Showing papers on "Electrical discharge machining published in 1974"

Dense polycrystalline silicon carbide

Abstract: A dense silicon carbide material having improved electrically conducting properties is disclosed which is prepared by forming a homogeneous dispersion of silicon carbide, a sufficient amount of boron nitride, and optionally a boron containing additive and hot pressing the dispersion at a sufficient temperature and pressure whereby a dense substantially nonporous ceramic is formed. The silicon carbide material can be machined by electrical discharge machining or by electrochemical machining.

Spark discharge and electro-chemical erosion machining apparatus

Abstract: In electro-erosion machining using a filamentary erosion electrode, a dielectric flushing medium (for spark-discharge erosion) or an electrolyte fluid (for electrochemical erosion) is fed from an outlet to the working area of the electrode in the direction of the electrode axis and in contact with it so as to cool the electrode and to reduce changes in the machining characteristics with changes in cutting direction. A continuously operable regenerating system, including deionising apparatus which is brought into, and out of, operation under the control of a conductivity measuring device, is provided for regenerating the used dielectric flushing medium in spark-discharge erosion machining.

Method of and system for the controlling of an apparatus for the electric discharge machining of a workpiece

Abstract: Discrete electric-discharge pulses are applied across a dielectric-swept gap between an electrode and a workpiece by triggering an ON-OFF switch between its conductive and nonconductive states in accordance with parameters of the gap so that per pulse adaptive control of the individual machining discharges is effected. An integrator responsive to the gap current, may be used to operate the switch means which may be turned on upon the detection of a pilot discharge. The number of unsatisfactory discharges is detected and, if this number exceeds a predetermined level, is used to control a gap parameter. The integrator signal may be digitalized for accumulation in a counter controlling pulse duration and other parameters.

Methods and equipment for machining electrodes

Abstract: A rough-cut blank is machined to provide a spark erosion electrode for use in the manufacture of an extrusion tool by bonding the blank to a base plate, fixing the base plate to a milling machine table and milling the blank. The milled blank is subsequently detached from the base plate by breaking the bond between the blank and the base plate.

Wire electrode feed system for electrical discharge machining

Abstract: A wire feed system for an electrical discharge machining apparatus and machine tool. The workpiece is supported for movement along two coordinate axes in the X- and Y-direction through electrically controlled stepping motors in a manner which is well known to the art. The electrode is of a wire or band configuration and is so supported, guided, and driven that the cutting portion of the electrode which is aligned with the workpiece before and during cutting remains properly oriented and travels without bend or distortion in its path. The improvements in the support and drive mechanism for the wire electrode include a particular arrangement of driving and driven rollers for providing a constant pulling force on the wire and a set of orthogonally oriented guide rollers for holding the wire electrode in a predetermined path proximate the workpiece.

Vacuum delay valve

Abstract: A method of manufacturing an orifice delay valve having an apertured plate which is formed by coining a section in the plate, eroding a portion of the coined section by electrical discharge machining followed by ultra-sonic cleaning of the plate.

Method and apparatus for regulating the gap distance in electroerosin machining

Abstract: A workpiece-supporting table of an electro erosion machining equipment is provided with a mechanism for subjecting the workpiece to a circling motion of continuously variable radius during operation from zero to a maximum value. The same tool electrode can be used, without withdrawal from the work, for coarse machining at first and fine machining under circling movement immediately thereafter.

Pulse generator for electro-erosion machining apparatus

Abstract: A pulse generator for an electro-erosion machining apparatus wherein electrical discharges occur at a machining zone formed between an electrode workpiece and an electrode tool, the pulse generator comprising a capacitor charged from a source of direct current through an inductance and a switch for discharging the capacitor through the primary of a transformer, the electrode tool and the workpiece being connected across the secondary of the transformer, the capacitor being charged at a predetermined current rate and being discharged when the voltage across the capacitor reaches a preset level.

Electrical discharge machine with evolved-gas detoxification

Abstract: An electrical discharge machining apparatus in which an electrode is juxtaposed with a workpiece across a gap filled with a dielectric liquid is provided with means for collecting gases from immediately above the surface of the dielectric liquid, evaluating these gases and detoxifying them by rendering them noncombustible and nonexplosive and nonhazardous to life.

Electrical discharge machining apparatus with monitoring circuit and means to check the operability of the monitoring circuit

Abstract: A circuit for controlling an EDM process in which a logical monitoring circuit is used to detect a wrong discharge pulse out of the simultaneous occurrence and absence of certain electrical characteristics in the electrical discharge, as for example the absence of a high frequency component on the discharge voltage, as a criterion for an arc condition, the circuit including an input device connected to supply test signals to the monitoring circuit to simulate a wrong discharge pulse and thus enable checking of the monitoring circuit.

