Electrospark machine system, assembly for use with system, device for mounting electrospark machining electrode, and method of shaping a workpiece

An electrospark machining system which includes an electrode forming machine which machines an electrode blank into a shaped electrode having a desired profile, an electrospark machine to which the shaped electrode is attached in order to machine a workpiece, and a reference block which is adapted to be attached to the electrode blank and which has a reference surface which can be commonly attached to the electrode forming machine and to the electrospark machine. A method of shaping a workpiece using this system is also provided.

BACKGROUND OF THE DISCLOSURE 
1. Technical Field of the Invention 
The present invention generally relates to an electrospark machining 
system, a device for mounting an electrospark machining electrode, and a 
method of using an electrospark machining system, and more specifically to 
a system which eliminates the need for using a surface of an electrode 
blank as a reference surface when an electrode blank is formed into a 
shaped electrode and during the electrospark machining of a workpiece 
using the thus-shaped electrode. 
2. Description of Relevant Information 
Electrospark machines and electrodischarge machines (also known as EDM 
machines) are presently widely used, e.g., to manufacture high precision 
molding dies for injection molding machines; these electrospark machines 
are used because of their high machining efficiency. In these systems, the 
shape of a shaped electrode is accurately reproduced on a workpiece to be 
machined. Generally, a blank from which the electrode is formed is 
machined by a wire cut electric spark machine, a cutting machine, or other 
machine tool, in order to provide a shaped electrode having a desired 
shape. 
A molding die having a simple profile can be machined, e.g., by a single 
shaped electrode. However, a molding die having a complex profile cannot 
be machined by only a single, shaped electrode. Specifically, such a 
complex molding die can instead only be machined by a composite machining 
system, using a plurality of shaped electrodes. 
Generally speaking, the number of shaped electrodes used in a composite 
machining process can be reduced or decreased if shaped electrodes having 
three-dimensional complex profiles could be produced and used. However, in 
practice, an increased plurality of shaped electrodes are needed to 
produce shaped electrodes having complex three-dimensional profiles, 
thereby resulting in an apparatus which would be difficult to maintain. 
During the conventional machining process of a shaped electrode, six faces 
of a rectangular parallelepipedic electrode blank are ground in order to 
provide six reference surfaces which are perpendicular to each other. The 
electrode blanks can be attached to an electrode forming machine, e.g., a 
wire cut electric spark (hereinafter electrospark) machine, with the 
assistance of the reference surfaces on the blank. When the electrode 
blank is subjected to a two- or three-dimensional machining process, the 
reference surfaces must be changed in order to again attach the blank to 
the electrode forming machine. 
In such a conventional machining process, as noted above, it is necessary 
to adjust the mounting position of the electrode blank, including but not 
being limited to centering the blank, and/or creating parallelism or 
perpendicularity between the reference surface or surfaces and the surface 
being machined at each change of direction during the machining process. 
The operations needed to make such adjustments are difficult and 
troublesome. Accordingly, it is practically impossible to obtain a shaped 
electrode having a three-dimensional complex profile using conventional 
methods. Accordingly, during an actual machining process, the molding dies 
are machined by a composite machining device in which a large number of 
shaped electrodes having simple profiles are used. 
The above-noted problems also occur during a machining process using an 
electrospark machine having a shaped electrode attached thereto. 
Specifically, when the shaped electrode is transferred from the electrode 
forming machine to the electrospark machine, unless the positional 
relationship of the electrode with respect to the electrode forming 
machine is exactly reproduced between the electrode and the electrospark 
machine, precise and exact machining by the electrospark machine cannot be 
achieved. In conventional processes, it is extremely difficult to exactly 
reproduce the identical positional relationship that the electrode had 
with respect to the electro forming machine when the electrode is 
positioned in the electrode spark machine; accordingly, the troublesome 
and difficult adjusting operations as noted above, e.g., the centering 
operation, must be effected after the electrode is transferred to the 
electrospark machine. Further, even after such an adjustment is made, an 
accurate reproduction of the positional relationship between the electrode 
and the electrode forming machine, on the electrospark machine, cannot be 
ensured. 
One type of shaped electrode is used in which the direction of displacement 
of the electrode during the course of electrospark machining of a 
workpiece is perpendicular to the direction of machining of the electrode 
blank. Using this type of shaped electrode, in conventional processes, the 
shaped electrode is first machined by the electrode forming machine and 
removed from the electrode forming machine. Thereafter, the shaped 
electrode is attached to the electrospark machine after the direction of 
the electrode is changed by 90.degree.. It is, however, difficult to 
accurately set the electrode again in the electrospark machine. The 
failure to accurately position the electrode in the electrospark machine 
results in a failure to accurately reproduce the shape of the shaped 
electrode on a workpiece being shaped. 
SUMMARY OF THE INVENTION 
Accordingly, one primary object of the present invention is to provide a 
system for machining an electrode in which a blank of an electrode can be 
machined into a shaped electrode having a predetermined shape without 
using any reference surface on the electrode blank itself. 
Another object of the present invention is to provide an electrospark 
machining system in which, when the workpiece is machined by a shaped 
electrode during an electrospark machining method, the direction of 
electrospark machining can be easily controlled in order to correspond to 
the direction of machining of the blank of an electrode into the shaped 
electrode. 
Still another object of the present invention is to provide a mounting for 
an electrode which can be advantageously used, particularly when the 
direction of machining of the electrode blank into a shaped electrode is 
perpendicular to the direction of electrospark machining of a workpiece 
using the shaped electrode obtained when the electrode blank was machined. 
Unlike conventional electrode forming methods, in which it is necessary to 
provide and use one or more reference surfaces on the electrode blank 
itself in order to mount the electrode blank to an electrode forming 
machine with the assistance of such reference surface or surfaces, the 
present invention includes the novel idea of using a separate reference 
block having three reference surfaces which are normal or perpendicular to 
each other. Specifically, in the present invention, a separate reference 
block is mounted to the electrode blank so that the electrode blank can be 
attached to an electrode forming machine and to an electrospark machine by 
using the reference surfaces of the reference block. In its simplest form, 
e.g., the reference block comprises a rectangular block having three 
reference surfaces which are normal to each other. Preferably, holders 
which are attached to the electrode forming machine, e.g., a wire cut 
electrospark machine used to form an electrode, and to the electrospark 
machine for machining a workpiece (with the use of a shaped electrode thus 
produced by the electrode forming machine), include reference grooves 
which can be engaged by reference surfaces of the reference block in order 
to hold the reference block in a predetermined position on the machines. 
