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Showing papers on "Electrical discharge machining published in 1971"


Patent
21 Jan 1971
TL;DR: An electrical discharge machining device comprising a plurality of detectors for detecting currents and voltages at different parts of the device and generating detection signals in response to the detection, is described in this paper.
Abstract: An electrical discharge machining device comprising a plurality of detectors for detecting currents and voltages at different parts of the device and generating detection signals in response to the detection, a logic circuit for determining different machining conditions of the device by logical combination of the detection signals so as to generate different discerning signals corresponding to the different machining conditions, and a control means for controlling the machining device based on relative frequency ratios of different discerning signals Said relative ratios may be determined by using integrating circuits

43 citations


Patent
29 Jan 1971
TL;DR: An improved electric discharge machining fluid permitting rapid removal of metal, particularly in the case of difficulty machined cast iron, is described in this article, which consists of a hydrocarbon oil and an oil-soluble primary monoamine containing about 12 to 25 carbons.
Abstract: An improved electric discharge machining fluid permitting rapid removal of metal, particularly in the case of difficulty machined cast iron. The electric discharge machining fluid comprises a major proportion of an oil and a minor proportion of an oil-soluble aliphatic amine containing about 10 to 50 carbons. The preferred electric discharge machining fluid comprises a hydrocarbon oil and an oil-soluble aliphatic primary monoamine containing about 12 to 25 carbons.

29 citations


01 Jan 1971
TL;DR: A submitted manuscript is the version of the article upon submission and before peer-review as mentioned in this paper, while a published version is the final layout of the paper including the volume, issue and page numbers.
Abstract: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers.

17 citations


Patent
08 Feb 1971
TL;DR: In this article, an electrical discharge machining apparatus comprising a frame, a plurality of substantially parallel electrodes, a carriage mounted on the frame for guided movement in a vertical direction, and a cartridge assembly supporting the electrodes and removably mounted on a carriage so that the electrodes extend vertically.
Abstract: Electrical discharge machining apparatus comprising a frame, a plurality of substantially parallel electrodes, a carriage mounted on the frame for guided movement in a vertical direction, and a cartridge assembly supporting the electrodes and removably mounted on the carriage so that the electrodes extend vertically. Manually operable gripper means is provided for feeding the electrodes downwardly after each machining operation into engagement with the workpiece so as to compensate for electrode wear experienced during one or more preceding machining operations. Positive stop anti-short power means is combined with the carriage to enable retraction of the electrodes out of engagement with the workpiece into a predetermined spaced relation with the workpiece at least as great as the desired spark gap spacing between the electrodes and the workpiece during machining. The cartridge assembly includes a cartridge member provided with contact blocks connected to a supply of current and engaged with the electrodes during machining.

16 citations


Patent
15 Sep 1971
TL;DR: In this paper, a roll is machined by electrical discharges in a lathe-type machine with a roll length electrode tool, such that high areas of the roll shape the adjacent surface of the electrode tool by a mechanical or electrical wear-in operation, and such surface substantially complements the desired final roll contour.
Abstract: Rolling mill rolls, such as the final rolls for a sheet cold rolling operation, are machined by electrical discharges in a lathe-type machine with a roll length electrode tool. High areas of the roll shape the adjacent surface of the electrode tool, either by a mechanical or electrical wear-in operation, so that such surface substantially complements the desired final roll contour. The shaped electrode tool is subsequently used for electrical discharge machining (EDM) the roll to the level of the lowest roll portions so as to impart a very uniform matte texture to the roll surface and provide a roll with substantially perfect cross-sectional circularily. If the machining is carried out with a segmented electrode tool, the tool is preferably moved slightly from time-to-time axially of the roll during at least the final stages of the machining process. Following the machining, the roll may be used without further processing as an improved substitute for rolls textured by the conventional shot blasting technique or it may be ground to a bright polish.

