Automation is everywhere. Digitalisation can control everything. AI is taking over the tasks that clever human beings used to do. The driverless car is with us, and the workerless factory cannot be far behind. But what of the cranes in those factories?
Cranes, of course, have been automated to one degree or another for many years. Process cranes, foundry cranes, and waste-to-energy cranes come with automation as standard these days. The staff who control them can sit in a comfortable and clean office, some distance from the action, monitoring the crane’s performance on multiple screens and intervening only when some change of output is desired. Such cranes do tend to be at the heavier, high-capacity – and high investment – end of lifting machinery: they are big and expensive bits of kit where the capital expenditure of installing perhaps complex automation can easily be justified.
What, though, of the other end of the lifting market? Is it not time that light cranes too – the ubiquitous overhead monorail – become automated as well?
Monorails and their offspring – the light overhead bridge crane made up of monorail sections and profiles, which can integrate smoothly with standard monorails – are abundant in manufacturing plants, large and small, all over the world.
Since automation is now becoming almost ridiculously inexpensive, components are available almost off the shelf, and smartphones and tablets that can control the ensuing systems are owned by almost everyone. Should it not now be applied to the monorail?
It would seem so. The global overhead monorail crane system market is valued at approximately $1.2bn in 2025 and is projected to experience robust growth. Automation and efficiency improvements – in logistics as well as in manufacturing – are reported to be primary drivers; businesses, as ever, seek to optimise material handling processes and reduce labour costs.
Even unautomated, the monorail more than repays its installation. It transports parts between workstations with minimal use of floor space; it gives continuous movement of parts, reducing bottlenecks in automated lines; it can feed parts into robotic cells or CNC machines; and its ergonomics can save human operators from the strains of manual lifting that can lead to back pains or worse.
We can split overhead monorails into those that have a hoist mounted on the trolley and those where the trolley supports a fixed length chain. The latter, of course, move the loads horizontally around the factory, but do not lift it up and down, and are often distinguished as ‘conveyors’. Both have their uses and, on both, the trolley can be motorised or manually operated. In the latter, the operator takes hold of the load or the empty hook, walks along with it to the desired location and the trolley follows him.
Is this really necessary?
So, why automate it? “There is a kind of misconception that automation is going to kill everything that is manual. But the two can work hand-in-hand, and that can give more efficiency than trying to automate every element when not necessarily every element of the process needs to be automated,” explains Dan Upton, who is managing director of Niko UK alongside his brother Sam Upton; the company is a subsidiary of leading European manufacturers Helm Hellas.
The Niko range includes overhead monorails and light bridge cranes, with a speciality in low headroom lifting. The case put forward by the brothers is that there are many places where light overhead monorails could and should be automated – and that there are many places where perhaps they should not.
“Very briefly, if you’ve got, say, a conveyor belt system or a robotic system that’s continuously moving, then trying to unload that or load it with a powered crane isn’t very safe unless you can actually stop the conveyor. That’s because you either have to get the crane moving at the same speed as the conveyor, or else you have to stop the conveyor then start it again – and a continuously repeated stop-start is not efficient. Add to that you will want to keep the lifting chain vertical, for safety: you don’t want it to drag either behind the trolley or ahead of it as it lifts the load from the conveyor.” If you do, you will get potentially dangerous swaying. Achieving the required automated speed synchronisation or a repeated stop-start is quite complex.
“Whereas if you have a manual solution, with the overhead crane unpowered and able to roll freely, then as the operator moves the hook and connects it to the load, the freewheeling trolley always follows the hook and stays almost directly over it. It is an easy thing for the operator to do if the conveyor is not moving too fast, and the chain is never at an angle. So stop-start and sway are issues that have been avoided,” explains Dan Upton.
There is a place for automated light cranes, he continues, with an option to go semiautomatic by automating sections of the route – such as taking the load to a specific section where you can stop it for a set amount of time or move it at a constant speed before going manually through buffering zones, storage areas and loading zones, for example, for complete flexibility in moving a product. Dan Upton dubs this the “best of both worlds”.
“And all of this is reasonably affordable nowadays. If you already have a reasonably modern motorised system that is pendant or radio-controlled, the drive motors will be variable frequency drive inverters; you can very easily and economically convert that to fully automatic. The complexity comes in the control panel or PLC, which with a few sensors is all you have to add, and you can make that as complicated or as simple as it needs to be for the operation you have in mind. All you really have to do is plug in the software.”
