Linear transmission is a mechanical transmission method that converts rotary motion into linear motion or vice versa. There are various types of linear transmission, such as belt drive, chain drive, hydraulic drive, screw drive, pneumatic drive, and electromagnetic drive. Among them, screw drive, due to its unique advantages, is used in almost all applications requiring precise linear motion control. Typical applications include automobiles, machine tools, semiconductor equipment, medical equipment, robots, and aerospace.
What is a lead screw?
Lead screws are ideal products for converting rotary motion into linear motion or vice versa. They are the most commonly used transmission components in machine tools and precision machinery. Their advantage lies in ensuring accurate positioning at high speeds, and due to their low friction, their transmission efficiency can reach 90%.
A lead screw consists of a nut and a screw/lead screw. The screw is the rotating part in the lead screw mechanism, usually cylindrical, with a helical thread on its outer surface; the nut is the linear motion part in the lead screw mechanism, and its inner surface matches the thread of the screw.
Working principle: When the screw acts as the driving rotating element, the nut, following the screw's rotation angle and according to the corresponding lead, converts the screw's rotational motion into linear motion. The workpiece performing the work can achieve the corresponding linear motion by connecting to the nut. The screw's rotation angle is directly proportional to the nut's linear movement, and this ratio is determined by the screw's lead (thread pitch). Conversely, if the nut moves as the driving element, it can also cause the screw to rotate, thus converting linear motion into rotational motion.
Screw Classification
Based on their friction characteristics, lead screws can be divided into three categories: sliding lead screws, rolling lead screws, and hydrostatic lead screws.
Source: Wanjie Transmission, Ke Hao, "Precision Analysis and Design of Planetary Roller Screw Transmissions"
1) Sliding lead screws are the most common type of lead screw mechanism. Their tooth profile is mostly trapezoidal, hence the name trapezoidal threaded lead screw. They have no rolling elements and transmit thrust through sliding friction. They are simple in structure, easy to manufacture, and self-locking, making them widely used in machine tools. However, they generate significant heat during continuous operation, resulting in relatively low transmission efficiency (30-50%).
2) Based on the different rolling elements, rolling screws can be further divided into two categories: ball screws and planetary roller screws. The following text will focus on these two types of screws.
3) A hydraulic screw requires an additional oil/air supply system to achieve non-contact or near-non-contact motion by forming a fluid film between the nut and the screw, which greatly reduces friction and wear and can achieve extremely high positioning accuracy. However, its process is complex, very difficult to process, and has a high cost, so it is rarely used.
Source: Nanjing Arts and Crafts
Accuracy is one of the key indicators for evaluating the performance of ball screws . High-precision ball screws can provide more accurate positioning and repeatability. According to ISO (International Organization for Standardization), DIN (Deutsche Industrie Norm), and JIS (Japanese Industrial Standards), the accuracy grades of planetary roller screws and ball screws are generally classified in the same way, mainly based on the lead error (V_300) over any 300mm length of the screw. ISO classifies accuracy grades into C0, C1, C3, C5, C7, and C10, while DIN classifies them into C1, C3, C5, C7, and C10. Except for C0, the ISO and DIN classifications are basically the same. Some European and American companies use the letter G to distinguish accuracy grades, but the meaning corresponds one-to-one with the ISO grades. The precision grades of ball screws in China are divided into 7 categories (P1, P2, P3, P4, P5, T7, T10), with the precision decreasing sequentially from 1 to 10. That is, the smaller the number, the higher the precision.
Most ordinary machinery is manufactured by rolling, corresponding to C7 and C10 precision grades; in applications with higher precision requirements, grinding is often used, corresponding to a precision range of C0-C5.
Low precision requirements: Consumer tools such as smart home devices, power tools, and automobiles have lower precision requirements for lead screws, and currently mainly use trapezoidal lead screws and low-to-mid-range ball screws. Among them, automotive power steering systems and linear brakes have precision requirements of C6-C8 and C5-C8, respectively.
