The fundamental IBM container design constraint is that the container body OD must be greater than or equal to the neck OD. This is dictated by the IBM process architecture: the preform must be able to pass through the neck ring of the blow mould when transferred on the core rod from the injection station to the blow station. If the container body OD were smaller than the neck OD, the blow mould cavity would need to close around a container body narrower than the neck — making it geometrically impossible to open and strip the blown container off the core rod without interference between the container body and the blow mould neck ring. In practice, IBM containers with body OD equal to neck OD (1.0x body BR) produce the tall narrow cylindrical serum vial and ampoule formats — IBM can achieve body OD = neck OD because the preform inflates uniformly at 1.0x BR (no radial expansion, only axial extension). Containers with body OD slightly larger than neck OD (1.05-1.20x body BR) produce the gently tapered or parallel-body Korean luxury cosmetic cylinder containers. The IBM preform design constraint (body OD ≥ neck OD) is therefore not a limitation for most Korean cosmetic container designs, which naturally have body OD larger than neck OD — it only becomes a constraint for hypothetical inverted-shoulder or waisted bottle designs where the body narrows below the shoulder before widening at the base.

Korea Ever-Power achieves ±2% cavity shot weight balance in 12-cavity IBM injection moulds through four techniques applied in combination during mould design, manufacture and qualification. Naturally balanced H-tree runner layout: the runner system is designed as a symmetric H-tree where every cavity is equidistant from the sprue in terms of runner path length and cross-section. This naturally balanced geometry ensures equal pressure drop from sprue to every cavity gate — producing equal fill rate and shot weight at each cavity without any runner diameter adjustment. Runner cross-section sizing: runner diameter is calculated to produce a residence time of 0.3-0.5 s in each runner branch at the injection rate used, ensuring the melt is at consistent temperature and viscosity at every gate. Under-sized runners shear-heat the melt, reducing viscosity and over-filling distal cavities. Cavity dimension verification: each of the 12 injection cavities is measured at 6 critical dimensions (cavity body diameter, cavity height, neck bore diameter, gate diameter, shoulder radius) by CMM before assembly, with all dimensions within ±0.01 mm of nominal. Dimensional variation within this range contributes less than ±0.5% to shot weight variation. Production trial balance verification: at pre-delivery production trial, Korea Ever-Power weighs all 12 cavities simultaneously (all shots collected and sorted by cavity identification mark) over 20 consecutive shots, calculates mean weight per cavity, and confirms all cavities are within ±2% of the 12-cavity mean. Cavities outside ±2% are corrected by gate diameter adjustment (slight enlarging of under-weight cavities) or runner diameter adjustment before final delivery.

Switching between HDPE and PP RCP IBM on the same injection mould and core rod set requires no preform design changes when the container is designed for PP RCP Korean cosmetic IBM (the more demanding material). The injection mould cavity dimensions for PP IBM and HDPE IBM are identical at the design stage because both materials are processed at similar injection pressures (80-120 MPa) and both materials have comparable linear shrinkage (HDPE 1.5-3.0%, PP RCP 1.2-2.0%) at the cavity dimensions used for Korean cosmetic containers. The slightly different shrinkage rates between HDPE and PP RCP produce a small dimensional difference in the finished container: a mould designed for PP RCP IBM at 2.0% shrinkage produces HDPE IBM containers at 2.5% shrinkage — approximately 0.1-0.3 mm smaller OD and height for HDPE versus PP RCP from the same mould. For Korean cosmetic container specifications where the container OD tolerance is ±0.5 mm or wider, this material-to-material dimensional variation is within specification. For Korean pharmaceutical containers with tighter OD tolerances (±0.05-0.10 mm), a separate mould calibrated for each specific material is required. Process changes when switching materials: barrel temperature (PP 210-245°C vs HDPE 195-220°C), mould temperature (PP cosmetic 55-70°C vs HDPE household 18-26°C or HDPE cosmetic 24-32°C), and injection hold pressure profile may all require adjustment, but the physical mould tooling remains unchanged.

Korea Ever-Power IBM injection mould tooling life depends on the steel specification, cavity count and production material. P20 steel injection mould (standard Korean cosmetic IBM): 2-3 million cycles before re-polish is required to maintain neck sealing land and cavity surface quality; 8-12 million total cycles before P20 cavity dimensions are outside tolerance from progressive wear and require cavity re-machining or replacement. H13 tool steel injection mould (high-volume Korean cosmetic and pharmaceutical IBM): 5-8 million cycles before re-polish; 15-25 million total cycles before re-machining. S136 stainless steel neck inserts (all Korean cosmetic and pharmaceutical IBM): 5-8 million cycles before re-polish; 20+ million total cycles (S136 corrosion resistance prevents pitting that prematurely terminates P20 neck insert life in humid Korean production environments). Core rod life: hardened nitrided steel core rod (core rod body hardness Rc 55-60) — 10-20 million cycles before core rod body taper wear requires re-grind; blow air channel orifice diameter monitored for enlargement from erosion at 0.5 million cycle intervals. Korea Ever-Power tracks mould cycle counts with production logging on all ZQ IBM machines and issues re-polish and re-machining service recommendations to Korean customers at the appropriate intervals, ensuring IBM container dimensional specifications are maintained throughout the full Korean brand production programme lifecycle.