Wire EDM
- Through cuts, insert profiles, and ejector pin holes
- Straight walls when the wire path can enter and exit the block
- Parting plates and slider tracks cut after heat treat
Glossary
Wire EDM for Injection Molds: Inserts, Ejector Pins & Parting Plates
Wire EDM uses a traveling wire electrode to through cut hardened mold steel for insert profiles, parting plates, ejector pin holes, and slider tracks. It complements sinker EDM on through geometry.
Definition
What Is Wire EDM?
Wire EDM uses a traveling wire electrode to through cut hardened mold steel for insert profiles, parting plates, ejector pin holes, and slider tracks.
Wire EDM cuts through hardened steel along a programmed path using a continuously traveling wire electrode.
Mold shops use it for insert outlines, parting plates, ejector pin holes, slider tracks, and through features that need a straight wall or tight corner.
It complements sinker EDM on geometry that can be cut from one side to the other.
Start and stop marks may appear where wire entry and exit are visible unless the process hides them on shutoffs.
Toolmaking
Wire EDM through cuts hardened mold steel
Insert profiles, ejector pin holes, and parting plates are common wire EDM jobs.
- Wire diameter sets minimum corner radius on insert outlines.
- Start holes often come from hole drilling EDM.
- Skim passes tighten shutoffs after rough wire cuts.
Versus sinker
Wire EDM vs sinker EDM
Different geometry problems, not competing labels for the same feature.
Sinker EDM
- Blind cavities, deep ribs, and sharp internal corners
- Logos and textures with shaped electrodes
- See the sinker EDM glossary entry for ram EDM detail
Tooling
Typical wire EDM on production molds
These features show up on mold build plans, not on part drawings alone.
Wire EDM insert profile cuts after heat treat for pocket fit
Ejector pin holes and through slots in hardened plates
Parting plate and slider track outlines with tight clearance
Review
Drawing notes that affect wire EDM time
Wire diameter selection and corner radius drive spark gap and skim time.
Minimum internal corner radius tied to wire diameter and overburn
Whether wire entry marks must land on non cosmetic shutoff steel
Insert clearance and parallelism after wire cut on mating plates
Wire EDM wins over CNC milling when steel is already hardened or internal corners are tighter than end mill radius
Recast layer on shutoff faces may require skim passes; note acceptable finish on drawing
Go deeper
EDM family links
Open the guide that matches your geometry question.
Sinker EDM
Blind ribs and shaped electrodes.
Sinker EDMHole-drilling EDM
Wire start holes and deep vents.
Hole-drilling EDMEDM overview
Sinker, wire, and hole drilling hub.
EDM overviewEDM finish
RFQ notes for EDM texture on parts.
EDM finishCore
Wire cut inserts on the core half.
CoreCavity
Wire cut inserts on the cavity half.
CavityMold base
Plates that receive wire cut inserts.
Mold baseVisual reference
Photos from molding and tooling programs
Images are selected from the NetProto Forge media library for this topic.
Wire EDM machine cutting with sparking wire through mold ste
Wire EDM machine cutting with sparking wire through mold steel
Wire EDM finished mold insert profile on steel plate
Wire EDM finished mold insert profile on steel plate
Ejector pin holes cut by wire EDM in hardened mold plate
Ejector pin holes cut by wire EDM in hardened mold plate
FAQ
Frequently Asked Questions About Wire EDM
What is the smallest corner radius wire EDM can achieve?
Corner radius is set by wire diameter plus spark overburn. Finer wire and skim passes tighten corners but add time.
How thick can wire EDM cut?
Thicker plates are possible but cut time and wire deflection rise. Shops balance speed, accuracy, and plate stack height on the quote.
Does wire EDM require a start hole?
Yes when the path begins inside solid steel. Hole drilling EDM often creates the start hole before the wire threads through.
What wire diameter should I choose for mold inserts?
Finer wire suits tighter corners and small insert outlines. Coarser wire suits faster roughing on larger through profiles. The mold maker picks from common shop wire sizes.
Can wire EDM cut tapered features?
Yes. Taper or four axis wire paths cut upper and lower profiles that differ, within machine travel limits.
How does wire EDM compare to CNC milling for through holes?
Wire EDM cuts hardened through features with low cutting force but slower metal removal than milling on open soft steel.
Next step
Quote wire EDM scope on your tool
Upload CAD with through cut features such as insert profiles, ejector pin holes, and parting plates to confirm wire EDM scope and lead time for your program.