TECHNOLOGY REPORT | DIGITILISATION
DEMAG SMART-TANDEM CONTROLS FOUR AT ONCE
For large or heavy components, indoor cranes frequently operate in tandem. This calls for great skill on the part of the crane operators and for near-perfect coordination between them, to keep the load level and safe. Alternatively, two Demag universal cranes with the smart-tandem control system can be operated by a single controller with a single remote control. Demag’s SafeControl unit, developed in- house, monitors and controls all the relevant motions of the cranes assigned to it, and can perform additional tasks as well. This feature allows a single control unit to control all the motions of two cranes and up to four trolleys. It is easy to link the operating functions via a common radio control system. The cranes can be used independently, or in synch with each other. In ‘normal mode’, each crane can be used as an individual unit, independent of the other and each with its own operator and radio control unit. If both cranes need to work in tandem, one operator can take control of both cranes, from one of the radio controllers, and with them can control up to four trolleys. As options, he can operate each of the two cranes separately (A or B) or both cranes synchronously in parallel (A and
automate first. That sets them up for failure. If you chose something simple – such as the conveyor unloading - that is going to give you a quick return on investment,” he adds. “But it is all about balancing the need
you have to the budget you have. It is easy to think that just because an automated overhead lifting system costs say, £40,000, that that is an end of it; but there are a lot of additionals that have to go in there as well. Beside all the legislation that you have to comply with there are all the control systems, how you link into them and how much information you want out of those control systems. Do you want continuous real-time feedback of usage and power use and maintenance schedules? It can escalate very quickly. You have got to program it, which is not that simple, and you’ll need software updates every couple of years; but once you have made that initial investment the gantries themselves – the steel overhead track and the trolley and motors - will last quite frequently in excess of 20 years. That’s a problem that Güdel as a company has with our gantries: the things never wear out.”
R Demag: Smart-Tandem SafeControl.
B). Switchover between these modes is by a selector switch on the radio controller. Since the safety control system can also detect and evaluate the simultaneous motions of two
One of the revolutions that has made
all this possible is sensors. A hook, or a vacuum lifter, or a servo-operated grab - has to meet the load, so it has to know where it is. “Our trolleys and hooks can repeat to an accuracy of about 20 microns. Typically, they will go to that position every time and pick up a load – as long as that is exactly where the load is each time. You can put vision systems onto the hook, and then the load can be a little bit off its zero position. The camera can give the coordinate shift to the gantry, or to the robot arm if that is what you are using and guide it to the load from there.” Picking up components that are
randomly piled in a crate is harder, he says. “It is not impossible but it is definitely challenging. For that, light is king. You need sufficient lighting for the camera system, and enough contrast between the items you are trying to pick up. If you have a containerful of brown cardboard boxes, from the camera’s perspective it just looks like a sea of brown. But stick a logo on each box, and the camera can focus on that. Or you can paint your boxes different colours, though
cranes, all the safety requirements for crane operation - Performance Level c or d and Category 2 to EN ISO 13849 are the relevant
using colour cameras is a little more expensive than monochrome. Another technique is to use barcodes. The camera can find the barcode to locate the box, and that tells it as well what is inside, and so where it should be carried to. That is used a lot in the food industry where you have one large gantry that is sorting say 15 different products at the same time. You may not have enough throughput to justify a dozen industrial robots, one for each product, but you can have one gantry that does different things to different products. It is about choosing the right automation for the right application.” Industry 4.0 is a goal but it is not needed for all and we are not there yet. For a self-contained system, but one that still uses digital interactions to achieve synchronous control of two different cranes, Demag has its SafeControl system, designed for handling joint lifts (see above). For what is currently achievable in a large system that is integrated with its plant, consider Street Crane Express Special Projects aluminium rolling mill in Oman (see p36) And for progress towards the goal, Dieter Feldhinkel, technical
www.hoistmagazine.com | August 2021 | 33
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