Keeping things efficient
A lot depends on the application, explains Dan Upton. “If somebody wants something automated, there is generally a reason for it: either they have to lift the load over something – a walkway or another conveyor, perhaps – or it is something generally quite big that they are moving. And people think, ‘Oh, it is motorised, it is automated, it is going to be quicker.’ But, most of the time, there is a grey area where manual cranes will be as fast as the automated system.” This is true especially for lighter loads, says Dan Upton, as generally there is a 1% force-to-load ratio for these systems when pushing a trolley. Pushing with a hundredth of the weight of the load means that anything up to 2t can be moved manually by the operator with ease. “Often, you are using electronic automated systems for safety as much as anything else. You don’t want to get too close to a large load, and you don’t want to accompany a load into a hazardous area.
“More often than not, customers come to us with automation projects wanting the full-singing, full-dancing solution and it ends up somewhere in between, with elements of fully powered and automated and elements of manual. It is all about working out what is most efficient.”
Sam Upton concurs. “From my point of view, I always try to tell customers to forget about the cranes, forget about whether the load is above you or on the ground or halfway between – instead, think about the ideal flow.
“Look at the movement from A to B to C to D and E via whatever workflow processes you have to do. What is the most efficient way to move that product around your factory? And then it is a case of, ‘Okay, so we know where the product has got to move to. How do we use the technology to get it there? Which bits of the journey need to be automated? Which bits are going to be better handled manually? Where do we have a crossover between the two? How do we most efficiently manage that?’,” he explains.
“One element of that is precision. Where in the process is precision most needed? Where is it less important? That again comes down to speed and to the actual process in the industry. If you are placing microchips onto a board it needs millimetre precision so it has to be camera controlled. Other processes don’t need to be like that. So you tailor the system to suit the stage of the process. If you automate, the precision is as good as the sensors and the software that you have. If you go manual, it is as good as the human eye and arm and hand.” For many applications, this is a complex, efficient and well-designed tool.
Sharing the load
There is a parallel here with the material you use for your overhead tracks and runway. Steel has been the traditional medium. Aluminium has recently gained traction for its lighter weight. “There are some interesting points here,” says Sam Upton. “In the market, aluminium is seen as modern, and there is a perception that aluminium is always lighter as a material. Yes, it certainly has lower density. A piece of steel will be heavier than a piece of aluminium of the same size. But, size-for-size, steel is stronger. You will find in a lot of instances that to get the same level of strength in aluminium you have to have a lot more of it, so the weight saving might not be significant at all.
“Often you get situations, more so on when you are dealing with loads at the upper end of the light crane spectrum, in which the moving parts of your crane, which on a bridge system will be the bridge itself, would be a similar weight in steel as aluminium.”
And, of course, as far as energy consumption is concerned, it is the weight of the moving parts that matter. The weight of the static parts – the main runways – is irrelevant. “If you were pushing a bridge around with a load of 250kg on it, most of the weight you are moving is actually the bridge. Even so, if the steel bridge weighs 200kg and the aluminium one weighs 180kg, and your pushing force is 1% in both cases, the saving in pushing force is next to nothing. So above a certain capacity there is no advantage in aluminium. But at the lighter capacity end of the market, it certainly has a place when you’re moving loads up to around 250kg.
“I do question, though, why anyone would ever motorise an aluminium system, because 90% of the advantage of an aluminium system has got to do with weight. And given the very low friction trollies that are around nowadays the capacities you would carry on it can be moved along almost with a finger. So why would you fit a motor? It is extra expense for no real reason, unless there’s an environmental reason for it – if you wanted it for, say, a clean room or an explosive atmosphere where operators should not go. If you want a motorised system, my advice would be to do it with steel and save the cost of expensive aluminium. You get exactly the same solution but much more cost effectively.”
A big advantage of an overhead monorail, he expands on the point, is that it moves with such low friction. “They have smart track profiles and wheels that that run and move very, very freely. The trolley is free to move and it is easy to move manually.” Not to mention moving things manually has other advantages. One of which is that if the operator works on the load in two different locations with two different machines – say to mill it then to drill into it – and walks between the machines pulling the load, then the load keeps pace with him exactly. “If you like, when you motorise something, you are losing the manual performance and convenience.”
The alternatives, then, depend on the application. All-singing, all-dancing automation is easy and economical to install and sound modern and state-of-the-art and attractive. It is there, and available, if you want it. But human operators, with human brains, work capably and efficiently too. You can pay or save your money, the choice is yours.
