Showing papers on "Electrical discharge machining published in 1993"

Theoretical models of the electrical discharge machining process. III. The variable mass, cylindrical plasma model

Abstract: A variable mass, cylindrical plasma model (VMCPM) is developed for sparks created by electrical discharge in a liquid media. The model consist of three differential equations—one each from fluid dynamics, an energy balance, and the radiation equation—combined with a plasma equation of state. A thermophysical property subroutine allows realistic estimation of plasma enthalpy, mass density, and particle fractions by inclusion of the heats of dissociation and ionization for a plasma created from deionized water. Problems with the zero‐time boundary conditions are overcome by an electron balance procedure. Numerical solution of the model provides plasma radius, temperature, pressure, and mass as a function of pulse time for fixed current, electrode gap, and power fraction remaining in the plasma. Moderately high temperatures (≳5000 K) and pressures (≳4 bar) persist in the sparks even after long pulse times (to ∼500 μs). Quantitative proof that superheating is the dominant mechanism for electrical discharge ma...

Experimental investigations into electrical discharge machining with a rotating disk electrode

Abstract: In electrical discharge machining, when the provision of holes in the electrode is impracticable, flushing of the working gap poses a major problem. Use of a rotating disk electrode is proposed as a more productive and accurate technique than use of a conventional electrode. Material removal rate, tool wear rate, relative electrode wear, corner reproduction accuracy, and surface finish aspects of a rotary electrode are compared with those of a stationary one. The effective flushing of the working gap brought about by the rotation of the electrode remarkably improves material removal rate and machines surfaces with a better finish. Despite the prevalent high tool wear rate, the reproduction accuracy is least affected as the wear gets uniformly distributed over the entire circumference of the disk. Machining of a sharp corner is possible even with an aluminum electrode, whose relative electrode wear is greater than unity.

Method of producing diffusion holes in turbine components by a multiple piece electrode

Abstract: A method of forming diffusion holes in a super alloy article by electrical discharge machining by the steps of (a) inserting onto an electrical discharge machine a multiple piece electrode with at least one tooth with respectively at least one movable elongated rod wherein each rod is positioned through each tooth and secured to the tooth, and (b) advancing the multiple piece electrode during electrical discharge machining longitudinally into the super alloy article so that the rod forms a hole with a metering section in the super alloy article of about 0.010 inches in diameter at a depth in excess of about 0.250 inches and the tooth forms a diffused area, with an angle of about 10 degrees, at one end of the hole.

Device and process for electrical-discharge machining of a three-dimensional cavity with a thin rotating tool electrode

Abstract: An EDM device for machining by electro-erosion a three-dimensional cavity by compensating for tool-electrode wear, which device includes a mechanism for rotating a tool electrode whose diameter is small in comparison to the dimensions of the cavity being eroded, a numerical control unit of known type, which controls relative three-dimensional movement between the tool electrode and the workpiece, apparatus for controlling volumetric wear rate, and computational apparatus equipped for storing the volumic shape of the cavity to be eroded in the form of virtual fine parallel layers superimposed on one another, for simulating a tool path so that the tool tip sweeps groove by groove across said successive layers, and for transmitting a corresponding signal to the three-dimensional control unit, characterized by a simulator that is programmed to calculate prior to machining the longitudinal wear of the rotating tool or a value intended for additional axial feed of the tool electrode and continuously compensating for said longitudinal wear, this calculation being made from preexisting, known technological data and parameters characterizing the geometry of the electrodes, and designed to transmit to the three-dimensional control unit a corresponding signal continuously compensating for this wear.

Electric discharge machining device

Abstract: PURPOSE:To display a machining time easily understood and further accurately controllable by providing a display means for displaying the present time and the machining ending expected time. CONSTITUTION:By an actual machining condition determining means 1, an actual machining condition containing a machining speed is determined from an experimental preobtained machining condition basic data 8 and preset data 7a. Further from a machining program 9, a peripheral length of a workpiece is obtained by a peripheral length calculating means 2. Next from this machining speed and the peripheral length, a machining time is calculated by a machining time calculating means 3. Simultaneously with the above, the present time is counted by a time counting means. Based on the present time counted by this time counting means and the machining time calculated by the machining time calculating means 3, the machining end expected time is calculated by a machining ending time calculating means 4. These present time and machining ending expected time are displayed analogically by a display means 16.

