Summary

These bowls are actually working as a pair of gears.

They look like bevel gear wheels, but technically, they are straight spur gears. They work perfectly well when sitting flat on the table.
This was done by varying the profile shift (addendum modification) of the involute from negative to positive along the Z-Axis.

The mechanical engineering part of this is quite complex, but nevertheless, these are some useful bowls for your sweets.

Print Settings

Printer:

Tronxy xy100 STARTT Prusa i3

                                            <p class="detail-setting rafts"><strong>Rafts: </strong>                     <div><p>Doesn't Matter</p></div></p>                                                                                <p class="detail-setting supports"><strong>Supports: </strong>                     <div><p>No</p></div></p>                                                                                <p class="detail-setting resolution"><strong>Resolution: </strong>                     <div><p>0.2mm</p></div></p>                                                                                <p class="detail-setting infill"><strong>Infill: </strong>                     <div><p>none</p></div></p>                                                        <br>                        <p class="detail-setting notes"><strong>Notes: </strong>                    </p><div><p>made with cura 2.1.99</p><ul><li>bottom 1.6mm</li><li>wall lines 3 (x 0.4mm)</li><li>spiralize outer contour</li></ul></div>

How I Designed This

Done with the involute gear feature found in FreeCAD's Gear workbench.

Geared-Bowls