A CAD scanner — more formally a three-dimensional optical scanner adapted for jewellery applications — is a bench instrument that captures the precise surface geometry of an existing piece of jewellery or a loose gemstone and converts that geometry into a digital model. The resulting file can be imported into computer-aided design (CAD) software for editing, scaling, or direct reproduction, making the technology central to modern jewellery reverse engineering, heirloom replication, and the creation of matched or resized designs.

Operating Principles

Two principal technologies dominate jewellery-grade 3D scanning. Laser triangulation projects a fine laser line or point across the object's surface; a camera offset at a known angle records the distortion of that line, and software triangulates the surface position point by point. Structured-light scanning projects a series of patterned light grids — typically white or blue LED — onto the object and analyses the deformation of each fringe with one or more cameras to reconstruct the surface simultaneously across a wide field. Both methods generate a point cloud: a dense set of three-dimensional coordinates that is subsequently processed into a polygonal mesh.

For jewellery work, scanning accuracy typically falls in the range of 10 to 50 microns (0.01–0.05 mm), which is sufficient to resolve prong profiles, milgrain beading, and engraved detail at the scale relevant to most fabrication tolerances. Sub-10-micron laboratory instruments exist but are rarely required outside of scientific measurement contexts.

Workflow

The practical scanning workflow proceeds in several stages:

• Preparation. Highly reflective or transparent surfaces — polished metal, faceted gemstones — can confuse optical sensors. A temporary matte scanning spray (usually a fine titanium-dioxide or chalk suspension) is applied to reduce specular reflection. The spray is fully removable and leaves no residue on the piece.
• Capture. The object is placed on a rotating turntable or held in a fixture; multiple scans from different angles are taken and automatically aligned by the software using reference targets or feature matching.
• Mesh processing. The aligned point cloud is converted to a closed polygonal mesh, with holes filled and noise filtered. File formats commonly used at this stage include STL, OBJ, and PLY.
• CAD import and editing. The mesh is imported into jewellery CAD platforms such as Rhino with RhinoGold, Matrix, or JewelCAD, where it serves either as a reference underlay for rebuilding clean NURBS geometry or, in some workflows, as a direct basis for 3D printing after mesh repair.

Applications in the Trade

The most common commercial application is heirloom replication: a client presents a worn or damaged piece, the scanner captures its geometry before any restoration work alters it, and the jeweller can reproduce the original form precisely — or use the digital model as the starting point for a sympathetic redesign. Related to this is the production of matched pairs, where a single earring, cufflink, or clip is scanned and its mirror image generated digitally, eliminating the laborious process of hand-measuring and sketching.

Resizing for different stone dimensions is another practical use: a mounting designed around a 7 × 5 mm oval can be parametrically scaled in CAD after scanning to accommodate a 9 × 7 mm stone, preserving all proportional relationships of the original design. This is particularly valuable when a client upgrades a centre stone and wishes to retain the character of a period or bespoke setting.

In larger manufacturing contexts, scanning supports quality control, allowing finished castings to be compared dimensionally against the original CAD model to identify distortion introduced during the casting or finishing process.

Limitations

Optical scanners cannot capture internal geometry — the underside of a closed-back setting, the interior of a tube, or the pavilion of a mounted stone. Computed tomography (CT) scanning addresses this limitation but remains expensive and is rarely deployed in bench jewellery contexts. Additionally, very fine wire gauges below approximately 0.3 mm and knife-edge profiles can fall below the reliable resolution threshold of most jewellery scanners, requiring manual measurement to supplement the digital capture.