Rehman 
The short answer
A well-built injection mould lasts anywhere from 50,000 to over 1,000,000 shots, depending on the steel grade, part complexity, material being moulded, and how well the mould is maintained. In Pakistani manufacturing, most production moulds are built for 200,000–500,000 shots — enough for years of steady production for the typical contract buyer.
The mould doesn't suddenly stop working at shot 500,001. It degrades gradually — dimensions drift, surfaces wear, vents clog. Knowing the signs and maintaining the tool on schedule is what separates a mould that lasts 5 years from one that's scrap in 18 months.
Mould life by steel grade
The single biggest factor in mould life is the steel used for the cavity and core inserts. Here's what each grade gets you:
Aluminium (soft moulds)
Shot life: 500–10,000. Used for prototyping, market testing, and very short runs. Cheap and fast to machine (2–3 weeks vs 4–8 for steel). Not meant for production — the cavity wears quickly, especially with glass-filled or abrasive resins. A smart choice when you're not yet sure the product will sell.
P20 (pre-hardened steel)
Shot life: 200,000–500,000. The workhorse of Pakistani injection moulding. P20 is pre-hardened to 28–34 HRC, easy to machine, polishable to a decent surface finish, and tough enough for most commodity plastics (PP, PE, ABS, PS). The majority of moulds built in Gujranwala use P20. Good balance of cost, machinability and durability.
H13 (hot-work tool steel)
Shot life: 500,000–1,000,000+. Hardened to 48–52 HRC after heat treatment. Used when running abrasive materials (glass-filled nylon, mineral-filled PP), high-temperature resins (PC, POM), or when the mould needs to survive a million+ cycles. Costs 30–50% more than P20 and takes longer to machine. Worth it for high-volume production tools.
S136 / NAK80 (mirror-finish and corrosion-resistant grades)
Shot life: 500,000–1,000,000+. Specialty steels for optical-grade parts (lenses, transparent covers), PVC moulding (which releases corrosive gas), or medical/food-contact parts that need mirror-polished cavities. Premium price — only justified when the application demands it.
The Pakistani market reality
Most contract buyers in Pakistan don't specify steel grade — they trust the moulder to pick appropriately. A responsible moulder will recommend P20 for standard work and flag when H13 or better is needed. If your moulder can't tell you what steel your mould is made from, that's a red flag.
What shortens mould life
Abrasive materials. Glass-filled nylon, mineral-filled PP, and recycled resin with contaminants grind down cavity surfaces faster. A P20 mould running 30% glass-filled PA will wear 3–5× faster than the same mould running virgin PP.
High injection pressure. Parts with thin walls or long flow paths need high pressure to fill. This stresses the mould steel, parting surfaces, and slides. Over time, flash appears where it didn't before — the steel is fatiguing.
Corrosive resins. PVC and some flame-retardant grades release chlorine or bromine gases that attack non-resistant steels. Run PVC in a P20 mould and you'll see pitting and surface corrosion within 50,000 shots. Use S136 or stainless inserts.
Poor cooling design. Uneven cooling causes thermal cycling stress — the mould heats and cools unevenly every cycle, warping cavity surfaces over time. Moulds with properly designed cooling channels last significantly longer.
Skipping maintenance. The #1 killer. A mould that never gets cleaned, lubricated or inspected will fail long before its steel-grade life expectancy. Most premature mould deaths in Pakistan are maintenance failures, not steel failures.
Mould maintenance — what a good schedule looks like
Every production run (operator-level)
Clean the parting surfaces and vents. Remove any residual flash or material. Check ejector pins for bending or sticking. Spray a light coat of rust preventive if the mould will sit idle for more than a day. This takes 15–30 minutes and prevents 80% of mould problems.
Every 10,000–25,000 shots (preventive maintenance)
Full disassembly, cleaning, and inspection. Check cavity dimensions against the original drawing. Polish any surface scratches or wear marks. Replace worn ejector pins, springs, and O-rings. Clean and flush cooling channels (scale buildup restricts flow and causes hot spots). Lubricate slides and lifters. Log the shot count and any observations.
