Abstract:
A small hole electric discharge machine drill is provided with a depth-specific processor and a tiltable unit operable in fluid. The turntable unit includes a first axis with a first center of rotation and a second tilting axis with a second center of rotation. The turntable unit is provided inside a work tank that may be filled with fluid. The small hole electric discharge machine drill includes an electrode for small hole processing.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a small hole electrical discharge machining method and a small hole electrical discharge machining apparatus. 
     FIG. 1 is a view showing one example of a related small hole electrical discharge machining apparatus  100 . In the small hole electrical discharge machining apparatus  100 , a processing vat  101  filled up with processing fluid is provided on an X-Y table  103 , and a work W is fixed to a jig  105  in the processing vat. 
     Above the processing vat  101 , a rotary spindle  1009  having an electrode  107  attached thereto is provided on a machining head  111 . The machining head  111  is provided so as to be freely moved in a vertical direction (Z axis direction) by a servomotor Mz. Moreover, the rotary spindle  109  is set to be rotatively driven by a motor Ms fixed to the machining head. 
     For example, when a small hole having a diameter of 0.2 mm or less is machined in the related small hole electrical discharge machining apparatus  100 , as shown in FIG. 2, a reverse discharge has been heretofore made to be generated between a rather thick electrode material  113  and a metal block  115  to form an electrode portion  117  having a fine electrode diameter d in accordance with a diameter of a hole to be machined, and the electrode portion  117  has been used as an electrode. 
     SUMMARY OF THE INVENTION 
     However, a length l of the electrode portion  117  is limited to fifth to tenth times the diameter d of the electrode portion  117  due to a factor such as buckling and vibration of the electrode portion  117  during machining. Hence, in the discharge machining in which an electrode corrodes away, there is a problem that the number of holes which can be continuously machined is small. 
     Moreover, in fabricating the electrode portion  117  by the reverse discharge, since corrosion of the metal block  115  cannot be completely eliminated, it is essential to confirm a finished dimension of the electrode diameter d. For confirming the dimension, the electrode  107  is detached from the rotary spindle  109 , and measurement thereof by use of a microscope and the like is repeated. Thus, the electrode portion is finished in a desired dimension. Therefore, productivity in the small hole electrical discharge machining is not enhanced. 
     The present invention was made in order to solve the problem as described above. An object of the present invention is to provide a small hole electrical discharge machining method capable of using a thin and long stick-shaped electrode, for which fabrication of an electrode tip thereof is not required, and a small hole electrical discharge machining apparatus having high productivity. 
     As means for achieving the above-described subjects, the small hole electrical discharge machining method of the present invention is a method_for a small hole electrical discharge machining apparatus including an electrode holding member for holding an upper portion of a stick-shaped or pipe-shaped electrode, and an electrode guiding member for guiding a lower portion of the electrode. Moreover, the electrode holding member is provided with a jet nozzle for generating a water jet. The method is characterized in that the electrode is fed to a work while being rotated simultaneously when the electrode is guided by use of the water jet. 
     Moreover, a small hole electrical discharge machining apparatus of the present invention is characterized by including: a slide base; a Z axis slide freely positionable in a verticle direction, the Z axis slide being provided on the slide base; an electrode holding member for holding an upper portion of a stick-shaped or pipe-shaped electrode, the electrode holding member being provided on the Z axis slide so as to be freely rotatable; an electrode guiding member for guiding a lower portion of the electrode, the electrode guiding member being provided on the slide base; and an electrode member, the electrode motor being provided on the Z axis slide. In the apparatus, the electrode holding member is provided with a jet nozzle for guiding the electrode by use of a water jet. 
     Moreover, in the small hole electrical discharge machining apparatus, the electrode guiding member is characterized by including; a guide unit provided with an electrode guide made of ceramics; a guide unit provided with an electrode guide made of ceramics; a funnel for guiding the water jet to a center of the guide unit; and a splash preventing member for preventing splash of the water jet. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view showing one example of a related small hole electrical discharge machining apparatus. 
     FIG. 2 is an explanatory view showing a shape of a fine electrode and a method of manufacturing the same in the related small hole electrical discharge machining apparatus. 
     FIG. 3 is a front view of a small hole electrical discharge machining apparatus according to the present invention. 
     FIG. 4 is a right side view of the small hole electrical discharge machining apparatus according to the present invention. 
     FIG. 5 is an enlarged view of a Z axis slide portion in FIG.  4 . 
