/// METROLOGY \\\


Linear encoders provide immunity to shock


A new range of linear encoder products feature isolation from the effects of shock and vibration when attached to machinery


In addition, they are also protected against M


etrology specialist, Renishaw has in- troduced an innovative enclosed lin- ear absolute encoder range for use in


harsh environments such as mounted on ma- chine tools. The FORTiS design is built on the company’s


Resolute encoder technology and provides high resistance to the ingress of liquids and solid debris contaminants. It also features an extruded enclosure with longitudinally at- tached interlocking lip seals and sealed end caps. The readhead body is joined to a sealed optical unit by a blade, which travels through the lip seals along the length of the encoder. Linear axis movement causes the readhead and optics to traverse the encoder’s absolute scale, which is fixed to the inside of the en- closure, without mechanical contact. This ab- sence of any contact forms the basis of its resistance to shock and vibration.


Enclosure design \\\ There are two different extrusion profiles to


suit different space requirements. The FOR- TiS-S is a standard-sized encoder, available with measuring lengths from 140mm to 3040mm and is installed directly to a ma- chined surface via flexure holes in the extru- sion’s body. The FORTiS-N encoder has a measuring length from 70mm to 2040mm and


features a narrower cross-section extrusion and a more compact readhead to enable in- stallations in confined spaces. This model can be mounted directly to a machined surface for greater rigidity. According to Ian Eldred of Renishaw, a great


deal of R&D effort has gone into the design of the encoder and as a result, it delivers high repeatability, reduced hysteresis and im- proved measurement performance. “Five years of accelerated life testing under


the harshest conditions has enabled us to re- fine the product to the extent that it offers ex- cellent resistance to wear and machine tool lubricants, superior sealing and ingress pro- tection up to IP64 when combined with air purge,” he says.


Mass damping \\\ In addition, the encoders also feature inte-


grated, specially-designed tuned mass dampers that deliver 30g vibration resistance and push the limits of what enclosed en- coders can endure. Eldred says that the FORTiS absolute en-


coder series is designed to be robust and re- sistant to a wide range of mechanical shock and vibration effects. “All FORTiS-S and FORTiS-N encoders when


installed with mounting spars, are rated up to 30g, which ensures dependable metrology for even the harshest environments and de- manding motion control applications,” he says.


A new range of linear encoders provides users with the ability to mount them directly to machine tools without being affected by shock and vibration, top; flexure holes in the body of the FORTiS-S encoder enable it to be attached directly to equipment for measuring lengths of up to three metres, above


2021 /// Climatic & Vibration Testing \\\ 7


contamination by a further level of sealing: the readhead optical unit, which runs inside the enclosure, is itself sealed to IP67 to pre- vent contamination by liquids, swarf and other debris. Moreover, improved sealing of the FORTiS encoder enclosure reduces air leakage from the air purge system, resulting in lower operating costs and greater system longevity. Unlike traditional installation methods, pe-


ripheral diagnostic equipment is not essen- tial. Renishaw’s patented set-up LED and carefully designed installation accessories en- sure intuitive and right-first-time installation that is substantially faster than more con- ventional systems, even in restricted loca- tions. For enhanced functionality, installers can


connect the Advanced Diagnostic Tool, ADTa- 100, via a standard USB connector, to a PC run- ning Renishaw’s ADT View software. This provides a graphical interface of advanced di- agnostic information, including key encoder performance parameters such as signal strength along the axis length. C&VT


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