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How long does an injection mould last?

An injection mould can last from 500 shots or fewer to more than a million, depending mainly on the SPI class it was built to, the metal it is made from and how it is run and maintained.

Tool life is quoted in shots or cycles: one cycle is one opening and closing of the mould, which may make one part or several, depending on the number of cavities. So a 100,000-cycle tool with four cavities can make up to 400,000 parts.

SPI mould classes

The mould classes published by the SPI (now the Plastics Industry Association) are the common shorthand on quotes. Secondary sources agree on the tiers but not on every number, so both columns are shown.

The classes also set how the tool is built. Crescent Industries describes Class 101 as needing a mould base of at least 280 BHN, moulding surfaces of at least 48 HRC, and features such as slide wear plates, corrosion-resistant cooling channels and parting line locks. For Class 103, Crescent gives a mould base of at least 165 BHN with cores and cavities of at least 280 BHN, and other features optional. Boyd notes that Class 104 tools may use mild steel or aluminium, and Class 105 tools may be soft aluminium, epoxy or cast materials.

Published shot counts by material

The aluminium figures disagree by a factor of thirty or more. Part of that is real (alloy, part geometry, resin and press settings all matter) and part is that some figures come from suppliers selling aluminium tooling as a service. Protolabs, for example, says some aluminium applications exceed 100,000 parts. Plan on the conservative end unless the toolmaker will put a higher figure in writing for your resin and part.

What shortens mould life

Fictiv lists the main causes of early wear:

• Abrasive resins: glass-filled grades wear moulds faster. Crescent Industries describes Class 102 as a good fit for abrasive materials such as glass-filled resins.
• Corrosive resins: Fictiv names PVC and POM as grades that can wear aluminium moulds quickly.
• Thick walls: thick-walled parts usually need longer cycles, which adds wear.
• Over-pressurising the plastic or using excessive clamping force.
• Poor temperature control, poor alignment, overlocking and excessive ejector stroke.

Komaspec's steel table gives a feel for why harder steels last longer: P20 at about 28 to 34 HRC, NAK80 at about 37 to 43 HRC, S136 at about 45 to 52 HRC and H13 at about 45 to 55 HRC.

Maintenance

Fictiv's maintenance advice is practical rather than numeric: clean the tool periodically without harsh abrasive cleaners, lubricate ejector pins, slides and cores without overdoing it (excess lubricant attracts debris), schedule inspections even if it takes the tool out of service, and keep a record of what was done. Fictiv gives no fixed interval; it depends on volume, resin and operating conditions.

What to ask for in writing

1. The SPI class, or the expected tool life in cycles, for your named resin.
2. The steel or aluminium grade and hardness for cavities, cores and mould base.
3. The number of cavities, so you can convert cycles to parts.
4. The maintenance schedule and who pays for routine maintenance and repairs.
5. What happens when the tool reaches its rated life: refurbishment, replacement inserts or a new tool, and who pays.
6. Who owns the tool and where it is stored. Precision Expedited points out that a tool you own on paper but cannot retrieve is a supply risk.

A low tool price may simply mean a lower class. That is fine if the class matches your lifetime volume.

These are published planning figures. Confirm expected life for your part and resin with the toolmaker.

Questions buyers ask

Which class do I need for 50,000 parts a year?

Multiply by the years you expect to sell the product and divide by the cavity count to get cycles. If the total is under 100,000 cycles, a Class 104 tool may do; above that, look at 103 or higher. Abrasive resins point to a higher class: Crescent Industries describes Class 102 as a good fit for glass-filled grades.

Does a glass-filled resin really matter?

Yes. Fictiv and Protolabs both say glass-filled and other abrasive plastics wear moulds faster, especially aluminium. Tell the toolmaker the exact grade at quote stage so the steel is chosen for it.

Can a worn mould be repaired?

Often. Fictiv notes that repairs commonly weld along parting lines and gates, and that welding aluminium is harder than welding steel. Ask the toolmaker how wear parts such as gate inserts can be replaced.

Is the rated life a guarantee?

Not unless it is in the contract. Xometry notes that some moulders will guarantee a tooling life, which varies by company. Ask for the figure and the remedy in writing.

Sources

• Komaspec, Injection mold tooling: https://www.komaspec.com/about-us/blog/injection-mold-tooling/
• Precision Expedited, Injection molding companies: questions to ask: https://precisionexpedited.com/injection-molding-companies-questions-to-ask/
• Crescent Industries, The impact of injection mold classification on cost: https://www.crescentind.com/blog/the-impact-of-injection-mold-classification-on-cost
• Boyd, Classification of plastic injection molds: https://www.boydcorp.com/blog/classification-plastic-injection-molds.html
• Fictiv, What to know about injection molding tooling life: https://www.fictiv.com/articles/what-to-know-about-injection-molding-tooling-life
• Fictiv, Steel vs. aluminum for injection molds: https://www.fictiv.com/articles/steel-vs-aluminum-for-injection-molds
• MakerVerse, Injection molding FAQ: https://www.makerverse.com/resources/injection-molding-faq/
• Protolabs, Aluminum vs. steel tooling: https://www.protolabs.com/resources/blog/aluminum-vs-steel-tooling/
• Protolabs, Soft vs. hard tooling: https://www.protolabs.com/resources/blog/soft-vs-hard-tooling/
• Xometry, Injection molding cost: https://www.xometry.com/resources/injection-molding/injection-molding-cost/