METHOD OF MACHINING BY ELECTROEROSIVE WIRE-CUT DISCHARGE

Abstract: A machining device by wire-cut discharge which dis­ plays a machinable time (T) based upon a remaining wire electrode (2). The length of a wire when a bobbin (B1) is loaded and a speed for sending the wire are input through a manual input device (7), and are stored in a memory (6). A CPU (5) calculates a new lenght (L) of the remaining wire relying upon the length of wire when it loaded or the length (L) of the remaining wire by them and the speed (V) for sending the wire every after a predetermined period of time during the machining (step S1), and further calculates the machinable time (T) relying upon the newly calculated length (L) of the remaining wire and the speed (V) for sending the wire. The machinable time is displayed on a display (8) (steps S2, S3).

Description: The present invention relates to a wire feed apparatus of a wire-cut electric discharge machine. Conventional wire-cut electric discharge machines include those having a mechanical means for obtaining a remaining amount of a wire electrode (to be referred to as a wire hereinafter), having a wire reel of a special design, and the like. These machines are all complex, high-priced, and inaccurate. A wire-cut electric discharge machine can perform working for a long period of time without need of an operator. However, if the wire cannot complete the current work, working is interrupted, resulting in damage to a work surface or loss of working time. It is an object of the present invention to improve the above drawbacks of the conventional technique and display a workable time or a workable length of a currently used wire by a simple means. According to the present invention there is provided a method of operating a wire-cut electric discharge machine, in which there are automatically displayed data relating to the length remaining from a full length of wire electrode initially mounted on the machine, wherein initially there is input into a memory of a control unit of the machine a parameter or parameters representing the initial full length of said wire electrode; there is also input into the memory a feed speed of said wire electrode; and a processor of the control unit calculates at the ends of successive time periods the length of wire electrode used by the machine, by multiplying the wire feed speed by the time elapsed, and then the length of wire electrode remaining by subtracting the length used from the full initial length, this remaining length of wire electrode being stored in the memory and the processor then going on to calculate the workable time remaining from the remaining wire electrode length and its feed speed, this workable time remaining being displayed. In this manner, when a new wire feed bobbin is mounted on the electric discharge machine, if the wire length is input, a workable time is displayed on a display unit. Therefore, interruption of working caused by depletion of the wire is prevented, so that the work surface is not damaged due to the interruption of working, and loss of working time is prevented. Since the workable time is displayed, automatic operation of the electric discharge machine can be performed easily. Brief Description of Drawings Fig. 1 is a schematic view showing a main part of an electric discharge machine embodying the present invention, in which part thereof is shown in a block diagram; Fig. 2 is a flow chart of the operation of the embodiment shown in Fig. 1; and Fig. 3 is a flow chart of the operation of another embodiment of the present invention. An embodiment of the present invention will be described with reference to the accompanying drawings. In Fig. 1, reference numeral 1 denotes a work to be worked; 2, a wire used for working; R1 and R2, rollers for guiding the wire 2; B1, a wire feed bobbin with unused wire wound therearound; B2, a wire takeup bobbin for taking up used wire; M, a motor for driving the dire takeup bobbin; 3, a motor drive circuit for driving the motor; and 4, a control unit of the electric discharge machine. In the control unit 4, reference numeral 5 denotes a central processing unit (to be referred to as CPU hereinafter) for controlling the entire electric discharge machine, and 6, a memory comprising a ROM storing a program for the overall control, a RAM for temporarily storing data, and a non-volatile memory for storing wire characteristics to be described later. Reference numeral 7 denotes a manual input unit, provided on a control panel or the like of the electric discharge machine, for inputting various preset values and operation commands; 8, a display unit such as a CRT; and 9, an input/output circuit, connected to various detectors or actuators such as a table drive unit of the electric discharge machine to which the work is mounted. Fig. 1 shows only the part of the input/output circuit 9 which is concerned with this embodiment. The input/output circuit 9 is connected to the motor drive circuit 3. Reference numeral 10 denotes a bus. The operation of the electric discharge machine of the embodiment with the above arrangement will now be described with reference to the operation processing flow shown in Fig. 2. First, an unused new wire feed bobbin B1 is mounted and set on the wire-cut electric discharge machine. A length L of the wire wound on the new wire feed bobbin B1 and a wire feed speed V are input at the manual input unit 7 and are stored in the memory 6. When the wire-cut electric discharge machine is started, the motor M is driven to run the wire 2 at the preset wire feed speed V, thereby initiating working. The CPU 5 performs working control and display processing for a workable time (as shown in Fig. 2) at predetermined preset time periods. More specifically, the CPU 5 reads the wire length L and wire feed speed V stored in the memory 6, subtracts, from the wire length L, a value V·t obtained by multiplying a time period t by the wire feed speed V, and stores the result in the memory 6 as a new wire length L (step S1). The new wire length L is divided by the wire feed speed V (step S2) and is stored in the memory 6 as a workable time T, and the workable time T is displayed on the display unit 8 (step S3). The workable time display processing is completed and the flow advances to the next step. The steps S1 to S3 are executed for every predetermined time period t . In other words, the memory 6 stores a current wire length L, and the display unit 8 displays a workable time T which changes after emery time period t . When a work 1 is completed and a next work is to be processed, the length L of unused wire is stored in the memory 6 and the workable time T is displayed on the display unit 8. Therefore, the operator can determine whether the next work can be completed. In the above embodiment, the wire length L itself is input on the manual input unit 7 when a new wire feed bobbin B1 is used. However, this embodiment can be modified such that a total weight W of the bobbin B1 on which an unused wire 2 is wound, the specific weight ρ of the wire 2, the diameter 2r or radius r of the wire, and the weight K of the bobbin B1 are input on the manual input unit 7 instead of the wire length L. Alternatively, specific weights ρ in accordance with the type of wire 2 and the weight K of the bobbin B1 as determined by its specifications can be stored as a table in the non-volatile memory of the memory 6, and the total weight W of the new bobbin B1 on which the wire 2 is wound and the diameter 2r or radius r of the wire 2 can be input from the manual input unit 7. In these modifications, the wire length L is calculated by an operation of the CPU 5 indicated by equation (2) below, in accordance with the various input data, and is stored in the memory 6. More specifically, equation (1), and hence (2) is established between the total bobbin weight W and the input data: W = ρπr²L+K (1) L = (W-K)/ρπr² (2) Generally, the time required for working the work 1 can be predicted from its finished shape. Therefore, if the workable time 7 depending on the length L of unused wire can be obtained in the above manner, only the predicted work time and the workable time T must be compared to determine whether or not the next work can be completed, thereby preventing interruption of working. Fig. 3 shows a process flow of another embodiment of the present invention. This embodiment is different from the above embodiment in that a workable wire length ℓ is displayed in accordance with the following facts. Namely, in this embodiment, the relative speed between a wire 2 being used and a work 1, i.e., a work feed speed V' for feeding a table holding the work 1, is controlled by a control unit 4. Therefore, an average work feed speed V'₀ can be obtained by averaging the work feed speeds V', and the workable wire length ℓ can be calculated from the average work feed speed V'₀ and a workable time T. In Fig. 3, steps S10 and S11 are the same as steps S1 and S2 of Fig. 2. The workable time T of the wire is calculated in steps S10 and S11. A memory 6 stores an actual work feed speed V' for every predetermined time period t , and thus stores speeds V' of 1 to n periods preceding the current period. The sum of the values V'₁,... V' n of respective memory sections of the memory 6 is divided by the number n of the values, thereby obtaining an actual average work feed speed V'₀ for n periods immediately preceding the current period (step S12). The stored values of the memory sections are then sequentially shifted to update the contents thereof. More specifically, a memory section which stored value V n now stores value V' n-1 , a memory section which stored value V' n-1 now stores value V' n-2 '... a memory section which stored value V'₂ now stores value V'₁, and a memory section which stored value V'₁ now stores the current work feed speed V', respectively (steps S13-1 to S13-n). The workable time T obtained in step S11 is multiplied by the average work feed speed V'₀ obtained in step S12, in order to calculate the workable wire length ℓ for the work 1 (step S14). When the workable time T and the workable wire length ℓ obtained in steps S11 and S14 are displayed on the display unit 8, the workable time and wire length display processing is completed, and the flow advances to the next step. In the manner described above, the average value V'₀ of the work feed speed V' is obtained and then the workable wire length ℓ from the current position is displayed. Therefore, when a new work of the same work thickness is to be worked under the same conditions and the average work feed speed V'₀ does not substantially vary, it can be determined from the displayed workable wire length ℓ whether or not the new work can be completed.

