A key mission of NSK is to create products that contribute to the environment. Using a variety of approaches, NSK is moving closer to its goal of contributing to a safer, smoother society and helping protect the global environment. One such environmentally friendly product is the "High-Durability Precision Ball Screw." We asked the designers about the thought process that went into its development.

Ball Screws—Making it Possible to Translate Motion

Naoki Ball screws, which are made up of a screw shaft, a ball nut, balls, and a recirculator, serve to translate rotational motion to linear motion. Ball screws are used in machine tools and semiconductor manufacturing equipment. They can also be found in injection molding machines used to produce the smartphone chassis that we all use. Ball screws are in high demand in a wide range of industries including automobile components, such as electric-hydraulic brake systems. Ball screws can even translate linear motion into rotational motion, which is a feature utilized in vibration damper for buildings.

Takashi One characteristic of ball screws is their ability for high-precision positioning. Since they can achieve very precise motion, they can help to increase the precision of machinery. Ball screws can also convert a slight rotational force into a much larger thrust. This characteristic is utilized in machines that need to generate extremely large forces, such as press machines.

Solving Customers' Problems with a Unique Process

Naoki The sophistication and precision of machines are ever advancing with the development of new technology. As a result, ball screws have come to be used in much more severe conditions than ever before. For example, in recent years our customers have released devices that move at extremely low speeds and devices that repeat very minute movements. Such advancements have made it necessary for NSK to create new products to adapt to these changes in the market. This is what led to the development of the "High-Durability Precision Ball Screw."

Takashi Under conditions of low speed movement or repeated fine movements, the metal of the groove and the metal of the balls make contact and grate upon each other inside the ball screw-a phenomenon known as "wear." Such wear can be mitigated by introducing a lubricant to form an oil film over the metal surfaces in contact with one another. However, operating the ball screw at low speeds makes it hard to form this oil film, causing wear to occur. When wear occurs, a crack is formed between the parts of the ball screw and rattling occurs, leading to deterioration of the precision of machinery.

Therefore, the "High-Durability Precision Ball Screw" is made with a special microstructure (a kind of surface processing) that makes is easier to form an oil film on the surface of the material. Thanks to this microstrucure, gaps are formed where the surface of the balls make contact with the groove, allowing oil in to reduce friction and maintain precision.

Naoki The catalyst behind the development of this technology was a problem that customers wanted us to solve. After talking with customers and discussing their concerns, we found that wear associated with using ball screws was a common issue. We are currently moving forward with the development of this product by getting feedback on sample products we have provided to our customers for testing. Producing the microstructure requires more effort than conventional products, so we are keeping cost in mind as we move forward.