BALL THREAD TECHNOLOGY
Ball Screw Drive
Technology
Through well-thought-out construction, modern manufacturing techniques and matched components, a ball screw technology is created th
Materials
The performance of a ball screw drive depends crucially on the choice of materials. Depending on the application, spindles and nuts can be manufactured from various materials. A wide range of options are available, from high-strength, hardened steels and wear-resistant bronze to corrosion-resistant stainless steel.
Our balls are made of either ceramic or 100Cr6 grade G5, depending on the application.
Raceway profile
Kammerer ball screw drives are fundamentally equipped with gothic raceway profiles and the maximum possible pressure angle ß. Additionally, the ball diameter is calculated for each respective application.
Advantages
- Optimal conformity ratios
- Highest load ratings and thus long service life
- Best running characteristics
- Efficiency at 98%
- Optimal rigidity
- Nearly constant drive torques
Effciency
The efficiency of a ball screw drive describes the ratio of output to input power and is a measure of the friction losses in the system.
It is primarily influenced by the lead angle and the friction angle. With increasing lead, the efficiency rises as the relative proportion of friction decreases. The friction angle in turn depends on the coefficient of friction between the balls, spindle, and nut.
Due to rolling friction, ball screw drives achieve very high efficiencies of typically 0.9 to 0.98. Due to the low friction, ball screw drives are already non-self-locking at small lead angles, making a reversal of the direction of movement necessary.
Preload (Axial Play)
The preload of a ball screw drive serves to deliberately reduce or completely eliminate the axial play between the spindle and nut. A preloaded ball screw drive increases axial rigidity, improves positioning and repeatability accuracy, and reduces backlash. The level of preload is adapted to the respective application, as it influences friction torque, efficiency, and service life.
Spindle
The spindle geometry has a direct influence on the achievable axial play. Lead tolerance, runout, and surface quality determine the uniformity of ball loading and the consistency of preload.
Nut
Through preloaded ball sets or double-nut concepts, the preload can be significantly influenced by the nut. The design and configuration define the preload force, the remaining axial play, and the friction behavior.
Deflectors
In our ball screw drives, we deliberately use individually adapted deflectors, so that we can precisely tune each one to the respective lead, regardless of the complexity of the requirements.
The result: Maximum smoothness of operation, optimized power transmission, and a significantly extended service life.
Lebensdauer
The service life of a ball screw drive is generally determined by the load rating of the ball raceway and the occurring loads. It describes the distance that the screw drive can travel under defined conditions before fatigue occurs at the rolling contacts.
The main factors for service life are: axial and radial loading, dynamic stress, lubrication, material quality, and manufacturing precision of the spindle and nut. Excessive loads or insufficient lubrication lead to increased wear and significantly reduce service life.
The service life can be estimated mathematically using the equivalent dynamic load rating and the achievable number of ball revolutions. Ball screw drives are characterized by high fatigue strength and, under optimal conditions, achieve travel distances of several thousand kilometers with precise guidance.
Questions
- What should be kept in mind regarding the play between the ball screw and the nut?
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. - What factors affect the service life of screw drives?
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. - How do I measure a thread correctly?
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.