Abstract: An electrochemical machining tool assembly includes first and second tools that are spaced apart from one another so that a workpiece can be located therebetween. The assembly also includes a first ultrasonic transducer mounted in the first tool and a second ultrasonic transducer mounted in the second tool. The electrochemical machining process is monitored by generating ultrasonic waves with the first and second ultrasonic transducers, and then detecting the arrival times, at the first and second ultrasonic transducers, of certain reflections of the ultrasonic waves. The detected arrival times are then used to calculate parameters such as the gap sizes between the first and second tools and a workpiece situated therebetween and the thickness of the workpiece.

Abstract: An electrode having a dielectric coating is patterned to provide axially spaced rows of insulating material on the external surface of the electrode with one or more gaps in the insulating material of each row. The electrode is placed in a preformed hole of a turbine bucket and an electrolyte is provided for flow between the electrode and the walls of the hole. Upon application of an electrical current, portions of the material of the interior wall surface directly opposite the non-insulated portions of the electrode are dissolved, forming grooves. The insulated portions of the electrode leave axially spaced rows of projections extending toward the axis of the hole. The gaps in the rows or projections are axially misaligned. The projections form turbulators in the cooling flow passages of the bucket, enhancing the heat transfer coefficient.

Abstract: A stuck locking pin is removed from a turbine rotor by forming an aperture in the locking pin. The diameter of the aperture is less than the diameter of the locking pin, such that a thin shell portion remains in the locking pin receiving slot of the rotor. The locking pin then can be easily removed by any suitable means, such as by driving a high-strength metal rod into the aperture. The driving force stretches the thin shell portion, which easily separates from the rotor.

Abstract: A method of shaping a tool comprises the steps of defining a shape of an article to be formed with the tool as a plurality of first elements; defining an initial shape of the tool as a plurality of second elements; determining an electric potential of each of the first and second elements; determining an equipotential line between the article and the initial shape of the tool based on the electric potential of the first and second elements; and forming the tool to have a shape coincident with the equipotential line.

Abstract: A stuck locking pin is removed from a turbine rotor by forming an aperture in the locking pin. The diameter of the aperture is less than the diameter of the locking pin, such that a thin shell portion remains in the locking pin receiving slot of the rotor. The locking pin then can be easily removed by any suitable means, such as by driving a high-strength metal rod into the aperture. The driving force stretches the thin shell portion, which easily separates from the rotor.

Abstract: A post-cast EDM process is used to remove material from the interior surface of a nozzle vane cavity of a turbine. A thin electrode is passed through the cavity between opposite ends of the nozzle vane and displaced along the interior nozzle wall to remove the material along a predetermined path, thus reducing the thickness of the wall between the cavity and the external surface of the nozzle. In another form, an EDM process employing a profile as an electrode is disposed in the cavity and advanced against the wall to remove material from the wall until the final wall thickness is achieved, with the interior wall surface being complementary to the profile surface.

Abstract: A machining process for forming a raised area in a wall of a predrilled hole includes distributing electrolyte via a workpiece internal cavity to a number of predrilled holes. Next, position a template including at least one electrode coated with an insulating material in a pattern defining the raised area to be formed in the wall of the predrilled hole below the workpiece such that the electrode is positioned within a predrilled hole and machining by passing electric current between the electrode and the workpiece wall and circulating electrolyte through the hole.

Abstract: An electrode of an EDM drill is aligned in at least two planes by positioning the electrode at a plurality of positions and determining the distances between the rotary center of the EDM drill and a plurality of points on the workpiece surface co-linear with the longitudinal axis of the electrode. By comparing these distances, it can be ascertained whether the electrode is aligned with the workpiece surface in a given plane. If the electrode is not aligned, an angle of rotation needed to align the electrode with the workpiece surface can be determined empirically.

Abstract: The back side recessed cooling surface of a shroud defining in part the hot gas path of a turbine is electrochemically machined to provide surface roughness elements and spaces therebetween to increase the heat transfer coefficient. To accomplish this, an electrode with insulating dielectric portions and non-insulating portions is disposed in opposition to the cooling surface. By passing an electrolyte between the cooling surface and electrode and applying an electrical current between the electrode and a shroud, roughness elements and spaces therebetween are formed in the cooling surface in opposition to the insulating and non-insulating portions of the electrode, hence increasing the surface area and heat transfer coefficient of the shroud.

Abstract: An apparatus for electrical discharge machining multiple holes in an electrically conductive work piece, includes an electrical discharge machine for rotatably mounting a first electrode, and at least one electrical discharge unit for rotatably mounting at least one second electrode. The electrical discharge machine includes a driver and a controller, the driver is desirably coupled to the electrical discharge machine and the electrical discharge unit for rotating the first electrode and the at least one second electrode, and the controller is desirably coupled to the electrical discharge machine and the at least one electrical discharge unit for controlling a supply of electrical energy from the first electrode and second electrode to the workpiece.

