Wire EDM CNC Prepress Updated August 2026

Wire EDM Spark Gap & Profile Offset Calculator

Calculate wire radius compensation ($R_w$), electrical discharge spark overcut ($S_g$), total toolpath offset ($H$), multi-pass rough/skimming offsets, minimum inside corner radii, and workpiece cutting speed for precision 2-axis and 4-axis Wire EDM machining.

1. Wire EDM & Workpiece Setup

Brass / Coated Wire Diameter (mm)

Standard tool steel & extrusion die cutting typically uses 0.25mm brass wire.

Workpiece Material

Workpiece Thickness (mm)

1.000 in (25.4 mm)

Total Passes Planned

More skims reduce wire deflection and recast layer.

Machining Geometry Type

Total Contour Perimeter (mm)

Combined length of all cutting toolpaths for time estimation.

2. Offset Vector & CAM Parameters

Wire Radius ($R_w$) 0.125 mm (4.9 mil)

Roughing Spark Gap ($S_g$) 0.035 mm (1.4 mil)

Total Roughing Toolpath Offset ($H_1$) 0.160 mm (6.3 mil)

Total Single-Pass Cut Kerf ($K$) 0.320 mm (12.6 mil)

CAM Multi-Pass Compensation Schedule

Pass 1 Offset (Rough Cut): 0.160 mm

Pass 2 Offset (Skim 1): 0.140 mm

Pass 3 Offset (Skim 2): 0.132 mm

Pass 4 Offset (Skim 3): 0.128 mm

Min Inside Corner Radius ($R_{min}$) 0.130 mm (5.1 mil)

Estimated Total Cut Time 24.5 min

Wire EDM Centerline vs Offset Contour Geometry

Importing Scans or Sketches into Wire EDM CAM?

Wire EDM CNC controllers (Sodick, Fanuc Robocut, Mitsubishi, Makino, GF AgieCharmilles) require continuous, zero-gap G02/G03 tangent arcs and closed polylines. Faceted line segments cause wire shudder, micro-grooving, and feed rate drops. SpotItLive converts raster images, paper blueprints, and sketches into clean, tangency-aligned DXF/SVG vector profiles ready for toolpath generation.

Vectorize EDM Profiles Now →

Wire EDM Machining Speed & Surface Finish Table

Typical cutting speed rates (μm/min or mm²/min), surface roughness ($R_a$), and skim pass schedules for 0.25mm brass wire in submerged deionized water.

Material Group	Roughing Speed Rate	1-Pass $R_a$	3-Pass $R_a$	4-5 Pass $R_a$ (Mirror)	Recast Layer
Hardened Tool Steel (D2, A2, H13)	180 - 240 mm²/min	2.8 - 3.2 µm	0.7 - 0.9 µm	0.18 - 0.25 µm	1 - 3 µm after skims
Tungsten Carbide (WC-Co)	90 - 130 mm²/min	2.2 - 2.6 µm	0.5 - 0.7 µm	0.12 - 0.18 µm	< 1 µm (requires AC spark)
Stainless Steel (304, 316)	160 - 210 mm²/min	2.6 - 3.0 µm	0.6 - 0.8 µm	0.20 - 0.28 µm	2 - 4 µm
Aluminum (6061-T6, 7075-T6)	250 - 350 mm²/min	3.2 - 3.8 µm	0.9 - 1.2 µm	0.35 - 0.45 µm	High oxidation layer
Titanium (Grade 5 / Ti-6Al-4V)	120 - 170 mm²/min	2.5 - 2.9 µm	0.6 - 0.8 µm	0.22 - 0.30 µm	Avoid hydrogen embrittlement
Inconel 718 / High-Temp Alloys	110 - 150 mm²/min	2.4 - 2.8 µm	0.5 - 0.7 µm	0.18 - 0.24 µm	Low thermal conductivity

Key Prepress Rules for Wire EDM Vector DXF Geometry

Start Hole Placement: Always locate wire start holes inside scrap slug areas or lead-in relief tabs, maintaining at least 1.5× wire diameter distance from the finished part boundary.
Inside Corner Relief Fillets: Because the wire has a physical radius plus spark gap ($R = d_w/2 + S_g$), sharp 90° inside corners are physically impossible. Add corner relief "dogbone" or tangent fillets ($R \ge 0.14\text{ mm}$ for 0.25mm wire) in your vector master.
Slug Retention Tabs: Leave a 0.5 - 1.0mm unmachined bridge (tab) on heavy internal cutouts to prevent the slug from tipping and shorting the wire against the lower guide before the roughing pass completes.
Continuous Tangency Arcs: Replace high-density faceted polylines with G02/G03 true circular arcs to allow constant high-speed servo motion without controller buffer stutter.