With such an arrangement, in accordance with the present invention, the 
three-dimensional positions of an electrode can be definitely and 
precisely determined by a reference block having three reference surfaces 
which are normal to each other; and, accordingly, it is possible to 
machine an electrode having a complex three-dimensional profile. Such an 
electrode can be formed without any need for performing any adjusting 
operation, e.g., there is no need to adjust for surface parallelism, 
perpendicularity or for centering. Such an adjusting operation would 
otherwise (normally) need to be performed when the direction of machining 
of the electrode is changed by the electrode forming machine. As a result, 
no positional adjustments are necessary in accordance with the present 
invention, either when electrode machining operations occur in different 
directions, or when the electrode is positioned in an electrospark 
machine. 
Further, because no centering operations need be performed during a complex 
machining operation in which a plurality of shaped electrodes are used, 
molding dies having complex profiles can be machined with high precision, 
thereby resulting in the increased applicability of the electrospark 
machining system and method. 
Further, in accordance with the present invention, because 
three-dimensional machining of an electrode can be effected, the number of 
shaped electrodes needed to produce a large number of identical molding 
dies can be decreased, thereby resulting in decreased costs for 
maintaining the shaped electrodes. 
The reference block which is used can be, e.g., a rectangular block; and 
holders used in the machinery can have reference grooves which are 
complementary in shape to the shape of the reference block. As one 
example, both the holder groove, and the block itself, can be 
substantially V-shaped. 
The present invention can also be advantageously used when the direction of 
machining of the electrode blank in the electrode forming machine is 
changed; and the later direction of machining of a workpiece generally 
corresponds to the direction of displacement of the shaped electrode. 
Accordingly, a mounting device according to the present invention is 
provided which includes a machine holder which can be detachably connected 
to the electrode forming machine and to the electrospark machine which 
machines the workpiece by using the shaped electrode obtained by the 
electrode forming machine. The machine holder is adapted to be engaged by 
an electrode holder which holds the electrode blank, with rotational 
surfaces being provided on both the electrode forming machine holder and 
the electrospark machine holder, which surfaces are inclined at 45.degree. 
with respect to the axis of the machine holder. Relative rotation of the 
machine holder with respect to the electrode holder over the rotational 
surfaces, by 180.degree., causes the position of the electrode blank which 
is secured to the electrode holder to be changed by 90.degree. with 
respect to the machine holder. In accordance with the mounting device 
referred to above, only rotation of the electrode holder by 180.degree. 
with respect to the machine holder will be sufficient to orient the 
electrode blank, (i.e., the shaped electrode) to agree with the direction 
of electrospark machining after the electrode blank is machined into the 
shaped electrode by the electrode forming machine. 
In a first aspect thereof, the present invention provides an electrospark 
machining system including an electrode forming machine comprising means 
for machining an electrode blank in order to produce a shaped electrode 
having a predetermined profile, an electrospark machine to which the 
shaped electrode is adapted to be attached in order to machine a workpiece 
and a reference block having a plurality of surfaces, the reference block 
being adapted to be attached to the electrode blank and having at least 
one surface which serves as a common reference surface for the electrode 
forming machine and the electrospark machine. 
The system further comprises at least one holder which is detachably 
connected to the electrode forming machine and at least one holder which 
is detachably connected to the electrospark machine, the holders having 
mounting surfaces which are adapted to detachably engage the reference 
surface of the reference block in order to retain the reference block in a 
predetermined position within the machines. 
The reference block includes a parallelepipedic insertion section having 
three reference surfaces which are perpendicular to each other, each of 
the electrode forming machine holder and the electrospark machine holder 
comprising means for engaging the three surfaces of the insertion portion 
of the reference block and means for supporting the reference block in a 
predetermined position in the machines. 
Each of the holders includes at least two planar surfaces which are 
perpendicular to each other, one of the planar surfaces being provided 
with two intersecting grooves and the other of the planar surfaces 
including at least one groove. 
The intersecting grooves of the forming machine holder comprise means for 
detachably engaging the reference block insertion portion, and the at 
least one groove comprises means for detachably engaging an electrode 
forming tool. 
The system can also include an electrode forming tool attached to a work 
table of the electrospark machine, the electrospark machine holder being 
adjustably supported on the electrode forming tool. The electrospark 
machine holder includes a substantially vertical guide rail which is 
slidably engaged by the at least one groove. Each of the holders includes 
a shaft for respectively mounting the holders to the electrode forming 
machine and to the electrospark machine. 
The shafts are substantially cylindrical, and each includes an outwardly 
extending, rotation restricting pin thereon. The reference block includes 
a reference insertion portion having three reference surfaces which are 
normal to each other, each of the holders including at least one reference 
groove which is adapted to be selectively engaged with a reference surface 
on the reference block to thereby comprise means for supporting the 
reference block in a predetermined position on the holder. 
Each of the holders includes an integrally attached mounting shaft which 
comprises means for mounting the holders on the electrode forming machine 
and on the electrospark machine, respectively; and each of the holder 
reference grooves is substantially perpendicular to the mounting shaft. 
Each of the holders includes a reference surface which comprises means for 
mounting the holders, respectively, to the electrode forming machine and 
to the electrospark machine; the holder reference surfaces are alternately 
spaced from, and attached to, the at least one reference groove, by a 
connecting shaft portion. 
The reference block and each of the holders can includes a plurality of 
positioning holes and a plurality of positioning pins adapted to be 
inserted into the positioning holes in order to secure the reference block 
to the holders. The reference block can include the positioning holes, and 
the holders include the positioning pins; or the reference block can 
include the positioning pins and the holders the positioning holes. 
Each of the holders includes a mounting shaft integrally attached thereto 
which comprises a reference surface for mounting respective holders to the 
electrode forming machine and to the electrospark machine. 
The holders include reference grooves which are perpendicular to the 
mounting shaft, and the holders can include a mounting surface which 
comprises a reference surface for mounting the holders to both the 
electrode forming machine and to the electrospark machine. 