Abstract: An apparatus for drilling cooling holes through a wall of a hollow component is disclosed. First, a laser drill is used for drilling at least one rough blind hole within a component wall, for example a turbine airfoil, so as to retain a residual bottom plate portion. Next, an electro discharge machine (EDM), for example a rotating EDM or plunge EDM, is used for finishing at least one rough blind hole so as to create at least one finished hole and breaking through the bottom plate portion.

Abstract: An electrochemical machining process is monitored by embedding an ultrasonic sensor in an electrochemical machining tool to provide a tool assembly, placing the tool assembly in a spatial relationship with a workpiece, disposing an electrolytic fluid at least in a gap between the tool and the workpiece, connecting the tool and the workpiece to an electrical power source, generating an acoustic wave from the ultrasonic sensor to propagate through the electrolytic fluid to the workpiece and reflect back from the workpiece, and, based on the propagation and reception of the acoustic wave, calculating measurement of at least the size of the gap or the thickness of the workpiece.

Abstract: An electrochemical stripping process is described that strips at least one metallic coating from a substrate. Due to the electrochemical selectivity of the disclosed process, the parent alloy is minimally affected by the electrochemical stripping process. The process comprises providing an electrolyte; disposing the coated articles and at least one electrode in the electrolyte; applying a current between the electrode and the coated articles, and removing the at least one coating from the coated articles without modifying the parent alloy. The system for the electrochemical stripping process comprises an electrolyte; a direct current source; and plurality of electrodes from which a direct current may be directed to the article being stripped. The direct current source is capable of being connected to the coated articles and the plurality of electrodes. The system permits removal of the at least one coating from the parent alloy.

Abstract: A process for producing a pattern in the surface coating of an electrode used in an electrochemical machining process comprises the steps of providing a cylinder having a body composed of an electrically conductive material and a surface coating of an electrically insulating material and exposing the surface coating of the cylinder to a source of light in accordance with the pattern. Locators(s) may optionally be formed on the surface of the cylinder to assist in positioning the electrode in a predrilled hole.

Abstract: An electrochemical machine is disclosed for use in an electrochemical machining process to simultaneously generate different levels of metal removal. The electrochemical machine comprises at least two electrodes, each including an electrically conductive cylinder having an external surface partially coated with an insulated coating. The insulating coating is in a pattern defining raised areas to be formed on an internal surface of a predrilled hole in a workpiece wherein at least one of the electrodes has a varied pattern of insulating coating.

Abstract: An electrode for use in an electrochemical machining process comprising an outer metal skin of corrosion resistant material, an inner core of conductive material, and an insulating coating disposed on an external surface of the outer metal skin. The external surface is partially coated with the insulating coating so as to define a pattern of raised areas to be formed on an internal surface of a predrilled hole in a workpiece.

Abstract: An electrode used as a tool in an electrochemical machining process to generate raised areas or ridges in the walls of a predrilled hole in an electrically conductive workpiece has an electrically conductive cylinder partially coated with an electrically insulating material in a pattern defining the raised areas to be formed. The pattern may comprise a plurality of spaced apart rings. An electrochemical machining method of drilling bulbs in the walls of a predrilled hole uses the electrode of the invention to greatly increase process efficiency.

Abstract: A post-cast EDM process is used to remove material from the interior surface of a nozzle vane cavity of a turbine. A thin electrode is passed through the cavity between opposite ends of the nozzle vane and displaced along the interior nozzle wall to remove the material along a predetermined path, thus reducing the thickness of the wall between the cavity and the external surface of the nozzle. In another form, an EDM process employing a profile as an electrode is disposed in the cavity and advanced against the wall to remove material from the wall until the final wall thickness is achieved, with the interior wall surface being complementary to the profile surface.

Abstract: A method of shaping a tool comprises the steps of defining a shape of an article to be formed with the tool as a plurality of first elements; defining an initial shape of the tool as a plurality of second elements; determining an electric potential of each of the first and second elements; determining an equipotential line between the article and the initial shape of the tool based on the electric potential of the first and second elements; and forming the tool to have a shape coincident with the equipotential line.

Abstract: An electrochemical machining process is disclosed for forming multiple raised areas having multiple heights in a wall of predrilled holes within a workpiece. Positioned within each hole is an electrode coated with an insulating material in a pattern defining the raised areas to be formed in the wall of each respective hole. An electric current is applied from a power supply to each of the electrodes. A resistor is positioned between the power supply and at least one of the electrodes to vary the voltage passing through the electrode to vary the amount of material removed within that respective hole.