March 2019

| INTERVIEWS & REPORTS | www.smartmachinesandfactories.com March 2019 | 47 | approaches to their design and capabilities and some are tailored to specific types of application. What most of these systems have in common is that their carriages run along tracks on rollers, usually propelled by some form of linear motor. But at the recent SPS IPC Drives automation exhibition in Germany, two new ideas emerged – both of which rely on carriers that “float” electromagnetically rather than running along fixed tracks. The two systems were being demonstrated on neighbouring stands by Beckhoff and Bosch Rexroth. Superficially, at least, the systems have much in common. They are designed to offer a lot more flexibility in movement than fixed-rail systems. So, for example, they can be programmed to move anywhere in a two-dimensional (X-Y) planar area. Some movement is also possible in the vertical (Z) direction, with the carriers being able to move a few millimetres up and down. They can also rotate, which could be a useful capability for presenting items to production processes at precise angles. And, finally, they can even be tilted slightly – a facility that could be used, for example, to prevent liquids from spilling when they are being transported at high speeds in open containers. The two systems operate on slightly different principles, although their developers are not revealing the full details at this stage. In both cases, the carriers float above an array of “tiles” containing some of the technology that enables them to levitate. Announcing Beckhoff’s technology – called XPlanar – managing director Hans Beckhoff hailed it as a “motion revolution” and compared it to a “magic carpet”. The carriers, known as “movers”, float above square tiles measuring 240 x 240mm, and can travel at speeds of up to 4m/s. They can accelerate at rates of up to 2 g and are claimed to be able to position the items they are carrying with a repeatability of 50µm. At the SPS show, Beckhoff demonstrated four sizes of mover, ranging from a 95 x 95mm version that can carry loads of up to 0.4kg, to a 275 x 275mm version that can handle up to 6kg. The movers can be linked together to transport heavier loads. They can even travel vertically up and down walls or be hung upside- down from ceilings. The movers are passive, containing no electronics or mechanics. Beckhoff’s movers can “fly” at height of 1–5mm above the tiles, can tilt by up to five degrees, and can rotate by up to 15 degrees (or 360 degrees if they are above a special type of tile). They can move freely and individually, allowing production line flows to be divided or logjams to be avoided. The contact-free technology avoids wear and contamination by friction particles. In a standby mode, each tile draws around 13W. During operation, the power requirement varies depending on factors such as the load on a mover, whether it is moving and its height above the tiles. For example, a mover “flying” 2mm above the tiles without a load would draw 115W. The sealed, watertight and chemical-resistant movers contain permanent magnets and are propelled by 3D travelling magnetic fields that are generated in the tiles which house flat coils as well as the electronics needed to detect and control the movers. The tiles are linked to a PC- based controller running Beckhoff’s TwinCat software via a 1Gbit/s version The XPlanar system offers a choice of six movers with different load-handling capacities