The reference block includes a reference insertion portion having three 
reference surfaces which are substantially normal to each other, and a 
blank securing portion adapted to be attached to the electrode blank, the 
electrode blank securing portion being normal to the reference insertion 
portion, the reference block thereby being substantially L-shaped. 
The reference block includes a reference insertion portion having three 
reference surfaces which are substantially normal to each other, and a 
blank securing portion adapted to be secured to the electrode blank, the 
blank securing portion lying in the same plane as the reference insertion 
portion, wherein the reference block is substantially I-shaped. 
The electrode forming machine itself can comprise a wire cut electrospark 
machine. 
An assembly is provided which includes a reference block having three 
reference surfaces which are substantially normal to each other, the 
reference surfaces comprising position references during the shaping of an 
electrode blank, the reference block being adapted to be attached to the 
electrode blank, the assembly further comprising a holder which is adapted 
to be attached to an electrode forming machine, the holder including a 
mounting surface for mounting and for retaining the reference block in a 
predetermined position. 
The reference block is connected to the electrode blank, and includes a 
reference insertion portion, the reference insertion portion including 
three reference surfaces which are substantially normal to each other, the 
holder including at least one reference groove which is adapted to engage 
the reference surfaces, the groove thereby comprising means for retaining 
the reference block in the predetermined position. 
The electrode forming machine holder includes three reference grooves which 
are substantially normal to each other. 
Two of the grooves are normal to each other within a common plane, and a 
third of the grooves is located in a plane perpendicular to the common 
plane. 
The electrode forming machine comprises a wire cut electrospark machine, 
and the electrode forming machine holder is adjustably attached to a work 
table of the wire cut electrospark machine. 
The holder includes two planar surfaces, substantially normal to each 
other, one of the planar surfaces including two reference grooves which 
intersect each other, and the other of the planar surfaces including a 
single reference groove. 
The holder includes a mounting shaft which comprises a reference surface 
for mounting the reference block to the electrode forming machine, or the 
holder includes a mounting surface for mounting the reference block to the 
electrode forming machine. 
The holder includes a single reference groove, and the holder is attached 
to a mounting shaft, the shaft comprising a reference for mounting the 
holder to the electrode forming machine. 
The holder reference groove is substantially perpendicular to the mounting 
shaft, and the holder is secured to a mounting support, the mounting 
support having a reference surface which comprises a reference for 
mounting the holder to the electrode forming machine. 
The reference block includes a reference insertion portion which has three 
reference surfaces substantially normal to each other, and an electrode 
blank securing portion which is substantially perpendicular to the 
inserting portion, the reference block being thereby substantially 
L-shaped. 
The reference block includes a reference insertion portion having three 
reference surfaces substantially normal to each other and an electrode 
blank securing portion which is positioned in the same plane as the 
reference insertion portion, the reference block thereby being 
substantially I-shaped. 
The reference block and the holder include a plurality of cooperating 
positioning holes and pins which are adapted to attach the reference block 
to the holder. 
The holder is attached to an electrode forming machine, and the holder 
includes a reference groove which is substantially perpendicular to a 
mounting shaft on which the holder is mounted. 
The holder is attached to a mounting member having a reference surface 
which comprises a reference for mounting the holder to the electrode 
forming machine. 
In yet another aspect, the present invention provides an electrospark 
machine. This machine uses a mounting device which comprises an electrode 
holder which is adapted to support an electrode blank to be machined. A 
machine holder is adapted to be detachably mounted, both to an electrode 
forming machine for machining the electrode blank into a shaped blank 
having a desired shape and to an electrospark machine which is adapted to 
use the shaped electrode to machine a workpiece, wherein the electrode 
holder and the machine holder include inclined surfaces which are inclined 
at a substantially 45.degree. angle with respect to an axis of the machine 
holder, wherein the holders are adapted to engage each other along the 
surfaces, the inclined surfaces being moveable with respect to each other 
and thereby comprising means for changing the direction in which the 
electrode blank extends. 
The inclined surfaces are rotatable with respect to each other and comprise 
means for changing the direction in which the electrode blank extends by 
90.degree. when they are rotated over 180.degree. with respect to each 
other. The electrode holder and the machine holder are detachably 
connected to each other. The inclined surfaces are electrode-direction 
changing, rotational surfaces which are adapted to rotate about an axis 
inclined at an angle of substantially 45.degree. with respect to the axis 
of the machine holder. 
The surfaces have central holes, along their respective axes of rotation, 
into which a central pin is adapted to be inserted in order to define a 
common axis about which relative rotation of the holders will occur, the 
central pin including a central bore into which a fastening bolt is 
adapted to be inserted in order to secure the holders to each other. 
At least one of the machine holder and the electrode holder is provided 
with a positioning plate which is adapted to project towards the holder to 
which the plate is not attached, the other of the holders being provided 
with a pair of parallel position restricting surfaces which are adapted to 
engage the positioning plate when the electrode holder and the machine 
holder are angularly displaced, from a first position, by 180.degree. with 
respect to each other. 
A positioning pin is positioned between the electrode holder and the 
machine holder which comprises means for selectively restricting angular 
movement between the holders. 
The machine holder and the electrode holder include at least one position 
restricting projection and at least one position restricting recess 
adapted to receive the projection in fitting engagement, the projection 
and the recess being positioned on the inclined surfaces such that they 
intersect an axis of the machine holder. 
The position restricting projection and the position restricting recess can 
be rectangularly shaped in cross-section, or the position restricting 
projection and the position restricting recess can have complementary 
V-shaped cross-sections. 
One of the holders includes a positioning plate which projects towards the 
other of the holders, the other of the holders including a pair of 
parallel position restricting surfaces which are adapted to engage the 
positioning plate, dependent upon the relative rotational positions of the 
two holders. 
One of the inclined surfaces includes two spaced apart bores and the other 
of the inclined surfaces includes a single bore, wherein the single bore 
is adapted to be selectively aligned with each of the spaced apart bores 
in predetermined positions of the holders, and wherein a fastening member 
is adapted to be inserted into the aligned bores. 
