JPH0451284B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a wire electrical discharge machining method and apparatus.

(Prior Art) A conventional wire electric discharge machining (hereinafter abbreviated as EDM) apparatus includes a head assembly attached to a machining tool body and a numerically controlled positioning table. The wire device also includes a spool assembly on which a thin wire is stretched tightly between two spools. A drive spool moves the wire from one spool to another at a constant speed. At this time, the effective processing length of the wire is ensured between the two spools. This length is approximately 10.16 cm to 20.32 cm. The cutting speed depends on the dimensions of the wire, the current flowing through the wire, and the feed rate, which is set to the depth of the cup. Fully ionized water is not only commonly used as a dielectric but also serves to wash away corrosive particles generated during cutting operations. As is known in all electrical discharge machining (EDM) operations, wire electrodes produce uniform over-cutting or over-burning. This excessive cutting or burning is approximately 0.00508 cm to 0.00762 cm larger than the diameter of the electrode.

In the extrusion of ceramic honeycomb structures used in catalytic exchangers of internal combustion engines, it is necessary to form extrusion dies with fairly long and narrow grooves. The fairly long narrow groove is not only straight and extends across the front face of the die, but also has parallel side walls and a uniform surface finish without burrs. Further, such long narrow grooves may have a length of more than about 8.89 cm, a depth of more than about 0.1524 cm, and a depth of more than about 0.03048 cm.
has a width not greater than

U.S. Patent Nos. 2,526,423, 4,205,213, and
All known wire electrical discharge machining (EDM) methods, such as that disclosed in US Pat. No. 4,233,486, are capable of forming grooves. However, such methods do not allow for a wire of a given diameter to
Limits the effective depth of grooves that can be cut to lengths greater than 8.89 cm or more. That is, for example, in known wire electrical discharge machining (EDM) methods, the effective cutting depth is limited because it is difficult to wash away corrosive particles from small grooves with a depth of 0.1524 cm or more during the cutting process. When the wire cutting process is stopped due to the deposition of corrosive particles, the groove width at that depth is significantly enlarged or improperly overcut, resulting in uneven grooves and wire breakage. arise.

Almost all wire electrical discharge machining (EDM) methods involve supplying fully ionized water longitudinally along or coaxially with the wire to create a longitudinal notch or groove in the workpiece. , using an array configuration for flushing either longitudinally or coaxially with the wire. However, when machining such longitudinal grooves using the wire method, the coaxially fed flushing medium is deflected at the edge of the workpiece and therefore this deflection of the dielectric is Make work inefficient or impossible. Inefficient machining conditions occur when the machine repeatedly returns from the surface to be cut and the electrical discharge is interrupted, or when orange sparks are observed in the cutting area, or when persistent wire breakage occurs. appears when As previously discussed, such inefficient machining conditions not only severely impact the ability to machine grooves to a given desired depth, but also the ability to consistently form grooves from beginning to end. The "ability to repeat" is effectively lost. Additionally, it has been discovered that when cutting with conventional wire electrical discharge machining (EDM) methods, an enlarged or flared condition often occurs at the entrance of the groove near the machined surface.

SUMMARY OF THE INVENTION The present invention overcomes the problems present in known wire electrical discharge machining (EDM) methods and apparatus, and provides parallel sidewalls with a uniform surface finish and preferably With a depth of 1.524 cm or more, 8.89
Its purpose is to enable the repeated formation of a plurality of long, thin grooves having a length of cm or more.

SUMMARY OF THE INVENTION According to the invention, a longitudinal path is used in which an electrical discharge machining wire moves along the length of the surface of the workpiece to be cut. The passageway is also open at each end but substantially closed along its length, allowing the dielectric fluid to extend beyond the surface of the workpiece to be cut and around the EDM wire. The flow is directed to flow along a directional path. The enclosed longitudinal passageway may be formed by a scouring device or trough having a longitudinal channel formed therein and containing the workpiece. is positioned opposite the surface to be cut.

