Frequently Asked Questions

How should crossed roller bearings be maintained and cared for in daily use?

Crossed roller bearings are widely used in industrial applications—such as robot joints, machine tool spindles, and aerospace—thanks to their high precision, high load capacity, and compact design. However, to ensure optimal performance and extend their service life, routine maintenance and care are essential. This article provides a detailed overview of daily maintenance and upkeep procedures for crossed roller bearings, helping users perform equipment maintenance in a scientific and systematic manner to guarantee reliable bearing operation.

How to Perform Daily Maintenance and Care for Crossed Roller Bearings
I. Lubrication Management for Crossed-Roller Bearings
(1) Select an appropriate lubricant

1. Lubricant Type

Lubricating oil: Suitable for low-speed, high-temperature applications or situations requiring heat dissipation. Lubricating oil has excellent fluidity and can effectively carry away heat.

Grease: Suitable for high-speed, low-temperature applications, or situations requiring long-term lubrication. Grease offers excellent sealing performance, effectively preventing dust and contaminants from entering the bearing.

2. Lubricant Selection Criteria

Operating temperature: Select an appropriate lubricant based on the operating temperature of the crossed roller bearing. In high-temperature environments, choose a high-temperature‑resistant lubricant.

Operating speed: Select an appropriate lubricant based on the bearing’s rotational speed. For high-speed bearings, use a low-viscosity lubricant.

Load conditions: Select an appropriate lubricant based on the bearing’s load. For high-load bearings, a high-viscosity lubricant should be chosen.

(II) Addition and Replacement of Lubricants

1. Add lubricant

Cleaning: Before applying lubricant, clean the crossed roller bearing and its surrounding area to ensure there is no dust or foreign matter.

Appropriate Amount: Add an appropriate amount of lubricant based on the bearing’s specifications and operating conditions. Both excessive and insufficient lubrication can adversely affect bearing performance.

2. Replace the lubricant

Regular replacement: Replace the lubricant at regular intervals, based on its usage and operating conditions. It is generally recommended to change it every 3 to 6 months.

Check the lubricant condition: When replacing the lubricant, inspect its color, consistency, and quantity. If the lubricant has discolored, deteriorated, or is insufficient in amount, it should be replaced immediately.

II. Cleaning and Maintenance of Crossed Roller Bearings
(1) Regular Cleaning

1. Cleaning frequency

Daily Cleaning: After each operation, perform a quick cleaning to remove surface dust and debris.

Deep Cleaning: It is recommended to perform a thorough cleaning once every quarter to remove dirt and contaminants from inside the crossed roller bearing.

2. Cleaning Method

Soft cloth wiping: Use a soft cloth or non-woven fabric to wipe the bearing surface, avoiding the use of hard objects to prevent damage to the bearing surface.

Cleaning with a cleaning solution: For thorough cleaning, use a dedicated cleaning solution. Ensure that the cleaning solution is non-corrosive to the materials of the crossed roller bearing.

(2) Pollution Prevention

1. Sealing Measures

Sealing device: Ensure that the bearing’s sealing device is intact and undamaged to prevent dust and contaminants from entering the bearing interior.

Regular Inspection: Regularly check the sealing performance of the sealing device, and replace it promptly if any damage is detected.

2. Working Environment

Clean Environment: Keep the equipment’s operating environment clean to prevent the accumulation of dust and contaminants.

Protective measures: During equipment operation, implement necessary safeguards, such as installing protective guards, to prevent external contamination.

Crossed roller bearing

III. Load and Speed Control of Crossed Roller Bearings
(1) Reasonably control the load

1. Load range

Design Load: Ensure that the cross-roller bearing operates within its specified load range. Exceeding the design load will accelerate bearing wear and reduce its service life.

Dynamic Load: For dynamic loads, ensure that load variations remain within the bearing’s allowable limits.

2. Load Monitoring

Monitoring equipment: Use load-monitoring devices to continuously track the load conditions of cross-roller bearings in real time.

Adjust the load: Based on monitoring results, promptly adjust the load to ensure the crossed roller bearing operates within its safe operating range.

(2) Reasonably control the rotational speed.

1. Speed range

Design speed: Ensure that the bearing’s rotational speed remains within its design limits. Exceeding the design speed will accelerate bearing wear and reduce its service life.

Dynamic rotational speed: For dynamic rotational speeds, ensure that the speed variations remain within the bearing’s allowable limits.

2. Rotational Speed Monitoring

Monitoring equipment: A rotational speed monitoring device is used to continuously track the rotational speed of the crossed roller bearing.

Adjust the rotational speed: Based on monitoring results, promptly adjust the speed to ensure the crossed roller bearing operates within its safe operating range.

IV. Monitoring of the Operating Condition of Crossed-Roller Bearings
(1) Vibration Monitoring

1. Vibration sensor

Installation Location: Install a vibration sensor near the crossed roller bearing to monitor its vibration in real time.

Monitoring frequency: It is recommended to conduct vibration monitoring once per hour to promptly detect any abnormal vibrations.

2. Vibration Analysis

Data Analysis: Utilize vibration data analysis software to process vibration data and promptly identify potential issues.

Early warning mechanism: A vibration-based early warning system is implemented, which promptly triggers an alarm when vibration levels exceed the set threshold.

(2) Temperature Monitoring

1. Temperature sensor

Installation Location: Install the temperature sensor near the crossed roller bearing to monitor the bearing’s temperature in real time.

Monitoring frequency: It is recommended to conduct temperature monitoring once per hour to promptly detect any abnormal temperatures.

2. Temperature Analysis

Data Analysis: Use temperature data analysis software to process temperature data and promptly identify potential issues.

Early warning mechanism: A temperature‑based alert system is in place to issue timely warnings when the temperature exceeds the set threshold.

(3) Noise Monitoring

1. Noise sensor

Installation Location: Install the noise sensor in the equipment’s operating environment to monitor noise levels in real time.

Monitoring frequency: It is recommended to conduct noise monitoring once per hour to promptly detect any abnormal noise levels.

