NOTE: This is a work in progress. I might make modifications or add features at some point.
I've included OpenSCAD source for remixing purposes. I've also included an STL of an SG90 servo for reference purposes.
This is a little robot arm that uses six SG90 servos. The idea was to make a the smallest robot arm possible with common parts and still have reasonable freedom of movement. It's also designed to come apart relatively easily for quick modifications.
Here's the little guy in action (controller arm and microcontroller not included)…
Before printing any parts, decide on what servos you want and purchase them. I highly recommend getting original Tower Pro servos (either SG90 or MG90, digital or analog versions. There are tons of knock-off SG90 servos with slightly different dimensions, and their quality varies wildly.
Once you've got the servos in hand, print the servo-shaft-gauge model. Use that to determine which arm parts you need to print. Check to see which hole the servo's shaft fits into. It should be as snug as possible to avoid slipping. The number next to the hole will correspond to the folder containing the arm parts you need to print.
You'll need one each of: base, shoulder, segment1, segment2, wrist, gripper. There's only one base model since it doesn't connect to a servo shaft. NOTE: Print the parts using the same filament as you used for the servo shaft gauge. Otherwise, you might run into tolerance issues. You should be able to print all parts without support material.
It helps to load the assembly.stl model into an STL viewer to visualize how everything fits together. It's easy to, say, mount a servo backwards if you're not sure of the orientation.
Using the microcontroller of your choice (I used an Adafruit M0), test the center position of each joint. I did this by hooking up each servo, one at a time, commanding the servo to its center position and, if necessary, unmounting the connected part and adjusting its position to match.
For the gripper, you might want to limit the range of the servo's sweep to avoid slamming the two fingers together.
At this point, you should have a functioning arm. You can program the microcontroller to perform various tasks or, like I did, build a controller arm and use the microcontroller to translate my movements onto the robot arm.
The author marked this model as their own original creation.