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World of Industries 3/2020

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World of Industries 3/2020

An extraordinary

An extraordinary movement artist in aircraft construction AUTIOMATION Industrial robots rotate a thousand times over several axes whilst riveting aircraft fuselages. A stress test for data, pneumatic and energy cables. To endure the movements, a Spanish plant manufacturer, relies on cable guides made of high-performance plastic. Passengers think of a lot of things on the flight to their summer holiday. Of relaxation, the beach and a cocktail. But very few think of rivets, of the inconspicuous fasteners that safely hold the fuselage parts of the aircraft together. In a task that takes weeks, skilled workers beat the rivets into metal fuselages that weigh several tons. Wasn’t automation of this laborious activity possible? Desirable, yes but it had been impossible for a long time, because robots were not sophisticated enough. They needed more than just flexibility to reach every point of a fuselage. They also had to master several work steps – from drilling and milling to riveting. With a precision of 0.2 millimetres. Author: Jörg Ottersbach, Business Unit Manager e-chains, igus GmbH, Cologne, Germany Fuselages are riveted together by 6-axis robots Loxin 2002 succeeded in automating the riveting process. The multi-axis robots of the Spanish company work in the production division of a large aircraft manufacturer. Left and right next to the raised fuselage. The robots are mounted on platforms that can be raised up to a height of several metres by linear units – similar to a forklift (lead picture). Arriving at the right height, the heavy robot weighing tons, moves to the operating point with millimetre accuracy over six axes. It drills a hole in the metal, mills a recess for the rivet head, vacuums up the dust, applies a sealant and sets the rivet. Depending on the fuselage section, the robots must constantly change the angles and diameters during drilling, milling and riveting. But this flexible multitasking was not the only hurdle that Loxin had to overcome during development. Challenge: cables have to withstand complex movements The engineers had to design the robots to be truly flexible. Six axes are used to move the head to any part of the fuselage. The issue of energy supply is equally complicated. The tools on the robot’s end effector are connected to numerous energy, pneumatic and data cables. And these cables must follow the contorted movements of 16 WORLD OF INDUSTRIES 2020

01 A twisterchain protects the cables from the base of the robot arm to the first axis. The energy chain allows 540 degree movements. 02 Unai Martínez Díez, Senior Sales Engineer at Loxin (left), together with Francisco Martínez, Sales Manager e-chain systems (igus Spain) 01 A twisterchain protects the cables from the base of the robot arm to the first axis. The energy chain allows 540 degree movements the arm perfectly, even at high speed – without rubbing against each other or knocking against the sensitive surface of the fuselage. Otherwise, long downtimes due to cable breaks and damage to the aircraft occur. In search of a reliable energy supply system, Loxin compared systems from several manufacturers. “However, for a long time we could not find a robust and reliable solution,” recalls Unai Martínez, Chief Engineer at Loxin. “The number of cables and the weight was a problem.” Loxin had experimented with corrugated tubes. Due to the rapid wear from friction, they break easily. In everyday life, material failure would have meant replacing the entire tube, including removing the cables on the heads. In the worst case this would have resulted in a shutdown for several days. 3D cable provide maximum degrees of freedom Loxin finally found what it was looking for in Germany. At igus, the motion plastics specialist from Cologne, which has been developing cable guides for decades! The range includes, among others, the triflex series. These are hose-like protective cages made of wearresistant high-performance plastic, which follow even the wildest three-dimensional movements of industrial robots. Inside, the cables for data, pneumatics and energy supply are securely fixed and protected against wear. “The cables are protected against mechanical stress due to tensile load, torsion and expansion. This protection is particularly important when the robot heads take their maximum position,” explains Unai Martínez. To ensure that the triflex energy chains mounted on the right and left of the arm move as close to the arm as possible and do not hit the aircraft, Loxin uses the triflex RSE retraction system. If the robot arm returns to its original position after a movement, the mechanical system retracts the chain – round brackets, which are mounted on the arm, ensure safe guidance. The robot arm has full freedom of movement, without having the parts of the chain rub against each other or form loops. “The igus energy chain also has a much better friction behaviour than the corrugated tube and will therefore not break and cause a stoppage,” says Martínez. And if a chain link reaches the end of its service life, it can be replaced in a few simple steps. By using the triflex chains in conjunction with the triflex RSE retraction system, Loxin has also been able to achieve a better mobility of the robots, which can now simplify their work steps around the fuselage even more easily, which saves valuable assembly time. Energy chain allows circular movements of 540° Another product from Cologne is used on the robot arm: the twisterchain, an energy chain that protects the cables from the base of the robot arm to the first axis. The chain moves in a guide trough. If the robot arm turns, the chain folds as the upper run of the chain rests on the lower run. The chain allows a circular movement of up to 540° at speeds of up to 1 m/s. Since it also consists of high-performance plastics, it is very wear-resistant. Tests in the igus test laboratory have proven that the service life of the energy chain is over one million cycles. “We are very satisfied with the solution, as our plants now have less downtime,” concludes Unai Martínez from Loxin. igus is also pleased with this extraordinary reference. Loxin was presented with the 2018 vector award for the challenging energy supply solution. This award is organised by igus every two years and its winners are chosen by an independent jury. Photos: igus WORLD OF INDUSTRIES 2020 17


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