Wire EDM vs CNC Milling

Published on: April 14, 2022

Wire electrical discharge machining (WEDM) is a non-traditional machining process that uses a thin wire electrode and electrical discharge (sparks) to cut through a workpiece composed of conductive material. For projects with certain characteristics, using wire EDM instead of CNC milling can significantly improve the quality of the finished part and reduce costs. In some cases, it is the only reasonable choice.

For many without a background in WEDM, it might be challenging to choose which method to implement when. Xact, as a provider since 1984 of precision wire EDM services to die, mold, and part manufacturers nationwide, can help you to determine the best process choice for your project. Xact Wire EDM is one of the largest and most experienced wire EDM shops in the country.

Here are six specific examples where wire EDM makes more sense than CNC milling:

Extremely hard or gummy metals

With wire EDM the angle of cutter entry and material hardness are not an issue, because sparks do the cutting. Wire EDM is suitable for workpieces made of any conductive material including superalloys, hardened tool steel, nickel, copper, stainless, and tungsten carbide.

Sharp internal corners

Wire EDM is ideal for machining sharp internal corners which are unachievable with an end mill. Because the wire electrode is so thin (down to .004” or .10mm), wire EDM can create extremely tight (virtually dead sharp) internal corner radii.

Complex shapes

Wire EDM is ideal for creating parts or features with unique or complex geometry which can be difficult or impossible for a milling cutter. CNC milling does remove metal more quickly than wire EDM. However, for highly complex parts, wire EDM is in many cases more efficient overall in creating the details required within the specified tolerances.

Precision machining delicate features

Wire EDM can achieve very tight tolerances, as low as +/-0.0002” (and tighter in some cases). There is very little or no workpiece distortion since the cutting is done using electrical discharge without physical contact. No cutting forces applied results in simpler fixturing as well.

Deep cutting

For cuts where the tool length to diameter ratio (L:D) is high, wire EDM is better than CNC milling. Mills with a high L:D ratio are subject to chattering, which is not an issue for a wire electrode.

Fine surface finish

Wire EDM can produce a much higher quality surface finish free of the scallop or swirl patterns caused by traditional machining.

Lights-out manufacturing

Because tool wear is not an issue, wire EDM can process multiple parts at once, even on unattended machines. We run wire EDM machines overnight and consistently turn out parts with a very high degree of repeatability.

Is wire EDM right for your project?

Wire EDM and CNC milling are used in combination for mold making. It is common for builders to use a CNC mill to start the process and then switch to wire EDM for the deepest cuts and detail work. Because XACT Wire EDM exclusively offers wire EDM and small hole EDM services, we are the ideal company for die and mold makers to partner with, regardless of what your in-house EDM capabilities may be. We are experts in wire EDM and not a competitor.

Production parts manufacturers can do the same. Milled blanks can be sent to Xact for the precision details to be added. Xact provides this service to many CNC shops in various industries including medical.

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