High precision requirements: Industrial machinery and equipment have certain precision requirements, which vary depending on the type of equipment. Generally speaking, general-purpose machinery or ordinary CNC machinery requires C7 (positioning error ±0.05 within any 300 mm stroke) or below; high-precision CNC machinery requires C5 (±0.018) or higher and C3 (±0.008) or lower; optical or inspection machinery requires C3 or higher. Robotic arms (precision grade) require precision of C1-C4, and high-precision grinding machines require C0-C2.
Lead screw technology barriers
There are three main barriers to producing high-precision ball screws: raw materials, process flow, and production equipment .
1. Raw materials
Materials are the foundation of lead screw manufacturing, and lead screws have stringent requirements for raw materials. During repeated motion, lead screws are subjected to continuous vibration, impact, and friction, thus demanding specific strength, rigidity, wear resistance, corrosion resistance, fatigue resistance, and load-bearing capacity from the materials. Ordinary metal materials cannot meet these requirements, typically necessitating the use of special metal materials. According to the Bote Precision website, the materials used for lead screws vary depending on the working environment, precision, and load requirements. Common materials include carburized steel, hardened stainless steel, non-alloy (carbon) structural steel (such as 45 and 50 steel), low-alloy tool steel, and bearing steel. Factors such as the rare element Cr/Mo ratio and processing technology affect the material's stability, melting point, and stiffness.
Inferior raw material quality and improper subsequent hot working processes are among the reasons for the performance gap between domestic and imported ball screws. Both foreign and domestic ball screws use high-quality alloy structural steel with added Mo, but the performance of domestic Cr/Mo steel ball screws still lags behind that of imported ones. According to the "Quality Analysis of Domestic Cr/Mo Steel Ball Screws and Similar Foreign Products," the banded segregation structure present in domestic ball screws is a significant reason for their poor performance. This banded structure, with its significant directionality, is a weak point, easily causing stress concentration during deformation and even cracking. It also reduces the steel's mechanical properties, machinability, and hardenability, increasing the tendency for quenching deformation and reducing strength and toughness.
2. Process Flow
Technological experience is an intangible yet crucial aspect of mechanical components. Because the machining process for lead screws is lengthy and complex, numerous factors, such as raw material formulations, heat treatment temperature and humidity, and machine tool parameter adjustments, all influence the final performance of the lead screw. Lead screw manufacturers require a considerable period of accumulation to master all the processes, and must continuously iterate and optimize through application and feedback. Globally, leading overseas companies in high-end lead screws all possess a long history and extensive experience.
The machining technology for lead screw shafts is divided into two types: cold rolling and grinding. The annealing process in cold rolling and the thread cutting in grinding are the difficult aspects of the process. Cold rolling has high efficiency but low precision. The thread is formed in one step without subsequent cutting, allowing for mass production at a lower cost. The precision level is typically between C9 and C5. Grinding has low efficiency but high precision. It first forms a coarse thread through cutting, and then improves the thread precision through a precision grinding process. The process is complex, has a longer delivery time, and is more expensive. The precision range of C9 to C0 can be achieved in the market.
Furthermore, heat treatment is also a core element in the manufacturing process, as it can improve the material properties and cutting performance of the ball screw. Outdated technology and equipment, or inadequate heat treatment process parameters, can lead to poor heat treatment results, greater deformation after heat treatment, and consequently affect the lifespan of the planetary roller ball screw.
3. Production equipment
The equipment determines the machining accuracy and efficiency of the leadscrew. Grinding machines are the core technological barrier in leadscrew machining, and their precision directly determines the leadscrew's accuracy. Through its highly precise grinding technology, the grinding machine ensures that the leadscrew has a consistent thread shape and size, thus providing reliable performance and stable motion control. The precision of the grinding machine directly affects the axial accuracy, radial accuracy, and overall motion smoothness of the leadscrew. Precise grinding processes ensure that each thread of the leadscrew has highly consistent specifications, preventing errors and vibrations, thereby improving the system's reliability and working accuracy. Therefore, the high-precision machining capability of the grinding machine directly determines the final performance and quality of the leadscrew.