The mounting device includes an electrode holder which is adapted to 
support a blank of an electrode to be machined, and a machine holder which 
is adapted to be attached both to an electrode forming machine which is 
adapted to machine the blank into a shaped electrode having a 
predetermined shape and to an electrospark machine which is adapted to use 
the shaped electrode to machine a workpiece, the electrode holder and the 
machine holder including surfaces which are inclined at 45.degree. with 
respect to the axis of the machine holder and which are adapted to engage 
each other, the inclined surfaces comprising means for changing the 
position of the electrode blank by approximately 90.degree. when the 
surfaces are repositioned with respect to each other over approximately 
180.degree., wherein one of the holders is provided with a positioning 
plate which is adapted to be selectively projected towards and retracted 
from the other of the holders, wherein the other of the holders includes a 
pair of parallel position restricting surfaces which are adapted to engage 
the positioning plate when it is projected towards the other holder. 
The inclined surfaces are repositioned by rotation and thereby rotatably 
engage each other and are rotatably repostioned with respect to each 
other. 
The electrode holder includes a pair of electrode securing surfaces which 
are perpendicular to each other and which are angled at substantially 
45.degree. with respect to the inclined surface of the electrode holder; 
and the electrode securing surfaces of the electrode holder include a 
plurality of threaded holes which are adapted to threadably receive a 
plurality of fastening bolts. 
In another aspect, the present invention discloses a method of shaping a 
workpiece in a predetermined configuration by using an electrospark 
machining electrode. The method comprises mounting an electrode blank to 
be shaped onto a block having a reference surface, attaching the block 
reference surface to an electrode forming machine, shaping the blank into 
a predetermined shape by using the electrode forming machine, detaching 
the block and blank from the electrode forming machine and attaching the 
block reference surface to an electrospark machine, and shaping a 
workpiece by using the electrospark machine to which the blank has been 
attached. 
The method further comprises attaching the block reference surface to a 
holder on the electrode forming machine and to a holder on the 
electrospark machine. The reference surface is attached in the same 
positional relationship to each of the holders. 
In another aspect, the present invention provides a holder which is adapted 
to be detachably connected to both an electrode forming machine and to an 
electrospark machine, the holder comprising a substantially 
parallelepipedic block, the block comprising four side surfaces, an upper 
surface, and a lower surface, wherein four corner projections extend 
upwardly from the upper surface, each of the corner projections being 
spaced from two adjacent corner projections, wherein a plurality of 
substantially perpendicular grooves are formed between the spaced corner 
projections, one of the side surfaces including a channel which is adapted 
to be attached to an electrode forming machine. 
At least one position limiting member is attached to a side wall of the 
reference block and extends upwardly beyond the upper surface of the 
block; and each of the grooves comprises means for detachably receiving a 
portion of a reference block to which an electrode blank to be shaped is 
attached. 
In still another aspect, the present invention provides an assembly 
comprising an electrode blank to be shaped and a reference block which is 
adapted to be attached to the electrode blank, with the assembly being 
adapted to be attached to either an electrode forming machine or to an 
electrospark machine. The block has a plurality of bores which are adapted 
to be aligned with corresponding bores on one surface of the electrode 
blank, and fastening means adapted to be inserted into the respective 
bores to connect the reference block to the electrode blank. 
The reference block can be substantially parallelepipedic, or can be 
substantially L-shaped. 
The electrode blank can be substantially cylindrical, and the reference 
block can comprise a hollow tube which includes an opening which is 
adapted to receive one end of the electrode blank. 
The reference block is substantially parallelepipedic and includes a 
central circular opening which comprises means for receiving a projection 
on a holder which is adapted to be connected to both an electrode forming 
machine and to an electrospark machine. 
A holder is adapted to detachably engage the assembly; the holder includes 
means for releasably engaging a reference surface of the reference block. 
The holder can comprise a plurality of intersecting grooves for releasably 
engaging the reference block, or can comprise only a single groove for 
releasably engaging the block. 
Alternately, the holder and the reference block include a plurality of 
aligned bores, with the assembly further comprising a plurality of 
fastening elements inserted into the bores to attach the holder to the 
block. A shaft can be attached to the holder, or a mounting member with a 
reference surface can be attached to the holder.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring more specifically to the drawings, FIGS. 1A and 1B illustrate a 
reference block 10 and an electrode blank 20 attached thereto. Normally, 
different types of electrode blanks 20 in the form of rectangular 
parallelepipeds are prepared in accordance with the intended shape of the 
shaped electrode to be formed. In the illustrated embodiments, reference 
blocks 10A and 10B, of L-shape and I-shape, respectively, are prepared in 
accordance with the shapes of the portions of the electrode blank which 
are to be machined. Each of the reference blocks 10A and 10B has at one 
end a reference insertion portion 13 which includes a butt or end surface 
(x), a pair of lateral restrictive or defining surfaces (y), which 
surfaces are spaced a distance (l) from each other, and a pair of 
longitudinal defining surfaces (z) which are spaced a distance (s) from 
each other. Surfaces (x), (y) and (z) are reference surfaces which are 
perpendicular or normal to each other and which are machined and precisely 
finished, by using a block gauge level, to provide surfaces with a high 
degree of flatness, and which are accurately and precisely parallel or 
perpendicular with respect to each other, dependent upon which surfaces 
are being referred to. 
In particular, it is important that widths (l) and (s), and most 
particularly width (s), be accurately formed. 
Reference insertion portion 13 is provided with an insertion hole 14 into 
which a setting bolt 101 is adapted to be inserted in order to secure the 
reference block 10 to a holder 30 (see FIG. 2). Insertion hole 14 is 
provided with a diameter which is slightly larger than that of the setting 
bolt such that a slight (but secure) clearance is provided between setting 
bolt 101 and the interior surface of insertion hole 14. 
Each of the respective L-shaped and I-shaped reference blocks 10A and 10B 
is provided with a blank securing portion 15 which is provided with 
mounting holes 16 to mount on electrode blank 20 (via, e.g., conventional 
bolts or other fasteners 11). Blank securing portion 15 of L-shaped 
reference block 10A is perpendicular to the surface insertion portion 13; 
on the other hand, blank securing portion 15 of I-shaped reference block 
10B is connected to reference insertion portion 13 along the same plane. 
Mounting holes 16 are provided as either threaded holes or through-holes 
which are adapted to secure blank 20 to securing portion 15 of reference 
block 10 via fasteners 11. Electrode blank 20 includes threaded holes (not 
illustrated) into which conventional setting bolts, e.g. bolts 11, which 
are also inserted into mounting holes 16 are adapted to be screwed in 
order to secure a block to the electrode blank. 
