Wire EDM

A hypothetical 0.250 mm wire and 0.015 mm discharge gap per side give 0.280 mm kerf and 0.140 mm center offset. For a 10.000 mm internal square, opposite straight center tracks are 9.720 mm apart. Corner geometry, wire lag and trim offsets require qualified settings and finished-feature inspection.

A traveling electrode cuts a programmed path by discharges in dielectric fluid. Confirm electrical conductivity and qualify the material condition, wire and settings. Sodick, wire-EDM mechanism, undated

Specify stock condition, thickness and start-hole access. Trial unfamiliar carbide binders, conductive ceramics or layered stock.

Geometry, access and kerf

Wire EDM normally requires a path for the wire through the workpiece. Plan how the wire reaches an internal contour—typically through a prepared start hole—and distinguish that access from a blind cavity that cannot be swept by the wire. Keep fixture and upper/lower guide access in the manufacturing review, not only the final CAD outline.

Reliable EDM's handbook explains that the spark gap makes the cut wider than the wire and that inside corners retain a radius. It also discusses wire trail-off and barreling, which affect corner and through-thickness geometry. A small wire is therefore not by itself proof of a sharp corner or constant profile through a tall workpiece. Confirm the actual cutting conditions, offsets and inspection coverage. Reliable EDM, Complete EDM Handbook, chapter 5, undated extract

Define straight or tapered walls and the relationship between upper and lower profiles. The fixture must hold the work while leaving the intended cutting and flushing regions accessible. Plan support and removal of the released slug so that the final separation is an intentional operation rather than an uncontrolled change in workholding.

Dielectric and wire control

Makino's wire-EDM tutorial describes deionized water as a common dielectric and identifies conductivity, flushing and tooling rigidity as process concerns. Flushing removes debris, but its forces can also influence the supported workpiece. The absence of conventional tool cutting force does not eliminate all mechanical loading or fixture deflection. Record the actual dielectric-management and nozzle arrangement used in the qualified route. The archived tutorial is background guidance, not a current universal conductivity or flushing-pressure recipe. Makino, wire-EDM tutorial, undated archive

Water is not universal. Sodick identifies oil-based dielectric machines in its precision wire-EDM range, including the AP series. A process developed on a water machine should not be transferred unchanged to an oil machine or vice versa. State the machine configuration and relevant material/process conditions when comparing finish and accuracy evidence. Sodick, machine-family descriptions

Roughing, trim passes and movement

The first cut and subsequent skim or trim cuts have different roles. Reliable EDM describes skim cutting for greater accuracy and finer finish and notes that residual stresses can move material even after prior stress relief. The ordered tolerance and condition determine the needed sequence; there is no universal number of passes. A successful first contour does not establish the released component's final dimensions. Reliable EDM, chapter 5

Sodick's report of its ALC400P at BI-MU, October 13–16, 2026, describes iGroove rotating the wire during skim cutting to present an unconsumed wire surface to the workpiece. This is a bounded example of machine-specific control intended to improve surface and geometric results, not proof that every wire machine has the function or that it eliminates part qualification. Confirm installed options and the demonstrated process. Sodick Europe, BI-MU 2026 report

Surface integrity is separate from finish

Newton and colleagues' original study, published July 15, 2009, investigates recast-layer formation in wire-EDM Inconel 718. Across its tested conditions, average recast thickness increased with spark energy, peak current and pulse duration; the layer was variable and carried tensile residual stresses. These observations support material- and parameter-specific verification, not a universal recast depth for EDM. ORNL, original research record

Specify required surface-integrity examinations independently from roughness and size. A low Ra measurement does not report recast thickness, cracks or residual stress. If subsequent polishing or another removal step is required, define the final geometry and inspection stage after that work. Do not translate “non-contact cutting” into “no thermal effect,” or treat a generic finishing-pass label as evidence that the altered surface meets the application requirement.

A bounded historical producer example

Mitsubishi Electric's MP-series brochure, effective July 2014, gives a circular-machining example using 0.2 mm brass wire and 30 mm SKD11 steel, with specified prior treatments and ±0.5°C room-temperature conditions. The listed treatments include sub-zero treatment, high thermal tempering, stabilization and demagnetization after quenching. Those details illustrate why a catalog result is conditional, not a capability to assign to an arbitrary untreated workpiece or shop environment. The brochure itself calls its processing data reference information. Mitsubishi Electric, printed p. 10 and back cover

Original kerf-offset example

Assume an invented straight cut with 0.250 mm wire diameter and a uniform 0.015 mm discharge gap on each side:

nominal kerf = 0.250 + 2 × 0.015 = 0.280 mm

wire-center offset from the intended wall = 0.250 / 2 + 0.015 = 0.140 mm

For a hypothetical 10.000 mm square internal opening, the wire-center tracks along opposite straight walls would be 9.720 mm apart. This only describes the straight portions: an internal corner cannot be made infinitely sharp by that offset.

Confirm compensation direction and corner control with the qualified machine, wire and material. Account for wire deflection, lag and the offsets used on successive trims.

Manufacturing handoff and acceptance

Provide the drawing/model revision, conductive material and heat-treatment condition, thickness range, start/access requirements, datums and released-slug plan. Agree rough/trim sequence, final cleaning and any surface-removal operations. Define dimensional coverage through the thickness, taper/corner requirements, texture and ordered surface-integrity criteria separately.

Request evidence for the delivered component and actual process configuration. Machine positioning specifications, historical demonstration results and finished-part conformance answer different questions. The source examples and original arithmetic supply no universal cutting speed, gap, wire tension, pressure or pass-count recipe.