Medical Syringe Barrel: STAVAX ESR Core Pins for Cleanroom Compliance
Challenge
A medical device manufacturer needed to produce precision syringe barrels for a Class III injectable drug delivery system. The mold ran POM (Polyoxymethylene) resin, which releases formaldehyde gas during processing — a corrosive byproduct that attacks standard tool steels. Previous SKH51 core pins developed surface pitting after approximately 300K shots, causing visible defects on the syringe bore and risking particle contamination in a cleanroom environment.
Solution
Core pins were specified in STAVAX ESR (martensitic stainless steel) with tip lapping for the barrel bore surface. The mold was built with Straight Core Pins in STAVAX grade, processed to achieve a mirror polish (Ra < 0.1 μm) on the working tip.
Results
| Metric | Before | After | Improvement |
|---|---|---|---|
| Pin Replacement Interval | 300K shots | 2M+ shots | 6.6× longer service life |
| Corrosion Incidents | 3 per year | 0 over 24 months | 100% elimination |
| Bore Surface Quality | Degraded after 200K | Consistent to 2M+ | No visible change |
| Cleanroom Compliance | Risk of particle shedding | Full ISO 14644 Class 7 | Continuous compliance |
"The cost premium for STAVAX was roughly 40% per pin, but we saved that back many times over in eliminated downtime and zero particle contamination events. For medical, there is really no alternative."
— Quality Director, Medical Device OEM