Date Code & Cavity Marking Best Practices for Injection Molded Parts
Key Takeaway: Use engraved core pins for permanent cavity numbering and static date codes. For changeable date codes, use clock-face inserts or rotating date wheels in the mold. Always verify with your customer whether regulatory requirements (IATF 16949, FDA 21 CFR 820) mandate specific marking formats.
Date Code Formats
| Format | Example | Update Method | Best For |
|---|---|---|---|
| Clock-face (12-position) | Arrow pointing to month number | Rotate insert between runs | Most applications — no tool modification needed |
| Year-month digits | "26-07" (July 2026) | Replace engraved insert monthly | Where alphanumeric codes are preferred |
| ISO year-week | "2628" (Week 28, 2026) | Replace insert weekly | Automotive IATF 16949 requirements |
| Engraved fixed | "2026" (year only) | Replace core pin annually | Low-mix production with annual date changes |
Cavity Numbering Systems
Cavity identification marks are permanently engraved on the core pin tip and transfer to every molded part:
- Sequential numbers — "1", "2", "3"… Simple and universal. Each cavity gets a unique number. The number appears on a non-cosmetic surface of the part.
- Dot system — 1 dot = cavity 1, 2 dots = cavity 2, etc. Used when space is extremely limited (part surface < 3 mm²).
- Alphanumeric — "A1", "B2"… Used in large molds where row/column identification aids troubleshooting.
According to ISO 20457, cavity identification marks must be placed on a surface that does not affect part function or appearance, and the mark location must be documented in the mold specification.
Engraving Depth & Character Size
| Parameter | Recommended Range | Notes |
|---|---|---|
| Character height | 1.5–3.0 mm | Smaller than 1.5 mm becomes illegible after wear |
| Engraving depth | 0.1–0.3 mm | Deeper than 0.3 mm creates ejection issues |
| Character type | Raised (on mold) → Recessed (on part) | Most common; reverse requires discussion |
| Font | Block/sans-serif | Avoid serifs — fill poorly in thin engraving lines |
| Minimum pin diameter | ø4 mm for single digit | Smaller pins cannot accommodate readable characters |
Regulatory Requirements by Industry
- Automotive (IATF 16949) — Cavity identification mandatory for all production parts. Date code mandatory for safety-critical components. Format per customer specification (usually ISO year-week).
- Medical (FDA 21 CFR 820) — Lot traceability requires cavity identification. Date code or lot number must be traceable to specific production dates and material batches.
- Food contact (EU 1935/2004) — Traceability marking required for closures, containers, and utensils. Cavity numbers enable traceback from consumer to specific mold cavity.
- Consumer products — Recycling codes (SPI resin identification, e.g., ♻️1 for PET) are typically molded via engraved core pins or cavity inserts.
Frequently Asked Questions
What date code format is standard for injection molded parts?+
Clock-face (12-position dial) is most popular — update monthly by rotating the insert with no tool modification. Year-month digits and ISO year-week formats are also used, especially in automotive per IATF 16949.
When is cavity marking legally required?+
Mandatory for automotive (IATF 16949), medical devices (FDA 21 CFR 820), and food contact packaging (EU 1935/2004). Even when not legally required, cavity marking enables root-cause analysis for cavity-specific defects.
Should date codes be raised or recessed on the part?+
Raised text on the part is generally preferred — no stress concentrations and easier optical inspection. Verify with your quality team which orientation is required for your specific application.
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