Showing papers on "Electrical discharge machining published in 1975"
Patent•
11 Dec 1975
TL;DR: In this paper, the position of the electrode at the start of EDM machining of a workpiece is estimated by measuring the forward movement of the needle during each machining cycle and regulating the backward retracting movement of needle to compensate for erosion of needle during the machining process.
Abstract: Electrical discharge machining apparatus having means to sense the position of the electrode at the start of EDM machining of a workpiece. The apparatus includes means to measure the forward movement of the electrode during each machining cycle and regulate the backward retracting movement of the electrode to a preselected distance so as to compensate for erosion of the electrode during the machining cycle to thereby facilitate positioning of the electrode in the correct location for the next machining cycle. The apparatus includes a sensing device operable to transmit electrical pulses corresponding to incremental movements of the electrode and control circuitry which receives the pulses and controls subsequent movement of the electrode.
24 citations
24 citations
Patent•
12 Nov 1975
TL;DR: In this article, a process and apparatus for achieving relative displacement between the electrode tool and the electrode workpiece of an EDM apparatus about a closed or looped path at a speed varying as a function of the machining gap width, such as to remove material from the machined surfaces at a substantially constant material removal rate.
Abstract: A process and apparatus for achieving relative displacement between the electrode tool and the electrode workpiece of an EDM apparatus about a closed or looped path at a speed varying as a function of the machining gap width, such as to remove material from the machined surfaces at a substantially constant material removal rate.
21 citations
Patent•
05 Nov 1975
TL;DR: In this paper, a liquid for electrical discharge machining which enables the machining to be performed at a markedly increased rate inviting less corrosion is described. But this liquid being prepared by emulsifying and dispersing a silicone oil and a surfactant in water.
Abstract: PURPOSE:To obtain a liquid for electrical discharge machining which enables the machining to be performed at a markedly increased rate inviting less corrosion, said liquid being prepared by emulsifying and dispersing a silicone oil and a surfactant in water.
14 citations
Patent•
04 Jun 1975
TL;DR: In this article, the machining power pulses are reduced during gap short-circuit condition by using a read-only memory to provide information relative to the material of the workpiece and the thickness of the piece.
Abstract: The system includes data input means for information relative to the material of the workpiece and the thickness of the workpiece. A read-only memory then provides information to a programmable counter so that off-time for the machining power pulses is appropriately provided for. In addition, there is manual preset means for setting the off-time to be provided during gap short circuit condition. An appropriate cut-off sensing circuit is operatively connected to the gap for sensing short circuit condition and initiating the pulse reduction but only for the duration of the gap short circuit condition.
14 citations
Patent•
30 Jan 1975TL;DR: In this paper, a curved tube insertable into the passage and an elongate flexible electrode is fed into the tube and deflected thereby to produce the desired holes, the apparatus is preferably for use with electrical discharge machining power supplies.
Abstract: An apparatus principally for producing holes in the wall of a passage in a workpiece, the apparatus has a curved tube insertable into the passage and an elongate flexible electrode is fed into the tube and deflected thereby to produce the desired holes, the apparatus is preferably for use with electrical discharge machining power supplies.
13 citations
Patent•
03 Feb 1975
TL;DR: In this paper, fault condition detectors monitor gap conditions and track voltage variations of the dc cutting current supply, and voltage drop detectors are used to modify automatic operation of the timing unit.
Abstract: On-time and off-time control over the current pulses by the timing unit associated with the power supply for EDM apparatus is supervised by fault condition and voltage drop detectors to modify automatic operation of the timing unit. The fault condition detectors monitor gap conditions, and track voltage variations of the dc cutting current supply.
11 citations
Patent•
03 Nov 1975TL;DR: Spark erosion is applied to a nonconducting workpiece while employing a dielectric liquid comprising an emulsion of an aqueous solution of an electrolyte in an organic liquid and a surfactant.
Abstract: Spark erosion is applied to a non-conducting workpiece while employing a dielectric liquid comprising an emulsion of an aqueous solution of an electrolyte in an organic liquid and a surfactant.
