Calottes

Two files belong to each calotte, in one file the carbon atoms are represented (e.g. methane-c-half.stl) and in the other the hydrogen atoms (e.g.methane-h-half.stl). In the slicer, the models are assigned to different filaments to get a two-colour print. After having been assigned to the two extruders, the two files are merged. This creates a joined model of the respective molecule.

There are two model variants. In variant 1, the model consists of one half. You therefore need two 6printouts to produce the entire model. Variant 2 contains the complete model, i.e. top and bottom. These must be printed separately, as follows:

The model is duplicated and exactly half of each part is lowered into the printing table in the Z-direction. Before that, one of the two models is rotated by 180°. The print should only include the outer walls, no infill. This ensures that two half-shells are printed. These are glued together after printing. In order to be able to do this accurately, one or two spacers are glued into one half, which serve as a centering aid for the final joining of the two halves. Print without adhesion. The tetrahedrons and spacers do not require any special print settings.

The optimal print settings are highly dependent on the slicer used. We usually use Ultimaker Cura. Six settings in Cura have proven to be favourable, sometimes in combination: (1) Adaptive Layer Height ensures accelerated printing in the areas of the object where details are not important. (2) Make Printable ensures that support is usually not needed because overhangs are “bevelled”. (3) Use Brim to ensure that the print adheres well to the print bed. Brim can be easily removed later. (4) Initial bottom layer a maximum of two or three layers so that the object has a flat surface and warping does not occur. (5) Maximum two or three wall layers to save material. (6) Infill maximum 15%, but six to seven top layers. If printing is done with support structures, other settings are usually required.

For this print, the parameters must be adjusted as follows when printing the calottes:
Options (1), (2), (3) should not be activated. (4) should be set to 0. (5) should be set to 3 for the C atoms and 2 for the H atoms. (6) should be set to 0. With these changed settings, the two halves of the calottes are printed hollow. This is helpful because they can then be glued together neatly with the help of the spacer. The usual settings apply for the tetrahedron and the spacer. The STL files contain the individual elements of the domes, each in halves. The 3mf files contain the complete partial model, i.e. C and H atoms.