Technical requirements for plot and cast models
The technique of creating models using CAD has opened up many new possibilities. But there are also physical limits to manufacturing with 3D printers. In addition, it is also necessary to take the restrictions in mould making and wax spraying or in the actual casting process into account in the design, depending on the production method. If all the production steps are considered in advance, this also guarantees a successful result. We have summarised some rules of thumb below that help avoid failed attempts. If you have specific questions about your 3D model, we will be happy to advise you in person.
When creating your data, please note that a 3D printer or plotting machine needs a closed volume to build a body. Non-connected parts, open edges or similar lead to unusable results. The file resolution should be fine enough to provide the machines with enough information. A plotter builds in the hundredths range, data that is too rough leads to small areas on the parts.
The platforms for all our machines are programmed with files in STL format. So you can convert your design data to .STL before sending it. When we receive common formats such as .3DM, Step or Iges, we are happy to convert these for our customers.
An email can be used to transfer data or customers can also alternatively upload files in our order portal with customer login.
As a rule, a minimum wall thickness of 0.5 mm is required for a successful casting. The wall thickness has to be increased accordingly for larger surfaces. Remember that you will lose material when you clean up the castings, ideally this will be calculated during the design process.
If you are planning to make an impression of the piece, the design must be scaled up accordingly. A 0.5%-1.5% addition is useful for silicone moulds, 3.5-4.5% for rubber moulds. It must also be taken into account whether a direct impression is to be taken or whether the model is to be poured out first and cleaned in between. The shrinkage can be even higher with solid and large parts.
If you do not specify the scaling you want when submitting a file, we assume that you have already included the corresponding size losses.
To achieve a good casting result we recommend you design blind holes, lettering, engravings and the like, at least 0.23-025 mm wide. The depth of the lettering/engraving/blind hole should not exceed the width, e.g. a blind hole with D = 0.50 mm should not be deeper than 0.40 mm, or if lettering is 0.23 mm wide, it should not be deeper than 0.23 mm. We achieve consistently good results with stamp and logo engravings with a minimum font width of 0.23 mm and a corresponding depth of 0.23 mm. We are happy to provide any further advice on this topic.
To achieve a good casting result, we recommend you design a relief with lettering and patterns, at least 0.4-0.5 mm, (0.6-0.7 mm is better). The height of the lettering/relief should not exceed the width.
A graphite pencil must be inserted through each hole in the wax model to cast longer through holes. Graphite pencils are available with the following diameters:
Graphite pencil 0,56 mm => Drill hole in model 0,58 mm
Graphite pencil 0,70 mm => Drill hole in model 0,72 mm
Graphite pencil 0,90 mm => Drill hole in model 0,92 mm
Graphite pencil 1,00 mm => Drill hole in model 1,02 mm
Graphite pencil 1,20 mm => Drill hole in model 1,22 mm
Graphite pencil 1,30 mm => Drill hole in model 1,32 mm
Graphite pencil 1,50 mm => Drill hole in model 1,52 mm
Graphite pencil 2,00 mm => Drill hole in model 2,02 mm
Edges which are formed by surfaces which meet at an angle smaller than 60° should be rounded with a radius r=min. 0.15 mm.
We ask you to check your designs against the criteria mentioned above.
Many thanks for your contribution to successful castings.