As cut EDM on visible land
- Matte gray appearance from recast and pitting
- Flow marks may look worse on high gloss expectations
- Requires stoning, polish, or texture spec to match SPI targets
Glossary
What Is EDM? Injection Molding Explained
EDM is spark erosion machining used to cut hardened mold details cutters cannot reach easily.
Glossary
EDM erodes hardened steel with controlled sparks for ribs, pockets, and sharp details
It is a machining process, not a substitute for SPI gloss by itself.
Electrical discharge machining removes material by vaporizing tiny bits of steel with repeated sparks. Mold makers use it where cutters cannot reach or where steel is already hard.
EDM leaves a recast layer and texture that may need stoning or polish when cosmetics require gloss.
Wire EDM is a sibling process that uses a moving wire for through cuts and insert outlines.
Toolmaking
Spark erosion cuts what milling cannot
EDM details show up on ribs, pockets, and shutoffs.
- Recast layer may need polish when cosmetics demand gloss.
- Wire and sinker EDM solve different geometry problems.
- Tool photos help buyers understand why rib steel costs more.
Finish
EDM surface versus polished cavity land
Plan post EDM work when Class A faces depend on the same feature.
EDM plus planned polish or texture
- Geometry preserved with controlled final finish steps
- Deep ribs achievable without weakening steel with only thin cutters
- Schedule includes EDM time plus finish labor explicitly
Go deeper
Where this term connects
Each link is a different angle on the same program, not a duplicate definition.
Wire EDM
Through cuts and insert outlines with a wire electrode.
Wire EDMSPI A1 finish
Gloss targets after steel geometry is cut.
SPI A1 finishEDM finish spoke
RFQ notes for EDM texture on production parts.
EDM finish spokeCore
Deep ribs often cut on the core half.
CoreVisual reference
Photos from molding and tooling programs
Images are selected from the NetProto Forge media library for this topic.
CNC and EDM area in a mold shop
CNC and EDM area in a mold shop
Precision mold steel component
Precision mold steel component
Close detail on molded rib geometry
Close detail on molded rib geometry
FAQ
EDM questions
Is EDM slower than milling?
Often yes on small deep features, but it can be the only safe path on hardened details.
Does EDM weaken the steel?
Recast must be managed on high stress features. Mold makers stone critical shutoffs when needed.
Can EDM replace draft on deep ribs?
No. Draft and polish still control ejection after EDM cuts the geometry.
Next step
Connect process to finish spec
Upload CAD with cosmetic faces and rib depth marked for DFM review.