Abstract:
An electric discharge machine includes a machine base configured to support a work piece, a y-axis alignment assembly having a first direction of travel and mounted to the machine base, and an electrode alignment assembly mounted to the machine base and configured to hold an electrode during a machining process. The electrode alignment assembly has a second, a third, and a fourth direction of travel, and an attached rotary indexer has a fifth direction of travel. Movements in the first, second, third, fourth, and fifth directions of travel are automatically controlled by a processor.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to machining and, more particularly, to using an electric discharge machine to machine a work piece. 
     Electric discharge machining is a process for machining electrical parts and power generation hardware, particularly when high precision is required. High precision machining enhances the efficiency and performance of the parts and work hardware. Precision machining is not only desired for small components, but is needed for larger power generation hardware which is heavy and awkward to handle. 
     Electric discharge machines typically include a working tank in which the work piece is at least partially submerged in a dielectric liquid. Since at least a portion of the work piece is submerged, the physical size of the work piece is limited by the interference of the working tank. Tanks are typically configured to receive light work pieces and are not sized to accommodate large, heavy work pieces. As a result, larger and heavier work pieces must be tooled and machined using manual tooling and machining methods. Such methods are laborious, depend on the skill of the operator, and are expensive and slow. 
     BRIEF SUMMARY OF THE INVENTION 
     In an exemplary embodiment, an electric discharge machine includes a machine base configured to support large and heavy work pieces in comparison to known systems. The machine base includes a y-axis alignment assembly having a first direction of travel and mounted to the machine base, an electrode alignment assembly mounted to the machine base which is configured to receive an electrode during a machining process and has a second, a third, and a fourth direction of travel. Additionally, the machine base includes a rotary indexer configured to support the work piece and moves in a fifth direction of travel. 
     In operation, the electric discharge machine is automatically controlled by a computer which includes a processor for controlling a plurality of servo drives. The servo drives are connected to the y-axis alignment assembly and the electrode alignment assembly and control the movement of the electrode and the work piece in the first, second, third, fourth, and fifth directions of travel. The electric discharge machine eliminates more costly and more complicated known machining equipment and is highly precise, reliable, cost-effective, and is configured for machining large and heavy work pieces. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of an electric discharge machine including a rotary indexer; 
     FIG. 2 is a side view of the electric discharge machine shown in FIG. 1; 
     FIG. 3 is top view of the rotary indexer shown in FIG. 1; and 
     FIG. 4 is a partial side schematic view of a dielectric filtration system used with the electric discharge machine shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is a front view of an electric discharge machine  10  including a rotary indexer  12 , and a machine base  14 . Machine base  14  includes a leveling system  16 , a cabinet  18 , and a worktable  20  mounted to a top  22  of cabinet  18 . Leveling system  16  includes a plurality of leveler pads  24  which extend from cabinet  18  and are attached to cabinet  18  with threaded members  26 . Rotating leveler pads  24  in a counter-clockwise direction causes leveler pads  24  to retract in a direction towards to cabinet  18  and rotating leveler pads  24  in a clockwise direction causes leveler pads  24  to extend away from cabinet  18  towards a floor  26 . As such, leveling system  16  can be adjusted such that worktable  20  is substantially level. 
     Worktable  20  is substantially flat, is mounted to top  22  of cabinet  18 , and is configured to support a work piece (not shown). In one embodiment, worktable  20  is precision lapped and is constructed from granite which provides additional electrical insulation to electric discharge machine  10 . 
     Cabinet  18  includes a front side  29  and a back side (not shown in FIG. 1) which is connected to front side  29  with a pair of side walls  30  and  31 . Cabinet  18  also includes a bottom side (not shown in FIG. 1) and top  22 . Front side  29  includes a pair of doors  32  and  34  which are hingedly connected to front side  29  and which provide access to a cavity area (not shown) formed by front side  29 , side walls  30  and  31 , the back side, the bottom, and top  22 . Cabinet  18  has a first side  36  and a second side  38  and is substantially rectangular in shape. 
     An electrode changer control  40  is mounted adjacent top  22  near cabinet first side  36 . Electrode changer control  40  is electrically connected to an electrode changer  42  mounted to top  22 . Electrode changer  42  is mounted to an electrode changer mounting plate  44  and is electrically connected to an electrode wear indicator (not shown) and to a computer (not shown) including a processor. In one embodiment, electric discharge machine  10  can be programmed off-line. In a further embodiment, electric discharge machine  10  is programmable with a laptop computer. In another embodiment, the processor is a full-featured computerized numerical control (CNC) controller including x-, y-, g-, and z-axis digital read-outs, an alphanumeric keypad, and machining parameter controls available from Current EDM, Inc., 2577 Leghorn Street, Mountain View, Calif. 94043. 