(Operations and Effects of the Invention) In the present invention, the efficiency of the cutting process can be increased by providing a longitudinal passage around the electrical discharge machining wire along the surface of the workpiece to be cut. This is because the longitudinal passages achieve coaxial flushing such that corrosion particles leached from within the groove as the groove is cut are completely flushed from the groove itself. Accordingly, the present invention overcomes the limitations in groove length and depth that plague conventional electrical discharge machining methods and apparatus. According to the present invention, it is possible to repeatedly form a plurality of narrow grooves having a depth of more than 0.1524 cm and a length of 8.89 cm or more. Additionally, the plurality of narrow grooves can have a uniform surface finish and parallel sidewalls.

(Example) Referring to the drawings, especially Figures 1, 2 and 3,
A flushing device or trough assembly 10 for a wire electrical discharge machining process is shown positioned near a surface 72 of a workpiece 70 to be cut. The trough assembly 10 includes a mounting bracket 12 for mounting the trough assembly 10 to a wire electrical discharge machine support structure (not shown). A guide platform 14 is adjustably mounted on the mounting bracket 12 by cap screws 16, the cap screws 16 being attached to the mounting bracket 12.
It protrudes through a groove 18 formed in the groove. The guide stand 14 has a pair of upper and lower holes 20 located on the outside, and a flanged bearing member 22 for slidably receiving a guide pin 24 is mounted in the holes 20. The guide pin 24 is fixed to the plunger stand 26 within the recess 28. The plunger base 26 is bolted to a trough member or receiving base 30 with a screw or bolt 32 or the like.

The front face 34 of the trough member 30 is provided with a recess or channel 36 along its longitudinal extension;
This groove path 36 is open on the side facing the surface to be cut (hereinafter referred to as "front surface 34"), and is open at the top and bottom ends of the trough member 30 in the vertical direction. The bottom openings are adjacent to each end of the surface 72 to be cut.

If desired, a passage having a plurality of apertures 40 may be formed in the trough member 30 to connect the passage to the channel 3.
6, thereby forming flushing means transversely to the area cut by the wire. Furthermore, a plurality of outlets or water discharge passages 42 are provided in the trough member or receiver 30, and these outlets 42 connect the channel 36 and the receiver 30.
0 may be in communication with the outer surface of the channel 36 to facilitate release or drainage of excess flushing fluid from the channel 36.

A wire W, as used in standard wire electrical discharge machining equipment, is shown in its initial position near the surface 72 of workpiece 70 to be cut by the solid line in FIG. 1 and by the dashed line W'. , is shown in the cutting position for forming the groove S shown in FIG. The longitudinal passage forms a groove 36 around the wire W.
It will be understood that the groove S is formed by the groove S and the groove S.
This longitudinal passage directs the axial flow of the dielectric flushing fluid along the longitudinal length of the wire W, thereby removing corrosion particles from within the small groove S cut by the wire W. Or wash it away.

The front surface 34 of the trough member 30 is a work piece 70
is held opposite the surface 72 to be cut so as to contain a dielectric fluid in a longitudinal or axial passage around the wire W during the cutting process. The guide pin 44 is connected to the plunger stand 26.
A hole 4 fixed to the guide table 14 and formed in the guide table 14
It stands out within 6. Additionally, a spring 48 seated at the end of the prepared hole 50 in the guide stand 14 is positioned around the guide pin 44 and moves the trough member or receiving stand 30 outward to prevent the surface of the work piece 70 to be cut. It abuts against the back surface of the plunger base 26 in order to engage with or come close to the plunger base 72 . A restraining washer assembly 52 is secured to the rear end of the guide pin 44 to limit forward movement of the plunger base 26 relative to the guide base 14. A handle 54 operated by a finger manually slides the trough member 30 toward and away from the work piece 70, so that the plunger stand 2
It extends outward from 6. Although the channel 36 is shown as having an arcuate shape in FIG. 2, the channel 36 of the trough member 30 has a pilot hole shape 56 as shown in FIG. 4 and a pilot hole shape 56 as shown in FIG. T-shape 58, square shape 60 as shown in FIG.
It may have.

In order to facilitate the formation of long narrow grooves with parallel side walls with a uniform surface finish, the grooves 36 and S formed by the groove S around the wire when flushing unwanted particles from the cutting area. The longitudinal passages help. As a particular embodiment, the square channel 60 formed in the trough member 30 is
The groove can have a depth of about 0.127 cm and a width of about 1.27 cm. The length of the groove, regardless of its shape, is substantially equal to the length of the surface to be cut that is being cut. If the trough member of the present invention is not used, process obstacles are expected when processing with molybdenum wire, and approximately 0.0254 cm
Various penetrations occur between this penetration and 0.152cm penetration, and the maximum penetration rarely exceeds 0.152cm. Using the T-shaped groove shown in Figure 5,
When using a molybdenum wire with a diameter of 0.01 cm,
A slight penetration of 0.03 cm was observed, and when using the same wire with the pilot hole-shaped groove shape shown in FIG. 4, a slight penetration of about 0.3 cm was observed.

When the trough member of the present invention is applied, the diameter is 0.0178
using multiple brass wires of cm and 0.002 cm, and
By using the curved channel of FIG. 2 or the rectangular channel of FIG. 6 with a depth of about 0.127 cm and a width of about 1.27 cm, each die has a surface to be cut of 17.145 cm and 20.32 cm. High-quality grooves can be formed on the front surface of the mold. The standard deviation of the groove dimensions depends on the material used and the quality of the workpiece, but is approximately
It falls between 0.005cm and 0.01524cm. These results demonstrate that the work piece can be machined to a significantly greater depth and finished with a more uniform and parallel surface using the trough member of the present invention than without the present invention. If desired, in conjunction with the axial flushing, it is also possible to perform lateral flushing through the openings 40, which is particularly useful when applying thin molybdenum wires. Although it has not been proven necessary for all wire applications, it has been observed that the use of this technique significantly increases transparency.

Referring to FIGS. 7-9, a cross-sectional portion of the workpiece 10 is enlarged and shown as having a pre-cut or guiding groove 112. A preliminary cut 112 is formed in the machining surface 114 by an electrical discharge machining wire 121 and extends to a depth d. The long narrow groove 116 has parallel sides with a uniform surface finish, and the pilot hole-shaped groove 11
Work piece 1 from the inner end 113 of 2 to depth D
It extends within 10. A wire 120 of a wire electrical discharge machine is inserted into the inner end 118 of the groove 116.
shown near. As shown in FIG. 7, the diameter of the wire 121 and the width w of the prepared groove 112 are equal to the diameter of the wire 120 and the long and thin groove 116.
, and the width w is two to three times the width W of the long and thin groove 116. After the desired groove 116 is formed in the workpiece 110, the pilot groove 112 can be eliminated by cutting down the upper surface 114 of the workpiece 110 to the bottom 113 of the pilot groove 112.
That is, depth d is removed.

As shown in FIG. 8, when the workpiece 110 is to be made into the extrusion die 130, the new surface 124 becomes the working or exit surface 124 of the extrusion die, and the plurality of long narrow grooves 116 is the emission surface 12 of the die 130.
A lattice-like acting part is formed across the 4. As previously mentioned, the groove 116 extends along the side edge 12 of the die 130 until it reaches a distance equal to the depth D shown in FIG.
6.

FIG. 9 shows a broken part 1 on the surface of the die mold 130.
Although only 24 is shown, it is clear that the groove 116 extends in a criss-cross pattern across the entire surface 124 of the die 130, and at its widest point extends approximately
Extends beyond the maximum diameter of the die which is greater than or equal to 20.32 cm.

