Patent Publication Number: US-9850589-B2

Title: System and methods for electrochemical grinding with a screen

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 61/991,877 filed on May 12, 2014 and titled System and Methods for Electrochemical Grinding with a Screen, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     FIELD 
     The present disclosure relates generally to grinding processes for material removal, and more particularly to a system and methods for electrochemical grinding with a screen element. 
     BACKGROUND 
     Grinding processes are employed to remove material from components for manufacture and finishing. Conventional methods of finishing and shaping aerospace components have employed grinding for high strength materials. One processing limitation of traditional grinding tools is the time required for grinding. Traditional grinding methods may be less effective with hardened or temperature resistant materials. While there have been improvements to grinding techniques, tool life and surface quality continues to be a concern. By way of example, traditional grinding may result in stresses or defects in components. 
     BRIEF SUMMARY OF THE EMBODIMENTS 
     Disclosed and claimed herein are a system and methods for electrochemical grinding. One embodiment is directed to an electrochemical grinding tool. The electrochemical grinding tool includes a grinding element having a grinding surface, wherein the grinding element is configured to be electrically coupled to a cathode of a voltage source. The grinding tool also includes a screen coupled to the grinding element, wherein the screen is configured to be electrically coupled to the cathode of the voltage source, and wherein the screen is configured to recover material by electroplating removed by the grinding element during electrochemical grinding. 
     Another embodiment is directed to an electrochemical grinding system. The grinding system includes a grinding tool including a grinding element having a grinding surface, wherein the grinding element is configured to be electrically coupled to a cathode of the voltage source. The grinding system also includes a screen coupled to the grinding element, wherein the screen is configured to be electrically coupled to the cathode of the voltage source, and wherein the screen is configured to recover material by electroplating removed by the grinding element during electrochemical grinding. The system also includes a controller configured to control the grinding tool for electrochemical grinding of a workpiece. 
     In one embodiment, a method is provided for electrochemical grinding. The method includes controlling a potential of a voltage source applied to a grinding tool, wherein the grinding tool includes a screen coupled to a grinding element and wherein the screen is electrically coupled to the cathode of the voltage source. The method also includes controlling a potential of the voltage source applied to a workpiece and controlling electrochemical grinding of the workpiece by the grinding tool, wherein the screen is configured to recover material by electroplating removed by the grinding element during electrochemical grinding. 
     Other aspects, features, and techniques will be apparent to one skilled in the relevant art in view of the following detailed description of the embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features, objects, and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout and wherein: 
         FIGS. 1A-1B  depict graphical representations of a grinding tool according to one or more embodiments; 
         FIGS. 2A-2C  depict graphical representations of a grinding tool and screen according to one or more embodiments; 
         FIG. 3  depicts a simplified system diagram according to one or more embodiments; and 
         FIG. 4  depicts a process for electrochemical grinding according to one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     Overview and Terminology 
     One aspect of the disclosure relates to systems and methods for grinding. In particular, systems and methods are provided for electrochemical grinding. In one embodiment, an electrochemical grinding tool is provided including a grinding element and a screen coupled to the grinding element. According to other embodiments, a system is provided for electrochemical grinding employing a grinding tool with a screen. In other embodiments, methods are provided for electrochemical grinding with a screen. 
     As used herein, the terms “a” or “an” shall mean one or more than one. The term “plurality” shall mean two or more than two. The term “another” is defined as a second or more. The terms “including” and/or “having” are open ended (e.g., comprising). The term “or” as used herein is to be interpreted as inclusive or meaning any one or any combination. Therefore, “A, B or C” means “any of the following: A; B; C; A and B; A and C; B and C; A, B and C”. An exception to this definition will occur only when a combination of elements, functions, steps or acts are in some way inherently mutually exclusive. 
     Reference throughout this document to “one embodiment,” “certain embodiments,” “an embodiment,” or similar term means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of such phrases in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner on one or more embodiments without limitation. 
     Referring now to the figures,  FIGS. 1A-1B  depict graphical representations of a grinding tool according to one or more embodiments.  FIG. 1A  depicts electrochemical grinding tool  100  including grinding element  105  and screen  110 . Grinding element  105  includes a grinding surface for removing material from one or more components. According to one embodiment, grinding element  105  may be a grinding wheel including abrasive material on the grinding surface. Grinding element  105  is configured to be electrically coupled to a cathode of a voltage source, such as potential connection  115   a . Screen  110  is electrically and mechanically coupled to grinding element  105 . According to one embodiment, screen  110  may be configured to be electrically coupled to the cathode of a voltage source. Screen  110  may be configured to recover material by the electroplating removed by the grinding element during electrochemical grinding. 
