Introduction: Printing a Robot Arm
Back in 2006, a client of mine wanted to make a robot arm to play Go. The idea was to allow remote play on real boards with the robot arm moving the stones for the remote player. Two arms would be used to keep two physical boards in sync with each arm matching the moves made by the other player. The goal was to make an arm that would fold into itself so you could easily transport it in a backpack. It would have two cameras: one to watch the board and another one to guide the vacuum picker to a piece.
The arm was designed in Autocad and printed on a Dimension ABS printer at Tech Shop in San Mateo. I showed this arm at Maker Faire 2010 in San Mateo and got a "Editors Choice" award. Even though this project was done in 2006, I wanted to document it now for the "Make It Real" contest.
The robot design here, the videos and the drawings are all (c) 2006-2012 Tim Black. I want to retain the rights to the arm design, so it is not fully documented here. The purpose of this instructable is to show you an overview of the steps that were required to design and build the arm from sketches to working prototype.
Step 1: Sketches
I had the idea for the design before I had the means to build it. It all started with paper and pencil drawings. I worked out the basic interplay of the parts and the way that the parts of the arm would fold into each other doing a number of these rough sketches. Not shown here are the many discarded ideas and experiments that led to this design that we decided to build.
Step 2: 2D Drawings
After the sketches looked good, I did some 2D drawings to study the range of movement of the parts. These drawings were also used to refine the design and plan the 3D parts. Several drawings show fold out feet, these were not in the first prototype. I just mounted it on a slab of high density composite board.
Step 3: 3D Drawings
The 2D drawings were used to design the entire arm in Autocad Inventor. I had help with this as I did not know this CAD package well. The CAD design was refined in several passes with the renderings used to look for the proper placement of the parts.
Step 4: Printed Parts
A 3D printer at TechShop (San Mateo) was used to print the parts from the CAD drawings. The assemblies were too big for the printer to make in one piece, so they were broken up into kit style parts and then glued together. After assembly they were dipped in acetone to harder the layers and then painted for color.
Step 5: Gears and Motors
You can also see the way that the elbow and wrist motors are mounted at the shoulder and turn drive shafts into the helical gears at the elbow. The first gear set is hard mounted to the elbow and extends the lower arm. The wrist is operated by a toothed belt from the second gear and this extends and retracts the finger.
Step 6: The Finger
Here you can see the finger tip with it's small vacuum cup tip. There was a small vacuum pump in the body with a dump valve to allow the Go stone to drop when you had the correct location. You can see the vacuum line going from flexible to hard line in different parts of the arm and around the joints. The layers from the printer are very visible where the angle of the arm is small.
Step 7: Servo Sensors
Step 8: Testing
The assembled parts were tested with power supplies instead of servo control. I used a custom power panel to run the motors around in this video. http://www.youtube.com/watch?v=1Q1CvGG4Szw
Step 9: Working
The finished arm was able to pick up go stones and move them around.
We never finished the video remote controls or web link parts, but I still think the arm is cool.
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