Wire electrode protection system for electrical discharge machining

Abstract: A wire feed protection system for an electrical discharge machining apparatus and machine tool. The workpiece is supported for movement along two coordinate axes in the "X" and "Y" direction through electrically controlled stepping motors in a manner which is well known to the art. The electrode is of a wire or band configuration and is so supported, guided, and driven that the cutting portion of the electrode which is aligned with the workpiece before and during cutting remains properly oriented and travels without bend or distortion in its path. When the wire breaks, bows or otherwise is caused to lose tension, a switch is operated to interrupt machining power pulses being supplied to the machining gap. For this purpose, a switch is located at one or more critical and predetermined locations in the wire electrode path, with the switch actuator in each case in engagement with the wire during transversal.

Electric Discharge Machining

Abstract: Compared to other fabrication techniques, spark machining is a relatively unknown process. However, for certain applications it is the only method that can be used. Conversely, if other methods can achieve satisfactory results, then spark machining is probably not the best method. Hence, there are applications for spark machining, often referred to as EDM (Electric-Discharge Machining) that are unique to this process.

Moulded spark erosion machining electrode - made of conductive particles and bonding medium which can be graphitised, coked or cracked

Abstract: Electrodes for use in electrochemical machining and/or spark erosion operations are moulded in a master mould from a conductive powder (copper or graphite) and a bonding medium, suitable for cracking, coking or graphitizing. The bonding medium provides adequate strength when green and is cracked, coked or graphitized during the machining operation. Such an electrode can be produced quickly and simply. It has a high flexibility in its surface configuration.

Apparatus for electrical discharge machining employing periodic extended pulse off time

Abstract: Electrical discharge machining is provided by generating a series of rectangular machining power pulses at a controllable on-off time duration. Provision is made for introducing extended off time duration between groups of pulses to contribute to the improvement of cutting stability. In one alternate embodiment of the invention, a single on time pulse is provided intermediate a pair of spaced pulse groups.

Gates timing system for electrical discharge machining

Abstract: Electrical discharge machining is provided by generating a series of rectangular machining power pulses of a controllable on-off time duration. A circuit is included for specialized machining by providing spaced machining power pulse groups, and between each group there is included a single on-time pulse. A count down system is used to preset the number of pulses desired in each group, with the off-time between groups and single pulses being selectively adjustable in the circuit.

Graphite Electrodes in Electric Discharge Machining

Abstract: Machining ability in electric discharge machining is judged by means of four factors, “machining speed”, “electrode wear ratio”, “surface roughness of worked pieces”and“isotropism of working clearance”. Since it is generally believed that the machining ability depends largely on the properties of graphite materials used as the tool-electrodes, it is obviously useful for the development of the most suitable graphite materials to make clear the relationship between the properties of graphite electrodes and the factor influencing machining ability.This report describes some of the test results examined on a series of graphite materials of various physical characteristics as well as of various grain constitution (both in shape and size) in relation to the effects of their properties on those judging factors. Experiments were carried out on an electric discharge machine currently in use, with graphite as an anodic tool-electrode under the common discharge conditions that have been proven to be optimum for graphite electrodes.The results obtained are:(1) “Machining speed”increases apparently with lowering electric resistivity of graphite electrodes as being generally considered, but since the resistivity is influenced decisively by the grain size distribution of raw materials, “machining speed”would rather be regarded to depend on the grain size.(2) “Electrode wear ratio”and“surface roughness”are, in contrast to the general belief, independent of any of the physical properties of the electrodes but depend significantly on the grain size distribution.(3) It should be pointed out that the above mentioned two factors tend to change sigmoidally in the range of mean grain size of 5 to 10μm.(4) “Anisotropy ratio”of working clearance decreases with decreasing anisotropy ratio of graphite materials being represented by the ratio of CTE's (coefficient of thermal expansion) measured in different directions of“across grain”and“with grain”.

Maximum power transfer in relaxation generator for electric discharge machining

Abstract: In the basic relaxation generator for electric discharge macchining, a reverse voltage usually appears across the discharge capacitor. The effect of this reverse voltage on maximum power transfer to the discharge capacitor is discussed. It is shown that the amplitude of the reverse voltage considerably reduces the power transferred to the capacitor per cycle Connecting a diode across the discharge capacitor results in better utilization of power. Resulting improvements in machining rate and tool wear are also explained.