16 citations


Patent
28 Jun 1971
TL;DR: An electrode for the electrical machining of a conductive workpiece by ECM or EDM is produced by high energy rate forming simultaneously with an index formation engaging in an electrode holder whereby a large number of such electrodes can be massproduced and identically positioned as discussed by the authors.
Abstract: An electrode for the electrical machining of a conductive workpiece by ECM or EDM is produced by high energy rate forming simultaneously with an index formation engaging in an electrode holder whereby a large number of such electrodes can be massproduced and identically positioned. The electrode defines a space with the holder through which a coolant is circulated to limit thermal deformation in use.

16 citations


Patent
10 Mar 1971
TL;DR: In this paper, a protection circuit is provided which senses and responds to gap short circuit condition during machining pulse on-time, and a machining current cut-off function is exercised by a complementary pair of electronic switches which operate with positive action to control pulser operation by decreasing the "on" time of the pulser and decreasing off-time.
Abstract: A protection circuit is provided which senses and responds to gap short circuit condition during machining pulse on-time. Responsive to such condition, a machining current cut-off function is exercised by a complementary pair of electronic switches which operate with positive action to control pulser operation by decreasing the "on" time of the pulser and decreasing off-time. An additional means is provided for appropriate limiting machining current by sensing gap open circuit condition during pulse on-time and correspondingly, through the operation of a complementary pair of electronic switches, increasing the "off" time of the pulser.

15 citations


Patent
24 Feb 1971
TL;DR: In this paper, a worktable reservoir tank, a fluid storage and settling tank and a source of clean fluid under pressure are used for electrical discharge machining, and a side arm of the jet pump can be connected to each of the tanks alternately to draw fluid there from.
Abstract: Electrical discharge machining equipment including a worktable reservoir tank, a fluid storage and settling tank and a source of clean fluid under pressure. Clean fluid under pressure is directed to a gap between an electrode and a workpiece in the reservoir tank during machining, Fluid is pumped between the tanks by a jet pump. Clean fluid under pressure powers the jet pump. A side arm of the jet pump can be connected to each of the tanks alternately to draw fluid therefrom. The discharge of the jet pump is connected to the other tank to discharge into the other tank.

14 citations


Patent
06 Dec 1971
TL;DR: In this article, a method and apparatus for machining a cavity within a work piece by electrical discharge machining with a tool having a replaceable electrode tip is described. But the tool is not aligned with the work piece where the cavity is to be formed and movable toward and away from work piece without affecting the alignment.
Abstract: A method and apparatus are disclosed for machining a cavity within a work piece by electrical discharge machining with a tool having a replaceable electrode tip. The tool includes a positioning member, a holder, a stem attached to the holder, and a tip secured to the stem. The tool is aligned with the work piece wherein the cavity is to be formed and movable toward and away from the work piece without affecting the alignment. During the electrical discharge machining, which produces the cavity, the tip erodes and becomes worn, necessitating replacement. When the tip has become worn, the stem and holder are moved away from the work piece to permit replacement of the worn tip with a new tip. While the tip is being replaced, the alignment of the stem with respect to the work piece is unaffected and the new tip will be automatically aligned with the partial cavity already machined. The tool with the new tip is moved toward the work piece and the electrical discharge machining may be resumed.

10 citations


Patent
12 Jul 1971
TL;DR: In this paper, a limit switch is actuated by a lead screw which is physically connected to the electrode holding means and the lead screw is moved a predetermined distance away from the limit switch by a motor means on each operation of the electrical discharge machine (EDM).
Abstract: Apparatus for compensating the electrode wear in an electric discharge machine tool wherein an end of electrode travel signal is generated by actuation of a limit switch. The limit switch is actuated by a lead screw which is physically connected to the electrode holding means. The lead screw is moved a predetermined distance away from the limit switch by a motor means on each operation of the electrical discharge machine (EDM).

9 citations


Patent
19 Jul 1971
TL;DR: In this article, an oversize negative master die or working tool with a roughened surface thereon from a positive model is used in conjunction with automated apparatus to prepare identical duplicate electrical discharge machining electrodes of the same dimensions as the model.
Abstract: A method of making an oversize negative master die or working tool with a roughened surface thereon from a positive model. The oversize negative master die is used in conjunction with automated apparatus to prepare identical duplicate electrical discharge machining electrodes of the same dimensions as the model.

