New Study Explores Excavator Agility Through Slewing Bearings

In the field of construction machinery, excavators are renowned for their exceptional flexibility and efficiency, capable of performing complex tasks such as grabbing, rotating, and unloading with precision. This powerful slewing capability is not accidental but stems from a core component located above the chassis—the slewing bearing.

Slewing bearings, also known as turntable bearings or slewing rings, serve as the critical hub connecting the upper and lower structures of excavators, enabling 360-degree omnidirectional operation. This article, written in an encyclopedic style, will thoroughly analyze the working principles, structural characteristics, application scenarios, maintenance points, fault diagnosis and troubleshooting, as well as related technological developments of slewing bearings. The goal is to reveal the secrets behind the flexible rotation of excavators and provide valuable insights for professionals in the construction machinery industry.

Slewing bearings are large-scale bearings capable of simultaneously withstanding axial loads, radial loads, and overturning moments. They integrate rotation, gear transmission, and installation connections into a single unit, simplifying design, reducing costs, and improving reliability.

In construction machinery like excavators, slewing bearings connect the upper structure (including the cab, engine, and hydraulic system) with the lower traveling mechanism (tracks or wheels), enabling the upper structure to rotate 360 degrees relative to the lower structure. This allows for full-range operational coverage.

The evolution of slewing bearings is closely tied to the development of construction machinery. Early machinery used simple sliding bearings or ball bearings for rotation, but their load capacity and precision were insufficient for large-scale equipment. With advancements in materials science and manufacturing technology, the production of large bearings became feasible.

In the early 20th century, slewing bearings capable of handling heavier loads emerged and were applied to cranes and other equipment. As construction machinery evolved, slewing bearings underwent continuous improvements in structure and performance, leading to various types tailored to different applications.

Slewing bearings can be categorized in multiple ways, including:

• By rolling element type: Ball-type (for lighter loads and higher speeds) and roller-type (for heavier loads and lower speeds). Roller-type bearings can be further divided into cylindrical, tapered, and spherical roller bearings.
• By raceway rows: Single-row (simple and cost-effective), double-row (higher load capacity and precision), and triple-row (maximum load capacity and stiffness).
• By gear type: External gear (easy installation), internal gear (compact for space-constrained applications), and gearless (for high-precision requirements).
• By structure: Integral (compact and easy to install) and split (facilitates maintenance and replacement).

Slewing bearings are widely used in various industries, including:

• Excavators: Support and rotate the upper structure for digging, loading, and unloading.
• Cranes: Enable the upper structure to lift and transport heavy loads.
• Wind turbines: Rotate the nacelle to harness wind energy.
• Medical equipment: Used in CT scanners and MRI machines for rotational components.

A typical slewing bearing consists of:

• Inner and outer rings: Made of high-strength alloy steel, heat-treated, and precision-machined for durability.
• Rolling elements: Balls or rollers that reduce friction and enable smooth rotation.
• Retainers: Separate rolling elements to prevent collisions.
• Seals: Protect against contaminants and retain lubrication.
• Gears (if applicable): Transmit rotational force.

Slewing bearings operate by converting sliding friction into rolling friction, minimizing resistance. Lubrication is critical to reduce wear and dissipate heat, ensuring longevity.

Proper lubrication intervals (every 100–200 operating hours) with suitable grease are essential to prevent wear and corrosion.

Issues like stiffness, noise, vibration, or leakage often stem from inadequate lubrication, contamination, or overloading.

Routine inspections of seals, bolts, and gear conditions can preempt failures. Avoid overloading and ensure proper installation.

Advancements in slewing bearings focus on higher load capacities, precision, longevity, and smart monitoring systems. Lightweight materials and modular designs are also gaining traction.

Slewing bearings are indispensable in construction machinery, enabling the flexibility and efficiency required for modern operations. Understanding their design, maintenance, and evolving technologies ensures optimal performance and durability in demanding environments.