There are relatively few domestic manufacturers of high-precision grinding machines, and their products lag behind world-class equipment in terms of precision and stability. According to GGII, domestically produced grinding machines can currently meet the requirements for machining mid-range lead screws with C3-C4 precision, but when mass-producing high-end lead screws (C0-C2), inconsistent output occurs. Imported equipment is very expensive and has long lead times; a high-precision thread grinding machine from Mitsui in Japan costs over 10 million yuan. Besides grinding machines, China also relies heavily on imports for cyclone milling equipment, heat treatment equipment, and straightening equipment, which also lag significantly behind imports and are largely dependent on imports.
ball screw
Ball screws, also known as ball screw pairs, are suitable for precision transmission. They generate point contact rolling friction, which results in lower friction, higher transmission efficiency, and higher precision compared to sliding screws.
The main structure of a ball screw consists of three parts: the ball screw, the ball nut, and the balls . The ball screw shaft is the guide shaft for the nut's movement, and its surface has threads in which the balls move. The nut, composed of a preload plate, a reverser, and a dust cover, is a linearly moving body that drives the ball circulation mechanism. In addition, its end seals are used to seal and lubricate the parts and prevent foreign objects from entering. The balls are the medium that maintains the operation of the entire component using a low coefficient of friction. Based on the circulation method, they are divided into internal circulation and external circulation.
The ball screw has a three-part structure. (Source: Huajing Industry Research Institute)
Internal and external circulation ball bearings are suitable for different scenarios. Structurally, external circulation ball bearings return to the nut and re-enter the cycle after the cycle is complete via a helical groove or tube on the outer surface of the nut. This process is relatively simple, easy to manufacture and maintain, has a larger radial dimension, and can handle high loads, making it suitable for high-load transmission systems such as heavy machinery and certain industrial automation equipment. Internal circulation ball bearings remain inside the nut throughout the cycle. They achieve a single, closed-loop circulation through a reverser. This process is more complex, with a compact radial structure, resulting in higher motion efficiency and positioning accuracy. It is suitable for high-precision, high-efficiency, high-reliability, and low-to-medium speed scenarios, such as machine tools and motion control for automotive and aircraft components.
Left image: Schematic diagram of external circulation; Right image: Schematic diagram of internal circulation. Source: Novo Precision.
Planetary roller screw
Planetary roller screws rely on the rotation of the screw and rollers to drive the nut in linear motion. The structure of a planetary roller screw is similar to that of a ball screw, including a screw, planetary rollers, a cage, an internal gear, and a nut, etc., but the rolling element is the planetary roller, not the balls in a ball screw.
The working principle of a planetary roller screw is similar to the orbit of planets around the sun in our solar system. The screw is analogous to the sun, the planetary rollers to the planets, and the nut to the orbits in the solar system. The screw's active rotation drives the rollers to revolve around the screw's axis while simultaneously rotating on their own axes, thus causing the nut to move axially in a linear motion. The planetary roller screw generates line contact rolling friction through the meshing rollers, significantly increasing the contact and force-bearing surfaces during the screw transmission process. Compared to ball screws used in precision transmissions, it offers high speed, high load capacity, high rigidity, a wide lead range, smaller size, lower noise, and easier maintenance and disassembly, all without significant loss in transmission efficiency.
Planetary roller screw structure diagram, source: Deng Qi, "Current Application Status of Planetary Roller Screw Electric Cylinders"
Planetary roller screws offer superior performance compared to ball screws. Ball screws use balls as load-transmitting elements, resulting in point contact; while planetary roller screws use threaded rollers, resulting in line contact. Therefore, planetary roller screws offer advantages such as high load capacity, impact resistance, small size, and high speed. They are currently used in high-tech fields globally, including aerospace, weaponry, and nuclear power, and also have wide applications in civilian sectors such as machine tools, precision robots, automotive ABS systems, and petrochemicals.
Advantage 1: Greater load-bearing capacity and lifespan
High load capacity: Because planetary roller screws use line contact, they can provide higher load capacity under the same conditions compared to the point contact of ball screws.
High rigidity and impact resistance: The planetary roller screw design provides higher rigidity while maintaining good impact resistance.
Long lifespan: According to Hertz's pressure law, the lifespan of planetary roller screws can be up to 15 times that of ball screws. This means that under the same working conditions, planetary roller screws have a longer maintenance cycle and higher reliability.
Advantage 2: Flexible lead and pitch, small size, and space-saving.
