3D Printing a Cactus

When I was eight years old, I was a big fan of cacti. And, not just any cacti, only the quintessential desert cactus: the saguaro.

When my family went on vacation to Saguaro National Park (yes, it’s actually a thing) one year, I saw huge valleys filled with thousands of these things — some of which were over 400 years old!

Anyway, I thought these things were pretty cool and after making a big enough deal about them, my mom got me a light shaped like a cactus.

I treasured this thing like no other. It was absolutely perfect from the texture of the material to the shape of the arms.

Eventually I started wondering, how was such an awesome thing made?

Cacti are pretty irregularly shaped, so someone (or something) must have spent some time chopping away at a block of plastic until the saguaro shape was revealed.

A lot of plastic was probably wasted in the process. In fact, there is probably less material in the actual light as was wasted making it.

And this doesn’t just apply to my (otherwise perfect) cactus light. So many of the things that we make nowadays involve a disproportionate amount of material.

This is crazy when you think about it: humans are pretty efficient at doing so many things, yet we still require much more material to make something than actually ends up in the object.

This method of producing an object is called subtractive manufacturing. It has to do with taking a block of something and getting rid of everything that is not the object we want.

Extremely wasteful.

And it makes you think, well wouldn’t it be more intuitive to just add everything that is the object?

Well, we can with 3D printing.

3D printing is a kind of additive manufacturing, which means that in order to create something, it slices the object into many different cross sections and prints these layers one on top of the other.

So, in the spirit of this elevated efficiency, I’m going to design a replica of my cactus light which can be 3D printed.

To design the cacti light, 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.

However, they don’t have a perfect cactus just waiting around ready to go. So, we’ll have to make it ourselves!

How?

Using segmentation — i.e breaking the larger cactus up into smaller shapes and then putting them all together.

Step 1: The body of the cactus

A saguaro’s body is cylindrical in shape and comes to a curve at the top. To do this, I used a cylinder with radius 12 mm and height 32 mm.

I then added a hemisphere (half of a sphere) with the same radius as the cylinder and a height of 16 mm and placed it on top of the 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.

Step 2: The arms of the cactus

A saguaro’s defining characteristic are it’s arms. They have a round top, but taper down closer to the bottom.

For the top, I used a hemisphere with radius 6mm. To get the tapering shape, I used a paraboloid with the same radius and height of 12 mm. I then put the hemisphere on top of the paraboloid, grouped them and duplicated the object to get the second arm.

I rotated each arm by 45 degrees (one clockwise and one counterclockwise) and merged them into the body of the cactus with one arm being slightly higher up than the other arm.

Step 3: The base

The base is kind of like a tapered cylinder — in other words, a cone with the top cut off. So, I made a cone with a radius 24 mm and a height of 60 mm.

I then duplicated this cone and made the duplicate a hole. 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.

I merged the hole about 27 mm up the original cone and grouped the two which gave the appearance that the top of the first cylinder was cut off.

I then rotated it so the larger face was facing upwards.

Then, I added the rim by

• duplicating the base
• increasing the duplicate’s radius by 2 mm
• cutting the bottom off using the same method as before
• cutting a hole into the center with the same radius as the base.

I then put this around the top of the base so that it’s top was 2mm off the top of the base.

Step 4: Putting it all together

I then took the cactus (with its arms), put it on the base and grouped everything.

And there you go: a little cactus figurine nearly as perfect as my own (only produced with much less waste).

So, yes… an eight year old’s cactus light is a pretty arbitrary example of something which can be 3D printed. However, the fact remains that 3D printing can be used to make some pretty cool things much more efficiently than how we currently make them.