Tens'EGG'rity - Halloween - 3D Printed

Maybe a little decorative piece for the bookshelf at Halloween time!

Instead of a pumpkin ... I took an egg and built it into a tensegrity structure!

An egg (3D printed!) with sliced off top, connected by a thin thread … both parts keep a fixed distance to each other and give the whole object a stable structure. It is a fascinating experience when, after the 3D printing and the assembly of the individual parts, this tension is suddenly created when setting up the object: TENSEGRITY!

At first sight a bit confusing ... you have to look twice to understand the principle.

Dimensions: Ø 114mm, H approx. 160mm

• Nylon thread Ø 0,35 mm
• Stop angle
• Cutter knife
• Super glue
• Canning gum
• Sewing needle
• Sandpaper
• Some patience (when creating the tension structure)

There are 7 files to print:

• lowerring.stl
• upperring.stl
• stand_eggcupside.stl
• stand_egghatside
• egg.stl
• egghat.stl
• egginside.stl

Print Settings:

• Printer brand: Prusa
• Printer: I3 MK3S, Mini
• Supports: No
• Resolution: 0,2
• Infill: 20%
• Filament brand: Prusa; ICE
• Filament color: Galaxy Black; Wintershine White, Young Yellow
• Filament material: PLA

After you have printed the parts ...

Remark: As all parts are designed to fit very precisely, it may happen that you have to rework one or the other part a bit with sandpaper and/or cutter due to different dimensional accuracy of the printers and the different behavior of the filaments.

You need the following printed parts:

• egghat.stl
• stand-egghatside.stl

First attach "egghat.stl" to "stand-egghatside.stl" with some superglue.

To ensure a good fit, the fitting accuracy can be very tight. So it may be necessary to correct the fit with a cutter knife or sandpaper. This also applies for all other parts!

You need the following printed parts:

• lowerring.stl
• stand-egghatside.stl

Apply a little superglue to both parts and then press them together at right angles for 20-30 seconds.

For this step you need the following printed parts:

• upperring.stl
• stand_eggcupside.stl

Do the same here as before: apply a little superglue to both parts and then press them together at right angles for 20-30 seconds.

Let the two glued pieces rest for a bit before continuing! 

For the next step you need to add the following parts:

• egg.stl
• egginside.stl

I printed „egginside.stl“ in black and yellow, but decided to install the black version.

When the glued parts are absolutely firm, you can make the connection between the lower ring (egg hat) with a short nylon thread, Ø 0,35mm. Thread or dental floss will also do the job! The space between - measured lower edge egg hat and egg cup - should be min. 35 mm (max.40 mm).

Take a nylon thread of about 15-20 cm and make a multiple not at one end. Pull it through the hole of the egg hat, and then put it first through "egginside.stl", then "egg.stl" and then through the egg cup. Now again make a multiple knot. While doing this, you have to try out whether the distance between the two parts is correct when setting the knot. This is a bit fiddly! It took me several tries too!

If the distance is correct, you can cut the ends of the thread.

You need 3 nylon threads of about 35-40 cm.

At the top ring the you see 3 holes. The holes - at bottom ring too - are drawn in the designer with only Ø 1 mm. During printing the holes can sometimes be narrower. Therefore it may be necessary to pierce them with a needle or drill them out.

Take one thread and make a multiple knot at one end and then pull the thread through one hole of the top ring. Do the the same with the two other holes of the trop ring.

One difficulty with tensegrity projects is always the tightening of the threads. Unfortunately, simply tying a knot in the "right" place doesn't work. As I did in previous projects, I cut 3 small pieces out of a canning gum. These pieces will serve as an "adjuster". It makes setting the tension considerably easier!

I placed the top and bottom pieces so that I could pass the 3 threads through the "top" ring from the outside. I took the first thread, a sewing needle, inserted the thread through the eye and pierced one of the small rubber pieces from below, as shown in the pictures. To prevent the thread from slipping out too easily, I pierced the needle through the rubber again from above, not too close to the first stitch. Without thinking about the alignment at this moment, I did the same with the remaining 3 threads.

After all 3 threads had been prepared that way, I started aligning the threads. The small pieces of rubber can be moved. I started with it while the top and bottom were lying flat. When all 3 threads were almost evenly tightened, I have placed it upside down and made the fine "tuning".

In any case, do not adjust too tightly, as it will cause the stand parts to bend over time.

Now you can cut off the overhanging threads ... but not too short on the gum, so that corrections can be made later. The rubber pieces can be pressed into the recesses with the help of a small screwdriver.

Done!