Here are cat coasters 13 through 16 of the coasters based on the 17 plane groups. See Cat Coasters 01,02 and 03 - things 54736, 56813 and 58639.

The four plane groups are: p3, p31m, p3m1, and p6. All of these groups contain three fold rotation axes. p6 also has six fold rotation axes. P3 and P6 have only rotational symmetry while p3m1 and p31m contain combinations of reflection and glide lines. The four sets of files for dual extrusion are:

cat_coasters_p3.stl and cat_decorations_p3.stl cat_coasters_p31m.stl and cat_decorations_p31m.stl cat_coasters_p3m1.stl and cat_decorations_p3m1.stl cat_coasters_p6.stl and cat_decorations_p6.stl

Cat_coasters_04 scad created the stl files and the images are in coasters_dxf_04.zip

The coasters are 110 mm in diameter and should be constructed directly on the build surface. I used one shell and ten percent infill and the coasters printed in about two hours.

The coasters can be used as teaching aids. Pdf files that show some of the symmetry elements are included in coasters_dxf_04.zip. Reflection lines are shown in red and glide lines in blue.