Patent Application
20180318951
The present invention relates to an apparatus and method for electro-polishing complex shapes and more specifically, and apparatus and method for electro-polishing metal leading edges for composite fan blades.
Structures that travel at high speed and that are formed of composite materials can be clad by metals to provide additional strength to resist impacts. Such structures include the high speed fan blades of gas turbine engines that are formed of composite materials. Composite materials can have limited impact resistance in comparison with other materials such as metal alloys and therefore fan blades that include composite materials can also include metal leading edges (MLE's). The metal leading edge is polished to provide corrosion protection. One problem with conventional methods of producing MLE's is that they are difficult to polish because of their complex shape.
This problem is addressed by an apparatus configured to electrically connect predetermined regions of complex shapes to an electrical pole.
According to one aspect of the technology described herein there is provided an apparatus for electro-polishing an object that has a complex shape that defines a cavity. The apparatus includes an electrode that is configured to closely engage a predetermined location of the object. The electrode is configured to be electrically connected to a power supply.
According to another aspect of the technology described herein there is provided a method for electro-polishing metal. The method includes the steps of: providing an object that has a wall and the wall defines a first surface that is to be polished and a second surface; positioning an electrode on the object to be polished such that the electrode is in contact with the second surface; connecting the electrode to a power supply; placing the object to be polished in an electrolyte solution such that the object is an anode; and passing current through the electrode.
The invention may be best understood by reference to the following description, taken in conjunction with the accompanying drawing figures in which:
Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,
Referring now to
The electrode 50 is configured to be positioned within the cavity 38 of the MLE 10 as shown in
Referring now to
As shown in
The technology described herein can be better understood through a description of the operation thereof. A location for positioning the electrode 50 within the MLE cavity 38 is determined. Preferable locations for electrode 50 include those that are located within cavity 38 such that they are opposite areas where enhanced polishing on the outer surface 34 of the MLE 10 is needed. Such areas are often those associated with a complex geometry. The electrode 50 is then placed within the cavity 38 at the determined location and positioned such that the electrode outer surface 54 is in contact with the inner surface 36 of the MLE 10. Preferably, the electrode 50 is positioned such that the electrode outer surface 54 of the electrode 50 is in substantially continuous contact with the inner surface 36.
The MLE 10 and the electrode 50 is then placed within the tank 12 such that at least portions of the MLE 10 and the electrode 50 are covered by the electrolyte solution 13. It should be appreciated that the electrolyte solution 13 can be added to the tank 12 either before or after the MLE 10 is positioned within the tank 12. The electrode 50 is electrically connected to an electrical pole of the power supply via the electrical connector 64. An electrical current is passed between the cathodes 14 and 16 and the electrode 50. Because the MLE 10 is electrically connected to cathodes 14 and 16 via the electrode 50 and the connector 64, the MLE 10 effectively acts as the anode and material is removed from the surface of the MLE 10. In this manner material is removed from the outer surface 34 of the MLE 10 such that MLE 10 is polished.
Referring now to an alternate embodiment as shown in
An electrode 170 is positioned with the cavity 138. The electrode 170 includes a first dam 172 positioned at the first end 128 and a second dam 174 positioned at the second end 132. The first dam 172 and the second dam 174 are removable fixtures that will be removed from the MLE after an electro-polishing process. A plug 176 is positioned between the first dam 172 and the second dam 174. The plug 176 is formed of a conductive substance and is formed to be in direct contact with the inner surface 136 of the MLE 110. The plug 176 is a low-melt alloy. By way of example and not limitation, the plug 176 can be formed of one of the following: bismuth based alloys containing lead, tin, cadmium or other metals; copper based alloys; iron based alloys; aluminum based alloys; silver; gold; and a combination thereof. The electrode 170 is electrically connected to at least one conductor 164. In the illustrated embodiment, at least an end of a plurality of conductors 164 is embedded in the plug 176. Alternatively, the conductors can be electrically connected to at least one of the first dam 172, the second dam 174, the plug 176, and a combination thereof. The electrical connection can be via a terminal.
The electrode 170 is formed according to the following method: The first dam 172 is positioned within the cavity 138 of the MLE 110 at the first end 128. The second dam 174 is positioned within the cavity 138 of the MLE 110 at the second end 132. The first dam 172 and the second dam 174, in conjunction with a portion of the inner surface 136, define an electrode region 175. To form the plug 176, material is melted during a melting process and poured into the electrode region 175. In accordance with the illustrated embodiment, the material is allowed to solidify before use.
The electrode 170 is used during an electro-polishing process as described above with respect to electrode 50. When the polishing process is complete the plug 176 and the first and second dams 172 and 174 are removed from the MLE 110. It should be appreciated that the plug 176 can be removed by melting or other suitable method.
The invention is an apparatus and method for providing precisely positioned electrical contact to complex shapes during an electro-polishing process.
The commercial advantages of the disclosed technology include minimized damage caused by the electro-polishing process and better polishing of complex shapes. One advantage of the disclosed technology when compared with conventional electro-polishing technologies is a reduction in the amount of racking, fixture marks, and burns that can be caused during a conventional electro-polishing process. Such a reduction is achieved because the conductor acts as a fixture. In this regard, the larger surface area of the conductor relative to conventional conductors distributes the potentially damaging mechanical and electrical forces associated with conventional electro-polishing conductors. Another advantage of the presently disclosed technology over conventional electro-polishing technology is that the contactors can be positioned and shaped such that electro-polishing is preferentially achieved in areas that would not be as well polished using conventional methods.
The foregoing has described an apparatus and method for electro-polishing a complex shape such as a metal leading edge for use in a gas turbine engine. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.
Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.
The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
