The cheapest useful robot arm is compact, servo-driven and honest about payload limits.
The cheapest robot arm that still teaches real robotics is a compact 4-axis servo arm with a small gripper. It will not lift heavy objects, but it can teach joint control, saved poses, calibration and simple pick-and-place.
Do not make the links too long. Short links reduce torque requirements and make cheap servos less frustrating.
Controller and web sliders
Servo PWM expansion
Low-cost metal gear servos
Servo power with current headroom
Short links and servo brackets
Light pick-and-place end effector
Base, shoulder, elbow and no wrist.
Use stronger servos on shoulder and elbow only.
Treat the generated output as a prototype plan, not a certified product. Body-adjacent, high-voltage, optical-energy and mobility builds need qualified review before real-world use.
Not reliably. Design for small blocks, pens or light parts.
It keeps servo timing stable and leaves ESP32 pins free.
The shoulder servo and power supply.
Start with this prompt prefilled, then let RoboHub generate the live parts list, wiring plan, CAD and firmware.
Generate build