This project was built for the 2008 Roboexotica conference in Vienna, Austria where it tied for first place in the drink serving category. Here's how it was made!
Step 1: Story
Our delicious fresh fairies are hand-captured from only the finest wormwood forests of Northern Europe. We take extreme pride in offering only the finest quality fairy juice available. While it may seem inhumane on the surface, any fairy connoisseur will tell you that only sheer terror can unlock the full aroma and flavor to be enjoyed by the drinker.
Our juicer was built from a rare 19th century umbrella cabinet for an authentic look that cannot be matched by this era's artisans. We chose this specific cabinet due to the convenient fact that it is made from wormwood which keeps fairies comfortable as they inhabit our holding tank. While the cabinet is late 19th century vintage, our juicing mechanism is designed using the latest technologies available. The transparent facade was chosen to guarantee that we are not using bottled fairy juice, yet it is frosted so as not to reveal the less appetizing realities of fresh fairy juice.
Step 2: The Illusion
As you approach the machine you hear a high pitch fairy voice saying things like "Where am I?" and "This is boring...boring, boring, boring." You also see a small green point of light flying around in 3 dimensional space behind a pane of frosted acrylic. You reach your right hand up and crank the wheel which actuates a mechanism inside the cabinet closing the walls in on the flying fairy. As the walls collapse the fairy gets anxious and says things like "The walls are getting closer" and "I don't like this." Finally the walls meet and the fairy screams before you hear a squish and the sounds of a pump pushing your fresh fairy juice into a small glass at the bottom of the case.
Step 3: Case Design
After some quick sketching to determine form factor, I jumped into CAD to whip up a quick assembly. It was good to get all the parts represented and oriented to help determine size. One of the main limiting factors on size was fitting it into a suitcase so that we could bring it to Austria.
DXF outlines of all the parts were necessary for cutting on the awesome Epilog lasercutter at Instructables. Once all the outlines and joinery were determined I went into a vector illustration program and drew up the badge and inlay flourishes to make it look more art nouveau and fancy. The badge was raster etched into the surface with the laser. The simulated inlay was achieved using two layers of wood. The outer layer I vector cut the outlines of the relief all the way through, and the inner layer is solid. It creates a great effect and could be even cooler with more layers.
Step 4: Lasercutting Tips
This project would have taken a lot longer and not come out nearly as good if i didn't have access to the Epilog laser. I learned that when cutting wood it helps to use masking tape to keep the surface of the wood near the cut from getting smoky and burnt. Also, you avoid cutting plywood with the lasercutter. The glue that bonds the plywood layers will smoke up and fog the optics of the laser which drastically reduces its effectiveness. Its also a good idea to do test cuts on cardboard before putting any valuable materials in the lasercutter.
Step 5: How It Works
The fairy is a 180degree green LED with small clear fairy wings super glued to it. It's suspended from the top compartment of the case by a servo arm attached to the same flexible small gauge wire that powers the LED. The servo has a pseudo random sweeping pattern that makes the fairy bob up and down. At the bottom of the case there are 4 holes cut for 80mm computer case fans. The fans blow air up into the fairy compartment and since the fairy has wings it catches the wind and swings around in a random pattern in XY space. The servo plus the fans make for a pretty realistic flying pattern.
The Juicing Mechanism:
The crank on the outside of the case is attached to a wheel on the inside of the case that has small magnets on it. When you spin the wheel the magnets pass by a hall effect sensor which sends a signal to our Make Controller board. The make controller then sends power to our two opposed DC gear motors that are coupled to some all-thread rods. The fairy squishing walls are mounted on drawer guides for smooth action and the all-thread passes through a nut on the wall to actuate it inwards and outwards. There are limit switches mounted on the drawer guides as stops to keep it from over extending or retracting. The inside limit switches also signal that the walls are closed and trigger the fairy death sequence. Finally, we have a tunable peristaltic pump attached to the back of the machine that pumps and mixes ice cold sugar water with the absinthe.
Electronics and Software:
We used a Make controller board for doing the in and out which talks over OSC to a laptop running Max/MSP. This is totally overkill, but my partner David wanted to learn Max and it seemed like a good way to get started. The electronics are all off the shelf basic stuff. Here is a somewhat complete electronics parts list:
-hall effect for the wheel sensor
-limit switches for the drawer guides
-servo for the fairy
-green LED for the fairy
-DC gearmotors for the wall actuation
-Peristaltic pump to move the liquid
-Make Controller for analog/digital I/O
-80mm case fans to move fairy
Step 6: Completed Mechanism
It took a while to get it wired up and dialed in. Actually we didn't juice our first fairy until about 4 hours before my flight left for Europe.