Method and apparatus for controlling electric discharge machining

Abstract: A method of and apparatus for controlling electric discharge machining in which a machining gap formed between a tool electrode and a workpiece is maintained at an essentially constant size based on a reference servo-feed voltage, and in which a jump action, for moving a tool electrode up and away from a workpiece, and returning it to a position close to the workpiece is controlled. The reference servo-feed voltage and conditions for jump action are optimally set to required values during machining according to the discharge stability. The discharge stability is obtained by comparing the actual values of characteristics required for specifying gap condition, e.g., waiting time for a discharge to occur, the voltage during the waiting time, discharge frequency, to the corresponding theoretical values. The theoretical values are calculated in part according to given machining conditions. Therefore, even when machining conditions change as machining progresses, jump action and servo-feed action are properly controlled.

Surface characteristics of titanium with rotary EDM

Abstract: Experimental investigations have been carried out on electro-discharge machining of titanium in respect of surface finish, out-of-roundness and overcut using rotating copper-tungsten tool electrode. An attempt has also been made to compare the results with stationary electrode.

Surface treating method of aluminum and alloy thereof by discharge in liquid

Abstract: (57) [Summary] (Modified) [Purpose] Efficiently forms a surface-hardened layer on the surface of aluminum and its alloys that has particularly high hardness, excellent wear resistance, and good adhesion and dimensional accuracy. [Structure] Ti, Zr, V, Ta, Cr, Mo, W, M n powder, Al powder, Sn powder, or Zn in a single powder or a mixed powder of two or more kinds of metals that easily carbonize such as Nb An electrode for electric discharge machining is obtained by compression-molding the powder into a desired shape by adding a binding metal, and in a machining fluid that decomposes and produces carbon by electric discharge, Al and its alloy, which are the amount of material to be treated, are used as the other electrode. A surface treatment method by submerged discharge of Al and an alloy thereof, which comprises forming a surface layer in which the above metal and a carbide thereof are mixed on the surface of a material to be treated by electric discharge machining.

Coil and manufacture of it

Abstract: PURPOSE: To easily manufacture coils for axial-direction DC-type brushless motors each having a spiral current path with approximately the same center and in approximately the same shape as an iron core made out of pillarlike soft magnetic material, by forming grooves with a cutting tool in an ingot formed by copper or aluminum extrusion. CONSTITUTION: A raw material 11 for a coil is made by extrusion of a copper or aluminum ingot with approximately the same center as and in a shape a little bit larger than and similar to an iron core made out of pillarlike soft magnetic material. Following this, grooves 30 and 31 are formed at a specified pitch with a cutting tool 20 rotatable about a rotation shaft brought into contact with the raw material 11 for a coil. As a cutting tool 20, either of wire electric discharge machining, water jet machining, electronic beam machining, and laser machining besides a metal saw and a screw slotting cutter, or their combination can be used. As a result. it becomes possible to manufacture a large number of products extremely cheaply. COPYRIGHT: (C)1995,JPO

Surface Modification by Electrical Discharge Machining : Composite Electrode Method

Abstract: This paper presents a new method of surface modification by electrical discharge machining (EDM) using composite structured electrode. Composite structured electrode is made of green compact product or sintered product. Since the apparent thermal conductivity of the electrode is very low, the wear rate of the electrode gets so high that the substance of the electrode is implanted into work surface by EDM. Some experiments of surface modification were performed on carbon steel as workpieces by EDM with the composite electrodes in hydrocarbon oil. Copper, aluminum and tungsten carbide were used for the material of the electrode in experiments. It was revealed that there existed the electrode material in the work surface layer with the thickness of several tens micrometers. These surfaces have less cracks, high corrosion resistance and wear resistance.

Method of precision electric-discharge machining employing electrodes in the form of wires, and apparatus for carrying out the method

Abstract: A method of precision electric-discharge machining carried out in apparatus of moderately high precision and stability with an electrode in the form of a wire. The object is a surface as smooth as the surface that can be obtained with the more expensive very high-precision apparatus. The contour of work that has already been roughed out at least once is accordingly exploited as a geometrical reference for at least one finishing cut. The gap is maintained constant by fine adjustments.

Method of machining metallic workpieces with cooling

Abstract: The invention relates to a method of machining metallic workpieces and also ceramic surfaces, in which cooling is carried out during the machining operation by feeding a coolant to the machining point. According to the invention, instead of conventional, liquid coolants, a coolant jet consisting at least mainly of carbon dioxide (CO2) and containing cold gas and snow particles is fed to the machining point for the cooling.

Method for manufacturing master of die for shaping golf ball

Abstract: A method for forming a master die from a conductive material using electrical discharge machining. The conductive material is created to have a plurality of dimples that are non-circular in a direction perpendicular to the spherical surface of a conductive material and/or in a vertical cross section. The plurality of dimples being formed by electric discharge machining using an electrode that is moved in a direction perpendicular to the surface of the material.

Wire electric discharge machining device

Abstract: PURPOSE:To improve machining precision by restraining 'corner sagging' at a corner part of a machining route in a wire electric discharge machining device to improve the machining precision at the corner part in the machining route. CONSTITUTION:By controlling relative positions of a wire electrode 60 and a machined article 100 supplied and controlled by a wire control part 6 by a machining route control part 5 in accordance with a machining route, detecting a corner part in this machining route by a corner detection part 3 and sequentially carrying out correction of tangential movement of a specified distance, movement along a corner of the specified distance and gradual return movement by a machining route correction part 4 concerning this detected corner, 'corner sagging' at the corner part is prevented, and machining precision is improved.

Electrical discharge machine

Abstract: An electrode for electrical discharge machining. This spark-machining electrode improves the accuracy at which the workpiece is machined by electrical discharge machining. The electrode can dispense with a mechanism which scans the spark-machining electrode or the workpiece. A plurality of needlelike electrodes are formed on the surface of the spark-machining electrode. The needlelike electrodes are so arranged that they are present in craters created by their respective adjacent needlelike electrodes. The plural electrodes form a group. The shape of the surface of this group is formed according to the desired shape to be formed in the workpiece. Art electric discharge occurs mainly at the tips of the needlelike electrodes and so the capacitance is smaller than the capacitance of the prior art flat-plate electrode. Also, the energy of a single electric discharge can be reduced. Furthermore, electric discharge at the side surfaces of the needlelike electrodes can be suppressed because of the effect of concentration of electric field.

Behaviour of a silicon spring fabricated by wire electro-discharge machining

Abstract: A silicon spring/frame combination has been fabricated laterally out of a (100) silicon wafer, using wire electro-discharge machining (WEDM) in a one-dimensional measurement problem. After a thermal annealing step and an isotropic etching process the crystalline structure of the silicon wafer could be restored. Exposing the spring to over three-million working cycles yielded no detectable fatigue at all. A high-resolution X-ray diffractometer was used to measure the strain in the wafer. This is an accurate, non-destructive microscopic method newly applied in this field to obtain quantified results on the crystalline disorder. The method is applied to the microfabricated spring after annealing and etching steps.

Electrical discharge machine with secondary electrode for corrosion prevention

Abstract: An electric discharge machining apparatus of the travelling wire or sink type includes at least one secondary electrode (14) which is immersed in the dielectric at least during machining. A microvoltage power supply (13) is used to create a micropotential difference between the workpiece (2) and the secondary electrode (14) so that the workpiece becomes a negative pole. Maintaining this arrangement both during machining and non-machining times prevents the workpiece from being subjected to positive-pole oxidation.

Surface Modification of Stainless Steel by Electrical Discharge Machining

Abstract: A commercial SUS 304 stainless steel was machined by EDM with a sialon electrode. The machined surface changed from the machining to the surface modification layer on the some proper machining conditions. The effect of the following factors to form the surface layer was investigated: Electrode polarity, work atmosphere and the working condition of the peak current, pulse duration and duty factor. Under the suitable machining conditions, the EDMed surface was covered with the alloyed layer, which consisted of the electrode and work piece components. The surface modified layer improved the corrosion and wear resistance.

Method for controlling a wire-cut electric discharge machine

Abstract: A method of controlling a wire-cut electric discharge machine to improve machining accuracy in a machining operation for a corner portion of a workpiece to be machined. In a case where the portion to be machined includes a corner, a pressure and/or an amount of machining fluid supplied to a gap between the workpiece and a wire electrode is decreased only in a specified section. The setting of this specified section and adjustment of the machining fluid is carried out on the basis of an allowable discrepancy amount, and shape and size of the corner. Furthermore, in addition to decreasing electric discharge energy supplied between the workpiece and the wire electrode, the machining fluid may be adjusted within the specified region.

Apparatus for filtering machining liquid of an electrical discharge machine

Abstract: An apparatus for filtering machining liquid of an electrical discharge machine. The apparatus includes a plurality of cross flow filters placed in series with one another and with a pump drawing dirty liquid from a capacity tank. The permeate from the cross flow filters is provided to the electrical discharge machine. The permeate outlets of the cross flow filters are provided with valves that are selectively opened only upon demand for machining liquid by the electrical discharge machine. The permeate valve of the cross flow filter having the smallest cross member pressure is opened prior to opening other permeate valves. A capacity tank includes a baffled area and sludge accumulating within the capacity tank is drawn from the baffled area to paper filters. The cross flow filters are back flushed on a timed interval and the particulates dislodged during back flushing are dumped into the baffled area of the capacity tank.

Method and apparatus for supplying power for electric discharge machining

Abstract: A method of and apparatus for supplying power during EDMing in which reverse polarity pulses are used to inhibit electrolytic activity. A main voltage pulse of a certain polarity and an auxiliary voltage pulse, preceding the main voltage pulse of the same or reverse polarity, are applied across a machining gap during the on time of a main gate signal and until a discharge is detected. The ratio of the number of auxiliary voltage pulses of regular polarity to those of reverse polarity is set to a desired value depending upon machining conditions, to thereby obtain a good compromise between the conflicting requirements of achieving a high machining rate, while inhibiting undesirable electrolytic activity.

An electric discharge machining fluid

Abstract: An electric discharge machining fluid comprising a mixture of a liquid dielectric and a powder of polycrystalline silicon and a small amount of inorganic oxide, provided for forming smooth workpiece surfaces having a carbon-iron-silicon alloy. The powder is present in an amount from 0.1 to 5.0 wt % of the liquid dielectric. The inorganic oxide includes silicon oxide, iron oxide and/or calcium oxide. Further, a concentrate made by kneading the powder with oil mainly composed of an aromatic hydrocarbon or aromatic hydrocarbons having a density of more than 0.93 g/millilitre at 15°C, is added to the dielectric whereby the powder is dispersed uniformly.

Self aligning electron beam gun having enhanced thermal and mechanical stability

Abstract: A compact, high power electron gun having enhanced thermal and mechanical stability which incorporates a mechanically coupled, self aligning structure for the anode and cathode. The enhanced stability, and reduced need for realignment of the cathode to the anode and downstream optics during operation are achieved by use of a common support structure for the cathode and anode which requires no adjustment screws or spacers. The electron gun of the present invention also incorporates a modular design for the cathode, in which the electron emitter, its support structure, and the hardware required to attach the emitter assembly to the rest of the gun are a single element. This modular design makes replacement of the emitter simpler and requires no realignment after a new emitter has been installed. Compactness and a reduction in the possibility of high voltage breakdown are achieved by shielding the "triple point" where the electrode, insulator, and vacuum meet. The use of electric discharge machining (EDM) for fabricating the emitter allows for the accurate machining of the emitter into intricate shapes without encountering the normal stresses developed by standard emitter fabrication techniques.

Diamond machining method

Abstract: PURPOSE:To provide a diamond machining method for eliminating adhesion of a graphite or an amorphous carbon derived from a carbon or the like re moved by machining without any effect on a diamond body, machining a dia mond at a high speed at a high accuracy, and forming a smoothly machined surface. CONSTITUTION:A diamond 1 is machined by irradiating the diamond 1 with a light of a 190-360nm wavelength, such as a laser beam 10, in a plasma 8 of an atmospheric gas, such as an oxygen, hydrogen, or inactive gas.