     Grinding tool  100  may be configured to remove material from one or more elements, such as workpiece  120 . By way of example, workpiece  120  may relate to one or more components, including but not limited to blades, bearings, vanes, housings, and jet engine components in general. 
     According to one embodiment, grinding tool  100  may be coupled to a voltage source during electrochemical grinding. By way of example, grinding tool  100  may be coupled to the cathode of a voltage source and workpiece  120  may be coupled to an anode of the voltage source. As shown in  FIG. 1A , grinding element  105  is electrically coupled to potential connection  115   a  and screen  110  is electrically coupled to potential connection  115   b  of voltage source (e.g., cathode connections). Workpiece  120  is electrically coupled to potential connection  125  of a voltage source (e.g., anode connections). 
     According to one embodiment, screen  110  may be configured to recover material removed by grinding element  105  during electrochemical grinding. Screen  110  may be removeably coupled to grinding element  105 .  FIG. 1B  depicts a graphical representation of grinding tool  100  in a disassembled view according to one or more embodiments. According to one embodiment, grinding element  105  may be a grinding wheel and screen  110  may be a metal mesh disk configured to be coupled to a surface of grinding element  105 . Screen  110  may be removable to allow for a replacement screen to be applied to grinding element  105 .  FIG. 1B  depicts optional connection element  130  which may be configured to couple screen  110  to a surface of grinding element  105 . 
     Referring now to  FIGS. 2A-2C , graphical representations of a grinding tool and screen are depicted according to one or more embodiments. According to one embodiment,  FIGS. 2A-2C  depict a grinding tool having a screen configured to the contour of the outer or grinding surface of a grinding element. The grinding tool of  FIGS. 2A-2C  may be similarly coupled to potentials of a voltage source as grinding tool  100  of  FIGS. 1A-1B . 
       FIG. 2A  depicts electrochemical grinding tool  200  including grinding element  205  and screen  210 . Grinding element  205  includes grinding surface  215  for removing material from one or more components. According to one embodiment, grinding element  205  may be a grinding wheel including abrasive material on grinding surface  215 . Grinding element  205  is configured to be electrically coupled to a cathode of a voltage source. Screen  210  is coupled to grinding element  205 . According to one embodiment, screen  210  may be configured to be electrically coupled to the cathode of a voltage source. Screen  210  may be configured to recover material removed by the electroplating by the grinding element during electrochemical grinding. 
       FIG. 2B  depicts electrochemical grinding tool  200  including grinding element  205  and screen  210  removed from grinding element  205 . According to one embodiment, screen  210  is a metal mesh contoured to grinding surface  215  of the grinding element  205 . 
       FIG. 2C  depicts a cross-sectional representation of electrochemical grinding tool  200  shown as grinding tool  201  including grinding element  205  and screen  210 , abrasive  216  applied to a grinding surface and bonding material  220 . 
     According to one embodiment, abrasive  216  includes at least one of a nonconductive material, diamond and aluminum oxide material. Abrasive  216  may be bonded to grinding element  205  by bonding material  220 . In certain embodiments, grinding element  205  includes nonconductive material, diamond and aluminum oxide material, bonded together by a bonding material such as nickel. According to another embodiment, screen  210  includes a plurality of openings to allow abrasive material  216  of grinding element  205  engage with a workpiece (e.g., workpiece  120 ). 
     It should be appreciated that grinding tools  200  and  201  of  FIGS. 2A-2C  may be different embodiments of the grinding tool of  FIGS. 1A-1B  wherein elements and attributes of the grinding tools may be similarly applied. 
       FIG. 3  depicts a simplified system diagram according to one or more embodiments. According to one embodiment, system  300  may employ one or more grinding tools described herein for electrochemical grinding. Electrochemical grinding system  300  includes a grinding tool  305  and controller  330 . 