Holders 30 are prepared for use in an electrode forming device, as 
illustrated in FIG. 2, and for use in an electrospark machine, as shown in 
FIGS. 3 and 4. As illustrated in FIG. 2, each holder 30 is adapted for use 
in an electrode forming tool 40, i.e., in a wire cut electrospark machine 
which is widely used as an electrode forming device. Electrode forming 
tool 40 includes a securing or supporting bed 41 which is adapted to be 
secured to a work table for a wire cut electrospark machine, and a guide 
rail or rib 42 which is used to (slidably) adjust the vertical position of 
holder 30. The direction of travel of the wire of the wire cut 
electrospark machine is either parallel to guide rail 42 or is inclined at 
a predetermined inclination angle with respect to guide rail 42. Holder 30 
includes a plurality of reference grooves 32 which are formed on a plane 
which is parallel to guide rail 42. 
In both FIGS. 3 (3A and 3B) and 4 (4A and 4B), holder 30 is secured to a 
mounting shaft 51, or to mounting member 52, of electrospark machine head 
50. There are two types of heads 50, one of which is a shaft type head in 
which holder 30 is mounted to shaft 51 of the head, as illustrated in FIG. 
3B, and the other type being a surface reference type in which holder 30 
is mounted to a mounting member 52 with the assistance of a reference 
surface 53, as illustrated in FIG. 3A. A rotation restricting pin 54 is 
provided on shaft 51 in order to restrict the angular displacement of the 
shaft, and to limit the positional relationships in which the holder can 
be attached to electrospark machine head 50. 
One electrospark machining process, and an electrode forming process, will 
now be described herein. 
Initially, an electrode blank 20 having a profile which corresponds to a 
desired electrode profile, and either a corresponding L-shaped or I-shaped 
reference block 10A or 10B, are selected; and mounting holes are formed in 
the selected electrode blank 20 and the selected reference block 10A or 
10B. After these mounting holes are appropriately ground, reference block 
10 is secured to electrode blank 20 by setting screws or bolts 11, which 
are inserted into mounting holes 16, as illustrated in FIGS. 1 and 2. The 
setting screws or bolts are conventional elements. 
Electrode blank 20, having a reference block 10 secured thereto, is then 
retained or held by holder 30 of electrode forming tool 40, and is 
subjected to a wire cut electrospark machining process in order to form 
the electrode blank into a shaped electrode. During a wire cut 
electrospark machining process, the insertion surface of reference block 
10 is fitted into and secured to one of reference grooves 32, 33 or 34 of 
the holder, such that reference surface (z) of insertion portion 13 of the 
reference block will come into close surface contact with the side faces 
of the reference groove to which it is secured, such that reference 
surface (x) will come into close surface contact with the bottom of the 
selected reference groove 32, 33 or 34, and such that reference surface 
(z) will come into close contact with a position restricting member 36 
provided on the outer surface of the holder adjacent the grooves, as best 
illustrated in FIGS. 2-4. 
When electrode 20 is machined in one dimensional direction, insertion 
portion 13 of reference block 10 is fitted into one of the reference 
grooves 32, 33 or 34 to complete a desired machining process. When 
electrode 20 is machined in two- or three-dimensional directions, 
insertion portion 13 is positioned within more than one of the reference 
grooves 32, 33 and 34 in order to complete a desired machining process. 
FIGS. 5A, 5B and 5C illustrate an example of a profile of a shaped 
electrode to be machined. FIGS. 6A, 6B and 6C illustrate the different 
mounting positions of reference grooves 32, 33 and 34 of mounting holder 
30 when the shaped electrode is machined, as illustrated in FIGS. 5A, 5B 
and 5C. Arrows A, B, C and D in FIGS. 5 and 6 illustrate the directions of 
travel of an electrospark machining wire (not shown in the drawings but 
known in the art). 
In accordance with the present invention, therefore, two- or 
three-dimensional machining can be effected with a high precision, since 
the positional relationship between electrode blank 20 and reference block 
10 is constant and does not change, and because reference block 10 can 
always be accurately positioned on holder 30 merely by fitting insertion 
portion 13 of reference block 10 into respective reference grooves 32, 33 
and 34 of the holder. 
Data representing the position of reference grooves 32, 33 and 34 can be 
included in machining data which will be input into a computer which 
controls movement of the wire cut electrospark machine for shaping the 
electrode blank. 
When a tapering machining process is necessary, the direction of travel of 
the wire will be inclined at a predetermined inclination angle, and the 
height of holder 30 will be adjusted by sliding the holder along guide 
rail 42 of electrode forming tool 40, such that data representing the 
height of holder 30 from the work table of the electrode forming machine 
will be similarly input to the computer control in order to optionally and 
accurately set the taper to be imparted to the electrode blank during the 
shaping process. 
The electrode blank which has been machined by the wire cut electrospark 
machine in order to form a shaped electrode 20 is then subjected to 
another machining process which need not be effected by the wire cut 
electrospark machine, e.g., it can be further shaped by a jig borer or by 
similar machinery if necessary. In such a case, machining data relating to 
the wire cut machining process can be supplied to the jig borer; it is 
also possible to measure the shaped electrode at this time. 
The machined electrode 20 is then mounted to head 50 of the electrospark 
machine via holder 30, which is secured to mounting shaft 51 or mounting 
member 52 without removing reference block 10 from electrode 20, as best 
illustrated in FIG. 4. Holder 40 is identical to the holder 30 which is 
used in the electrode forming tool 40 of the wire cut electrospark machine 
used to shape blank 20, and, accordingly, shaped electrode 20, the 
machining data from which can be input to the electrospark machine, is 
then attached to the electrospark machine. Specifically, when insertion 
portion 13 of reference block 10 is fit within any one of reference 
grooves 32, 33 or 34 of holder 30, in accordance with a predetermined 
machining direction of the shaped electrode, and when the setting bolts 
are screwed within mounting holes 16 and threaded holes 35, the electrode 
blank being machined will be in the same position as when it was in the 
wire cut electrospark machine used to shape the blank. When the shaped 
electrode is then set or attached to the electrospark machine (which 
positioning will be referred to as a "set change" hereinafter), it will 
not be necessary to adjust the parallel or perpendicular relationship of 
the surfaces of the electrode, nor the centering of the electrode, with 
respect to the holder. 