Flexible lead and pitch: Planetary roller screws can be designed with smaller leads, which can be integers or decimals, providing finer control.
Space saving: Planetary roller screws are smaller in size while providing the same load, which helps to reduce the overall size of mechanical equipment and make the design more compact.
Advantage 3: Higher speed and acceleration
High rotational speed and acceleration: Due to the non-recirculating design of the rollers, planetary roller screws can achieve higher rotational speeds and accelerations, which is crucial for systems requiring rapid response.
High linear speed and high input speed: Planetary roller screws can achieve higher linear speeds (up to 2000 mm/s) and input rotational speeds (up to 5000 rpm or higher) to meet the needs of high-speed operation.
Despite the advantages mentioned above, planetary roller screws are generally more expensive to manufacture and have higher technological barriers than ball screws. Therefore, the choice between planetary roller screws and ball screws requires a comprehensive consideration of specific application requirements, cost budget, and maintenance capabilities.
Ball screw classification: Based on the different structural components and motion relationships of planetary roller screws, planetary roller screws can be divided into five types: standard type, reverse type, circulating type, differential type, and bearing type.
1) Standard type: also known as non-circulating roller screw. The screw usually serves as the power input end and rotates only around its own axis; the nut is usually connected to the load and moves only along its own axis; the rollers perform planetary motion and axial movement between the nut and the screw under the action of the screw; the internal gear ring is fixed to the nut, and the end teeth of the rollers mesh with the internal gear ring to ensure that the rollers roll on the nut. The relative axial displacement between the rollers and the nut is zero, and they move axially together with the nut.
2) Reverse type: The functions of the nut and screw are reversed, resulting in a more compact structure suitable for short strokes and integrated design applications. The working principle is the same as a standard roller screw, but the functions of the nut and screw are opposite to those of the rollers. The rollers move axially within the nut, which is stretched to allow the full stroke of the drive shaft, achieving higher rated loads with a smaller lead and high space utilization. However, the stroke is limited by the thread length of the nut. Tesla's Optimus currently uses a reverse planetary roller screw.
3) Circulating type: The circulating roller design is suitable for high-precision, medium-to-low-speed operating scenarios. In a circulating roller screw, the rollers move axially within the nut until they rotate one revolution around the screw thread and return to their original position. Due to the minimum pitch and circulating roller design, very high positioning accuracy, resolution, and extremely high load capacity can be achieved.
4) Differential type: It has differential motion characteristics, smaller lead, and is suitable for working scenarios with large transmission and high load. The differential planetary roller screw adopts a segmented ring groove structure, which has differential motion. It can obtain a smaller lead and a larger reduction ratio than ordinary planetary roller screws. Moreover, due to its compact structure, the electromechanical actuator can have a higher power-to-volume ratio and power-to-weight ratio.
5) Bearing ring type: The structure is complex and the manufacturing cost is high. It is suitable for working scenarios with extremely high load-bearing capacity requirements. By adding components such as roller bearings, end caps, and housings, the load-bearing capacity is large and the wear rate is greatly reduced under high loads. However, its structure is complex and the manufacturing cost is high.
The difference between a reverse planetary roller screw and a standard planetary roller screw lies in the nut's function as the power input component, rotating around its own axis, while the screw acts as the actuator, moving axially. Gears are added at both ends of the screw to replace the internal gear ring, meshing with the roller end teeth to ensure the rollers roll on the screw. There is no relative axial displacement between the rollers and the screw; they move axially together. In a reverse planetary roller screw, the nut is the driving component, and the screw is the output component. There is no relative axial displacement between the rollers and the screw. It is mainly used in applications with small to medium loads, short strokes, and high speeds. Its biggest advantage is that the nut can be used as a motor rotor, achieving an integrated design of the motor and screw, forming a compact, integrated electromechanical actuator. This design does bring additional engineering challenges, the biggest being the machining of the nut's internal thread. In a standard planetary roller screw, the screw is fixed and the nut moves; in a reverse planetary roller screw, the nut is fixed and the screw moves. Since the length of the nut in a reverse planetary roller screw is much greater than that in a standard screw, machining threads within such a long nut is a challenge, requiring precise machining techniques and high-quality control.