The above basic wire EDM method is approximately
It is possible to process grooves with a width of 0.0254 cm or more, and the present invention can also process grooves with a width of 0.0178 cm or less.
It is possible to process long, thin, and highly precise grooves with a depth of 0.254 cm or more accurately and with good reproducibility. An enlarged precut or guiding pilot groove is initially formed in the surface of the workpiece with a width of about 1.5 to 3.5 times the width of the desired groove to be formed in the workpiece. The depth of the pilot groove can vary from about 0.127 cm to about 0.381 cm, with an average effective depth of about 0.2159 cm. In view of the time and cost factors involved in forming an enlarged pilot flute and the fact that a greater depth of the pilot flute does not increase the cutting efficiency of the desired flute, approximately 0.381 cm or more. There seems to be no reason to form a pilot hole-like groove with a maximum depth of .

When the depth of the pilot groove is less than about 0.0762 cm, the standard deviation of the desired groove increases considerably, resulting in undesirable non-uniformity in the parallelism and straightness of the cut desired groove. . For example, when the pilot hole has a depth of about 0.381 cm, the workpiece is effectively penetrated to an average depth of about 0.32766 cm, with a standard deviation of 0.004547 cm, but in a similar test, the depth of the pilot hole It was found that when the depth is 0.0762 cm, the standard deviation is 0.0132 cm, and an average depth of about 0.0315 cm can be obtained. Additionally, it was found that when using a pilot hole of only 0.0762 cm, the average cutting speed was significantly reduced during the final 0.04572 cm penetration.

As previously mentioned, uncontrolled and irregular overcuts that occur when the cut is stopped due to inefficient flushing or removal of particles from the groove are undesirable, but uniform It will be appreciated that overcutting is obtained. That is,
In a preferred embodiment, in order to form a guide or pilot groove 112 on the front surface 114,
Brass wire with a diameter of 0.0254cm is used and approx.
An average width w of 0.03048 cm is formed. Guide groove 1
12 is machined to a depth d of approximately 0.2159 cm, and then
A long, narrow working groove 116 is machined from a molybdenum wire having a diameter of 0.0127 cm. At this time, the groove 116 is straight and has no curls, with an average depth of about 0.014986 cm and a standard deviation of about 0.0004572 cm.
is formed with good reproducibility. The maximum length of the groove formed in the workpiece is equal to the maximum diameter of the extrusion die 130 made from the workpiece, and ranges from 17.145 cm to 20.32 cm depending on the die required.
The various materials that can be processed by the above method include EZ-Cut 20, cold rolled steel, D-2 steel, crucible CPM-10V, Ferro-o-tic, stainless steel and high nickel alloys. but,
The above method is applicable to virtually all tool steels, carbide materials, hot ISO steels, and vacuum melted steels.

Although the exact mechanism by which such pilot grooves improve cutting efficiency and standard deviation over known techniques has not been precisely elucidated, the dielectric material supplied to the cutting area during electrical discharge machining operations is Said pilot groove or enlarged pre-cut 112 functions as a tubular wash-out chamber for fluid, and corrosion particles in the groove 116 generated during cutting can be easily removed from the groove 116 by such fluid. It is thought that this will make it easier. The corrosive particles, if not removed as described above, will limit the effective depth and cutting speed. Said coaxial flushing is ensured by the pilot hole-like grooves, thus increasing the efficient removal of corrosive particles. long and narrow groove 1
Upon completing the formation of 16 to form the release groove of die 130, surface 114 is removed by lowering the enlarged pilot groove 112 to the die working surface 124 and removing it.

Although presently preferred embodiments of the invention have been disclosed, it will be appreciated by those skilled in the art that the wire cutting method of the invention can be used to form virtually any article and as described in the claims. It will be understood that various substitutions and modifications may be made without departing from the spirit and scope of the invention as described.