Patent
20 Aug 1971
TL;DR: In this article, a new electrode material for electrical discharge machining consisting essentially of copper containing a critical oxygen content was disclosed, which showed an increase in wear resistance of up to 30 percent over presently known electrode materials and after heat treatment shows an increase of cutting speed three-fold over oxygen free copper electrodes.
Abstract: A new electrode material for electrical discharge machining consisting essentially of copper containing a critical oxygen content is disclosed. The novel electrode shows an increase in wear resistance of up to 30 percent over presently known electrode materials and after heat treatment shows an increase of cutting speed three-fold over oxygen free copper electrodes.

Patent
26 Mar 1971
TL;DR: In this paper, a gap monitoring circuit registering machining energy flow across a working gap between a tool electrode and a workpiece in terms of voltage and/or current is presented, and a servo system which effects advance and retraction of the tool electrode to maintain the working gap within predetermined dimensions.
Abstract: The invention provides electrical discharge machining apparatus including in combination, a gap monitoring circuit registering machining energy flow across a working gap between a tool electrode and a workpiece in terms of voltage and/or current; a servo system which effects advance and retraction of the tool electrode to maintain the working gap within predetermined dimensions; a retraction detection means registering the extent of retraction of the tool electrode. In addition there is provided a subsidiary control circuit which is effective to operate at least one of (i) a warning device which may be visible or audible, (ii) means for disconnecting the supply of machining power to the inter-electrode gap, (iii) means for fully retracting the tool electrode; this subsidiary circuit being effective only when the following conditions exist simultaneously: the gap monitoring circuit registers machining energy flow at normal working levels and the retraction detection means registers retraction of the tool electrode to such an extent that the tool electrode and the workpiece are separated by more than a predetermined distance.

Patent
16 Aug 1971
TL;DR: In this paper, a depth stop sensing device used in an electrical discharge machine which cuts holes of a specified depth in a conductive workpiece by eroding the workpiece with a discharge cutting current includes a tool electrode having a cutting porjection that is lowered into cutting relationship with the work piece by a ram assembly.
Abstract: A depth stop sensing device used in an electrical discharge machine which cuts holes of a specified depth in a conductive workpiece by eroding the workpiece with a discharge cutting current includes a tool electrode having a cutting porjection that is lowered into cutting relationship with the workpiece by a ram assembly. As a cutting current is applied by the tool electrode to the workpiece, a hole is formed in the workpiece in the same shape as the cutting projection. When the hole is cut to the specified depth, a sensing projection on the tool electrode supplies a signaling current to a sensing finger disposed adjacent to the workpiece and positioned at the specified depth. A triggering circuit coupled to the sensing finger receives the signaling current from the sensing finger and initiates the retraction of the ram assembly and thereby the tool electrode from the workpiece so that the hole is not cut beyond the specified depth.

Patent
03 Sep 1971
TL;DR: In this paper, a frequency generator for use with electrical discharge machining devices to afford automatic control of the operational duty cycle, such control being effected by monitoring cutting conditions at the cutting area or gap, reducing the duty cycle whenever the gap voltage falls below a predetermined voltage which is substantially in excess of zero voltage.
Abstract: A frequency generator for use with electrical discharge machining devices to afford automatic control of the operational duty cycle, such control being effected by monitoring cutting conditions at the cutting area or gap, reducing the duty cycle whenever the gap voltage falls below a predetermined voltage which is substantially in excess of zero voltage to automatically reduce the predetermined normal duty cycle by an amount proportional to the amount by which said gap voltage falls below said predetermined voltage, the monitoring means being continuously operable to monitor the gap voltage and thereby maintain the duty cycle at a level reduced from the normal duty cycle by an amount proportional to the amount which the gap voltage is below the predetermined voltage and to adjust the duty cycle to a predetermined minimum duty cycle if the gap voltage is reduced to zero volts.

