Glossary · Hardware
Planetary roller screw
In brief
A planetary roller screw converts rotary motion to linear motion using threaded rollers around a central screw. It carries far more load than a ball screw at similar size, runs at high duty cycles, and is the actuator standard inside Tesla Optimus.
Where a ball screw uses recirculating balls to convert rotation to linear motion, a planetary roller screw uses threaded rollers — many points of contact, much higher load capacity, and longer life under cyclic loading. Tesla's Optimus team chose planetary roller screws for the linear actuators in the legs and hips precisely because the duty cycle of a humanoid is brutal — every step is a load cycle.
The trade-off is cost and supplier scarcity: planetary roller screws are not commodity components, and qualified suppliers are few. For humanoid programs targeting volume manufacturing, securing roller-screw supply is a real strategic concern.
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