Casting from your file
You send a 3D model, we print a pattern from it and cast it in silver or gold. This page explains what the model needs, before the file reaches the configurator.
A model for casting is not a model for printing
A print is the finished object: what you see on screen comes out of the printer. A casting is only the beginning. The resin pattern burns out of the investment, the metal poured into its place shrinks as it cools, and the surface of the raw casting then goes under the grinder and the polisher.
Each of those three steps moves the dimension by tenths of a millimetre, and none of them is visible in the file. That is why we ask more about a casting model than about a printing model. Not to put an obstacle in the way, but so that the piece you finally hold has the dimension you gave us.
You give the finished dimension, we handle the rest
The model should carry the dimensions of the piece you want to receive. Metal shrinkage, the grinding allowance and the sprue layout are added on our side, following the tables on this page. Before you confirm an order we show the whole calculation: target dimension, allowance, shrinkage factor and the pattern size that goes to the printer.
The casting process holds a dimension to 0.2 mm, and that is what we promise. Where tighter accuracy is needed, machining after casting works better, and we agree that separately.
Minimum thicknesses in the finished piece
Two columns, because these are two different statements. “Minimum” is the limit below which the casting will not fill and we do not take the order. “Safe” is the thickness at which reproduction is certain regardless of how the model sits in the flask. Between the two we will cast, but without a promise of full reproduction.
| Model feature | Minimum | Safe |
|---|---|---|
| Wallmeasured automatically from the file | 0.45 mm | 1.0 mm |
| Ring shank | 1.0 mm | 1.3 mm |
| Prong | 0.7 mm | 0.9 mm |
| Free-standing detail | 0.6 mm | 0.8 mm |
| Relief height | 0.3 mm | 0.5 mm |
| Lettering stroke | 0.4 mm | 0.6 mm |
| Gap between parts | 0.8 mm | 1.0 mm |
| Through hole | 0.8 mm | 1.2 mm |
| Edge radius | 0.1 mm | 0.2 mm |
Wall thickness is measured automatically from the uploaded file. The other rows cannot be recognised in a triangle mesh, because that would mean knowing what each feature is: those values stay a design decision.
Metals we cast
Shrinkage is the factor by which we enlarge the pattern so the casting comes out at your dimension. Density gives the mass, and the mass of precious metal dominates the bill. We show both numbers, because everything that happens to the model along the way follows from them.
| Alloy | Shrinkage | Density |
|---|---|---|
| Silver 800 | x 1.017 | 10.20 g/cm³ |
| Silver 925 | x 1.016 | 10.36 g/cm³ |
| Au 9K | x 1.021 | 11.30 g/cm³ |
| Au 585 (14K) | x 1.0196 | 13.10 g/cm³ |
| Au 750 (18K) | x 1.018 | 15.50 g/cm³ |
The table gives the base density of the alloy. White gold takes heavier additions, so at the same volume it weighs noticeably more than yellow, and the quote accounts for that separately.
What you do not have to do
You do not have to scale the model for shrinkage
We do it ourselves, with the factor that belongs to the alloy chosen in the order. If the file is already enlarged, just name the alloy it was scaled for in the configurator: we then add only the difference, and for a matching alloy the file goes to the printer untouched.
Do not add a sprue system
We set the sprues and the pouring cone ourselves, because their position depends on how the model stands in the flask and where the metal has the furthest to travel. A sprue modelled into the file would have to be cut off anyway.
Do not add a machining allowance
We narrow the ring hole ourselves, because grinding makes a hole larger. An allowance on the outer surface is added only for an order with a mirror polish. Both values appear in the calculation shown before you confirm.
Do not add an allowance on a decorated surface
Texture, hammering, engraving and relief never receive an allowance, whatever the chosen finish. Grinding would take away the very detail the order is placed for. Mark the surface as decorated in the configurator and the allowance drops to zero.
What the file needs
- Formats and size
- We accept STL, OBJ, 3MF, STEP, STP, up to 60 MB. The same set as for 3D printing, because there is no reason for a customer to remember that casting reads a file differently.
