Electrochemical polishing of non-uniform features

1. A method of controlling a working gap between at least one cathodic tool and an anodic workpiece in an electrochemical material dissolution process, the method comprising:

at least partially immersing the at least one cathodic tool and the anodic workpiece in a conductive electrolyte solution, the at least one cathodic tool comprising a plurality of cathodic heads defining a working gap between each of the cathodic heads and the anodic workpiece;

independently varying the working gap between each of the cathodic heads and the anodic workpiece according to electrochemical working conditions or offset values;

providing a negative electrical potential to the at least one cathodic tool;

monitoring one or more of the electrical potential, current, current density and charge between the at least one cathodic tool and the anodic workpiece to determine the working gap between the at least one cathodic tool and the anodic workpiece; and,

controlling one or more process parameters to maintain one or more of the working gap and electrochemical working conditions between the at least one cathodic tool and the anodic workpiece at a targeted value.

2. The method as claimed in claim 1 , wherein the anodic workpiece is at least partially comprised of a metallic material.

3. The method as claimed in claim 1 , wherein the anodic workpiece comprises a metallic aerospace article such as, for example, a casing, pipe, disc, bladed disk, drum, bladed drum, ring, bladed ring or aerofoil.

4. The method as claimed in claim 1 , the process parameters comprising, for example, one or more of working gap, electrical potential, current, current density, charge, resistance, cathodic tool feed rate, processing time, cathodic tool depth, electrolyte flow rate and/ or pressure, temperature and electrolyte chemistry.

5. The method as claimed in any claim 1 , wherein the controlling step comprises comparing or correlating one or more of the electrical potential, current, current density and charge between the at least one cathodic tool and the anodic workpiece with sample or real-time data to convert the monitored electrical output into an estimation of the working gap.

6. The method as claimed in claim 1 , wherein the monitoring system comprises one or more of a drive, actuation, spring, resilient member or reciprocating mechanism to increase or decrease the working gap according to the monitored electrical output.

7. The method as claimed in claim 1 , wherein each of the plurality of cathodic heads comprises an insulating tip, guide portion or member to provide the working gap between each of the plurality of cathodic heads and the anodic workpiece.

8. The method as claimed in claim 1 wherein the electrolyte has a pH of 7or less.

9. The method as claimed in claim 1 wherein the electrolyte has a pH of 7 or more.

10. The method as claimed in claim 1 wherein the electrolyte comprises a molten salt solution.

11. The method as claimed in claim 1 wherein a facing surface of each of the at least one cathodic tool or each of the plurality of cathodic heads is at least partially contoured, the facing contour of the or each at least one cathodic tool or each of the plurality of cathodic heads at least partially replicating the desired shape of at least a portion of the anodic workpiece.

12. An electrochemical material dissolution apparatus configured to remove material from a surface of an anodic workpiece, the apparatus comprising:

at least one cathodic tool comprising a plurality of cathodic heads defining a working gap between each of the cathodic heads and the anodic workpiece, the at least one cathodic tool and the anodic workpiece being at least partially immersed in a conductive electrolyte solution;

an actuation system configured to independently vary the working gap between each of the cathodic heads and the anodic workpiece according to electrochemical working conditions or offset values;

an electrical source configured to provide one or more of a controllable voltage and a controllable current to the at least one cathodic tool;

an electrical detection device configured to monitor one or more of electrical potential, current density, charge and current applied to the at least one cathodic tool so as to determine a working gap between the at least one cathodic tool and the anodic workpiece;

the electrical detection device further comprising a feedback system and the actuation system configured to control process parameters to maintain one or more of the working gap and electrochemical working conditions between the at least one cathodic tool and the anodic workpiece at a targeted value.

13. The method as claimed in claim 7 , wherein the insulating tip has a rounded surface.

14. A method of controlling a working gap between at least one cathodic tool and an anodic workpiece in an electrochemical material dissolution process, the method comprising:

at least partially immersing the at least one cathodic tool and the anodic workpiece in a conductive electrolyte solution, the at least one cathodic tool comprising a plurality of cathodic heads defining a working gap between each of the cathodic heads and the anodic workpiece, each of the plurality of cathodic heads comprising an insulating tip;

providing a negative electrical potential to the at least one cathodic tool;

monitoring one or more of the electrical potential, current, current density and charge between the at least one cathodic tool and the anodic workpiece to determine the working gap between the at least one cathodic tool and the anodic workpiece; and,

controlling one or more process parameters to maintain one or more of the working gap and electrochemical working conditions between the at least one cathodic tool and the anodic workpiece at a targeted value.

15. The method as claimed in claim 7 , wherein the insulating tip has a rounded surface.