IBM PP bottle neck OD variation during the first 100–300 ZQ production cycles (start-up drift) is a commonly observed phenomenon at Korea Ever-Power Ansan-si production and is caused by three thermal equilibration processes that occur as the ZQ IBM machine transitions from cold start to steady-state thermal conditions. First, injection cavity tool steel thermal expansion: the H13 steel IBM injection cavity expands thermally as it heats from ambient temperature (typically 20–25°C at Korea start-up in the morning) to its steady-state operating temperature (injection cavity steady-state temperature: approximately 40–60°C for standard PP IBM from contact with 220–235°C PP melt at each cycle). H13 steel thermal expansion coefficient approximately 11 × 10−6/°C: for a 28mm OD injection cavity bore, a 35°C temperature rise from ambient to steady-state produces bore OD expansion Δd = 28 × 11 × 10−6 × 35 = 0.011mm. This tool expansion means the injection cavity bore is 0.011mm smaller at steady-state than at cold start — producing IBM bottle neck OD approximately 0.01mm smaller at steady-state than at start-up. Second, core rod thermal expansion: the ZQ core rod also heats from ambient to steady-state (core rod steady-state temperature typically 50–80°C from repeated PP melt contact) — core rod OD increases slightly at steady-state, reducing the preform annular neck wall slightly (core rod OD ↑ ⇒ preform neck wall ↓). Third, PP process temperature stabilisation: ZQ barrel heater PID controller takes 20–50 cycles to reach thermal steady state from cold start — melt temperature variation during thermal stabilisation produces PP shrinkage variation and therefore IBM neck OD variation in start-up bottles. Korea Ever-Power Ansan-si standard practice: ZQ IBM machines warm up for 30–50 cycles (start-up purge + initial production cycles held as “warm-up scrap”) before production starts and neck OD measurement is taken. Only after ZQ barrel temperatures, injection cavity temperature and core rod temperature have reached steady-state (confirmed by 10 consecutive IBM bottle neck OD measurements within ±0.03mm) does Korea Ever-Power Ansan-si production begin generating conforming IBM bottles for customer shipment.

Customer-proprietary IBM neck finishes (closure systems designed and owned by the cosmetic or pharmaceutical brand, not based on published GPI/BPF standards) are among the most demanding IBM neck engineering projects at Korea Ever-Power Ansan-si because the neck geometry must be reverse-engineered from the brand’s proprietary closure physical sample or 2D drawing and exactly replicated in the IBM injection cavity without access to the closure supplier’s tolerance specification sheet. Korea Ever-Power’s process for proprietary IBM neck engineering: step 1 — closure sample dimensional analysis: the brand provides 5–10 closure body samples (injection-moulded PP or HDPE caps, pump bodies or flip-tops) from their proprietary closure tooling. Korea Ever-Power Ansan-si dimensional team measures all relevant closure inner engagement dimensions (closure body inner thread profile, closure snap-collar inner groove OD, TE skirt engagement inner OD) using calibrated digital micrometer (±0.001mm) and optical comparator projection profile measurement. Step 2 — IBM neck target dimension calculation: IBM bottle neck OD = closure body engagement inner OD ± interference/clearance designed for the specific closure function (screw cap: 0.0–0.1mm clearance between cap thread and bottle thread for screw fitment; snap bead: 0.2–0.4mm positive interference for snap retention). Step 3 — injection cavity machining: Korea Ever-Power Ansan-si mould shop machines injection cavity neck geometry per calculated IBM bottle neck specification (EDM thread, CNC bore, CNC bead). Step 4 — T1 fitment validation: T1 IBM bottle samples sent to brand for proprietary closure fitment test — brand’s closure QC team installs proprietary closure on T1 IBM bottle and measures: cap application torque (screw), snap-in force (pump/bead), snap-out force (retention), TE skirt break torque (first-opening). Korea Ever-Power adjusts injection cavity dimensions based on T1 fitment data for T2 validation before FAI approval of proprietary neck IBM bottle programme. All proprietary closure dimension data held under NDA at Korea Ever-Power Ansan-si.