10 citations
Patent•
27 Jan 1975
TL;DR: In this paper, an eccentric device is placed between a pair of orthogonal rollers, each spaced from opposing surfaces of the workpiece, so that a conical cutting path is described with respect to the electrode wire as it traverses in proximity to the work piece during cutting.
Abstract: A system for controlling the cutting of a workpiece with a wire electrode. The system provides for inclining the electrode wire in the path of traversal in opposition to the electrode such that a predetermined incline or taper is given to the workpiece during cutting. This is accomplished with precision control and sizing by providing an eccentric device positioned between a pair of orthogonal rollers, each spaced from opposing surfaces of the workpiece, so that a conical cutting path is described with respect to the electrode wire as it traverses in proximity to the workpiece during cutting.
9 citations
Patent•
01 Aug 1975
TL;DR: In this paper, a graphite substrate is impacted by a dry air blast of glass beads having a size in the range of approximately 200 to 325 mesh, which will remove a desired amount of graphite to thereby cut the desired pattern into the substrate but will not remove the photoresist or affect the substrate beneath the polymerized photoresists.
Abstract: Method of forming an electrode for imprinting or imaging a circuit board mold face includes covering a graphite substrate with a photoresist material. The photoresist material is appropriately exposed to develop a desired pattern. The unpolymerized photoresist is removed from the graphite substrate to leave the desired pattern of an exposed graphite surface. The graphite substrate is then impacted by a dry air blast of glass beads having a size in the range of approximately 200 to 325 mesh. The glass beads will remove a desired amount of graphite to thereby cut the desired pattern into the substrate but will not remove the photoresist or affect the substrate beneath the polymerized photoresist. The polymerized photoresist is removed with materials that will not interfere with the subsequent machining process. The resultant cut graphite substrate can be utilized as a electrode in an electrical discharge machining process to form a desired pattern in a mold face.
8 citations
Patent•
17 Apr 1975TL;DR: In this article, a continuous smooth surface on a workpiece having an irregular surface comprising a nonsmooth area bordered by a smooth area is produced by electrical discharge machining with a rotating electrode.
Abstract: Method and apparatus for producing a continuously smooth surface on a workpiece having an irregular surface comprising a nonsmooth area bordered by a smooth area. Said workpiece is subjected to electrical discharge machining with a rotating electrode, while maintaining an acute angle between the axis of said electrode and the face of said workpiece.
Patent•
17 Jul 1975
TL;DR: In this article, a step motor is used to drive the cross-table on which wire drawing dies are mounted on a cardan suspension, the wire electrode entering the hole in the metal part at the intersection of the x-and y-axis of the suspension, and the axes of the cross table being parallel with the X- and y- axes.
Abstract: Spark erosion machine for making conical holes etc. in metal parts, uses numerical control of the path of a wire electrode fed continuously through the hole and where a stepping motor is used to drive the cross-table on which the metal part is mounted, the novelty being that the cross-table can pivot on all sides. The cross-table is pref. mounted on a cardan suspension, the wire electrode entering the hole in the metal part at the intersection of the x- and y- axes of the suspension, and the axes of the cross-table being parallel with the X- and y- axes of the suspension. Two U-shaped machine elements are pref. used of form the cardan suspension and the cross-table is pref. adjustable w.r.t. height. Esp. the mfr. of wire-drawing dies in hard metal using punched- or magnetic-tape and numerical control. Conical holes with an included angle up to 45 degrees can be made during an automatic cycle.
Patent•
30 Jun 1975TL;DR: An electrical discharge machining process using as a dielectric fluid a composition comprising a base oil and a minor amount of an oil-soluble cationic organic surfactant is described in this paper.
Abstract: An electrical discharge machining process using as a dielectric fluid a composition comprising a base oil and a minor amount of an oil-soluble cationic organic surfactant.
