relative movement speed V 2 , to one end surface S of the workpiece  102 . 
     Next, the contact detection unit  14  detects contact between the wire electrode  101  and workpiece  102 . The contact detection unit  14  measures the relative position of the wire electrode  101  and workpiece  102 . The second detection operation thereby ends. 
     Next, a program of the present embodiment will be explained. Each configuration included in the control device  1  can be respectively realized by hardware, software or a combination of these. Herein, being realized by software indicates the matter of being realized by a computer reading and executing a program. 
     The program can be stored using various types of non-transitory computer readable media, and supplies to the computer. Non-transitory computer readable medium includes various types of tangible storage media. Examples of non-transitory computer readable media include magnetic recording media (e.g., flexible disk, magnetic tape, hard disk drive), magneto-optical recording media (e.g., magneto-optical disk), CD-ROM (Read Only Memory), CD-R, CD-R/W and semiconductor memory (e.g., mask ROM, PROM (programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (random access memory)). In addition, the display program may be supplied to the computer by way of various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals and electromagnetic waves. Transitory computer readable media can supply programs to the computer via wired communication paths such as electric wires and optical fiber, or wireless communication paths. 
     According to the control device  1  and program of the first embodiment above, the following effects are exerted. (1) In the control device  1  which controls the wire electrical discharge machine  100  having a movement drive unit  103  that causes the wire electrode  101  and workpiece  102  to relatively move, the control device  1  measuring the relative position of the wire electrode  101  and workpiece  102  by detecting contact between the wire electrode  101  and workpiece  102  which have been relatively moved includes: the cycle setting unit  11  which sets the pulse cycle of the detection voltage applied to the electrode gap between the wire electrode  101  and workpiece  102 ; the voltage application unit  12  which applies the detection voltage to the electrode gap at the set cycle; the movement speed control unit  13  which controls the relative movement speed by the movement drive unit  103 ; and the contact detection unit  14  which detects contact between the wire electrode  101  and workpiece  102 , based on the change in the applied detection voltage; in which the contact detection unit  14  executes the second detection operation of contact between the wire electrode  101  and workpiece  102  at the second relative movement speed V 2  which is slower than the first relative movement speed V 1 , and at the second pulse cycle T 2  which is longer than the first pulse cycle T 1 , after executing the first detection operation of contact between the wire electrode  101  and workpiece  102  at the first relative movement speed V 1  and first pulse cycle T 1 , and the movement speed control unit  13  causes the wire electrode  101  and workpiece  102  to relatively move in a distancing direction after execution of the first detection operation and before execution of the second detection operation. 
     In addition, in a program which causes a computer to function as the control device  1  which controls the wire electrical discharge machine  100  having a movement drive unit  103  that causes the wire electrode  101  and workpiece  102  to relative move, the control device  1  measuring the relative position of the wire electrode  101  and workpiece  102  by detecting contact between the wire electrode  101  and workpiece  102  which have been relatively moved, the program causes the computer to function as: the cycle setting unit  11  which sets the pulse cycle of the detection voltage applied to the electrode gap between the wire electrode  101  and workpiece  102 ; the voltage application unit  12  which applies the detection voltage to the electrode gap at the set cycle; the movement speed control unit  13  which controls the relative movement speed by the movement drive unit  103 ; and the contact detection unit  14  which detects contact between the wire electrode  101  and workpiece  102 , based on the change in the applied detection voltage; in which the contact detection unit  14  executes the second detection operation of contact between the wire electrode  101  and workpiece  102  at the second relative movement speed V 2  which is slower than the first relative movement speed V 1 , and at the second pulse cycle T 2  which is longer than the first pulse cycle T 1 , after executing the first detection operation of contact between the wire electrode  101  and workpiece  102  at the first relative movement speed V 1  and first pulse cycle T 1 , and the movement speed control unit  13  causes the wire electrode  101  and workpiece  102  to relatively move in a distancing direction after execution of the first detection operation and before execution of the second detection operation. 
     It is thereby possible to preliminarily measure the relative position of the wire electrode  101  and one end surface S of the workpiece  102 , at the first pulse cycle T 1  and first relative movement speed V 1  in the first detection operation. Then, in the second detection operation, it is possible to suppress the occurrence of craters in the workpiece  102 , by measuring the relative position of the wire electrode  101  and one end surface S of the workpiece  102  at the second pulse cycle T 2  and second relative movement speed V 2 . In addition, it is possible to suppress the influence of deflection of the wire electrode  101 , by using the detection voltage of the second pulse cycle T 2 . Therefore, by improving the contact detection precision between the wire electrode  101  and workpiece  102 , it is possible to improve the measurement precision of the relative position of the wire electrode  101  and workpiece  102 . 
     Although each preferred embodiment of the control device and program of the present disclosure have been explained above, the present disclosure is not to be limited to the aforementioned embodiments, and modifications thereof are possible where appropriate. For example, in the above embodiments, an example using the first and second detection operations is explained; however, it is not limited thereto. For example, measurement may be executed using three or more detection operations. In this case, detection operations executed later are executed with a longer pulse cycle and slower relative movement speed. 
     In addition, in the above embodiments, an example moving the wire electrode  101  relative to the workpiece  102  is explained; however, it is not limited thereto. Both the workpiece  102  and wire electrode  101  may be configured to move relatively. It may be a mode in. which the workpiece  102  moves and the wire electrode  101  does not move. 
     In addition, in the first detection operation, the first pulse cycle T 1  and/or first relative movement speed V 1  may not be constant. In the second detection operation, the second pulse cycle T 2  and/or second relative movement speed V 2  may not be constant. 
     In addition, in the above embodiments, the contact detection unit  14  is configured to execute the first detection operation and the second detection operation; however, it is not limited thereto. As another embodiment, the contact detection unit  14  executes the detection operation two or more times, and in any of the detection operations of the second time and later, contact between the wire electrode  101  and the workpiece is detected more slowly than the relative movement speed of the wire electrode  101  and workpiece  102 , and at a pulse cycle longer than the pulse cycle in the detection operations prior to these. By configuring in this way, it is possible to improve the measurement precision of the relative position of the wire electrode  101  and workpiece  102 . 
     In addition, as another embodiment, the contact detection unit  14  may execute the detection operation a plurality of times by slowing the relative movement of the wire electrode  101  and workpiece  102 , and lengthening the pulse cycle, in every detection operation. It is thereby possible to further improve the position detection precision of one end surface S of the workpiece  102 . In addition, the movement speed control unit  13  causes the wire electrode  101  and workpiece  102  to relatively move in the distancing direction every time during the detection operation. At this time, it may be configured so that the movement speed control unit  13  shortens the distance by which distancing the wire electrode  101  and workpiece  102  every time the number of the detection operation advances. It is thereby possible to suppress an increase in the time required for the overall detection operation, even if the relative movement speed bringing the wire electrode  101  and workpiece  102  into contact becomes slower every time the number of the detection operation advances. 
     EXPLANATION OF REFERENCE NUMERALS 
     
         
           1  control device 
           11  cycle setting unit 
           12  voltage application unit 
           13  movement speed control unit 
           14  contact detection unit 
           100  wire electrical discharge machine 
           101  wire electrode 
           102  workpiece 
           103  movement drive unit 
         T 1  first pulse cycle 
         T 2  second pulse cycle 
         V 1  first relative movement speed 
         V 2  second relative movement speed