3-D Printed Robot Arm

I often go around to schools in my area to show off projects that I have been working on, as an engineer, in order to promote STEM. After presenting to the class I always speak with the instructors to find out how they teach their classes and what some of their problems are. A recurring theme has been the cost of robotics kits.

Kits like the LEGO Mindstorms are too expensive to provide one for every student, and they lose pieces over time. Low cost kits rarely spark the imagination of the students. And few kits have the capability to allow students to actually build something from scratch.

So I took a couple of days on the weekend and started prototyping a simple robot arm that would be 3-D printed and run off of an Arduino. The result is a system that costs less than $50 and can be used as a teaching tool for entry level users, but is also complex enough that a person could use it during their graduate robotics program for testing programs.

There are 4 primary 3-D printed pieces. The base, the shoulder, the upper arm, and the forearm. These make up the structure of the arm without an end effector. Each is easily 3-D printed. I use a Makerbot Replicator 2X so I can easily create rafts. But the pieces can be printed without rafts just fine. The forearm in particular will warp if you don’t have a heated bed and poor adhesion. All the pieces were designed in Autodesk Inventor.

Grippers can be added by either screwing them on or using a modular slider joint that is implemented in the end of the arm. I have designed 3 so far. One is a traditional gripper whose fingers are geared together. Another is a rigid clamp for a sharpie pen. And the last is a simple hook.

There are four MG90S metal gear servos used to articulate the arm. I like these servos because I was able to use all identical servos throughout the arm to reduce complexity, but still have a decent payload capability and low cost.

The base of the arm is designed to hold a miniature breadboard and the Arduino Uno used to control the arm. In the first couple of iterations I had the arm separate from the boards. But after carrying it around to show friends I quickly just expanded the base.

As I said the Arduino Uno was used to control the arm. I used the Arduino particularly for the project because of the support available. I was afraid that it wouldn’t have the memory or speed to do the inverse and forward kinematics that I am putting into the arm. But is has handled it well so far.

The arduino is powered through the USB cable that allows control from the computer. The servos are powered by a 6V 1A power adapter that be had off amazon.

Currently I control the arm through a GUI created using Tkinter in python. It is a decent interface for the moment but I am working on controlling it using just a mouse.

I have had several friends and teachers say that they want one for fun or school. So I am working on turning it into a full kit. Right now the website is up to download all CAD and code to build it. And there are links to purchase parts like the servos. Over the next few weeks I will be creating tutorial videos on building and using the arm.