EDM Surface Defect Troubleshooting
Pitting, pinholes and patchy gloss are rarely “just cosmetic.” Use this decision path before another polishing cycle erases geometry or delays mold approval.
Diagnose the surfaceStart with the defect, not the machine brand
Pitting or pinholes
Check first: unstable spark gap, debris, flushing, filtration and abnormal/secondary discharges. Compare the suspect area against an approved physical reference—not a phone photo.
Uneven texture or gloss
Check first: electrode area, sidewall flushing, additive distribution, material batch and viewing light. A single Ra number can still miss optical non-uniformity.
Texture repeats poorly cavity-to-cavity
Check first: stored machine settings, electrode wear, loading verification, inspection location and the same reference plate at every station.
Part sticks or demolds badly
Check first: crater form, draw direction, draft, texture depth and plastic material. Surface structure can materially affect plastic adhesion and cycle behavior.
Five-minute shop-floor triage
Acceptance evidence to capture
- Workpiece and electrode material, electrode area and finishing program.
- Dielectric condition, filtration/flushing status and inspection location.
- Ra/Rz result where contractually required, plus crater appearance and direction.
- Approved A–F physical VDI/SPI reference plate under agreed lighting.
- Photos only as supporting records—not the master acceptance standard.
Technical basis: Makino describes secondary discharge control and debris/clean spark-gap effects; GF Machining Solutions notes that Ra alone may not describe optical appearance and that crater geometry can affect plastic adhesion. See Makino and GF Machining Solutions.