Critical orifice gap setting for ECM grooving of flat plates

Abstract

An apparatus and method for electrochemically etching grooves in a working surface. A frame holds a working surface about an axis and facing a movable electrode movable along the axis. The electrode is axially movable and has a surface carrying a groove pattern to fix on the working surface. A source of electrolyte is pumped at a fixed static pressure rate between the surface of the movable electrode and the working surface. A support fixture is provided for supporting the electrode for movement toward and away from the working surface with minimal frictional restriction. A force biases the electrode surface toward the working surface so that a gap through which the electrolyte flows between the surface of the movable electrode and the working surface is determined primarily by the static flow rate of the electrolyte and the force bias of the electrode toward the working surface.

What is claimed is:  
     
         1 . An apparatus for electrochemically etching grooves in a working surface, the apparatus comprising: 
 a frame for holding the working surface about an axis and facing a movable electrode movable along the axis, the electrode being axially movable and having a surface carrying a groove pattern to fix on the working surface;    a source of electrolyte to be pumped at a fixed static pressure rate between the surface of the movable electrode and the working surface; and    a support fixture for supporting the electrode for movement toward and away from the working surface with minimal frictional restriction, and a force biasing the electrode surface toward the working surface so that a gap through which the electrolyte flows between the surface of the movable electrode and the working surface is determined primarily by the static flow rate of the electrolyte and the force bias of the electrode toward the working surface.    
     
     
         2 . The apparatus of  claim 1 , wherein the support fixture comprises a hydrostatic bearing cartridge assembly.  
     
     
         3 . The apparatus of  claim 1 , wherein the bias of the electrode surface toward the working surface is established by pressure against a distal end of the electrode.  
     
     
         4 . The apparatus of  claim 3 , wherein the pressure is caused by a substantially frictionless air cylinder.  
     
     
         5 . The apparatus of  claim 1 , further comprising a source of electric potential to be applied between the electrode and the working surface.  
     
     
         6 . The apparatus of  claim 5 , wherein the electric potential creates a fixed current across the gap so that a rate at which an ECM process is carried out is determined primarily by the gap.  
     
     
         7 . The apparatus of  claim 1 , wherein the working surface is a surface of a counter plate.  
     
     
         8 . The apparatus of  claim 1 , wherein the working surface is a surface of a conical element.  
     
     
         9 . The apparatus of  claim 1 , wherein the electrode comprises a plenum through which electrolyte flows.  
     
     
         10 . A method of electrochemically etching grooves in a working surface, the method comprising: 
 holding, via a frame, the working surface about an axis and facing a movable electrode movable along the axis, the electrode being axially movable and having a surface carrying a groove pattern to fix on the working surface;    pumping electrolyte at a fixed static pressure rate between the surface of the movable electrode and the working surface; and    supporting, via a support fixture, the electrode for movement toward and away from the working surface with minimal frictional restriction, and using a biasing force to bias the electrode surface toward the working surface so that a gap through which the electrolyte flows between the surface of the movable electrode and the working surface is determined primarily by the static flow rate of the electrolyte and the force bias of the electrode toward the working surface.    
     
     
         11 . The method of  claim 11 , wherein the support fixture comprises a hydrostatic bearing cartridge assembly.  
     
     
         12 . The method of  claim 11 , wherein the bias of the electrode surface toward the working surface is established by pressure against a distal end of the electrode.  
     
     
         13 . The method of  claim 12 , wherein the pressure is caused by a substantially frictionless air cylinder.  
     
     
         14 . The method of  claim 10 , further comprising a source of electric potential to be applied between the electrode and the working surface.  
     
     
         15 . The method of  claim 14 , wherein the electric potential creates a fixed current across the gap so that a rate at which an ECM process is carried out is determined primarily by the gap.  
     
     
         16 . The method of  claim 10 , wherein the working surface is a surface of a counter plate.  
     
     
         17 . The method of  claim 10 , wherein the working surface is a surface of a conical element.  
     
     
         18 . The method of  claim 10 , wherein the electrolyte flows through a plenum in the electrode.  
     
     
         19 . An apparatus for electrochemically etching grooves in a working surface, the apparatus comprising: 
 means for holding the working surface about an axis and facing a movable electrode movable along the axis, the electrode being axially movable and having a surface carrying a groove pattern to fix on the working surface;    means for pumping electrolyte at a fixed static pressure rate between the surface of the movable electrode and the working surface;    means for supporting the electrode for movement toward and away from the working surface with minimal frictional restriction; and    means for biasing the electrode surface toward the working surface so that a gap through which the electrolyte flows between the surface of the movable electrode and the working surface is determined primarily by the static flow rate of the electrolyte and a force bias of the electrode toward the working surface.    
     
     
         20 . The apparatus of  claim 19 , wherein the means for biasing the electrode surface toward the working surface is adapted to apply pressure against a distal end of the electrode.  
     
     
         21 . The apparatus of  claim 20 , wherein the means for biasing the electrode surface toward the working surface comprises a substantially frictionless air cylinder.  
     
     
         22 . The apparatus of  claim 21 , wherein the air cylinder is located distally of the electrode.