Inexpensive maintenance and replacement of bearings can avoid a lot of expense; spending as little as £20 now could save tens of thousands in lost production later. Al Ng, director of engineering at Thomson Linear Bearings and Guides shares practical tips for effective maintenance and inspection to maintain a productive and reliable production line
While the cost of linear bearings is low, their performance is essential to the accuracy, throughput and reliability of critical production machines. Even if using high quality bearings designed for longer life, these are wear parts and will eventually need replacing. Bearing failure can cause lengthy unplanned downtime and potentially damage a machine, or lead to product defects and quality control problems.
The cost of a linear bearing is insignificant compared with the costs associated with its failure. Regular lubrication of bearings is inexpensive and essential to protect machinery, keep production efficient and to help avoid early failures. A typical maintenance cycle is every year or 100km of travel but consideration should be given to the application and environmental conditions to which the bearing is subjected. Even with the best care, bearings will eventually fail and, to avoid unnecessary costs and downtime, it makes good business sense to have a programme to replace them before this happens.
A bearing will last for longer and require less maintenance if it is correctly selected and sized for the application – allowing for required accuracy and load. Ninety per cent of bearings last longer than their L-10 life and this gives some guidance to a replacement schedule. Ten per cent, however, will fail before this time and harsh external conditions or starving of lubrication will make this figure higher.
Early signs of failure
Bearings which are starting to show signs of needing replacement impact the efficiency of a process and can affect production throughput. If left, failure can cause significant damage to the machine and lead to costly, unplanned production shutdowns. For example, one manufacturer operating a plasma cutting machine noticed that its bearings were starting to “ride a bit rough” but did not take its machine off line for a more thorough inspection. In time, the machine failed and the production line was stopped with lost revenue estimated at £124,000 per day. Regularly observing the following simple indicators can save time and cost as well as keeping production running smoothly and efficiently:
• Listen. A bearing that is coming towards the end of its life will make more noise. Listen for clicking or any scratching sounds from the machine.
• Look. Bearings which are not working efficiently may make a machine stutter. Visual inspection may also show grooves on the shaft. Metal particulates on the surface of the shaft or rail are also a concern.
• Feel. Increased vibrations in the machine are a warning sign of bearing failure. Simply placing a hand on top of a rig and feeling for these vibrations will give a good indication of the state of the bearings. A thin layer of lubricant should be felt by running a finger over the shaft and rail. If this is dry, the bearing requires more lubricant.
Make use of planned shutdown
At any time where there is a scheduled shutdown it makes sense to check linear bearings and replace them for a minimal cost if there are any early signs of failure. Remove them from the machine and look inside – if they are fairly dry and the lubrication discoloured it would be wise to replace them while there is the opportunity as part of planned maintenance. When bearings need replacing any delay could be critical. Ensuring the correct spares stock is maintained is another important aspect for smooth running operations.
All of the failure indicators give a measure of whether bearing maintenance is required but sometimes a failure can still occur without symptoms showing. Alongside an appropriate maintenance schedule for bearings, train operators and maintenance teams to spot the early signs of failure as part of day-to-day routines. Ensure bearings have been selected and sized to match an application and have a planned replacement programme to give the best possible chance of avoiding unexpected, costly breakdowns.
Proactive maintenance and taking straightforward steps to monitor and check bearing performance as part of a standard routine is good practice. Looking after and regularly replacing this minimal cost part of a process will help maintain machine accuracy, efficiency, productivity and reliability. Spending just a little time and money really could save your business a great deal.
Thomson has more than 60 years of motion control innovation and quality and has among the widest ranges of linear bearings and accessories, all engineered for low friction and smooth, accurate straight-line motion with distributors throughout the UK. Thomson invented the linear Ball Bushing bearing in 1945 and is one of the industry’s premier producers of linear Ball Bushing bearings and profile rail bearings.
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