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Enclosed linear encoders ‘push endurance limits’

01 February, 2021

The British encoder manufacturer Renishaw has launched a series of enclosed, absolute linear encoders for use in harsh environments such as machine tools. It claims that the Fortis encoders deliver high repeatability, low hysteresis and good measurement performance using a non-contact design that does not need a guide carriage.

The encoders, based on Renishaw’s Resolute technology, come in two profiles, both of which can be installed directly onto machined surfaces. The standard Fortis-S versions cover measuring lengths from 140–3,040mm, while the narrower Fortis-N models span lengths from 70–2,040mm and have smaller readheads, allowing installation in confined spaces.

Ian Eldred, principal mechanical engineer for the Fortis range, says that the encoders are culmination of years of r&d, including five years of accelerated life testing under the harshest conditions. This work resulted in new lip seals that resist wear and aggressive machine tool lubricants, and offer protection up to IP64, when combined with air purge.

The optical readhead, which runs inside the enclosure, is sealed to IP67 to prevent contamination by liquids, swarf or other debris. Effective sealing reduces air leakage from the air purge system, resulting in lower operating costs and longer operating lives.

The encoders are designed to resist a wide range of shock and vibrations and incorporate special tuned mass dampers. They can handle acceleration rates up to 30 g, ensuring they will operate in demanding environments and motion control applications. According to Eldred, they “push the limits of what enclosed encoders can endure”.

Renishaw’s standard (top) and narrow enclosed linear encoders

Unlike traditional installation methods, peripheral diagnostic equipment is not needed. A patented set-up LED helps to ensure right-first-time installation which is said to be much faster than conventional systems, even in restricted locations.

The encoders support several serial communications protocols including BiSS C, BiSS Safety, Siemens Drive-CLiq, Fanuc, Mitsubishi and Panasonic.

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