Ejection Pin Marks in Die Casting: What They Are and How We Minimize Them

Ejection pins play a crucial role in the die-casting process—they push the part out of the mold once it solidifies. But where these pins contact the casting, they can leave visible marks or indentations.

For cosmetic parts, uncontrolled ejection marks are a red flag. That’s why proper ejection design is critical in balancing tool function with part aesthetics.

⚙️ What Are Ejector Pins?

Ejector pins are steel rods mounted in the ejector half of the die. After each shot, they push the cooled part off the core or cavity, allowing for clean release.

🔍 Where Issues Arise:

1. Deep or Soft Alloys (e.g. Zinc)

   Ejector pins can imprint into hot, soft metal if timing or placement is off.

2. Improper Ejector Layout

   Pins too close to edges or thin ribs may cause cracks or distortion.

3. No Relief or Surface Texture

   High-gloss or painted surfaces will show even shallow pin marks.

4. Non-Flush Retraction

   If pins don’t retract flush, they can leave burrs or high spots.

✅ How LVIO Minimizes Pin Marks:

• We work with tooling designers to position pins behind bosses or low-visibility areas

• Use pin polishing and precision seat depth to reduce witness marks

• Recommend post-cast surface treatment (e.g. shot blasting) to blend in marks for cosmetic parts

At LVIO Precision, we treat ejection planning as part of product design—not just tool mechanics. Whether it’s a B-side enclosure or a customer-facing surface, we ensure ejection features don’t become visual defects.