Monday, November 5, 2012

How to make a giant paper-mache egg

How to make a giant paper-mache egg

Step 1Make a solid model

As a first step, I used Autodesk Inventor to design a 3d model of an egg, by making a single curve, and then rotating the curve 360 degrees to form the egg shape. Then I exported it into an STL for modifications.

Step 2Use 123D Make

For the next step, I used Autodesk's 123D make, a free web app that can turn solid models into plans for either interlocking, or stacked slices. I set our material to 1/4 plywood, chose radial slices as my construction method, and hollowed out the interior of the form (so that there would be plenty of room for our rider). Then I exported the resulting vectors (complete with notches to fit together) as an .eps file.

Step 3Shopbot!

Next I pathed these vectors to be cut on a Shopbot CNC router at Techshop, using VCarve Pro as my CAM package. Then we took our file to the shopbot to cut out our "egg bones."

Step 4Assembly

After we had all our pieces, we carefully notched them together. Since the fits were surprisingly tight, and our material was fairly fragile, we had a little bit of cracking in some off the plywood pieces, which ended up working just fine, since we were planning to cut the egg in half anyway.

Step 5Crack the Egg

Next we used a jig saw to cut the egg jaggedly in half, taking advantage of the couple of points that had cracked in assembly. We lined the points were the two halves would come together with cardboard, so that the seam between the two halves would be finer. The picture shows the joint between the two halves after we had started to paper mache the egg.

Step 6Paper-Mache Time

Once we had the egg structure finished, we just had to cover the whole thing in paper mache. I stole a bag full of free newspapers from various spots around San Francisco, then layered it over the egg with a mixture of water, flour, and Titebond glue. Once the glue dries, we'll paint the whole thing white and be ready for our big day!

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