Choosing the right manufacturing process can mean the difference between a successful project and a costly do-over. While CNC milling and turning are versatile workhorses for many applications, some projects simply demand a different approach. Wire Electrical Discharge Machining (Wire EDM) uses electrical energy rather than cutting forces to remove material—and that fundamental difference makes it the superior choice in specific situations.
Here are five clear indicators that your project needs EDM instead of conventional machining.
1. Your Material Is Too Hard for Efficient Cutting
The Problem: Once materials exceed certain hardness levels, conventional machining becomes impractical or impossible. Cutting tools wear rapidly, cycle times skyrocket, and tool breakage becomes a constant concern. Materials like hardened tool steels (Rc 60+), tungsten carbide, cobalt alloys, and nickel superalloys can destroy carbide end mills in minutes.
Why EDM Works: Wire EDM doesn't care about material hardness. The process removes material through controlled electrical erosion, not mechanical cutting. The wire never touches the workpiece—there's a small gap maintained by the dielectric fluid, and material removal happens through rapid electrical discharges across this gap. This means hardened tool steel at Rc 62 machines just as easily as aluminum. Tungsten carbide, which would require diamond grinding or specialized tooling conventionally, is routine work for Wire EDM.
The practical result: consistent surface finishes, predictable cycle times, and no tool wear to factor into your costs. If you're working with materials specifically chosen for their extreme hardness or wear resistance, EDM is often the only economical path forward.
2. You Need Intricate Internal Features or Deep Narrow Slots
The Problem: Cutting tools need access. An end mill can only reach so deep relative to its diameter before deflection, chatter, or breakage become issues. Internal pockets with narrow openings, deep thin-wall sections, and complex internal profiles push conventional machining to its limits—or beyond them.
Why EDM Works: Wire EDM only requires a small starting hole (often created by EDM drilling) and can then cut in any direction through the material. The wire can navigate tight internal passages, create deep narrow slots, and machine intricate internal geometries that would be physically impossible with rotating cutting tools. There's no tool pressure causing deflection, and while wire EDM does have depth limitations due to wire deflection, it can achieve much greater depth-to-width ratios than conventional machining.
This makes Wire EDM the go-to process for stamping die components with complex internal forms, injection mold cavities with deep ribs or narrow cooling channels, and any part where internal features are inaccessible to conventional tooling.
3. Tight Corner Radii Are Non-Negotiable
The Problem: Every end mill creates an internal corner radius equal to the tool radius. A 1/8" end mill leaves a 0.0625" radius in the corners. Smaller tools create smaller radii but are fragile and slow. Many precision applications—particularly in stamping dies and molding applications—require much sharper internal corners than conventional machining can deliver.
Why EDM Works: Wire EDM can achieve extremely tight corner radii, limited only by the wire diameter and the offset required for the electrical gap. With standard wire, corner radii in the range of 0.002" to 0.004" are achievable. This is an order of magnitude sharper than what's practical with conventional machining and often makes the difference between a functional part and one that requires secondary operations or design compromises.
For applications like keyways, punch and die work, or mold components where sharp internal corners are critical, Wire EDM eliminates the compromises inherent in end mill geometry.
4. Your Part Has Thin Walls or Delicate Features
The Problem: Conventional machining applies cutting forces to the workpiece. Even with careful tool selection and optimized feeds and speeds, these forces can deflect thin walls, distort delicate features, or cause vibration that ruins surface finish. Parts with thin ribs, tall narrow features, or low-rigidity sections are challenging to machine conventionally without deformation or dimensional errors.
Why EDM Works: Wire EDM applies virtually no mechanical force to the workpiece. The thermal energy that removes material is highly localized and controlled, and the dielectric fluid maintains stable conditions. This means thin walls maintain their intended dimensions, delicate features remain intact, and parts that would deflect under cutting pressure come out accurately.
This advantage extends to materials that are soft or prone to work hardening. Conventional machining can create stress, distortion, or work-hardened surfaces that affect subsequent operations. EDM removes material without these mechanical complications.
5. The Part Exceeds Standard Machining Capacity
The Problem: Most job shops have machining centers with travel in the range of 20" x 16" x 20" or similar. Larger parts require specialized equipment that many shops simply don't have. Even when oversized machining centers are available, fixturing heavy workpieces and managing long cycle times become major challenges.
Why EDM Works: Large Wire EDM machines can handle significantly oversized work, and the process remains efficient at these scales. At Infinity EDM, our largest Wire EDM machines can accommodate work that exceeds what most machining centers can handle, and we can wire multiple large pieces simultaneously. There's no need to section parts or use multiple setups to stay within machine travel limits.
For shops working with large stamping dies, mold bases, or industrial tooling, having access to oversized Wire EDM capacity means avoiding the compromises and complexity that come with trying to machine large parts conventionally.
Making the Right Choice
These five situations aren't exhaustive, but they represent common scenarios where Wire EDM becomes the logical choice over conventional machining. The key is understanding that Wire EDM isn't a specialty process for exotic applications—it's a practical solution when material properties, geometric requirements, or size constraints make conventional machining inefficient or impossible.
The best approach is often hybrid: rough out with conventional machining where it makes sense, then finish with EDM where precision, geometry, or material properties demand it. Understanding when each process excels is how successful toolrooms keep projects on schedule and within budget.
If you're facing any of these five situations, it's worth having a conversation with an EDM specialist before committing to a machining approach that may not deliver the results you need.