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Personal Project: Six DOF Stepper Arm

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Hardware Design Robot Arms Stepper Arm

Motivation
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In my last semester of undergrad, I enrolled in MEEN 408/612: Robotic Manipulators with Dr. Dharba. It was a challenging but fascinating course, and a big reason why I decided to pursue robotics as a career.

Part of the class focused on different control strategies for manipulator arms. Since there were no lab sessions, I wanted to take what I learned and apply it to real hardware.

Open Source Robot Arm
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The most cost-effective way to get an arm was to build one myself. I found a small group called Annin Robotics that sold pre-designed kits. These kits included machined parts and a bill of materials for sourcing the rest from Amazon or McMaster-Carr.

Design Lessons
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The parts arrived, and I started assembly around the same time we were designing the RoboBall pendulum. As you can imagine, working with Dr. Ambrose on a custom robot is wildly different from assembling a cheap kit. Here are a few lessons I learned while building this arm alongside RoboBall:

  • Standardize your fasteners – This kit used multiple bolt heads, set screws, and thread types. Keeping track of them was a pain compared to RoboBall, which only used 4-40s and 10-32s.
  • Use standard components wherever possible – For some reason, all the screws were metric, which made it harder to find spares locally.
  • Working in an apartment is very limiting – Building an arm requires a surprising amount of space and tools. My bedroom couldn’t function as both a workshop and a place to sleep.
  • Design with maintenance in mind – The kit called for many components to be soldered directly together. Adding connectors might have increased bulk but would’ve saved a lot of headaches during repairs.
  • Keep software modular and familiar – The included control software used a custom serial protocol, with all the low-level logic lumped into one massive for loop. It was nearly impossible to read or debug.

Low Budget Apartment Build
Cramped workspace in my apartment

Calibration Video
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I eventually finished assembling the arm according to the kit instructions, but didn’t have time to go further as the RoboBall project was ramping up.

Update — October 2025
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I’ve since finished grad school and learned a lot more about robot programming. Once I’m settled into a new job, I plan to rewrite the control software in ROS 2 and possibly implement some controllers using the pydrake library.