EDM Service
Sinker EDM Machining
Sinker EDM uses a shaped electrode to reproduce a blind cavity or internal form in conductive material. It creates shaped blind geometry in hardened material without tool deflection, including mold cavities, ribs, texture details, and internal forms.
Quick Answer
Choose Sinker EDM when the feature is blind, the electrode can approach from one side, and a shaped form must be controlled in depth. Electrode access and debris evacuation limit deep, narrow blind geometry.
Key Process Decisions
When to Choose This Process
Typical planning tolerance is ±0.008–0.030 mm, with Ra 0.2–6.3 μm as the broad finish context.
What to Watch For
Deep narrow ribs and poorly vented cavities increase electrode wear, debris trapping, corner growth, and floor inconsistency. We manage this by checking access, support, discharge conditions, and inspection before release.
How the Process Works
A shaped electrode—typically graphite for roughing and copper or copper-tungsten for finishing—is sunk into the workpiece through dielectric oil. Graphite tolerates high roughing current without melting, while copper wears more predictably at low energy and produces a finer surface. The electrode moves in an orbital path so wear is distributed and the cavity walls are finished evenly rather than burned straight down. Separate roughing and finishing electrodes are standard: the first removes bulk material, and the second produces final size and texture with a tighter orbit and lower energy.
Sinker EDM Capability Reference
| What you're asking | What you can expect |
|---|---|
| Feature types | blind cavities, ribs, shaped pockets, mold details, deep forms, and internal geometry that a traveling wire cannot reach |
| Tolerance | ±0.008–0.030 mm |
| Surface finish | Ra 0.2–6.3 μm |
| Electrode choice | Graphite or copper selected from cavity, finish, and wear needs |
| Primary cavity limit | Depth, rib width, access, and debris evacuation |
| Main limitation | Electrode access and debris evacuation limit deep, narrow blind geometry. |
Surface Control
Roughing and finishing are normally separated. Lower-energy finishing electrodes improve texture and reduce recast on selected cavity walls and functional faces.
Sinker EDM Drawing Checkpoints
- Choose Sinker EDM when the feature is blind, the electrode can approach from one side, and a shaped form must be controlled in depth.
- State the material grade, condition, controlled dimensions, and the functional surfaces that need Ra 0.2–6.3 μm.
- Use the same datum scheme for machining and inspection, and identify any report or sample-approval requirement.
Typical Parts and Features
- mold cavities
- blind pockets
- deep ribs
- shaped inserts
- texture and logo details
- internal key forms
Limits and Better Alternatives
Consider Another Route When
Use Wire EDM for through profiles, CNC for open cavities with tool access, or grinding for simple flat precision surfaces.
Practical Next Step
For a Sinker EDM quote, send the drawing, material grade and condition, critical dimensions, surface requirements, quantity, and inspection expectations. If the process route is unclear, send what you have and we will map each feature to the appropriate EDM method.
Practical Takeaway
Sinker EDM is the route to review when a part has a blind cavity, rib, or internal form that a traveling wire cannot reach.
Request a Machining Feasibility Review
Send material grade, drawing files, tolerance and quantity. We confirm process fit before quoting.
- Drawing or part sketch
- Material grade
- Thickness / part size
- Quantity
- Tolerance and critical dimensions
- Surface finish or inspection requirement
STEP/STP, DXF, DWG, PDF, IGS/IGES or ZIP.
Confidential drawing review. NDA support available on request.
Frequently Asked Questions
When should I choose Sinker EDM?
Choose Sinker EDM when the feature is blind, the electrode can approach from one side, and a shaped form must be controlled in depth. It creates shaped blind geometry in hardened material without tool deflection, including mold cavities, ribs, texture details, and internal forms.
What usually limits Sinker EDM?
Electrode access and debris evacuation limit deep, narrow blind geometry. Deep narrow ribs and poorly vented cavities increase electrode wear, debris trapping, corner growth, and floor inconsistency.
What tolerance and finish can I plan for?
Use ±0.008–0.030 mm and Ra 0.2–6.3 μm as planning ranges. Geometry, material condition, finishing passes, and inspection determine the released result.
What should I send for review?
Send the drawing, material and condition, functional dimensions, surface callouts, quantity, and inspection requirements. If some items are unknown, send the available files and we will help define the missing points.