Why use both a CMM and an optical projector on a neck ring?

The CMM measures three-dimensional relationships such as concentricity and position, while the optical projector shows the magnified thread and neck finish outline in one plane. Together they cover both fit and profile.

Is a 3D scanner more accurate than a CMM?

Not for fit diameters. A scanner is faster at capturing whole freeform surfaces such as blow mold cavities; a tactile CMM is generally the better choice for tight tolerances on cores, cavities and plates.

What does bottle sample inspection add if the mold parts already passed?

It checks the result of the whole system — mold, cooling and process — on real preforms and bottles: weight, wall thickness, neck dimensions and capacity.

Can I receive measurement data with my mold or spare parts?

Yes. LIHE supplies validation and inspection reports with molds and spare parts on request.

Why does temperature matter for CMM measurement?

Steel expands as it warms, so a part measured at a different temperature reads a different size. Stable temperature in the measuring room keeps CMM results comparable.

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QC equipment

QC Equipment

Our quality control lab verifies every mold component before shipment using a Zeiss 3D coordinate measuring machine, 3D profile scanner, optical projector and dedicated bottle sample inspection equipment. Cores, cavities, neck rings and blow mold cavities are checked against drawings, and sample preforms and bottles are measured before a mold leaves the factory.

Zeiss CMM: 3D coordinate measurement of cores, cavities, neck rings and mold plates.
3D profile scanner: Contour and surface checks of blow mold cavities and complex shapes.
Optical projector: Two-dimensional measurement of neck finish profiles and small features.
Bottle inspection: Sample preform and bottle checks, including wall thickness and dimensions.
Documentation: Inspection reports supplied with molds and spare parts on request.

Quotes and technical questions are handled directly by the manufacturer's international sales department.

QC equipment reference for PET preform and blow molds: Zeiss CMM, 3D profile scanner, optical projector and bottle inspection

Updated October 13, 2026Author: LIHE Precision Engineering Team

QC equipment in mold making refers to the measuring instruments used to verify that mold components and the parts they produce match the drawing and the CAD model. 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 page is an instrument-by-instrument reference: how each instrument in LIHE's QC lab works, which features it is suited to, and where its limits are.

Zeiss CMM: three-dimensional measurement of cores, cavities and plates

A coordinate-measuring machine (CMM) moves a probe along three perpendicular axes and records the X, Y and Z position of each point it touches. Software fits these points to geometric elements — circles, cylinders, cones, planes — and compares them with nominal values. LIHE runs an in-house Zeiss CMM lab.

How it measures: the part is aligned to its datums, then the probe touches or scans the surface. Results are reported in millimeters, usually to the micron level.
Typical features on PET mold parts: core and cavity diameters, taper, concentricity between features, stack lengths, bore positions on plates and the geometry of gate seats.
Why it matters: the preform wall is the gap between core and cavity, so their relationship in three dimensions has to be measured, not assumed. LIHE mold bases are also verified on the Zeiss CMM.
Limits: contact measurement takes time per point, and results depend on stable temperature, correct fixturing and a calibrated probe.

3D profile scanner: freeform surfaces of blow mold cavities

A 3D profile scanner captures a dense cloud of surface points without touching the part, typically by projecting light patterns or laser lines and recording them with cameras. The point cloud is aligned to the CAD model, and deviations are shown as a color map across the whole surface.

Typical features: bottle contours, shoulder and base shapes, grip panels, embossed text and logos in blow mold cavities, and other complex shapes.
Why it matters: a bottle shape cannot be described by a few diameters; a full-surface comparison shows local deviations that point measurements would miss.
Output: a deviation color map and section profiles compared with the 3D model.
Limits: for tight fit diameters a CMM is usually the more precise choice, and highly polished surfaces can be harder to capture optically.

Optical projector: two-dimensional profiles of neck finishes and small features

An optical projector, also called an optical comparator, projects a magnified silhouette of a part onto a screen. The operator compares the outline with an overlay drawing or measures distances and angles directly on the screen. It measures without contact and is fast for profiles.