Every 100,000+ shots (major service)
Dimensional inspection of all critical cavity and core surfaces. Re-polish or re-texture as needed. Check for cracks at stress concentration points (gate area, thin sections, sharp corners). Replace any insert showing measurable wear. Re-qualify with a trial shot and compare parts to the original approval sample.
The reality in Pakistan
Many Pakistani moulders skip preventive maintenance until something breaks. The mould runs fine for 100,000 shots, then suddenly produces parts with flash, short shots, or dimensional drift — and the fix is an emergency repair that costs more than three preventive services would have. If your moulder doesn't have a shot counter or maintenance log, ask why.
Signs your mould needs attention
Flash appearing where it didn't before. The parting line is wearing — surfaces that once sealed tight now have a gap. Can often be fixed by welding and re-machining the parting surface.
Parts sticking or ejecting unevenly. Worn ejector pins, damaged slides, or surface buildup. Usually a maintenance issue, not a rebuild.
Dimensional drift. Parts are within spec on the first run but creeping out of tolerance over time. The cavity is wearing — measure it. If wear is localised (gate area, high-flow zones), insert replacement fixes it. If it's general, the mould is approaching end of life.
Surface defects on parts. Scratches, pitting, or dull patches on what should be a smooth surface. The cavity needs re-polishing or, if corrosion has set in, insert replacement.
Longer cycle times. If you're running the same settings but cycle time has increased, cooling channels may be scaled up, or the mould isn't seating properly. Service and descale before assuming the mould is done.
Water leaks. Cracked cooling channels or failed O-rings. Fix immediately — water in the cavity causes rust, pitting, and part defects.
Repair vs refurbish vs retool — which one and when
Repair (PKR 10,000–50,000): fixes a specific problem — replace an ejector pin, weld a parting-line wear spot, re-polish a cavity surface. The mould is fundamentally sound, just needs a specific fix. This is routine and should be done in-house by the moulder.
Refurbish (PKR 50,000–200,000): a major overhaul of a mould that's worn but structurally intact. New inserts for worn cavities, re-machined parting surfaces, new cooling lines, all-new ejection components. Extends the mould's life by 50–100% of its original capacity. Worth it when the mould cost was high and the part design isn't changing.
Retool (full new mould cost): build a completely new mould. Necessary when the old mould is beyond economic repair, the part design has changed significantly, or you need to move to higher cavitation for increased volume. The old mould can sometimes be kept as a backup for emergency runs.
The decision rule
If the repair/refurbishment cost exceeds 40–50% of a new mould's price, retool. You get a fresh tool with full life expectancy, and you can incorporate any design improvements learned from running the old one.
How in-house tooling extends mould life
Moulders with their own tool room (milling, lathe, grinding, EDM) can maintain and repair moulds faster and cheaper than those who subcontract tool work. A worn ejector pin that takes 2 days to fix in-house takes 2 weeks when sent to an outside tool-maker — and costs 3× as much.
More importantly, in-house tooling means the moulder can catch problems early. When the press operator notices parts sticking, the tool-room technician can inspect the mould the same day, fix it, and have production running again by morning. Outsourced tool repair means production stops for a week.
This is one of the most underrated factors when choosing a moulder in Pakistan. Ask whether they have an in-house tool room. If yes, ask to see it. If no, ask who does their mould repairs and how long they typically take.
Bottom line
A well-built injection mould is a long-term asset, not a consumable. With the right steel grade for your application and a disciplined maintenance schedule, a production mould in Pakistan should last 200,000–500,000+ shots — that's years of production for most contract buyers.
The key questions to ask your moulder: what steel grade are you using and why? Do you track shot counts? What does your maintenance schedule look like? Can I see the mould after 100,000 shots? The answers tell you whether your tooling investment is being protected or neglected.
At Rehman Industry, we build and maintain moulds in-house — milling, lathe, grinding, hand finishing, all under one roof. We track shot counts, run preventive maintenance on schedule, and advise on steel-grade selection before you commit to tooling. Send us your part details and we'll recommend the right mould for your volume and budget.
What we do at Rehman Industry
Need a quote for your part?
Send us your drawing, sample or just a description. We'll reply within a business day with real numbers.