     FIG. 6 is an enlarged explanatory view of the portion VI in FIG.  5 . 
     FIG. 7 is a sectional view of a collet in FIG. 6, taken along a line VII—VII. 
     FIG. 8 is an enlarged explanatory view of a portion VIII in FIG.  5 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, description will be made for an embodiment of the present invention with reference to the drawings. 
     FIGS. 3 and 4 are a front view and a side view of a small hole electrical discharge machining apparatus according to the present invention, respectively. A worktable  5  for fixing a work W thereon is provided on a pedestal  3  of a small hole electrical discharge machining apparatus  1 . On the worktable  5 , a processing vat  7  for accommodating the work W therein is provided. Moreover, on the rear side of the worktable  5  (right side in FIG.  4 ), columns  9   a  and  9   b  extending upward from the worktable  5  are provided. 
     On the above-described columns  9   a  and  9   b , an X axis carriage  11  freely movable and positionable in an X direction (right-and-left direction in FIG. 3) is provided. Moreover, on the X axis carriage  11 , a Y axis carriage  13  freely movable and positionable in a Y direction perpendicular to the X direction is provided. 
     With reference to FIG. 4, a slide base  17  is engaged with a front end (left-side end in FIG. 4) of the above-described Y-axis carriage  13  so as to be vertically movable. With reference to FIG. 5, a Z axis slide  19  is engaged with the slide base  17  by an unillustrated guide so as to be freely movable vertically. 
     A shaft of a Z axis feed screw  21  extending in a Z direction is supported on the slide base  17  so as to be freely rotatable. On an upper end of the Z axis feed screw  21 , a servomotor  23  for rotatably driving the Z axis feed screw  21  is provided. Moreover, a nut  24  fitted to the Z axis slide  19  is screwed to the Z axis feed screw  21 . 
     Hence, the Z axis screw  21  is rotatively driven in an appropriate manner by the above-described servomotor  23  under control of an unillustrated control device, whereby the Z axis slide  19  can be moved to a desired position in the Z direction. 
     On a lower portion of the above-described Z axis slide  19 , an electrode holding  27  provided with one-touch coupler  25  is provided so as to be freely rotatable. Moreover, to the electrode holding member  27 , a hollow rotation shaft  29  extending to the upper portion of the Z axis slide  19  is fixed with the one-touch coupler  25  interposed therebetween. On the upper end of the rotation shaft  29 , a pulley  31  such as a timing pulley for driving a rotation shaft is provided. Moreover, the upper end of the hollow rotation shaft  29  is coupled to an unillustrated water supply device via a pipeline  35  with a rotary joint  33  interposed therebetween. Moreover, the pulley  31  is coupled to a drive pulley (not shown) provided in the electrode motor  37  for rotating an electrode via a drive belt (not shown). 
     Hence, water supplied from the water supply device will be supplied through a hollow portion of the hollow rotation shaft  29  to the electrode holding member  27 . Moreover, the electrode holding member  27  can be rotatively driven by the electrode motor  37  for rotating the electrode. 
     Below the electrode holding member  27 , an electrode guiding member  41  for guiding a tip of a stick-shaped or pipe-shaped electrode  39  is provided. The electrode guiding member  41  is fixed to a support plate  43  provided integrally on the lower end of the slide base  17  by a fastening member  45  such as a bolt. 
     For example, even a stick-shaped or a pipe-shaped electrode having a fine line diameter of about 0.030 mm to 0.200 mm can be fed to the electrode guiding member without being bent by a reaction force due to friction between the electrode and the above-described electrode guide. 
     As shown in FIG. 6, the electrode holding member  27  includes a collet  47  for holding the end of the fine stick-shaped or pipe-shaped electrode  39 . The collet  47  is detachably inserted into a collet holding for the end of the fine stick-shaped or pipe-shaped electrode  39 . The collet  47  is detachably inserted into a collet holding hole  51  open downward, which is provided in a collet holder  49  for holding the collet  47 . Moreover, in the collet holding hole  51 , a water path  53  communicating with a hollow hole of the rotation shaft  29  is provided. 
     Between the upper portion of the collet holding hole  51  and the collet  47 , a ring spacer  55  having an approximately equal diameter to that of the collet  47  is inserted. Moreover, inside the ring spacer, a reserve chamber  57  for reserving water from the water path  53  is defined. 
