Drive system extends the conventional linear motor principle

Written by: Paul Fanning | Published:

A linear transport that is claimed to unite the benefits of rotary and linear systems, save valuable space and offer huge flexibility is now available in the UK.

The XTS (eXtended Transport System) is a mechatronic linear transport system containing all functions necessary for operation: a modular, fully integrated linear motor with power electronics and position measurement in a single device, a mover as a moved part and a mechanical guide rail.

According to Beckhoff, the most diverse applications can be realised with these few, co-ordinated components. The desired geometries, lengths and radii are formed by the number and choice of the components. XTS enables individual product transport with a continuous flow of material and, due to the low construction volume, the energy efficiency and the size of a machine can be significantly improved.

In essence, the XTS is a linear motor that travels in a circle. It is modular in nature and offers arbitrary installation position and a length of 10m and more. In fact, though, according to Bradley McEwan, Beckhoff Automation's business development manager: "The only real limits on the system's potential size are voltage drops – ie the availability of power supplies – and bearing size."

As previously mentioned, perhaps the XTS' greatest benefit is the significantly reduced footprint required by machines that incorporate it. The possibilities are clear in comparison with acceleration and deceleration conveyor belts . These mechanically complex, space-consuming and correspondingly expensive belts are often required to maintain a uniform distance between – for instance – objects in a packaging line before they are transported for sealing. Thanks to XTS with its synchronised movers, no conveyor belts are necessary, resulting in a significant reduction in both costs and machine footprint.

XTS also enables the maximum possible utilisation of the machine footprint, as the circular movement allows travel in both directions as well as curves. Equally, complex cabling and drag chains are no longer required, while the position measurement system is already integrated.

Perhaps the most eye-catching features of the XTS, however, are the movers, which can accelerate, brake, position and synchronise. They can also take up absolute positions relative to one another, group themselves and accumulate, create clamping forces in motion, travel along curves as fast as along straights and even recover energy though regenerative braking.

The movers themselves are made of a light and solid aluminium alloy. They contain magnetic plates that , together with the coils of the motor module, generate a controlled driving force. The attractive forces of the magnetic plates are largely balanced by the opposed arrangement, so that the rollers and the rail do not have to absorb the comparatively high attractive forces of the magnets.

Thanks to their arrangement the rollers allow backlash-free travel on the straights and in the curves.The coating of the rollers causes very little running noise and is particularly low-wear without lubrication of the guide rail.

The centre of the encoder flag supplies a position signal to the motor module. Movers can be distinguished from each other by the encoder flags, which are made from a sturdy, lightweight glass-fibre reinforced material.

The motor module, the power electronics and the displacement measurement are built into the profile. The power electronics are optimised for the requirement and reduce assembly expenditure. There is an upper mechanical interface to the guide rail and a lower one to the support structure. Straight segments and curves can be combined however suits the application. Because the motor module is without edges and openings, it also allows easy cleaning.

The motor contains the electromagnetic coils and all other active functions necessary for the operation of the system. Only a power supply and an EtherCAT connection are required. A control cabinet is no longer required. The motor module contains no moving parts and is therefore not subject to any wear. The coil arrangement and the mechanical configuration are ready for use.

Integration of displacement measurement eliminates the need for additional installation and the calibration, while tolerances are compensated automatically.

XTS uses a double air gap linear motor, with magnets positioned above a coil package on opposite sides. The high attraction forces of the magnets cancel each other out, which means that only low resultant forces act on the mechanical bearings.

The guide rail with the matching movers makes the XTS system a ready-to-use solution. However, the motor modules can also be used together with the magnetic plate sets as a custom solution without the XTS guide rail. The movers can be removed or inserted without tools through a lock by releasing two screws and removing part of the rail.

The rail system can be extended with straight and curved sections as required. The desired geometries, lengths and radii are formed by the number and choice of the components. In combination with the contact surface of the mover rollers, the system results in good running characteristics and low wear.

The guide rail system is optimised for instant installation on the motor module and minimum manufacturing tolerance and pre-stressed rollers ensure zero backlash. The guide rails have no joints and are available in lengths of up to 6 m. Fittings ensure high-precision mounting.

Movers and guide rail are optimally matched to each other. The geometry of the rail and the hard anodised aluminium of the surface allow good running characteristics and low wear. Lubrication of the system is therefore not necessary.

In terms of applications, XTS can obviously be used in a variety of sectors where there is a need for high-speed handling. However, according to Bradley McEwan, market response has been positive. He says: "The UK is an early adopter and we have already sold a couple of systems", although the company is not yet able to disclose who these customers are.

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Beckhoff Automation Ltd

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