Patent
12 Aug 1971
TL;DR: In this paper, a servo feed control circuit in which servo feeds control of the cutting operation is related to gap electrical parameter during machine pulse on-time was presented. But this circuit was used only for machining pulse ontime only.
Abstract: A servo feed control circuit in which servo feed control of the cutting operation is related to gap electrical parameter during machine pulse on-time. A gap voltage sensing network is connected to an electrical servo feed means through a field effect transistor, which transistor in turn is rendered conductive through a keying arrangement effective during machining pulse ontime only.

Patent
02 Sep 1971
TL;DR: In this paper, the authors present a method for adjusting the working gap in an electrochemical machining system in which a tool electrode poled as cathode is by means of a feed motor moving relative toward a workpiece electorde as anode, while electrically parallel to the two electrodes there is provided a voltage detector which controls switch means for the feed motor.
Abstract: Method of and device for adjusting the working gap in an electrochemical machining system in which a tool electrode poled as cathode is by means of a feed motor moved relative toward a workpiece electorde poled as anode and in which after adjustment of a working gap between the electrodes an electrolyte is pumped through the working gap, while electrically parallel to the two electrodes there is provided a voltage detector which controls switch means for the feed motor in such a way that in the absence of a metallic contact between the two electrodes the tool electrode is moved by the feed motor toward the workpiece elctrode whereas in response to a metallic contact between the electrodes the voltage detector opens the switch means, and the feed motor is stopped.

Patent
13 Sep 1971
TL;DR: In this article, an electrical discharge machining circuit of independently variable machining pulse frequency and current magnitude is presented, where a current control system is employed to limit current to the gap to a safe level.
Abstract: An electrical discharge machining circuit of independently variable machining pulse frequency and current magnitude as set by machining pulse on-time. A current control system is employed to limit current to the gap to a safe level in accordance with each preselected frequency and current magnitude combination. Included to accomplish the control function are a plurality of gating means connected in a logic system and employing the resistor-transistor configuration.

Patent
10 Mar 1971
TL;DR: In this paper, a protective system is provided for an electrical discharge machining apparatus of the multiple type in which there are a single pulse generator and a plurality of drive and output stages, each associated with a different machining gap.
Abstract: A protective system is provided for an electrical discharge machining apparatus of the multiple type in which there are a single pulse generator and a plurality of drive and output stages, each associated with a different machining gap. A separate cutoff stage is keyed into operation in phased relationship with the machining power pulses to each gap and control of machining power pulses is exercised through switching of a flip-flop stage operatively connected in each drive stage.

Patent
21 Jan 1971
TL;DR: In this article, a method and a device for machining a workpiece by means of spark erosion are described, in which a breakdown is produced in a discharge space formed by the workpiece and a tool electrode which are connected to a supply source.
Abstract: A method and a device for machining a work-piece by means of spark erosion are described, in which a breakdown is produced in a discharge space formed by the work-piece and a tool electrode which are connected to a supply source. It is shown that the current density in the discharge space may be maintained substantially constant by switching a stabilized voltage source across the discharge space at the instant of breakdown.

Patent
16 Jun 1971
TL;DR: The electro-erosion device gives a smoother surface and is coupled to a trigger circuit spark generator that is connected to a workpiece electrode and a tool electrode as mentioned in this paper.The electrical connections are made by conductors consisting in each case of a bundle of strands having a cross-section 0.2 mm.
Abstract: The electro-erosion device gives a smoother surface and is coupled to a trigger circuit spark generator that is connected to a workpiece electrode and a tool electrode. The electrical connections are made by conductors consisting in each case of a bundle of strands having a cross-section 0.2 mm.

Dissertation
01 Jan 1971
TL;DR: Thesis (B.S. as discussed by the authors, Mass. Institute of Technology, Dept. of Mechanical Engineering, 1971, Boston, Massachusetts, USA, U.S., USA.
Abstract: Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1971.

