How to Eliminate Backlash in Ball Screws | Causes & Preload Solutions

In precision motion systems, the ball screw plays a vital role in converting rotary motion into linear motion.

It is widely used in CNC machinery, automation equipment, and measuring instruments.

However, during operation, one common issue known as backlash often occurs - a small but critical factor that directly affects positioning accuracy and repeatability.

Understanding and eliminating backlash is essential for ensuring stable and precise linear motion.

eliminate-backlash-in-ball-screw

Backlash refers to the lost motion that occurs when the rotational direction of a ball screw reverses, and the ball nut does not immediately follow the screw's movement.
This phenomenon results from the clearance between the balls and the contact grooves of the screw and nut. Although this gap is usually very small, in high-precision or frequent reversing applications, it can lead to noticeable positioning deviation, vibration, or noise.

During production, small dimensional deviations between the ball diameter and groove curvature can result in clearance between components.

Continuous operation causes wear between the balls and raceways, which gradually increases the axial gap.

When the lead-to-diameter ratio is too large, the rolling motion becomes unstable, making it difficult to eliminate clearance.

Temperature variations can affect material dimensions and contact states, especially in high-speed or high-temperature environments.

Reduced Positioning Accuracy and Repeatability – Lost motion during reversal directly decreases motion precision.
Vibration and Noise – Loose contact between balls and grooves causes impact and resonance.
Accelerated Wear – Uneven load distribution leads to localized wear, which further worsens backlash.
Lower Servo Responsiveness – Backlash negatively affects the response and stability of servo-driven systems.

To eliminate backlash in ball screws, engineers can adopt several effective methods depending on the precision requirements and application conditions.

At the manufacturing stage, factories can adjust ball diameters to reduce or eliminate clearance.
For example, in small-lead, large-diameter models (like 5×25 mm), precisely matching ball size can achieve near-zero backlash or even preload.
This method is cost-effective and works well for small-lead ball screws, but for larger leads, the rolling motion tends to become rough and unstable, making this method less suitable.

When all the clearance inside the nut is eliminated by applying axial preload, the ball screw assembly is known as a preloaded ball screw.
The preload ensures the balls contact both sides of the raceway simultaneously, completely removing backlash and improving rigidity.

Common preload methods include:

Single Nut with Differential Ball Size – Slightly different ball diameters create an internal interference fit.
Double Nut Preload System – Two nuts are axially offset using a spacer or spring mechanism, pressing each nut against opposite sides of the raceway.

An adjustable preloaded ball nut uses two ball nuts connected by a spring assembly.
The spring pushes one nut against the left side of the screw groove and the other against the right, creating a constant axial force.
A threaded adjusting ring can fine-tune the preload tension between the nuts, allowing customization for different applications.
This design also enables the nut and screw to be purchased separately while still achieving precise preload after assembly - ideal for maintenance and flexible installation.

Maintain proper lubrication to prevent metal-to-metal contact.

Ensure accurate alignment and support stiffness during installation to prevent extra vibration or offset.

Replace worn balls or nuts promptly to avoid increasing backlash over time.

Even though backlash appears minimal, its effect on motion accuracy and machine performance can be significant.
To achieve smooth, rigid, and high-precision transmission, it is essential to control backlash at every stage - from design and production to installation.
By combining precision ball selection, proper preload structures, and professional assembly, backlash can be effectively minimized or completely eliminated, ensuring long-term stability and repeatable accuracy in your automation systems.

✅ Looking for a Reliable Ball Screw Manufacturer?

At DLY Automation, we specialize in precision ball screw assemblies with customizable preload solutions to meet different accuracy and load requirements.
With over 20 years of manufacturing experience, advanced inspection equipment, and a full in-house production chain, we provide consistent quality at competitive factory prices.

Get in touch with DLY now

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