My First Planetary Gearbox (5:1) for servo MG996R

This is my first planetary gearbox, designed completely from scratch in Fusion 360.

I created it mainly because I wanted to learn how planetary gear systems work and gain some hands-on experience designing mechanical components. The result turned out much better than I expected — the gearbox runs smoothly and has surprisingly little backlash.

Gear Specifications

• Gear ratio: 5:1
• Sun gear: 12 teeth
• Planet gears: 4 × 18 teeth
• Ring gear: 48 teeth
• Module: 1

Designed For

The gearbox was designed around a continuous rotation MG996R servo.

Hardware Required

• 5 × M3×8 mm screws
  • 4 for mounting the servo
  • 1 for attaching the sun gear to the servo
• 4 × M2×15 mm screws and 4 × M2×8 mm
  • for securing the ring gear assembly and cover

Printing Notes

• Some parts require supports
• PLA works fine for testing and learning
• Print with good dimensional accuracy for the best gear mesh

Performance

The gearbox is fully functional and capable of transmitting significant torque.

One important lesson I learned during testing: be careful when ordering MG996R servos. I accidentally received a version with plastic internal gears, and the servo gears failed before the printed planetary gearbox did.

What Surprised Me

The biggest surprise was how little backlash the gearbox has. Since this was my first planetary gearbox design, I expected much worse results.

Why I Made It

I built this project simply because I was curious about planetary gear systems and wanted to understand how they work. It was a great learning experience, and I am sure the knowledge gained from this project will be useful for future robotics and actuator designs.

If you improve or remix the design, I would love to see your version.