Basic information on tolerances in 3D printing
Compared to injection moulding or machining processes, the possible deviations are greater in 3D printing. In the injection moulding of plastics, tolerances in the tenth range are possible, and in the machining of metal, worked in the hundredths. Deviation tolerance is at least 0.1 mm in most processes.
Often, confusing the terms “resolution” and “tolerance” results in misunderstandings. The resolution of a Polyjet printer of only 15 μm does not, for example, mean that the tolerance is just as low. Here you have to deal carefully with the different terms.
Converting file format from STP to STL
For processing in 3D printing, an appropriate STL file must be available. This can either be created directly in a CAD programme or converted from an existing CAD file.
However, the conversion from STP to STL data may result in inaccuracies in the hundredths range. This is due to the different types of surface mapping. The STP format uses a data algorithm that presents the data in more detail than the STL format. This is due to the transformation of the surface into a kind of mesh of triangles, simplifying the representation of shape in STL format.
Therefore, the lower the resolution, the larger the deviations become. The other way around, the larger the resolution, the larger the data becomes, with the result that they may not be processed properly. Here you have to be a little bit adventurous as a 3D-printing newcomer or, if necessary, get advice from the specialist. Many providers of 3D printing offer appropriate services and assist in the creation or conversion of CAD data.
The diagrams show from top to bottom the conversion from the STP to an STL with increasing resolution. The resolution should be selected depending on the complexity and size of the component. Here in the example, the two average resolutions would be sufficient for the printing of this component.