Technical Reference
EDM Micro Cracks Guide Technical Reference
Microcrack acceptance must be tied to material, surface function, discharge history, inspection resolution, and sampling location. Microcracks can remain below a smooth surface and propagate under fatigue, thermal cycling, or corrosion.
Quick Answer
Microcrack acceptance must be tied to material, surface function, discharge history, inspection resolution, and sampling location.
Key Surface Points
What the Surface Requirement Means
A vague “no micro cracks” note without method or magnification cannot be released or verified consistently. The consequence changes fit, function, or service performance for the Micro Cracks decision; it is not only a change in surface appearance.
How to Control It
Define whether the requirement is “none detected” at a stated method, a maximum length/depth, or removal of the affected layer on selected faces. When planning Micro Cracks, apply the requirement only to the dimensions and faces that control fit, function, service life, or documented release.
What Gets Missed
Microcracks can remain below a smooth surface and propagate under fatigue, thermal cycling, or corrosion. Releasing the part from Ra alone misses the defect; use metallography, penetrant, or another agreed method where service risk requires it.
Technical Context
Microcracks form when the heated surface contracts rapidly and tensile stress exceeds the local material resistance. They usually start in or near the recast layer and are more likely on brittle materials, hardened edges, and aggressive roughing conditions. Crack acceptance therefore requires an inspection method, not only an Ra value. This mechanism explains the limits and behavior that matter when planning Micro Cracks.
EDM Micro Cracks Guide Reference
| What you're asking | What you can expect |
|---|---|
| Acceptance item | Define separately |
| Roughness | Ra and measurement method |
| Recast/white layer | limit or removal on named face |
| Microcracks | method, magnification, and acceptance |
| Edge | radius, break, chipping, or rollover |
| Post-process | polish, lap, grind, stress relief, or passivation |
Inspection and Post-Process
Crack acceptance needs a named inspection method and service context. Fatigue, pressure, corrosion, and brittle materials justify stricter review than a cosmetic or nonfunctional surface. Do not use Ra as a substitute for crack inspection. For Micro Cracks, tie the accepted condition to the feature and inspection method named in the drawing.
Micro Cracks Drawing and Release Checkpoints
- Identify the controlled feature, material condition, access direction, and functional datum for this Micro Cracks decision.
- Separate dimensional requirements from texture, edge, recast, corrosion, fatigue, or post-process acceptance.
- State the inspection method, sampling or first-article requirement, drawing revision, quantity, and any documentation needed for release.
Limits and Better Alternatives
Main Limit
For EDM Micro Cracks Guide, one Ra value cannot approve recast, micro-cracks, edge damage, corrosion response, fatigue risk, or post-processing. When that boundary dominates, use lower-energy finishing, selective polishing/lapping/grinding, or a process redesign where the functional surface cannot accept the EDM-affected condition.
Consider Another Route When
Use lower-energy finishing, selective polishing/lapping/grinding, or a process redesign where the functional surface cannot accept the EDM-affected condition.
Practical Next Step
Crack acceptance needs a named inspection method and service context. Define whether the requirement is “none detected” at a stated method, a maximum length/depth, or removal of the affected layer on selected faces.
What to Remember
Microcrack acceptance must be tied to material, surface function, discharge history, inspection resolution, and sampling location. A surface is accepted by the failure mode it must prevent, not by one roughness value applied to the whole part.
Technical Reference
Use the values as planning references and define the functional requirement on the controlled drawing.
Use This Guide to Prepare Your RFQ
Contact us when your drawing and requirements are ready for review.
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- Thickness / part size
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Frequently Asked Questions
Is Ra enough to approve the surface?
No. Roughness and metallurgical/edge condition are separate.
Which faces need detailed control?
Fatigue, seal, wear, corrosion, contact, cutting, and medical surfaces.
Can finishing reduce the affected layer?
Yes, but the pass or removal method and inspection must be defined.
Should every surface use the same requirement?
No. Restrict detailed acceptance to functional faces.