Water Bottle Connector - Recycled Building System

This Instructable will show you how to build structures out of empty disposable water bottles using 3D printed connectors. These structures could be used as inexpensive shelving or as play-forts for kids.

During the past year, I have been exploring and designing various building systems made of materials that would otherwise have been thrown away. My initial designs consisted of rolled up scrap paper and connectors made of popsicle sticks, which unfortunately had the tendency to crumple and snap. Recently, I realized that water bottles--which are plentiful and sturdy when air is sealed inside--are a perfect building material. The water bottle connector featured in this Instructable is the 5th version of my design and makes for surprisingly rigid structures.

This Instructable specifically shows you how to build a simple 1x1 cube that can hold up to 14 lbs of weight. As you save more water bottles and print more connectors, you can create more elaborate designs.

• Water bottles with 1/4 inch tall caps* (24 are required to make a cube)
• Transparent packing tape
• 3D printer
• PLA filament
• Small flat screwdriver

*The 3D printed connectors I designed only work with the thinner caps commonly found on cheaper water bottles (the ones I used came from Costco). The thicker Coke-style bottles won't work; however, the 3D models could be easily modified to accommodate this.

No glue is required for this project. The connectors are made of parts that snap together and the structures created from this system can be taken apart and reassembled.

Drying the water bottles:

The empty water bottles may contain some residual water inside. To dry them, open the water bottles and set them next to a sunny window for a day or two; the water will evaporate.

Removing the seal:

In order for the connectors to work, you must remove the thin plastic seal directly below the cap of the water bottle. To do so, use the small flat screwdriver to pry the seal off. Discard the seal, but keep the caps; they are very important.

Take two water bottles and tape them together at their bases, as shown in the picture. 1.5 to 2 wraps of tape around each bottle pair is sufficient. Press the tape securely against the plastic to make sure it has good contact.

To make a cube, you will need 8 connectors. On my printer, each connector takes about 2 hr & 30 min.

For each connector, you will need to 3D print:

• 2 slotted connector pieces
• 1 "X" shaped connector piece
• Approximately 3 cap placeholders*

*This varies depending on the number of bottles attached to the connector. For the cube we are making, each connector needs 3 cap placeholders.

These are the print settings I used:

• Printer: Monoprice Maker Ultimate
• Material: PLA
• Layer Height: 0.2 mm
• Shell Thickness: 0.8 mm
• Bottom/Top Thickness: 0.8 mm
• Fill Density: 50%
• Support Type: None
• Platform Adhesion Type: Raft

Keep in mind that these settings are just what I used. You should adjust them to fit your printer.

To assemble a connector, take one of the slotted pieces and slide the "X" piece inside its core, perpendicularly. Then, slide the second slotted piece into the core, perpendicular to the first piece in the other direction.

Repeat for each of the 8 connectors in the cube.

To insert a water bottle cap or cap placeholder* in the connector, choose a side of the connector and place the cap at an angle under the lips of two of the four connector prongs. Then, press down on the opposite end of the cap until it snaps into place. Don't worry if the cap looks slightly bent inside the prongs.

To build the cube, each connector will need 3 caps grouped around one corner of the connector and 3 cap placeholders grouped around the opposite corner.

*It is important that a cap or cap placeholder is in each of the 6 spots on the connector. Otherwise, the connector pieces will slide apart. You could put caps in each of the spots on the connector, but you will end up having a shortage of caps.

To build structures with the connectors and water bottle members, just twist the water bottles onto the caps in the connectors. It will usually make a click noise once it is seated properly. Make sure you grip the cap in the connector and not the connector itself. Otherwise the cap may not be screwed on completely and the bottle may disconnect.

For the cube, assemble the pieces as shown in the picture.

Be careful not to unscrew one end of the bottle member while you screw in the other end.

When you want to take apart the cube structure, just unscrew the water bottles from the connectors.

To build different structures, you will need to rearrange the positions of the caps and cap placeholders. To remove a cap, pry apart (slightly) two of the prongs that are holding in the cap and pop the cap out as shown in the picture.

The picture above shows the various versions my connector idea went through before it actually worked. Throughout the design process I worked with different ideas, trying to find the balance between functionality, quick 3D print time, and ease of assembly.

My favorite part about this project is how it takes water bottles, a material that is normally discarded in large quantities, and turns it into something fun and useful.

This is my first Instructable, so I am still learning how to write them well. If you have suggestions for how to improve this Instructable, please post them in the comments.