Dimensional Inspection (CMM & 3D Scanning)
Also known as: CMM, Coordinate Measuring Machine, Structured-Light Scanning, Laser Scanning, GD&T Verification, First Article Inspection
Dimensional inspection verifies that an AM part's external geometry meets its drawing tolerances. Coordinate Measuring Machines (CMM) use a touch probe to measure discrete features (bores, datums, GD&T callouts) to micrometre accuracy. Structured-light and laser 3D scanners capture millions of surface points to build a dense mesh that is compared against nominal CAD (colour-map deviation) — ideal for the freeform surfaces AM produces. The two are complementary: CMM for tight-tolerance functional features, scanning for whole-surface form and first-article CAD comparison.
Why AM parts need this
AM parts must be dimensionally qualified before use — and AM's freeform, organic geometry (topology-optimised brackets, conformal-cooled inserts) is exactly where traditional CMM-only inspection struggles and 3D scanning excels. First Article Inspection (FAI) for aerospace and medical AM requires documented dimensional verification mapped to the drawing. Scanning a whole AM part against nominal CAD also quantifies build distortion and shrinkage — feeding back into shrinkage-compensation and orientation decisions for the next build. CMM verifies the machined critical features to PPAP/FAI tolerance after post-machining.
Key parameters
Tactile CMM measurement uncertainty (E0 per ISO 10360). For tight GD&T on machined AM features.
Structured-light / laser. Lower accuracy than CMM but captures full surface — ideal for freeform AM geometry and CAD comparison.
Dense mesh enables colour-map deviation against nominal CAD — visualises distortion and form error across the whole part.
Documented dimensional report mapped to drawing GD&T — required for aerospace (AS9102) and automotive (PPAP) AM qualification.
Compatible materials
Limitations
- Surface/external geometry only — internal porosity and internal channels require CT scanning instead
- CMM is slow and measures discrete points — not ideal for whole-surface freeform AM geometry (use scanning)
- 3D scanning accuracy (10–50 µm) is coarser than CMM (sub-3 µm) — not sufficient alone for the tightest functional tolerances
- Shiny/reflective AM metal surfaces may need matting spray before optical scanning — adds a step and slight thickness
- Detects out-of-tolerance but does not correct it — feeds accept/reject and process-feedback decisions
Providers
Hexagon Manufacturing Intelligence
Swedish measurement-technology conglomerate providing CMMs, structured-light scanners, CT, and AM simulation software for digital quality assurance.
Stockholm, SE
ZEISS Industrial Metrology
German precision-optics and metrology leader offering CT scanning, CMM, and 3D X-ray systems used globally for AM part qualification.
Oberkochen, DE
Creaform
Canadian developer of portable 3D scanning and inspection systems, widely used for as-built dimensional verification and reverse engineering of AM parts.
Lévis, QC, CA
Renishaw — Equator & REVO Gauging
UK metrology OEM — Equator comparative gauging system and REVO 5-axis scanning head for in-process and post-process dimensional inspection of AM parts.
Wotton-under-Edge, GB
FARO Technologies
US OEM of portable CMMs, laser trackers, and 3D scanners — FARO Arm and FaroArm scanners widely used for AM first-article and in-process dimensional inspection on the factory floor.
Lake Mary, FL, US
GOM — ATOS Structured Light Scanners
ZEISS subsidiary GOM (Germany) — ATOS structured light 3D scanners and ARGUS forming analysis systems widely used for AM part dimensional inspection, surface quality, and first-article reporting.
Braunschweig, DE
KEYENCE — 3D Measurement Systems for AM
Japanese sensor and metrology giant KEYENCE — VR Series 3D surface profilometers and IM Series image dimensioning systems for fast, non-contact AM part inspection in production environments.
Osaka, JP
Relevant standards
CMM and 3D-scan accuracy figures from Hexagon, ZEISS, Creaform, and GOM published specifications (manufacturer tier). Standards per ISO 10360 (CMM), VDI-VDE 2634 (optical 3D), AS9102 (FAI).
All post-processing