2. Noise Analysis

Data Analysis: Utilize noise‑analysis software to process noise data and promptly identify potential issues.

Early warning mechanism: An noise‑level early warning system is in place, which promptly triggers an alarm when the noise exceeds the preset threshold.

V. Maintenance Records and Periodic Inspections
(1) Maintenance Records

1. Record Content

Lubrication Log: Record the time of each lubrication, the type of lubricant, and the amount used.

Cleaning Records: Document the time and method of each cleaning session.

Inspection Records: Record the time of each inspection, the inspection items, and the inspection results.

2. Records Management

Electronic Records: It is recommended to use an electronic records system for convenient management and retrieval.

Regular Reviews: Conduct periodic reviews of maintenance records, analyze equipment operating conditions, and promptly identify potential issues.

(2) Regular Inspections

1. Inspection Frequency

Monthly Inspection: Conduct one inspection per month, covering lubrication, cleaning, sealing devices, and other related tasks.

Quarterly Inspection: Conducted once per quarter, this inspection includes monitoring operational parameters such as vibration, temperature, and noise levels.

2. Inspection Content

Visual inspection: Examine the bearing’s exterior for signs of wear, deformation, or corrosion.

Performance Testing: Evaluates the bearing’s rotational smoothness, vibration levels, and noise output.

Lubrication Inspection: Check the condition of the lubricant and determine whether it needs to be replenished or replaced.

Seal Inspection: Verify the sealing performance of the sealing device and determine whether replacement is necessary.

Proper daily maintenance and care of crossed roller bearings are essential for ensuring reliable equipment operation and extending service life. By implementing sound lubrication management, regular cleaning and upkeep, careful control of load and rotational speed, continuous monitoring of operating conditions, and systematic record-keeping and periodic inspections, the incidence of failures can be reduced, thereby enhancing equipment reliability and operational efficiency. Users are encouraged to establish a comprehensive maintenance regime, conduct routine inspections, and adopt preventive replacement strategies to guarantee long-term, stable performance. It is hoped that this article will provide valuable guidance, helping users carry out equipment maintenance in a scientific and well‑structured manner.

How do cross-roller bearings achieve high repeat positioning accuracy?

In modern industry, machinery and automated equipment demand high repeat positioning accuracy from bearings. Crossed roller bearings, with their distinctive structural design and superior precision performance, are an ideal choice for many high‑precision applications. By means of optimized design, proper installation, and regular maintenance, crossed roller bearings can meet stringent requirements for repeat positioning accuracy. This paper will examine in detail how crossed roller bearings achieve such high repeat positioning accuracy through their unique design features.

How do crossed roller bearings achieve high repeat positioning accuracy?
1. Structural Design
Crossed roller bearings employ a unique crossed‑arrangement design, with rollers intersecting within the raceways, enabling the bearing to withstand high loads in both the radial and axial directions. This configuration not only enhances the bearing’s load-carrying capacity but also significantly improves its repeat positioning accuracy.

Crossed roller bearing

2. High-Precision Manufacturing
The manufacturing process of crossed roller bearings employs high-precision machining techniques to ensure dimensional accuracy and surface finish of both the rollers and raceways. This precision manufacturing minimizes internal friction and wear, enhancing operational smoothness and repeatable positioning accuracy.

3. Preload Design
Through proper preload design, crossed roller bearings can eliminate internal clearance, enhancing bearing stiffness and repeatable positioning accuracy. The magnitude of the preload must be calculated and adjusted according to the specific application to ensure high precision during operation.

How do crossed roller bearings achieve high repeat positioning accuracy? Thanks to their structural design and high‑precision performance, crossed roller bearings can meet stringent requirements for repeat positioning accuracy. Through optimized design, proper installation, and regular maintenance, these bearings can deliver precise operation in a wide range of machinery and automation systems. In practical applications, users should tailor maintenance schedules and operating procedures to the specific conditions of their equipment, promptly identify and address potential issues, and ensure both reliable equipment performance and the long‑term stability of the bearings.

Life Assurance of Crossed Roller Bearings under High-Speed, Heavy-Load Operating Conditions

Crossed roller bearings, owing to their compact design and high precision, are widely used in mechanical transmission systems. However, under high-speed, heavy-load conditions, their service life faces severe challenges. High rotational speeds increase centrifugal forces, while heavy loads exacerbate contact stresses between the rollers and raceways—both of which can lead to premature bearing failure. Consequently, ensuring the longevity of crossed roller bearings in such demanding operating conditions is critical for enhancing equipment reliability and reducing maintenance costs. This paper examines, from multiple perspectives, strategies for extending the service life of crossed roller bearings.

Life Assurance of Crossed-Roller Bearings under High-Speed, Heavy-Load Operating Conditions
I. Rational Selection and Design Optimization
1. Select the appropriate bearing model

High-speed, heavy-load operating conditions place stringent demands on a bearing’s load-carrying capacity and dynamic performance. Selecting the appropriate bearing model is essential for ensuring long service life. Based on the equipment’s rotational speed and load characteristics, choose a crossed-roller bearing whose dynamic load rating and speed capability both meet the requirements. For instance, under high-speed, heavy-load conditions, priority should be given to double-row crossed-roller bearings that offer high precision, high stiffness, and excellent dynamic balance.

2. Optimize bearing design

Optimizing the internal structural design of bearings can enhance their performance under high-speed, heavy-load operating conditions. Selecting bearings with optimized raceway designs helps reduce contact stresses between the rollers and raceways. Meanwhile, employing a lightweight cage design minimizes the impact of centrifugal forces on the bearing. Fabricating the cage from high-strength steel or ceramic materials further improves its strength and stability.

3. Consider the preload

Appropriate preload can enhance bearing stiffness and stability, but excessive preload increases wear. Select the preload level based on the equipment’s actual operating conditions. Under high-speed, heavy-load conditions, a light preload or no‑preload design is recommended to minimize friction and wear between the rollers and raceways.

