Mold Marking Methods Compared: Engraved Pins vs Inserts vs Laser vs EDM
Key Takeaway: Use engraved core pins when the marking location is at a core pin position (cheapest, most integrated). Use marking inserts for changeable date codes on mold surfaces. Use laser or EDM engraving only when permanent, high-resolution markings on hardened mold surfaces are required.
Four Methods at a Glance
| Method | Location | Changeable? | Cost | Durability | Resolution |
|---|---|---|---|---|---|
| Engraved core pin | At core pin position (internal feature) | Yes (swap pin) | $5–15/pin | Pin life (500K–1M+) | 1.5 mm min character |
| Marking insert | Any mold surface (pocket required) | Yes (swap insert) | $20–50/insert | Insert life | 1.0 mm min character |
| Laser engraving | Any mold surface | No (permanent) | $50–200/mark | Mold life | 0.3 mm min character |
| EDM texturing | Any mold surface | No (permanent) | $100–500/mark | Mold life | 0.5 mm min character |
Engraved Core Pins
The most cost-effective method when marking location coincides with a core pin position. The engraving (raised or recessed characters) is machined directly into the pin tip during manufacture.
- Best for: Cavity numbers, recycling codes (SPI symbols), fixed year codes
- Limitation: Mark appears only at the pin location (internal feature) — not suitable for external surface marking
- Character depth: 0.1–0.3 mm
- Minimum pin diameter: ø4 mm for single character
Marking Inserts
Small steel inserts pressed into pockets machined in the mold. Available as clock-face date wheels, year-month rotary inserts, or custom-character fixed inserts.
- Best for: Changeable date codes, regulatory compliance markings that update periodically
- Limitation: Requires a pocket machined in the mold surface — cannot be added to a finished mold without re-machining
Laser Engraving
Direct laser marking on hardened mold steel. Produces extremely fine detail (0.3 mm minimum character) and is permanent.
- Best for: Complex logos, QR codes, fine text on cavity surfaces
- Limitation: Permanent — cannot be changed without re-polishing and re-engraving. Higher cost per mark than pins or inserts.
EDM Texturing
Electrical discharge machining creates marks by eroding the mold surface with a shaped electrode. Produces deep, durable marks in hardened steel.
- Best for: Deep text or symbols on very hard mold steels (HRC 50+) where laser depth is insufficient
- Limitation: Most expensive method, permanent, requires electrode manufacture
Decision Guide
- Marking at a core pin location? → Engraved core pin (cheapest, integrated)
- Changeable date code on mold surface? → Marking insert / clock-face
- Fine detail or logo on mold surface? → Laser engraving
- Deep permanent mark on hardened steel? → EDM texturing
Frequently Asked Questions
Which mold marking method is most cost-effective?+
Engraved core pins at $5–15/pin when the marking location coincides with a core pin. Marking inserts at $20–50 for mold surface locations. Both are far cheaper than laser ($50–200) or EDM ($100–500).
Can I change date codes without modifying the mold?+
Yes — use clock-face inserts (rotate monthly), interchangeable marking inserts (swap out), or replaceable engraved core pins. Direct laser/EDM on the mold surface is permanent.
Which method lasts the longest in production?+
Direct EDM texturing lasts the mold's lifetime. Engraved core pins last until pin replacement (500K–1M+). Marking inserts are designed for periodic replacement.
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