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3D Measurement & Quality Control

At Norm Additive, the scope of dimensional verification — which dimensions, using which method, and with what reporting — is determined by the part's geometry, tolerances and project requirements. We verify critical dimensions with a coordinate measuring machine (CMM) and deliver the agreed reporting.

3D Measurement & Quality Control
How does coordinate measurement work?

A coordinate measuring machine (CMM) is a measurement system that precisely determines the X, Y and Z coordinates of points on a part’s surface in space, numerically reconstructing its geometry. A measurement sensor — a tactile probe or a suitable optical sensor — collects coordinates from the surface; software fits geometric elements such as planes, circles and cylinders to these points and calculates quantities like diameter, flatness, position and cylindricity from them. A caliper measures a single dimension at a single point; a CMM evaluates the part’s entire geometry within a coordinate system — that’s the essential difference. We collect points in two ways. Touch-triggering point by point gives fast, stable measurements of holes, planes and dimensions. Continuous scanning gathers a dense set of points across the surface, which is necessary to properly evaluate form/profile characteristics such as cylindricity, roundness and freeform surfaces. Which method is used depends on the characteristic being measured.

Fixturing and datum alignment
Fixturing and datum alignment

Over-clamping a thin-walled part turns what you measure into the shape the clamping force gave it, not the part's true geometry — one of the most common sources of measurement error. After fixturing, the part's own reference system is established: whatever the A-B-C datums define on the technical drawing, the CMM's coordinate system establishes the same thing (the classical method is the 3-2-1 alignment, built from a primary plane, a secondary line and a tertiary point).

Engineering Note

If the datum is set up incorrectly, the measurement report is wrong even if each individual number is correct. A measurement is only meaningful when the part's reference system is established exactly as the drawing's datum definition specifies. That's why clarifying critical dimensions and datums at the design stage is a precondition for reliable verification — we start building quality at the design stage, not at delivery.

GD&T: What Does a CMM Actually Prove?

A CMM’s real job isn’t to produce raw measurements — it’s to prove that the tolerances defined on the technical drawing are met. That tolerance language is GD&T (geometric dimensioning and tolerancing). It shows what a caliper cannot:

  • Form — flatness, roundness, cylindricity (a surface’s deviation from its own ideal form)
  • Orientation — perpendicularity, parallelism, angularity (angular deviation relative to a datum)
  • Location — position tolerance, concentricity (a feature’s location relative to the datum system)
  • Runout and profile — circular/total runout; the deviation band of a freeform surface from nominal

For a part with tight position and profile tolerances, only a CMM (or an equivalent 3D measurement system) can prove conformance.

Measurement Infrastructure

We carry out dimensional verification at our facility in Izmir, using our Zeiss coordinate measuring machine integrated with our production processes — so responsibility never splits as a part moves from production to measurement.

Coordinate measuring machine Zeiss CMM
Measurement mode Tactile probing and scanning
Accuracy level Micron-level
Calibration Traceable, periodic verification

Measurement Uncertainty and Traceability

A number that has no known uncertainty isn’t engineering data. A measurement result only becomes meaningful when its uncertainty is evaluated alongside the part’s tolerance: if the measurement system isn’t sufficiently capable relative to that tolerance, the result alone doesn’t support a reliable conformance decision. Common practice in measurement system analysis (MSA) is that measurement uncertainty should be a small fraction of the tolerance band — typically a 10% target, with 20–30% as an upper limit.

 

Temperature is one of the biggest factors driving uncertainty. The reference temperature for dimensional measurement per ISO 1 is 20°C; since aluminum’s coefficient of thermal expansion is roughly 23 µm/m·K, a one-meter aluminum part changes size by about 115 µm for a 5°C deviation. That’s why environmental control in precision measurement isn’t optional — it’s a requirement. Measuring equipment accuracy is defined through ISO 10360 acceptance and periodic verification tests; a measurement result needs to be traceable to national/international standards. We measure under controlled conditions, with equipment whose calibration is traceable.

CAD-to-Part Comparison and Reporting

We report a part’s conformance to design by comparing the measured geometry against the CAD model. Depending on the verification method and software used, results can be presented as a dimensional table, a geometric report, or a deviation map. A serious report includes the part/revision number, date and operator, equipment and calibration status, datum definition, and a nominal / tolerance / measured / deviation / conformance record for every characteristic. This matters especially for complex-geometry parts made by metal additive manufacturing.

Workflow

From scan to manufacturable model

  • 1
    Scan planning

    The part's size, surface complexity and critical dimensions are assessed; the right scanning method and resolution are chosen.

  • 2
    3D scanning

    The surface is captured as a dense point cloud using optical/laser scanning; aligned to reference markers where needed.

  • 3
    Modeling from the point cloud

    A surface or solid CAD model is built from the point cloud. For reproduction the geometry is modeled faithfully; for development it's modeled parametrically and editably.

  • 4
    Verification

    The manufactured part's conformance to the CAD is verified with a deviation map, or by CMM measurement for critical dimensions.

  • 5
    Production

    The model is taken into production with the appropriate technology: metal or polymer 3D printing, or hybrid production where needed.

Quality Documentation We Deliver

Depending on your request and our agreement, we provide any of the following:

First Article Inspection Report (FAI)

Documented verification that the production process meets every requirement on the drawing; in the AS9102 format for aerospace.

Certificate of Conformance (CoC)

A document declaring the part's conformance to the specified material and specification.

Material / lot traceability

The lot record of the powder used — not the same thing as a CoC.

PPAP

The dimensional-results portion of the automotive series-production approval package.

Measurement report

A record of the dimensional results and deviations.

Measurement on Additive Manufacturing Parts

In metal L-PBF, residual stress accumulates as each layer melts and solidifies; once the part is cut from the plate it opens up or closes slightly, and you can't know that deviation without measuring it. The same geometry behaves dimensionally differently when printed in a different orientation (anisotropy), and each post-process step — heat treatment, HIP, blasting or machining — changes the dimensions further. That's why measurement happens at the end of the process, and at intermediate steps where needed; a new parameter set, a new powder lot, or a new build orientation should never go into series production without being confirmed by measurement.

Measurement Infrastructure
Criterion Tactile CMM 3D Scanning (optical / laser)
Strong for Hole diameter, position, GD&T tolerances How the whole surface matches nominal
Data Selected critical points Full surface (dense point cloud)
Freeform surfaces Weak-to-moderate Very strong
Soft/flexible parts Contact can cause deformation Non-contact, advantageous
Reverse engineering Not suitable Primary method
Typical use FAI/PPAP, formal verification of tight tolerances Full-surface comparison, warping, digitization

In short, a CMM answers “are these critical dimensions within tolerance?” while scanning answers “what's the state of the whole geometry / how do we recapture it?” If your project needs full-surface capture or geometry extraction, we look at reverse engineering and 3D scanning.

Next Step

Let's get your part scanned and modeled.

Making sure a part's 2nd, 10th and 100th copy are all the same comes from controlled production parameters and processes. Measurement doesn't create that repeatability — it verifies and tracks it. Once process parameters are locked in, we track within-lot and lot-to-lot consistency through measurement; the calibration and traceability of our measurement equipment is the foundation of that tracking.

Share the part, or a photo and its dimensions; let's work out the scanning method, modeling approach (reproduction or development) and verification plan together.

Share your part's tolerance, reporting and certification expectations; let's define the measurement and verification process for your project together.

QUALITY PROCESS CONSULTATION
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