Today, manufacturing is hardly conceivable without industrial robots and their areas of use are increasing continuously. But due to the permanent three-dimensional movements in the automated factory, the cables that supply the robot are subjected to extreme levels of stress. A special challenge for manufacturers of cables and connecting components. Article by Reiner Rössel – Head of Business Unit ECS Chainflex Cables.
The International Federation of Robotics (IFR) predicts that by 2020 more than 1.7 million industrial robots will be working in factories worldwide. That is a huge worldwide market for robot manufacturers. To ensure that robots are supplied with data and energy without any interruption, it is worth taking a look at the cables that have to “go along with” the 3D movement of robots, which are on the move continuously.
Robot cables for applications where the cables are subjected to torsional stress have to be constructed and manufactured in a completely different way to cables for linear motion. They must be as compact and as closely braided as possible and have an outer jacket extruded at high pressure. The reason that this is important is because this special “hardness” enables the cable to follow the motion pattern of the energy chain.
Robot cables, in contrast, need force-compensating elements, loose braiding elements, different slip planes and completely different shield concepts in order to ensure they continue to function correctly even after several million movements involving torsional stress. This is because the cables used in robot technology have to repeatedly change the directions in which they move. For example, the diameter of the braid structure can actually change with torsion angle.
Cable specialist igus incorporates damping elements and torsional-force absorbing felt into the core groups, which are specially designed for use in applications involving continuous changes in torsional stress, in order to offset the forces acting on the cores. The requirements for the shielded cable types are especially high. In order to ensure that the forces acting on the shield wires are not too large, the motion plastics specialist places gliding elements above and below the shields. These elements ensure that the shield can move freely in relation to the overall braiding as well as the outer jacket.
The shield structure is designed for force redistribution and has damping elements in the direction of that force redistribution. This “soft” mode of construction gives the entire cable the necessary freedom of movement, reduces tensile and compressive forces, and preventing shutdown of a machine due to a premature conductor breakage.
Optimum Protection For Robot Cables
On the basis of know-how gained over more than 50-years of experience in this area, the jacket materials have been optimally matched to the plastic of the triflex R robot energy chain, reducing abrasion and wear to a minimum. The triflex R TRCF is a closed energy tube based on the three-chamber principle: all three chambers of the TRCF can be opened and closed independently of each other.
The supply hose is placed in one of the three chambers of the energy tube and is therefore protected against deformation. This makes the energy supply process reliable whatever the axial position of the robot is. The main feature that ensures reliable and operationally safe guidance of robot cables and hoses is compliance with the minimum bending radii. If the latter are not adhered to, there is a risk of cost-intensive plant failures.
The technical design of the igus triflex R ensures that the prescribed minimum bending radius is adhered to whatever may be the working position of the robot – a circumferential outer stop prevents bending below the minimum bending radius. Moreover, the modular design of the igus triflex R ensures that a torsion angle of approx. +-10° per chain link is not exceeded. This has the advantage that the torsional stress on the cables is distributed along their whole length and not only at one end, which is the case with other systems.
The defined minimum bending radius of the triflex R robot energy supply system guarantees process reliability especially in robot applications with supply hoses as well as in the case of flow punch bolting. This is because a kink in the supply hose interrupts the power supplied to the screws on the tool and the process is disrupted.
Tests Offer Plannable Reliability And Reduce Costs
igus has been setting new standards with its range of “chainflex” moving cables in the areas of automation and robot technology. It is a company for special cables, available from stock, for continuous motion in applications involving energy chains and torsional stress. In a 3,800 square metres test laboratory, igus twists the chainflex CFROBOT cables millions of times while continuously measuring core resistance in different test set-ups. The undoubtedly greatest challenge in the tests is that it is difficult to reproduce every conceivable application that involves torsion over the service life of the product.
Whereas the service life limits can be dependably predicted in the case of linear travel in energy chains due to fixed parameters and known ambient-influences, robot applications are usually much more complex. In particular, the sequence of movements per se is often not completely clear during the planning phase. For the cable supplier, it is therefore of prime importance to test, test and test again. All the results of the tests are recorded in a database.
The mechanical engineering processes can be precisely planned. If a CFROBOT cable failed when used for the intended purpose, igus would supply a new cable. The great advantage of the CFROBOT series for robot manufacturers and users is that they do not have to depend on expensive, special cables with long delivery times but can simply select from a standard range of products which has been specially developed for torsion applications and includes over 100 types of robot cables all available from stock.
Predictive Maintenance: Industry 4.0 Gets Trouble-Free Motion
The “smart plastics” provide a glimpse into the near future of robotic cables. Under the name isense, igus carries sensors of various kinds that detect the condition of components such as cables or energy chains. They measure among other things the wear during the operation and alert the user early enough to plan repair or replacement.
By networking with the icom communication module, the data is transmitted to an intelligent system. The module can be connected to all specific sensors. Once the measured values from a sensor have been transferred to the icom module, they have to be “interpreted”, ie: understood in order to generate instructions from the same. So far, this has been possible via the connection to the igus cloud. Due to the increasing importance of IT security, however, many companies are increasingly relying on the development of their own SCADA systems, which is why igus has now advanced its data concentrator into icom.plus.
With the new module, the customer can integrate the data in the way that best suits their equipment. With the online connection of the icom.plus, a continuous matching of the service life statement with the cloud takes place in order to enable maximum system runtimes with minimal failure risk. The data in the cloud draws on the 10 billion test cycles of energy chains and cables performed in the company’s own 3,800sqm test laboratory, and thanks to machine learning and AI, igus can provide precise information on the durability of the solutions used and inform the user about a necessary replacement beforehand.
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