3D Designing A Modular NFT Hydroponics Unit
Hydroponics — the poster child of the urban farming movement — is based on the idea of growing plants without soil, but by suspending their roots in nutrient solutions.
Producing food this way requires 95% less water, chemicals and pesticides and than a land based farm and is 2–4 x more space efficient. Not to mention, the fact that it is designed for growing food indoors and in cities means that if you live in areas with deathly cold winters, you can basically get fresh produce from your own living room all year round. This in turn has even more ripple effects in terms of supporting your local economy, reducing transportation emissions and decreasing material waste.
All in all, hydroponics holds great potential for feeding our growing cities in the coming decades. It’s not a one size fits all replacement for land based farming, but for some circumstances it just makes more sense.
But, here’s what doesn’t make sense… trying to BUILD one of these systems (trust me, I’ve tried).
The most popular kind of hydroponic system is called Nutrient Film Technique (NFT). It works by
- Connecting of a network of troughs, usually made out of pvc piping
- Putting holes along them for plant baskets (little perforated cartridges which plants grow in so that their roots can hang out the bottom)
- Filling a vat with water and a blend of nutrients and placing it at the bottom of the system
- Putting a pump in this vat (kind of like one that goes in a fish tank) and running it’s cable up to the top of the system.
In this way when the pump is turned on
- nutrients will be pumped from the vat to the opening in the top
- flow through the troughs where the roots can get at them
- and spill out the bottom to the vat once more
Last summer whilst I was on a farming tear, I told my Dad we were going to assemble one of these systems. So, we drove to home depot and got several feet of pvc piping, elbow connections, plant baskets, nutrients and a pump. Basically, everything you needed to make one of these systems.
My dad, who was a woodworker in his distant past, had the clamps and drills and lubricant necessary to cut and paste all these things together. So I thought I could do this without all the blood, sweat and tears.
I would just cut the pvc piping into 5 foot troughs, drill 2 inch wide holes along them every 6 inches and cement the elbow and T connections between them.
Anyway, I set to work cutting and drilling, and after that first hour, I managed to make one hole.
Just one hole.
And for the rest of the summer, the materials just sat in our shed and I haven’t touched them since.
Not a story about resilience.
Anyway, I am definitely not the handiest person ever to walk the planet, so there are plenty of people much more talented than myself who have tried and succeeded at making such systems.
But, here’s the thing. Not many people who live in apartment buildings in cities are wicked craftspeople in disguise. Not to mention, most people probably don’t have the tools and clamps and drills necessary for making one of these systems just lying around.
While hydroponics is designed to be used by cities and the people who live in them, they are not totally meant to be made by them.
Which is a pretty big limitation, if you ask me.
3D printing is a kind of additive manufacturing which has to do with creating an object by slicing it into many cross sections and printing them one on top of the other.
If we applied this to making hydroponics systems, instead of spending countless hours trying to hack away at plastic pipes so that you can have fresh lettuce all year round, you can literally just get a printer to extrude it from the ground up.
Sounds much simpler.
But, let’s say you — the opportunistic urban farmer — decide to fill your living room wall with 10 foot long NFT contraption. A couple months later, you realize it’d be better off in another location. Only, in this spot you don’t have enough room for 10 ft of plants, but you do have enough space to add more vertical levels.
Well, basically, your current system is not compatible. But since everything is printed in one big piece, you either have to bust out all the tools you don’t have to rejig everything or start from scratch.
But, what if we 3D printed a modular hydroponics unit? Like perhaps a 15 cm trough that could be fit together with other 15 cm troughs to make things as wide or as tall as you want?
That way, if you needed to make any changes whatsoever, you just take the individual modules apart and put them back together again differently.
So, basically, you don’t have to start from square one every time you decide you don’t have enough lettuce.
In this article, we’re going to go over my design for a modular 3D printed NFT hydroponics system.
The system will be comprised of a bunch of modular cylinders, with a diameter of 10 cm, a length of 15 cm and space for one plant trough measuring 5 cm.
