I am getting my first 3D-printer (a Prusa CORE One) this week! I have tons of ideas that I want to get started with, but the most time-sensitive one is to make some self-watering planters for my balcony (so I can have time to grow some greens in the season). I wanted to do this without a 3D-printer last year, but I could never find any cases close to the right dimensions in the stores, and making the separator between the water reservoir and soil from off-the-shelf parts was not so easy with the cases I did find, so I hope I am able to make something functioning with my 3D-printer this year.
But I'm new to this, and I am looking for some advice to where to get started reading up on different concepts that will be relevant to this project. These are the things I am planning to dive into over the next weeks, and I am sure there are plenty of things I have not thought about at all:
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Splitting and joining 3D-printed objects: The overall base area of the planter is too large for my 3D-printer to do in one go, and I am likely going to need four parts that I need to fuse together. I am thinking there are many "standard" ways of doing this, such as splitting with a jigsaw-puzzle pattern? I am also planning to simply glue to the parts together along the seam, and add an additional layer of glue along the boundary. Which leads to concerns about...
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Water tightness: I know that making watertight prints is not the easiest thing in the world. The container should be able to contain water without leakage, and I am planning on reading up on all the ways to make the prints themselves as impermeable to water as possible. I am sure there are much to learn in terms of slicer settings here. In addition, I will look into different coatings I can finish it up with, such as a layer of water-proof wood glue. However, the water here will be absorbed by the soil and then by the plant's roots, so this coating should be non-toxic.
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Material choice: To begin with, I will only have PLA available, but I can get other filaments if needed. There are two immediate concerns I have about this: whether it is food-safe (for the same reason as above) and whether it is suitable for outdoors use. It will not be in direct sunlight, as I will build a wooden case around these 3D-printed containers, but the planters themselves will be, so it could get a little hot during Summer. Any other considerations I need to make?
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Modelling the parts: I am already familiar with Blender, and planned on using it for the first project. I have FreeCAD installed, but zero experience. The shapes are simple, and I am sure I can draw up something in Blender in no time. But since I want to split them up, and join them ideally as flush as possible, will the models be precise enough? Dimensional precision is the main reason I've heard for using CAD-software over Blender for hobby basis.
ETA: Hm, how thick do you think the walls would have to be?
Oh, that could be a much better solution. How would you design the reservoir filling system in that case? It would be difficult accessing the rear reservoirs directly, but I could maybe make something with cheap PVC-pipes. Ideally I would fill it from only one point, and I eventually plan to have some sensors measuring the water level in the reservoir(s)
You can always mock some stuff up and try it out in PrusaSlicer to see how long it thinks it'll take?
Wall thickness potentially depends on the size of the object? I guess 2mm would the the starting point, fill one with soil, see how sturdy it feels. Complexity for 3D printing is "free", kinda. A lot of the best container designs incorporate ribs to strengthen them without using up too much material. Given that the joins are the weak part, you'd potentially want that a lot thicker.
You also want to look at "vase mode". Some of the fastest printing objects you can get on a 3D printer are where you design around the constraints of vase mode and then you can use a fat nozzle with thick layers to print really fast.
You can always print plumbing instead of using PVC pipes? I've definitely seen self-watering pots such that they just have a pipe incorporated into the design such that it just sticks up along the corner. So, worse case, each module has a watering port. If you want to get fancy, you could make a manifold such that a single pipe sticks up in the middle and fills 4 reservoirs, although the fancier the plumbing the more likely you are to have one of them get dried out faster unless your filling routine tops them off.