Left image: Standard planetary roller screw structure; Right image: Reverse planetary roller screw structure. Source: "Precision Analysis and Design of Planetary Roller Screw Transmission" by Ke Hao, "Planetary Roller Screw Design" by Wang Jiajian
Planetary roller screws are a core component of the "limbs" of humanoid robots, widely used in the arms, legs, and dexterous hands of robots to provide precise linear motion control. The Tesla humanoid robot Optimus uses 14 rotary joints, 14 linear joints, and 12 hollow cup joints in its hands. The linear joints utilize 14 reverse-type planetary roller screws (2 at the elbow, 4 at the wrist, and 8 in the legs). These screws come in three specifications: 500N, 3900N, and 8000N, to accommodate the different load-bearing requirements of each joint.
Optimus linear articulated lead screw, source: Tesla Robotics 2022 AI Day
Tesla's use of reverse/reverse planetary roller screws in its humanoid robot Optimus is likely based on their performance advantages, especially in terms of load-bearing capacity and stiffness. However, it's possible that lower-cost ball screws might be used for humanoid robots with lower load-bearing requirements.
Typical application scenarios and market distribution of lead screws
The widespread application and market demand for lead screws across various industries are further elaborated below, focusing on application scenarios in new energy vehicles, machine tools, and humanoid robots:
1. Applications in New Energy Vehicles: With the development of vehicle electrification and intelligence, the application of lead screws in the automotive field is constantly deepening, such as in automotive wheel-side brake-by-wire systems (EMB), rear-wheel steering systems (iRWS), steer-by-wire systems (SBW), suspension systems, and adjustment and control devices for automotive components.
2. Applications in the Machine Tool Industry: Lead screws are one of the core standard components of machine tools. Machine tools include rotary axes and linear axes. Linear axes consist of lead screws and guide rails, enabling precise positioning and movement of the workpiece. Traditional machine tools mainly use trapezoidal/sliding lead screws. CNC machine tools, based on traditional machine tools, incorporate digital control systems, requiring higher precision in workpiece transmission, and currently mostly use ball screws. In the global machine tool supply chain, most machine tool manufacturers tend to manufacture spindles, swivel heads, rotary tables, and other functional components in-house due to customization or differentiation considerations. However, rolling functional components are almost entirely outsourced. With the upgrading of the machine tool industry, the demand for rolling functional components is expected to continue to grow, which is highly certain.
3. Applications in Humanoid Robots: Humanoid robot actuators fall into two categories: hydraulic and electric. While hydraulic mechanisms offer superior performance, their higher cost and maintenance requirements limit their current use. Electric actuators are the mainstream choice. Planetary roller screws, with their high load-bearing capacity, are the core component of linear actuators in humanoid robots, enabling precise control of the robot's joints. This technology has been adopted by companies such as Tesla overseas, the LOLA robot from the University of Munich in Germany, and domestically by companies like Ligong Huahui and Kepler.
In the global ball screw market, Japanese and European companies account for approximately 70% of the market share, with the top five (CR5) holding about 46%. The Asia-Pacific region is the primary application area, with a market share of 49.46% (data from Zhiyan Consulting). Major ball screw manufacturers include Japanese companies NSK and THK, German companies Bosch Rexroth and Schaeffler, and Swedish companies Ewellix. There are numerous domestic manufacturers of rolling components, but their products are concentrated in the low-to-mid-end market, and their technological level lags behind that of foreign companies. Domestic manufacturers include Taiwanese companies HIWIN and Yintai, as well as mainland Chinese companies Nanjing Craft and Qinchuan Machine Tool. Looking specifically at the Chinese market, according to information from a metalworking public account, in the high-end market for rolling functional components, Japanese and European companies together hold a 90% market share, while mainland Chinese and Taiwanese companies each hold approximately 5%, indicating a relatively concentrated high-end market structure. In the low-to-mid-end market for rolling functional components in China, mainland Chinese manufacturers hold approximately 30% of the market share.
