CAD jewellery design

CAD stands for computer-aided design. Instead of carving a model by hand, a designer builds the piece in software. The design file is sent to a carving mill or printer to be made in wax, ready for casting and finishing. The practical gains: changes are easy to make, a design can be flipped to a mirror image, and it can be scaled. CAD also lets designers develop detailed models before production begins.

The usual order of work is:

1. A brief: sketches, photos or a description, with the ring size, metal and stone sizes.
2. A 3D model built to those dimensions.
3. Renders, and views with measurements, for your approval.
4. A physical pattern, milled or printed.
5. Lost-wax casting of the pattern in metal.
6. Finishing and stone setting.

CAD sits at the front of the process. Casting and finishing still follow it.

Both routes turn the model into a pattern. Machines and materials keep changing, so ask any studio what it uses now.

Milling cuts a block of carving wax. It suits simple shapes without undercuts and fine lettering, but it struggles with hollow sections and long, thin forms, and the cutter leaves a flat tip of about 0.003 inch (0.08 mm). Printing builds a pattern layer by layer, which handles undercuts and hollow interiors. It can leave layer lines, and the surface may not be as crisp as carved wax. For photopolymer resin, one trade author advises avoiding sharp angles or edges, thin holes and lettering more than 0.6 mm high, because resin expands during burnout and can crack the investment.

Resin has one more catch. It does not melt out of the mould as wax does. It begins to decompose at 300 to 400 °C and leaves a solid char residue, and under-cured resin can cause raised blemishes on the finished piece. Printers that jet a wax-based material can help avoid these casting problems. It is a reason to ask which material your pattern uses.

A render is a picture of the model, not the finished ring, so approve the numbers as well as the image. Check these:

• Ring size and width. The inside diameter and band width in millimetres, against the ring size chart. Rings with wide shanks usually need to be a bit larger.
• Stone seats. Each seat should match the measured width of the real stone in millimetres. Melee that differs in size by even 0.20 mm may be noticeable.
• Metal around stones. For pavé, GIA recommends at least a 0.50 mm border, and for a channel setting, walls of 1.00 mm on either side. Ask about prong thickness too.
• Engraving. Spelling, letter height, position, and whether the text is raised or cut in.
• Views. Top, side and underside. Comfort depends on the inside of the ring, which a hero render rarely shows.
• Metal and finish. Colour and polish on screen are approximations.

Changes are far easier on the model than on a cast piece, so raise every question before approval.

A render shows shape and proportion, but it cannot tell you how a ring sits against your knuckle. Ask whether the pattern can be printed in resin or wax so you can try on the size and width before casting, and whether that pattern matches the dimensions of the metal piece.

You can also sketch your idea in the design studio first, then discuss dimensions under custom jewellery design or custom engagement rings. A showroom visit lets you compare widths and sizes on your own hand before the numbers are set.