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Cobotic Thread Inspection Generates Aero Engine Digital Twin

Lufthansa Technik has automated the inspection of threaded inserts during the repair process of V2500 aero engine casings. The system was developed in partnership with Lufthansa Technik by The collaborative robot system detects different thread inserts on complex components with the help of a 3D.SurfEyes Midi sensor. The result of the collaboration was a significant increase in the efficiency of the inspection process from 3 hours for the manual process to just 4-5 minutes.

More Precise Inspection Due to Highly Accurate Sensor Technology

If a threaded insert is present and free, the Collaborative Robot (Cobot) checks the thread to the specified tightening torque. The shop floor workers only have to set up the Cobot and turn the component once during the inspection process. The Cobot system provides standardized damage documentation that is evaluated in engineering and used as the basis for any subsequent casing repair steps.

For the thread inspection on an outer V2500 rear case, including the subsequent marking of the detected defects, the previous manual inspection took around three hours to perform, repeating the inspection activity in a highly concentrated manner, and inspecting a total of 230 threads. The manual activity involved the risk that inspectors focus and accuracy were simply not consistent over the complete inspection process. In addition if the inspector was distracted by a colleagues, it could happen that a thread is missed or unnecessarily inspected several times making it more difficult to ensure consistent quality of thread inspection with uniform and high-quality documentation.

Manual Process Tedious and Error Prone

With robotic thread inspection, the work requirements by the mechanic is reduced to comparatively short set-up times taking around four to five minutes thus allowing the inspector to utilize their time for activities with higher added value such as component diagnosis, exploiting their enormous expertise, with clearly positive effects on value creation and efficiency.

The use of the robot improves quality even further as on the one hand, it inspects every tapped hole with consistent precision, which has led to a significant positive development in both quality and throughput times compared with the previously manual process. Secondly, the robot can immediately convert the data collected during the inspection into a ‘digital twin’ of the inspected component, creating a basis for further forward-looking maintenance measures.

Mobile Robotic Inspection System Coexists With Humans

The design of the system in which man and machine ‘coexist’ also enabled the system to be designed as a mobile system. The compact robot and table unit can be rolled to any desired location in the workshop providing great flexibility. The cobot is permanently connected to the rotary table upon which the casing to be inspected is placed and rotated 360 degrees around the central axis.

Despite the safety regulation associated with cobots, suitable additional safety measures were implemented for completely safe operation of the inspection system in the workshop which included robot, rotary table and screwdriving tool. To mitigate the potential risk of personal ‘bumping’ into the robot its traversing speed was reduced to a maximum of 250 mm/second. The lower speed also prevents jamming in the rotating component, as the rotary table moves at less than one revolution per minute. In addition, the rotary table is driven without a brake, thus in the event of an emergency shutdown human operators can easily manually reverse the table to prevent further damage. For the test tool, the maximum permissible pressure was limited to 110 Newtons per square centimeter, which is monitored by appropriate force sensors. In addition, the screwdriving tool was provided with a special protective cover.

Integrated Vision System

The cobot provides a high degree of flexibility and adaptability with its built-in vision system providing the advantage that it can react very well to changing component conditions.

The development cooperation with, experts in innovative automation and digitalization of complex production and maintenance processes was very positive. Since the cobot is comparatively inexpensive to procure and intuitive to program, the CoBot2DAT project was economically convincing allowing the thread inspection system to be transferred to series use in the Lufthansa Technik Hamburg engine workshops.

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