LINEAR MOTION FEATURE
DISPELLING THE MYTHS surrounding linear guidance systems
Many engineers are comfortable with rotary bearing technology but view linear as complicated and over-engineered with complex maintenance requirements. Bob Love, business development manager at Schaeffler UK, dispels the common myths about linear bearing technology
L
inear systems are a key part of production
machinery and plant automation. If your linear guide stops, your machine will stop too. If your linear systems are not providing the low friction movements they should be, you will use more power, increasing the strain on your motors and drive systems, which in turn increases bearing loads and reduces component life. However, while many engineers are
comfortable with rotary bearing technology, they often view linear motion systems as complicated and over- engineered with complex maintenance requirements. As a result, selecting the right linear guidance system for an application can be daunting. Contacting a reputable supplier to
discuss the application will enable the right solution to be found. The supplier can also inform the customer exactly what is and isn’t possible and can provide valuable advice and guidance on integrated systems such as lubrication, sensors, mounting arrangements, corrosion-protected coatings and materials, as well as sealing arrangements.
GUIDANCE SYSTEMS Linear 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. These systems are responsible for the guidance and transmission of force between machine parts moving in a translational direction and so have a significant effect on the overall performance and accuracy of a machine. The most common types are: • Shaft • Track Roller • Profile Rail/Monorail • Flat Cage
Shaft guidance system
• Miniature. Typically, a linear supplier will offer a range of accessories and sealing arrangements for the different bearing types depending on the specific application requirements. 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: power tools (mitre
saws); fitness/exercise equipment. Track roller guidance systems: These
consist of carriages, composite guideways and track rollers that combine to achieve versatile and 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, and are highly suitable for automated, multi-axis
handling systems. Typical applications:
multi-axis and gantry arrangements;
machine guards; packaging machinery; automatic doors. Monorail/Profile rail guidance systems: These systems comprise one or more carriages running on a profiled
Ball monorail guidance systems
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. These systems offer extremely high load
carrying capacity, rigidity and accuracy. Typical applications: machine tool axes and tool changers; robots; packaging machinery; paper processing machinery; medical equipment; measuring equipment; palletisers & other mechanical handling systems. 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: gauging
equipment; applications with very low section height. 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: compact medical
equipment; 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 linear guidance systems from Schaeffler can be supplied with precision accessories to enhance the performance and, in some application conditions, achieve maintenance-free operation and a reduced Total Cost of Ownership (TCO). 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 linear accessories such as wipers, plugs, clamping elements, guideway covering strips, emergency braking devices and vibration damping elements.
Schaeffler T: 0121 313 5870
www.schaeffler.co.uk
DESIGN SOLUTIONS | JUNE 2016 21
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