     According to one embodiment, grinding tool  305  includes grinding element  310 , such as a grinding wheel, having a grinding surface. The grinding surface of grinding element  310  may include an abrasive material. In certain embodiments, grinding element  310  includes nonconductive material, diamond and aluminum oxide material, bonded together by a bonding material such as nickel. In another embodiment, grinding tool  305  includes screen  315  coupled to grinding element  310 . Screen  315  is configured to recover material by the electroplating removed by the grinding element  310  during electrochemical grinding. 
     Controller  330  may be configured to control grinding tool  305  for electrochemical grinding of workpiece  360  including potential applied and control of grinding tool  305 . In one embodiment, grinding tool  305  may be rotated by drive unit  320  via shaft  321 . Controller  330  may be configured to control drive unit  320  for control of rotational speed for grinding tool  305 . Controller  330  may be configured to control drive unit  320  in order to rotate one or more grinding tools. Grinding element  310  is configured to be electrically coupled to a cathode of the voltage source  340 , as shown by connection  335   a . Screen  315  is configured to be electrically coupled to a cathode of voltage source  340 , as shown by connection  335   b . Workpiece  360  is configured to be electrically coupled to an anode of voltage source  340 , as shown by connection  345 . According to one embodiment, screen  315  may have a different electric potential than the grinding element  310 . In certain embodiments, screen  315  is insulated from grinding element  310  if there are different potentials. 
     During electrochemical grinding, an electric current generated by voltage source  340  is passed through electrolyte  355 , which may be a small gap (e.g., a 0.001″ gap) between workpiece  360  and grinding tool  305 . According to one embodiment, voltage source  340  can be a DC power supply of 4-14 volts, DC current can be 50-3000 A with current density 500-1500 A/in 2 . 
     System  300  may include nozzle  350  configured to apply the electrolyte  355  in the gap between workpiece  360  and grinding tool  305 . Controller  330  may be configured to control electrochemical grinding by applying an electrolyte in between workpiece  360  and grinding tool  305 . In other embodiments, system  300  may include placing workpiece  360  and grinding tool  305  in a reservoir (not shown) filled with a selected electrolyte and medium. 
       FIG. 4  depicts a process for electrochemical grinding according to one or more embodiments. Process  400  may be employed by a machine/apparatus for grinding, such as the system of  FIG. 3 . Process  400  may include controlling a potential of a voltage source applied to a grinding tool at block  405 . A screen coupled to a grinding element of a grinding tool may be electrically coupled to the cathode of the voltage source and applied a potential. In one embodiment, potential applied to the screen is different than the potential applied to the grinding element. According to another embodiment, controlling potential applied to the grinding tool at block  405  includes measuring at least one of current and potential of an electrolyte solution during electrochemical grinding. 
     At block  410 , potential of the voltage source applied to a workpiece is controlled. 
     At block  415 , electrochemical grinding of the workpiece by the grinding tool is controlled. During electrochemical grinding, the screen is configured to recover material removed by the grinding element during electrochemical grinding. Controlling electrochemical grinding at block  415  can include controlling potential applied to the screen. 
     Controlling electrochemical grinding at block  415  can include applying electrolyte in between a grinding tool and workpiece. In one of embodiment, the electrolyte may be sprayed by a nozzle. In another embodiment, the electrolyte may be applied by placing the workpiece and the grinding tool in a reservoir filled with a selected electrolyte, for example, sodium chloride, sodium nitride and rust inhibitor. A selected electrolyte may depend on material to be ground. Controlling at block  415  may include selecting an appropriate electrolyte and its medium to allow metal ions generated from the workpiece (anode) in the electrochemical grinding process not to form metal hydroxide/metal oxide rather to exist in ions forms or coordinated with other ion groups in the electrolyte medium so the metal ions travel to the cathode side and electroplated on the cathode as the metal. 
     Controlling electrochemical grinding at block  415  can include adjusting one or more of the grinding speed, angle and position of the grinding tool. Positioning the grinding tool and the workpiece may also include leave a gap between the grinding tool and the workpiece, such as a distance is 0.001″ so that the electrolyte can be applied during grinding. 
     Process  400  may optionally determine a condition requiring screen replacement at block  420 . During grinding, metals may accumulate on the screen. During electrochemical grinding process  400 , when excessive metal is plated on the screen, the screen is replaced and the metal may be recycled. 
     While this disclosure has been particularly shown and described with references to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the claimed embodiments.