This application is a continuation and claims priority to U.S. patent application Ser. No. 11/327,035 filed Jan. 5, 2006 for “METHODS AND APPARATUS FOR FABRICATING COMPONENTS,” which is hereby incorporated by reference herein in its entirety.
The methods and apparatus described and/or illustrated herein relate generally to fabricating components, and more specifically to fabricating components using electric-discharge machining (EDM).
At some known turbine engine components, such as turbine nozzle and blade airfoils, use film cooling to cool surfaces that are exposed to hot gas flows during operation of the engine. More specifically, some known turbine engine airfoils are cooled by channeling cooling air through an internal cooling passage and out a plurality of cooling holes in the airfoil such that a film of cooling air flows over the airfoil. The film of cooling air acts as a barrier between the hot gas flow and the airfoil surface to facilitate cooling the airfoil. To facilitate promoting distribution of a cooling air film over the airfoil, at least some known cooling holes include a non-circular and/or divergent discharge opening, sometimes referred to as diffuser cooling holes.
At least some known diffuser cooling holes are fabricated using EDM. However, EDM may be difficult, time-consuming, and/or expensive, particularly when fabricating a plurality of diffuser cooling holes in the airfoil. For example, some known EDM processes for fabricating diffuser cooling holes use a comb-type electrode. However, comb-type electrodes may sometimes only be practical when fabricating a row of diffuser cooling holes that each have generally the same entrance angle. Some other known EDM processes for fabricating diffuser cooling holes move an electrode about a plurality of axes to fabricate the non-circular and/or divergent discharge openings. However, EDM processes that include moving an electrode about a plurality of axes to form the non-circular and/or divergent openings may be time-consuming and/or less repeatable than desired. Some other known EDM processes for fabricating diffuser cooling holes include first drilling a round through hole, and thereafter manually loading a stamped electrode into the EDM device and fabricating the non-circular and/or divergent opening using the stamped electrode. However, because of multiple operations and manual loading of the stamped electrode, such EDM processes may be time-consuming and/or costly.
In one aspect, a method is provided for removably holding an electrode for use in an electric-discharge machining (EDM) apparatus including a tool holder having an expandable collet. The method includes providing the collet in an unclamped position, receiving at least a portion of the electrode within an opening of the collet, and moving the collet to a clamped position using at least one of electrical, pneumatic, and hydraulic power, wherein in the clamped position the collet exerts a radially inward force around a circumference of the electrode to facilitate fixedly holding the electrode.
In another aspect, a tool holder assembly is provided for removably holding an electrode for use in an electric-discharge machining (EDM) apparatus. The tool holder assembly includes an expandable collet having an opening for receiving at least a portion of the electrode. The collet is movable between an expanded unclamped position that facilitates receiving the electrode within the collet opening and removing the electrode from the collet opening, and a compressed clamped position wherein the collet exerts a radially inward force around a circumference of the electrode to facilitate fixedly holding the electrode. The assembly also includes a source of at least one of pneumatic, electrical, and hydraulic power operatively coupled to the collet and configured to move the collet between the clamped and unclamped positions.
Referring to the drawings,
During operation, air flows through fan assembly 12, along a central axis 34, and compressed air is supplied to high pressure compressor 14. The highly compressed air is delivered to combustor 16. Airflow (not shown in
Airfoil 42 includes a first sidewall 44 and a second sidewall 46. First sidewall 44 is convex and defines a suction side of airfoil 42, and second sidewall 46 is concave and defines a pressure side of airfoil 42. Sidewalls 44 and 46 are connected at a leading edge 48 and at an axially-spaced trailing edge 50 of airfoil 42 that is downstream from leading edge 48.
First and second sidewalls 44 and 46, respectively, extend longitudinally or radially outward to span from a blade root 52 positioned adjacent dovetail 43 to a tip plate 54 which defines a radially outer boundary of an internal cooling chamber 56. Cooling chamber 56 is defined within airfoil 42 between sidewalls 44 and 46. Internal cooling of airfoils 42 is known in the art. In the exemplary embodiment, cooling chamber 56 includes a serpentine passage 58 cooled with compressor bleed air. Cooling chamber 56 is in flow communication with a plurality of diffuser cooling holes 70 for distributing a cooling air film over airfoil 42. As can be seen from
Machine head 104 includes a tool holder 108 coupled thereto. Tool holder 108 is electrically coupled to a negative terminal of power source 102 for receiving electrical current from powers source 102. Tool holder 108 removably holds an electrode 110 that discharges electrical current to turbine rotor blade 40 to machine material therefrom. In some embodiments, tool holder 108 is hollow and is supplied with a coolant to facilitate cooling tool holder 108 and/or electrode 110 during machining of turbine rotor blade 40.
Machine head 104 is movable to automatically retrieve an electrode 110 using tool holder 108, machine turbine rotor blade 40 using the electrode 110, and dispose of the electrode 110 after the machining process. In the exemplary embodiment, machine head 104 is movable between an electrode storage rack 112, fixture 106, and a disposal basket 114. Although machine head 104 may be movable along and/or about any number of axis and/or in any general direction(s), in the exemplary embodiment machine head 104 is generally movable along three axes 116, 118, and 120. In the exemplary embodiment, electrode storage rack 112 includes a plurality of differently sized and/or shaped electrodes for machining differently sized and/or shaped diffuser cooling holes 70, as will be described in more detail below. In the exemplary embodiment, disposal basket 120 receives electrodes 110 released from tool holder 108 after the electrode 110 has performed a machining process. However, machine head 104 may also replace electrodes 110 that have performed a machining process back in storage rack 112. As such, in some embodiments one or more electrodes 110 is reusable after performing a machining process, although a re-usable electrode 110 may be retrieved by machine head 104, or manually, from rack 112 or basket 114. In some embodiments, one or more electrodes 110 are disposable.
