Abstract: An electric discharge machining apparatus including a first power source for applying machining voltage to a machining gap to generate an electric discharge, a second power source for applying voltage of equal to or lower than 20 V to the machining gap, a transistor switching bridge connected to both the workpiece and the tool electrode, a switch for selectively connecting one of the first and second power sources to the transistor switching bridge, a transistor controller for controlling on/off switching operation of the transistor switching bridge to alternatively change polarity of voltage being applied to the machining gap, a contact detector for electrically detecting the contact between the workpiece and the tool electrode when output of the second power source is applied across the machining gap, and an NC device which controls the switch so that the first power source is connected to the transistor switching bridge when the application of the machining power is required while the second power source i

Abstract: An electric discharge machining apparatus for machining a workpiece by supplying a series of voltage pulses to a machining gap formed between the workpiece being machined and a tool electrode, comprises a machining power supply for supplying voltage to the machine gap; a switching transistor connected between the machining power supply and the machining gap for pulsing the output voltage of the machining power supply; a gate pulse generator is provided for generating a gate pulse signal having an ON time and an OFF time to control on/off switching operation of the switching transistor so that switching transistor is in non-conducting state when the gate pulse signal is OFF, a monitoring power supply is connected in parallel with the switching transistor, and; a faulty transistor determination circuit is provided which determines if a switching transistor has failed when current flows from the monitoring power supply through the switching transistor even though the gate pulse signal is OFF.

Abstract: A wire-cut EDM method and apparatus for machining to a fine surface roughness of 1 .mu.m Rmax or less. Two power supplies and a electrode polarity switching system are used. A first high energy power source is used for initial profile cutting and may also be used for one or more later cuts while the machining pulse parameters, and feed rate and offset are adjusted for increasing less rough surface finishes. The wire electrode is held at negative machining potential. A second power supply and smaller offset values are used for later cuts to create lower values of surface roughness, while still maintaining the wire electrode at a negative machining potential. Finally, in order to create a fine finished surface (Rmax.ltoreq.1 .mu.m), the offset is further reduced and the wire electrode polarity is reversed.

Abstract: A method and apparatus for screening, sensing, or diagnosing disease states by obtaining a plurality of electrical impedance data measurements in organized patterns from two anatomically homologous body regions, one of which may be affected by disease. One subset of the data so obtained is processed and analyzed after structuring the data values as elements of an n.times.n impedance matrix, and deriving from these matrices their eigenvalues and eigenvectors. The matrices and their derivatives are then related by their characteristics to normal or disease states.