Maintenance

Linear Bearings: Costly Mistakes to Avoid and Maintenance Tips

In an industry increasingly relying on automation, plants and facilities need to recognise the importance of predictive maintenance in balancing their books and take the necessary steps to prioritise the maintenance of their machines. Specifically, in linear motion technology, it is crucial to ensure proper and timely lubrication for linear bearings, as with all bearings, to minimise unscheduled downtime. Investing in the maintenance of your linear bearings can lead to higher returns in the long run. To assist with this, we have compiled a list of the four most common mistakes and how to establish proper maintenance procedures for your linear bearings.

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5 Common Mistakes in Maintaining Linear Bearings

Inadequate or improper lubrication is one of the main causes of failures in linear motion technology. Proper lubrication of linear bearings is essential for prolonging their lifespan and performance, significantly impacting your facility’s output.

Mistake 1: Under-Lubricating Your Linear Bearings

Lubrication is an important process that helps reduce friction, prevents machine wear and tear, and protects them against corrosion and contaminants. When linear bearings are under-lubricated, heat can be generated from the friction between moving parts.

The usual practice is to perform preventive maintenance weekly or monthly. You can use automatic lubricators to regulate this process and reduce your workload, especially for systems that are difficult to access. However, this alone may not be sufficient and could lead to bearing failure in the future.

Instead, we recommend using a strategic combination of both preventive and predictive maintenance. In predictive maintenance, lubrication is scheduled as needed. We discourage only lubricating your linear bearings when the schedule dictates. Proper monitoring and measurement of friction levels should be conducted periodically using ultrasound instruments to gather accurate data for maintaining the best conditions for linear bearings.

Mistake 2: Over-Lubricating Your Linear Bearings

Over-lubrication can lead to malfunctions in your linear bearings. Applying too much grease can cause contamination and heat to accumulate in the bearing housing.

Excessive grease can fill up the bearing cavity over time. Without relief ports, the seals may blow through and leak out of the housing, creating an opportunity for external contamination.

The build-up of excessive grease creates pressure between the rolling elements and the outer race, resulting in more force needed for the bearing to move. Additionally, too much grease causes heat from fluid friction; unlike oil, grease does not transfer heat effectively. As the temperature increases, the grease degrades due to over-churning. Having relief points to remove excess grease makes the over-lubrication of your linear bearings a less critical issue compared to under-lubrication.

Mistake 3: Incorrect Choice of Lubrication

Choosing the right lubrication for linear bearings is crucial for ensuring optimal performance, durability, and reliability of machinery.

One common mistake is underestimating the operating conditions and requirements of the application. Failure to consider factors such as load capacity, speed, temperature variations, and environmental conditions can result in the use of lubricants that are either too thick or too thin, leading to inadequate protection or excessive friction and wear on the bearings.

Another critical error is overlooking compatibility issues between the lubricant and the bearing materials. Some lubricants may contain additives or chemicals that can degrade or corrode specific bearing materials, leading to premature failure and costly downtime. Inadequately long-lasting or stable lubricants might require frequent reapplications, which increases maintenance costs and the risk of human error.

Moreover, making cost-driven decisions can result in choosing subpar lubricants. Opting for cheaper alternatives without considering their performance characteristics can compromise the efficiency and overall lifespan of the linear bearing, ultimately leading to higher costs for repairs and replacements.

ORAPI RECOMMENDS:

CT 609

Multi-Purpose Bearing Grease

CT 609 is a very high-quality translucent grease designed for use in the food and food-processing industries.

CT 609 complies with NSF H1 and INS H1 standards for unintentional contact with foodstuffs. It contains no toxic substances, is hypoallergenic, and possesses high mechanical stability and good thermal stability.

CT 609 bonds well, is infusible (no drop point), and can be used by centralized lubrication systems.

Mistake 4: Inadequate Maintenance

For most applications, grease must be reapplied at scheduled intervals because the “old” grease dries out and oxidises. When the bearings are re-greased, the contaminated “old” grease will be pushed out of the bearing housings.

Developing a comprehensive maintenance schedule for your linear bearings can be challenging because it’s difficult to predict the exact amount of lubrication to apply. Variables to consider include the size and speed of the linear bearing, its operating temperature, and the number of operation hours.

Some systems may require lubrication on a weekly, monthly, or daily basis. It is recommended to thoroughly clean your bearings at least once a year and apply a new coat of grease. Before disposing of the “old” grease, make sure to send it to the lab for analysis. Analytical data is the best way to fine-tune the effectiveness of your greasing schedules.

