Build 4-DOF Robot Arm under $10 (MeArm) (Part 1)
I’ve always been captivated by inexpensive DIY contraptions. There’s something deeply satisfying about building things yourself, and what could be more exciting than robots? However, robotics typically comes with a hefty price tag — even a basic robot arm can cost upwards of a thousand dollars, making it inaccessible for weekend hobbyists like me who want to have fun building things.
Fortunately, exceptions exist, and one remarkable example is the “ultra cheap robot arm” project, better known as MeArm. Started by Ben Gray (aka phenoptix) from the UK in 2014, this project was inspired by the Kickstarter-funded uArm. However, it’s Gray’s MeArm — a 4 degrees of freedom robot arm — has gained worldwide popularity. This success is unsurprising given its fully open design and affordability; including clones, you can build one for less than $10 for the frame, plus the cost of 4 servos and a microcontroller like Arduino Uno.
I assembled my first MeArm in September 2017 and have since witnessed numerous variations. Despite the project’s accessibility and its excellent demonstration that robotics needn’t be expensive or intimidating, I believe the original project deserves more recognition, and there’s still a gap in comprehensive how-to documentation online. Often, clones are sold without any instructions whatsoever.
In this series of articles, I’ll share my experience with the MeArm, covering:
- Building the physical structure.
- Calibration techniques.
- Implementing inverse kinematics — crucial for more advanced applications.
Whether you’re a beginner curious about robotics or an experienced maker looking for an affordable project, the MeArm offers a perfect entry point into the fascinating world of robotic arms.
Disclaimer: MeArm is a registered trademark of MeArm Limited. I have no affiliation with this company and am not receiving (nor do I expect to receive) any endorsement from them. This series of articles documents my personal experience with a fun DIY project I’ve enjoyed working on in my spare time.
What is MeArm?
The MeArm is a compact, affordable 4 degrees of freedom robot arm that has gained popularity in the maker community. Let’s explore its origins and availability.
Official Source
The official website at shop.mearm.com was created by the original author of the MeArm. The design has evolved through several iterations, each with its own version number. You can find details about these versions on their history page.
Options
You have several ways to obtain a MeArm:
- Purchase a kit from the official website.
- Create your own using the open-source laser-cut files available on GitHub.
- Buy a clone from marketplaces like Amazon or AliExpress (searching for “4 DOF Robot Arm” will yield many results).
It’s worth noting that third-party clones can vary significantly from the original design, often featuring mix-and-match variations of different versions as I will show below.
Evolution
The MeArm design has evolved considerably since its inception. The latest official version as of this writing is v3.0, which you can see assembled by Ben Gray himself in this YouTube video.
For those interested in the project’s origins, the original v0.1 design was published on Thingiverse back in 2014.
Throughout this series, I’ll be sharing my experience with building and programming a MeArm clone, providing insights that should be helpful regardless of which version or variant you’re working with.
Instructions
Before assembling your 4-DOF robot arm, it’s important to identify which version you have. For the latest official v3.0, comprehensive instructions are available on Instructables (published in 2019).
Among clone products, the most popular versions are typically v0.4 or v1.0. The original instructions for these versions can be found here:
- MeArm v0.4 Instructions (2014)
- MeArm v1.0 Instructions (2015)
What I’ll Be Building
One of the main cost advantages of the MeArm design is that the robot arm is cut from flat sheets of material — either acrylic or wood. I’ve previously built an acrylic version but found that the claw gear was easily damaged. For this article, I’ll be working with a wooden version that cost me approximately $6 including four servos (yes, really that inexpensive!).
Interestingly, I received a hybrid between the v0.4 and v1.0 versions, which is common with clones. Rather than walking through every construction step in detail (since the official instructions already do this well), I’ll share my experience building this particular model and highlight how clone versions might differ from the original designs.
Initial Calibration
A crucial initial step — often overlooked in some instructions — is calibrating the servos to their default positions before assembly. This is straightforward but essential for the proper functioning of your 4-DOF robot arm.
The robot arm uses four servos:
- Base (rotation),
- Shoulder,
- Elbow,
- Claw (also called gripper).
I’ve provided code examples for this calibration in my GitHub repository.
Following the recommendations from the v1.0 instructions, I connected each servo individually to my Arduino Uno (PWM pin 6, along with 5V and GND).
Using a simple sketch, I set each servo to 90 degrees and marked this position with a pen. After marking the last servo (designated for the claw), at a 90-degree position, I updated the sketch to set it to 25 degrees.
This approach accomplishes two things:
- all servos are calibrated to a known position,
- the claw servo is easily identifiable since it’s set differently.
Why This Matters
This calibration aims to ensure your 4-DOF robot arm is assembled with the servos in their default positions. Ideally, the 90-degree mark should align with the center position of the robot arm’s mechanical parts.
While perfect alignment rarely occurs in practice, this initial calibration ensures that the servo motors’ range of motion will reasonably match the expected movement range of the robot arm’s physical components.
When I built my first MeArm without proper calibration, I had a severely limited range of motion — only about half of what should have been possible. This happens because slight alignment shifts occur when you connect the arms to the servos. Additionally, the mechanical load and the basic nature of these inexpensive servos (“ultra cheap,” remember?) can further impact positioning accuracy.
Taking the time for this calibration step will significantly improve your robot arm’s performance and range of motion!
Build
After calibrating the servos, I extracted the pre-cut parts from the wooden sheets. The pieces are designed to fit together in one specific way, so it takes some trial and error to find the correct orientation, though this process wasn’t overly time-consuming.
I started by inserting the four largest screws in the base and assembled the square structure with the servo motor that connects directly to the base.
Since these holes don’t have actual threads (they rely solely on size differences for fit), I ended up stripping the makeshift “threads” almost immediately and resorting to glue. This particular wooden kit seems quite delicate — the acrylic version I built previously was more robust in this regard.
The left and right sides were close to the v1.0 design, but the middle section deviated significantly, confirming that my kit is a hybrid between the v0.4 and v1.0 designs.
Next, rather than strictly following either the v0.4 or v1.0 instructions, I:
- attached the base to the base servo to create a foundation,
- assembled the arm components on the right side,
- connected the right side, center pivot (“pig”), and middle parts.
During this process, I had to swap the servo lever on the left side for another option and then back again. The first lever wouldn’t hold the screw properly, and the alternative appeared to be designed for the claw, which followed the v0.4 design pattern.
Only after this sequence was I able to connect the left side properly. Working with this hybrid model actually gave me insight into the evolution of the MeArm design — I could see why certain parts changed between v0.4 and v1.0, making it an educational experience despite the challenges.
I ultimately had to leave the arm partially unassembled without the claw until I could purchase additional fasteners, primarily because the holes were oversized and the kit was missing nuts. While I recommend buying proper kits rather than random clones (unless you enjoy problem-solving), it’s hard to complain too much when the entire package, including servos, costs less than $6!
Later, after acquiring the necessary screws, nuts, and other hardware, I was able to complete the arm. I also added rubber feet to the base, as the base servo motor sits lower than the platform and requires some form of spacer.
Conclusion
Despite the challenges I encountered with this $6 build — oversized holes, missing fasteners, and hybrid design elements — the project was both rewarding and enlightening. More importantly, it demonstrates something remarkable: robotics doesn’t have to be expensive or intimidating to get started.
The MeArm design, whether you obtain an official kit, a clone like mine, or laser-cut your own parts, opens up the world of robotics to hobbyists, students, and makers on virtually any budget!
Next Steps
Now that we’ve assembled the physical structure, we’re ready to bring our robot arm to life! In the next article, we’ll move beyond hardware and explore:
- Proper calibration of servos for optimal range of motion.
- Implementation of inverse kinematics to control arm movement.
- Writing Arduino code to make the arm move predictably in 3D space.
With these fundamentals, you can transform this seemingly simple contraption into a precisely controlled robot arm operating in 3D space. The skills you develop here can serve as a foundation for more complex robotics projects in the future.
The project code is going to be built up here: https://github.com/loginov-rocks/4-DOF-Robot-Arm — it can be useful as a boilerplate for experimenting with your own robot arm implementation.
That’s all for today, see you next time!
This article was refined with assistance from Claude 3.7 Sonnet.
