Device for electrical discharge machining, comprises workpiece holder, electrode, programmed storage device for required shape and machining conditions, and electrode feed with special wear-compensation system

摘要

A device for electrical discharge machining, has an electrode-advance system programmed to produce the required machined shape and compensate for electrode wear. A device for electrical discharge machining, comprising (a) a holder (3) for the workpiece (2); (b) a machining electrode (1) with a simple shape; (c) a power supply (8); (d) a storage device for storing the required final shape and the machining conditions, plus an NC machining program for advancing (1) relative to (2) along a movement path (P) in the X-Y plane; (e) a feeder (5, 6) for advancing the electrode (1) as in (d); (f) an electrode-wear corrector (11) for gradually advancing the electrode (1) in the Z-direction at right angles to X-Y, with a control unit (10; 30; 63) for (f1) controlling the feeder (5, 6) to move the electrode according to the program in successive steps each corresponding to a correction reference value (delta L) until the end of the movement, (f2) stopping the electrode (1) after a step corresponding to delta L and (f3) lowering (1) in the Z-direction towards the workpiece (2) by a correction adjustment value (delta Zu) after stopping the advance along path P by a step corresponding to delta L, where (f4) the control unit includes a repeat-number control device (22) which, with the aid of a machining depth (E) and a rate of movement in the Z-direction (delta Z), determines how often a tool path has to be cut along path P; (g) a device (23) for measuring the machining depth during or after repeats, the control unit (10; 30; 63) being designed to change at least one of the following parameters if the measured value varies too much from an acceptable value: (g1) remaining number of repeats (N), (g2) Z-axis correction adjustment value (delta Zu), (g3) a value (~Lu) equivalent to the x-y movement distance in the X-Y plane corresponding to delta Zu and (g4) electrical conditions for controlling electrode wear; and (h) a device for adjusting delta L and delta Zu in parallel and in accordance with the stored machining conditions. An independent claim is included for a method for electrical discharge machining by holding a workpiece and machining it with a controlled moving electrode as described above.