Linear axes achieve step-change in performance

Paul Boughton
Festo is launching a family of electromechanical axes based on a radical new profile design that is claimed to provide unprecedented rigidity. Moreover, the new EGC axes are said to offer exceptional feed force, speed, acceleration and torque resistance. They are suitable for use in gantry-type materials handling systems and are likely to open up entirely new application areas for high-performance single- and multi-axis motion control.

Festo's EGC axes are the direct result of an extensive research and development programme to advance the performance of electromechanical drives. The outcome is said to be little short of spectacular: the new axes provide a performance gain of between 100 per cent and 200 per cent over their previous-generation counterparts, yet they cost 10 per cent less. Offering a choice of toothed belt or ballscrew drive mechanisms - with numerous variants in both formats - EGC axes enable OEMs and system integrators to easily choose an actuator that is optimally matched to their application needs. In many cases it is now possible to use a smaller axis and motor than was previously necessary, because the performance is so much higher.

The main body of every EGC axis is constructed from extruded aluminium; this has a novel computer-optimised cross-section, featuring an internal arch-shaped structure that provides exceptional rigidity and load-bearing capabilities, combined with very low mass. Unlike most competitive products on the market, the axes' stainless steel guide rail is mounted externally, allowing the moving carriage to accommodate large cantilever and offset loads that apply very high moments to the carriage. Carriage twisting moments of up to 185Nm can be accommodated.

The moving carriage is fitted with the latest high performance caged ball bearings for a long and trouble-free service life, and the fully sealed bearing cassette features grease pockets throughout its length. Festo also offers a number of optional guide scrapers and grease feed adapters for use with centralised lubrication systems. The top face of the aluminium carriage is fitted with helicoil inserts and centre holes to facilitate fast, accurate and reliable load mounting.

Festo offers the toothed belt version of the EGC axis with a choice of 50, 70, 80, 120 and 185mm wide profiles, and the three largest models can be supplied with standard stroke lengths of up to 8.5 metres. Different models within this range are capable of generating feed forces as high as 2500N and of handling speeds up to 5m/s and acceleration rates up to 50m/s2. The external guide arrangement also conveys another major advantage to the toothed belt versions of EGC axes; it results in the use of smaller belt pulleys, often obviating the need for a gearbox altogether. An innovative cover opening and securing mechanism allow the belt to be replaced without dismantling the axis, which helps reduce maintenance times and lowers service costs.

The ballscrew versions are suitable for applications with short cycle times, very high feed forces and extremely accurate and repeatable positioning. These axes are available with 70, 80, 120 or 185mm wide profiles and standard stroke lengths of up to 3m, and several models offer a choice of spindle pitches. The spindle itself features a noise-optimised design, and the body of the axis is fitted with a non-metallic, clip-in cover band to guard against the ingress of contaminants. Different models within this range are capable of generating feed forces as high as 3000N, and can provide positioning accuracies to within +/-20um.

Festo is also launching a new series of inductive position sensors for use with the EGC axes. Together with their cables, these fit flush within the body of the axis, and unusually, they look 'out' from the body to detect the presence of a flag plate on the moving carriage, instead of looking 'into' the actuator to detect embedded magnets. This makes installation and commissioning very easy, since both sensor and target are clearly visible at all times - and the sensors are equipped with LED indicators that can be seen from the top and side of the unit.

The new EGC axes are particularly easy to install thanks to a hollow drive pinion and a new design of elastomeric motor coupling featuring an expanding shaft; together these provide a simple, backlash-free connection. The flexibility of this arrangement is especially apparent on the toothed belt version - the motor can be mounted at either end and on either side of the axis, which means that users do not have to specify motor placement at the time of ordering, but can leave this decision until installation.

EGC electromechanical axes are available as standalone products or as part of complete motion control systems, as they are fully compatible with Festo's range of stepper and servo motors, as well as the company's modular multi-axis system. The axes can also be used with third-party motors; Festo can provide flange designs for these motors and even manufacture them if required. Festo also offers a wide range of accessories for use with EGC axes, including extra guide units, axial motor mounting kits, footmounts, adapter plates and a new drag chain connector.

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