- July 05, 2016
By Bob Love, Schaeffler UK
Linear systems are a key part of production machinery and plant automation. If your linear systems are not providing the low friction movements they should be, you will strain your motors and drive systems, which will increase bearing loads and reduces component life.
By Bob Love, Business Development Manager at Schaeffler UK
Many engineers are comfortable with rotary bearing technology but view linear as complicated and over-engineered with complex maintenance requirements. This article will help dispel the common myths about linear bearing technology.
Linear systems are a key part of production machinery and plant automation. If your linear guide stops, your machine will stop too, resulting in costly production downtime. 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.
Selecting the right linear guidance system for an application can therefore be a daunting task. While many engineers are comfortable with rotary bearing technology, they often view linear motion systems as complicated and over-engineered with complex maintenance requirements.
However, on most occasions, if engineers contact a reputable supplier of linear guidance systems to discuss their application, any potential issues can normally be resolved and a suitable solution found. Engineers can save themselves a lot of wasted design effort or prevent the system from being too costly or over-engineered. The supplier can also inform the customer exactly what is and what 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.
Linear Doesn’t Have to be Complicated
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 of linear guidance systems are:
- Track Roller
- Profile Rail/Monorail
- Flat Cage
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 systems 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 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 of the product 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 a range of linear accessories such as wipers, plugs, clamping elements, guideway covering strips, emergency braking devices and vibration damping elements.
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