For small batch injection molding production (typically prototyping, validation runs, or annual volumes from a few thousand to tens of thousands of parts), the core principle in selecting mold steel is high cost-effectiveness, short machining lead time, and sufficient mold lifespan—no need to chase ultra-long durability.
Mainstream Options Comparison:
- P20 (pre-hardened steel, hardness 28-36 HRC): The most budget-friendly choice. Excellent machinability, no additional heat treatment required, minimal distortion, and fast delivery. Mold life around 100,000–300,000 shots, ideal for common non-corrosive, non-high-gloss materials like PP/ABS in small runs. Drawback: moderate mirror polishing and wear resistance. If budget is tight or part appearance is not demanding, P20 is the top pick for small batches.
- 718 / 718H (improved P20 with added Ni, hardness 30-40 HRC): Builds on P20 with better toughness, polishability, and wear resistance; mold life can reach 300,000–500,000 shots. Especially suitable for medium-complexity cavities, larger parts, or small-to-medium runs needing improved surface quality. Priced 20-40% higher than P20, but offers superior overall value—many factories regard it as the “small-batch upgrade version.”
- NAK80 (mirror-finish pre-hardened steel, hardness 37-43 HRC): Top-tier mirror polishing performance (up to #10,000 or better), excellent corrosion and wear resistance, perfect for high-gloss, transparent parts (e.g., PC, PMMA) or strict aesthetic requirements in small batches. Lifespan exceeds 400,000–500,000 shots, but it’s the most expensive (often 2-3x P20) and slightly slower to machine. If your product demands ultimate mirror finish or high-precision appearance, NAK80 is worth the investment; otherwise, it’s overkill for small runs.
Small-Batch Recommendation Order:
- Tight budget + general appearance → P20 (most cost- and time-efficient)
- Moderate requirements + better durability → 718/718H (the balanced king)
- High-gloss/transparent/premium appearance → NAK80 (mirror expert)
Don’t blindly opt for expensive steel in small batches—first evaluate your plastic material, surface finish needs, and expected shot volume! Professional mold makers recommend starting with a smart assessment for optimal results.