Robot arm

This year I took on the challenge of designing and building a robot arm as part of my marble machine project for school. The process was full of learning opportunities, design changes and iterative problem-solving, and it helped me grow as a maker.

The arm went through several major iterations while I was building it.

• Servo mounts

  I first designed the base to hold a single standard servo, but it was too weak to lift the arm, which led to multiple redesigns. I switched to two regular servos, then finally to a powerful 80 kg·cm servo. That meant reprinting the base servo mount three times.

• Arm design

  To fit more wiring I had to reprint two of the arm sections. That improved the arm overall and made room for the light and LDR used to detect marbles.

• Collection system

  I printed the collection system once, then revised the chute to improve marble flow and save filament. The final version uses a simplified two-part support.

Limits of 3D printing

It's possible to print gears and servo mounts, but they don't hold up reliably under stress and tend to fail over time.

The value of iteration

Iterating on designs and adapting to new challenges is a critical part of engineering.

Mechanical design

Stability and precision matter. Bearings in the joints, better servo arms and integrated screw holes would make a big difference.

A larger arm

I'd use stepper motors with potentiometers for precise control, and belts to keep the motors closer to the previous joint and take stress off them.

The same size

I'd refine the servo arms with cut-outs and screw holes for secure mounting, and add bearings to the joints for stability and precision.

Colour detection

I'd use a dedicated RGB colour sensor instead of an LDR, for more accurate and reliable results.