This is a compact 3D printed robotic arm designed for hobby robotics, Arduino projects, STEM learning, and servo/stepper motor experimentation.

The arm uses 4 SG90-style micro servos for joint and gripper movement, along with a 28BYJ-48 5V stepper motor and ULN2003 driver board for base rotation. It is designed as a light-duty educational robot arm, perfect for learning basic robotic movement, multi-servo control, stepper motor control, gripper mechanics, and Arduino-based robotics.

This model is intended for makers, students, and hobbyists who want a simple robotic arm platform they can build, test, modify, and improve.

The design is prototype-friendly and remix-friendly. It is not meant for heavy lifting or industrial precision, but it works great as a small desktop robotics project.

Hardware Required

• 4x SG90-style 9g micro servos
• 1x 28BYJ-48 ULN2003 5V stepper motor
• 1x ULN2003 stepper driver board
• 7x M3-style bolts and nuts
• Arduino, Raspberry Pi, or compatible controller
• External 5V power supply recommended
• Jumper wires

The 7 M4-style bolts and nuts are used to attach the base to the housing and to mount the stepper motor to the base.

Suggested Printing Notes

Print orientation and tolerances may vary depending on your printer. Some light sanding or fitting may be required, especially around servo openings, bolt holes, and moving joints.

For best results, use a sturdy material like PLA+, PETG, or similar. Standard PLA should work fine for basic testing, but stronger materials may hold up better over time.

NOTE: You are not crazy; many manufacturers of the SG90 motors use different-sized horns. There's some built-in tolerance for smaller horns; the arm will just be slightly more wiggly. For larger horns you may need to sand the inserts some, but they should fit in almost perfectly.