Wire EDM Service
Precision wire EDM cutting at FIRMFG. We cut hardened tool steels, titanium, stainless, and tungsten carbide with tolerances to ±0.0001" and surface finishes down to 4 Ra µin. Complex geometries, tight corners, and micro features that conventional CNC cannot reach. ISO 9001 certified. Get a quote in 24 hours.
Wire EDM Service: Tight-Tolerance Cutting for Hard Materials & Complex Geometry
Wire EDM service at FIRMFG delivers ultra-precision cutting of electrically conductive materials using wire electrical discharge machining. A continuously feeding wire electrode — as thin as 0.004" (0.10 mm) — erodes material through controlled electrical sparks, producing geometries that are impossible to achieve with conventional CNC milling. Because the process is entirely non-contact, material hardness is irrelevant: wire EDM cuts fully hardened D-2 tool steel at 60 HRC just as easily as soft aluminum.
Our wire EDM department holds positioning accuracy to ±0.0001"(±0.0025 mm) and achieves surface finishes as fine as 4 Ra µin(0.1 Ra µm) through multi-pass skim cutting. This makes wire EDM the process of choice for stamping dies, injection mold inserts, medical components, aerospace parts, and any application requiring sharp internal corners, narrow slots, or intricate 2D contours in hardened materials.
At FIRMFG, we operate multi-axis wire EDM machines capable of taper cutting up to ±30°, accommodating workpieces up to 300 mm (12") tall. Every part is backed by our ISO 9001:2015 certified quality system and inspected with CMM equipment. Whether you need a single prototype die insert or a production run of precision components, our engineers review every CAD file for manufacturability and provide free DFM feedback before cutting begins.
This guide covers everything you need to know about wire EDM machining — how the process works, our capabilities, material selection, process comparison, cost factors, design rules, and quality assurance. Use it as a reference when designing your next wire EDM part, or skip ahead and request a quote for an immediate price and lead time.
What Is Wire EDM?
Wire electrical discharge machining uses spark erosion through a traveling wire electrode to cut conductive materials with no physical contact and no cutting force.
Wire EDM (Wire Electrical Discharge Machining) is a non-conventional machining process that removes material through a series of rapid, controlled electrical discharges — sparks — between a thin wire electrode and the workpiece. Both the wire and the part are submerged in deionized water, which acts as a dielectric fluid. Each spark generates intense, localized heat (up to 12,000°C) that melts and vaporizes a microscopic amount of material. The dielectric fluid then flushes away the eroded particles, and the wire advances to the next position.
The wire — typically brass, 0.004" to 0.012" (0.10 to 0.30 mm) in diameter — feeds continuously from a spool through the workpiece and is discarded after a single pass. This ensures a fresh, uniform electrode surface at all times, contributing to the process's exceptional consistency. The wire never touches the workpiece; a spark gap of roughly 0.001" to 0.002" (0.025 to 0.05 mm) is maintained between them at all times.
Spark Erosion Principle
Each electrical discharge melts a microscopic crater in the workpiece. At cutting speeds of 0.5–3 in²/hour, thousands of sparks per second remove material with no mechanical contact, no cutting force, and no tool pressure on the part.
Non-Contact Cutting
Because the wire never touches the workpiece, there is zero mechanical stress, no tool deflection, and no workpiece distortion. Thin, delicate, and fully-hardened parts can be cut without risk of warping or cracking.
Key Difference from Conventional CNC Machining
Conventional CNC milling and turning rely on physical contact between a cutting tool and the workpiece. The tool must be harder than the material being cut, and cutting forces limit how thin walls, sharp corners, and small features can be. Wire EDM overcomes all three limitations simultaneously:
- No material hardness limit — the spark erodes any conductive material regardless of hardness, so fully hardened tool steel (60+ HRC) is cuttable.
- True sharp internal corners — the wire produces corners with a radius equal only to the wire radius plus spark gap, as small as 0.003" (0.076 mm).