Further, the machining and measurement data, i.e., data representing the 
actual profile of the shaped electrode, will be supplied to the control 
unit for the electrospark machine. Electrospark machining is then effected 
by bringing head 50 of the machine close to the workpiece to be machined, 
such that the workpiece will be shaped by the electrode so as to have a 
profile precisely identical to the profile of the shaped electrode 20. 
The present invention can be used in a composite machining process in which 
a plurality of shaped electrodes having different profiles are used. 
Namely, during such composite machining, it is important to center 
electrodes 20; and, in accordance with the present invention, centering of 
a plurality of shaped electrodes can be easily effected in a single 
operation, without special adjustment. 
Further, in accordance with the present invention, because a workpiece 
having a complex profile can be machined by a single shaped electrode, 
precise molding dies with complex profiles can be machined by a reduced 
number of shaped electrodes. 
FIGS. 7 and 8 (8A and 8B) disclose an alternate embodiment of a reference 
block 10C and holder 30', both formed according to the present invention. 
In this embodiment, the shaped electrode has a simpler profile. 
Specifically, reference block 10C includes an electrode blank insertion 
hole or bore 18, which is adapted to receive an electrode blank in the 
form of a cylindrical rod 21, and a hole 14' into which a setting bolt 
(not shown) is inserted to attach the block to a holder. Insertion portion 
13' of reference block 10C is essentially identical to the insertion 
portion of the above-described embodiment. Accordingly, elements 
corresponding to those in the first embodiment have been designated by the 
same reference numerals of the those in the first embodiment in this 
second embodiment; with the exception that primes have been added to 
describe the similar elements in this embodiment. 
Holder 30', which is common to both the electrode forming machine and to 
the electrospark machine, includes a single positioning groove 38 into 
which insertion portion 13' of reference block 10C is adapted to be 
inserted. Positioning groove 38 is provided at one end with a 
position-restricting member 36' attached thereto along the exterior 
surface of the upper portion of the holder. This member is adapted to sit 
on or above a seating surface 39, as illustrated in FIG. 8A. In a manner 
similar to the structure of the first embodiment, two types of holders 30' 
are provided, a shaft reference type holder in which the holder includes 
a mounting shaft 51' and a rotation restriction pin 54', and a surface 
reference type holder in which the holder includes a mounting member 52' 
with a reference surface 53'. In any event, the positional relationship 
between mounting shaft 51' or reference surface 53', and positioning 
groove 38, can be predetermined in advance. Electrode blank 21, which is 
supported by holder 30' via reference block 10C, is thus adapted to be 
machined into a predetermined shape by an electrode forming machine, in a 
fashion similar to that of the first embodiment; thereafter, the shaped 
electrode thus produced from electrode blank 21 is set into an 
electrospark machine having an identical holder 30', such that the 
workpiece to be machined can be machined with a high precision by an 
electrospark machining process. 
A different reference block and holder can be advantageously used for a 
relatively large electrode blank 20a; in FIG. 9, reference block 10D 
includes two positioning holes 61 and 62, and holder 30a includes two 
positioning pins 63 and 64 which can be inserted into respective 
positioning holes 61 and 62. 
Central positioning pin 63 is integrally attached to holder 30a, and 
circumferential positioning pin 64 can be detachably inserted into a hole 
in holder 30a which corresponds to positioning hole 62. Alternatively, it 
is also possible to provide positioning pins on reference block 10D and to 
provide the corresponding positional or positioning holes on holder 30a, 
in a manner opposite from (but similar in purpose) to the illustrated 
embodiment of FIG. 9. 
In FIG. 9, reference block 10D includes mounting holes 66 into which set 
bolts or screws 69 are screwed in order to secure reference block 10D to 
holder 30a. Set bolts 67, which are inserted into corresponding mounting 
holes 65, are screw-engaged into corresponding threaded holes (not 
illustrated) of electrode blank 20a in order to secure block 10D to the 
electrode blank 20. Set bolts 69 are then inserted into bolt inserting 
holes 68 of holder 30a in order to secure reference block 10D and 
electrode blank 20a to holder 30a. There are two possible types of 
holders, e.g., a shaft reference type of holder and surface reference type 
of holder, similar to those shown in FIG. 8, although these are not 
expressly shown in FIG. 9. The holders are adapted to be mounted commonly 
to an electrode forming machine and an electrospark machine, as noted 
previously. 
Similar to the embodiments illustrated in FIGS. 7 and 8, in the embodiment 
of FIG. 9, the electrode blank is mounted to the electrode forming machine 
via a holder, such that the electrode blank will be shaped into a shaped 
electrode having a predetermined shape; and, thereafter, the shaped 
electrode is adapted to be mounted to the electrospark machine via a 
holder which is identical to the holder of the electrode forming machine, 
where it will be subjected to electrospark machining with a high 
precision. 
In an alternative embodiment of the present invention, it is possible to 
provide a reference block having a V-shaped cross-section. In this 
alternative embodiment, the reference groove of the holder is also 
provided with a V-shape, such that the V-shaped groove will provide two 
reference surfaces which are substantially perpendicular to each other. 
Alternately, it is also possible to provide a cross-shaped insertion 
portion on the reference block and a complementary, cross-shaped reference 
groove(s) on the holder, in order to facilitate engagement between the 
holder and the block. 
As noted from the above explanation, the present invention is most 
advantageous when identical holders are provided on both the electrode 
forming machine and the electrospark machine. Alternately, the present 
invention can be applied only to an electrode forming machine to produce a 
shaped electrode having a predetermined shape. In this alternate 
embodiment, the specific holder which is adapted to be mounted to the 
electrospark machine need not be considered. 
The following discussion will be directed to a mounting for an electrospark 
machining electrode. 
FIGS. 10A and 10B illustrate one example of the mounting of an electrode. 
The electrode mounting device of the invention essentially includes a 
machine holder 110 which will be hereinafter referenced as a machine 
holder, and an electrode holder 130. Machine holder 110 is common to all 
machine tools, such as ball end mill machines and electrospark machines, 
and is adapted to be detachably mounted thereto. In the illustrated 
embodiment, machine holder 110 is of the shaft reference type, in which 
the holder is inserted in the machine by inserting a detachable shaft 111 
into an aperture into a machine. The holder can be replaced by a surface 
reference type of holder, as described above and as shown in the drawings. 
An electrode blank 120 (and, later, the formed electrode 121) to be 
machined by a shaped electrode of an electrospark machine is attached to 
electrode (blank) holder 130. Machine holder 110 and electrode holder 130 
engage each other at rotatable, i.e., direction changing, surfaces 112 and 
122, as illustrated in FIGS. 10A and 10B; both of these surfaces are 
inclined at 45.degree. with respect to axis P of machine holder 110. In 
this fashion, electrode holder 130 will rotate about an axis Q which is 
precisely perpendicular to inclined surfaces 112 and 122. Electrode blank 
120 is thus capable of rotating to change its direction by 90.degree. with 
respect to axis P, as illustrated in FIG. 10B, when holder 130 has rotated 
over 180.degree.. 
FIGS. 11A and 11B illustrate one example of forming an electrode 121 in 
which the direction of machining of electrode blank 120 is perpendicular 
to the direction of electrospark machining. Shaped electrode 121, as 
illustrated in FIGS. 11A and 11B, thus has a planar body with an arcuate 
front end 132 and a bottom groove 133 which extends inwardly onto the 
electrode 121 from the arcuate front end 132 of the electrode. 
When a shaped electrode 121 is to be machined, electrode holder 130 is 
attached to machine holder 110 such that the plane of blank 120 will lie 
perpendicularly to axis P. After this attachment, a cutting tool C of a 
machine tool, as illustrated in FIG. 10A, e.g., a ball end mill, will move 
downwardly as illustrated by arrow (a) in FIG. 10A, and will also move 
laterally to cut a desired groove 133. It is thus also possible to cut the 
arcuate front end 132 of the electrode with tool C. 
When shaped blank 121 thus obtained is then subjected to electrospark 
machining by an electrospark machine, electrode holder 130 will be rotated 
or turned by 180.degree. with respect to machine holder 110, as 
illustrated in FIG. 10B, such that shaped electrode 121 will be oriented 
in a direction (b) which is perpendicular to direction (a) of machining 
effected by tool C. Accordingly, by merely transferring insertion shaft 
111 from an electrode forming machine to the electrospark machine, 
electrospark machining can be precisely and exactly effected. 
Specifically, since the distance of the axis P of machine holder 110 and 
the shaped electrodes 121 (i.e., electrode blanks 120) can be 
predetermined, only rotation of the electrode holder over 180.degree. 
needs to occur at the time of the "set change" (taking the known distances 
into consideration) in order to adequately machine a workpiece. 
FIGS. 12 and 13 illustrate details of a machine holder 210 and an electrode 
holder 220. Rotational surfaces 212 and 222 are provided with central 
rotational holes 213 and 223, respectively, into which a central 
rotational pin 221 is adapted to be inserted, such that holders 210 and 
220 can rotate relative to pin 221. Central pin 221 will come into contact 
at its opposite ends with the bottoms of central holes 213 and 223 in 
order to restrict or limit the closest distance that machine holder 210 
and electrode holder 220 will come to each other. The bottom of central 
hole 223 is provided with a threaded bore or additional hole 224 into 
which a fastening bolt 214 is adapted to be inserted through the machine 
holder side so that it will extend through a central opening 221a in 
center pin 221. In other words, bolt 214 is screwed into center opening 
221a of center pin 221. With such a construction, machine holder 210 and 
electrode holder 220 can be secured to each other and come into close 
contact with each other via central pin 223, which also serves to space 
the holder 220 and holder 210 from each other. Electrode holder 220 
includes a pair of positioning holes 225 and 226 which are diametrically 
opposed to each other with respect to central hole 223; a positioning pin 
215 can be selectively inserted into these positioning holes. On the other 
hand, machine holder 210 includes a positioning hole 216 which is adapted 
to be selectively aligned with positioning holes 225 and 226 in accordance 
with rotational movement of the electrode holder 220. As a result, when 
positioning pin 215 is inserted into positioning hole 216 and one of 
positioning holes 225 and 226 is registered with positioning hole 216, 
rotation of the electrode holder 220 relative to the machine holder 210 
can be prevented. The two positions in which the positioning pin 215 is 
inserted in holes 216 and 225 and holes 216 and 226, respectively, 
correspond to the electrode forming position and the electrospark 
machining position, respectively, of the holders. 
A pair of electrode securing surfaces 227 and 228, which are perpendicular 
to each other and which are inclined at 45.degree. with respect to 
rotational surface 222, are provided on electrode holder 220. Electrode 
securing surfaces 227 and 228 are each provided with threaded holes 229 
(see FIG. 13) for receiving set bolts in order to secure an electrode 
blank as desired. The shaped electrode (i.e., a shaped electrode blank) 
can be secured to either one of electrode securing surfaces 227 and 228, 
dependent upon the shape of the shaped electrode. The elements referred to 
above, specifically surfaces 212 and 222, holes or apertures 213, 216, 
223, 225, and 226, centering pin 214, and positioning pin 215, should all 
be formed in a known fashion such that their surfaces will have a high 
surface flatness, the holes will have good surface regularity and accurate 
diameters, and the clearances between the holes and the pins will be 
relatively small. 
With an arrangement as referred to above, when fastening bolt 214 is 
disengaged from threaded aperture 224, electrode holder 220 can be 
detached from machine holder 210. Accordingly, by preparing a required 
plurality of electrode holders 220 having, e.g., electrode blanks 20 (or 
shaped electrodes 20) secured thereto, the number of machine holders 210 
can be decreased (e.g., only one machine holder 210 will be needed) in 
order to achieve the object of the present invention. 
In particular, if a plurality of electrode holders 220 having shaped 
electrodes are adapted to be detachably mounted to a single machine holder 
210, there will be no deviation in the centers of the attached electrodes, 
as there would otherwise be during composite machining using such 
electrodes. Further, precise machining results from the use of positioning 
pin 215, which restricts angular displacement of electrode holder 220. 
In the embodiment referred to above, rotational surfaces 212 and 222 
comprise direction changing surfaces. Alternately, it is possible to 
provide non-rotational direction changing surfaces, as illustrated in 
FIGS. 14-16. In FIGS. 14-16, machine holder 310 includes a direction 
changing surface 312a which is provided with an elongated position 
restricting projection 317a which is located at an intersecting point of 
the surface with the axis P, as shown in FIG. 14. Projection 317a is in 
the form of a rod having a substantially rectangular cross-section. On the 
contrary, electrode holder 320 has a direction changing surface 322a which 
is provided with an elongated aperture 323a which is in the form of a 
rectangular groove into which projection 317a is adapted to be fitted. 
