Summary

This is a fancy decorative octahedron which can fit perfectly (and hide) in the spaces formed inside the interior of the Folding Cube by Emmett (https://www.thingiverse.com/thing:135836)

Print Settings

Printer Brand:

Creality

                                            <p class="detail-setting printer"><strong>Printer: </strong>                     <div><p>Ender 3</p></div></p>                                                                                <p class="detail-setting rafts"><strong>Rafts: </strong>                     <div><p>No</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>0.12</p></div></p>                                                                                <p class="detail-setting infill"><strong>Infill: </strong>                     <div><p>20%</p></div></p>                                                    <strong>Filament:</strong> Unknown/unbranded PETG                Black                    <br>                        <p class="detail-setting notes"><strong>Notes: </strong>                    </p><div><p>This is a bit of a test of bridging and overhangs, but it should print fine.</p></div>

How I Designed This

See SCAD files attached

            <div><p>The default dimension of emmett's Folding Cube results in an interior octahedron with 20mm sides.  There was a bit of trigonometry required, to work out the dimensions of the octahedron, which I represented in SCAD as a single polyhedron with 6 points - I visualised this as two stacked square-based pyramids, with a height of 10mm x sqrt(2).<br>The holes are formed using CSG difference operator - subtracting cylinders from the octahedron solid. There was a bit more trigonometry required to work out the rotation angles required for the cylinders  - I worked this out to be:</p><p>360 <em> atan(sqrt(2))/(pi</em>2)  ~=   54.73 degrees</p><p>The octahedron would end up on its pointed end without the final rotation to rest it onto one of the flat faces.  The angle there is just 180 - 54.73 degrees.</p></div>                <p class="detail-image"><img src="https://cdn.thingiverse.com/assets/0f/98/d0/36/c5/20200525_215048.jpg"></p>                <p class="detail-image"><img src="https://cdn.thingiverse.com/assets/44/cd/82/c0/6e/20200525_215202.jpg"></p>            <p class="detail-caption"><strong>Nestled inside the Folding Box (you can fold the Folding Box to hide this object!)</strong></p>

Hidden Gem for Folding Box