Crossed roller bearing

II. Optimization of the Lubrication and Cooling Systems
1. Choose the appropriate lubricant

The performance of the lubricant directly affects bearing life. Under high-speed, heavy-load operating conditions, the lubricant must exhibit excellent high-temperature stability and wear resistance.

Choose high-performance synthetic greases or lubricating oils, which offer higher dropping points and superior anti-wear properties. Polyalphaolefin (PAO) synthetic greases can maintain excellent lubrication at elevated temperatures, thereby extending bearing life.

2. Optimize the lubrication method

An appropriate lubrication method ensures uniform distribution of the lubricant within the bearing, thereby reducing wear. Select the suitable lubrication approach based on the equipment’s operating conditions. For high-speed, heavy-load applications, oil‑mist or oil‑bath lubrication can deliver superior performance. Oil‑mist lubrication evenly atomizes the lubricant and delivers it into the bearing interior, minimizing areas with inadequate lubrication.

3. Strengthen cooling measures

Under high-speed, heavy-load operating conditions, bearing temperatures rise; excessively high temperatures accelerate lubricant oxidation and bearing material fatigue. Cooling measures—such as air cooling, water cooling, or oil‑cooling systems—should be employed to reduce bearing operating temperatures. Installing cooling fans or cooling jackets can lower bearing temperatures and extend their service life.

III. Strengthening Operational Monitoring and Maintenance
1. Real-time monitoring of bearing condition

By continuously monitoring the operating condition of bearings, potential faults can be detected promptly, preventing equipment downtime. Installing monitoring devices such as temperature sensors, vibration sensors, and oil‑condition analyzers enables real-time tracking of bearing temperature, vibration, and lubricant quality. Vibration sensors can identify abnormal vibrations, allowing early detection of issues like wear or looseness.

2. Regular Maintenance and Inspections

Regular maintenance is a crucial means of ensuring bearing life. Routine inspections enable the timely identification and resolution of potential issues. Develop a detailed maintenance schedule that includes periodic checks of lubrication, wear conditions, and operating temperatures. For example, conduct quarterly inspections to replenish or replace grease and adjust bearing clearances, among other tasks.

3. Data Analysis and Fault Prediction

Through data analysis, it is possible to predict bearing failure trends and take proactive measures. A equipment‑operating database should be established to record all monitoring and maintenance data. Using data‑analysis software, trend analysis can be performed to estimate the remaining useful life of bearings. Moreover, vibration‑data analysis enables early detection of bearing wear patterns, allowing for timely scheduling of maintenance.

Under high-speed, heavy-load operating conditions, ensuring the service life of crossed roller bearings requires a comprehensive approach that takes into account design selection, lubrication, cooling, and monitoring. By making appropriate bearing selections, optimizing the lubrication and cooling systems, and strengthening operational monitoring and maintenance, it is possible to extend bearing life and enhance equipment efficiency and reliability. It is hoped that this article will provide users with practical guidance, helping them better safeguard the service life of crossed roller bearings in real-world applications.

Maintenance of Crossed Roller Bearings in High-Temperature Environments

In industrial production, many pieces of equipment operate under high-temperature conditions, placing stringent demands on the performance and service life of crossed roller bearings. Elevated temperatures accelerate the aging and wear of bearing materials, thereby compromising their performance and reliability. Consequently, understanding maintenance strategies for crossed roller bearings in high-temperature environments is essential to ensuring stable equipment operation and extending bearing life. This article provides a detailed overview of cross‑roller bearing maintenance under high‑temperature conditions, covering lubrication management, cooling systems, routine inspections, and troubleshooting procedures.

Maintenance of Crossed Roller Bearings in High-Temperature Environments
I. Lubrication Management
1. Choose the appropriate lubricant

High-Temperature Lubricants: In high-temperature environments, it is essential to select lubricants that are resistant to heat. These lubricants maintain excellent lubrication performance at elevated temperatures, thereby reducing friction and wear.

Lubricant stability: Select lubricants with high thermal stability and excellent oxidation resistance. These lubricants can maintain their performance at elevated temperatures, thereby minimizing degradation caused by heat.

2. Frequency of lubricant replacement

Regular replacement: In high-temperature environments, the frequency of lubricant changes should be appropriately increased. High temperatures accelerate lubricant degradation, and regular replacement ensures that the lubricant remains in optimal condition.

Check the lubricant condition: Regularly inspect the lubricant, observing any changes in color and viscosity. If the lubricant turns black or its viscosity decreases, replace it promptly.

3. Amount of lubricant added

Add in appropriate amounts: In high-temperature environments, the amount of lubricant added should be moderate. Too much lubricant may lead to heat buildup at elevated temperatures, while too little will fail to adequately lubricate the bearing.

Uniform distribution: Ensure that the lubricant is evenly distributed throughout the cross-roller bearing. When using grease, apply it uniformly to both the rolling elements and the raceways.

II. Cooling System
1. Design of the Cooling System

Cooling device: In high-temperature environments, a cooling device should be installed. For example, use a cooling fan or heat sink to help reduce the temperature of cross roller bearings.

Coolant circulation: For certain high‑load equipment, a coolant circulation system can be employed. The coolant absorbs the heat generated by cross‑roller bearings, helping to maintain bearing temperatures within an acceptable range.

2. Maintenance of the Cooling System

Regular Inspections: Periodically check the cooling system’s operating condition. Verify that the cooling fan is functioning properly and that the coolant level is adequate.

Clean the cooling system: Regularly clean the cooling system to ensure optimal heat dissipation. For example, remove dust and debris from the散热片 (heat sinks) to maintain their cooling efficiency.

3. Optimization of the Cooling System

Optimize the coolant: Select an appropriate coolant based on the equipment’s operating temperature and ambient conditions. A properly chosen coolant can enhance the efficiency of the cooling system.

Adjust cooling parameters: Based on the equipment’s operating condition, fine-tune the cooling system’s settings. For example, adjust the coolant flow rate and temperature to ensure optimal cooling performance.

