3D scanning

3D scanning is a non-contact measuring method that captures the shape of a physical object as a point cloud, a set of millions of 3D coordinates describing the object's surface. The resulting data serves as input for reverse engineering, quality inspection or digital archiving.

The most widely used 3D scanning technologies are structured light (suited to medium-sized parts, with an accuracy of roughly 0.02 to 0.05 mm), laser scanning (handheld laser scanners for parts and machines, stationary scanners for large objects) and photogrammetry (large structures and buildings, or as a complement that improves the accuracy of scans of large objects). Each technology differs in preparation effort, scanning time and achievable accuracy.

Industrial 3D scanners can handle complex geometry, including undercuts. Internal channels and deep holes can only be captured to a limited extent and often have to be measured by other means. Highly reflective or transparent surfaces (polished steel, chrome, glass) need a coat of matte powder or spray before scanning.

Processing scan data involves filtering the point cloud, generating a polygon mesh and, if required, reconstructing CAD geometry. The resulting STL model or STEP CAD model can then be used for manufacturing, 3D printing or analysis.

3D scanning is the right tool when you need to capture, quickly and completely, a shape that is hard to measure with calipers: freeform surfaces, castings, molded parts, parts of the human body for ergonomic aids, or entire assemblies when designing mating parts. It is the first step of reverse engineering and the basis for designing covers, fixtures and adapters that must fit existing geometry.

In quality control, it is used to compare a manufactured part with its CAD model (a color deviation map), for example on the first parts from a new mold or when tracking down the cause of warping.

A scanner measures the surface, not the design intent. The result is a mesh of triangles, not a parametric model, and converting it into a usable CAD model is a separate and often more laborious job. Decide up front whether you need just a mesh (STL), a comparison against a model, or a complete CAD model with a drawing.

The accuracy quoted for a scanner is not the accuracy of the whole scan. On large objects, the error accumulates with every scan that is stitched on, unless reference targets or photogrammetry are used. Ask the provider what accuracy they can guarantee for the size of your object, how they will capture holes and shiny surfaces, and in what format they will deliver the data.