For planetary roller screws, the domestic market is currently dominated by foreign manufacturers. Leading foreign manufacturers Rollvis (Switzerland), GSA (Switzerland), and Ewellix (Sweden) hold market shares of 26%, 26%, and 14%, respectively. While domestic companies lag behind foreign companies in core planetary roller screw technologies, they are gradually catching up in performance aspects such as lead accuracy, maximum dynamic load, and maximum static load. The combined market share of domestic planetary roller screw manufacturers is 19%.
Typical foreign ball screw companies
1. Schaeffler
Schaeffler's ball screws and planetary roller screws are widely used in the automotive, semiconductor, industrial robotics and automation, petrochemical and other fields.
Leveraging the precision machining capabilities of its mold-making division, the Schaeffler Group began mass production of roller screw drives in 2009, marking the beginning of a new direction for the company in the chassis sector. Roller screws have become an essential component in many chassis applications.
In 2022, the Schaeffler Group acquired Ewellix, a leading global manufacturer and supplier of drive and linear motion solutions. The addition of Ewellix significantly boosted Schaeffler's planetary roller screw division, giving it a more comprehensive portfolio of roller screws with varying performance and specifications.
2. SKF (SKF)
Founded in Gothenburg, Sweden in 1907, it is currently a global leader in bearing manufacturing and innovation. While focusing on the development, design and manufacturing of bearings, seals and lubrication systems, it also provides machine condition assessment, reliability engineering design and remanufacturing services, providing customers with a full-ecosystem one-stop service.
Currently, SKF's ball screw product series mainly includes precision rolled ball screws, ground ball screws, and roller screws.
3. NSK
Founded in 1916, NSK is Japan's first and largest bearing manufacturer. Leveraging the precision machining technology honed through bearing production, NSK has expanded its business to include industrial machinery bearings, precision machinery and components, as well as automotive bearings and components.
In ball screw manufacturing, NSK currently holds the second-largest market share globally, with its R&D capabilities and product advancements leading the world. Its main applications include machine tools, injection molding machines, and general machinery, as well as specialized applications such as semiconductor and LCD manufacturing equipment. In R&D and product innovation, NSK pioneered the development of a low-friction torque ball screw for energy regeneration and coordinated braking systems in EV/hybrid vehicles, and developed the world's largest high-load-capacity ultra-large ball screw.
4. THK
Founded in 1971, the company opened its China R&D center in 2010. It was the world's first company to develop a linear motion method using rolling contact, and also the world's first to develop and commercialize linear motion (LM) guides. Currently, it is the world's largest ball screw manufacturer.
5. HIWIN
Founded in 1989 and listed on the Taiwan Stock Exchange in 2009, HIWIN has become a global professional manufacturer of drive control products and system technology products. HIWIN ball screws offer a variety of precision grades to meet different application needs, with JIS C0-C7 being the primary precision grades.
6. Rexroth
Rexroth, a subsidiary of the Bosch Rexroth Group, is a large industrial products company primarily manufacturing hydraulic systems, gearboxes, electrical control technology, and mechatronics products. In the field of linear motion technology, Rexroth offers linear guides, ball and roller screws, screw drives, electric cylinders, and linear motion modules. Its roller screws are a relatively new product launched within the last decade, employing rolling technology to meet the needs of customers seeking higher economic efficiency, but they are unsuitable for applications requiring high precision and long lifespan. Its main product is the PLSA planetary roller screw drive system, also used in its electromechanical actuators, but the range of available diameters is relatively small, and its product portfolio is less comprehensive than that of Schaeffler and SKF.
7. Moog
Founded in the United States, Moog is a leading global integrator of precision motion control systems, primarily serving the aerospace, defense, and industrial manufacturing sectors. In industrial machinery, Moog offers a range of products including motors, servo valves, electrostatic pumps, and ball screws. Among these, ball screws include ball screws, planetary roller screws, and inverted roller screws, with over thirty years of experience in the production and design of customized high-precision planetary roller screws. They offer a variety of diameters, pitches, and lengths, featuring high load capacity and high start-up speeds. Their screws are mainly used in metal forming and stamping machinery; they do not currently produce dedicated roller screws for humanoid robots or similar applications.
Typical domestic ball screw enterprises
Currently, domestic ball screw manufacturers are relatively small in scale, and their products are mainly mid-to-low-end. With new competitors entering the market, the industry is expected to enter a stage of high-quality development.
