When to Specify TiCN Coating on Core Pins: ROI, Limitations & Best Practices
Key Takeaway: TiCN coating is cost-effective only when processing abrasive resins (glass-filled, mineral-filled) at volumes exceeding 200,000 shots. For non-abrasive resins, coating adds cost without meaningful life extension. For corrosive resins, TiCN does not replace STAVAX ESR.
What TiCN Coating Does
TiCN (Titanium Carbo-Nitride) is a PVD hard coating applied at 3–5 μm thickness on the core pin surface. Its properties:
- Hardness: HV 3000+ (vs HRC 60–62 / ~HV 750 for uncoated SKH51)
- Friction coefficient: 0.2–0.3 (vs 0.4–0.6 for uncoated steel against plastics)
- Temperature limit: ~400°C (compatible with most injection molding temperatures)
- Thickness: 3–5 μm (does not affect shaft tolerance)
ROI Analysis: When Coating Pays Off
| Resin Type | Uncoated Life (shots) | TiCN Life (shots) | Life Extension | ROI Verdict |
|---|---|---|---|---|
| PA6-GF30 (glass-filled nylon) | 200K–300K | 600K–1.5M | 3–5× | ✅ Excellent — coating cost recovered in 1–2 replacement cycles saved |
| PBT-GF20 (glass-filled PBT) | 300K–500K | 800K–1.5M | 2.5–3× | ✅ Good — pays back at volumes > 500K |
| ABS (unfilled) | 800K–1.2M | 1M–1.5M | 1.2–1.3× | ❌ Marginal — coating cost not justified |
| PP/PE (commodity) | 1M+ | 1.2M+ | ~1.2× | ❌ Not justified — wear is minimal |
| PVC (corrosive) | 100K–200K (corrosion) | 120K–250K | ~1.2× | ❌ Wrong solution — use STAVAX ESR |
When NOT to Use TiCN
- Corrosive resins — TiCN does not provide corrosion protection. Acidic off-gases from PVC, POM, and FR compounds penetrate through micro-pores in the coating. Use STAVAX ESR instead.
- Non-abrasive resins at low volume — If pin life already exceeds your total production run, coating adds cost without benefit.
- Very thin pins (< ø1.5 mm) — The PVD coating process subjects pins to 400–500°C. Very thin pins may distort slightly. Verify straightness after coating.
- Pins requiring re-grinding — TiCN must be stripped and reapplied if the pin is re-ground to restore tip geometry. This doubles the reconditioning cost.
Cost-Benefit Calculation
Example: 8-cavity mold, PA6-GF30 resin, ø3 mm core pins
- Uncoated SKH51 pin cost: $15/piece × 8 = $120
- TiCN-coated pin cost: $25/piece × 8 = $200 (coating adds ~$10/piece)
- Uncoated life: 250K shots → 4 replacements per 1M shots = 4 × $120 = $480
- TiCN life: 1M shots → 1 set per 1M shots = $200
- Net savings per 1M shots: $280 (58% reduction)
According to ScienceDirect's PVD coating reference, TiCN coatings deposited below 500°C by cathodic arc evaporation achieve optimal adhesion on HSS substrates like SKH51.
Specification Checklist for TiCN Orders
- Substrate material: SKH51 (best adhesion), SKD61 (acceptable)
- Pre-coating finish: Ground to Ra ≤ 0.8 μm before coating
- Coating area: Full shaft or tip-only (tip-only is standard for core pins)
- Target thickness: 3–5 μm (specify "per side")
- Post-coating inspection: Verify shaft diameter remains within tolerance
Frequently Asked Questions
How much longer do TiCN-coated core pins last?+
2–5× longer on abrasive resins (glass-filled, mineral-filled). On non-abrasive commodity resins, improvement is only 1.2–1.5×, making coating uneconomical at low volumes.
Does TiCN coating add corrosion resistance?+
No. TiCN is a wear coating, not a corrosion barrier. For corrosive resins (PVC, POM, FR compounds), use STAVAX ESR core pins instead.
What is the typical TiCN coating thickness on core pins?+
3–5 μm. This thin layer does not change shaft diameter measurably (within h7 tolerance). Applied by PVD at below 500°C, it doesn't affect substrate hardness.
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