Learning how to prepare a jewelry CAD model for wax printing and casting is the biggest factor in whether a piece comes out of the flask clean or comes out with porosity, broken prongs, and a redo bill. After more than two decades running our jewelry services in Glendale, we can usually tell within a minute of opening a file whether it was built by someone who has cast before. The rules are not complicated; they just have to be applied before the model goes to the printer.
Why Preparing a Jewelry CAD Model for Wax Printing Matters
A jewelry CAD file is not just a picture of the ring. It is the exact geometry that gets printed in wax or castable resin, invested in plaster, burned out, and filled with molten metal. Every thin wall, sharp internal corner, and floating detail becomes a physical problem downstream. Wax printers can resolve features a caster cannot reliably fill, so a model that prints beautifully can still fail at the casting stage. Preparing the model correctly means designing for the weakest link in the chain, which is usually metal flow and shrinkage, not printer resolution.
Minimum Wall Thickness and Feature Size for Castable Models
The most common problem in files sent to us is walls that are too thin to cast. Our general guidance is a minimum wall thickness of about 0.8 mm for sterling silver and 0.6 to 0.7 mm for gold and platinum, with 1.0 mm a much safer target on larger surfaces like wide bands and signet tops. Thinner areas tend to fill incompletely, warp during burnout, or bend during finishing.
Fine details follow the same logic. Raised lettering, milgrain, and filigree should generally be at least 0.3 to 0.4 mm wide and tall, or they either fail to print or disappear the moment the piece is polished. Engraved or recessed details should be at least 0.2 to 0.3 mm deep so they survive finishing.
Shanks, Galleries, and Hollowed Pieces
Ring shanks should rarely go below 1.5 mm in height at the thinnest point, and 1.8 to 2.0 mm is a more durable choice for daily wear. Open galleries under a center stone look elegant in CAD, but the bars that form them need real cross-section, typically 0.9 mm or more, to hold up in metal. Hollowing a heavy piece to save weight is fine, but keep the shell thickness consistent and add a vent hole so investment can escape.
Prong and Setting Design That Survives Casting
Prongs are the most failure-prone feature in a jewelry CAD model because they are tall, thin, and isolated. We recommend modeling prongs slightly oversized, around 0.9 to 1.1 mm in diameter for a typical center stone, and tapering them only above the seat so there is enough metal at the base. The setter will trim and shape them by hand, so leave material rather than modeling the finished tip. Cut the seat at the actual stone dimensions plus a small clearance, and confirm stone sizes before the file is finalized, because resizing a setting after casting is far more work than editing the model.
For bezels and channel settings, keep the wall that will be pushed over the stone between 0.4 and 0.6 mm at the top and thicker toward the base. Pavé fields need consistent spacing with enough metal between holes, usually no less than 0.3 mm, so beads can be raised without breaking through.
Accounting for Casting Shrinkage in Your CAD Model
Metal shrinks as it cools, and so does the wax or resin pattern during burnout. The combined effect is small but real: roughly 1.5 to 2 percent for silver and gold alloys, with platinum on the higher end. A ring modeled at exactly size 7 will typically cast slightly smaller. The usual fix is to scale the model up by about 1.5 to 2 percent before printing, or to model the ring a fraction of a size larger than the target. Stone seats shrink too, which is another reason to leave a little clearance and let the setter do the final fitting. If we handle the wax printing and casting, we apply the scale factor for the chosen metal ourselves; if you manage the file, ask your caster which factor they use, since it depends on their investment and burnout process.
File Export Checklist Before Sending a Jewelry Model
Once the geometry is right, export is where clean models get ruined. Check that the mesh is watertight with no naked edges or flipped normals, that all bodies are unioned into a single solid rather than overlapping pieces, and that curved surfaces are exported finely enough to avoid visible faceting. An STL at a tolerance of around 0.01 mm is standard for jewelry; a 3DM or STEP file is even better if you want us to be able to edit the model. Include the intended metal, ring size, stone sizes, and finish so we can check shrinkage and wall thickness against the actual job. Fixing a 0.5 mm wall in CAD takes minutes. Discovering it after casting means a second wax, a second flask, and another week.
Get Your Jewelry Model Reviewed, Printed, and Cast in Los Angeles
Whether you are a designer with a finished file or a jeweler who needs a sketch turned into a castable model, we can review your jewelry CAD model, print it in wax or castable resin, and cast it in the metal of your choice under one roof. Request a quote from eCadCam in Los Angeles, or call us at 213.489.1173 and we will look at your file before you commit to a print.