Typical features: thread profiles and neck finish outlines on neck rings, small radii, chamfers, edges and step heights.
Why it matters: neck finishes such as PCO 1881, PCO 1810, 1716, 3025 or 2925 must match the closure; a magnified outline shows thread form errors clearly.
Output: dimensions and a pass or fail comparison with the profile drawing.
Limits: it sees only the silhouette in one plane, so three-dimensional relationships still need the CMM.

Bottle and preform sample inspection: checking what the mold produces

Instruments that measure steel parts cannot confirm how the mold behaves in production. LIHE's QC equipment therefore includes dedicated bottle sample inspection, which measures sample preforms and bottles.

Preform checks: weight in grams, wall thickness and its uniformity around the circumference, neck finish dimensions and length.
Bottle checks: overall dimensions, wall thickness distribution from neck to base, and capacity — for example on 330ml, 500ml, 550ml or 1.5L water bottles.
Why it matters: uneven preform walls cause uneven stretching in blowing; bottle walls that are too thin can fail, especially in hot fill at about 85–95°C.
Limits: sample results describe the samples tested, so the number of samples per cavity should be agreed for multi-cavity molds.

Instrument comparison for PET mold inspection

Instrument	Measuring principle	Contact	Best for	Main limitation
Zeiss CMM	Probe points in X, Y, Z fitted to geometry	Yes (tactile probe)	Diameters, concentricity, positions, cores, cavities, plates	Slower per point; needs stable temperature
3D profile scanner	Optical point cloud compared with CAD	No	Freeform blow mold cavities, complex shapes	Less suited to tight fit diameters; reflective surfaces
Optical projector	Magnified silhouette on a screen	No	Neck finish threads, radii, edges, small features	Two-dimensional profile only
Bottle sample inspection	Measurement of produced preforms and bottles	Varies	Weight, wall thickness, neck dimensions, capacity	Describes samples, not every part

How a feature is matched to the right instrument

Step 1: Identify the feature type on the drawing: fit diameter, position, profile, freeform surface or product property.
Step 2: Choose the instrument: CMM for three-dimensional relationships, optical projector for planar profiles, 3D profile scanner for freeform surfaces, sample inspection for preform and bottle properties.
Step 3: Align the part to the same datums used for machining, so that the measurement reflects how the part will sit in the mold.
Step 4: Measure and compare each result with its nominal value and tolerance.
Step 5: Record the results; LIHE supplies validation and inspection reports with molds and spare parts on request.

What the instruments support for buyers

Capability: LIHE tooling consistently achieves CPK ≥ 1.33, which can only be shown with repeatable measurement.
Interchangeability: 100% interchangeable conversion parts for Husky, SACMI, SIPA, NETSTAL, MHT, OTTO, ASB, Krupps and Corvaglia systems depend on parts being measured against the same reference.
Low defect rates: operational defect rates as low as 0.0064% depend on every cavity being verified, not only a few.

Frequently asked questions

Why use both a CMM and an optical projector on a neck ring?: The CMM measures three-dimensional relationships such as concentricity and position, while the optical projector shows the magnified thread and neck finish outline in one plane. Together they cover both fit and profile.
Is a 3D scanner more accurate than a CMM?: Not for fit diameters. A scanner is faster at capturing whole freeform surfaces such as blow mold cavities; a tactile CMM is generally the better choice for tight tolerances on cores, cavities and plates.
What does bottle sample inspection add if the mold parts already passed?: It checks the result of the whole system — mold, cooling and process — on real preforms and bottles: weight, wall thickness, neck dimensions and capacity.
Can I receive measurement data with my mold or spare parts?: Yes. LIHE supplies validation and inspection reports with molds and spare parts on request.
Why does temperature matter for CMM measurement?: Steel expands as it warms, so a part measured at a different temperature reads a different size. Stable temperature in the measuring room keeps CMM results comparable.