A Glimpse into Aircraft Assembly Lines
The design and the industrialization of aircraft is a complex process. To give an idea the number of parts (excluding standard elements) used in an aircraft like the Airbus A400M exceeds the 500,000. The parts are assembled into aerostructures and major components, which are designed and manufactured in several countries all over the world. In a particular plant, a Final Assembly Line (FAL) is created to join several major aerostructures and components, integrate systems and test the complete aircraft.
The design of the FAL is part of the aircraft industrialization phase and it is shifted from the aircraft functional design. It starts after the aircraft feasibility phase, when a definition of the aircraft basic concept (as specified product structure) is available. The FAL design can be decomposed into three main phases: Concept (create conceptual assembly process), Definition (define assembly process) and Development (develop detailed assembly process).
In many industrial sectors, Assembly Line Balancing (ALB) is a key part of designing an assembly line. In general, ALB comprises ordering of tasks among workstations to satisfy precedence constraints and objective functions. The objective function can be: minimize cycle time, minimize workstations, etc.
An aircraft FAL requires a different approach, due to its specific features. For instance, the number of workstations relates to technological criteria rather than to a calculation that aims to minimize the total number of stations. The cycle time is equal for all the workstations and it is usually a known target, and the number of tasks to be executed in a workstation ranges between 50 and 500. Less than fifty percent of the tasks have precedence constraints, and very few tasks can be automated since most of them are intensive in human resources usage.
The FAL definition is created based on requirements related to delivery plan, budget, technologies, space availability, logistic, etc. A preliminary design solution contains the workstations, their precedence constraints, tasks assigned to stations due to technology, jigs and tools, and industrial means constraints.
The concept of product Digital Mock-Up (DMU) as master is a standard in the aerospace sector and in Airbus in particular. All the information related to the functional aspects of the product is included in the product DMU. The product DMU is the reference for the product functional definition. It is built under concurrent engineering working methods, which comprise the definition of manufacturing constraints.
Currently, working methods at Airbus, based on a Collaborative Engineering approach, promotes the integration of design teams, both functional and industrial, to generate a unique deliverable along the design process, named: industrial Digital Mock-Up (iDMU). The iDMU integrates geometrical and technological information related to: product (What to manufacture?), processes (How to manufacture the product?) and resources (What is needed to execute the processes and manufacture the product?).
Not surprisingly, such a collaborative approach resulted in a new concept: 'iDMU for all.' This is the main enabler of the Collaborative Engineering approach and provides a common virtual environment for all the aircraft development stakeholders. Functional design and industrial design are part of a single design process where they progress together and influence each other.
The iDMU collects the information related to functional design together with all the information related to industrial design: manufacturing and assembly process, associated resources, industrial means and human resources. All is defined in an integrated digital environment, where complete and partial simulations are done continuously, and at the end of the design phase, they guarantee a validated solution to manufacture the aircraft.
A Product Lifecycle Management (PLM) system creates, manage and support the iDMU., since collaborative working methods require the intensive use of PLM tools to perform virtual manufacturing and support the iDMU as kernel. The iDMU is the key element of the Collaborative Engineering approach to tear down the wall between functional design and industrial design. The aim is to pursue a collaborative design process with a single team that creates a single deliverable: the iDMU. By applying virtual validation, using virtual manufacturing techniques, a further reduction of time-to-market is also feasible.
Since the iDMU comprises the full definition of the manufacturing activities, the downward link with the physical manufacturing is created by feeding the generated work instructions (WIs) to the shop floor.
During the conceptual design phase of an aeronautical FAL, requirements are under definition. For instance: work share, work load distribution, factory locations, production processes and technologies, logistic system, main machinery and tooling. During the conceptual phase, designers require defining FAL alternatives with different values for a set of input requirements.
Such set of values for the input requirements defines a scenario and allows executing ‘what-if’ analyses. A Project Management Office is responsible to define the scenarios. Both the scenario and the FAL design alternatives are part of the iDMU. Different product structures are collaboratively created along the design process: “as designed” (functional view), “as planned” (industrial workload view) and “as prepared” (process oriented view).
At the conceptual phase, the process of generating industrialization solutions depends heavily on the personnel experience and is time-consuming. Consequently, manufacturing engineers can only check a simplified set of cases to generate and submit early manufacturing processes and resource requirements. In order to enhance such process, it was decided to launch a project, named CALIPSOneo, to investigate how to assist designers to generate FAL alternatives at the conceptual stage and how to enhance the current PLM tools to support the implementation of the ‘iDMU for all’ concept. The project had to be carried out within the framework of a commercial PLM/CAX system used in the aircraft programs (Catia/Delmia v5 from Dassault Systèmes).
CALIPSOneo is one year lasting project that was launched early in 2013 to support the development, customization and deployment of the PLM tools and processes in Airbus Military. It is a research and development joined effort that involves Engineering Companies (Glenser), IT companies (T-Systems), PLM Vendors (Dassault Systèmes), Research Centers and Universities (FIDETIA, CEIT and Polytechnic University of Madrid).
CALIPSOneo aims implementing new working methods and processes needed to support a collaborative functional and industrial aircraft design. It takes as input developments from previous projects, related to digital manufacturing techniques implementation and aircraft conceptual design modeling. The main project objectives can be summarized as follows:
Test Collaborative Engineering concepts applied to aircraft design and manufacture.
Evaluate the current status of the PLM system to support the iDMU concept, develop and deploy new capabilities to facilitate the collaborative work and the iDMU creation.
Define working procedures to create the iDMU.
Evaluate the capability to generate an iDMU and to use it for a virtual manufacturing validation.
Assess the benefits of the iDMU concept when compared to the current practices for the industrial design.
Demonstrate how to exploit the iDMU to produce advanced work instructions and shop floor documentation.
Evaluate the deployment of work instructions and shop floor documentation using augmented reality techniques.
Evaluate the product configuration based on individual specimen.
Further information about the project can be requested from the authors:
About the Authors
Mr. Fernando Mas is Industrial Engineer and EADS Senior Expert in Advanced Manufacturing Processes Methods & Tools and Information & Software Technologies. He is in charge of the PLM Processes & Tool Solutions Department of Airbus Military. He participates in the projects EADS RTG (Research and Technology Groups) and EADS TRANSPHER for PLM harmonization.
Dr José Ríos is senior lecturer in the Dept. of Mechanical and Manufacturing Engineering at Polytechnic University of Madrid. He has collaborated, in research projects related to PLM technologies, KBE and collaborative engineering with different companies, e.g.: AIRBUS, GKN Aerospace, T-Systems, SEAT, GAMEGAM and ASCAMM.
Dr Carmelo del Valle is senior lecturer in the Dept. of Computer Languages and Systems at University of Seville, and researcher at FIDETIA. He has collaborated in research projects related to PLM, Planning & Scheduling, Diagnosis and Business Process Management with different companies, e.g.: AIRBUS, CAMPSA, IZAR Astilleros Sevilla and Skill Consejeros.