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Backlash is the biggest enemy of precision linear motion. Uncontrolled reverse clearance will cause positioning deviation, repeated positioning errors and jitter during axis reversing. Almost all high-precision ball screws rely on preload structure to eliminate backlash.
This article systematically explains the three mainstream ball screw preload types on the market, analyzing their advantages, characteristics and applicable industrial scenarios to help engineers avoid inaccurate preload selection.
1. Double Nut Preload Structure
Double nut preload is the most classic and mature zero-backlash solution. It uses two ball screw nuts with spacing adjustment to generate pre-pressure, completely eliminating reverse idle stroke.
Advantages: Ultra-low backlash, high positioning repeatability, stable preload, suitable for long-term high-precision operation.
Disadvantages: Slightly larger volume, higher assembly precision requirements.
Applications: Precision testing equipment, micro-processing machines, high-end CNC machine tools.
2. Internal Offset Preload (Single Nut Preload)
Internal preload ball screws adopt special steel ball size difference or internal offset structure to realize preload inside a single nut. The structure is compact and easy to install.
Advantages: Small size, simple installation, uniform stress, low noise.
Disadvantages: Preload adjustment range is limited, not suitable for super heavy load.
Applications: Automation linear modules, 3C processing equipment, robotic linear actuators.
3. Spring Preload Structure
Spring-assisted preload uses elastic components to compensate nut clearance dynamically. It can automatically absorb clearance changes caused by wear and temperature deformation.
Advantages: Good wear compensation, long-term stable precision, strong environmental adaptability.
Disadvantages: Limited rigidity, not suitable for high-impact working conditions.
Applications: Medium-precision automatic production lines, continuous cycle handling equipment.
How to Choose the Right Preload Type
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Zero backlash & ultra-precision: Double nut preload (C2/C3 grade)
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Compact structure & low noise: Internal single nut preload (C5 grade)
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Long service life & wear tolerance: Spring dynamic preload (C7 grade)
Final Summary
Ball screw preload directly determines the precision stability of linear motion equipment. Reasonable preload matching can completely solve backlash, jitter and positioning drift problems. According to precision grade, installation space and load conditions, selecting the correct preload structure is the key to improving equipment yield and stability.