1. Hanjiang Machine Tools
Hanjiang Machine Tool is a key project of the Third Front construction during the Third Five-Year Plan period, a large-scale backbone enterprise in the machinery industry, and a leading domestic manufacturer of thread grinding machines. The company's main products include machine tools and rolling functional components, including ball screw pairs, rolling linear guide pairs, rolling guide blocks, ball splines, ball guide sleeves, precision cross tables, self-locking devices, linear modules, precision roller cross guide pairs, and precision needle roller cross guide pairs. With 50 years of design and manufacturing experience, the company possesses a complete range of rolling functional component processing equipment in terms of specifications, quantity, and precision, as well as advanced thread testing instruments and comprehensive precision testing instruments for rolling linear guides. It has an annual production capacity of 200,000 pairs of various ball screws and 100,000 meters of ball linear guides.
2. Nanjing Craft
Nanjing Craft has a 70-year history of research and manufacturing in the field of rolling functional components. Its products are used in large quantities for high-speed, high-precision, and high-end CNC machine tools, promoting the upgrading of domestic rolling functional components and the substitution of imports.
Nanjing Craft's current products include rolling guides, ball screws, rolling splines, planetary roller screws, and CNC precision worktables.
3. Dingzhi Technology (Jiangsu Leili)
Founded in 2008, the company is a provider of customized precision motion control solutions, primarily based on micro-motors. Currently, its main products include linear actuators, hybrid stepper motors, and DC motors, which are widely used in medical devices, robotics, precision electronic equipment, and other industrial automation fields.
The company's linear actuators include sliding screw linear actuators, ball screw linear actuators, and permanent magnet motor linear actuators. The company currently manufactures all its screw nuts in-house, including design, processes, molds, and injection molding, achieving domestic leadership in efficiency and noise reduction. The company has also achieved a milestone in the research and development and production of miniature planetary roller screws.
4. Guangdong Kaitai Precision Machinery
Founded in 1993, the company's products include linear modules, linear guides, clamps, ball screws, etc., and it has more than 20 years of industry manufacturing experience.
5. Shandong Bote Precision Machinery
Formerly known as Shandong Jining Screw Factory, it was founded in 1966 and is a national high-tech enterprise and a leading specialized manufacturer of rolling functional components in China. With over 50 years of manufacturing experience, the company has been dedicated to the research and production of rolling functional components. It is a key drafting unit for my country's standards for rolling functional components (ball screw pairs and linear guide pairs), a key drafting unit for the national high-speed spindle standard, the leader unit of the national ball screw pair standard working group, and the vice-chairman unit of the China Machine Tool & Tool Builders' Association.
The company's main products include ball screws, linear guides, CNC worktables, electric spindles, mechanical spindles, hydrostatic spindles, and trapezoidal screws. The company holds the number one market share nationwide for precision spindles and spindle units, ranks among the top three in the national market for ball screw assemblies, and its trapezoidal screws are the only product nationwide recognized as a ministerial-level superior product. Its "high-speed precision electric spindle" and "high-speed precision ball screw assembly" have been recognized by the Ministry of Science and Technology as "National Torch Program Key New Products."
6. Qinchuan Machine Tools
As a leading enterprise in the machine tool industry, it possesses the capability to produce high-precision thread grinding machines; relying on advanced machine tools, it has taken the lead in deploying the production of high-precision rolling screws and guideways, giving it a significant competitive advantage.
7. Hengli Hydraulics
Founded in 2005, this leading company in the hydraulic industry started with hydraulic cylinders and has diversified its business into cylinders, castings, and hydraulic components. From manufacturing hydraulic cylinders, the company has grown into a large-scale comprehensive enterprise encompassing the research and development and manufacturing of products such as high-pressure cylinders, high-pressure piston pumps, hydraulic multi-way valves, industrial valves, hydraulic systems, hydraulic test benches, and high-precision hydraulic castings.
In 2021, the company raised no more than 5 billion yuan through a private placement, of which 1.4 billion yuan was invested in the linear actuator project. Upon completion, the project will have an annual production capacity of 104,000 standard ball screw electric cylinders, 4,500 heavy-duty ball screw electric cylinders, 750 planetary roller screw electric cylinders, 100,000 meters of standard ball screws, and 100,000 meters of heavy-duty ball screws.
