THK business manager, South Africa, Graham O’Donoghue, reviews the technology behind the company’s Caged Ball system and its benefits.
THK started the linear ball rolling during the 1970s with the introduction of the LM Guide linear motion system. The company has remained at the forefront of linear motion technology, and has over the decades, developed a number of new systems, with some of these becoming industry standard across the globe.
THK's new technology Caged Ball was recently unveiled and following the initial launch, has developed into a complete new generation of linear motion products with a number of advantages. Most notably these include more than 50% reduction of noise levels, significantly increased operating speeds, extended lubrication life, substantial reductions in rolling resistance variation and low particle emissions.
O'Donoghue discusses some of the differences between Caged Ball Linear Motion Technology and conventional systems: "It is widely acknowledged that ball-to-ball impacting is found in virtually all non-caged linear motion systems. This point-to-point, high stress contact will shear rapidly through any lubrication film present, causing metal to move against metal which, in turn, generates noise, friction, heat, accelerated wear and debris. This resultant particle debris from the continual impacting of the balls further accelerates the degradation of internal components.
Typically, this degradation is controlled and bearing life optimised by the frequent re-lubrication of the system. Most linear motion manufacturers generally recommend lubrication approximately every 100 km of travel which, on a busy machine tool, packaging machine or printing press, for example, could mean regular downtime purely for the purposes of bearing lubrication.
Until recently, the perfectly logical response to this would have been that the requirement for frequent lubrication is inherent to the nature of the product and is simply accepted by industry as a necessary evil. However, this is no longer the case as the technology of the THK Caged Ball linear motion system significantly reduces lubrication requirements.
In essence, the Caged Ball linear motion system is a non-contact, ball retaining mechanism that eliminates any possibility of ball-to-ball impact. Each ball is held in a position equidistant to its neighbour by the retainer, which is manufactured from a high performance and hard wearing lubricant-compatible material. A 'grease' pocket is established in the space between each ball and retainer, ensuring a continual film of lubrication to the ball, which can no longer be disrupted by metal-to-metal contacts.
The elimination of contact reduces metallic noise, significantly reducing the operational dBA level. For example, a conventional linear motion guide operating at a speed of 70 m/min will typically generate noise in the region of 65 dBA. The Caged Ball linear motion system, operating at the same speed, reduces noise to less than 50 dBA and with increasingly stringent health and safety legislation concerning noise in the workplace, the Caged Ball linear motion technology can significantly contribute to meeting health requirements.
Low noise levels are of equal importance for applications from machine tools to medical equipment; in the latter instance especially, minimal noise, combined with the overall 'clean' construction of the device, can produce important environmental benefits.
Basically, all the benefits of the technology stem from the equidistant retention of the balls and the maintained lubrication film. For example, this ensures that the balls move smoothly, regardless of mounting position, significantly reducing fluctuations in rolling resistance by a factor of up to 10, compared with conventional technology; in turn, allowing for higher degrees of accuracy to be achieved. Preventing adjacent balls from impacting on each other, the Caged Ball linear motion system reduces internal friction and enables high speed performance through reduced heat generation due to lower bearing stress.
All these factors, combined with the virtual elimination of bearing wear and the potential of 40 times increase in lubrication intervals, have resulted in Caged Ball linear motion systems that provide long term, virtually maintenance free operation.
Originally introduced specifically on the LM Guide type SSR, the technology is already proving itself in a variety of applications world wide. THK has increased this range by developing the SNR/SNS, SHW, SRS and SHS type LM Guides. Each product in the range has unique benefits and features to suit a variety of applications and environments with the additional benefits of Caged Ball technology.
SKF South Africa is the official distributor of the THK range of linear guides in sub-Saharan Africa.
For more information contact Graham O'Donoghue, SKF South Africa, +27 (0) 82 565 3189, [email protected], www.thk.com
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