are a kind of transmission parts that convert rotary motion into linear motion. The bead screw is a more commonly used transmission element in tool machinery and precision machinery. Planetary roller screws combine helical and planetary motions and are characterized by high load and high precision. मानक प्रकारको ग्रह रोलर स्क्रूहरू सबैभन्दा व्यापक रूपमा प्रयोग गरिन्छ, र रिभर्स प्रकार सबैभन्दा कम्प्याक्ट र काल्पनिक छ।