Crossed roller bearing

III. Routine Inspections
1. Temperature Monitoring

Install a temperature sensor: Position the temperature sensor near the bearing. Monitor the bearing’s temperature in real time to ensure it remains within safe limits.

Record temperature data: Regularly log temperature readings and analyze trends. If an abnormal temperature increase is detected, take prompt corrective action.

2. Vibration Monitoring

Install vibration sensors: Mount vibration sensors near the crossed roller bearings. Monitor bearing vibrations in real time to promptly detect potential faults.

Analyze vibration data: Regularly analyze vibration data to detect any abnormal vibrations. If abnormal vibrations are detected, promptly inspect the operating condition of the bearings.

3. Visual Inspection

Inspect the bearing surface: Regularly check the cross-roller bearing for signs of wear, cracks, or corrosion. Such defects can degrade bearing performance and even lead to failure.

Check the lubricant condition: Inspect for changes in color and viscosity. If the lubricant has turned black or its viscosity has decreased, replace it promptly.

IV. Troubleshooting
1. Abnormally high temperature

Check the cooling system: If the cross-roller bearing temperature is abnormally high, first inspect the cooling system’s operating condition. Ensure that the coolant level is adequate and that the heat‑dissipation components are functioning properly.

Check the lubricant condition: Inspect for changes in color and viscosity. If the lubricant has turned black or its viscosity has decreased, replace it promptly.

2. Abnormal Vibration

Check bearing installation: If abnormal vibration is detected in the crossed roller bearing, verify that the bearing is properly positioned. Ensure the bearing is accurately installed, with no eccentricity or misalignment.

Inspect the rolling elements and raceways: Check for wear or cracks on both the rolling elements and the raceways. If any wear or cracks are detected, replace the crossed roller bearing promptly.

3. Lubricant Leakage

Inspect the sealing assembly: If lubricant leakage is detected, check whether the seals are damaged. Ensure that the seals are intact and free of leaks.

Replace the sealing device: If the sealing device is found to be damaged, it should be replaced promptly. After replacement, check for any lubricant leaks.

Maintaining crossed roller bearings in high-temperature environments is essential for ensuring stable equipment operation and extending bearing life. By optimizing lubrication management, cooling systems, routine inspections, and troubleshooting procedures, the adverse effects of elevated temperatures on these bearings can be minimized. It is hoped that this article will help technical personnel better maintain and manage crossed roller bearings, thereby guaranteeing reliable equipment performance under high‑temperature conditions.

Rust- and Corrosion-Resistant Treatment and Storage Methods for Crossed Roller Bearings

As high-precision, high-value mechanical components, cross roller bearings require meticulous rust‑proofing and corrosion‑prevention treatments, along with scientifically sound storage practices, to safeguard product quality, extend shelf life, and ensure reliable performance. After manufacturing and prior to deployment, these bearings may remain in storage for months or even years, exposed to environmental hazards such as humidity, salt spray, temperature fluctuations, and contamination. Inadequate protection can lead to rust, corrosion, and loss of precision, resulting in substantial economic losses. Given their complex structure, stringent precision requirements, and heightened sensitivity to cleanliness and corrosive environments, cross roller bearings demand far more rigorous rust‑proofing and corrosion‑prevention measures than standard bearings. Consequently, establishing a systematic protective‑technology framework and standardized storage‑management protocols is an essential component of quality assurance for cross roller bearings. This paper elaborates on the key aspects of rust‑proofing and corrosion‑prevention for cross roller bearings, examining five critical dimensions: cleaning and degreasing, rust‑inhibiting treatments, packaging and protective measures, storage environment, and inventory management.

Rust- and Corrosion-Resistant Treatment and Storage Methods for Crossed Roller Bearings
I. Cleaning, Degreasing, and Drying Processes
1. Post-manufacturing cleaning

Cleaning agent selection: Use a neutral or mildly alkaline water-based cleaner, or a petroleum‑based solvent cleaner, to remove machining residues such as oil stains, metal chips, and fingerprints. Avoid using strong acids or strong alkalis that could corrode the surface of crossed roller bearings; the cleaning agent must be compatible with the bearing material.

Cleaning process control: Ultrasonic cleaning or spray rinsing, with temperature maintained between 40 and 60°C for sufficient duration to ensure thorough cleanliness. Post‑cleaning, multi‑stage rinsing is performed to remove residual cleaning agents. Bearings are processed using dedicated cleaning equipment to prevent cross‑contamination.

2. Drying Process

Drying method selection: Use hot-air circulation drying, vacuum drying, or desiccant‑based moisture absorption to ensure complete drying of both the surface and internal channels. Maintain the drying temperature below 80°C to prevent tempering or changes in material properties. Immediately apply a rust‑preventive treatment after drying to avoid reabsorption of moisture.

Drying verification: Use a dew‑point meter or humidity indicator cards to assess the drying performance. For critical cross‑roller bearings, employ the gravimetric method, comparing the mass change before and after drying to confirm residual moisture levels.

II. Rust-Prevention Treatment Technologies
1. Application of rust-preventive oil

Rust‑preventive oil selection: Depending on the storage duration and environmental conditions, choose displacement‑type rust‑preventive oil, solvent‑diluted rust‑preventive oil, or grease‑type rust‑preventive oil. For short‑term storage (within one year), use a thin‑film rust‑preventive oil; for long‑term storage (three years or more), use a thick‑layer rust‑preventive grease or vapor‑phase rust inhibitor.

Coating process: dip coating, brush coating, or spray coating—ensure that all surfaces of the cross roller bearing are uniformly covered, with no omissions in concealed areas such as raceways, rollers, and cage pockets. Control the coating thickness: excessive coating may cause dripping and buildup, while insufficient coating provides inadequate protection. After coating, allow the excess to drain or spin off to form a uniform oil film.

2. Gas-phase corrosion protection applications

Vapor-phase corrosion‑inhibiting materials—such as vapor‑phase corrosion‑inhibiting paper, film, or powder—release inhibitive vapors that form a protective atmosphere within a sealed environment. When used in conjunction with rust‑preventive oils, they enhance long‑term protection. These materials must be compatible with the bearing material to prevent chemical reactions.