[Brief explanation of the drawing]

FIG. 1 is a side elevational view of a washing device or trough of the present invention positioned facing the surface of a workpiece to be cut, and FIG. 2 is a top plan view of the device of FIG. 1. , FIG. 3 is a front elevational view of the apparatus of FIG. 1 with the workpiece omitted and rotated 90 degrees, and FIGS. 4, 5, and 6 show the trough member of FIG. FIG. 7 is a large enlarged partial cross-sectional view of a workpiece showing grooves formed in accordance with another embodiment of the invention; FIG. FIG. 9 is a perspective view of the die, with a part of the die cut away to show the pattern of discharge grooves formed on the front surface of the die. FIG. 9 is a perspective view of a main part showing a broken portion of the die mold shown in FIG. 8, greatly enlarged to show the grooves formed using the die. 10... Washing device (trough assembly), 12
...Mounting bracket, 14...Guide stand, 16...
... Cap screw, 18 ... Groove, 20 ... Hole, 22 ... Bearing member with flange, 24 ... Guide pin, 26 ...
...plunger stand, 28 ... recess, 30 ... trough member, 32 ... bolt, 34 ... front, 36 ...
Ditch (waterway), 40...opening, 42...water discharge passage,
44... Guide pin, 46... Hole, 48... Spring,
50... Pilot hole, 52... Stop washer assembly,
54...Handle, 56...Prepared hole shape, 58...
T-shape, 60... Rectangular shape, 70... Work piece, 72... Surface to be cut, 112... Pilot hole-shaped groove (preliminary cutting), 114... Surface, 116...
Groove, 118... Inner end, 120... Wire, 1
21...Wire, 124...Emission surface, 126...
Side edge, 130...Dice type, S...Groove, W,
W'...Wire.

Claims (1)

Claims: 1. Providing a workpiece having a surface to be cut; positioning an electrical discharge machining wire in a longitudinal passage proximate a predetermined portion of the surface to be cut; substantially shielding the passageway and the wire within the passageway while leaving both ends of the passageway open near the terminal edge of the surface to be cut; and providing fluid around the passageway and the wire. directing the fluid along the axial direction of the passage and the wire; and cutting the work piece from the predetermined portion with the wire to form a groove extending in the depth direction from the passage. . A wire electrical discharge machining method comprising the steps of: forming corrosion particles in the passageway; and washing away the corrosion particles from one of the openings of the passageway along the axial direction of the passageway. 2. The method of claim 1, including the step of supplying dielectric fluid in the axial direction of the longitudinal passageway. 3. The method of claim 1, including the step of supplying dielectric fluid to the longitudinal passage from a direction transverse to the passage. 4. The method of claim 1, including the step of providing means for discharging said fluid supplied to said longitudinal passageway from a direction transversely therebetween between a plurality of open ends of said longitudinal passageway. 5. A trough member having a groove formed on the front surface thereof is positioned so that the electrical discharge machining wire is located within the groove formed in the trough member, so that the groove and the trough member are arranged to cut a workpiece. positioning the wire in engagement with or adjacent to the surface to be cut of the workpiece so as to form a substantially enclosed longitudinal passage around the electrical discharge machining wire along the direction of extension of the surface; The method of claim 1 comprising: 6. An electrical discharge machining wire, a trough member extending in the vertical direction and having a shielding surface facing the surface to be cut of the workpiece, and a trough member formed vertically within the trough member along the shielding surface, and a groove path that is open facing the surface to be cut and the groove to be cut and that is laterally partitioned by two independent parts of the shielding surface; the shielding surface is positioned to engage or proximate the surface to be cut so as to be substantially surrounded by the surface and the groove to form a longitudinal passageway through which the electrical discharge machining wire extends; means for directing and determining a flow of dielectric fluid into the groove along an axial direction of the wire for washing away corrosion particles generated in the groove during cutting of the groove; An electrical discharge machining device that supplies the dielectric fluid into the groove. 7. The apparatus of claim 6, wherein the trough member includes means for supplying fluid to the channel from a direction transverse to the channel. 8. The apparatus of claim 6, wherein said trough member includes means for discharging excess fluid from said channel to the exterior of said trough member. 9. The apparatus of claim 6, wherein the channel formed in the trough member has a rectangular cross-sectional shape. 10. The apparatus of claim 6, wherein the channel formed in the trough member has an arcuate cross-sectional shape.