Claims: A method of operating a wire-cut electric discharge machine, in which there are automatically displayed data relating to the length remaining from a full length of wire electrode (2) initially mounted on the machine, wherein initially there is input into a memory (6) of a control unit (4) of the machine a parameter or parameters representing the initial full length of said wire electrode (2); there is also input into the memory (6) a feed speed of said wire electrode (2); and a processor (5) of the control unit (4) calculates at the ends of successive time periods (t) the length of wire electrode (2) used by the machine, by multiplying the wire feed speed by the time elapsed, and then the length of wire electrode (2) remaining by subtracting the length used from the full initial length, this remaining length of wire electrode (2) being stored in the memory (6) and the processor (5) then going on to calculate the workable time remaining from the remaining wire electrode length and its feed speed, this workable time remaining being displayed. A method according to claim 1, wherein said parameters representing the initial full length of said wire electrode (2) comprise the total weight (W) of a bobbin (B1) on which said wire electrode (2) is wound, the diameter (2r) of said wire electrode (2), the specific weight (ρ) of said wire electrode (2), and the weight (K) of said bobbin (B1) alone, the length of wire electrode (2) mounted on said bobbin (B1) being calculated from these parameters. A method according to claim 2, wherein there are stored in memory specific weights (ρ) of wire electrodes in accordance with type thereof, and weights (K) of bobbins in accordance with specifications thereof, and the length of the wire electrode (2) when the wire electrode (2) is mounted on said bobbin (B1) is calculated and input from the total weight (W) of said bobbin (B1) on which said wire electrode (2) is wound, the diameter (2r) of said wire electrode (2), the type of said wire electrode (2), and the specifications of said bobbin (B1), which are initially input as parameters representing the initial full length of said wire electrode (2), and from the specific weight (ρ) of said wire electrode (2), and the weight (K) of said bobbin, which are stored in memory as aforesaid. A method according to any preceding claim, comprising calculating an average work feed speed from work feed speeds for the predetermined time periods, workable wire length being calculated from the average work feed speed and the workable time, and the workable wire length also being displayed.

Inventors: ITO, MASAYA, IZUMIYA, SHUNZO, OKUYAMA, YUJI
Applicants: FANUC LTD.
Application year: 1985
Main classification: B23H7
IPC codes: B23H7, B23H3