FEATURE LINEAR MOTION
SMART LINEAR GUIDES TAKE the strain off machine operators
Linear guides are available in a variety of configurations to suit different applications. Sally Sillis, Technology Centre manager at Schaeffler UK, outlines the main types, their typical applications and the latest smart versions that offer integrated sensors and vibration analysis
L
inear guidance systems use rolling elements (balls, rollers, track rollers)
between moving guidance elements that maintain a direction of motion along a linear track (profiled rail, guideway or cylindrical shaft). As these systems are responsible for the guidance and transmission of forces between machine parts moving in a translational direction, they have a significant effect on the overall performance and accuracy of a machine. Production machines and plant automation systems rely heavily on linear guides. If these stop or fail prematurely, the machines will stop too, resulting in costly production downtime. If linear systems are not providing the low friction movements they should be, plants will use more power, increasing the strain on motors and drive systems, which in turn increases bearing loads and reduces component life.
SHAFT GUIDANCE SYSTEMS These are relatively simple guidance mechanisms due to their low-to- moderate accuracy. One of the oldest guidance systems based on rolling elements, these consist of a hardened and ground shaft and one or more low friction linear ball bearings, which run back and forth on the shaft supporting high radial loads. Typical applications include hand tools, power saws and fitness/exercise equipment.
MONORAIL/PROFILE RAIL GUIDANCE SYSTEMS These systems comprise one or more carriages running on a profiled guideway. The rolling elements are guided by a rolling element recirculation system with either balls or rollers in full complement (maximum possible number of rolling elements) sets. Benefits include extremely high load carrying capacity, rigidity and accuracy. Some suppliers now provide monorail guidance systems with integrated sensors
10 MAY 2018 | DESIGN SOLUTIONS
and vibration analysis to offer automatic relubrication. Schaeffler, for example, has integrated this functionality into its linear recirculating bearing and guideway assemblies – for both ball and roller types. Each individual linear axis is provided with precisely the level of relubrication it needs based on its loads and requirements. An electronic evaluation system allows up to six carriages to be monitored on each axis. The system (DuraSense) reliably
prevents both insufficient lubrication and over-greasing, which extends machine operating life and reduces the rate of failure. Relubrication system failures due to defective lubrication units, leaking hoses or blocked lubricating nipples are also reliably detected. Complex monitoring using pressure sensors such as those used in centralised lubricating systems is not required. The system thus protects even heavily interconnected systems against very costly downtimes. Implementing monorail guides with fully automated lubrication, and the monitoring of the lubrication conditions, signifies a major step forward for manufacturers and operators of production machinery. Operators are no longer required to carry out manual lubrication work and machine manufacturers are no longer dependent on the often-limited control options offered by a centralised lubricating system. Typical applications for monorail guidance systems include machine tool axes, tool changers, robots, food and packaging machinery, automotive production/assembly lines, paper processing machinery, medical equipment, measuring equipment, and ‘motion axes’ in intra-logistics.
FLAT CAGE GUIDANCE SYSTEMS These systems are ideal for oscillating motion and applications that require high load carrying capacity, high rigidity and accuracy with restricted stroke length and very smooth running. Typical applications include gauging equipment and applications with very low section height.
Some suppliers now offer monorail guidance systems with integrated sensors and vibration analysis to offer
automatic relubrication. Each individual linear axis is provided with precisely the level of relubrication it needs based on its loads and requirements
TRACK ROLLER GUIDANCE SYSTEMS These consist of carriages, composite guideways and track rollers that combine to achieve versatile, cost-effective designs. The systems are lightweight in construction and offer low noise, high speed and long travel distances. They support forces from all directions except in the direction of motion. Typical applications include automated handling systems, multi-axis gantry arrangements, machine safety guards, automatic doors and packaging machinery.
MINIATURE GUIDANCE SYSTEMS These are characterised by their extremely compact designs, high accuracy, high rigidity and high load carrying capacity with unlimited stroke, subject to rail length. Typical applications include compact medical equipment and machinery for manufacturing electronic components.
CUSTOM AND MAINTENANCE-FREE SYSTEMS In some cases, linear guidance systems need to operate in special conditions or harsh environments such as high temperatures, high speeds, high accuracy, low noise or unusual load conditions. All Schaeffler’s linear guidance systems can be supplied with precision accessories to enhance the performance of the product and, in some application conditions, achieve maintenance-free operation and a reduced Total Cost of Ownership. These include lubrication systems, sensors and measurement devices, corrosion-protected coatings and materials, as well as enhanced sealing arrangements to protect against contamination. A reputable linear supplier should
also offer a range of linear accessories such as wipers, plugs, clamping elements, guideway covering strips, emergency braking devices and vibration damping elements.
Schaeffler
www.schaeffler.co.uk
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