OSAT is technology that can be used to help advance third-world countries, but in ways that makes the most sense to those areas. For starters, the type of technology is best when is relatively sustainable. Furthermore, it is also extremely helpful when the technology runs off of parts and materials that can be developed locally and does not require large purchases. These things help prevent an area from becoming self-sustainable. 3D printers are working to be a huge contribution to OSAT. Some printers, like the JellyBox, have open source designs and can use open source files to print very useful objects. This project was my design of one the objects that can be printed. In particular, I decided to design a protractor with a spirit level. First, this will be useful in education, where protractors can be used to help teach geometric concepts. Additionally, they can be used in construction to make sure angle measurements are made accurately. Both of these purposes could be quite useful to a growing country.

Bill of Materials[edit | edit source]

  1. At least 13 grams of PLA filament - $0.20
  2. 1 clear straw - $0.05
  3. A small amount of rubbing alcohol - $0.10
  4. 2 pieces of gum or anything else that can seal the ends of a straw $0.15
  5. The following files - FREE
    1. OpenSCAD file if you would like to change the width of the spirit level's straw: File:Protractor.scad
    2. STL file for printing the default size

Tools needed[edit | edit source]

  1. Jellybox or similar RepRap 3-D printer
  2. Access to everything on the Bill of Materials
  3. Some kind of 'snippers' that can cut through a straw or other thin plastic.
  4. A rolled-up piece of paper that can be used as a funnel

Skills and knowledge needed[edit | edit source]

  • The default model perfectly fits the straw from a Silk Almond milk box, which is about 2 mm smaller than the average straw. To change the radius of the straw holder, you must change the value of the variable 'levelradius' in the .scad file. You must then export this into a new .stl file.

Technical Specifications and Assembly Instructions[edit | edit source]

  1. Print the .stl file. This should take about 2 hours and 45 minutes.
  2. Use the 'snippers' to cut off the circles at the corners of the protractor.
  3. Fit a straw through both ends of the straw holder.
  4. Use the 'snippers' to cut the straw even with the outside edges of the holders.
  5. Use 1 piece of gum or other sealing material to seal one end of the straw.
  6. Use a piece of paper as a funnel to pour rubbing alcohol into the open end of the straw. Do not completely fill the straw. Leave roughly an eighth of the straw's volume unfilled.
  7. Assembly should take roughly 10 minutes.
  8. Protractorlevel.jpg

Common Problems and Solutions[edit | edit source]

  • If the straw holder is not a good fit for your straw, adjust it in the .scad file using the instructions given in the 'Skills and Knowledge' section.

Cost savings[edit | edit source]

  1. The total estimated cost of this protractor is $0.50
  2. Commercial equivalents sell protractors and spirit levels separately, for a total of about $7.50 on the cheap end.
  3. Printing one of my protractor/spirit levels saves about $7, which yields about 93.3% savings.

References[edit | edit source]

  • The following page was the inspiration/motivation for this project:



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