Application method: Wrap the bearing with vapor‑phase corrosion‑inhibiting paper, or place it in a vapor‑phase corrosion‑inhibiting bag and seal it. Place a vapor‑phase corrosion inhibitor inside the bag to ensure that the concentration of evaporated gas meets the required protection level. Regularly inspect the effectiveness of the vapor‑phase corrosion‑inhibiting material and replace it promptly when it has lost its efficacy.

3. Peelable plastic coating

Special protection requirements: For long-term storage or marine transportation, apply a removable plastic coating—such as acrylic resin or polyvinyl alcohol—to the surface of crossed roller bearings. The coating thickness should be between 0.5 and 2 mm, creating a physical barrier that isolates the bearing from corrosive media.

Removal method: Prior to use, manually or mechanically strip the coating until it is completely removed with no residue. Verify the cleanliness of the surface after coating removal; perform a secondary cleaning if necessary.

Crossed roller bearing

III. Packaging and Protection System
1. Inner Packaging Protection

Moisture‑proof packaging materials: aluminum‑plastic composite film, aluminized film, or co‑extruded nylon film, with a water vapor transmission rate of less than 1 gram per square meter per day. Use heat sealing or vacuum packaging, and place desiccants and humidity indicator cards inside the bag. Before packaging, allow the bearing temperature to equilibrate with the ambient temperature to prevent condensation.

Buffering and Fixing: Foam plastics, corrugated cardboard, or injection-molded pallets are used to secure the bearings, minimizing vibration and impact during transport. Cushioning material is placed between the cage and the rollers to prevent relative movement and wear. The bearings are packaged in a suspended‑type package or with dedicated tooling.

2. Reinforcement of outer packaging

Packaging strength: Five-layer corrugated cardboard boxes or wooden crates, with compressive and drop‑test resistance meeting transportation requirements. The interior is lined with cushioning material to eliminate voids and prevent movement. Packaging markings are clear, including handling symbols such as “This Side Up,” “Keep Dry,” and “Handle With Care.”

Unitized Packaging: Large‑quantity bearings are packaged on pallets and secured with stretch film or strapping. For container transport, moisture‑proof liners and desiccants are used to control the internal microenvironment.

IV. Storage Environment Control
1. Warehouse Requirements

Temperature and humidity control: The storage facility shall maintain a temperature between 5°C and 25°C, with relative humidity kept below 60%. A temperature and humidity monitoring and recording system shall be installed, with alarms triggered upon exceeding set limits. During the rainy season or periods of high humidity, dehumidifiers or air-conditioning units shall be activated to prevent condensation and mold growth.

Cleaning and Contamination Prevention: The warehouse is located away from corrosive environments such as chemical plants, acidic or alkaline areas, and salt‑spray zones, and is free of dust and harmful gases. Regular cleaning is performed to prevent dust accumulation. Crossed roller bearings are stored on racks or pallets, with a clearance of at least 200 mm from the floor and at least 500 mm from the walls.

2. Classified Storage Management

Batch and Specification Classification: Store items by model, specification, accuracy class, and batch, with clear labeling to facilitate traceability. Apply the first‑in, first‑out principle to prevent over‑storage. Nonconforming and pending‑processing items shall be stored separately to avoid misuse.

Status Label Management: Clearly mark statuses such as “Packaging Intact,” “Opened,” “Pending Inspection,” and “Nonconforming.” After opening, cross-roller bearings that have not been used should either be re‑cleaned and re‑packaged with anti‑rust protection or stored temporarily in a sealed cabinet.

V. Inventory Management and Overdue Item Handling
1. Shelf-life management

Rust‑Prevention Monitoring: Based on data from rust‑preventive material suppliers and empirical testing, the shelf life of various rust‑prevention packaging types is determined. Typically, rust‑preventive oils provide protection for one to three years, vapor‑phase rust‑inhibiting packaging for three to five years, and peelable coatings for five to ten years. An inventory ledger is maintained to issue early warnings for bearings approaching their expiration dates.

Periodic sampling inspection system: Overdue bearings are sampled, disassembled, and inspected to assess their corrosion condition and dimensional accuracy retention. The sampling rate is determined based on the storage environment and historical data, typically ranging from 5% to 10% per batch.

2. Overdue Processing and Re‑Protection

Assessment and Grading: Crossed roller bearings that pass random inspection are re‑cleaned, re‑rust‑proofed, and repackaged to extend their storage life. Bearings with minor rust are repaired by fine polishing or chemical derusting, then re‑packaged for rust protection. Bearings with severe rust or loss of precision are scrapped to prevent them from entering service.

Re‑protection process: re‑clean and degrease, replace with a new type of anti‑rust material, and update the packaging markings. Record the date and number of re‑protection cycles; bearings that have undergone more than two re‑protections shall be used preferentially or downgraded for use.

VI. Storage in Special Environments
1. Maritime Transportation and Coastal Storage

Strengthen protective measures: Employ dual-layer protection using vapor‑phase corrosion‑inhibiting bags combined with desiccants, or apply a thick layer of anti‑rust grease. Use moisture‑proof wooden or metal crates for outer packaging, and ensure all seams are tightly sealed. During transit, monitor the temperature and humidity inside the container and record any anomalies.

Rapid handling upon arrival: Upon arrival at the port, promptly transfer the goods to a dry storage facility and inspect the integrity of the packaging. If any damage is detected or if the humidity indicator card has changed color, immediately open the container for inspection and take appropriate action.

2. Long-term strategic reserves

Ultra‑long‑term storage solution: Employ nitrogen‑flushed sealed packaging or vacuum packaging, supplemented with desiccants and oxygen scavengers. Store in an underground warehouse or a temperature‑ and humidity‑controlled facility at 10–15°C and 40–50% relative humidity. Conduct random inspections and assessments every two years, and replace packaging materials as necessary.

