Apparatus for shaping electrodes

Claim 1

An improved apparatus for forming electrical discharge machining electrodes said apparatus being of the type including a first platen, a second platen mounted in superimposed relation and adapted to be driven vertically with respect to said first platen, a die member having an abrasive surface mounted on one of said platens, a workpiece member mounted on the platen opposite the platen on which said die member is mounted in working alignment with said die member, means for applying horizontal oscillatory rotary motion to said first platen, vertical drive means for infeeding said workpiece member and said die member into contact with each other while said oscillatory rotary motion is being applied to thereby abrasively shape said workpiece member to the form of said die member, and wherein said improvement comprises means for sensing the relative vertical position of said die member with respect to said workpiece member and generating an output signal representing said relative vertical position; means for providing a first predetermined reference signal representing a first relative vertical position and corresponding to a preselected maximum vertical distance between said die member and said workpiece member; means for providing a second predetermined reference signal representing a second relative vertical position and corresponding to a vertical distance between said die member and said workpiece member of substantially zero; means for providing a third predetermined reference signal representing a third relative vertical position and corresponding to a preselected penetration of said workpiece member by said die member; means coupled to said sensing means, and to said first, second and third reference signal means for comparing the output signal of said sensing means with said first, second and third reference signals and for generating first, second and third output signals when the output of said sensing means is equal to said first, second and third reference signals respectively; said vertical drive means being adapted for infeed and outfeed operation at at least two drive rates; and means coupled to said comparing means for cyclically controlling the operation of said vertical drive means to infeed said die member and said workpiece member at a first relatively higher rate until the output signal of said sensing means is equal to said second reference signal, at a second relatively slower rate until the output signal of said sensing means is equal to said third reference signal, and to outfeed said die member and said workpiece at said first relatively higher rate until the output signal of said sensing means is equal to said first reference signal.