Machine Design
Boosting reliability with lubricating surfaces

Boosting reliability with lubricating surfaces

Any plant using linear motion requires maintenance workers to regularly apply lubrication to linear guides, because insufficiently lubricated mechanical components exhibit excessive wear, performance problems, and premature failure. However, manual lubrication practices can be pricey, due to recurring maintenance-personnel wages and the cost of the lubricant itself. Such lubrication expenses are even higher for remotely located grease fittings, or those requiring downtime for servicing.

One alternative for linear-motion applications is lubed-for-life or maintenance-free guides. Typically, these subcomponents incorporate lubrication storage and delivery systems to drastically reduce or even eliminate the need to reapply lubricant after bearings go into service. Their drawback is complexity and cost.

Yet another alternative is maintenance-free bearings with integrated mechanical features in the bearing slider that store and deliver oil. Such guides and ways abound, but are typically designed for either the longest possible maintenance-free intervals or design compactness.

A third linear-component lubrication option aims to meet both design objectives. These long-life maintenance-free linearmotion products are manufactured in roller-guide, ball-guide, and ball-splinebased shaft-guide versions. Track widths range  from 5 to 65 mm, with the largest guides offering a basic static load rating of 172,000„lb. All have lubricating elements of sintered-resin powder and a steel backing. The working resin surface has a porous structure that can be impregnated with copious amounts of oil; the elements are formed into either a plate or sleeve shape and integrated into the bearing’s slider. They then release the impregnated oil slowly through direct, continual contact with the linear guide’s internal rolling elements for maintenance-free operation to 20,000 km or  ve years — which is often the entire application life. All of the geometric iterations offer the same maintenance-free interval. Therefore, the engineer can choose the suitable product based on load type, duty cycle, and other application factors.

Let’s take a closer look at each style:

• Roller guides — Designed for applications requiring maximum stiffness and resistance to moment loads, these feature a slider on a balanced set of four cylindrical rollers. Here, the impregnated-oil element is fashioned into a plate housed just behind the slider’s end plates.

• Ball guides — These run on recirculating steel balls that run through a sleeve made from the oilimpregnated sintered resin. As the balls travel through the sleeve, they pick up oil and transfer it to the rail.

• Ball-spline guides — These incorporate an internal oilimpregnated plate-shaped element, so as the balls traverse this plate, they pick up oil — allowing both the balls and spline shaft to be lubricated.


© 2013 Penton Media, Inc.

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