The rust‑proofing and corrosion‑prevention treatment, along with storage management, for crossed roller bearings requires a systems‑based approach that integrates materials science, packaging engineering, and environmental control. Cleaning and degreasing, rust‑preventive treatments, protective packaging, environmental monitoring, and inventory management must be coordinated as an interconnected whole. The key lies in recognizing the sensitivity of crossed roller bearings to cleanliness and corrosion: remove contaminants through thorough cleaning, select appropriate rust‑preventive materials to establish a protective barrier, ensure tight packaging to isolate the bearing from environmental exposure, and maintain controlled warehouse conditions to slow aging—thereby preserving the bearing’s precision and performance throughout storage. It is recommended that users develop standardized quality‑management procedures for storing crossed roller bearings, equip facilities with cleaning and rust‑prevention equipment as well as environmental monitoring systems, train dedicated bearing‑storage personnel, and establish technical‑support channels with bearing manufacturers and rust‑preventive material suppliers. By integrating the storage phase into the bearing’s full lifecycle quality‑management system, this shift moves from passive protection to proactive management.

Causes of rotational stiffness in crossed roller bearings

Crossed roller bearings are renowned for their high rigidity and precision, and their ideal operating condition is characterized by smooth, steady motion with uniform resistance. When rotational drag occurs, it manifests as noticeable uneven resistance, periodic sticking, or overall stiffness during manual turning or low-speed operation; in severe cases, substantial external force may be required to sustain rotation. Such rotational drag not only degrades the equipment’s positioning accuracy and dynamic response but also serves as a clear indicator of internal damage or assembly defects. If left unaddressed, the drag will rapidly escalate into seizing, accelerated wear, or fatigue failure, resulting in equipment downtime and financial losses. This paper systematically examines the causes of rotational drag in crossed roller bearings from five perspectives: preload conditions, lubrication status, foreign‑object ingress, raceway damage, and installation accuracy.

Causes of rotational stiffness in crossed roller bearings
1. Excessive preload
Crossed roller bearings rely on preload to eliminate clearance and enhance stiffness; however, when the preload exceeds an appropriate range, contact stresses between the rollers and raceways increase sharply, leading to excessive elastic deformation. The rolling space of the rollers within the raceways becomes compressed, causing additional axial contact between the end faces and the flanges and increasing the proportion of sliding friction. Excessive preload also significantly raises internal frictional power losses, intensifying operating temperature rise; thermal expansion further reduces clearances, creating a vicious cycle in which the bearing becomes progressively tighter as it rotates. In positioning‑type preload arrangements, an excessively thin spacer ring; in constant‑force preload systems, an overly stiff spring or excessively high hydraulic pressure—each can be a common cause of excessive preload.

2. Lubrication Failure
Lubricant degradation, contamination, or improper selection can prevent the formation of a lubricating film between the rollers and raceways. When grease is left unchanged for extended periods, the base oil oxidizes and evaporates, while the thickener hardens and forms clumps, losing its fluidity and adhesion. Dust, metal debris, or moisture that infiltrates the grease can lead to abrasive wear or emulsification‑induced failure. Under high‑speed, heavy‑load conditions, excessive shear forces cause rapid separation of the base oil, resulting in inadequate lubrication in the central region of the raceway. Once lubrication fails, direct metal‑to‑metal contact increases, frictional resistance rises sharply, and rotational drag is accompanied by abnormal noise and elevated temperatures.

Crossed roller bearing

3. Foreign Object Intrusion and Contamination
Seal failure or an unclean installation environment allows foreign particles—such as dust, metal chips, and fibers—to enter the bearing. Hard particles become lodged between the raceway and the rolling elements, creating localized high points that subject the rollers to additional compression and resistance as they pass. Flexible fibers may wrap around the rollers or cage, disrupting their normal motion path. Foreign contamination can also clog grease passages, leading to uneven lubrication and dry friction in certain areas. In dusty workshops, outdoor environments, or on equipment with aged seals, rotational binding caused by foreign‑particle ingress is particularly common.

4. Damage to Raceway and Roller Surfaces
Fatigue pitting, spalling, scratches, or indentations on the raceway surface render the originally smooth rolling contact uneven. As the rollers pass over damaged areas, the contact conditions change abruptly, generating impact and localized deformation, which in turn causes a periodic increase in running resistance. Wear on the roller end faces, loss of cylindricity, or cage deformation likewise compromise the smoothness of motion. Surface damage may result from prolonged overload, inadequate lubrication, foreign‑object intrusion, or installation impacts; once initiated, such damage exhibits self‑accelerating tendencies, with increasing stickiness as operating time accumulates.

5. Poor installation accuracy
During bearing installation, deviations in coaxiality, misalignment, or deformation of the raceways can lead to uneven contact between the rollers and the raceway surfaces. In localized areas, excessively small clearances—or even negative clearance—can cause the rollers to become jammed, while overly large clearances in adjacent regions may result in roller wobbling and deflection. Such non‑uniform contact causes the bearing to exhibit varying friction characteristics at different angular positions, producing periodic fluctuations in rotational resistance. Additionally, burrs, protrusions, or inadequate cleaning on the mating surfaces can create local high spots after assembly, likewise contributing to sluggish operation.

Solutions for Rotational Stiffness in Crossed-Roller Bearings

Solutions for Rotational Stiffness in Crossed Roller Bearings
1. Measures to address excessive preload
Loosen the lock nut or gland, remove the spacer ring or shim, and measure its thickness. Based on the bearing’s specifications and the manufacturer’s recommended preload range, recalculate the required preload and select a spacer of appropriate thickness. For constant‑pressure preloading arrangements, replace the spring with one of suitable stiffness or reset the hydraulic pressure. After re‑adjustment, use a torque wrench to tighten the fasteners in the prescribed sequence and to the specified torque; then measure the starting friction torque and axial clearance to confirm they remain within allowable limits. Following a low‑speed break‑in period, perform a second measurement to verify that the preload is appropriate.

