Electrical discharge power unit, the heart of Sodick's product for electrical discharge machining.

In high-speed machining on a wire-cut electrical discharge machine, for instance, a power circuit that applies currents of 1000 A for 1 microsecond or less and a pulse control unit that controls the currents generate pulse currents repetitively and stably.  In finish machining, a pulse control unit generates pulse currents of the order of a nanosecond repetitively and stably.  In a die-sinking electrical discharge machine, on the other hand, a pulse control unit that optimally controls the pulse width and current value generates stable pulse currents to minimize electrode weare.  These control units, which are generically called electrical discharge power units, serve as the driving force of the high performance of Sodick's products as their hearts.  (Even light travels only about 30 cm in a nanosecond.)

Mechanism of Electrical Discharge Power Units

The history of the technical development of Sodick began with the development of an electrical discharge power unit, which constitutes the heart of an electrical discharge machine.  Electrical discharge machining proceeds in a dielectric fluid tank by generating electrical discharge between two energized electrodes, namely a machining electrode and a workpiece, and gradually reducing the distance between the two.  The material of the workpiece is melted and vaporized by the energy of the discharge, and blown away by the high pressure generated from the discharge.  The electrical discharge machining proceeds through repetition of the above phenomenon tens to hundreds of thousand times a second.

Desired performance of the electrical discharge machining is achieved through control of the discharge pulses, that is, by controlling the method and duration of the energy supply and the distance between the electrodes.

• Wire-cut discharge machining
  
  

  Mechanism of Wire-cut EDM

  1. Homogeneously generating a high peak voltage of 1000 A or more within a period of a microsecond (TM circuit)
  2. An electrolysis free power unit that prevents the electrolysis by the machining fluid and power supply (BS circuit)
  3. A power circuit for efficient intermediate finishing (ALPM circuit)
  4. A control power circuit for high-speed finish machining and pulse control for the machining of a corner (HF circuit)
  5. Finishing circuit for achieving a surface finish Ry on the order of several tenths of a micrometer (Super-PIKA circuit)
  6. An optional special circuit that minimizes the chipping of the machined surface
• Die-sinking electrical discharge machining
  
  

  Wire-cut surface

  1. Accurately and repetitively applying currents of one to several amperes each during one to several microseconds (SVC circuit)
  2. Homogeneously and repetitively applying comparatively long pulse currents each during several tens of microseconds to several milliseconds (no-electrode-consumption circuit)
  3. Achieving mirror polishing (PIKA circuit)
• Common
  
  Controlling machining pitch on the order of 0.1 μm using K-SMC capable of calculating distance to an accuracy of 10 nm (quickly reactive linear motor servo control circuit)

Electrode & work sample

Work sample Material : STAVAX Surface : 0.36µmRz

Discharge gap

The electrical discharge machining in the period around 1960 was mainly electrode-wearing machining wherein both the electrode and workpiece were consumed by the discharge energy, and for this reason, its application was limited principally to the so-called through-hole machining.  Thereafter, the progress of transistor technology led to the development of no-electrode-wearing electrical discharge circuits, and as a result, the electrical discharge machining became applicable also to cavity machining; thus the technique became indispensable for the present-day mold machining.  The key development targets in the improvement of the performance of electrical discharge machining include issues such as "how to supply discharge energy efficiently to the machining gap", "how to maintain an optimum distance of the machining gap" and "how to maintain adequate electrical discharge continually."  Therefore, it has been necessary in the pursuit of the best possible performance of electrical discharge machining, to continue to improve discharge power units keeping pace with the advance in electronic devices and control technology.