Patent•
28 Apr 1975
TL;DR: In this paper, a multidimensionally curved surface on a workpiece using an electro-erosion machine tool is machined by using a tool electrode which has an effective machining face inclined to the direction in which the advance feed drive of the machine tool advances the tool electrode towards the workpiece.
Abstract: In order to machine a multidimensionally curved surface on a workpiece using an electro-erosion, i.e. spark erosion or electro-chemical erosion, machine tool, the machine tool is provided with a tool electrode which has an effective machining face inclined to the direction in which the advance feed drive of the machine tool advances the tool electrode towards the workpiece. By using transverse feeding mechanisms for the tool electrode or the workpiece acting under the control of a computer, or by using a cam and guide arrangement coupled to the tool electrode, the tool electrode and workpiece are so relatively moved that the effective machining face of the electrode always moves in the direction of the momentary largest radius curvature of the curve to be machined. When a cam and guide arrangement is used, the tool electrode can be coupled to the advance feed drive by way of a coupling device which incorporates a universal joint, or a domed surface sliding joint. The effective machining face of the tool electrode can be curved in accordance with at least a part of the curve to be machined.
Patent•
19 Jun 1975
TL;DR: In this paper, the authors proposed to maintain cooling effect and easy discharge generation effect always optimal for machining, by controlling working fluied feed amount per 1g, with in a range of about 400-3,000cc.
Abstract: PURPOSE:To maintain cooling effect and easy discharge generation effect always optimal for machining, by controlling working fluied feed amount per 1g. machining, with in a range of about 400-3,000cc. CONSTITUTION:The working fluid flow fed by a pump 7 is partially by-passed through relief valve 8 to control flow amount of machining clearance 4. A control circuit 9 controls said valve 8 as required responding to machinging power by means of a signal from machining power ditection circuit 11. There is an optimal value for working fluid feed amount per machining of 1g. and that for kerosene is 700-3,000cc/g, with water 400-1,000cc/g, therefore, it will do only by presetting this relationship in said control circuit 9 as a working fluid feed amount per unit energy. Hence, by controlling feed amount within 400-3,000cc/g, the cooling effect and easy discharge generation effect are always kept optimal for machining.
Patent•
15 Apr 1975
TL;DR: In this paper, an improved power output pulse amp circuit was proposed for machining a conductive workpiece by passing electrical pulses between a tool electrode and the workpiece across an arc gap therebetween.
Abstract: An improved power output pulse amp circuit module for use especially in an apparatus for machining a conductive workpiece by passing electrical pulses between a tool electrode and the workpiece across an arc gap therebetween. The improved power output circuit module includes individual diodes in series with each output transistor to prevent sequential massive failure and also to protect each individual transistor against the second breakdown phenomenon. Optionally, the output circuit module may include a protector circuit for detecting the presence of a high voltage due to a breakdown, which protector circuit may be used to turn OFF the high voltage supply and also, optionally to turn ON an operator warning light until a repair or replacement has been made.
Patent•
07 Oct 1975
TL;DR: In this article, an over or undersize abrasive master mold is used to form tool electrodes by abrading a workpiece using a circular reciprocatory motion The master mould is made by a casting process which starts with a preformed model, positive or negative, of the exact shape to be machined by the tool electrodes.
Abstract: An over or undersize abrasive master mould is used to form tool electrodes by abrading a workpiece using a circular reciprocatory motion The master mould is made by a casting process which starts with a preformed model, positive or negative, of the exact shape to be machined by the tool electrodes to be made Positive and negative castings of the model, one of which castings is abrasive, are subjected to a relative circular reciprocatory motion in an abrading operation to provide the correct under or oversize of the master mould, which is then made directly or indirectly from the abraded casting Casting apparatus for use in the method comprises a pallette for holding the casting and adjusting devices for ensuring parallelity and correct alignment for the moulding faces and there is also disclosed apparatus for the abrading operation in which an error detection system regulates the amplitude of the reciprocatory abrading movement
Patent•
25 Mar 1975
TL;DR: In this article, a longitudinally movable carriage supports the workpiece in a tank which is filled with dielectric machining liquid to a level above the level of the opening.