2. Measures to Address Lubrication Failure
Clean the interior of the bearing, using a specialized cleaning agent to remove aged grease and contaminants. Inspect the raceways and roller surfaces: lightly damaged areas should be ground and repaired, while severely damaged components require bearing replacement. Select a new grease that matches the operating conditions, taking into account temperature, speed, load, and environmental factors; prioritize synthetic greases containing extreme-pressure additives and antioxidants. Grease the bearing to the specified fill quantity, ensuring even distribution. Maintain lubrication management records, determine replacement intervals based on operating conditions, and conduct periodic sampling to assess the grease’s condition.

Crossed roller bearing

3. Measures to Address Foreign Object Intrusion and Contamination
Disassemble the bearing and remove any foreign matter and contaminated grease from its interior. Inspect the seals for integrity, replacing any that are aged, deformed, or damaged. Opt for sealing designs with enhanced performance, such as double‑lip seals or labyrinth seals, and, if necessary, add dust shields. Improve installation and maintenance conditions to ensure cleanliness during unpacking, assembly, and relubrication. In dusty environments, shorten the grease‑change interval and increase the frequency of seal inspections.

4. Measures to Address Damage to Raceway and Roller Surfaces
After disassembly, inspect the raceways and roller surfaces, using a magnifying glass or profilometer to assess the extent of damage. Minor scratches and pitting can be repaired by lapping with a fine oilstone along the raceway direction, removing high spots and burrs. In cases of fatigue spalling, deep cracks, or extensive damage, replace the bearing; do not continue to use it. When replacing, analyze the root cause of the damage and implement targeted improvements to lubrication, sealing, or load conditions to prevent recurrence. During installation of a new bearing, strictly adhere to established procedures to avoid hammering or impact.

5. Measures to Address Poor Installation Accuracy
Disassemble the bearing and inspect the journal and housing bore for dimensional accuracy, geometric tolerances, and surface roughness. If any deviations exceed specifications, repair or replace the shaft and housing to ensure that all fit dimensions remain within allowable limits. During reinstallation, use a dedicated press‑fit tool and apply force evenly to prevent misalignment of the raceway. Employ a laser alignment instrument or dial indicator to check coaxiality; adjust if deviations exceed acceptable tolerances. Prior to installation, clean the mating surfaces and remove burrs and foreign contaminants. After installation, verify rotational flexibility and precision; only proceed with operation if the results meet the required standards.

Rotational stiction in crossed roller bearings results from the cumulative effect of multiple factors; excessive preload and lubrication failure are common causes, while foreign‑object intrusion and surface damage often stem from inadequate preventive maintenance. Addressing stiction requires a systematic troubleshooting approach—starting with the simplest issues and progressing to more complex ones, and working from the exterior inward. Begin with preload adjustment and lubricant replacement, then move on to disassembly inspection and precision repair. Establishing a condition‑monitoring–based preventive maintenance regime—regularly assessing friction torque, vibration, and temperature trends—and intervening at the earliest signs of stiction is the key to preventing severe bearing damage and ensuring long‑term equipment reliability. Although rotational stiction is not a catastrophic failure, it serves as an important indicator of bearing health; timely and accurate diagnosis and corrective action can significantly extend bearing service life and reduce overall equipment lifecycle costs.

Crossed Roller Bearing Selection Guide: Three Key Parameters Determine Precision

Crossed roller bearings, owing to their high rigidity, excellent rotational accuracy, and compact design, are widely employed in applications that demand stringent motion precision, such as industrial robots, machine tool rotary tables, and medical equipment. However, improper selection can lead to increased equipment vibration, larger positioning errors, and even premature bearing failure. This article focuses on precision—the primary performance requirement—and outlines the selection rationale for crossed roller bearings from three key perspectives: precision class, preload setting, and mounting fit tolerances. Drawing on years of industry experience, Jiu Liang Bearings recommends prioritizing these three parameters during the selection process, as they directly influence the final output accuracy in practical engineering applications.

1. Accuracy Class: The essence of classification is to control rotational error.
Precision grade is the most fundamental criterion for selecting crossed roller bearings, typically classified according to national or company standards as P0, P2, P4, P5, and so on. Each grade corresponds to specific tolerance limits for rotational runout and end-face runout between the inner and outer rings. As the precision grade increases by one level, both manufacturing costs and machining complexity rise significantly; therefore, it is essential to select an appropriate grade based on the actual requirements of the equipment, rather than blindly pursuing a higher grade.

1.1 Application Scenarios for Different Accuracy Levels
P0 level: Meets general transmission and positioning requirements, commonly used in handling robots and simple indexing tables.
P2/P4 grade: Suitable for precision positioning applications, such as the fourth axis of small machining centers and the rotary axis of laser cutting machines.
P5 grade and above: Designed for applications requiring high dynamic response, such as semiconductor packaging equipment and precision rotary stages in measurement instruments. Jiu Li Bearing’s engineering team has observed in real-world projects that many users select P4‑grade bearings for applications that should instead use P2‑grade bearings, resulting in unnecessary costs; conversely, choosing lower‑grade bearings when high precision is required can compromise the overall system accuracy.
1.2 “Accuracy Stability” to Consider During Selection
In addition to initial precision, it is also important to consider precision retention. High‑grade bearings are subject to stricter controls in areas such as material heat treatment and rolling element consistency. If the equipment operates for extended periods under heavy loads or at elevated temperatures, it is advisable to prioritize bearing models that have undergone specialized thermal‑stability treatments, thereby preventing rapid precision degradation caused by material creep.

2. Preload: Determines the balance between rigidity and rotational accuracy.
Crossed roller bearing
Preload refers to the axial force applied to a bearing during installation, with the aim of eliminating internal clearance and enhancing bearing stiffness. Crossed-roller bearings typically employ a preloading method using either a small clearance or an interference fit. The magnitude of the preload directly determines the bearing’s deformation, vibration levels, and temperature rise under operating conditions.

