CA1171466A - Automatic stop for retraction in an edm machine - Google Patents
Automatic stop for retraction in an edm machineInfo
- Publication number
- CA1171466A CA1171466A CA000389455A CA389455A CA1171466A CA 1171466 A CA1171466 A CA 1171466A CA 000389455 A CA000389455 A CA 000389455A CA 389455 A CA389455 A CA 389455A CA 1171466 A CA1171466 A CA 1171466A
- Authority
- CA
- Canada
- Prior art keywords
- ram
- actuator
- movement
- base
- retraction
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
- B23H7/00—Processes or apparatus applicable to both electrical discharge machining and electrochemical machining
- B23H7/26—Apparatus for moving or positioning electrode relatively to workpiece; Mounting of electrode
- B23H7/30—Moving electrode in the feed direction
Abstract
ABSTRACT OF THE DISCLOSURE
The disclosure teaches an EDM machine hav-ing a base supporting a workpiece, a ram reciprocable on the base and a plurality of electrodes carried by the ram to engage and drill the workpiece. In accordance with the invention, a limit switch limits the retraction movement of the ram in combination with an actuator magnetically held on and movable on the ram and an automatic stop device. The stop device includes a member on the base in a position to engage the actuator during the drilling movement of the ram to adjust the position of the actuator on the ram.
The disclosure teaches an EDM machine hav-ing a base supporting a workpiece, a ram reciprocable on the base and a plurality of electrodes carried by the ram to engage and drill the workpiece. In accordance with the invention, a limit switch limits the retraction movement of the ram in combination with an actuator magnetically held on and movable on the ram and an automatic stop device. The stop device includes a member on the base in a position to engage the actuator during the drilling movement of the ram to adjust the position of the actuator on the ram.
Description
7~
Description An Automatic Stop For Retraction In An EDM Machine Technical Field This invention relates to machines for performing EDM (electrical discharge machining) and particularly to an automatic retraction stop for the machine.
Background Art In the EDM machine and process particularly in drilling small diameter holes one or more small diameter electrodes are advanced toward the workpiece and an electrical differential between the electrode and the workpiece results in the machining of a small diameter hole for each rod being formed in the workpiece. An electrolyte submerge~ the workpiece and electrode to provide an electrical insulation therebetween. The rod is eroded away as the hole is - being drilled at a rate as much as four times the machining of the hole. When a short circuit or other malfunction occurs with any one electrode the ram carr~ving the electrode is automatically retracted to correct the malfunction. A minimum distance for retraction is desirable in order that the electrode will not be withdrawn from the holes which could cause the part to be scrapped for elongated holes and also to minimize the nondrilling time for each operation.
Disclosure of Invention A feature of the invention is the device to minimize the retraction distance and to maintain this distance substantially~constant regardless of electrode wear and depth of drill hole in the workpiece.
7~
Anothex feature is an adjustment by which to change the retraction distance if desired.
In accordance with a particular embodiment of the invention, there is provided an EDM,machine. The machine has a base supporting a workpiece and a ram reciprocable on the base. A plurality of electrodes are carried by the ram to engage and drill the workpiece.
A limit switch limits the retraction movement of the ram and operates in combination with an actuator magnetically held on and movable on the ram and an automatic stop device including a member on the base in a position to engage the actuator during the drilling movement of the ram to adjust the position of the actua-tor on the ram.
According to the invention the ram carrying the electrodes has an actuator for the upper limit stop for t.he retraction and the actuator is magnetically held to a surface on the ram parallel to the direction of ram movement. Cooperating with the actuator is an automatic stop device that is positioned on the base of the machine in a location to be engaged by the actuator so as to reposition the actuator on the ram as the latter moves toward the workpiece. This stop preferably includes a threaded rod on the base extend-ing parallel to the ram movement and sliding through ahole in the actuator. Stop nuts on the rod permit - adjustment of the retraction distance and are set to position the actuator from the limit switch the desired retraction distance. ~s the ram moves toward the work-piece this adjustment will slide the actuator along thesurface on the ram and maintain the actuator so as to control the desired retraction distance at all times.
The foregoing and other objects, features and advantages of the present invention will become more apparent in the light of the following detailed des-cription of the preferred embodiments thereof as shown ~ 7~
-2a-in the accompanying drawing.
Brief Description of the Drawings -Fig~ 1 is an elevation of a machine embodying the invention.
Figs. 2, 3 and 4 are diagrams showing on an enlarged scale the step by step movement of the stop.
Best Mode For Carrying Out l'he Invention As shown in Fig. 1 the machine has a base 2 that has a supporting surface 4 for a plurality of fixtures ~ . c.
1'7~
6 in each of which is releasably mounted a workpiece 8.
The base supports a ver~ically movable ram 10 that carries at its lower end a die set 11 which supports a plurality of holders 12 one above each fixture 6.
