There are substantial differences between rolled ball screws and ground ball screws in terms of processing methods, precision, performance, application scenarios, and costs. The specific analysis is as follows:
Processing Methods and Processes
Rolled Ball Screws: Metal billets are directly extruded through rollers, utilizing plastic deformation to form threads. This process is straightforward and enables mass production. However, accurately controlling the thread shape during rolling is challenging, resulting in limited precision. The ball contact surface features an irregular polished finish, and the coaxiality between the shaft diameter and the spiral groove at the bearing installation point is low. Consequently, it relies heavily on the assembly technician's experience for adjustment, making it difficult to ensure high precision consistently.
Ground Ball Screws: Threads are ground using an ultra-precision thread grinder, with stringent control over all stages, from raw material selection to heat treatment and processing inspection. Multiple heat treatment processes are employed during manufacturing to eliminate internal stress and guarantee thread shape accuracy and surface quality. In the final process, the shaft diameter and thread raceway exhibit high coaxiality, minimizing repeated positioning errors.
Precision and Performance
Precision Level:
Rolled Ball Screws: Precision typically ranges from C7 to C10, with a lead error of approximately 0.05 mm and an axial clearance of 0.05–0.17 mm. While some high-end products can barely reach C5 precision, the coaxiality issue continues to constrain their overall accuracy.
Ground Ball Screws: Precision can achieve levels from C0 to C5, with a lead error of only 4–23 μm and an axial clearance of 0.01–0.03 mm. High-precision products can meet the demands of extreme scenarios, such as optical equipment and semiconductor processing.
Performance Difference:
Rolled Ball Screws: They have low surface hardness, poor wear resistance, and a significant decrease in precision after prolonged use. Additionally, they generate high noise levels and are suitable for low-speed rotation (preferably with an input speed below 900 rpm).
Ground Ball Screws: They feature high surface hardening hardness (HRC 58–63), strong wear resistance, and excellent precision retention. They produce low noise levels and are suitable for medium- to high-speed rotation (with a DN value reaching up to 70,000 and even 130,000 in heavy-load scenarios).
Application Scenarios
Rolled Ball Screws: They are suitable for scenarios with low precision requirements, such as general machine tools, automation devices, and general instruments. Their low cost and fast delivery time (2–3 weeks) make them ideal for projects with limited budgets or those insensitive to precision.
Ground Ball Screws: They are widely used in high-precision, high-speed, high-frequency, and high-load scenarios, such as high-speed machine tools, dynamic measuring devices, precision instruments, and aerospace equipment. Their high precision and long service life ensure the long-term stable operation of the equipment.
Cost and Delivery Time
Rolled Ball Screws: They are priced low, with the cost being only one-sixth of that of ground products for the same length and diameter. Their short delivery time (2–3 weeks) makes them suitable for rapid iteration or emergency needs.
Ground Ball Screws: They have high manufacturing costs, requiring precision equipment and complex process support. Their delivery time is long (more than three months), but they can be customized into non-standard nuts, screws, and other special parts to meet personalized needs.
Selection Suggestions
Prefer Rolled Ball Screws: If the project does not require high precision (such as C7 or above), has a limited budget, or necessitates fast delivery, rolled products are a more cost-effective choice.
Prefer Ground Ball Screws: If the project demands high precision (below C5), high speed, long life, or extreme environmental adaptability (such as high temperature or high load), ground products can provide more reliable protection.