The rise and rise of linear robots

Linear motion - that is motion along a straight line, which can be described mathematically using only one spatial dimension - is the most basic type of motion. Linear motion systems which utilise this principle are employed extensively throughout industry across a broad range of application areas. These can include basic sliding systems: for example, automatic doors on a train, bus or other vehicle; for adjustable fixtures, furniture and seating, including those in automotive, aerospace or medical applications; or for sliders used in racks, shelves and drawers.

They are also heavily used in the film and theatre industry in dolly systems for stage or set camera, lighting and sound rigs; or in studios, control rooms and vehicle cabins for mounting moveable monitors and panels. In this article, Robert Dumayne, director, igus, discusses how these linear motion systems are also being deployed to help raise productivity and reduce costs in industrial automation.

In more industrial settings, linear motion systems are commonly used for automating elements of manufacturing, test and measurement, materials handling, filling and packaging, and logistics. High speed, high precision and highly repeatable motion control of machinery is being used across pick and place, inspection, sorting, storage and retrieval, palletising and other production tasks to help prevent workers having to perform mundane, repetitive and monotonous tasks. This helps improve safety and avoid injuries, eliminate bottlenecks, increase quality and consistency, and raise productivity and efficiency – with accelerated cycle times, increased throughput and longer production cycles, even 24/7, becoming feasible.

Known as linear, gantry or Cartesian robots, these industrial systems are mechatronic devices that combine not only the linear motion capabilities, but motors and linear actuators to make rapid and accurate movements in up to three axes, X, Y and Z, usually to position some form of tool and/or to move and deposit a payload. A physical framework – the gantry - supports the axes and payload (and can therefore handle heavier payloads), enabling precisely controlled linear motion along the machine’s axes, even with rapid acceleration and deceleration, and can be mounted horizontally, vertically or even overhead in certain configurations. As well as the manufacturing, packaging and handling applications outlined above, linear robots are also the most common design for 3D printers, which require fast and accurate positioning for their print heads through three axes.

These linear robots offer certain advantages over other common industrial robot types, including pedestal-mounted six-axis articulated robotic arms or SCARA (Selective Compliance Assembly Robot Arm) robots. Typically, they are less expensive, because they can be quickly assembled from standardised, modular components, as well as programmed and controlled more easily. They can often be easily designed and specified using online configurator tools simply by defining requirements and parameters – and can even be reconfigured and upgraded as requirements change. Because they use parallel, not serial kinematics, manufacturers can reduce operational costs, including making savings in energy costs. In parallel kinematic systems, each motor acts directly on the load, and by sharing the load in this way, they can work more efficiently. Parallel kinematic systems deliver higher dynamics, can carry higher payloads, offer reduced cable management and are more compact.

Industrial linear motion systems often feature recirculating ball bearings, but these require very careful installation, set-up and periodic maintenance. Lubrication with oil or grease is essential, which contributes to them not coping well with many manufacturing, production or laboratory environments, where contamination via ingress of dust or dirt is a constant hazard. Plastic linear plain bearings, on the other hand, are dry-running and self-lubricating, therefore run maintenance free. Unlike recirculating ball bearings systems, they operate on glide pads and do not depend on travel length, hence do not impose any conditions on minimum stroke length.

igus offers industry-leading, tribologically optimised materials for virtually every linear application, all of which have been extensively application tested at its 2,750m2 test facility in Cologne, the industry’s largest and most advanced facility for testing motion plastics. Its modular drylin linear technology range spans many different configurations and options for every application, including linear guide bearings and rails, linear bearings and shafts, leadscrew technology, toothed belt and electric-motor driven systems. igus offers complete, flexible and reconfigurable linear robotic systems via its versatile, modular and easy to design and specify drylin linear bearing and drive technologies. Engineers can use igus online tools and configurators to specify their application requirements and to configure combinations of complete linear axes, including motors, drives, initiators, supply cables, limit switches and mounting components. Line, surface or room gantry linear robots deliver scalable, flexible and reliable linear motion through one, two or three axes.