Minimum wall thickness for casting: gold, silver, platinum
When a piece is cast from wax or resin, the metal has to flow through the narrowest part of the mold too. If a wall is too thin, the metal freezes before it fills that area: an edge comes out incomplete, a prong breaks off, a hole is left in the surface. That is why the thinnest point of a model has to be measured before it goes to casting.
Wall limits per metal
These are the values the Kumpix casting check uses. They come from a caster's recommendation and are still to be confirmed with the workshop (to be verified).
| Metal | Minimum wall | Safe wall |
|---|---|---|
| Gold (14K, 18K, 22K; yellow, white, rose) | 0.6 mm | 0.8 mm |
| Silver (925) | 0.7 mm | 1.0 mm |
| Platinum (950) | 0.6 mm | 0.6 mm |
When a resin print is cast directly, without a rubber mold, the minimum wall is taken as 0.4 mm.
How the check decides
- Red: more than 1% of the measuring points on the surface are below the minimum wall, the area below the minimum wall is larger than 2 mm², or the thinnest point is less than half the minimum wall (a knife edge or a sharp tip). The model is not considered ready for casting, and the thin areas are shown where they are.
- Yellow: the minimum wall is met, but more than 1% of the measuring points, or a surface larger than 2 mm², are below the safe wall; or an area smaller than 2 mm² is below the minimum wall. Casting is possible, but watch that area.
- Green: none of the above: the wall is above the minimum everywhere and above the safe limit almost everywhere.
Besides wall thickness, the check also looks for open edges, disconnected bodies and closed internal voids; if any of these is found, the model is again not considered ready for casting.
Where walls get thin
- Prong tips and the rims of settings
- Hollowed (lightened) shanks and hollow cast earrings such as fizyon
- The bottom of engraved lettering and thin plates
- Filigree and fine wire details
In Kumpix
The casting check runs again after every change, and when you switch metals the limit changes with it. Details are on the casting check page. For the weight of the metal, see 14K, 18K and 22K gold weight.