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Complex robotics in aircraft construction
22 January 2021
Industrial robots rotate a thousand times over several axes whilst riveting aircraft fuselage. To endure the movements, manufacturer LOXIN (ARITEX GROUP), relies on cable guides made of high-performance plastic – developed by the motion plastics specialist, igus.
Inconspicuous fasteners that safely hold the fuselage parts of the aircraft together are vital. In a task that takes weeks, skilled workers beat rivets into metal fuselages that weigh several tons. But why has this process not been automated? Because robots were not sophisticated enough. They needed more than just flexibility and they also had to master several work steps - from drilling and milling to riveting. They also needed it to have a precision of 0.2 millimetres.
Fuselage are riveted together by 6-axis robots from LOXIN
LOXIN succeeded in automating the riveting process. The multi-axis robots of the Spanish company work in the production division of a large aircraft manufacturer. The robots are mounted on platforms both sides of the fuselage. These can be raised up several metres high by linear units. Once at the required height, the robot, which weighs several 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.
Challenge: cables have to withstand the complex movements
The engineers had to design the robots to be truly flexible. Six axes are used to move the head to reach all parts of the fuselage. The issue of energy supply was equally complicated. The tools on the robot's end effector are connected to numerous cables, energy, pneumatic and data. These cables must follow the contorted movements of the arm perfectly and at high speeds.
Solution: 3D cable guides from Cologne ensure freedom of movement
LOXIN finally found what it was looking for in Germany. Igus has been developing cable guides for decades! The range includes, among others, the triflex series. These are hose-like protective cages made of wear-resistant 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.
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.
The robot arm has full freedom of movement, without having the parts of the chain rub against each other or form loops. 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.
Energy chain allows circular movements of 540°
Another product used on the robot arm: the twisterchain, an igus 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 1m/s.
"We are very satisfied with the solution, as our plants now have less downtime," concludes Unai Martínez from LOXIN
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