Each holder 12 carries a plural:ity of parallely positioned rods or electrodes 14 for pexforming the drilling operations on the workpieces. ~hese electrodes are clamped in vertical position in the holders and may be adjustably positioned therein being held as by clamps 16.
Directly above the fixture 6 is a guide 18 mounted on the base and through which the drilling rods or electrodes extend and by which these electrodes are yuided into the precise desired relation to the workpiece directly below the guide. ~ertical movement of the ram 10 carries all of the rods in unison against the several workpieces and by electrical discharge machining provide holes therein.
When any malfunction occurs as for example a short circuit between one of the electrodes and the associated workpiece, suitable controls reverse the movement of the ram and retract it a small distance to eliminate the short circuit and then again feed the electrode against the workpieces. One type of malfunction is a shorting between cne of the wires and the associated workpiece and this is corrected by a retraction o~ the electrode a vexy short distance.
The retraction movement of the ram on the machine, if not limited, could permit the rods, that is the electrodes to be withdrawn from the holes being drilled and possibly resulting in a scrapped part if the electrode warps away from the hole being drilled.
It is desirable to limit the retraction distance to a speci~ic small dimension that will not vary with each retraction or with the depth of the holes or the amount of erosion of the electrodes. To accomplish this the base carries a limit switch 20 :
:~'7~
that serves to stop the upward retractive movement of the ram~ The ram has an actuator 22 in a position to engage this limit switch and the actuator is - magnetically held in position on a vertical surface 24 on the ram. The base also carries a support 26 for a threaded rod 28 that extends through a vertical hole 30 in the actua~tor and carries adjusting nuts 32 in a position to engage the underside of the actuator.
These nuts are set during operation so as to position '0 the actuator the desired retraction distance from the limit switch.
As the operation of the machine begins and a retraction occurs, the upper movement of the ram will carry the actuator against the switch to stop the retracting movement. As the holes are drilled deeper and as the rods are eroded, the ram moves further down in the machine and the adjusting rod stop nuts being fixed with respect to the base cause a corresponding upward movement of the actuator vertically along the surface 24 on the ram as shown - in Fig. 3. When a retraction now occurs, the actuator engages the limit switch after only the set retracting - movement has occurred because of the higher position of the actuator on the ram. The result is that the same length of retraction movement occurs regardless of the position of the ram. Since the erosion of electrodes and the depth of hole being formed is thus compensated for, the operative ends of the electrodes are in fact withdxawn the same distance from the bottom of the hole for each retraction. The net eff~ct is to foolproof the machine and assure only the necessary limited retraction of electrodes.
In this way, possible damage to the workpieces is avoided and incidentally the nondrilling portion of the cycle of the machine is minimized~
Although the extent of the rnovement of the actuator in Figs. 3 and 4 is shown as a substantial amount it will be understood that in fact the actual movement of the actuator along the ram between retractions may be extremely small on ~he order of one-thousandths of an inch or even less depending upon the frequency that retractio~ occurs. Where the drilling operation involves a plurality of workpieces as shown in Fig. 1, and as many as seventy-five or more electrodes operating on each workpiece any malfunction such as a short circuit on one electrode may occur very frequentlyO The conventional machines are electronically controlled so the malfunctions are sensed electronically and cause retraction and immediate return to feeding motion of the ram. Thus a retraction stroke that can be kept to a minimum uniform length throughout the machine operation is desirable and shortens the length of the total drilling operation.
It will be understood that the machine is built so that the workpieces and operative ends of the electrodes are immersed in a dielectric of a suitable - type. However this is well known in the art and has not been described and it is not in itself a part of the invention in any way.
Although the invention has been shown and described with respect to a preferred embodiment threof, it should be understood by those skilled in the art that othar various changes and omissions in - 30 the form and detail thereof may be made therein without departing from the spirit and the scope of the invention.
Description An Automatic Stop For Retraction In An EDM Machine Technical Field This invention relates to machines for performing EDM (electrical discharge machining) and particularly to an automatic retraction stop for the machine.
Background Art In the EDM machine and process particularly in drilling small diameter holes one or more small diameter electrodes are advanced toward the workpiece and an electrical differential between the electrode and the workpiece results in the machining of a small diameter hole for each rod being formed in the workpiece. An electrolyte submerge~ the workpiece and electrode to provide an electrical insulation therebetween. The rod is eroded away as the hole is - being drilled at a rate as much as four times the machining of the hole. When a short circuit or other malfunction occurs with any one electrode the ram carr~ving the electrode is automatically retracted to correct the malfunction. A minimum distance for retraction is desirable in order that the electrode will not be withdrawn from the holes which could cause the part to be scrapped for elongated holes and also to minimize the nondrilling time for each operation.
