Frozen Processing for EDM (Air/Space, Nuclear, Medical)
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  1. #1
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    Default Frozen Processing for EDM (Air/Space, Nuclear, Medical)

    Since I point many of my customers to this incredible website for EDM knowledge, I thought I would post something that is a regular question from them.
    It is old news to most, but maybe it will help someone out...


    Why do we have to freeze our EDM process for Aerospace, Nuclear, Military and Medical parts?

    Frozen Process (EDM) - A process of EDM manufacturing for which no variation is allowed from the original process that yielded a passing metallographic sample.

    EDM uses a thermal process for removing material.
    "The Spark" is all about delivering heat to the work-piece, melting a relatively small amount of material, turning off the heat source and allowing the molten material to cool/flush away, and then starting the process all over again.
    With heat (10,000+ deg/C) comes unwanted side affects.
    HAZ (Heat Affected Zone) is work-piece material that has been altered by the thermal process, but was not removed.
    It is comprised of redeposited/degraded electrode and work-piece material, annealed portions of work-piece material, and micro-cracking.
    All of which can and has caused failures of the component or interacting components in the field.
    Nobody wants an airplane to crash on their house or a submarine to get stuck under the polar ice cap...

    Things such as EDM Spark Parameters(critical), Fixturing, Machine/Power Supply, Dielectric, Electrode Material/Geometry, Flushing Type and Number of parts run simultaneously must not be altered to ensure that parts run today have the same acceptable HAZ as what the first metallographically tested cycle yielded.
    Critical EDM Spark Parameters consist of anything that has potential the make the spark "hotter" and thus make the HAZ worse than the original metallographic sample (Amps, Volts, On-time, Polarity, Capacitance, Voltage type, Wave Form)
    Additional variables such as machine generator calibration and operator training are also of concern.

    These concerns also hold true with with other non-conventional machining processes that yield a HAZ (ECM, ECG, Laser, Water-jet and SEG).


    Jay Crumb
    Advanced EDM, LLC

  2. #2
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    Default

    This is a highly underrated post, my good sir. Those hoping to move beyond typical die shop EDM work should be saving this for future reference. Wait... is HAZ really a thing with water jet?

    I miss the volleyball league!


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