Common faults and solutions of slewing drives

What is Slewing Drive?

The slewing drive is full-cycle rotary deceleration transmission mechanism with integrated drive power. It uses a rotating bearing as a drive follower and mechanism attachment. By attaching the active element, drive source and cover to one of the inner and outer rings of the rotating bearing, the other ring serves as both a drive follower and a connecting base for the driven working part. This makes use of the characteristics of the rotary bearing itself as a full-cycle rotary connector, and the efficient configuration of the drive power source and main transmission components, making it a universal deceleration transmission mechanism integrating rotation, deceleration and driving functions, and also has the characteristics of simple structure and convenient manufacturing and maintenance. Shown here are two typical slewing drives.

Features of Slewing Drive:

Compact layout: The integrated power mechanism and support system eliminate the independent support structure in the traditional transmission chain, and the installation volume of the equipment is reduced by about 40%.

High-efficiency transmission: the power is directly transmitted through the inner and outer rings of the bearing, eliminating the intermediate transmission loss, and the transmission efficiency is generally more than 85%.

Heavy-duty load: Equipped with worm gear or planetary reduction mechanism, the output torque covers a wide range from 500 N·m to tens of thousands of N·m.

Precise motion control: Through bearing preload adjustment and meshing clearance optimization technology, the ±0.05° level of motion repeatability is achieved.

Modular architecture: The power module, support components, and protective devices are designed with standardized interfaces to support rapid replacement and maintenance.

Environmental adaptability: The integral sealing structure meets the IP65 protection standard and is resistant to high dust, moisture and corrosive working conditions.

Working Principle of Slewing Drives

The slewing drive uses the slewing bearing as the core of the operation, and completes the power transmission through four key stages:

Power Transmission Phase: The electric motor drives the worm shaft or gear train to transmit the initial rotational kinetic energy to a specific drive interface in the inner/outer ring of the bearing.

Torque conversion stage: through the multi-stage meshing transmission of worm gear pair or planetary gear set, the speed step reduction and torque geometric progression amplification are realized with the help of the reduction ratio.

Motion output stage: the bearing fixed side ring is rigidly anchored with the equipment base, and the drive side ring is docked with the operating load through the high-strength flange to form an effective rotating output.

Composite bearing stage: the precision-arranged rolling elements (steel balls/cylindrical rollers) realize continuous cyclic movement between the inner and outer ring raceways, and synchronously complete the three-dimensional mechanical bearing of axial load, radial load and overturning moment.

Common faults and solutions of slewing drives

The following are the common fault types, causes and corresponding solutions of rotary drives in practical applications, combined with their structural characteristics (such as worm drive, seal design, etc.):

1. Mechanical transmission failure

Unusual noise or vibration

Causes: Tooth flank wear, excessive backlash, bearing damage or ingress of foreign objects.

Solution: Check the wear of the tooth surface of the worm gear and replace the worn parts if necessary. Adjust the backlash to a specified range (e.g. WEA9 backlash≤0.35mm). Clean internal impurities, replace grease or add lubricating oil.

Stuck or unable to turn

Causes: Overload leading to worm deformation, foreign body seizure or lubrication failure.

Solution: Check if the load exceeds the rated value (e.g. WE25 axial static load 2360kN) to lighten the load. Disassemble and remove the foreign matter inside, and reapply the high-temperature grease (if suitable for high-temperature environments). Replace the deformed worm or worm gear (e.g. 42CrMo material needs to be quenched).

2. Sealing and protection issues

Oil leakage or oil leakage

Causes: Aging seals, cracks in the housing, or loose bolts.

Solution: Replace O-rings or oil seals (fluoroelastomer material is recommended for corrosion resistance).

Inspect the housing for cracks and weld to repair or replace if necessary. Tighten the bolt according to the specified torque

Water ingress or dust ingress

Cause: Inadequate degree of protection (e.g. below IP65) or failure of sealing.

Solution: Upgrade the degree of protection to IP67 (e.g. with a dust cover). Check that the vents are not blocked to ensure that the internal air pressure is balanced.

3. Lubrication system failure

Insufficient or ineffective lubrication

Causes: Dry grease, clogged oil holes, or incorrect sizing.

Resolution: Use a high-temperature grease (e.g., NLGI Grade 2) and replenish regularly (every 500 hours is recommended). Dredging the oil injection hole and cleaning the oil circuit. Choose the right grease according to the working conditions (e.g. lithium grease for low temperature environments).

Excessive lubrication

Cause: Excess grease leads to increased resistance or higher temperatures.

Solution: Clean up excess grease and maintain the right amount of lubrication. Check if the seal has been damaged due to excessive pressure.

4. Installation and foundation issues

Loose or broken bolts

Causes: Insufficient installation torque, excessive vibration, or uneven load.

Solution: Use a torque wrench to tighten at a standard torque. Add an anti-loosening rubber or spring washer and check the flatness of the mounting surface.

The overturning moment is overrun

Cause: The load exceeds the design value (e.g. WE17 overturning moment 350kN・m).

Solution: Recalculate the load and select a higher specification model (e.g. upgrade to WE25). Increase the auxiliary support structure to disperse the torque.

5. Electrical and drive faults

The motor is overloaded or burned

Causes: Unstable voltage, mismatched ratios, or frequent start-stops.

Solution: Check the stability of the power supply and install an overload protection device. Adjust the speed ratio to a reasonable range (e.g. 1:50~1:100 for WE series).

The control system is abnormal

Cause: Encoder failure, signal interference, or program error.

Solution: Calibrate the encoder, check the line shield. Reconfigure control parameters (e.g., limit switch position).

Precautionary measures

Regular maintenance: Check lubrication, sealing, and bolt tightness every 2000 hours.

Condition monitoring: Real-time monitoring of temperature, vibration, and load with sensors (e.g., the WE series supports IoT modules).

Selection and adaptation: Choose the material (such as 316L stainless steel for corrosive environments) and the protection level according to the actual needs.

Supplier of Slewing Drives

LTZC is a professional slewing drive manufacturer, providing high-quality slewing drives with accuracy covering four levels: Po, P6, P5 and P4. Executive standard: universal bearing GB/T307, slewing drive JB/2300, shipbuilding industry CB/T3669, machinery industry JB/T10471, wind turbine bearing B/T10705. In 2003, it passed the SO9001 quality system certification.