Method and apparatus for discharge machining polygonal contours

A discharge machining method of machining a workpiece by applying electric current to said workpiece and an electrode having a polygonal contour through a machining solution in the interelectrode space between said workpiece and said electrode comprising the steps of:

• displacing said electrode and said workpiece relative to each other in a plane with the direction of movement of said electrode and said workpiece in said plane being substantially perpendicular to a primary machining direction, relative displacement of said workpiece and said electrode being such that a geometric center of said electrode moves along straight lines extending through a geometric center of an area to be machined and intersections of straight lines defining boundaries of said area to be machined such that, during movement along each said straight line extending through said geometric center of said area to be machined and one of said intersections, the two straight lines on said workpiece which form said one of said intersections are maintained parallel to respective two corresponding sides of said electrode, and gap widths between each of said two straight lines on said workpiece and said respective corresponding sides of said electrodes are substantially the same throughout said movement;
• and
• performing discharge machining by controlling said electrode and said workpiece in such a manner that an interelectrode space is maintained between said electrode and said workpiece to an extent that electric discharge occurs in said interelectrode space.

A discharge machining method for machining a workpiece by applying electric current to said workpiece and an electrode having a polygonal contour through a machining solution in the interelectrode space between said workpiece and said electrode comprising the steps of:

• displacing said electrode and said workpiece relative to each other in a plane with the direction of movement of said electrode and said workpiece in said plane being substantially perpendicular to a primary machining direction, relative displacement of said workpiece and said electrode being such that a geometric center of said electrode moves along straight lines extending through a geometric center of an area to be machined and final displacement points at intersections of straight lines defining boundaries of said area to be machined such that, during movement along each said straight line extending through said geometric center of said area to be machined and one of said intersections, the two straight lines on said workpiece which form said one of said intersections are maintained parallel to respective two corresponding sides of said electrode, and gap widths between each of said two straight lines on said workpiece and said respective corresponding sides of said electrode are substantially the same throughout said movement, and each mvement along each of said straight lines extending through said geometric center of said area to be machined and one of said intersections being decreased in length from the previous movement along the same line;
• performing discharge machining by controlling said electrode and said workpiece in such a manner that an interelectrode space is maintained between said electrode and said workpiece to an extent that electric discharge occurs in said interelectrode space.

A discharge machining apparatus for machining a workpiece by applying electric current to said workpiece and an electrode through a machining solution in the interelectrode space between said workpiece and said electrode comprising:

• first driving means for determining whether discharge machining is acceptable in a primary machining direction and if so for moving said electrode relative to said workpiece with a predetermined machining space being maintained between said electrode and said workpiece;
• second driving means for moving said electrode relative to said workpiece in a direction substantially perpendicular to said primary machining direction;
• a numerical control device for providing instruction signals to control an amount of relative movement of said electrode driven by said second driving means;
• timer means, said numerical control device operating in response to said timer means to provide instruction signals for displacement vectors every predetermined period of time;
• detection means for detecting an interelectrode voltage between said electrode and said workpiece to output a pulse signal having a frequency which corresponds to said interelectrode voltage thus detected;
• and
• means for outputting, when the number of pulses outputted by said detection mechanism reaches a predetermined value, a drive signal for a displacement vector provided by said numerical control device to drive said second driving device.

A discharge machining method for machining a workpiece by applying electric current to said workpiece and an electrode through a machining solution in the interelectrode space between said workpiece and said electrode comprising the steps of:

• displacing said electrode and said workpiece relative to each other in a plane with the direction of movement of said electrode and said workpiece in said plane being substantially perpendicular to a primary machining direction;
• performing discharge machining by controlling said electrode and said workpiece in such a manner that an interelectrode space is maintained between said electrode and said workpiece to an extent that electric discharge occurs in said interelectrode space;
• controlling said relative displacement of said workpiece and said electrode such that a geometric center of said electrode moves along straight lines extending through a geometric center of an area to be machined and intersections of straight lines defining boundaries of said area to be machined such that, during movement along each said straight line extending through said geometric center of said area to be machined and one of said intersections, the two straight lines on said workpiece which form said one of said intersections are maintained parallel to respective two corresponding sides of said electrode, and gap widths between each of said two straight lines on said workpiece and said respective corresponding sides of said electrode are substantially the same throughout said movement;
• and
• superposing a predetermined minute displacement motion on said relative displacement to an extent that machining accuracy is not affected by said superposition.

A discharge machining method for machining a workpiece by applying electric current to said workpiece and an electrode through a machining solution in the interelectrode space between said workpiece and said electrode comprising the steps of:

• displacing said electrode and said workpiece relative to each other in a plane with the direction of movement of said electrode and said workpiece in said plane being substantially perpendicular to a primary machining direction, relative displacement of said workpiece and said electrode being such that a geometric center of said electrode moves along straight lines extending through a geometric center of an area to be machined and intersections of straight lines defining boundaries of said area to be machined such that, during movement along each said straight line extending through said geometric center of said area to be machined and one of said intersections, the two straight lines on said workpiece which form said one of said intersections are maintained parallel to respective two corresponding sides of said electrode, and gap widths between each of said two straight lines on said workpiece and said respective corresponding sides of said electrode are substantially the same throughout said movement;
• and
• performing discharge machining by controlling said electrode and said workpiece in such a manner that an electrode space is maintained between said electrode and said workpiece to an extent that electric discharge occurs in said interelectrode space;
• and
• superposing a predetermined minute displacement motion on said relative displacement to an extent that machining accuracy is not affected by said superposition.

A discharge machining apparatus for machining a workpiece by applying electric current to said workpiece and an electrode through a machining solution in the interelectrode space between said workpiece and said electrode comprising:

• first driving means for determining whether discharge machining is acceptable in a primary machining direction and if so moving said electrode relative to said workpiece so that a predetermined machining space is maintained between said electrode and said workpiece;
• second driving means for moving said electrode relative to said workpiece in a direction substantially perpendicular to said primary machining direction;
• control means for controlling a relative position of said electrode and said workpiece according to a voltage across said interelectrode space;
• and
• minute displacement control means for minutely modifying said relative position of said electrode and said workpiece in association with said control of said control means.