Method of and apparatus for machining a 3-D cavity in a workpiece

A method of forming a cavity of a desired three-dimensional contour in a workpiece, comprising the steps of:

• (a) mechanically drilling a multiplicity of holes in a said workpiece substantially all over but within a three-dimensional region which is destined to constitute said cavity and is bounded by a programmed outline corresponding to said desired three-dimensional contour whereby only a minimum of stock is left unmachined in said workpiece within said region;
• and thereafter
• (b) electroerosively machining said minimum left unmachined stock among said holes and within said programmed region with at least one electrical machining tool electrode having a machining surface which is complementary in shape with said desired contour and is positioned to lie in parallel with said programmed outline, by:
• (b1) passing an electrical machining current across a machining gap between said machining surface and said region in the presence of an electrical machining liquid in said holes and said gap, and (b2) advancing said at least one tool electrode relatively into said workpiece while maintaining said parallelism and holding said machining gap spacing substantially constant until said machining surface reaches a position spaced by said spacing from said programmed outline, step (a) being carried out with a plurality of drilling tools having different tool sizes to produce the corresponding plural sets of holes different in diameter.

A method of forming a cavity of a desired three-dimensional contour in a workpiece, comprising the steps of:

• (a) mechanically drilling a multiplicity of holes in a said workpiece substantially all over but within a three-dimensional region which is destined to constitute said cavity and is bounded by a programmed outline corresponding to said desired three-dimensional contour whereby only a minimum of stock is left unmachined in said workpiece within said region;
• and thereafter
• (b) electroerosively machining said minimum left unmachined stock among said holes and within said programmed region with at least one electrical machining tool electrode having a machining surface which is complementary in shape with said desired contour and is positioned to lie in parallel with said programmed outline, by:
• (b1) passing an electrical machining current across a machining gap between said machining surface and said region in the presence of an electrical machining liquid in said drilled holes and said gap while (b2) advancing said tool electrode relatively into said workpiece, with said parallelism maintained, so as to hold said machining gap spacing substantially constant until said machining surface reaches a position spaced by said spacing from said programmed outline, said multiple holes being drilled in step (a), respectively to individually predetermined depths such that an outline defined by the floor regions of said holes substantially conforms to and are substantially equi-distantly spaced from said programmed outline.

A method of forming a cavity of a desired three-dimensional contour in a workpiece, comprising the steps of:

• (a) mechanically drilling a multiplicity of holes in a said workpiece substantially all over but within a three-dimensional region which is destined to constitute said cavity and is bounded by a programmed outline corresponding to said desired three-dimensional contour whereby only a minimum of stock is left unmachined in said workpiece within said region;
• and thereafter
• (b) electroerosively machining said minimum left unmachined stock among said holes and within said programmed region with at least one electrical machining tool electrode having a machining surface which is completely in shape with said desired contour and is positioned to lie parallel with said programmed outline, by:
• (b1) passing an electrical machining current across a machining gap between said machining surface and said region in the presence of an electrical machining liquid in said drilled holes and said gap while (b2) advancing said tool electrode relatively into said workpiece, with said parallelism maintained, so as to hold said machining gap spacing substantially constant until said machining surface reaches a position spaced by said spacing from said programmed outline, said multiple holes drilled in step (a) including a set of holes obliquely intersecting another set of the holes, step (b) including the step of flushing said machining liquid through said oblique holes under a negative pressure to create a dynamic flow of said machining liquid through said machining gap.