     As shown in FIGS. 6 and 7, on an outer circumference of the collet  47 , four water grooves  59  communicating with a tip  47   h  of the collet  47  and the reserve chamber  53  is defined. 
     Note that, in the tip  47   h  of the collet  47 , cross-shaped cut grooves  63  reaching a chuck hole  61  of the collet  47  is provided so that the tip  47   h  can be elastically deformed readily. Moreover, on a lower outer circumference of the collet holder  49 , a talon-shaped engaging portion  65  abutting on the lower end of the one-touch coupler  25  is provided. 
     On the lower end of the collet holder  49 , a collet fixing member  67  that is engaged with a tapered portion of the tip of the collet  47  and tightens the collet  47  is provided. The collet fixing member  67  includes a female screw  71  screwed to as male screw  69  in the lower end of the collet holder  49 . The collet fixing member  67  is rotated, thus making is possible to release or fix the collet  47 . 
     Moreover, in the above-described collet fixing member  67 , a jet nozzle  73  is provided, which turns water flown out downward from the four water grooves  59  of the collet  47  into a water jet WJ and injects the water jet WJ so that the water can surround the stick-shaped or pipe-shaped electrode  39 . 
     Meanwhile, as shown in FIG. 8, in the electrode guiding member  41 , a guide unit  75  for vertically guiding the lower end of the stick-shaped or pipe-shaped electrode  39  attached to the electrode holding member  27  is provided. The guide unit  75  is fabricated by forcibly inserting an electrode guide  77  made of ceramics into a support  79  made of a material having high tenacity e.g., metal). In the guide unit  75 , a weak point of the ceramics is supplemented, in that the ceramics is frangible though the ceramics has high abrasion resistance. 
     Moreover, in the upper portion of the above-described guide unit  75 , a funnel portion  83  for collecting a water stream into a guide hole  81  is provided. Note that an outer diameter of the upper portion of the guide unit  75  is set to be somewhat larger than that of the lower portion thereof. 
     The above-described guide unit  75  is attached to a guide holder  85  so that a step portion of the guide unit  75  is allowed to abut on the bottom of the guide holder  85 . 
     Moreover, on an upper portion of the guide unit  75 , a splash preventing member  91  for preventing splash of the water jet WJ on the periphery is provided so as to be detached from the guide holder  85 . 
     The splash preventing member  91  includes a funnel  93  for guiding the water jet WJ to the center of the guide unit  75  and a cover unit  95  for turning downward the water splashing upward on the funnel  93 . Moreover, in the cover  95 , a plurality of drain holes  97  for draining the water reflected on the upper portion of the cover are provided. 
     In order to attach the splash preventing member  91  to the guide holder  85 , a female screw is provided on the upper portion of the attachment hole  87  of the guide holder  85 , and a male screw screwed to the female screw is provided on an outer circumference of the funnel  93 . Hence, the guide unit  75  can be fixed with pressure to the guide holder  85  simultaneously when the splash preventing member  91  is screwed to the guide holder  85 . 
     Note that the above-described guide holder  85  is fitted to the support plate  43  provided integrally with the slide base  17 . Moreover, for the fluid for guiding the stick-shaped or pipe-shaped electrode  39 , processed oil for use in the electrical discharge machining can be also used. 
     In the case where the small hole is subjected to electrical discharge machining in the electrical discharge machining device constituted as described above, when the upper portion of the stick-shaped or pipe-shaped electrode  39  is attached to the collet  47  of the electrode holding member  27 , and water is fed from the water supply device to the electrode holding member  27 , then the water passes through the reserve chamber  57  of the electrode holding member  27  and the water grooves on the outer circumference of the collet  47 , and the water jet surrounding the circumference of the electrode is injected from the jet nozzle  73 . Thus, it is made possible to straightly guide the stick-shaped or pipe-shaped electrode  39  from the electrode holding member to the electrode guiding member  41 . 
     Moreover, since the electrode is surrounded by the water jet, flexure (jump rope phenomenon) of the electrode generated due to the rotation of the electrode can be suppressed, and high-precision small hole machining can be carried out. In addition, fusion cutting of the electrode due to heating caused by the electrical discharge machining can be prevented. 
     Note that, since a thin and long stick-shaped electrode can be used, for which fabrication of an electrode tip thereof is not required, productivity in the small hole electrical discharge machining can be improved. In this embodiment, machining can be carried out under conditions where the line diameter of the electrode is 0.070 mm and the length thereof is about 220 mm.