Patent
25 Jun 1971
TL;DR: In this paper, the authors present an ARRANGULAR DISCHARGE MACHINING CIRCUIT, which is a system for providing an array of ELECTRONIC SWITCH MEANS for discharging a power plug into a generator.
Abstract: THE CIRCUIT INCLUDES AN ARRANGEMENT FOR PROVIDING ELECTRICAL DISCHARGE MACHINING ACROSS ONE OR MORE GAPS WITH POWER PULSES DERIVED FROM A COMMON POWER SUPPLY. EACH MACHINING GAP INCLUDES AN ELECTRONIC SWITCH AND HAS ASSOCIATED WITH IT A SHUNT DIODE OF BLOCKING POLARITY TO PREVENT GAP INDUCTANCE FROM BREAKING DOWN THE ASSOCIATED SWITCH. WHEN SEVERAL ELECTRONIC SWITCHING MEANS ARE USED, THEY ARE EACH CONNECTED THROUGH AN ISOLATING DIODE TO A COMMON PULSE GENERATOR OR TRIGGERING MEANS FOR TURNING THEM ON AND OFF AT THE SAME TIME. ALSO IN- CLUDED IN EACH GAP CIRCUIT IS A SERIES DIODE OF A POLARITY TO A PASS POWER PULSES TO THE GAP WITH A DETECTOR MEANS CONNECTED ACROSS THE SERIES DIODE FOR PROVIDING AN INDICATION OF COMPONENT FAILURE IN THE ASSOCIATED GAP CIRCUIT WHEN SEVERAL SWITCHES ARE CONNECTED IN PARALLEL.

Patent
01 Feb 1971
TL;DR: In this article, a main machining DC source is derived from an AC source through a rectifier, and a saturable reactor is connected between the AC source and rectifier to limit the maximum current that is available from the DC source.
Abstract: A circuit is included to provide preselected gap cutting current limiting. A main machining DC source is derived from an AC source through a rectifier. A saturable reactor is connected between the AC source and rectifier to limit the maximum current that is available from the DC source. The control of the saturable reactor is maintained and regulated in accordance with the frequency at which the electrical discharge machining operation is being carried out.

Patent
17 Nov 1971
TL;DR: In this article, a control circuit for automatic control of electric discharge machinery apparatus is presented, where a transistor 16 is controlled to pass power pulses from a source 10 to a dielectric coolant-filled gap between an electrode 12 and a workpiece 14, with the control circuit shown for automatically maintaining the gap spacing at a predetermined value.
Abstract: 1,254,211. Automatic control of electric discharge machinery apparatus. ELOX Inc. Jan.3, 1969 [Jan.22, 1968], No.456/69. Heading G3R. Electrical discharge machinery apparatus of the type wherein a transistor 16 is controlled to pass power pulses from a source 10 to a dielectric coolant-filled gap between an electrode 12 and a workpiece 14, is provided with the control circuit shown for automatically maintaining the gap spacing at a predetermined value. The electrode movement is controlled by a coil 44 which forms part of a hydraulic motor and servo valve system (not shown) and which is included in a differential amplifier comprising transistors 46, 48 to show bases are respectively applied signals representative of actual and desired gap spacing. The former signal is derived from a sensing circuit which comprises members 34, 36, 38, 40, 42 and which is connected between a multi-vibrator drive 22, 24 for the transistor 16 and members 12, 14. During normal operation an RC circuit 64, 66 is connected in series with the coil 44 and transistor 46 is turned on by the signals from the drive 22, 24, which also operates the transistor 16 at a predetermined frequency and mark/space ratio. Thus current passes through the coil 44 in a direction corresponding to downward movement of the electrode 12 and the gap spacing is held at a value determined by the setting of a reference potentiometer 30. Should the gap be "shorted", transistor 48 conducts to reverse the current flow through the coil 44, the consequent discharge of capacitors 60, 66 producing a rapid electrode movement upwards and the subsequent charging of these capacitors producing a rapid downward movement, these features ensuring rapid short circuit clearance and restoration to normal gap spacing. A second RC circuit 68, 70, 72 of different time constant from the first is used during a high frequency finishing operation to slow down the servosystem. The illustrated arrangement of members 44, 54, 56, 58, 60 is suitable for operation at relatively high frequencies and may be modified. Fig.1a (not shown) for low frequency operation. The sensing circuit 34--42 may be connected to point B instead of point A, the transistor 16 may be replaced by an equivalent three electrode electronic switch (e.g. a vacuum tube) and the coil-hydraulic motor combination may be replaced by the direct control of an electric motor.