Abstract: Electric discharge machining apparatus and methods, particularly suited to enlarging an elongate opening or bore in an electrically conductive workpiece, wherein a longitudinally movable carriage supports the workpiece in a tank which is filled with dielectric machining liquid to a level above the level of the opening. An elongate strain rod, which may be removably coupled to the tank end walls, extends longitudinally through the opening and mounts an electric discharge machining electrode in axial alignment with the bore. An electromachining source of power is connected to the workpiece and the electrode for eroding the workpiece to enlarge the bore to precise configuration as the carriage moves the workpiece axially relative to the electrode.
01 Jan 1975
TL;DR: In this article, the effects of debris concentration on erosion of the electrodes, and the tool/work erosion ratio, varied, depending upon the materials and conditions, in some cases, however, the effect was negligible.
Abstract: Electro-discharge machining has been studied with controlled ‘pollution’ of the dielectric up to very high levels by unfiltered recirculation. The effects of debris concentration on erosion of the electrodes, and the tool/work erosion ratio, varied, depending upon the materials and conditions. In some cases, however, the effect was negligible.
TL;DR: In this article, the workpiece material removal rate, tool wear rate, discharge frequency and wear ratio (ratio of workpiece removal rate and tool wear ratio), when supply voltage and capacitance are changed in an R-C circuit, have been studied using High Speed Steel and High Carbon Steel as workpiece materials and copper, brass and aluminum as tool electrodes.
Patent•
29 Dec 1975
TL;DR: In this article, a push-pull drive stage is used to drive the output stages in either polarity setting in such manner as to allow for negligible noise in the system, and a switching system is provided for reversing the polarity of electrode relative to workpiece.
Abstract: A power supply circuit particularly useful in a multiple gap or a multiple electrode system in which multiple electrodes and a common workpiece or multiple electrodes and a like number of workpieces are selectively connected in circuit with a common DC source power supply circuit. A switching system is further provided for reversing the polarity of electrode relative to workpiece. A power supply circuit itself incorporates a specialized push-pull drive stage effective to drive the output stages in either polarity setting in such manner as to allow for negligible noise in the system. The drive system is one which generates triggering pulses effective to switch the output transistor bank in either polarity very rapidly and independently of the number of output leads which may be included.
Patent•
30 Oct 1975
TL;DR: The electronic control system depends on the generation of a series of electrical impulses across the gap between the electrode tool and the workpiece and the circuit monitors this gap be means of the threshold discriminators which generate a signal when the thresholds of 20V, 35V and 45V respectively are exceeded as discussed by the authors.
Abstract: The electronic control system depends on the generation of a series of electrical impulses across the gap between the electrode tool and the workpiece The circuit monitors this gap be means of the threshold discriminators which generate a signal when the thresholds of 20V, 35V and 45V respectively are exceeded These different thresholds correspond to the state of the di-electric which fills the gap between the electrode tool and workpiece which may be gas or a mixture of gas and liquid or all liquid, depending on operating conditions The electrical impulses from the electrode tool affect the rate of discharge of the condenser which in turn controls the threshold discriminators
Patent•
24 Apr 1975
TL;DR: In this article, a toroidal coil is used to energise a Schmitt-trigger via a controlling diode which discriminates between fast and slow rates of rise current by the voltage induced in the coil.
Abstract: An electrical discharge machine comprises an oscillator which feeds impulses to an electrode via an amplifier and a resistor in the conventional way. Should either partial or complete short circuits occur between the electrode and a workpiece it is known that the rate of rise of current flow between the electrode and the workpiece is very high. This rate of rise is detected by a toroidal coil positioned around the lead to the electrode and used to energise a Schmitt-trigger via a controlling diode which discriminates between fast and slow rates of rise current by the voltage induced in the coil. The output from the schmitt-trigger is passed via a flip-flop to one entrance of an AND gate positioned between the oscillator and the amplifier to isolate the electrode.