How many shots is Mould Life rated for?

Answer: Size decides — 200,000 below 520 mm, 150,000 from 520 to 700 mm, 100,000 above 700 mm, counted while the cavity stays inside ±0.13 mm.

Must a tool be replaced at 100,000 shots?

Answer: No. With tolerance, flash and cycle inside limits, one nitride plus a lap buys 30,000 more shots. Two limits breached and repair costs more than the remaining depreciation.

At what flash thickness does production stop?

Answer: 0.25 mm. Above it each part costs six extra seconds, or 300 parts a shift.

Is harder steel always cheaper?

Answer: Above 48 HRC wear slows but corners chip. P20 at 30 HRC with one nitride at 40,000 often lands cheaper overall.

Calendar or counter for servicing?

Answer: The counter. A tool idle three months is not new, and grease dries in the slides.

Mould Life: Dimensional Drift After 100,000 Shots

Quick answer: Mould Life at 100,000 shots reads as three numbers: cavity length grown 0.09 mm, flash up from 0.05 to 0.18 mm, wall tolerance opened from ±0.06 to ±0.13 mm. Half of that drift lands in the first 40,000 shots.

Where Mould Life Shows Up as Dimensional Drift
Cavity Wear and Flash per 20,000 Shots
How Wall Tolerance Opens Up
Steel Grade and Service Intervals
Repair, Retirement and Depreciation
FAQ

1. Where Mould Life Shows Up as Dimensional Drift

A 520 mm × 380 mm × 96 mm tool in a 650 t press does not grow at a constant rate. Gauging five parts every 20,000 shots gives two slopes: 0.05 mm over the first 40,000, then 0.04 mm more to 100,000.

Three causes need separate logs: abrasion pushes the cavity outward, parting-line collapse grows flash, residual stress warps the base.

Shots	Cavity length (mm)	Wall tolerance (mm)	Flash (mm)
First part	520.02	±0.06	0.05
40,000	520.06	±0.08	0.09
70,000	520.09	±0.11	0.14
100,000	520.11	±0.13	0.18

Nine hundredths of a millimetre becomes a 0.2 mm step along the closing line. The groove is 6 mm wide for an 8 mm cord, a 25% squeeze when new; at 6.1 mm it falls to 22% and the immersion test weeps near shot 90,000.

2. Cavity Wear and Flash per 20,000 Shots

Wear is easier to plan in 20,000-shot blocks. A P20 cavity at 30 HRC loses 0.015 to 0.02 mm opposite the gate in each block; the same geometry in S136 at 48 HRC loses 0.006 mm.

Mould Life trial case in off-white, lid closed with a wavy seam along the front edge, thin-walled lid border, rounded corners, pale grey background

Flash follows a simpler rule. Every 0.02 mm the parting faces collapse doubles flash at unchanged clamp: 0.05 mm new, 0.09 mm at 40,000, 0.14 mm at 70,000, 0.18 mm at 100,000. Past 0.2 mm deburring loses 300 parts a shift.

Adding clamp buys time only. 650 t to 690 t presses flash back to 0.12 mm, but the tool carries 6% more load and guide clearance opens from 0.03 to 0.05 mm faster.

Vents fail quietly: 0.02 mm deep and 8 mm wide when new, closed to 0.008 mm by shot 60,000, leaving a 0.3 mm scorch mark that reads like a melt fault.

3. How Wall Tolerance Opens Up

The wall is nominal 2.8 mm, measured 2.79 to 2.83 mm when new, a ±0.06 mm band that opens one way: ±0.08 at 40,000, ±0.11 at 70,000, ±0.13 at 100,000. Beyond ±0.15 the latch preload no longer lands.

Loose walls show in three places. A 3.2 mm latch boss drops holding force from 180 N to 150 N after a 0.1 mm growth; a 6 mm hinge bore becomes 6.08 mm and the lid rocks at 90 degrees; a base rib root of R2 becomes R1.7 and a 1.2 m drop leaves a stress mark.

Splitting the band by feature buys shots. Hold assembly faces at ±0.08 mm, let cosmetic walls run to ±0.15 mm, and the tool reaches 130,000 shots instead of 100,000 for the cost of one gauge.

Warp is read on a surface plate: 0.15 mm at the corners when new, 0.35 mm at 100,000, and above 0.4 mm a five-high stack crushes the bottom case.

4. Steel Grade and Service Intervals

Steel is chosen per shot. A P20 tool at 30 HRC costs 380,000 CNY and needs three polishes to reach 100,000 shots; 718H at 34 HRC costs 460,000 CNY and needs two; S136 at 48 HRC costs 620,000 CNY, holds the cavity almost unchanged, and adds 30% machining hours.

Mould Life verification case in blue, front edge from above, semicircular handle notch in the lid skirt, two hinge blocks at the rear, white background

Steel	Hardness (HRC)	Tool price (10k CNY)	Polishes to 100,000 shots	Cost per part (CNY)
P20	30	38	3	1.9
718H	34	46	2	2.3
S136	48	62	0	3.1

Servicing runs on shots: grease ejector pins every 5,000, flush the water circuit with 5% citric acid every 15,000, polish a 0.005 mm deposit layer every 25,000, nitride at 60,000.

The first nitride matters more than repeats. One tool waited to shot 80,000 with the substrate at 26 HRC; its 50 HRC surface collapsed within 10,000 shots. Nitriding at 40,000 carried it to 140,000 inside 0.06 mm.

Tap water lays down 0.4 mm of scale in two years, lifting mould temperature from 45 °C to 58 °C and the cycle from 58 s to 66 s.

5. Repair, Retirement and Depreciation

Who pays for the tool decides how it is written down. If the moulder builds it and spreads cost into piece price, 380,000 CNY over 200,000 shots is 1.9 CNY per part. If the brand funds it and keeps title, it becomes a fixed asset amortised over five years with 8% residual.

Repair has a ceiling: three weld-and-lap passes at 0.04 mm. A fourth softens everything within 15 mm of the weld below 32 HRC; three passes restore 0.03 mm for under 30,000 shots.

Four triggers settle retirement: wall tolerance outside ±0.15 mm for three lots, flash steady above 0.25 mm, cycle 8% longer than new, three repairs in one spot. Two of the four and the tool comes out.

Trigger	Threshold	Check	Action
Wall tolerance	3 lots beyond ±0.15 mm	5 parts per lot	Repair or replace
Flash	Steady above 0.25 mm	Every 5,000 shots	Lap the parting line
Cycle time	8% longer than new	Weekly	Check water and vents
Repairs	3 in one location	Each repair	Retire the tool

Ownership needs three clauses: drawings and programs, where the tool sits, what happens at retirement. Without them a supplier change means a fresh 380,000 CNY build.

Conclusion

Mould Life is two slopes plus three service events. Four checks: cavity growth under 0.10 mm, wall tolerance inside ±0.13 mm, flash under 0.2 mm, fewer than three repairs in one spot. Meet all four and 100,000 shots is a midpoint, not an ending.