     In operation, the processor receives continuous feedback from an electrode wear indicator (not shown) regarding the useful life of an installed electrode  46  used in a machining process. As electrode  46  deteriorates, the processor signals electrode changer control  40  which activates electrode changer  42  to replace electrode  46  with a new electrode (not shown). In one embodiment, electrode changer  42  is an AEC-24 Automatic Electrode Changer available from Current EDM, Inc. Mountain View, Calif. In one embodiment, electrode  46  is a sixteen-inch diameter electrode. 
     Electrode changer control  40  and electrode changer  42  are electrically connected to a power supply cabinet  50  which is electrically connected to machine base  14 . Power supply cabinet  50  is mounted to cable conduit  52  which is mounted to machine base cabinet  18  near second side  38 . Power supply cabinet  50  shields circuit boards and other internal components (not shown). Power supply cabinet  50  also houses four separate circuit breakers (not shown) which protect machine base  14 . 
     Machine base  14  includes a y-axis alignment assembly  60  and an electrode alignment assembly  62 . Y-axis alignment assembly  60  includes a y-axis mount plate  64  mounted to machine base cabinet  18  in slidable contact with top  22 . Y-axis alignment assembly  60  is configured to move mount plate  64  with respect to cabinet  18  in a substantially linear y-axis direction of travel  66  (not shown in FIG.  1 ). Mount plate  64  is rigid to increase the accuracy of an alignment process and the precision of the machining process. In one embodiment, mount plate  64  is a high-precision, recirculating ball slide available from Current EDM, Inc., Mountain View, Calif. 
     Electrode alignment assembly  62  receives electrode  46  and includes an x-axis alignment assembly  70 , a theta-axis alignment assembly  72 , and a g-axis alignment assembly  74 . Electrode alignment assembly  62  also includes an electrode support assembly  76  which includes a first support  78  and a second support  80 . First support  78  is mounted substantially perpendicularly to cabinet top  22  adjacent a corner (not shown) formed between cabinet side wall  30  and the back side. Second support  80  is mounted substantially perpendicularly to cabinet top  22  adjacent a corner (not shown in FIG. 1) formed between cabinet side wall  31  and the back side. 
     X-axis alignment assembly  70  has a first end  84 , a second end  88 , and an axis of symmetry  90 . X-axis assembly alignment  70  is attached to first support  78  and second support  80  such that axis of symmetry  90  is substantially perpendicular to first support  78  and second support  80 . As such, axis of symmetry  90  is substantially parallel to top  22 . X-axis alignment assembly  70  includes a front surface  92 , a back surface (not shown in FIG. 1) which is connected to front surface  92  with a top surface  94  and a bottom surface  96 , and a pair of side surfaces (not shown in FIG.  1 . Bottom surface  96  is attached to first support  78  and second support  80 . An x-axis drive motor  98  is attached to the side surface near first end  84 . Front surface  92  is in slidable contact with a rotary-axis cover  100  which is electrically connected to x-axis drive motor  98 . X-axis drive motor  98  is electrically connected to the processor and is configured to move rotary-axis cover  100  in a substantially linear x-axis direction  102  which is substantially parallel to axis of symmetry  90 . X-axis alignment assembly  70  includes a pair of limit stop assemblies  104  and  106  which are mounted near first end  84  and second end  88  respectively. Limit stop assemblies  104  and  106  provide a limit to a travel distance  108  that x-drive motor  98  can move rotary-axis cover  100 . In one embodiment, travel distance  108  is equal to approximately  42  inches. X-axis drive motor  98  is electrically connected to a servo drive (not shown) which is electrically connected to the processor. In one embodiment, x-axis alignment assembly servo drive is an AC servo motor available from Current EDM, Inc., Mountain View, Calif. 
