A General Mechanism for Access Control: Its Relationship to Secure System Concepts

An electrode assembly for electro-chemically machining an article, such as an aerofoil shaped blade for a turbo machine. The assembly comprises a plurality of electrodes 2,3 for location adjacent a workpiece 7. Each electrode 2,3 is constrained to move in a first direction towards each other and towards the workpiece 7 and has two side members 22,23 carried by a main body 21. The side members 22,23 are constrained to move with the main body 21 and also relative to the main body in directions parallel to the first direction. The side members 22,23 advance ahead of the main body 21 and when they abut the side members 22,23 of the other electrodes 2,3 their advancement is stopped while the main bodies 21 of the electrodes 2,3, continue to approach each other for a predetermined distance. In this way edge effects during machining are eliminated enabling an accurate shape of article to be produced.