Ball Screw Drive

The play between the ball screw and the nut—known as axial play—has a significant impact on positioning accuracy and smoothness of operation. Excessive play leads to backlash, reduces precision, and can cause vibrations, while insufficient play or excessive preload increases friction and accelerates wear.
Therefore, the clearance must be designed to achieve an optimal balance between accuracy, smoothness, and service life. In high-precision applications, preloadable ball screw nuts are often used to specifically minimize clearance.

The service life of a lead screw depends on several factors. The loads acting on the system—including their magnitude, direction, and frequency—influence the stress on the thread flanks. Speed, acceleration, and operating cycles affect wear and fatigue. Lubrication and cleanliness are critical, as insufficient lubrication or contamination can increase friction and damage the surface.
In addition, the material, hardness, precision, and fit of the lead screw and nut, as well as temperature and environmental conditions, play a role.
All these factors must be taken into account during design to ensure a long, reliable service life.

If the nut can be customized to meet your specific requirements, it can be adapted to the application and the available installation space. This allows the installation configuration, interfaces, fasteners, and additional functions to be precisely tailored, which reduces assembly time and eliminates the need for additional components. In addition, stiffness, preload, seals, and lubrication concepts can be specifically designed to improve the performance, service life, and reliability of the lead screw drive.

A driven nut offers the advantage that the spindle itself remains stationary and only the nut is moved by a motor or drive, thereby reducing the mass that needs to be accelerated. This design results in higher dynamics, faster response times, and lower load capacity. At the same time, it allows for the use of long or heavy spindles, thereby facilitating integration into tight or complex machine-building environments. Furthermore, the direct drive force applied to the nut enables optimization of precision and positioning accuracy.

A driven nut is a good choice when high dynamics, rapid acceleration, or long spindles are required. Since the spindle is stationary and does not need to rotate, inertia, vibrations, and critical speeds are significantly reduced. This design is particularly advantageous in limited installation spaces, for long travel distances, at high speeds, or when precise positioning is required at high speeds.

A thread is measured correctly by determining the pitch, outside diameter, center diameter, and profile angle. First, the outside diameter of the screw or the inside diameter of the nut is measured using a micrometer or a vernier caliper. Next, the pitch is determined—that is, the distance between two adjacent threads—usually with a thread gauge or visually under a microscope. For exact profile tolerances and angle forms, thread profilometers, thread testers, or optical measuring systems can be used.
It is important to control cleanliness, measurement direction, and temperature to obtain precise results.

The difference between right-hand and left-hand threads lies in the direction of rotation used to tighten or move them. A right-hand thread is tightened by turning clockwise and is the most commonly used type of thread. A left-hand thread, on the other hand, is tightened by turning counterclockwise and is used when a component would otherwise come loose due to the normal direction of rotation, or when a reverse motion is required.

A left-hand thread is used when a connection would loosen on its own due to the normal direction of rotation of a right-hand thread, or when a counter-rotational movement is required. Typical applications include rotating components with specific directions of rotation, safety screw connections, or systems in which two threads are designed to clamp or balance each other.

Ball screws are subject to internationally recognized standards such as ISO 3408 and the corresponding German DIN-ISO 3408 standards. These standards provide binding definitions of dimensions, tolerances, test procedures, and accuracy classes, thereby ensuring comparable and reproducible quality standards for precision ball screw systems worldwide.
The accuracy classes of ball screws primarily refer to pitch accuracy and are divided into classes C0, C1, C3, C5, C7, and C10. As a general rule, the lower the class number, the higher the positioning accuracy and repeatability.
Overview of typical accuracy classes:

C0 to C3: For high-precision applications, such as in machine tool manufacturing, metrology, or high-precision robot axes
C5 to C10: For robust and cost-effective applications in automation, conveyor, and positioning technology, where positioning accuracy requirements are less stringent.

In addition to pitch accuracy, form and position tolerances also play an important role. Among other things, they influence the smoothness of operation, concentricity, and the dynamic positioning performance of the ball screw. The corresponding limit values are specified in DIN ISO 3408; however, in practice, they are often supplemented by manufacturer-specific standards to achieve optimal performance and service life.
Kammerer Gewindetechnik manufactures ball screws in strict accordance with DIN and ISO standards while also meeting individual customer requirements—from development and design through to series production, for every accuracy class and every application.