- No cutting force — delicate features, thin webs, and fragile geometries are cut without deflection or distortion.
- Exceptional surface finish — skim passes produce finishes down to 4 Ra µin, often eliminating the need for secondary grinding or polishing.
Ideal Applications
Wire EDM excels at cutting hard materials (hardened tool steels, tungsten carbide, titanium), complex 2D geometries (intricate contours, narrow slots, sharp corners), and micro features (small holes, fine details, delicate profiles). It is the go-to process for tool & die making, precision mold inserts, medical device components, and aerospace parts where conventional machining cannot reach the required precision or geometry.
Wire EDM Capabilities
FIRMFG's wire EDM machines deliver sub-ten-thousandth accuracy, mirror-quality surface finishes, and taper cutting for complex 3D geometries.
| Capability | Specification |
|---|---|
| Positioning Accuracy | ±0.0001" (±0.0025 mm) |
| Surface Finish (Skim Pass) | 4 Ra µin (0.1 Ra µm) |
| Max Workpiece Size | 400 × 300 × 300 mm |
| Max Taper Cutting Angle | ±30° |
| Min Internal Corner Radius | 0.003" (0.076 mm) |
| Wire Diameter Range | 0.004" – 0.012" (0.10 – 0.30 mm) |
| Max Workpiece Height | 300 mm (12") |
| Quality Standard | ISO 9001:2015 Certified |
±0.0001" Accuracy
Positioning accuracy of one ten-thousandth of an inch is achieved through precision glass scales and thermal-stable machine construction.
4 Ra µin Finish
Multi-pass skim cutting produces mirror-quality surfaces that often eliminate secondary grinding or polishing operations.
±30° Taper Cutting
Independent upper and lower wire guides enable continuous taper cutting for draft angles, cones, and complex 3D profiles.
0.003" Min Corner
Using 0.004" wire, internal corner radii as small as 0.003" are achievable — far sharper than any rotating cutting tool.
Wire EDM vs Sinker EDM vs CNC Milling
Choosing the right process depends on material hardness, geometry complexity, tolerance requirements, and production volume. Compare wire EDM against the two most common alternatives.
| Process | Precision | Surface Finish | Complexity | Speed | Cost | Suitable Materials |
|---|---|---|---|---|---|---|
| Wire EDM | ±0.0001" | 4 Ra µin | Very High | Slow | Medium-High | Conductive only |
| Sinker EDM | ±0.0002" | 8 Ra µin | High (3D cavities) | Slow | High | Conductive only |
| CNC Milling | ±0.002" | 32 Ra µin | Moderate | Fast | Low-Medium | Most materials |
Process Selection Decision Guide
| Scenario | Recommended Process | Notes |
|---|---|---|
| Hardened tool steel, tight tolerance | Wire EDM | No contact, hardness irrelevant |
| Sharp internal corners / narrow slots | Wire EDM | Min radius 0.003" |
| Blind 3D cavity in hardened steel | Sinker EDM | Electrode form required |
| Open prismatic geometry, soft material | CNC Milling | Fastest, most economical |
| Large part, moderate tolerance | CNC Milling | Higher material removal rate |
When in doubt, send your CAD file to FIRMFG. Our engineers evaluate geometry, material, tolerance, and volume to recommend the most cost-effective process — and wire EDM is often combined with CNC milling in a hybrid workflow for optimal results.
Materials Compatible with Wire EDM
Wire EDM cuts any electrically conductive material. Below is a guide to the most common materials we process, with recommended wire diameters and expected cutting performance.
| Material | EDM Machinability | Recommended Wire Ø | Cutting Speed | Surface Quality |
|---|---|---|---|---|
| Tool Steel A-2 | Excellent | 0.010" | Medium | Excellent |
| Tool Steel D-2 | Excellent | 0.010" | Medium | Excellent |
| Tool Steel H-13 | Excellent | 0.010" | Medium | Excellent |
| Tool Steel M-2 | Excellent | 0.010" | Medium | Excellent |
| Tool Steel O-1 | Excellent | 0.010" | Medium | Excellent |
| Tool Steel S-7 | Excellent | 0.010" | Medium | Excellent |
| Stainless 304 | Good | 0.010" | Medium-Slow | Good |
| Stainless 316 | Good | 0.010" | Medium-Slow | Good |
| Stainless 17-4PH | Good | 0.010" | Medium-Slow | Good |
| Titanium Ti-6Al-4V | Good | 0.008" | Slow | Excellent |
| Tungsten Carbide | Fair | 0.008" | Slow | Good |
| Copper Alloy (C110) | Fair | 0.012" | Slow | Fair |
Material Conductivity Requirement
Wire EDM requires the workpiece to be electrically conductive. The spark must pass through the material to complete the circuit. All metals — including hardened tool steels, stainless, titanium, carbide, and copper — are conductive and cuttable. Non-conductive materials such as plastics, ceramics, glass, and most composites cannot be cut with wire EDM. For those materials, CNC milling, laser cutting, or waterjet cutting are the appropriate alternatives. Material hardness has no effect on EDM machinability — a fully hardened D-2 die at 60 HRC cuts at the same rate as annealed D-2, which is one of the process's greatest advantages.
Common Wire EDM Applications
Wire EDM is indispensable across industries that demand precision, complex geometry, or machining of hardened materials. Here are five sectors where the process delivers unmatched value.
Tool & Die Making
Wire EDM is the backbone of modern tool and die manufacturing. It cuts hardened tool steels after heat treatment, eliminating distortion from post-machining hardening and preserving critical tolerances.
Typical Examples
Progressive stamping dies, injection mold inserts, extrusion dies, blanking dies, form tools
Medical Devices
The medical industry relies on wire EDM for surgical instruments and implant components machined from titanium and stainless steel with burr-free edges and biocompatible surface finishes.
Typical Examples
Surgical forceps, bone saw blades, orthopedic implants, dental instruments, biopsy needles
Aerospace
Aerospace components demand extreme precision in exotic, difficult-to-machine materials. Wire EDM produces complex turbine and structural parts without inducing thermal stress or mechanical distortion.
Typical Examples
Turbine blade cooling slots, fuel system components, titanium brackets, nozzle segments
Automotive
Automotive prototyping and production tooling leverage wire EDM for high-wear components and precision fixtures. Hardened steel tooling is cut to final tolerance without grinding.
Typical Examples
Gear blanks, fuel injector components, transmission tooling, prototype brackets, fixtures
Electronics
Electronics manufacturing uses wire EDM to produce lead frames, connector molds, and precision stamping dies with features too fine for conventional machining.
Typical Examples
Lead frames, connector dies, EMI shielding prototypes, heat sink fins, micro-molds
Wire EDM Cost Factors
Understanding what drives wire EDM cost helps you optimize designs for manufacturability and reduce per-part pricing. Cutting time is the dominant factor.
Programming Time
CAM programming for complex 2D contours and taper cuts. Simple shapes program in minutes; multi-pass taper parts take hours.
Cutting Time
The dominant cost driver. Cutting speed depends on material conductivity, workpiece thickness, and required surface finish. Thicker parts cut slower per unit of travel.
Wire Consumption
Brass wire is consumed continuously as it feeds through the workpiece. Thinner wire costs less per foot but breaks more often, increasing downtime.
Workpiece Height
Taller workpieces require more cutting time per linear inch of travel. A 4" tall part takes roughly four times longer than a 1" tall part for the same contour.
Skim Pass Count
Roughing cuts are fast but leave a recast layer. Skim passes improve accuracy and surface finish but add cutting time. Precision parts require 2-4 skim passes.
Cost Estimation by Material & Complexity
| Material | Thickness | Complexity | Estimated Cost Range |
|---|---|---|---|
| Aluminum 6061 | 25 mm | Low | $80 – $200 |
| Stainless 304 | 15 mm | Moderate | $120 – $300 |
| Tool Steel D-2 | 20 mm | Moderate | $150 – $400 |
| Tool Steel D-2 | 50 mm | High | $400 – $900 |
| Titanium Ti-6Al-4V | 30 mm | High | $350 – $800 |
| Tungsten Carbide | 10 mm | High | $300 – $700 |
Estimates are for a single prototype part with standard lead time. Production volumes of 10+ units reduce per-part cost through setup amortization and stack cutting. Actual quotes vary with geometry, tolerance, and finish requirements.
Design Rules for Wire EDM
Wire EDM has unique design constraints driven by the wire diameter and spark gap. Follow these guidelines to achieve optimal accuracy, surface finish, and cost.
| Feature | Recommended | Minimum (Higher Cost) |
|---|---|---|
| Min Internal Corner Radius | Wire radius + spark gap (≈0.006") | 0.003" (0.076 mm) |
| Max Workpiece Height | 200 mm (8") | 300 mm (12") — reduced accuracy |
| Taper Cutting Angle | ±15° | ±30° (special wire guides) |
| Start Hole Diameter | 0.020" (0.5 mm) | 0.006" (0.15 mm) |
| Min Slot Width | Wire Ø + 2× spark gap | 0.008" (0.20 mm) |
| Wire Diameter | 0.010" (0.25 mm) | 0.004" (0.10 mm) |
Internal Corner Radius
The minimum internal corner radius equals the wire radius plus the spark gap. With 0.010" wire and a 0.001" spark gap, the minimum corner radius is approximately 0.006". Use 0.004" wire for sharper corners down to 0.003", but expect slower cutting and higher wire-breakage risk.
Stack Cutting Strategy
For thin parts under 10 mm, stack multiple sheets together and cut them in a single pass. This dramatically reduces per-unit cost by amortizing cutting time across the entire stack. Clamp sheets firmly to prevent dielectric leakage between layers.
Taper Cutting
Taper angles up to ±30° are achievable with special wire guides. Keep tapers under ±15° for best accuracy. Always specify the reference datum surface — the side from which the taper is measured — to ensure correct programming.
Start Hole Positioning
Every wire EDM cut begins from a pre-drilled start (threading) hole. Position start holes to minimize air-cutting travel distance between features. If the part has multiple internal cutouts, plan start-hole locations to reduce non-cutting wire travel and total cycle time.
DFM Checklist for Wire EDM Parts
- Ensure the workpiece material is electrically conductive — wire EDM cannot cut plastics, ceramics, or non-conductive composites.
- Provide a start hole (threading hole) or allow FIRMFG to drill one. Position it to minimize air-cutting travel distance.
- Design internal corners with a radius equal to or larger than the wire radius plus the spark gap to avoid wire breakage.
- Specify the required surface finish explicitly — a single roughing pass is faster but leaves a recast layer; skim passes improve finish and accuracy.
- Indicate taper angles and the reference datum surface on the drawing to ensure correct wire-guide programming.
- Consider stack cutting for thin parts — stacking multiple sheets reduces per-unit cost by cutting several parts in a single pass.
Quality Assurance
Every wire EDM part at FIRMFG is inspected with precision metrology equipment and backed by our ISO 9001:2015 certified quality management system.
CMM (Coordinate Measuring Machine)
Verifies dimensional accuracy to ±0.0001". Full 3D probing of critical features, profiles, and positional tolerances.
Optical Comparator
Projects part profile at 10×–50× magnification for visual inspection of geometry, angles, and edge sharpness against CAD overlay.
Surface Roughness Tester
Measures Ra in both µin and µm. Confirms skim-pass surface finish meets specification down to 4 Ra µin.
First Article Inspection (FAI)
The first part of every wire EDM batch undergoes full First Article Inspection. Critical features, dimensional tolerances, and surface finish are verified against the drawing on CMM equipment. The part is not released to production until FAI is approved. For aerospace and automotive customers, FAI reports are provided in AS9102 format.