- Units
- STL and OBJ carry no unit in the format, so we read them as millimetres. The other formats do carry a unit and then we take it from the file.
- A closed solid
- A mesh with no open edges. Without it there is no reading where the metal is and where the air is, and no quote from such a file is binding.
- A single solid
- Several interpenetrating solids leave an undefined region inside. Merge them with a boolean union, or order a file repair from us.
- Flask envelope
- The model has to fit the flask envelope, that is Ø63 x 62 mm. What counts is the diagonal of the footprint, because a flask is a cylinder and not a box: a flat, wide piece fits better than it looks. Anything larger goes to an individual quote.
- Finger hole
- For a ring, a wedding band and a bangle you give the inner diameter of the finished piece. If the hole measured in the file differs from your size by more than 0.2 mm, the order stops: opening the hole eats into the shank, so we do not change it without talking to you.
After upload we compute watertightness, the number of solids, the envelope, the thinnest wall and the hole diameter. The result is visible straight away, before the order is placed, not in an email the next day. On a very dense mesh we skip the thickness measurement and check it by hand, and the configurator says so plainly.
What you receive
- A casting in the chosen alloy
Silver 800 or 925, gold 9K, 14K or 18K. The metal can be ours, or you can supply your own.
- Finishing at the chosen level
From a raw casting with the sprues cut off, to a jewellery finish, meaning grinding, polishing and a check before release. You pick the level in the configurator and see what each one covers.
- Sprue metal where it is yours
With customer-supplied metal the sprues are your metal, so they travel with the casting. With our metal the sprues stay here and go back to the melt.
- Hallmarking by arrangement
The AEJaCA maker's mark and a report to the Polish Assay Office, on request with the order. A piece can also be collected unmarked, the reporting obligation then passes to the recipient.
Frequently asked questions
Should I scale the model for shrinkage before sending it?
There is no need. The model should carry the finished dimensions and we add shrinkage ourselves, with the factor for the ordered alloy. If the file is already enlarged, just name the alloy it was scaled for in the configurator: we then add only the difference, so shrinkage is never applied twice.
How thin a wall will you still cast?
The limit is 0.45 mm, and below it the casting will not fill, so we do not take such an order. Between 0.45 mm and 1.0 mm we will cast, but without a promise of full reproduction, and the configurator says so at upload. Above 1.0 mm reproduction is certain.
What happens if the casting fails?
It is decided by what the model check showed. If the check reported nothing and the casting came out faulty, we repeat it at our own cost. If a warning about a feature of the model was shown before ordering and the order was placed anyway, the repeat is at the customer's cost. That is why warnings appear before the item goes into the basket, not after casting.
Should I add a sprue system to the model?
No. We set the sprues and the pouring cone ourselves, because their position depends on how the model stands in the flask and where the metal has the furthest to travel. A sprue modelled into the file would have to be cut off anyway, and its mark would sit where the caster did not choose.
Which file format and which units should I send?
We accept STL, OBJ, 3MF, STEP and STP, up to 60 MB. STL and OBJ carry no unit in the format, so we read them as millimetres. 3MF and STEP do carry a unit and then we take it from the file. The model has to be a single closed solid, with no open edges.
How large a piece can you cast from a file?
The model has to fit the flask envelope, that is Ø63 x 62 mm. What counts is the diagonal of the footprint, because a flask is a cylinder: a flat, wide piece fits better than three numbers suggest. Anything larger goes through an individual quote, since it needs a different flask and a different setup.
What inner diameter should a ring have in the file?
The target one, the diameter the finished piece should have. We subtract the grinding allowance ourselves, because grinding makes a hole larger. In the configurator you give the finished inner diameter and we compare it with the hole measured in the file: if they differ by more than 0.2 mm, the order stops, because opening the hole eats into the shank and we do not do that without talking to you.
File ready?
Upload the model to the casting configurator. After upload you see the geometry check and the full dimension calculation, before anything is confirmed.