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Water bottle to sippy cup converter cap
Water Bottle to Sippy Cup Bottle Topper
Project developed by [megandersen]
My Open Source Appropriate Technology project is a water bottle cap modified to turn any water bottle into a sippy cup. Sippy cups are helpful to young children as they serve as a kind of "training cup" when learning how to use a real glass. Sippy cups are helpful in that parents spend less time cleaning up spills and the baby practices drinking liquids at a faster pace than a bottle but not as fast as an open cup. Sippy cups are also helpful because they help the child develop motor skills and hand-eye coordination. Sippy cups can be purchased for $5 or more but they generally aren't available at all small, local stores. They're more likely to be found at big box stores like Walmart and Target. This is why it would be helpful to be able to print a sippy cup top that fits onto nearly any plastic water bottle. This also encourages reuse of plastic water bottles rather than throwing them away after a single use. Like the water bottle, the top can be easily rinsed out and cleaned to avoid build-up, especially with drinks other than water. This project is Appropriate because it follows the ideology of Appropriate Technology--designing a part in the simplest, most energy-efficient, and environmentally-friendly way possible on a small scale that benefits communities. This is the simplest version of this water bottle adapter that still achieves the intended purpose, and this technology fits in with the ideals of sustainable living.
It's important to use sippy cups properly--here is a link to do's and don'ts for sippy cups, so please read this before using the sippy cup top! 
Bill of Materials
The only materials required are PLA filament and a standard plastic water bottle, ideally one that has been recycled.
Here is the finished STL file: File:Finalsippycuptop.stl
CAD File (FreeCAD) of the top portion of the sippy cap -- this top part was later joined with a regular bottle cap using NetFabb. SippyCupDesignFreeCAD.FCStd
Link to NetFabb file: 
Tools needed for fabrication of the OSAT
Jellybox or similar RepRap 3-D printer
Skills and Knowledge Necessary to Make the OSAT
No special skills were necessary beyond a working knowledge of FreeCAD, NetFabb, Cura, and the basics of printing on a RepRap Jellybox printer.
Technical Specifications and Assembly Instructions
1. Download the .stl file and import into Cura. 2. Insert SD card into computer and then in Cura, select "Save to Removable Drive" in the lower right hand corner. 3. When Cura says the card can be ejected, hit "Eject" and switch the SD card back over to your 3D printer. 4. On the printer, select "Print from SD", select the file, and the print should start right away. 5. I recommend printing at 210 degrees Fahrenheit. I used a fan speed of 78% and 100% print speed and got a smooth product. These may need to be adjusted depending on your filament etc.
Assembly: When the bottle cap has finished printing, cut away the Build Plate Adhesion layer around the base (if you chose that setting in Cura). Take your recycled bottle, remove its original cap, and replace it with this one! Super simple! :)
Print Time: The print should take about an hour and a half.
Assembly Time: Under a minute if you include cutting away the brim!
Photos of finished part attached to water bottle:
Common Problems and Solutions
The only really tricky aspect was figuring out how to design the sippy cup top on such a small surface (a narrow bottle cap). It took time to figure out the measurements and then even more time to figure out a shape. I encountered various issues with my initial processes for designing the shape in Blender and SketchUp, so I recommend FreeCad for this type of project. It was helpful to turn to NetFabb for joining the top with the bottle cap on the bottom.
The estimated cost of the PLA is $0.22 USD, and the average price of a disposable plastic water bottle is $0.34 when purchased in a case. This brings the total cost to $0.56.
To the right is a link to a commercial equivalent sold for $6.99 on Amazon. 
Cost savings: 92% Dollar savings: $6.43
- web page: New Kids-Center, Five Things You Should Know When Introducing Sippy Cup. Available: http://www.newkidscenter.com/Sippy-Cup.html