Introduction: 3D Printed Theo Jansen Strandbeest

Being convinced that 3D printing will eventually lead to an industrial revolution, I've tried to stay up to date with 3D printing and, as a Computer Science major, the CAD software used to create printable objects.

Recently, the cost and quality of 3D printing has become reasonable and CAD software has become easier to use, allowing anyone interested and motivated to design and print 3D objects.

I was surprised when I saw a functional version of Theo Jansen's Strandbeest a few months ago on Shapeways, because I thought all 3d prints were fragile and would crumble if you tried to make something with that many moving parts. I wanted to try to make one myself, so I downloaded the student version of Autodesk Inventor during winter break and got to work on what would become my first 3D Print.

This instructable details the steps I took to make one of Theo Jansen's Strandbeest using a 3d printer. The finished design was printed fully assembled. The full scale .stl file can be downloaded here, the .77 scale here, and the .66 scale here.

Step 1: Sketching the Parts

Strandbeests have a large number of parts, but there are only 8 unique parts that you'll need to make that will be copied over and over again.

Using the Theo Jansen's proportions, make an outline of each of the 8 parts using millimeter scale.

I used a minimum width of 2mm in the outlines, and a 7mm outer diameter for where the hinges will go.

If you are using Autodesk Inventor, John Helfen (Autodesk Student Expert Program Manager) does a great job of demonstrating how to start sketching in his videos here.

Step 2: Modeling the Parts

Using the outlines made in the last step, create the parts.

Be sure to make hinges with clearances that will work with your 3d printer/material. I left a .5mm clearance around all moving parts.

I used a fillet on the inside contact area of the hinge so that if the parts did fuse, only a small part of the pieces would stick together and could be worked free. 

John Helfen's videos on modeling parts here.

I've included the finished parts below.

Step 3: Assemble the Parts Into a Sub-assembly

Take the parts created in the last step and assemble them into a sub assembly of the strandbeest as shown in the first picture.

Be sure that there is at least  .5mm clearance between all moving parts.

Here's a video of the process.

Also, John Helfen's videos on assembling parts are available here.

Step 4: Mirror the Sub-assembly to Finish the Strandbeest

Copy the sub-assembly twice then add the middle part to get half of the final model.

Align the blue parts in the third picture so that they are at a 60 degree offset from each other.

Now mirror the entire structure to get the final model.

Step 5: Print

My University is in between 3D printers at the moment so I used for my print. Their white, strong, and flexible nylon material is great for moving parts.

Export an .stl file from your 3d software. I scaled my .stl down to 77% scale when exporting to print because full scale would have cost $116 to print, I knew I was running the risk of having the parts fuse together because all of my clearances were below .5mm but I took the chance because 77% scale only cost $54 to print. 

Some of the hinges were fused when I received the print so I carefully worked each of them until they began to move. The hinges eventually became smooth with use. I printed a test sub-assembly at 2/3 scale and the joints also functioned well after use, at this scale, a full print  would cost $35.

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