Have you ever been sitting at home with nothing to do and plenty of time? Do you have cardboard, a box knife, and an animal you like? With this Intractable you can learn to make a 3D cardboard animal that holds itself together, specifically a puffer fish! If so this is the instructable for you!

Step 1: Brainstorming Ideas

First, I brainstormed all the animals I could make out of cardboard that would work well for this project. I thought about each animal in segments and how many parts each animal would require. I divided the list of animals I brainstormed into levels of difficulty. That helped me chose an easier animal since this was my first time making one of these 3D structures.

Next, I basically thought about the animal and what it would look like from a view head on and from a side view. I sketched each one out and considered how many layers the animal would consist of. I included details such as the tail, side fins and spikes all around the puffer fish. Finally I knew the fish needed an identity, so I sketched a face to help show the distinctive eyes and mouth of a puffer.

The photos above show my list, my front and side view sketch, and the facial feature sketch respectively.

Step 2: Supplies

What you'll need:

-Cardboard (A LOT!!)

-Pencil X-acto Knife (Fancii 16-PC Presicion craft knife kit)

https://www.amazon.com/Fancii-Precision-Craft-Kni...

-Cutting mat (self-healing non-slip cutting mat)

https://www.amazon.com/Fancii-Precision-Craft-Kni...

-Eraser

-Ruler/Straight edge

-Drawing compass

-Paper to Sketch ideas

-Camera for pictures (optional)

Step 3: Model Maquette

I wanted to first make a small version of my puffer fish to model it and test out how I would be able to attach each layer of the cardboard since this was my first time making the 3D model. I used cardboard to help me do this but kept it very simple. (See photo above.)

Step 4: Making the Shapes

Start with making one large circular cardboard shape that has spikes, a tail, and two fins on either side of the tail. Cut it out. (SHAPE #1) Now make a second cardboard shape by tracing your first shape exactly, and cut it out. (SHAPE #2) The slits you see cut into the shapes will come later in the process so disregard them at the moment. These two shapes will anchor the center of your 3-D puffer fish.

Now cut a third circular cardboard shape that has only spikes but is exactly the same size as the first two shapes. (SHAPE #3) This will be your anchor piece that the first two circular pieces attach to to form the center of the puffer fish. These three shapes can be seen in the first photo.

Continue cutting out circular cardboard shapes in pairs of two. Keep adding your spike design on each layer. On cardboard piece 7 add extra side fins that the puffer fish has that will add detail to your final construction.

Each set of two circular cardboard shapes will get progressively smaller as you go. You can see this in pair 4 and 5, then pair 6 and 7, and finally pair 8 and 9.

Step 5: Cutting to Attach

Find the center of each circular cardboard piece you have cut out.

Starting with the largest piece (#3 which is the same size as #1 and #2) you have to find the center of the piece and draw a diameter line across the center. Using that line you will measure from the absolute center dot on you diameter line the distance to the right and to the left that you would like your two base pieces (#1 and #2) to attach to piece #3 with equal spacing apart. Make one dot to the right of the center dot on the diameter line and make one dot to the left of the center dot on the diameter line. I used 1" to the right and 1" to the left from the center dot making the distance between the two points 2". Cut from each dot, perpendicularly down to the very edge of your circle. (Look at #3 for a representation of my directions.)

Repeat this process for circles #4-9. Customize the length of each perpendicular cut for the size of the circle you are cutting. See circle photos above.

Now, using piece #1 find the very center and make a dot. Draw a diameter line across the circular piece going through the center dot. Draw a line from the center dot perpendicular to the very edge. This will become a cut. Piece #3 will eventually go in this cut.

Using the center dot, you need to make 6 additional cuts where the six additional circles will fit. Three of those cuts will be to the right of the center dot/cut and the other three will be to the left of the center dot/cut. They will be equally spaced and each line cut will be the same length as the line cut on the piece sliding into the cut.

For example, measure the cut you made on piece #4. Mine is about 5.5". The line you should now cut onto piece #1 to the right of the center line, would measure 5.5" from the diameter line to the edge of your circle going perpendicular from the diameter and parallel to the center line you already cut.

Repeat this same process from piece #5 on the left side of the center most dot/line on shape #1.

Continue this process for shape #6. Repeat the steps above on the right side of the center most dot. Measure the cut you made on piece #6. Mine is about 4.75". The line you should now cut onto piece #1 to the right of the center line, would measure 4.75" from the diameter line to the edge of your circle going perpendicular from the diameter and parallel to the center line you already cut.

Repeat this same process from piece #6 on the left side of the center most dot/line on shape #7.

Cut your final pair of lines. Continue the above process for shape #8. Repeat the steps above on the right side of the center most dot. Measure the cut you made on piece #8. Mine is about 3.5". The line you should now cut onto piece #1 to the right of the center line, would measure 3.5" from the diameter line to the edge of your circle going perpendicular from the diameter and parallel to the center line you already cut.

Repeat this same process from piece #8 on the left side of the center most dot/line on shape #9.

Now your lines/cuts are complete on piece #1.

Make piece # 2 look identical to piece #1.

You now have all the cuts you will need to assemble your puffer fish.

Step 6: Assemble

Pick up pice #1 and #2. Match them up side by side with all cuts next to one another with the cuts facing up. Slide in piece #3 to the center cuts on pieces #1 and piece #2. Slide in pieces #4 and #5 into the next cuts closest to the center line cuts. Then slide in pieces #6 and #7 to the next cuts out. Finally slice in pieces #8 and #9 to the last cuts near the edge. Your should have the shape of a puffer fish assembled.

Step 7: Make a Base

In order for the puffer fish to stand and not crush it's spikes, I created a stand for it. I cut three "U" shaped cardboard pieces and three "H" shaped cardboard pieces that are roughly 2" x 1.5". (See photo.) Then I attached the 3 "U" shaped pieces to the three "H" shaped pieces. When you use them, the "H" shaped piece will be connected to the cardboard puffer fish and the cardboard "U" shaped piece. (See photo.) I found three stand pieces were enough to support the entire puffer fish.

Step 8: Make Face Details

To make the face details I measured the inside length between piece 1 and piece 2 to know my maximum width for the mouth. I then made a wavy rectangular shape about a cm smaller on each side for a small gap. I wanted to make it have some depth so I then cut a smaller version of the wavy rectangle so I could layer the two pieces. As for the eyes I traced the bottom of a glue stick to make a circle. I then cut those out and made that the eyes. To place the three total pieces on the face I took the front piece and put the mouth between piece 1 and piece 2. The eyes were placed towards the top of the front piece close to the bisecting cardboard.

Step 9: Display

To display the puffer fish you have to use the three bases (already connected) and place one piece towards the back of the tail. This side will have two of the base pieces. The side with only one base piece should have the piece more towards the back but also somewhat in between the pieces about 1/3 of the distance from the piece farthest back. The last piece should be on the side with two bases. The piece should be placed in front of the two other bases and about 2/3 of the space between the second piece and this one. This should help balance the puffer fish so it doesn't fall over. If it doesn't completely balance adjust the pieces on all sides until its an even balance. After this you have no more steps. You have completed the puffer fish and it looks great!! Nice job and I hope you come back soon for some more Instructables.