Disclosure of Invention A feature of the invention is the device to minimize the retraction distance and to maintain this distance substantially~constant regardless of electrode wear and depth of drill hole in the workpiece.
7~
Anothex feature is an adjustment by which to change the retraction distance if desired.
In accordance with a particular embodiment of the invention, there is provided an EDM,machine. The machine has a base supporting a workpiece and a ram reciprocable on the base. A plurality of electrodes are carried by the ram to engage and drill the workpiece.
A limit switch limits the retraction movement of the ram and operates in combination with an actuator magnetically held on and movable on the ram and an automatic stop device including a member on the base in a position to engage the actuator during the drilling movement of the ram to adjust the position of the actua-tor on the ram.
According to the invention the ram carrying the electrodes has an actuator for the upper limit stop for t.he retraction and the actuator is magnetically held to a surface on the ram parallel to the direction of ram movement. Cooperating with the actuator is an automatic stop device that is positioned on the base of the machine in a location to be engaged by the actuator so as to reposition the actuator on the ram as the latter moves toward the workpiece. This stop preferably includes a threaded rod on the base extend-ing parallel to the ram movement and sliding through ahole in the actuator. Stop nuts on the rod permit - adjustment of the retraction distance and are set to position the actuator from the limit switch the desired retraction distance. ~s the ram moves toward the work-piece this adjustment will slide the actuator along thesurface on the ram and maintain the actuator so as to control the desired retraction distance at all times.
The foregoing and other objects, features and advantages of the present invention will become more apparent in the light of the following detailed des-cription of the preferred embodiments thereof as shown ~ 7~
-2a-in the accompanying drawing.
Brief Description of the Drawings -Fig~ 1 is an elevation of a machine embodying the invention.
Figs. 2, 3 and 4 are diagrams showing on an enlarged scale the step by step movement of the stop.
Best Mode For Carrying Out l'he Invention As shown in Fig. 1 the machine has a base 2 that has a supporting surface 4 for a plurality of fixtures ~ . c.
1'7~
6 in each of which is releasably mounted a workpiece 8.
The base supports a ver~ically movable ram 10 that carries at its lower end a die set 11 which supports a plurality of holders 12 one above each fixture 6.
Each holder 12 carries a plural:ity of parallely positioned rods or electrodes 14 for pexforming the drilling operations on the workpieces. ~hese electrodes are clamped in vertical position in the holders and may be adjustably positioned therein being held as by clamps 16.
Directly above the fixture 6 is a guide 18 mounted on the base and through which the drilling rods or electrodes extend and by which these electrodes are yuided into the precise desired relation to the workpiece directly below the guide. ~ertical movement of the ram 10 carries all of the rods in unison against the several workpieces and by electrical discharge machining provide holes therein.
When any malfunction occurs as for example a short circuit between one of the electrodes and the associated workpiece, suitable controls reverse the movement of the ram and retract it a small distance to eliminate the short circuit and then again feed the electrode against the workpieces. One type of malfunction is a shorting between cne of the wires and the associated workpiece and this is corrected by a retraction o~ the electrode a vexy short distance.
The retraction movement of the ram on the machine, if not limited, could permit the rods, that is the electrodes to be withdrawn from the holes being drilled and possibly resulting in a scrapped part if the electrode warps away from the hole being drilled.
It is desirable to limit the retraction distance to a speci~ic small dimension that will not vary with each retraction or with the depth of the holes or the amount of erosion of the electrodes. To accomplish this the base carries a limit switch 20 :
:~'7~
that serves to stop the upward retractive movement of the ram~ The ram has an actuator 22 in a position to engage this limit switch and the actuator is - magnetically held in position on a vertical surface 24 on the ram. The base also carries a support 26 for a threaded rod 28 that extends through a vertical hole 30 in the actua~tor and carries adjusting nuts 32 in a position to engage the underside of the actuator.
These nuts are set during operation so as to position '0 the actuator the desired retraction distance from the limit switch.
As the operation of the machine begins and a retraction occurs, the upper movement of the ram will carry the actuator against the switch to stop the retracting movement. As the holes are drilled deeper and as the rods are eroded, the ram moves further down in the machine and the adjusting rod stop nuts being fixed with respect to the base cause a corresponding upward movement of the actuator vertically along the surface 24 on the ram as shown - in Fig. 3. When a retraction now occurs, the actuator engages the limit switch after only the set retracting - movement has occurred because of the higher position of the actuator on the ram. The result is that the same length of retraction movement occurs regardless of the position of the ram. Since the erosion of electrodes and the depth of hole being formed is thus compensated for, the operative ends of the electrodes are in fact withdxawn the same distance from the bottom of the hole for each retraction. The net eff~ct is to foolproof the machine and assure only the necessary limited retraction of electrodes.