Mistake 5: Neglecting Environmental Factors

Failure to consider the operating environment can significantly impact the performance and lifespan of linear bearings, leading to unexpected failures and increased maintenance costs. Environmental conditions such as temperature extremes, humidity, dust, and chemical exposure can affect linear bearings. Neglecting these factors can result in improper bearing selection or inadequate protective measures.

Temperature Extremes

High temperatures break down lubricants, causing more friction. Low temperatures thicken lubricants, affecting smooth movement. Use bearings and lubricants suited to your application’s temperature range.

Humidity and Moisture

Exposure to moisture and high humidity can cause corrosion and rust, impacting bearing performance. Bearings in such environments should be made from corrosion-resistant materials and properly sealed to prevent moisture ingress.

Dust and Contaminants

Operating in dusty or dirty environments can lead to more wear and potential failure in bearings. Using sealed or shielded bearings and maintaining proper cleaning routines can help mitigate this risk.

Chemical Exposure

It’s important to choose bearings and lubricants that are compatible with the chemicals present to avoid premature failure.

Vibration and Shock Loads

Bearings exposed to high vibration or shock loads must be designed to withstand these conditions to avoid damage and reduce operational life.

Linear Bearing Maintenance Tips

As previously mentioned, bearing lifespan largely depends on proper and timely maintenance. In fact, it is estimated that up to 80% of bearing failures result from issues related to lubrication. While this percentage sounds high, the maintenance process is not difficult. Many companies face challenges due to inadequate standard operating procedures (SOPs) and a lack of strategic maintenance schedules.

Step 1: Proper Pre-Cleaning

Begin by removing any remaining grease, corrosion protection coatings, and oils. This step is essential for preserving the equipment’s lifespan and preventing the introduction of unwanted contaminants.

Note: If the product comes pre-coated, this step may not be necessary, provided that the coating is very thin and compatible with your lubricants.

For best results, we suggest using cleaning solvents that do not leave any residue.

Step 2: Ensure Correct Fill Quantities

Please pay special attention to this step as it often leads to over- or under-lubrication of your linear bearing. The quantity of lubricant you apply is important for providing consistent lubrication to the contact surfaces between metals.

Applying too much lubricant causes increased heat generation and friction in your bearing housings. On the other hand, applying too little means that not all of the contact surfaces are evenly lubricated, leading to wear and tear and a shorter operating life.

When the proper fill quantities are achieved, the contact surfaces of the bearings should have sufficient lubricating films. The correct amount is determined on a case-by-case basis, and we will elaborate on this in the next step.

Step 3: Calculate Bearing Free Space

Determining the appropriate amount of lubricant to be used in a bearing is known as the Calculation of Bearing Free Space. This involves specifying the lubricant as a percentage of the bearing’s free space according to industrial standards. This critical step ensures the longevity and optimal performance of the bearing by preventing over-lubrication or under-lubrication.

The exact fill quantities can be obtained through direct communication with the bearing manufacturer via a phone call or email, which provides precise and tailored information. Alternatively, a grease calculator can be used to estimate the required lubricant amount. However, it should be noted that this method has limitations in accuracy and may not be as reliable as consulting the manufacturer directly.

Step 4: Run-In Procedures

Grease the linear bearing elements to form a grease collar, ensuring an even distribution of the base oil where friction surfaces receive the optimal oil quantity.
Purge any leftover grease from your system.
Create a grease collar to deliver oil to the surface contact zone.
Let the system cool down to room temperature.
Restart the procedure at the last speed prior to the temperature spike.
Continue the above cycle until the maximum operating speed is achieved.

Step 5: Lubricating Your Bearings

Lubricate your linear bearings in a dry and clean environment to minimise contamination from moisture or debris. For smaller amounts, use a calibrated grease gun or a syringe. Rotate the bearings without load to distribute the grease evenly through the race.

Conclusion

Remember, proper maintenance of linear bearings is essential for equipment performance and lifespan. Balance lubrication and select suitable lubricants to reduce downtime and costs. Use a mix of preventive and predictive maintenance to enhance efficiency and profitability in operations involving linear motion technology.

GET YOUR COMPLETE LUBRICANRT & GREASE BUYING EGUIDE NOW!

We also have a full list of lubricants and greases in the guide

Linear Bearings: Costly Mistakes to Avoid and Maintenance Tips

5 Common Mistakes in Maintaining Linear Bearings

Mistake 1: Under-Lubricating Your Linear Bearings

Mistake 2: Over-Lubricating Your Linear Bearings