Sunday, November 30, 2014

Maker Faire 2014: さらし首 (sarashi kubi)

Apart from the stroboscope, I brought a scary robot arm to the Tokyo Maker Faire. This project actually started a few months ago during a Shinamonolab meetup.

During the meetup, participants had to sketch up an idea for the Maker Faire. I thought of building an arm robot that would scare children and take a photo of them. Three other guys were also interested in building a robot so we got together as a team called roboband (ロボバンド).

My first step was building up the robotic arm. Since Tokyo HackerSpace recently acquired a laser cutter, I decided to use it for cutting the open hardware meArm v0.4 robot. Unfortunately, my first attempt ended in failure because I was using a 6mm thick MDF wood sheet which was not appropriate.

After reviewing the CAD model more carefully, I decided to buy 3mm acrylic sheet and cut it again. This time I managed to assemble the robot correctly (I still had many problems with the accuracy of the laser printer software). The servo motors (standard 9G) are very cheap if you buy them in

Next, I created a 3D model of my scary robot using Blender. I tried not to make it too complicated because my intention was to later convert it into papercraft.

The 3D model was converted into 2D papercraft using a software called pepakura. Cutting and putting all those parts together can take you almost one day.

Then, I applied some Epoxy resin (GM-6600) to make it harder and more robust. I used an organic vapor respirator with appropriate filters, safety googles and nitrile gloves while handling the resin in my balcony. It is not as dangerous as polyester resin but I don't think it's good for health either.

Regarding to the software I used the Arduino servo library to control the servo motors and light up the LEDs in his face whenever a character was sent from Raspi through the serial port. The Raspi itself was used to detect the presence of a face, through a cheap webcam and the simpleCV library, emit a scary sound through the pygame library and communicate with Arduino through the serial library.

The robot was quite popular among children which made me very happy. However, some children were a bit cruel against my little robot haha. In fact, when I got back home I noticed that the SD card on my raspi was broken, meaning that I lost all the photos of scary faces I took during the event. Next time I should add a case.

No comments: