# How to build a robot arm: a kit, a DIY servo arm, or an AI arm

You can build a robot arm three ways. Buy a kit for about $70, build a DIY servo arm on an Arduino, or build an open source AI arm like the SO-101. This guide covers parts, prices checked in October 2026, and the build steps.

Updated Oct 18, 2026. HTML version: https://robotsforthat.com/guides/how-to-build-a-robot-arm/

## Short answer

The easiest robotic arm kit is a 4 or 5 axis servo arm for about $70. Examples are the ACEBOTT QD022 ($69.98, ages 12+) and the Adeept 5 DOF arm ($69.99). A DIY arm needs 4 to 6 servos, a servo driver board and an Arduino; small servos cost about $6 each. For an arm that learns tasks with AI, try Hugging Face's open source SO-101. It starts around $100 in parts, per TechCrunch, but needs 3D printed parts and more setup.

| Option | Price (Oct 2026) | Axes | Controller | Good for |
|---|---|---|---|---|
| ACEBOTT QD022 robot arm kit | $69.98 | 4 servos | ESP32, blocks, Arduino or Python | Kids 12+ and first timers |
| Adeept 5 DOF robotic arm (Arduino or Pi version) | $69.99 | 5 | Arduino IDE, or Python on Raspberry Pi | Teens and adults |
| DIY servo arm from parts | about $70 to $170 | 4 to 6 | Arduino plus 16 channel servo driver | Learning how arms really work |
| Hugging Face SO-101 (open source) | about $100 to $500, per TechCrunch | 6 motors per arm | Computer running LeRobot | Adults curious about AI robots |

## What a robot arm is made of

A hobby robot arm is a chain of joints. Each joint has a servo, a motor that turns to an exact angle when you tell it to. A gripper at the end opens and closes.

Count the joints and you get the axes, or DOF (degrees of freedom). Four axes can pick up and place small objects. Six axes can reach from more angles but are harder to control.

## Option 1: a robotic arm kit

A kit is the quickest way to a working arm. All the brackets fit, and the code is ready.

The ACEBOTT QD022 is listed at $69.98 on ACEBOTT's shop. The maker says it has 4 servos, an ESP32 board, and is for ages 12+. You can drive it with a joystick or a web app, code it with blocks in ACECode, or move up to Arduino and Python. ACEBOTT says it has a memory grab function that replays a move.

Adeept sells a 5 DOF robotic arm kit for $69.99 in an Arduino version and a Raspberry Pi version. The Pi version lists support for Pi 4B, 3B+, 3B and A+ and comes with Python code and tutorials, per Adeept.

## Option 2: a DIY servo arm from parts

Building from parts teaches you why arms wobble, droop and drop things. You can cut the frame from thick cardboard or plywood, or 3D print a free design.

Here is a parts list with Adafruit and Arduino store prices checked October 18, 2026.

- Arduino Uno Rev3: $27.60 at the Arduino US store.

- 16 channel PWM servo driver (PCA9685): $14.95 at Adafruit. It runs up to 16 servos over two wires (I2C). It was out of stock when we checked.

- Micro servos (TowerPro SG92R): $5.95 each at Adafruit. Good for a small, light arm. You need 4 to 6.

- Or standard metal gear high torque servos: $19.95 each at Adafruit, rated 10 kg cm at 6V by the shop. Use these for a bigger arm or the shoulder joint.

- A separate power supply for the servos (a 4 x AA pack is $2.95 at Adafruit), jumper wires, screws and the frame material.

## Steps: build a 4 axis DIY arm

This plan makes a simple arm with a turning base, a shoulder, an elbow and a gripper.

- Sketch the arm on paper: a base, two arm pieces about 8 to 10 cm long, and a gripper.

- Cut or print the parts and mark where each servo will mount.

- Before you mount anything, plug each servo into the driver and set it to its middle position (90 degrees) with a short test program.

- Attach the servo horns while the servos sit at 90 degrees, so every joint starts centered.

- Mount the base servo first, then the shoulder, elbow and gripper servos, keeping the heavy servos low.

- Wire the servo driver to the Arduino: power, ground and the two I2C pins. Power the servos from their own battery pack, not from the Arduino.

- Move one joint at a time in code and find its safe limits so it never pushes against the frame.

- Write a sequence: open gripper, lower, close gripper, lift, turn, lower, open. That is your first pick and place.

- Add control: two joysticks or a phone app later, once the basic moves work.

## Option 3: an AI arm that learns (SO-101)

The SO-101 is an open source arm from Hugging Face and The Robot Studio. TechCrunch reported a base price of $100 in parts, rising to about $500 for assembled units, depending on the seller and tariffs. Sellers named include WowRobo, Seeed Studio and PartaBot.

Most people build it as a pair. You move the leader arm by hand, and the follower arm copies you. Hugging Face's LeRobot software records those demos so the follower can learn to repeat the task on its own.

Hugging Face's guide says the follower uses six STS3215 servo motors. The leader uses the same motor with different gear ratios, so it is easy to move by hand. You also need a motor controller board, a power supply, a USB cable and the 3D printed parts listed in the SO-ARM100 repository.

- Source the parts and 3D print the frame.

- Install LeRobot on your computer and add the Feetech motor extra.

- Find each arm's USB port with the LeRobot tool.

- Set each motor's ID and speed setting before assembly.

- Assemble the joints and gripper, then calibrate both arms.

- Record demonstrations with the leader arm and train the follower with the LeRobot tutorial.

## Common problems and fixes

- Arm jitters or resets the board: the servos need their own power supply.

- Shoulder droops: use a stronger servo at the shoulder and keep the arm short.

- Gripper drops things: add rubber bands or foam tape to the fingers.

- Servo buzzes at rest: it is pushing against a limit. Change the angle in code by a few degrees.

## Questions people ask

### What is the best robotic arm kit for a beginner?

A 4 or 5 axis servo kit around $70, such as the ACEBOTT QD022 ($69.98, ages 12+) or the Adeept 5 DOF arm ($69.99). Both come with code and tutorials, per the makers.

### How much does it cost to build a robot arm?

About $70 for a kit, or about $70 to $170 in parts for a DIY arm depending on servo size. The SO-101 AI arm starts around $100 in parts, per TechCrunch.

### Can I build a robot arm without a 3D printer?

Yes. Kits come with all the brackets, and a simple DIY arm can be cut from thick cardboard or plywood. The SO-101 does need 3D printed parts, which some sellers include.

### What servos do I need for a robot arm?

Micro servos like the SG92R ($5.95 at Adafruit) for a small arm. A metal gear standard servo ($19.95, rated 10 kg cm at 6V) for the shoulder of a larger arm.

### Can a robot arm use AI?

Yes. Hugging Face's LeRobot software lets the SO-101 learn tasks from demonstrations you give with a second leader arm.

## Sources

1. [ACEBOTT: QD022 ESP32 programmable robot arm kit](https://shop.acebott.com/products/acebott-qd022-esp32-programmable-robot-arm-kit-for-arduino)
2. [Adeept: robot kits and 5 DOF robotic arm](https://www.adeept.com/)
3. [Adafruit: 16 channel PWM servo driver PCA9685](https://www.adafruit.com/product/815)
4. [Adafruit: Micro servo TowerPro SG92R](https://www.adafruit.com/product/169)
5. [Adafruit: Standard size high torque metal gear servo](https://www.adafruit.com/product/1142)
6. [Adafruit: 4 x AA battery holder](https://www.adafruit.com/product/830)
7. [Arduino US store: Arduino Uno Rev3](https://store-usa.arduino.cc/products/arduino-uno-rev3)
8. [TechCrunch: Hugging Face releases a 3D printed robotic arm starting at $100](https://techcrunch.com/2025/04/28/hugging-face-releases-a-3d-printed-robotic-arm-starting-at-100)
9. [Hugging Face LeRobot docs: SO-101](https://huggingface.co/docs/lerobot/en/so101)