Process & Material
AZ91 Magnesium Alloy Micro EDM Precision Tolerance + Skim Cut / Fine Pass Finish Review
This AZ91 Magnesium Alloy Micro EDM page combines a Precision tolerance target with a Skim-cut / fine pass finish surface target. These requirements must be planned together because finishing passes improve texture while also changing profile offset, cavity size, hole size, or edge geometry.
Quick Answer
For AZ91 Magnesium Alloy, ±0.010–0.020 mm and Ra 0.4–0.8 μm are achievable on selected Micro EDM features when electrode wear, gap stability, micro-flushing, thermal control, and measurement resolution are planned together. Apply both targets from the same datum, and reserve the tightest values for the dimensions and faces that control function.
Key Quality Decisions
What These Targets Mean
On AZ91 Magnesium Alloy, ±0.010–0.020 mm controls the named dimensions and Ra 0.4–0.8 μm controls the named functional faces. In Micro EDM, electrode wear and measurement resolution can consume the tolerance while low-energy finishing changes edge radius and texture. The supplied condition adds a separate risk: casting porosity, thin walls and surface reactivity can destabilize finish and edge quality.
Getting Both Targets Right
Use one machining and inspection datum. Apply ±0.010–0.020 mm only to dimensions that control fit, and Ra 0.4–0.8 μm only to functional faces. Plan electrode wear, feature-to-electrode ratio, micro-flushing, aspect ratio, edge radius, thermal stability, and measurement resolution. State the exact AZ91 Magnesium Alloy condition and the inspection method before releasing the result.
What Gets Missed
On a sub-millimeter hole, slot, or pitch feature specified at ±0.010–0.020 mm and Ra 0.4–0.8 μm, electrode wear and measurement uncertainty can consume the remaining tolerance while the edge rounds during finishing. The tolerance represents a feature-level precision fit, while successive low-energy passes change kerf, taper, and corner geometry while improving texture; treating them as independent callouts can make the last finishing step destroy the dimension it is meant to improve. Inspect size, pitch, depth, edge radius, electrode wear, and measurement uncertainty after the final surface step. For AZ91 Magnesium Alloy, also account for this material-specific risk: casting porosity, thin walls and surface reactivity can destabilize finish and edge quality.
How the Targets Interact
For AZ91 Magnesium Alloy, ±0.010–0.020 mm and Ra 0.4–0.8 μm are linked through the Micro EDM finishing route. Electrode wear and measurement resolution can consume the tolerance while low-energy finishing changes edge radius and texture. The release plan must bind material condition, geometry, datum, finishing stage, and measurement to the same named features.
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. |
Quality Target Reference
| Requirement | Planning range | What it means in practice |
|---|---|---|
| Precision tolerance | ±0.010–0.020 mm | Use stable datum control and a finishing strategy on the dimensions that govern fit. |
| Skim-cut / fine pass finish finish | Ra 0.4–0.8 μm | Use dedicated trim or finishing passes and inspect only the surfaces carrying this callout. |
Material Condition Reference
| Condition | What to expect | Watch out for | Surface notes |
|---|---|---|---|
| as-cast | Use stable support and economical roughing. | Clamping and material condition can move delicate features. | Apply fine finishing only to functional faces. |
| solution-treated | Balance dimensional stability with feature-specific finishing. | Residual stress can shift thin sections or small details. | Identify wear, seal, fatigue, or contact surfaces. |
| aged condition | Use conservative energy and selective inspection. | Finished or hardened surfaces can be sensitive to edge damage and recast. | Use lower-energy finishing or post-processing where function requires it. |
Tolerance & Surface Requirements
For Micro EDM at ±0.010–0.020 mm and Ra 0.4–0.8 μm, apply the finish only to the faces named on the drawing. On AZ91 Magnesium Alloy, avoid unsupported absolute capability claims and define cleaning, residue and handling requirements before production. Roughness does not replace recast, edge, corrosion, crack, or post-process acceptance where those items affect function.
AZ91 Magnesium Alloy Micro EDM Quality Checkpoints
- Mark the dimensions that actually need ±0.010–0.020 mm and use the same datum for machining and inspection.
- Circle the faces that need Ra 0.4–0.8 μm; leave nonfunctional surfaces at a practical production finish.
- State the AZ91 Magnesium Alloy condition, Micro EDM finishing strategy, measurement method, and any recast or edge requirement.
Limits and Better Alternatives
Main Limit
±0.010–0.020 mm and Ra 0.4–0.8 μm are selected-feature planning references for AZ91 Magnesium Alloy in Micro EDM, not unconditional whole-part guarantees.
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 AZ91 Magnesium Alloy drawing with the Micro EDM features that need ±0.010–0.020 mm, the faces that need Ra 0.4–0.8 μm, the supplied condition, quantity, datums, and inspection method.
Practical Takeaway
On AZ91 Magnesium Alloy, plan ±0.010–0.020 mm and Ra 0.4–0.8 μm together for the selected Micro EDM features. Use one datum and one inspection plan, and apply the tightest values only where they control function.
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: AZ91 Magnesium Alloy
- 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.