     Theta-axis alignment assembly  72  includes a rotary-axis motor  120 , a rotary-axis mount  122 , a rotary-axis assembly housing  124 , and rotary-axis cover  100 . Rotary-axis cover  100  is mounted to x-axis alignment assembly front surface  92  and extends from front surface  92  towards cabinet front side  29 . An adaptor plate (not shown in FIG. 1) is mounted to rotary-axis cover  100 . Rotary-axis assembly housing  124  is mounted to the adaptor plate and houses a rotary drive assembly (not shown). Rotary-axis motor  120  is mounted to a top surface (not shown in FIG. 1) of rotary-axis housing  124  and is electrically connected to power supply cabinet  50 . Rotary-axis motor  120  is configured to move g-axis alignment assembly  74  in a substantially rotary-axis rotational direction  128  about rotary-axis mount  122 . Rotary-axis motor  120  is configured to move g-axis alignment assembly  74  through an angular travel distance  129  or through an angular travel distance  130 . In one embodiment, angular travel distance  129  is approximately 70 degrees, angular travel distance  130  is approximately 70 degrees, and rotary-axis mount  122  is an NSK Model 320 available from NSK Ltd., Precision Machinery &amp; Parts Technology Centre Eng&#39;g. Dept., X-Y Table &amp; Direct-Drive Actuator, 78 Toriba-machi, Maebashi-shi, Gunma-ken 371, Japan. 
     G-axis alignment assembly  74  includes a g-axis support  132 , an electrode holder assembly  134 , and a g-axis motor  136 . G-axis support  132  has a first end  138  and a second end  140 . First end  138  is rotatably attached to rotary-axis mount  122 . Electrode holder assembly  134  is configured to receive electrode  46  and is in slidable contact with a front surface  142  of g-axis support  132 . G-axis motor  136  is configured to move g-axis support  132  in a substantially liner g-axis direction  148  a travel distance  150 . The movement of g-axis support  132  is limited by a first limit switch  152  positioned near first end  138  of g-axis support  132  and a second limit switch  154  positioned near second end  140 . In one embodiment, travel distance  150  is approximately 12 inches. G-axis motor  136  is electrically connected to power supply cabinet  50  and to the processor with interface cables (not shown) which extend through a cable guide  158 . G-axis motor  136  is electrically connected to a servo drive which is electrically connected to the processor. In one embodiment, the g-axis alignment assembly servo drive is available from Current EDM, Inc., Mountain View, Calif. 
     Machine base  14  also includes a rotary indexer  160  mounted to cabinet  18 . Rotary indexer  160  includes a base  162 , a ninety-degree base  164 , and a rotatable platform  166 . Ninety-degree base  164  includes openings  165  and extends substantially perpendicularly from base  162 . Base  162  includes a plurality of fastener assemblies (not shown) which secure base  162  to an insulator  170 . When base  162  is attached to insulator  170 , base  162  and rotatable platform  166  are both substantially parallel to cabinet top  22  and ninety-degree base  164  is substantially perpendicular to cabinet top  22 . In one embodiment, ninety-degree base  164  is secured to insulator  170  with fastener assemblies (not shown) which extend through openings  165 . Insulator  170  is attached to an adaptor plate  172  which is mounted to y-axis mount plate  64 . A dielectric fluid drainage system  174  is attached between insulator  170  and y-axis mount plate  64 . Drainage system  174  collects dielectric fluid (not shown) used in the machining process. In one embodiment, the dielectric fluid is water. Rotatable platform  166  includes a mounting system  180  which is configured to receive a work piece. In one embodiment, rotatable platform  166  is configured to receive work pieces weighing 200-pounds. 
     FIG. 2 is a side view of electric discharge machine  10  including machine base  14 . Machine base  14  includes y-axis alignment assembly  60 , electrode alignment assembly  62 , rotary indexer  160 , and cabinet  18  which includes leveling system  16 . Cabinet  18  also includes front side  29 , a back side  200 , and side walls  31  and  30  (shown in FIG. 1) which connect front side  29  to back side  200 . 
     Electrode changer  42  is mounted to electrode changer mounting plate  44 . Power supply cabinet  50  is electrically connected to machine base  14  and is mounted to cable conduit cabinet  52  which extends from cabinet top  22 . Y-axis alignment assembly  60  is mounted to top  22  and includes y-axis mount plate  64  which is in slidable contact with top  22 . A y-axis drive motor  202  is configured to move y-axis mount plate in a substantially linear y-axis direction  204  and a travel distance  66 . In one embodiment, travel distance  66  is approximately 14 inches. Y-axis drive motor  202  is electrically connected to a servo drive (not shown) which is electrically connected to the processor (not shown). In one embodiment, y-axis alignment assembly servo drive is available from Current EDM, Inc., Mountain View, Calif. 
