Lost-wax casting in jewelry making
Lost-wax casting, also called investment casting, turns a wax or castable resin pattern into the same shape in metal. The pattern is set in a plaster-like investment and burned out in a kiln, and molten metal fills the hollow it leaves. The pattern is lost every time, hence the name.
3D Jewelry Designer1 min read
How it works
- Pattern. Carved in wax, injected into a rubber mould for repeat pieces, or 3D printed in castable wax or resin.
- Tree. Sprues join the patterns to a wax trunk, so one flask can hold several pieces.
- Investing and burnout. Investment is poured around the tree in a steel flask, then a kiln burns the pattern out.
- Casting. Molten metal fills the hollow, helped in by vacuum or centrifugal force.
- Clean-up. The investment is broken away and the pieces are cut from the tree, filed and polished.
Patterns from a CAD file
A printed pattern usually starts as an STL file. STL records no units, so confirm millimetres or inches with the printer first. The Jewelry CAD workspace exports STL as a watertight casting mesh, with validity checks.
Before anything is cast, the same model can be rendered for a customer: see Rhino and MatrixGold rendering.
Weight and the pour
More metal is poured than the finished pieces weigh, because the sprues and button are cast too. That extra metal, with what filing and polishing remove, is casting loss. The metal weight calculator gives the finished weight from a 3D file; the caster adds their own allowance on top.
Questions
Can a 3D printed resin pattern be cast?
Yes, if it is printed in a castable resin, made to burn out cleanly. Check the resin with your caster before you print.
Related
- Sprue in jewelry casting
A sprue is the channel that feeds molten metal into a casting mould. The metal that sets in it is cut off, so it is poured but never part of the piece.
- Casting loss in jewelry manufacturing
Casting loss is the metal that never reaches the finished piece: sprues, flashing and polishing. It is why a cast ring weighs less than the metal poured.
- Gold Weight Calculator from a 3D Model
Drop an STL or 3DM file and get the gram weight in 9k to 24k gold, silver and platinum, gross and net of stones. Free.