Process & Material
Invar 36 Micro EDM Feasibility Review
Invar 36 can be machined with Micro EDM when the geometry matches micro holes, micro slots, miniature cavities, fine pins, and sub-millimeter precision details. Invar 36 is a low-expansion iron-nickel alloy selected for dimensional stability across temperature changes; the supplied condition affects support, discharge energy, finishing, and inspection.
Quick Answer
Micro EDM is suitable for Invar 36 when the feature is a micro hole, micro slot, miniature cavity, fine pin, or other sub-millimeter detail. The supplied condition must be stated before tolerance and surface requirements are confirmed.
Key Material Decisions
How This Material Behaves
A low-expansion iron-nickel alloy selected for dimensional stability across temperature changes. In Micro EDM, the supplied condition directly changes discharge stability, electrode wear, edge quality, and the finishing plan—especially at micro scale.
Choosing the Right Condition
Choose Micro EDM for micro holes, micro slots, miniature cavities, fine pins, and sub-millimeter precision details. State the exact Invar 36 condition, then set tolerance, finish, support, and inspection from the controlled feature rather than the whole part.
Risks to Manage
For Micro EDM, residual stress and asymmetric stock removal can undermine the low-expansion design intent. Electrode wear, debris and spark-gap variation can move size and pitch together during the final sizing of a sub-millimeter slot, hole or datum feature, especially around temperature-sensitive datums and low-expansion geometry. The practical failure in Invar 36 is apparent feature error produced by temperature drift, electrode wear and limited measurement resolution. For Invar 36, stabilize workpiece and inspection temperature, finish from controlled datums, and measure only after the part has thermally settled. Verify size, pitch, edge continuity and surface condition under the same inspection plan; document stabilized geometry, datum relationship and inspection temperature for Invar 36.
How Micro EDM Works on Invar 36
Micro EDM uses a very small electrode and low discharge energy to machine miniature features in Invar 36. Electrode wear, spark-gap stability, micro-flushing, temperature control and measurement resolution consume a significant share of the available tolerance. The local feature size and aspect ratio—not the overall workpiece size—must define the route.
Micro EDM Capability Reference
| What you're asking | What you can expect |
|---|---|
| Feature types | micro holes, micro slots, miniature cavities, fine pins, and sub-millimeter precision details |
| Tolerance | ±0.002–0.010 mm |
| Surface finish | Ra 0.1–1.6 μm |
| Feature scale | Sub-millimeter holes, slots, and cavities |
| Primary micro limit | Electrode wear and measurement resolution |
| Main limitation | Loose-tolerance or easily accessible features are rarely economical with Micro EDM. |
Material Condition Reference
| Condition | What to expect | Watch out for | Surface notes |
|---|---|---|---|
| solution annealed | Use stable support and conservative energy. | High-temperature alloys can retain a hard recast layer. | Identify fatigue and hot-section faces before finishing. |
| cold-worked or stabilized | Account for cold-work and service stress. | Thin features can move and electrode wear can grow corners. | Use low-energy finishing and selective metallurgical inspection. |
How This Material Behaves
Invar 36 is a low-expansion iron-nickel alloy whose value depends on dimensional stability. In EDM, this means residual stress release and uneven thermal history can move precision features even when cutting force is absent. Rough symmetrically, allow the part and dielectric to reach thermal equilibrium before final passes, and inspect at the specified temperature and datum condition. For Micro EDM, residual stress and asymmetric stock removal can undermine the low-expansion design intent. At micro scale, phase condition, recast and tool wear can be comparable with the remaining dimensional and surface-integrity allowance.
Surface Integrity and Post-Process
For Micro EDM on Invar 36, use lower-energy finishing and inspect critical surfaces when fatigue, sealing or corrosion performance is specified. Use low-energy finishing and account for electrode replacement or calibration before final sizing. Specify edge, recast and post-process requirements only on functional microfeatures, and use metrology that can distinguish true size from edge rounding and surface residue.
Invar 36 Micro EDM Checkpoints
- Confirm that the feature matches micro holes, micro slots, miniature cavities, fine pins, and sub-millimeter precision details.
- State the supplied condition: solution annealed and cold-worked or stabilized.
- Mark the controlled dimensions, functional surfaces, datum scheme, and inspection method.
Typical Parts and Features
- turbine and energy features
- corrosion-resistant inserts
- precision seals
- micro holes
- micro slots
- miniature cavities
Limits and Better Alternatives
Main Limit
Loose-tolerance or easily accessible features are rarely economical with Micro EDM. On Invar 36, residual stress and asymmetric stock removal can undermine the low-expansion design intent; the supplied condition still controls support, finishing, and surface-integrity review.
Consider Another Route When
Use conventional EDM for larger features, precision laser processing for suitable thin geometry, or mechanical micro-drilling where a tool can reach.
Practical Next Step
Send the Invar 36 drawing with condition, controlled geometry, tolerance, functional surface callouts, quantity, and inspection requirements. If the route is unclear, we will compare Micro EDM with the adjacent EDM or conventional process.
Practical Takeaway
Invar 36 is compatible with Micro EDM when the feature matches the process access. The supplied condition determines support, finishing, surface control, and inspection.
Additional Project Information
Include application, destination and end-use notes together with the material, quantity and drawing requirements.
Project Details for Technical Review
Include application and end-use notes when they affect material, inspection, documentation, or export review.
- Process: Micro EDM
- Material: Invar 36
- 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
Can Invar 36 be machined with Micro EDM?
Yes, when the feature is a micro hole, micro slot, miniature cavity, fine pin, or other sub-millimeter detail. Invar 36 is electrically conductive and the final route follows the feature geometry and supplied condition.
What controls Micro EDM on Invar 36?
The main process controls are electrode wear, feature-to-electrode ratio, micro-flushing, aspect ratio, edge radius, thermal stability, and measurement resolution. The Invar 36 condition adds dimensional-stability and surface-integrity requirements.
What is the main risk?
For Micro EDM, residual stress and asymmetric stock removal can undermine the low-expansion design intent. Electrode wear, debris and spark-gap variation can move size and pitch together during the final sizing of a sub-millimeter slot, hole or datum feature, especially around temperature-sensitive datums and low-expansion geometry. The practical failure in Invar 36 is apparent feature error produced by temperature drift, electrode wear and limited measurement resolution. For Invar 36, stabilize workpiece and inspection temperature, finish from controlled datums, and measure only after the part has thermally settled. Verify size, pitch, edge continuity and surface condition under the same inspection plan; document stabilized geometry, datum relationship and inspection temperature for Invar 36.
What should I send for review?
Send the drawing, exact Invar 36 condition, controlled geometry, tolerance, functional surface requirements, quantity, and inspection expectations. If any item is undecided, send what you have and we will help complete the review.