3D printing is a revolutionary technology, however, there are some issues with it.

FFF or fused filament manufacturing is the most common 3D printing technology makers like me use, it works by melting a thermoplastic and adding it layer by layer to create an object, most filaments can be easily recycled since there just virgin plastic and pigment so along as there kept separated and clean they can be recycled either at a factory or at home with something like the preciousplastic extruder machine.

However when it comes to filament spools its a different story, most spools are made of a mix of plastics which makes it hard to recycle or even worst a thermosetting plastic that cant be re-melted or recycled.

Whats a thermoplastic and a thermosetting plastic

Thermoplastics are plastics that can be melted again and again with no issue, when you think of thermoplastic think of hot glue gun silicone, this is melted at a factory and when you get it you can re-melt it to glue whatever you wish and if you want to you could even heat it up again and use it with no issue as long as you don't exceed the recommended temperature.

Thermosetting plastics or polymers are polymers that once hardened they can't go back to its original state, most common examples of thermosetting plastics are resins.

in a nutshell thermoplastics can be reshaped while thermosetting plastics cant.

So the issue with this is that recycling spools is really hard and if you use your 3D printer often you can and probably already have many spools left over, so to fix this issue I designed a space-effective, cheap and quick way to repurpose the spools, by capping one end with a 3D printed part, putting some soil in them and hanging them to save space you can have a farm with minimal to no effort and very cheap.

Supplies

To make this project you'll need :

A 3D printer and the .stl files provided in this instructable.
Standard 1kg spools
Some string.
hot glue or 2 part epoxy glue (t2 part epoxy is a thermosetting polymer)
Dirt.
Plant/s or seed/s

Step 1: Step 1: 3D Print

To begin this project you'll need to 3D print the spool caps.

I've included 2 files, one with a draining hole and one without, if you wish to save some water use the one with the hole for every planter but the one on the bottom, this way the top planter will share the water with the bottom until it reaches the end.

I printed the caps using 3 perimeters, 3 top/bottom layers, 10% infill and PETG although PLA can work too just bear in mind it won't be as durable, 1 year tops.

The spool caps have a 54mm diameter, so if you filament spool has a hole of that size this will work great (most 1kg spools have a 54mm hole).

Step 2: Step 2: Assembly

Once you have the parts you need you'll have to glue them to the spools, this can sometimes be tricky due to the material the spools are made of, cyanoacrylate (superglue) won't work so you'll have to use hot glue or 2 part epoxy glue, visit the link to get a better idea of the glue I'm talking about.

Before you glue the caps and assemble the planter you might want to remove any stickers and/or wash the spools, this is not necessary along as you have a clean surface to glue the caps.

I printed 4 caps with holes and 1 without.

Step 3: Step 3: Gluing the Caps

I'm using 2 part epoxy glue because it's my favorite glue, it holds great and it dries in a matter of minutes.

Apply glue to the inside lip of the caps, then place it on the spool hole and finally press for as long as the glue requires you to do so, for 2 part epoxy glue its around 5 minutes.

TIP: place something heavy on top of the caps to hold them and free your hands.

Step 4: Step 4: Threading the Strings

Once all your caps are glued you can hang them by threading a 40cm string through the filament holes on the side of the spool, most spools have 4 pairs of holes 90 degrees apart, if yours don't have 4 pairs of holes you can still use it, just make sure the planter is well leveled.

TIP: you can change the length of the string to fit what you need.

For the top planter tie all strings into one, this will make hanging the planters much easier, however how you hang them is up to you and your specific situation. For the rest of the planters use the holes on the bottom part of the spool above to fix them to the one below, see the picture to get a better idea.

TIP: to make sure all your string are the same size you can set the spool on a flat surface, bunch the strings into one and cut just below where you're grabbing. It's ok If some levels of your planter are uneven, the large area around the center makes the spools self-level.

TIP: transparent spools such as the ones from polymaker are great for plants that like sunlight on the roots such as orchids.

Once you've threaded all strings you're ready to hang the planter, depending on your situation it might be easier to fill the pods once it's hanging, in my situation this didn't matter so I filled them in the next step.

When you hang the planter make sure you're safe, use a ladder and make sure its set on a steady nonslippery surface.

Step 5: Step 5: Planting

When it comes to planting there are many ways to do it, you can use pre-mixed soil, garden soil, you can grow your own seeds, store seeds or even store-bought plants, that's up to you.

TIP: go to a home depot and check the garden/plants section

For my planter I used pre-mixed soil, you can buy it in home depot and any kind should work but just to be sure ask the person that sells it.

I planted succulents and some chili seeds on my planter.

Planting something is just a matter of adding soil, the plant/seeds and watering from the top.