In this way, possible damage to the workpieces is avoided and incidentally the nondrilling portion of the cycle of the machine is minimized~
Although the extent of the rnovement of the actuator in Figs. 3 and 4 is shown as a substantial amount it will be understood that in fact the actual movement of the actuator along the ram between retractions may be extremely small on ~he order of one-thousandths of an inch or even less depending upon the frequency that retractio~ occurs. Where the drilling operation involves a plurality of workpieces as shown in Fig. 1, and as many as seventy-five or more electrodes operating on each workpiece any malfunction such as a short circuit on one electrode may occur very frequentlyO The conventional machines are electronically controlled so the malfunctions are sensed electronically and cause retraction and immediate return to feeding motion of the ram. Thus a retraction stroke that can be kept to a minimum uniform length throughout the machine operation is desirable and shortens the length of the total drilling operation.
It will be understood that the machine is built so that the workpieces and operative ends of the electrodes are immersed in a dielectric of a suitable - type. However this is well known in the art and has not been described and it is not in itself a part of the invention in any way.
Although the invention has been shown and described with respect to a preferred embodiment threof, it should be understood by those skilled in the art that othar various changes and omissions in - 30 the form and detail thereof may be made therein without departing from the spirit and the scope of the invention.
Claims (4)
1. An EDM machine having: a base supporting a work-piece; a ram reciprocable on the base; and a plurality of electrodes carried by said ram to engage and drill the workpiece; characterized by a limit switch to limit the retraction movement of the ram in combination with;
an actuator magnetically held on and movable on the ram and an automatic stop device including a member on said base in a position to engage the actuator during the drilling movement of the ram to adjust the position of the actuator on the ram.
an actuator magnetically held on and movable on the ram and an automatic stop device including a member on said base in a position to engage the actuator during the drilling movement of the ram to adjust the position of the actuator on the ram.
2. A machine of claim 1 further characterized by adjusting means for changing the operative position of the stop deivce.
3. A machine of claim 1 further characterized by the automatic stop device having a threaded rod mounted on the base and extending through the actuator, said rod being parallel to the ram movement, and a stop nut on the threaded rod to engage the actuator.
4. The machine of claim 1 further characterized by the ram having a surface parallel to the ram movement on which the actuator is positioned, and the stop device causing sliding movement of the actuator along said surface.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/US1981/001102 WO1983000453A1 (en) | 1981-08-12 | 1981-08-12 | An automatic stop for retrack in an edm machine |
| USPCT/US8101102 | 1981-08-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1171466A true CA1171466A (en) | 1984-07-24 |
Family
ID=22161373
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000389455A Expired CA1171466A (en) | 1981-08-12 | 1981-11-04 | Automatic stop for retraction in an edm machine |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS58501274A (en) |
| CA (1) | CA1171466A (en) |
| GB (1) | GB2114930A (en) |
| WO (1) | WO1983000453A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60172423A (en) * | 1984-02-15 | 1985-09-05 | Fanuc Ltd | Electric discharge drilling device |
| JPS60213421A (en) * | 1984-04-07 | 1985-10-25 | Fanuc Ltd | Initial hole machining device in wire-cut electric discharge machining device |
| US4654499A (en) * | 1985-05-20 | 1987-03-31 | Xermac, Inc. | EDM electrode assembly and method of making and using same |
| EP0368394A1 (en) * | 1988-11-08 | 1990-05-16 | Charmilles Technologies S.A. | Device for limiting the tool electrode withdrawal of a working machine and its use in electroerosion |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3125700A (en) * | 1960-08-10 | 1964-03-17 | Automatic electrode wear compensator | |
| US3688074A (en) * | 1971-07-12 | 1972-08-29 | Jade Corp | Electrode wear compensating apparatus for an electrical discharge machine |
| US3777104A (en) * | 1972-05-30 | 1973-12-04 | Colt Ind Operating Corp | Electrical discharge machine ram cycle control system |
| CH585089A5 (en) * | 1975-04-07 | 1977-02-28 | Charmilles Sa Ateliers | |
| US4039779A (en) * | 1975-12-11 | 1977-08-02 | Raycon Corporation | Apparatus for compensating for electrode wear in an electrical discharge machine |
-
1981
- 1981-08-12 WO PCT/US1981/001102 patent/WO1983000453A1/en unknown
- 1981-08-12 GB GB08306779A patent/GB2114930A/en not_active Withdrawn
- 1981-08-12 JP JP50285181A patent/JPS58501274A/en active Pending
- 1981-11-04 CA CA000389455A patent/CA1171466A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS58501274A (en) | 1983-08-04 |
| GB8306779D0 (en) | 1983-04-20 |
| GB2114930A (en) | 1983-09-01 |
| WO1983000453A1 (en) | 1983-02-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |