Views: 0 Author: Site Editor Publish Time: 2026-05-04 Origin: Site
A mold doesn't just "stop working" one day. In practice, mold failure falls into three categories:
Failure Type | What It Means | Typical Shot Count When It Happens |
|---|---|---|
Cosmetic wear | Part surface loses gloss, slight texture wear | Still functional for non‑cosmetic parts |
Dimensional failure | Part exceeds tolerance (usually due to wear of shut‑offs, pins, or core/cavity) | End of life for precision parts |
Catastrophic failure | Cracked cavity, broken core, seized ejector plate | End of life for any mold |
For this guide, "end of life" means dimensional failure or cracking — the point where part quality no longer meets spec without major repair.
Typical hardness: 28–32 HRC (pre‑hardened)
Best for: Low to medium volume, consumer goods, automotive interior non‑wear parts
Abrasive fillers? Not recommended
Application | Expected Shots (before dimensional wear) |
|---|---|
Non‑filled plastics (PP, ABS, PE) | 300,000 – 800,000 |
Mildly filled (<15% talc/glass) | 150,000 – 300,000 |
High cosmetic surface (textured) | May show wear earlier ~200,000 |
Real shop floor note: Many P20 molds run past 1 million shots on unfilled resins — but part dimensions drift. For tight‑tolerance parts, plan replacement at 500k.
Typical hardness: 46–52 HRC (heat treated)
Best for: High cavitation, high injection pressure, moderate glass fiber, hot runner manifolds
Abrasive fillers? Good for up to 30% glass
Application | Expected Shots |
|---|---|
Non‑filled or low fill (PP, ABS, PC) | 800,000 – 1,500,000 |
30% glass‑filled nylon or PBT | 300,000 – 600,000 |
High‑cavitation caps/closures | 2,000,000+ (with proper venting) |
Why H13 lasts longer than P20: Higher hardness resists abrasion and galling. It also withstands higher mold temperatures without softening.
Typical hardness: 48–52 HRC (heat treated)
Best for: Corrosive materials (PVC, POM, flame‑retardant grades), medical, optical
Abrasive fillers? Poor – stainless steels have lower abrasive wear resistance than tool steels
Application | Expected Shots |
|---|---|
Non‑filled, non‑abrasive, corrosive resin | 500,000 – 1,200,000 |
With glass fiber (any amount) | 150,000 – 300,000 (wear accelerates fast) |
Optical/lens molds (high polish) | 200,000 – 500,000 (scratch sensitivity) |
Important: S136 is chosen for corrosion resistance, not wear resistance. If you need both (glass + corrosive resin), consider D2 or coated H13.
Typical hardness: 58–62 HRC
Best for: High glass fiber (30–50%), high wear, long‑run unsupported shut‑offs
Abrasive fillers? Excellent – best among common mold steels
Application | Expected Shots |
|---|---|
30–50% glass‑filled engineering resins | 600,000 – 1,500,000 |
Unfilled resins | 1,500,000 – 3,000,000+ |
Tight shut‑offs (thin steel sections) | 500,000 – 1,000,000 |
Downside: D2 is more brittle than H13 and harder to machine. Not ideal for thin cores or sharp corners.
Typical hardness: 20–40 HRC (varies)
Best for: Core pins, areas requiring rapid cooling
Expected shots as a cavity steel: Not recommended – too soft.
Lifespan as cooling component: 100,000 – 500,000 before dimensional wear or galling
Used correctly: Copper alloys should be inset into a steel mold – not used as the primary cavity material.
Steel type sets the potential lifespan. These factors determine actual lifespan:
Every 10% of glass fiber or mineral filler roughly halves abrasive wear life.
Example – H13 mold:
Unfilled ABS → 1,200,000 shots
30% glass nylon → 350,000 shots
50% glass PPS → 120,000 shots
High pressure (over 1500 bar) and fast fill speeds erode gates, cores, and shut‑offs.
Effect: Can reduce mold life by 40–60% compared to conservative parameters.
PVC, POM, and some FR grades release acids during molding.
Effect: Pits the steel surface, accelerating wear. Stainless (S136) solves this but wears faster with fillers.
Dropped molds during handling
Overtightened clamp bolts (distorts plates)
Ejector pin seizure due to poor maintenance
Wrong melt temperature (burns steel surface)
Effect: Instant or rapid failure — unrelated to shot count.
Rust and scale inside cooling channels reduce heat transfer, causing localized hot spots.
Effect: Accelerated steel softening and cracking, especially in H13 and D2.
Adding a surface coating can double or triple mold life, especially with glass‑filled resins.
Coating | Best For | Typical Life Extension |
|---|---|---|
TiN (Titanium Nitride) | General wear, gate erosion | 2–3x |
CrN (Chromium Nitride) | Corrosive resins + mild wear | 2–4x |
AlTiN / AlCrN | High glass fiber, high temperature | 3–5x |
DLC (Diamond‑Like Carbon) | Low friction, sticky resins (PA, TPU) | 2–3x |
Rule of thumb: If your mold is wearing out before half its expected steel life, consider coating before re‑building the mold.
Steel | Unfilled (PP, ABS) | 20–30% Glass | Corrosive (PVC, POM) | Best For |
|---|---|---|---|---|
P20 | 500k – 800k | 150k – 250k (not recommended) | 200k – 400k | Low cost, low volume |
H13 | 1.0M – 1.5M | 350k – 600k | 400k – 700k | High cavitation, moderate glass |
S136 | 700k – 1.2M | 150k – 300k | 700k – 1.2M | Corrosive resins, optical |
D2 | 1.5M – 2.5M+ | 800k – 1.5M | 200k – 400k | High glass, high wear |
Copper alloy | Not used as cavity | Not used as cavity | Not used as cavity | Heat transfer insets only |
All ranges assume proper maintenance, conservative process parameters, and no extreme mechanical damage.
Shot count vs. steel type | Part quality | Recommendation |
|---|---|---|
Below typical range | Acceptable | Continue, but inspect more frequently |
At typical range | Still acceptable | Plan refurbishment (polish, pins, shut‑offs) |
At typical range | Out of spec | Replace or major rebuild |
Beyond range + visible wear/cracks | Any | Retire or major steel replacement |
Most large molders refurbish P20 molds at 300k–400k shots (new ejector pins, polish cavities, adjust shut‑offs) and run them to 600k–800k. H13 and D2 molds often get 500k–1M shots between refurbishments.
Mold life is not a single number — it's a range determined by steel, application, and care.
Choose P20 for low‑cost, moderate volume (under 500k shots)
Choose H13 for high cavitation and mild glass (1M+ shots)
Choose S136 for corrosive resins (but avoid heavy glass)
Choose D2 for high glass fiber and wear (2M+ potential)
And remember: A well‑maintained H13 mold with a good coating can outlast a neglected D2 mold every time. Steel sets the ceiling. Maintenance determines how close you get to it.
If you'd like a printable PDF with expected shot counts by steel type, filler content, and maintenance level — just let me know. I can also provide a mold inspection checklist based on shot count intervals.