Machine head 104 may be moved using any suitable structure, mechanism, and/or means that enable machine head 104 to perform the functions described herein. Examples of suitable means for moving machine head 104 include, but are not limited to electrical, pneumatic, and/or hydraulic power. Moreover, tool holder 108 may removably hold electrode 110 using any suitable structure, mechanism, and/or means that enable tool holder 108 to perform the functions described herein, for example fixedly holding an electrode 110 during a machining process. Examples of suitable means for removably holding electrode 110 include, but are not limited to, electrical, pneumatic, and/or hydraulic power.
Referring again to
Fixture 106 includes a retainer 156 for containing any suitable dielectric fluid (not shown). When turbine rotor blade 40 is coupled to fixture 106, at least a portion of blade 40 is immersed in the dielectric fluid. Fixture 106 is electrically coupled to a positive terminal of power source 102 for receiving electrical current from powers source 102 such that when turbine rotor blade 40 is coupled to fixture 106, blade 40 is electrically coupled to a positive terminal of power source 102 for receiving electrical current from powers source 102.
Apparatus 100 includes a control system 158 for monitoring and/or controlling general operation of apparatus 100 to machine turbine blade 40. Examples of monitoring and/or controlling operation of apparatus 100 include, but are not limited to, monitoring and/or controlling movement of fixture 106 and machine head 104, monitoring and/or controlling operation of tool holder 108, and/or monitoring and/or controlling parameters of the EDM process, such as, but not limited to an amount, duration, and/or other characteristic of the transient electric discharge, a location and/or orientation of electrode 110 relative to turbine rotor blade 40, a size, shape, and/or other characteristic of the electrode 110 being used for a particular machining process, and/or a characteristic of the dielectric fluid. In the exemplary embodiment, control system 158 includes a processor 160 for executing control instructions stored in a memory 162, and a display 164 for displaying information about apparatus 100 and its operation, such as, but not limited to, EDM process parameters. Control system 158 also includes an input device 166 for inputting information into control system 158, such as, but not limited to, input of EDM process parameters.
In operation, a turbine rotor blade 40 is coupled to fixture 106. An orientation and/or location of fixture 106 is then adjusted by rotating fixture 106 about axes 152 and/or 154 to position fixture 106, and therefore blade 40, in a location and/or orientation relative to machine head 104 that facilitates machining one or more diffuser cooling holes 70 within blade 40. Machine head 104 is moved to a position adjacent the electrode storage rack 112 such that tool holder 108 is adjacent a predetermined electrode 110 having a predetermined size and/or shape for machining at least a portion of one or more predetermined sized and/or shaped diffuser holes 70. Tool holder 108 grips the electrode 110 and as machine head 104 is moved away from rack and towards turbine rotor blade 40 the electrode 110 is removed from rack 112 and fixedly held by tool holder 108. Machine head 104 is then moved towards turbine rotor blade 40 to at least partially machine one or more diffuser cooling holes 70 therein. As electrode 110 is moved toward blade 40, when electrode 110 reaches a position such that the dielectric of the gap therebetween is broken down by an erosive electrical intermittent discharge thereacross, particles of material are removed from blade 40. Further pulsating discharges continue to erode material until hole 70 is at least partially formed. The predetermined size and/or shape of electrode 110 machines the predetermined sized and/or shaped diffuser cooling hole 70, for example the predetermined non-circular and/or divergent discharge opening 72. In some embodiments, electrode 110 machines one or more entire diffuser cooling holes 70, while in some embodiments electrode 110 machines only non-circular and/or divergent discharge openings 72. Once one or more holes 70 have been at least partially machined with the predetermined electrode 110, machine head 104 in a position adjacent electrode disposal basket 114 and tool holder 108 releases electrode 110 to dispose of electrode 110 in basket 114. Machine head 104 can then be moved to electrode storage rack 112 to retrieve an electrode having a different predetermined size and/or shape for machining one or more differently sized and/or shaped holes 70 in blade 40.
The above-described methods and apparatus may facilitate cost-effective and/or reliable fabrication of components using EDM. For example, by automatically retrieving and disposing of differently sized and/or shaped electrodes for machining a plurality of differently sized and/or shaped diffuser cooling holes, the above-described methods and apparatus may facilitate reducing a time and an amount of labor as compared with some known EDM processes.
Although the methods and apparatus described and/or illustrated herein are described and/or illustrated with respect to an airfoil, and more specifically to a turbine blade for a gas turbine engine, practice of the methods and apparatus described and/or illustrated herein is not limited to turbine blades, gas turbine engine components, nor airfoils generally. Rather, the methods and apparatus described and/or illustrated herein are applicable to fabricating any feature and/or portion of any component.
Exemplary embodiments of methods and apparatus are described and/or illustrated herein in detail. The methods and apparatus are not limited to the specific embodiments described herein, but rather, components of each apparatus, as well as steps of each method, may be utilized independently and separately from other components and steps described herein. Each component, and each method step, can also be used in combination with other components and/or method steps.
When introducing elements/components/etc. of the methods and apparatus described and/or illustrated herein, the articles “a”, “an”, “the” and “said” are intend portioned to mean that there are one or more of the element(s)/component(s)/etc. The terms “comprising”, “including” and “having” are intend portioned to be inclusive and mean that there may be additional element(s)/component(s)/etc. other than the listed element(s)/component(s)/etc.
While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
Number | Date | Country | |
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Parent | 11327035 | Jan 2006 | US |
Child | 11355413 | Feb 2006 | US |