Dropper assembly fitment on IBM serum bottles (18/415 or 20/415 narrow-neck PP IBM pharmaceutical vial or cosmetic eye serum IBM bottle) requires IBM neck geometry specifically designed for the dropper collar (aluminium or PP collar retaining the rubber bulb and glass or PP dropper pipette). IBM neck design features for dropper assembly: smooth bore IBM neck inner surface (Ra ≤0.4μm on core rod neck OD to produce smooth inner bore) for dropper pipette insertion and removal without surface drag. Crimp-collar IBM neck (aluminium crimp collar dropper): IBM neck outer bead or knurled zone below thread for aluminium crimp collar deformation during assembly (crimp collar crimped mechanically onto IBM bottle neck during pharmaceutical filling line assembly, permanently retaining rubber bulb-pipette assembly). IBM neck bead OD and knurl dimensions at ZQ injection station designed for target crimp force (50–120 N press-on force for pharmaceutical dropper crimp assembly). Screw-collar dropper IBM neck (PP screw-collar dropper): IBM 18/415 or 20/415 thread on bottle neck for PP screw-collar dropper (screw-collar with integrated rubber bulb retains pipette by threading onto IBM bottle neck). IBM thread OD ±0.05mm for consistent screw-collar application torque at pharmaceutical filling line. Dropper orifice tip insert: some IBM pharmaceutical serum IBM bottles have a dropper orifice tip insert (small PP orifice insert snapping into IBM bottle mouth bore) that limits dropper bottle flow to single-drop dispensing. IBM bottle mouth bore OD (inner bore formed by core rod neck OD) machined at ±0.02mm for consistent dropper tip insert snap-in force across IBM production. Korea Ever-Power produces 18/415 and 20/415 narrow-neck IBM PP serum and pharmaceutical dropper bottles on ZQ40 IBM machine (highest cavity count for small-format dropper IBM bottles at Ansan-si: 10–12 cavities for 10–30ml PP narrow-neck dropper IBM bottle on ZQ40) for Korean pharmaceutical and cosmetic brand eye serum, OTC pharmaceutical liquid and dermatology product IBM packaging programmes.

At ZQ IBM Station 2 (blow station), the preform carried on the core rod enters the blow mould cavity. The blow mould cavity body and base sections close around the preform body and base, but the IBM bottle neck sits above the blow mould cavity parting line, outside the closed blow mould. The IBM preform neck is supported at Station 2 by the neck ring (also called neck plate or neck split): two halves of a precision machined ring that mate around the IBM preform neck OD at the blow mould parting plane, providing: lateral support for the IBM preform neck against blow pressure-induced lateral movement during blow inflation (without neck ring support, blow air pressure at 4–8 bar acting inside the preform body could push the preform radially within the blow mould cavity, causing asymmetric body wall distribution); vertical support for the IBM preform-plus-core-rod assembly weight in the blow station (the neck ring supports the weight of the preform and core rod suspended from the injection station machine platen during blow dwell). The neck ring inner OD dimensions at Korea Ever-Power ZQ machines are machined to match the IBM preform neck OD at production tolerance + 0.1–0.2mm clearance: neck ring inner OD = IBM preform neck OD + 0.15mm clearance. This clearance allows the IBM preform neck to enter and exit the neck ring during ZQ station indexing without scraping (neck ring clearance 0.15mm > ZQ indexing positional tolerance 0.05mm for smooth neck ring entry) but tight enough to prevent lateral preform movement during blow. Neck ring clearance is important because excessive neck ring wear (neck ring inner OD increases over IBM production cycles as PP/HDPE preform neck contacts neck ring at indexing) produces increasing preform lateral movement at blow station, which can cause IBM body wall asymmetry (one side thinner than opposite side from preform-off-centre blow expansion). Korea Ever-Power monitors neck ring wear by quarterly dimensional measurement at Ansan-si and replaces neck rings when inner OD exceeds IBM preform neck OD + 0.25mm clearance to maintain IBM body wall symmetry specification.