Floating Pen Box - Tensegrity - 3D Printed

The thread in the middle of the two brackets - besides the four threads connecting the pen box and the base - builds the tension in this object. It's a bit magical how the physical conditions create a tension that makes this object a unit - a perfect unit. Tensegrity! At first sight a bit confusing ... you have to look twice to understand the principle.

Dimensions: container Ø 100mm, H 90mm, base 110x110mm, H above all 200mm

Material:

• Ø 0,35mm nylon thread
• Sewing needle
• Rubber canning ring
• super glue
• stop angle
• scissors
• sanding paper
• thin metal rod

Files to print:

• FDPB_base.stl
• FDPB_bottombracket.stl
• FDPB_container.stl
• FDPB_separator.stl
• FDPB_topbracket.stl

Print instructions:

• Printer brand: Prusa 
• Printer: I3 MK3S, Mini 
• Supports: No 
• Resolution: 0,2 
• Infill: 15% 
• Filament brand: Prusa; Geeetech 
• Filament color: Galaxy Black; Silky Silver

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.

For this first step you need:

• FDPB_base.stl
• FDPB_bottombracket.stl
• super glue
• stop angle

When inserting the bracket, make sure that the surface is level and that the ends of the bracket do not overlap on the ground side.

To ensure a good fit, the fitting accuracy can be very tight. It may be necessary to correct the fit with a cutter knife or sandpaper. Then apply superglue. For a correct alignment you should use a stop angle!

Wait a few minutes until the bracket is absolutely fixed!

For the next step you'll need:

• "FDPB_topbracket.stl" 
• the prepared base
• 1 nylon thread Ø 0,35mm, 20cm
• scissors
• thin metal rod

Take a nylon thread about 20cm long and make a multiple knot at one end and pull the thread from above through the hole in the middle of "FDPB_bottombracket".

Now take the thread and pull it through the hole of "FDPB_topbracket", side parts pointing upwards.

Making a knot in the right place here is not so easy.

To optimally position the bottom knot, it is helpful to tie the loop around a thin metal rod, then hold the outer thread and slide the metal rod to the desired distance of 30mm.

When the loop is well in place, pull out the metal rod and multiply the knot , so that it does not slip through the hole.

Now you need:

• "FDPB_container.stl"
• 4 nylon threads Ø 0,35mm, 30-35 cm
• scissors
• sewing needle
• pliers

There are 4 holes in the container bottom. I have constructed these holes in the designer with Ø 1mm. Depending on the printer and/or filament, these holes are more or less open. It is therefore useful to pierce these holes with a thin needle before continuing work. A pair of pliers can help.

Now you need 4 nylon threads of about 30-35 cm.

At the bottom side of the container you see the 4 little holes. Feed one of the four threads from the outside of the bottom into the container.

Then pull the thread out of the inside of the container until you can tie a multiple knot (be careful not to pull it all the way out!). Cut the short end of the thread behind the knot. Then you can pull out the thread on the bottom side until it is stopped by the knot.

Do the same with the other 3 holes.

For the assembly you need:

• all prepared parts
• Sewing needle (as thin as possible. However, the eye must be wide enough for the nylon thread to pass through)
• Rubber canning ring
• scissors
• ruler

First you should check if the 4 holes in the base are free. If not, you have to pierce the holes with a needle or with a Ø 1mm drill bit.

A big problem with tensegrity projects is always the tightening of the threads. Unfortunately, simply tying a knot in the "right" place doesn't work. Similar to previous projects, I cut 4 pieces of rubber from a preserving rubber ring. This time though longer, each about 12mm. Longer because then one more stitch can be made, making it more difficult to slip back. However, this also makes the adjustment somewhat more difficult. These pieces will serve as an "adjuster".

Put the parts in front of you, push "topbracket.stl" into the side recesses of the container. You can fix it with superglue. But it is not necessary. It holds by itself!

I placed the container and the base so that I could I could insert the 4 threads one after the other into the holes of the base. Then I took the first thread, a sewing needle, put the thread through the eye and pierced one of the rubber pieces from the bottom as shown in the pictures. To prevent the thread from slipping out too easily, I again pierced the needle through the rubber again from the top, not too close to the first piercing. The 3rd stitch through is then done from the bottom, not too close to the second one. Without worrying about adjustment at that moment, I did the same with the other 3 threads.

This is the most interesting part of the project! ... but adjusting the threads is always a little tricky

After all the threads are fitted with the "rubber adjuster", I began adjusting them. The little rubber pieces can be moved around. Due to the 3 stitches the shifting is a bit more difficult. I started doing this while the container and the base part were lying flat. When all 4 threads were almost evenly tightened, I raised the object upside down and started the "fine tuning".

The small rubber pieces find a place in the recesses at the bottom of the base.

It took me several tries to get a good alignment.

When the fine-tuning is finished, you can cut off the protruding threads. But not too short, so that a readjustment remains possible.

It is always a fascinating experience when, after assembling the individual parts, this tension suddenly is created when setting up the object: TENSEGRITY!

… just print

• FDPB_separator.stl

This insert is created to achieve a better distribution of the content inside the container. In addition, the content does not get so mixed up.

To give you an impression of how other color schemes make this "floating container" look, here are a few color variations.