From STL file to metal jewellery
This is the guide we use in the workshop. Not theory: these are the settings we
cast our own pieces with. Adjust them to your printer, but start here.
1. Choosing the resin
| Resin type | When to use it | Shrinkage |
|---|---|---|
| Castable wax (20-40 %) | Direct lost-wax casting | Low |
| Wax-free castable | Very thin pieces, extreme detail | Very low |
| Standard grey | Prototypes and size testing only | High |
To test ring size on the finger before casting, print in standard resin: it is
far cheaper and handles being tried on much better.
2. Printing parameters
- Layer height: 25-30 microns. Going below 20 rarely justifies the time.
- Exposure time: start from the manufacturer's value and run a calibration
tower. Overexposing fattens the model and you lose detail in prongs and engraving. - Temperature: 25-28 °C in the vat. Cold castable resin turns thick and
produces badly formed layers.
3. Orientation and supports
- Tilt the ring 30-45° relative to the build plate.
- Place supports on the inner face of the band, never on engraving,
filigree or visible surfaces. - Thin supports (0.3-0.4 mm tips) and many of them beat few and thick ones.
- Leave the sprue on the bulkiest area: that is where metal will enter.
4. Post-processing before casting
- Wash in isopropyl alcohol briefly: castable resin softens if you leave
it soaking. - Dry with compressed air.
- Cure very little, 30 seconds to 2 minutes. An over-cured piece turns
brittle and leaves ash during burnout. - Inspect under a loupe: a badly formed layer will show in the metal too.
5. Burnout cycle
A long, gentle cycle is what separates a clean cast from one full of porosity.
Typical reference for jewellery investment:
| Stage | Temperature | Time |
|---|---|---|
| Drying | 150 °C | 2 h |
| Slow ramp | 300 °C | 2 h |
| Burnout | 730-750 °C | 3 h |
| Down to pour | 500-580 °C | 2 h |
Always confirm the cycle against the datasheet for your investment and
your resin: they vary a lot between brands.
6. Finishing
Cut the sprue, file, sand progressively and finish on a polishing wheel with
compound. On silver, rhodium plating protects against tarnish; on brass, a
lacquer coat stops it marking the skin.
Most common mistakes
The piece comes out porous. Almost always over-curing or too fast a
burnout: ash is left inside the mould.
Engraving detail disappears. Overexposure while printing. Lower the layer
time and repeat the calibration tower.
The ring is the wrong size. Metal and investment shrinkage. Measure what
comes out, work out your factor and apply it before printing: our editable
files let you scale without distorting the design.
Supports leave marks. They were on a visible face. Reorient it — it is
faster to reprint than to polish out a ruined surface.
Ready? Pick your first design.