A system for controlling an electrical discharge machining apparatus wherein the system is rendered responsive to an electrical gap parameter such as gap current or gap voltage level. Included in the system for responding to gap condition is a sensing circuit which includes a light-emissive device connected in circuit with the gap or with other essential operating elements such that there is provided a light output of an intensity proportional to gap current or voltage. A second light responsive device, such as a phototransistor or photo diode, is used to convert the light signal into an electrical control signal, which signal in turn is utilized in a function control for the electrical discharge apparatus. The function control exercised may include machining power pulse on-time and off-time control, interruption of machining power responsive to gap short circuit condition, servo feed by providing relative movement of controllable speed and direction between a tool electrode and the workpiece for regulating the gap width, and interruption of the power for the power supply in order to protect against gap short circuit condition arising from failure of an essential switching element in the EDM power supply such as one of the output electronic switches.

Function control circuit for edm power supply

An electro-erosion process and apparatus for improving the rate of material removal from a workpiece and for decreasing the rate of wear of the electrode tool in an electrical discharge machining apparatus, by controlling the average value of the machining current across the machining gap between the electrode tool and the workpiece by providing cut-off time intervals between consecutive pulse trains at a frequency of at least 200 Hz, and by controllably varying at least one of the parameters of operation consisting of the number of the pulses included within a single pulse train, the duration of application of said pulses within a single pulse train, and at least the longest of the intervals of time comprised between two consecutive voltage pulses.

Process and apparatus for electro-erosion machining by electrical discharges employing variable cut-off time intervals between pulse trains and/or pulse trains of variable durations

A power-supply control device includes a high-frequency component detecting unit, a machining voltage level detecting device, and a pulse control device. The high-frequency component detecting unit detects a high-frequency component of discharge voltage at a machining gap. The machining voltage level detecting device detects a discharge voltage level at the machining gap. The high-frequency component is compared with a reference high-frequency component to obtain a first comparison result. The discharge voltage level is compared with a reference voltage level to obtain a second comparison result. The pulse control device controls pulse off time based on the first comparison result, and cuts off a discharge pulse based on the second comparison result.

Power supply-control device for electrical discharge machining apparatus

A method and apparatus for shaping a workpiece by electrical discharge, the workpiece being shaped by a shaping electrode by intermittently impressing a voltage pulse across a working gap formed between the workpiece and the shaping electrode. The apparatus comprises a means for efficiently controlling the duration of a discharge across the working gap according to a condition dependent upon a no-load voltage impressing period, i.e., the period of operation beginning with the impression of the voltage pulse and ending with the occurrence of a discharge, and further according to the state of the working gap detected in terms of a processing voltage mean value. When a no-load voltage impressing period is inside a given interval, the duration of a discharge is increased according to the length of the period. Alternatively, when the no-load voltage impressing period is outside the given interval, the duration of a discharge corresponding to the state of the working gap is not increased. Accordingly, operating stability is improved and electrode consumption is minimized.

Method and apparatus for electrical discharge machining

A process and apparatus for controlling an electric discharge machine consisting of applying a pulse voltage across a working gap when the predetermined time of interruption of the electric discharge has lapsed and when the interpolar voltage has exceeded a reference voltage, increasing the reference voltage and lengthening the time of interruption of the electric discharge when the rate of abnormal discharge occurrence becomes greater than an allowable rate and decreasing the reference voltage and reducing the time of interruption of the electric discharge when the rate of abnormal electric discharge occurrence is less than an allowable rate.

Method and apparatus for controlling an electric discharge machine

A protection circuit is provided which senses and responds to gap short circuit condition during machining pulse on-time. Responsive to such condition, a machining current cut-off function is exercised by a complementary pair of electronic switches which operate with positive action to control pulser operation by decreasing the "on" time of the pulser and decreasing off-time. An additional means is provided for appropriate limiting machining current by sensing gap open circuit condition during pulse on-time and correspondingly, through the operation of a complementary pair of electronic switches, increasing the "off" time of the pulser.

Verner Dalton R

Papers

Pulse narrowing and cut-off protection system for electrical discharge machining