DLY’s Early Breakthrough in Large-Diameter Cold-Rolled Ball Screws

Project date: 2011. This company milestone was published retrospectively.

In 2011, Zhejiang DLY Automation Manufacturing Co., Ltd. completed the development of a Φ80 × 10 mm, 10-meter cold-rolled ball screw for large-scale, heavy-duty transmission applications.

The project represented an important milestone in DLY's development of large-diameter and ultra-long ball screws. It also formed part of the company's broader strategy of developing both large-load transmission components and smaller precision linear motion products.

The experience gained through the project subsequently supported DLY's continued development of ball screw assemblies, linear guideways and linear shafts for machine tools and industrial automation.

The Market Challenge in 2011

More than a decade ago, large-diameter, heavy-duty cold-rolled ball screws were difficult to manufacture and were not widely available from domestic suppliers.

According to DLY's project records from that period, imported large-scale ball screw assemblies could cost nearly RMB 100,000 per set. The high purchasing cost and limited availability created challenges for customers requiring long, large-diameter transmission components.

Against this background, DLY decided to begin an independent development project rather than continue relying entirely on imported products.

The Φ80 × 10 mm, 10-Meter Development Target

The development target was a cold-rolled ball screw with a nominal diameter of 80 mm, a 10 mm lead and an overall length of approximately 10 meters.

A product of this size creates manufacturing challenges that are significantly different from those involved in producing conventional smaller-diameter ball screws. Material preparation, straightness, rolling stability, heat treatment and handling become increasingly difficult as the diameter and length increase.

Large-diameter ball screws may be used in equipment requiring long travel, high axial load capacity or the controlled movement of large mechanical structures. Potential application areas include:

• Large gantry machine tools
• Heavy lifting and hoisting equipment
• Hydropower gate operating systems
• Large forging and forming equipment
• Shipbuilding and heavy industrial machinery
• Cable winding and winching equipment
• Other long-stroke, high-load transmission mechanisms

Final product selection for these applications must still be based on the actual axial load, speed, stroke, duty cycle, mounting arrangement, safety factor and environmental conditions.

Manufacturing Challenges of the Large Ball Screw

Producing an ultra-long, large-diameter cold-rolled ball screw required DLY to address multiple technical challenges throughout material preparation, rolling, heat treatment and nut matching.

• Material performance: The steel needed suitable strength, consistency, density and elongation for the rolling process.
• Roller development: The rolling tools and profile parameters had to match the large thread geometry.
• Ultra-long blank preparation: Machining and handling a blank approximately 10 meters long required specialized process control.
• Rolling stability: Roundness, thread formation and the risk of surface cracking had to be controlled during rolling.
• Heat-treatment deformation: Shrinkage, residual stress, straightness and hardness had to be managed after heat treatment.
• Deep raceway finishing: The long and deep helical raceway required customized polishing methods and equipment.
• Ball nut matching: A corresponding ball nut and recirculation system had to be developed for the large screw shaft.

More Than 300 Meters of Trial Rolling

DLY assembled a dedicated research and development team for the project. The team repeatedly adjusted the material condition, roller profile, rolling parameters, temperature control and subsequent finishing processes.

During development, more than 300 meters of material were used for trial rolling. The project required over 90 days of intensive development and testing before the team achieved the required thread formation and process stability.

Each trial helped the team identify problems involving surface condition, dimensional consistency, deformation and matching between the screw shaft and ball nut. The results were then used to revise the next round of processing parameters.

Seven Key Technologies Developed during the Project

The development process focused on seven closely connected manufacturing technologies:

1. Selection and testing of high-strength steel
2. Roller design and rolling-parameter optimization
3. Machining and handling of the ultra-long blank
4. Cold-rolling process optimization and temperature control
5. Heat treatment, shrinkage control and residual-stress management
6. Deep-thread polishing with customized equipment
7. Development of the matching ball nut and recirculation mechanism

These technologies could not be addressed independently. Changes to material condition or rolling parameters also influenced heat-treatment deformation, raceway finishing and the final matching condition of the ball nut.

Recorded Results of the Development Project

According to DLY's original project records, the completed Φ80 × 10 mm, 10-meter cold-rolled ball screw achieved the following measured results:

The first completed assembly was subsequently used in an operating application. According to the feedback recorded by DLY at the time, the ball screw operated steadily under the applicable working conditions.

From Development to Industrial Application

Following the completion of the project, large-scale cold-rolled ball screws were applied in several types of industrial equipment, including:

• Large gantry machine tools
• Industrial automation systems
• Hydropower gates and hoisting devices
• Shipbuilding and heavy machinery
• Cable winding and winching equipment

Feedback collected by DLY from the applicable projects indicated improvements in service life, startup torque, operational stability and transmission efficiency compared with the previously used solutions.

These results were specific to the relevant equipment and operating conditions. Actual ball screw performance depends on load, alignment, lubrication, mounting, speed, duty cycle and environmental conditions.

Cold Rolling and Long Ball Screw Manufacturing

Cold rolling forms the ball raceway through controlled plastic deformation rather than removing material through thread grinding. The process can provide efficient production and favorable material-flow characteristics when the material, tooling and process parameters are properly controlled.

However, cold-rolled and ground ball screws serve different accuracy, cost and application requirements. Cold rolling does not automatically guarantee longer life or higher strength in every application, and producing an ultra-long cold-rolled screw is still limited by material availability, equipment capacity, heat treatment and straightness control.

The correct manufacturing method should therefore be selected according to the required accuracy grade, load, speed, stroke, rigidity, service life and project budget.

Looking Back More Than a Decade Later

The 2011 project demonstrated that a privately operated manufacturing company could address a difficult technical requirement through repeated testing, process development and close cooperation among its employees.

For DLY, the significance of the project extended beyond one large ball screw. The work strengthened the company's experience in rolling technology, heat-treatment control, ultra-long component processing and ball nut development.

More than a decade later, this milestone continues to represent DLY's approach to technical development: identify the practical problem, test the process, improve the details and turn a difficult requirement into a manufacturable product.

Continued Development at DLY

Since the completion of the large-diameter cold-rolled ball screw project, DLY has continued to develop its manufacturing capabilities in several areas:

• High-load and long-lead ball screws
• Long linear guideways and linear shafts
• Precision transmission components for industrial automation
• More efficient and controlled manufacturing processes

Founded in 2005, Zhejiang DLY Automation Manufacturing Co., Ltd. manufactures ball screws, linear guideways, linear shafts and related linear motion components for machine tools and industrial automation.

Customers requiring a large-diameter, long-stroke or customized ball screw can provide drawings, dimensions, loads, speeds, installation details and operating conditions for technical review.

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