Save the Sparrows. 3D Printed Bird Feeder (Parametric)

World's sparrow day was just a couple weeks ago, on March the 20th. I know, it might seem like there's a day for everything nowadays, but this day in particular was created to bring awareness to the dwindling sparrow population. Here in Europe it has dropped by over 60% over the last 30 years. Climate change, invasive species, the inability to find a place to nest in out modern cities, contamination and lack of food are some of the reasons.

To try and make things change for the better, I devised a three part plan to help to save the sparrows and restore avian biodiversity, because, after all, biodiversity is one of the best indicators of the quality of the environment we live in. My plan will focus on providing shelter, food and water for these little birds.

In this instructable you'll learn how to easily create a bird feeder from an empty bottle of wine and some 3D printed parts. The files I provided are parametric, this means no matter what the diameter of your bottle is, you'll be able to adjust the model effortlessly, just by entering a couple parameters.

If you're not comfortable working with glass, you can also use a plastic bottle, acrylic tube or any other kind of tube. I've tested the files and they are guaranteed to work from 50 to 100 mm in diameter. I chose a wine bottle because it's a nice way of repurposing them. Also, my country is still in lockdown, so I'm working with the materials I have at the moment :P

1. 3D printer
2. Wine Bottle (Any 1 liter bottle will work, be it glass or plastic)
3. Glass Cutter
4. Threaded Rod (A diameter of 6 to 8mm is recommended)
5. 3x 20mm M3 Screws

WARNING: Cutting glass can be dangerous, always wear work gloves and goggles.

Having said that, you can proceed scoring the wine bottle. I don't expect anybody to have a fancy bottle cutter, neither do I, that's why I devised with simple bottle cutter with some scrap wood, some clamps and a 2$ glass cutter. A piece of wood is clamped at the base, this block serves as a stop, to keep the bottle from moving up and down.

To score the bottom, another piece of wood is clamped to the previous one, with the glass cutter clamped at half the bottle's diameter. The bottle is pressed against the base and the cutter, and is slowly rotated. A mark should appear around the bottle, indicating the scoring has been successful. To make the second cut, I used another clamp to place the glass cutter farther away, and repeated the operation.

Once the glass has been scored, I filled my sink with cold water, heated the scored areas and dunked the bottle into the water. It might take several attempts, but the bottle should be cut cleanly along the scoring lines. I sanded the edges with 100 grit sand paper while wearing thick gloves.

If you are using a plastic bottle you can just cut it so you end with a cylindrical shape. If you chose to use a length of acrylic tube or any other kind of tube you can skip this step entirely.

I used Fusion 360 to design my model, and introduced a set of variables that can be edited to change the final result. I could just have designed a single bird feeder, but my plan is to get people involved, that's why I made my 3D model parametric, so everybody can effortlessly edit it to suit their needs and produce bird feeders around the world.

Editing it is very simple, just open the .f3d file below, click "Change Parameters" under "Modify", a window like the one in the picture will pop up. There are some main parameters, and some extra ones to make your life easier. Follow this list and you'll be done in no time:

1. Internal_Diameter_Bottom: Here you must enter the internal diameter of the bottom section of the bottle, if you're using a thin plastic bottle, make this diameter is a couple of millimeters smaller to be on the safe side, since the edge on the bottle will rest on a "lip", created from this diameter.

2. External_Diameter_Bottom: Here you must enter the external diameter of the bottom section of your bottle. Glass bottles aren't perfectly round, so measure the maximum diameter and add some slack (+0.5-1mm should be fine) to avoid a fit too tight.
   

3. Internal_Diameter_Top: Some bottles aren't perfectly straight all the way, mine had a slight taper, so I included parameters for the top section as well to account for this. If your bottle is straight, simply type in the same diameters again. In this parameter, make sure to add some slack by subtracting ~1mm from the diameter you've chosen.

4. External_Diameter_Top: If your bottle has a taper or an irregular shape, enter here the external diameter of the top section, you don't have to worry about tolerances here. If your bottle is straight, use the same value you used on the second parameter.

5. Threaded_Rod_Diameter: The threaded rod holds everything together, I chose an 8mm threaded rod, but you can change this number around, I suggest you stay around 6mm. This parameter will change the diameter of the threads on the base and the holder.
   

6. Holes: Changing this parameter changes the number of holes at the base, I added this parameter in case you want to use a very small or very large diameter, so you can adjust the number of holes for a better distribution of the seeds. Six holes should be just fine for most cases.

Once all the parameters have been introduced, save each body as an .stl file, and use Fusion 360 or your slicer choice to slice and print each part. You can also check the 3D model at Fusion 360 hub

Once you've double checked your measurements and parameters you can start 3D printing, which might take a while, but assembling this bird feeder can be done in a couple minutes following these steps, just like in the .gif above.

1. Take your threaded rod and cut it to length, the exact length should be equal to the length of the section of the bottle plus 35mm, this will ensure the rod will protrude from the top.

2. Attach the rail to the base of the feeder using 3x M3 screws, I used tapered screws for a flush finish.You can thread the holes first, but it's not really necessary.

3. Screw the threaded rod into the hole on the base, it should fit snugly.

4. Insert the section of the bottle or tube into the base.

5. Fill the feeder with seeds.

6. Put the roof on and screw the holder, this will secure the entire assembly.

Your feeder is ready to hang. Tie a rope through the hole on the holder. Make sure you hang the feeder high enough to avoid predators. Keep it away from noisy or transited areas and be mindful of opportunistic critters like squirrels, who might want some of that food too. Sparrows might not be willing to climb on it at first, so I decided to put it on a ledge to get them used to it. They like it so much I have to fill it every week.

On a final note, PLA isn't the best filament for outdoor use, if you decide to use it anyway, placing the feeder under the shadow of a tree will make the feeder last longer. You can always print a new part.

I hope you liked this instructable and I inspired you to help bring the sparrow back into our towns and cities.
Please consider casting your vote for the 3D printed contest, there are many awesome entries. Thank you for your time!