To design the hydroponics module, I used a program called TinkerCAD which is a free online CAD (computer assisted design) platform which you can use to design 3D printable objects.
TinkerCAD has a library with a bunch of different shapes, numbers and letters which you can use to build basically anything. We’ll use a technique called segmentation — i.e breaking the module up into smaller shapes and then putting them all together.
Step 1: The Tube
The trough that the plants will grow in is going to be 150 mm long, have an external diameter of 100 mm and a material thickness of 5mm.
To do this, we are going to
- construct a cylinder with diameter 100 mm and length of 150 mm
- duplicate this cylinder and decrease it’s diameter to 90 mm
- make it a hole (by clicking the icon in the top right corner)
A hole is essentially negative space, so whenever it is merged with another object, it will make a hole of that shape in the object. Kind of like how when you walk through a snowbank, your boot makes a hole which is shaped like your foot in the snow.
We’ll then merge this hole cylinder into the middle of the original cylinder.
Now, these two shapes are independent and since we want them to be one collective shape, we’ll select both of them and press the group function. This basically sticks them together so if you move one, you move the other.
We’ll then use the rotate tool (the little arrow around the selected shape) to rotate the object laterally by 90 degrees so that it’s resting on the curved surface.
Step 2: The Plant Bed
A typical plant basket has a 2.5 cm radius, and so we want the hole that this basket rests in to be equivalent.
To do this, we’ll
- Make a cylinder
- Make it’s diameter 50 mm and give it a height of 35 mm
- Make it a hole
- Use the elevation tool (the upward arrow above the selected shape) to raise it by 65 mm
- Move it into the center of the tube cylinder so that there are 50 mm between it and either edge of the tube cylinder. That circular face of the hole should come flush with the curvature of the larger tube cylinder.
And of course, group everything!
Step 3: The Screws
So in order to make this module modular, it needs to become a tessellation (if you put a bunch of them together, they fit perfectly and don’t leave any gaps).
This means that we can pretend that one end of the tube is going to be screwing in to the other end of the tube. But, at the moment, both ends are the same size, so one can’t physically fit one into the other one.
To fix this, we’ll add an extension to one end with the same exterior diameter as the interior diameter of the large tube (90 mm) and the same material thickness.
To do this, we’ll
- Take a cylinder and give it a height of 20 mm and diameter of 90 mm.
- Duplicate it and shrink it’s diameter down to 80 mm
- Make it a hole and merge it into the middle of the original cylinder.
- And… group the two!
We can then rotate by it laterally by 90 degrees and merge it 5 mm into one end of the larger tube.
So, now we can put these two different ends together just fine, but there’s nothing to hold them in place. They can simply come apart with a little lateral force.
So, to fix this, we’re going to introduce some torque — i.e. rotational force. Because of the angle with which this force is applied, it’s harder to counter act with gravity.
And what better way to do this than with a screw.
Now, making a screw is pretty challenging. Luckily, TinkerCAD has a communal repository of random shapes that wonderfully talented people have put together, one of which has made a screw.
In order to change the screw parameters, each shape has a handy drop down menu where you can just fill in whatever dimensions you want.
So, we are going to make the interior radius of the screw 18 and the exterior radius of the screw 20. We will make the inner thread height and outer thread height 1 and 2 mm, respectively. We’ll also give the screw two “turns” — or make it wrap around twice.
We will give the exterior screw a diameter of 100 mm and a height of 10 mm. We’ll then duplicate this screw and change it’s diameter to 90 mm for the interior screw.
The exterior screw will go 4 mm off the end of the extension, and the interior screw will go 6 mm off the other end.
And, finally. Group everything.
And there you have it, one modular hydroponics unit. Combined with a bunch of other identical ones, you could basically make a full NFT system that’s customizable to whatever configuration you’d like.
The only things that are missing are elbow joints as well as solid connections to make multiple troughs and multiple levels. These are pretty easy to obtain using pvc piping, but more on that to come… :).