- Full dimensional verification against CAD
- Critical feature CMM probing
- Surface roughness measurement on skim-pass surfaces
Available Inspection Reports
FIRMFG provides a range of quality documentation to meet industry requirements. Standard dimensional reports are included with every order; specialized reports are available on request.
- Dimensional inspection report (included standard with every order)
- CMM full inspection report (available on request)
- First Article Inspection report — AS9102 format (aerospace & automotive)
- Material test certificate (available on request)
- Certificate of Conformance (available on request)
Wire EDM Service FAQ
Answers to the most common questions about wire EDM machining services at FIRMFG.
QWhat is wire EDM and how does it work?
Wire EDM (Wire Electrical Discharge Machining) is a non-contact thermal cutting process that uses a continuously feeding thin wire electrode — typically brass, 0.004" to 0.012" in diameter — to cut electrically conductive materials. A controlled electrical spark erodes material from the workpiece through a dielectric fluid (deionized water). Because there is no physical contact between the wire and the part, material hardness is irrelevant — wire EDM cuts hardened tool steel as easily as soft aluminum.
QWhat tolerances can wire EDM achieve?
FIRMFG achieves wire EDM positioning accuracy of ±0.0001" (±0.0025 mm) on precision parts. With multiple skim passes, dimensional accuracy of ±0.0002" is routinely held on production tooling. Surface finish can reach 4 Ra µin (0.1 Ra µm) after fine-finishing skim passes. These tolerances are verified with CMM inspection equipment and reported on dimensional inspection reports.
QWhat materials can be cut with wire EDM?
Wire EDM cuts any electrically conductive material. Common materials include tool steels (A-2, D-2, H-13, M-2, O-1, S-7), stainless steels (304, 316, 17-4PH), titanium (Ti-6Al-4V), tungsten carbide, copper alloys, and even exotic grades like Inconel and Kovar. The material must be conductive — plastics, ceramics, and glass cannot be cut with wire EDM. Material hardness does not affect cutting speed or quality.
QHow thick of a part can wire EDM cut?
FIRMFG wire EDM machines accommodate workpieces up to 300 mm (12") thick. However, cutting speed decreases as workpiece height increases because each spark erodes less material per discharge. For parts taller than 200 mm, accuracy may be slightly reduced due to wire vibration. Very thick parts are cuttable but require longer cycle times and may need additional skim passes to maintain tolerance.
QHow long does wire EDM cutting take?
Cutting speed depends on material, thickness, wire diameter, and required surface finish. Typical cutting rates range from 0.5 to 3 in²/hour for steel. A simple 20 mm thick steel contour may take 2-4 hours, while a complex 50 mm thick tool steel part with multiple skim passes can take 10-20 hours. FIRMFG provides lead times of 3-7 days for most wire EDM parts, with rush service available.
QHow much does wire EDM cost?
Wire EDM pricing is driven primarily by cutting time. A simple aluminum part may cost $80-$200, while a complex hardened tool steel die can range from $400-$900. Key cost factors include material type and thickness, contour complexity, number of skim passes for surface finish, and wire consumption. FIRMFG offers free quotes with DFM feedback — upload your CAD files for an instant estimate.
Related CNC Machining Services
Explore our other CNC machining capabilities and material-specific landing pages.
CNC Micro Machining
Ultra-precision micro machining for miniature components with features down to 0.1 mm.
Learn MoreCNC Machining Service
Full-range CNC milling, turning, and 5-axis machining across 50+ materials.
Learn MoreCNC Machining Stainless Steel
Precision machining of 303, 304, 316, and 17-4 PH stainless steel alloys.
Learn MoreStart Your Wire EDM Project
Upload your CAD files and get a free wire EDM quote within 24 hours. Our engineers provide DFM feedback and process recommendations at no cost. ISO 9001 certified quality, tolerances to ±0.0001", and surface finishes down to 4 Ra µin.