     Electrode alignment assembly  62  includes electrode support assembly  76  which includes first support  78  (not shown in FIG. 2) and second support  80 . Second support  80  is mounted substantially perpendicular to cabinet top  22  in close proximity to a comer  210  formed between cabinet side wall  31  and back side  200 . X-axis assembly  70  is mounted to electrode support assembly  76  and theta-axis alignment assembly  72  is mounted to x-axis assembly  70 . Theta-axis alignment assembly  72  includes rotary-axis motor  120  mounted to a top surface  206  of rotary-axis assembly housing  124 . Theta-axis alignment assembly  72  also includes rotary-axis mount  122 , rotary-axis assembly housing  124 , and rotary-axis cover  98 . Theta-axis alignment assembly  72  is mounted to an adaptor plate  214  which is mounted to x-axis assembly  70 . 
     G-axis alignment assembly  74  is slidably mounted to theta-axis alignment assembly  72 . G-axis alignment assembly  74  includes g-axis support  132 , electrode holder assembly  134 , and g-axis motor  136 . G-axis motor  136  is configured to move g-axis support  132  travel distance  150  in a g-axis direction  148 . Electrode holder assembly  134  is configured to receive electrode  46  and is in slidable contact with g-axis support  132 . A z-axis motor  216  is configured to move electrode holder assembly  134  with respect to g-axis support  132  a travel distance  218  in a z-axis direction  220  on g-axis support  132 . Z-axis motor  216  is electrically controlled by a servo (not shown). Z-axis direction  216  is substantially parallel to g-axis direction  148   
     In operation, a work piece (not shown) is attached to rotary indexer mounting system  180 . Once the work piece is secured to rotary indexer  160 , the processor (not shown) adjusts the position of the work piece with respect to cabinet  18  by adjusting the servo drives which control the movement of y-axis alignment assembly  60 . Additionally, the processor can change the orientation of the work piece by adjusting the servo drives which control the movement of rotary indexer rotary platform  166 . The position of electrode  46  can also be adjusted by the processor. The processor can automatically adjust the position of electrode  46  by adjusting the servo drives which control the movement of x-axis alignment assembly  70 , theta-axis alignment assembly  72 , and g-axis alignment assembly  74 . After the processor adjusts the position of g-axis alignment assembly  74 , the processor adjusts the position of electrode holder assembly  134  by controlling the servo drive which controls the movement of electrode holder assembly  134 . 
     FIG. 3 is a top view of rotary indexer  160  and includes rotary platform  166  which includes mounting system  180 , and ninety-degree base  164 . A rotary head drive  230  is mounted to rotary indexer  160  and is electrically connected to power supply panel  50  (not shown in FIG.  3 ). Rotary head drive  230  is configured to rotate rotary platform  166  and as such, simultaneously rotates the work piece attached to rotary platform  166 . In one embodiment, rotary head drive  230  is configured to rotate rotary platform  166  approximately 360 degrees in a rotary-axis direction  232  and is an NSK Model 320 available from available from NSK Ltd., Precision Machinery &amp; Parts Technology Centre Eng&#39;g Dept., X-Y Table &amp; Direct-Drive Actuator, 78 Toriba-machi, Maebashi-shi, Gunma-ken 371, Japan. Rotary indexer  160  also includes a first locating pin  234  and a second locating pin  236  which align rotary indexer  160  parallel to x-axis direction  102 . 
     FIG. 4 is a partial side schematic view of a dielectric filtration system  250  including a clean fluid reservoir  252  and a used fluid reservoir  254 . Clean fluid reservoir  252  includes a pair of supply lines  256  and  258  which supply clean dielectric fluid (not shown) to electric discharge machine  10  (shown in FIG.  1 ). Used fluid reservoir  254  includes a pair of return lines  260  and  262  which lead from dielectric fluid drainage system  174  (shown in FIG.  1 ). Dielectric filtration system  250  also includes a water conductivity sensor  264  positioned within an exchange vessel  266 , a pump  268  for transferring the dielectric to electric discharge machine  10 , a filter canister  270  for removing impurities from the dielectric fluid, and an electric pump motor  272  for supplying pressure to pump  268 . 
     The above-described electric discharge machine is cost-effective and highly accurate for machining small work pieces or large and heavy work pieces. The machine is capable of automatically controlling and aligning a work piece in relation to an electrode in five distinct axes. Furthermore, the machine uses positioning assemblies that are more precise and reliable when compared to other known machining systems for use with heavy, awkward, and large work pieces. As such, a cost effective and precise electric discharge machine is provided. 
     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.