I wanted a planter for my apartment that would:

• Fit my small 3D printer
• Have enough volume to hold a medium sized plant
• Be able to be shoved right up to a window
• Stop my cat from making a huge mess

And so this is what I ended up with! It's a cube shaped planter, with built-in drainage, and a sliding lid that can be sized to a specific plant, to keep all the soil inside.

The planter can be printed without supports, and the built in drainage has been designed with bridging in mind. 

Print two of whatever lid works best for you, and they should be able to just slide on to the planter to protect the soil inside.

Printing instructions

Base:

• Print the base with 0.2mm layer height (or less) for the bridges to work. Take a look at your slicer preview to ensure the bridges generated correctly 
  • (In PrusaSlicer, if the layers exactly line up with the bridges, they will end up scrambled in a strange way. Just add/subtract a tiny amount from your first layer height if this happens)
• Try setting your slicer settings for good quality bridging (this can mean lower bridge speed, high fan speed on bridges, etc)
• To ensure it's water-tight, you can print with a slightly thicker line width to increase the squish between layers (You shouldn't need perfect water-tight layers for this, though)

Lids:

• Print the lids with the flat side down
• Test the fit after printing one lid, to ensure the fit is good. It doesn't need to be perfect, but the lid should slide on and stay on.
• If it's too tight/loose, you can adjust the x/y offset in your slicer to get it to fit right.

Known Issues

There are a couple of small issues with this model that I may fix eventually, but they don't affect its functionality (at least, in my experience) enough to prevent it from working as intended.

• The bridges are a little too large/difficult to print
  • I spent a long time making the bridges in this model easier to print, however some of them are still kinda long, and if any of the bridges fail, it can cause the bridges on the next layer to fail too.
  • My first test (with a 0.4mm nozzle) worked well, but the wood filament I had clogged my nozzle. Therefore, I switched to a 0.5mm nozzle, and my bridges came out pretty bad.
  • This could be fixed by just adding some more anchor points around the drainage holes
  • If your bridges don't work right, they can also just be ignored; A little bit of secret spaghetti in the hidden drainage area wont stop the planter from looking good and working correctly.
• The tolerance on the lid is just a bit too loose
  • I made the tolerances fairly loose on the lid, hoping that they would be easy to slide on, and expecting that the slanted shape would prevent them from coming detached. However, the slight flexibility of the flat lid makes it really easy for the lids to just pop on or off.
  • With my first print, the tolerance was just too large and the lid didn't really stay on at all. 
  • I adjusted the x/y offset for my second print, and that fixed it.
  • If I ever redesign the lid, I'll probably add a lip in addition to the sloped part, to really lock the two parts together.