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Every PET preform mold undergoes rigorous dimensional verification using industry-leading metrology systems. Our QC lab is equipped with Zeiss coordinate measuring machines (CMM), high-resolution 3D profile scanners, optical comparators, and dedicated bottle sample inspection equipment — ensuring every mold core cavity and neck ring component conforms to specification before shipment.
Key Capabilities
Our quality control equipment and systems
- ✓Zeiss CMM (3D coordinate measurement)
- ✓3D profile scanning
- ✓Optical comparators
- ✓Bottle sample inspection systems
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PET preform mold quality control workflow: inspection from steel to sample preforms and bottles
A mold inspection workflow is the sequence of measurements a mold maker carries out from raw material to finished mold, so that every stage is checked before the next one adds cost. LIHE Precision (Foshan Lihe Precision Machinery Co.,Ltd.) is a manufacturer of PET preform molds, blow molds, closure and compression molds, hot runner systems and mold components for the beverage and packaging industry, with manufacturing in Foshan, China. This guide walks through what is measured at each stage — incoming steel, machined components, assembly and sample preforms or bottles — and what an inspection report should contain.
What a PET mold inspection workflow covers
Quality control in mold making is not a single final check. A deviation found on a finished mold is expensive to fix, while the same deviation found on a single core before assembly costs one rework. A staged workflow therefore measures at four points.
- Incoming material: is the steel the right grade and condition before machining starts?
- Machined components: does each core, cavity, neck ring and insert match the drawing?
- Assembly: do the parts fit together, align and interchange across all cavities?
- Sample parts: do the preforms or bottles the mold produces meet the product specification?
- Reference figures: tooling capability of CPK ≥ 1.33, defect rates as low as 0.0064%, mold bases for preform molds up to 160 cavities and replacement parts in 4 weeks.
Stage 1 — incoming steel and blanks
Mold steel determines wear resistance, polishability and corrosion behavior over the life of the mold. Common incoming checks in the industry are simple but prevent the most expensive kind of failure: a part machined perfectly from the wrong material.
- Material certificate from the steel supplier compared with the grade on the drawing.
- Hardness check of the blank, or of the part after heat treatment, against the specified range.
- Visual and dimensional check of blank size so that the finishing allowance is sufficient.
- Identification of each blank so that the part can be traced back to its material batch.
Stage 2 — machined mold components on the Zeiss CMM, scanner and projector
Component inspection is where most measuring time is spent. LIHE uses an in-house Zeiss CMM lab, a 3D profile scanner and an optical projector at this stage. Features are measured against the CAD model and the drawing tolerances.
- Cores and cavities: diameters, lengths, concentricity and the geometry that sets preform wall thickness — measured on the CMM.
- Neck rings: thread and neck finish profiles such as PCO 1881 or 29/25 — measured on the CMM and checked as a two-dimensional profile on the optical projector.
- Gate inserts and hot runner parts: small bores and seats that control gate quality and sealing — measured on the CMM.
- Mold plates and mold base: flatness, hole positions and parallelism that keep up to 160 cavities aligned.
- Blow mold cavities: freeform bottle contours compared with the 3D model on the 3D profile scanner.
Stage 3 — assembly, fit and interchangeability checks
Individually correct parts can still assemble badly if fits, stack heights or alignment features do not work together. Assembly checks confirm that the mold behaves as one unit.
- Stack fit: each core, cavity and neck ring set closes and aligns without forcing.
- Interchangeability: parts from one cavity fit any other cavity. LIHE supplies 100% interchangeable conversion parts for Husky, SACMI, SIPA, NETSTAL, MHT, OTTO, ASB, Krupps and Corvaglia systems.
- Cooling circuits: water channels are open and correctly connected so that every cavity cools evenly.
- Moving and sealing surfaces: clearances are checked so that the mold can run up to 8 million shots on Husky, SACMI and Netstal platforms.
Stage 4 — sample preform and bottle inspection
The final proof of a mold is the part it makes. LIHE's QC equipment includes dedicated bottle sample inspection for this stage. Typical checks on sample preforms and bottles include:
- Preform weight in grams, which matters when a lightweighting project removes 1g to 2g from a design.
- Wall thickness and its uniformity around the circumference, which affects blowing.
- Neck finish dimensions, so that the closure seals on the filling line.
- Overall length and visual defects such as gate marks or flash.
- For blow molds: bottle dimensions, wall thickness distribution and capacity, for example on 330ml, 500ml or 1.5L water bottles.
Inspection stages compared
| Stage | What is measured | Typical instrument | Record produced |
|---|---|---|---|
| Incoming steel | Grade, hardness, blank size | Certificate review, hardness tester, gauges | Material record per batch |
| Machined components | Diameters, lengths, concentricity, profiles, positions | Zeiss CMM, optical projector, 3D profile scanner | Dimensional report per part |
| Assembly | Fit, alignment, interchangeability, cooling circuits | Assembly checks, CMM for critical features | Assembly checklist |
| Sample preforms | Weight, wall thickness, neck finish, length | Bottle and preform sample inspection | Sample inspection report |
| Sample bottles | Dimensions, wall distribution, capacity | Bottle sample inspection, 3D profile scanner | Sample inspection report |
What the inspection report should contain
LIHE supplies validation and inspection reports on request. A useful dimensional report is traceable and lets a buyer compare measured values with tolerances without guessing.
- Part identification, drawing number and revision.
- Nominal value, tolerance, measured value and deviation for each feature.
- Pass or fail status, instrument used and date of measurement.
- For repeated features across many cavities, capability statistics. LIHE tooling consistently achieves CPK ≥ 1.33.
How to request and review inspection reports
- Step 1: State in the purchase order which parts need dimensional reports — for example all cores, cavities and neck rings of a new preform mold.
- Step 2: List the critical features that matter to your line, such as neck finish, preform weight or a specific Husky or SACMI interface.
- Step 3: When the reports arrive, check that each part number matches the parts in the shipment.
- Step 4: Compare measured values against tolerances and look at how centered they are, not only whether they pass.
- Step 5: Keep the reports as a baseline, so that worn parts can later be compared with their original dimensions during maintenance or replacement.
Frequently asked questions
- Which stages of mold production does LIHE inspect?
- LIHE's QC equipment — Zeiss CMM, 3D profile scanner, optical projector and bottle sample inspection — covers machined components and the sample preforms and bottles a mold produces. Validation and inspection reports are supplied on request.
- Why measure components before assembly instead of only testing the finished mold?
- A deviation found on a single core costs one rework. The same deviation found after assembly may require taking the mold apart and delaying shipment, so staged inspection protects the lead time.
- What is checked on sample preforms?
- Typically weight in grams, wall thickness and its uniformity, neck finish dimensions, length and visual defects such as gate marks or flash.
- What does CPK ≥ 1.33 tell me in an inspection report?
- It shows that a dimension repeated across parts is both centered and consistent: the process average is at least four standard deviations from the nearer tolerance limit. LIHE tooling consistently achieves this level.
- Can I use the inspection report later for spare parts?
- Yes. The original measured values are a useful baseline when comparing worn parts, and they support ordering replacement parts, which LIHE supplies with a 4-week lead time.