NC electroerosion method and apparatus

Claim 2

An electroerosion method of machining an electrically conductive workpiece with a tool electrode, the method comprising the steps of: (a) effecting a succession of electrical discharges across an electrical discharge machining (EDM) gap between the tool electrode and the workpiece to electroerosively remove material from the workpiece while consecutively advancing the tool electrode relatively into the workpiece under numerical commands from a numerical controller whose commands in a set numerically prescribe a desired path and extent of the relative advancement; (b) maintaining electrical parameters of said discharges in a given EDM mode during an initial period of the numerically commanded consecutive advancement of the tool electrode relative to the workpiece; (c) sensing, by means of said numerical controller, arrival of the tool electrode at a predetermined position in said path relative to the workpiece spaced by a preselected distance from its final position determined by said numerically prescribed extent of the consecutive relative advancement to provide a signal; and (d) in response to said signal, switching the electrical parameters of said discharges into another EDM mode, and maintaining said switched parameters until said tool electrode reaches said final position relative to said workpiece established in said numerical controller.

Claim 3

The method defined in claim 1 wherein in step (c), said parameters of electrical discharges are switched in response to the NC commands representing said arrival.

Claim 4

The method defined in claim 1 or claim 2 wherein said given mode is a roughing EDM mode and said another mode is a finishing EDM mode.

Claim 5

The method defined in claim 3, further comprising switching said parameters to establish a medium EDM mode upon arrival of the tool electrode at a predetermined position spaced by a preselected distance from the first-mentioned predetermined position relative to the workpiece and maintaining the established EDM mode until said tool electrode reaches said first-mentioned predetermined position relative to the workpiece.

Claim 6

The method defined in claim 1, further comprising changing said parameters to progressively establish successive EDM modes from the first-mentioned EDM mode to the second-mentioned EDM mode as a function of the relative position of the tool electrode to the workpiece intermediate between said initial period and arrival of the tool electrode at said predetermined position during said consecutive relative advancement.

Claim 7

The method defined in claim 1 or claim 5 wherein said parameters include at least one of the pulse interval between successive electrical discharges and the pulse duration and peak current thereof.

Claim 8

The method defined in claim 1 or claim 5 wherein said succession of electrical discharges is applied in the form of a succession of time-spaced or intermittently occurring trains of discharge pulses and said parameters include at least one of the peak current and duration of the discharge pulses, the time intervals between said successive trains and the duration of the trains.

Claim 9

The method defined in claim 1 wherein said set of NC commands is programmed to execute said consecutive relative advancement between the tool electrode and the workpiece along a predetermined orbital path extending transversely to the axis of the tool electrode.

Claim 10

A numerically controlled (NC) electroerosion apparatus for machining an electrically conductive workpiece with a tool electrode, the apparatus comprising: power supply means for effecting a succession of electrical discharges across an EDM gap between the tool electrode and the workpiece to electroerosively remove material from the workpiece; NC drive means for consecutively advancing the tool electrode relatively into said workpiece under numerical commands from a numerical controller as said material removal proceeds, said commands in a set numerically prescribing a desired path and extent of the relative advancement; control means associated with said numerical controller and said power supply means for maintaining electrical parameters of said discharges in a given EDM mode during an initial period of the consecutive advancement of the tool electrode relative to the workpiece; means in said numerical controller responsive to arrival of the tool electrode at a predetermined position in said path relative to the workpiece spaced by a preselected distance from its final position determined by said numerically prescribed extent of the consecutive relative advancement for switching the parameters of the electrical discharges into another EDM mode and maintaining the switched parameters until the tool electrode reaches said final position relative to said workpiece established in said numerical controller.

Claim 11

A numerically controlled (NC) electroerosion apparatus for machining an electrically conductive workpiece with a tool electrode, the apparatus comprising: power supply means for effecting a succession of electrical discharges across an EDM gap between the tool electrode and the workpiece to electroerosively remove material from the workpiece; NC drive means for consecutively advancing the tool electrode relatively into said workpiece under numerical commands from a numerical controller as said material removal proceeds, said commands in a set numerically prescribing a desired path and extent of the relative advancement; control means associated with said numerical controller and said power supply means for maintaining electrical parameters of said discharges in a given EDM mode during an initial period of the consecutive advancement of the tool electrode relative to the workpiece; means in said numerical controller responsive to arrival of the tool electrode at a predetermined position in said path relative to the workpiece spaced by a preselected distance from its final position determined by said numerically prescribed extent of the consecutive relative advancement for switching the parameters of the electrical discharges into another EDM mode and maintaining the switched parameters until the tool electrode reaches said final position relative to said workpiece established in said numerical controller.

Claim 12

The apparatus defined in claim 9 wherein the last-mentioned means is associated with said NC drive means to respond to the NC commands representing said arrival.