8. Best
Founded in 1997, the company's main business is the research, development, production, and sales of various precision parts and tooling fixtures. In 2022, it established a wholly-owned subsidiary, Wuxi Yuhua Precision Machinery Co., Ltd., to comprehensively develop linear rolling functional components. Its main products include high-precision ball screw pairs and high-precision rolling guide pairs, targeting the high-end machine tool field, the semiconductor equipment industry, and the automation industry for vigorous expansion.
9. Changsheng Bearings
Founded in 1995, the company is a high-tech enterprise specializing in the research, development, production, and sales of self-lubricating bearings. In recent years, Changsheng Bearing has also made significant progress in the field of ball screws, making ball screw business a new highlight for the company. Changsheng Bearing's ball screw products are mainly used in commercial vehicle transmissions, passenger car braking, steering, and parking systems.
10. Heng Erda
Founded in 1995, the company is a leading enterprise in the cutting tool industry, primarily engaged in the research, development, production, and sales of metal cutting tools and related intelligent CNC equipment, as well as high-precision rolling components. The company's heavy-duty die-cutting tools hold the number one market share both internationally and domestically; its sawing tools boast superior performance, meeting or exceeding international and national standards, making it a major manufacturer in the bimetal band saw blade sector.
Since metal heat treatment and processing technology have the same origin, the company has entered the production of high-precision rolling functional components based on its many years of manufacturing experience. High-precision linear guides have entered the industrialization process, and the company continues to expand production lines for components such as ball screws.
11. Southern Precision Engineering
Nanfang Precision Machinery Co., Ltd. is a professional manufacturer and developer of bearings and related components for the transmission industry. The company primarily produces needle roller bearings, one-way clutches, and one-way pulley assemblies, and its products are supplied to numerous Fortune 500 companies and many other well-known global enterprises. Its ball screw products are currently mainly used in the automotive industry.
12. Inovance Technology
Founded in 2003, the company focuses on the R&D, production, and sales of industrial automation control products, targeting high-end equipment manufacturers. In May 2023, Inovance Technology officially completed the acquisition of SBC Linear Co., Ltd. of South Korea. The company's main products include ball guides, roller guides, rolled screws, and material handling slides. Its products rank among the top in the industry in terms of precision retention, noise, and rigidity.
13. New Year's Greetings Across the World
The company primarily manufactures high-end precision components such as bearings and automotive parts. Its main products include bearings, bearing rings, wind turbine rollers, and automotive parts. The company also has the capability to manufacture ball screw nuts. It has successfully developed RV reducer bearings and harmonic reducer flexible bearings, and has sent samples to well-known robot reducer companies. It has successfully developed ball screw nut steering system bearing assemblies and has the capability to produce ball screw system components. Products are mainly used in new energy vehicle steering systems, electronic braking and parking systems, transmissions, and active suspension systems.
14. New Sword Transmission
Founded in 1999, the company's main business is providing worm gear and worm drive components and precision parts to industries such as semiconductor communications, computers, electronics, automobiles, construction machinery, human-machine collaboration, and service robots. A research and development center was established in 2005, and a branch laboratory of the R&D center (Shanghai) was established in 2015, focusing on mechanical transmission technology and artificial intelligence application integration technology.
The planetary roller screw electric cylinder production line series is the company's latest R&D product, which entered mass production in 2022. This product is the first of its kind in the province, representing a crucial technology for replacing imported components and poised to become the main technological alternative for hydraulic drives and ball screw electric cylinders. It is widely used in industries such as automobiles and humanoid robots. The company has built the first mass production line for planetary roller screws in China, which began mass production in March 2022, and has a production capacity of 3.5 million sets. It has also been first applied in the automotive industry.
15. Ningbo Cixing
2018 年慈兴集团设立宁波慈兴汽车轴承与滚珠丝杆研究院，核心研究开发方向为高端汽车轴承、新能源汽车用轴承、车用滚珠丝杆组件等。2022 年公司年产能为6亿套轴承，500万只滚珠丝杠。