2.1 Selection of Negative and Positive Clearance
Negative clearance (preloaded condition): Ensures continuous, tight contact between the rolling elements and raceways, significantly enhancing stiffness. This configuration is well suited for applications requiring high positioning accuracy and vibration resistance, such as grinding‑machine spindles and radar turntables. However, negative clearance increases friction torque and raises operating temperatures, so caution is advised in high‑speed applications.
Positive clearance (light preload or no preload): Suitable for applications with high rotational speeds and small load variations, it helps reduce heat generation but offers relatively low stiffness. Examples include light‑load indexing tables or low‑speed scanning mechanisms.
2.2 Engineering Estimation of Preload Magnitude
Preload is not always better when it’s higher. Excessive preload can lead to contact stresses between the rolling elements and raceways that exceed allowable limits, thereby reducing fatigue life; too little preload, on the other hand, fails to effectively suppress micro‑vibrations. As a general guideline, select a preload within the range recommended in the bearing catalog based on bearing size and expected load, and verify it through practical testing. When equipping precision rotary tables, Jiu Li Bearings typically uses a preload range of 3% to 8% of the rated dynamic load, which customers can fine‑tune according to their specific operating conditions.

3. Fit Tolerances in Assembly: The Overlooked Silent Killer of Precision
Many users focus on the bearing itself while overlooking installation fit. The machining tolerances, roundness, and cylindricity of the shaft journal and the bearing housing bore directly determine the amount of deformation the bearing experiences after installation. Even if the bearing itself boasts high precision, an excessively tight or loose fit can still lead to additional runout and noise.

3.1 Principles for Selecting Fit Types
Inner ring–shaft fit: For rotating shafts, the inner ring is typically fitted with an interference fit, with a recommended tolerance class of js6 or h6; for fixed shafts, a transition fit may be used. If the interference is excessive, the resulting expansion of the inner ring can alter the contact angles of the rolling elements, thereby reducing precision.
Outer ring–housing fit: Use an interference fit (H7/h6 recommended) when the outer ring is to be rotated, and a clearance fit (G7 or F7) when the outer ring is to be fixed. Note that the outer ring of crossed roller bearings typically features a mounting flange or tapped holes; excessive fit clearance can readily lead to fretting wear.
3.2 Geometric Tolerance Requirements for the Mounting Surface
It is recommended that the perpendicularity between the shaft shoulder and the housing end face relative to the bearing mounting surface be maintained within 0.01 mm, and the coaxiality should be kept within 0.02 mm. If these tolerances cannot be met during assembly, consider employing a self-aligning design or a flexible compensation solution. In field measurements, a dial indicator is typically used to perform runout checks on the mounting datum surface, ensuring that deviations remain within the bearing’s allowable limits.

4. Mutual influence among the three parameters
Precision grade, preload, and mounting fit are not independent variables. For example, pairing a high precision grade with a relatively tight preload can significantly enhance system stiffness, but it also amplifies the adverse effects of installation errors. Conversely, when mounting fit tolerances are tightly controlled, the requirements for the bearing’s own precision grade can be appropriately relaxed, thereby reducing costs. Jiu Liang Bearings recommends that users, during the selection process, work backward from the equipment’s target positioning accuracy to determine the appropriate ranges for each parameter, and, if necessary, employ finite element analysis for verification.

4.1 A Typical Example of Selection Logic
Clearly specify the equipment’s repeat positioning accuracy (e.g., ±3 arcseconds).
Select the radial and axial stiffness of the bearing based on the load and rotational speed.
Select P2-grade bearings and apply a preload with a negative clearance of 0.005 mm.
Design the tolerance zones for the journal and the housing bore, and specify a surface roughness of Ra ≤ 0.8 μm.
Conduct actual running-in tests during the prototype stage and adjust the preload.
This process has proven effective at Jiuliang Bearing when supplying components to numerous CNC machine tool manufacturers, thereby eliminating the need for repeated rework caused by parameter mismatches.

FAQ: Common Questions About Selecting Crossed Roller Bearings
Q: Can crossed roller bearings completely replace cylindrical roller bearings?
A: They cannot be used as direct replacements. Crossed‑roller bearings, with their cross‑arranged rollers, can simultaneously handle radial loads and bidirectional axial loads, offering higher stiffness; however, their maximum permissible speeds are generally lower than those of cylindrical roller bearings. A case‑by‑case assessment based on the specific operating conditions is required.

Q: Can preload adjustment be performed on-site during assembly?
A: Some models can have their preload adjusted via shims or nuts, but for most crossed roller bearings, the preload is determined by the internal design at the factory and cannot be altered on-site. It is recommended to specify the desired preload value during the selection phase and have it confirmed by the supplier.

Q: After installation, unusual noises occur—what could be the cause?
A: The most common causes are excessive interference fit leading to rolling element seizure, or poor cleanliness of the mounting surfaces. It is recommended to disassemble the unit and re‑inspect the fit tolerances and the geometric deviations of the mounting surfaces. If the issue persists, the bearing itself may be damaged.

Summary: The selection of crossed roller bearings revolves around precision, with the key parameters being the precision class, preload, and mounting fit tolerances. Neglecting any one of these can result in substandard equipment accuracy or a shortened service life. It is recommended to consider these three factors as an integrated whole from the outset and to validate them against actual operating conditions. Jiu Liang Bearings offers comprehensive support, from parameter matching to on-site installation guidance, helping users maximize the performance of crossed roller bearings.

What are the applications of constant-section thin-wall bearings?

A thin-section bearing is a precision bearing characterized by an extremely thin cross-section, typically manufactured from thin-walled steel or other alloy materials, and designed to support radial loads on rotating shafts. This type of bearing plays a critical role in a wide range of applications.

Specification for Cleaning and Relubrication of Thin-Walled Bearings

Due to their compact structure, light weight, and high load-carrying capacity, thin-wall bearings are widely used in aerospace, precision machinery, robotics, and other fields. However, during operation, these bearings are prone to contamination from dust, oil residues, and abrasive particles, which can lead to inadequate lubrication, increased operating friction, and even bearing failure. Therefore, regular cleaning and relubrication are essential measures for maintaining bearing performance and extending service life. This article provides a detailed overview of the standardized procedures for cleaning and relubricating thin-wall bearings.