In this embodiment, machine holder 310 includes a bolt hole 318 
substantially at the center of the length of projection 317a, which bolt 
hole is positioned perpendicularly with respect to the direction changing 
surface 312a. Electrode holder 320 includes a threaded hole 324a which is 
located at the center of the length of the bottom of recess 323a of 
electrode holder 320; and which is connected to machine holder 310. 
Fastening bolt 314a is inserted into bolt hole 318 and is threadably 
screw-engaged in threaded hole 324a of electrode holder 320 in order to 
secure holders 310 and 320 to each other. 
A positioning plate 340 is secured to a side face of machine holder 310; 
this positioning plate projects towards electrode holder 320. Electrode 
holder 320 includes a pair of parallel position restricting surfaces 341 
which are spaced from threaded hole 324a by the same distance, and which 
are perpendicular with respect to recess 323a. Position restricting 
surfaces 341 are positioned so as to engage positioning plate 340; and the 
mounting device referred to above is adapted to separate machine holder 
310 from electrode holder 320 when fastening bolt 314a is disengaged. 
Electrode holder 320 includes electrode securement surfaces 327 and 328, as 
shown in FIG. 16. After the holders are separated from each other, they 
are relatively rotated or turned by 180.degree., and projection 317a of 
machine holder 310 is fitted within recess 323a of electrode holder 320, 
such that one of position restricting surfaces 341 will come into contact 
with positioning plate 340. Finally, fastening bolt 314a will be inserted 
into hole or bore 318 and screwed into threaded hole 324a, again in order 
to secure electrode holder 320 to machine holder 310, such that the 
position of an electrode blank (e.g.,20) secured to electrode holder 320 
will be reversed, namely rotated over 180.degree.. In the mounting device 
illustrated in FIGS. 14-16, machine holder 310 and electrode holder 320 
can be easily and inexpensively manufactured. 
It should be noted that projection 317a and corresponding recess 323a can 
be provided with a V-shaped configuration in cross-section, as illustrated 
by the imaginary lines in FIG. 14, rather than a substantially rectangular 
cross-section. It should therefore be appreciated that the cross-sectional 
configurations of projection 317a and the recess 323a need not be limited 
to a rectangular or V-shape, as noted above, but could be formed from 
other shapes. The projection and the recess can be formed of any 
complementary configurations which are symmetrical to each other and with 
respect to central axis of rotation Q. 
The position restricting mechanism in which a positioning plate 340 is 
provided on a machine holder 310, as illustrated in FIG. 14, can also be 
applied to the first embodiment referred to above if desired. 
FIGS. 17-20 illustrate another embodiment of a mounting device having a 
positioning plate 440a. Positioning plate 440a is provided on machine 
holder 410 such that the inner face of positioning plate 440a will engage 
a pair of positional restricting surfaces 441a provided along the side 
faces of electrode holder 420. Positioning plate 440a is movable so that 
it can engage and disengage position restricting surfaces 441a. 
Specifically, positioning plate 440a includes an elongated bore or hole 442 
which extends along the direction of axis P. A fastening screw 443 is 
inserted into elongated bore 442 and is screwed into threaded hole 444 
which is formed in machine holder 410. Accordingly, positioning plate 440a 
can move over a distance defined by elongated hole 442; the length of the 
elongated hole extends in the direction of axis P, such that inclined 
portion 446 of plate 440a, which is parallel to rotational surface 412 of 
the front end of machine holder 410, will project from rotational surface 
412 towards electrode holder 420. Normally, inclined portion 446 is then 
retracted into rotational surface 412. 
A pair of position restricting surfaces 441a of electrode holder 420 are 
parallel to each other and are spaced from axis of rotation Q and from 
axis P by the same distance, in a similar fashion to the above-noted 
embodiments. The other portions of the embodiment noted in FIGS. 17-20 are 
essentially identical to those of the first embodiment. The elements 
illustrated in FIGS. 17-20 which correspond to those of the first 
embodiment have been designated with the same numerals (with the prefix 
400) as those of the first embodiment. For example, electrode securing 
surfaces 427 and 428, electrode bore 424, shaft 411, electrode holder 
surface 422 and aperture 423, bolt 414, center pin 421, center pin opening 
421a, rotational hole 413, and threaded holes 429, are all substantially 
equivalent to previously described elements having the same last two 
digits. 
With the arrangement illustrated in FIGS. 17-20, when electrode holder 420 
is rotated or turned by 180.degree., positioning plate 440a slides towards 
electrode holder 420, so that front inclined portion 446 of positioning 
plate 440a will come into contact with one of the position restricting 
surfaces 441a along the inner faces of the inclined portion 446. This 
prevents relative rotation of electrode holder 420 and machine holder 410. 
The two restricting positions, in which inclined portion 446 of 
positioning plate 440a comes into contact with restricting surfaces 441a, 
correspond to the electrode machining position and the electrospark 
machining position, respectively. 
FIG. 20A and 20B illustrate two different positions of an electrode blank 
430 (and shaped electrode 431) and substantially correspond to the 
positions of FIGS. 10A and 10B, respectively. 
In the embodiment illustrated in FIGS. 17-20, it is not easy to separate 
machine holder 410 from electrode holder 420, as compared to the ease of 
separation which result from use with the previously noted embodiments; 
and, accordingly, the holders can be treated and handled together, as a 
unit, thereby resulting in an increased capacity of preventing the holders 
from becoming lost. 
Positioning plate 440a, which is slidable in the illustrated embodiment, 
can be replaced by a plate which rotates about an axis in order to 
selectively project and retract a projection from rotating surface 412 of 
electrode holder 420. Although positioning plates 440 and 440a are 
provided on machine holder 10 in the illustrated embodiments, they can 
also be supported on electrode holder 420. In such a case, position 
restricting surfaces will be provided along machine holder 410. 
Although the present invention has been described with respect to a variety 
of specific embodiments thereof, it should be clear that it is not limited 
to the specific embodiments listed herein, and that it equally applies to 
all embodiments covered by the claims, and to all embodiments and 
modifications which would be within the skill of those of ordinary skill 
in the art.