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Scenario for concurrent conceptual assembly line design: A case studyF. Mas, J. Ríos, and J. L. Menéndez Citation: AIP Conf. Proc. 1431, 625 (2012); doi: 10.1063/1.4707617 View online: http://dx.doi.org/10.1063/1.4707617 View Table of Contents: http://proceedings.aip.org/dbt/dbt.jsp?KEY=APCPCS&Volume=1431&Issue=1 Published by the American Institute of Physics. Additional information on AIP Conf. Proc.Journal Homepage: http://proceedings.aip.org/ Journal Information: http://proceedings.aip.org/about/about_the_proceedings Top downloads: http://proceedings.aip.org/dbt/most_downloaded.jsp?KEY=APCPCS Information for Authors: http://proceedings.aip.org/authors/information_for_authors
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Scenario for Concurrent Conceptual Assembly Line Design: A Case Study
F. Mas(1), J. Ríos(2), J.L. Menéndez(1)
(1) AIRBUS Military, Avda. García Morato, s/n. 41011, Sevilla, Spain, [email protected]
(2) Universidad Politécnica de Madrid, José Gutiérrez Abascal, 2. 28006 Madrid, Spain, [email protected]
Abstract. The decision to design and build a new aircraft is preceded by years of research and study. Different disciplines work together throughout the lifecycle to ensure not only a complete functional definition of the product, but also a complete industrialization, a marketing plan, a maintenance plan, etc. This case study focuses on the conceptual design phase. During this phase, the design solutions that will meet the functional and industrial requirements are defined, i.e.: the basic requirements of industrialization. During this phase, several alternatives are studied, and the most attractive in terms of performance and cost requirements is selected. As a result of the study of these alternatives, it is possible to define an early conceptual design of the assembly line and its basic parameters. The plant needs, long cycle jigs & tools or industrial means and human resources with the necessary skills can be determined in advance.
Keywords: Assembly line design process, assembly line design scenario, concurrent assembly line conceptual definition, case study.PACS: 89.20.Bb, 89.20.Ff, 89.20.Kk.
INTRODUCTION
Predictive scenarios are a decision support technique used to plan and make decisions for future designs 0. When addressing the design of aerospace assembly lines, the design process is characterized by a collaborative way of work, where several industrial partners are involved, and personnel knowledge and competencies are its main support. The need to develop formal models of manufacturing systems for evaluation and decision making rather than relying on experience and rules of thumb is widely acknowledge 00. Due to the relevance of the aeronautical assembly processes, the interest in capturing its associated rationale and creating models to help in the assembly line design process is the research focus of some authors 0 0.
At the conceptual phase in the lifecycle, input requirements are still under definition: work share and work load distribution, technologies to be used in the product and in the process, main machinery and tooling [6]. This leads to situations where the designers wonder what will be the impact if a particular requirement changes, or where the designers would like to know possible design alternatives based on different values for the input requirements. A ‘what-if’ analysis is a predictive scenario technique to respond to such questions 0.
The 4th Manufacturing Engineering Society International Conference (MESIC 2011)AIP Conf. Proc. 1431, 625-632 (2012); doi: 10.1063/1.4707617
© 2012 American Institute of Physics 978-0-7354-1017-6/$30.00
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In this paper, a pilot case study is presented to illustrate a ‘what-if’ scenario defined for the conceptual design of aeronautical assembly lines. It represents the first results of a research aiming to define a ‘what-if’ scenario to assist during the Industrialization Conceptual Phase. The case study is based on the FAL (Final Assembly Line) of the AIRBUS A400M aircraft, and particularly in the Station 60 0. One of the main tasks done in the Station 60 is the Fuselage join-up and one of the most important decisions during the conceptual phase was to decide between an automatic assembly process and a manual one. A scenario defined by parameters and some associated rules are presented to illustrate how the ‘what-if’ technique would be applied and how the decision process is.
METHODOLOGICAL APPROACH
An assembly line is a complex industrial installation that involves complex assembly processes, sophisticated jigs & tools, machines and industrial means and skilled human resources. The decisions taken in the first step of the product lifecycle, the conceptual phase, are decisive in its final conception and industrialization and then have a strong influence on the assembly line. As the product starts to be designed, the ability to evaluate many alternatives based on many scenarios and therefore to have an early industrialization of the assembly line is considered a valuable tool.
Traditionally the industrialization at the conceptual phase, have not been supported by predictive technologies to the same degree as other aspects of aircraft development. Up to 80% of the final aircraft cost is determined during the conceptual phase alone, and for conventional aircraft structures built up from parts, up to 30% of the final cost is incurred during assembly operations 0. The lack of tools to help developers to evaluate scenarios in a practical way means that engineers do a large amount of work using CAD and office tools (spreadsheets, tables, standards, PERT charts, etc.) to evaluate a reduced set of scenarios to release cost estimations, an early processes and resources requirements.
FIGURE 1. Scenario Definition and Concurrent Loop
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Figure 1 shows the scenario definition and the concurrent loop between the different actors: Program Management Office, Design Engineering and Manufacturing Engineering. Based on the scenarios, all the industrial view requirements are included in the product definition. The processes and resources needs are predefined and launch to the different providers early in the lifecycle avoiding future delays. Also the concurrent loop with the providers can start early. At the end of the development phase, the final version of the assembly line plus the definition of its resources is ready to be used in the next phase.
Conceptual modeling is the basic element in the development process. It started with the definition of an Assembly Line Design Process Model where requirements involved in such design process were identified 0. The next step was to create an information model to support such process 0. The case study presented in this paper shows the rationale behind the defined scenario and the model to support it.
The definition of scenarios requires also a formal process that comprises several steps: define scope, define stakeholders, identify technological and management trends, identify key uncertainties, create initial scenario theme, check scenario consistency, wrap-up on the scenario checking and identification of research needs, and develop quantitative models. Traditionally and due to its origins, scenario planning was considered a tool used for strategic planning 0. Time frame and overall impact are the main attributes to distinguish between: strategic, tactical and operational. Currently, the concept of scenario has a wider scope ranging from the strategic to the operational levels. And the three main steps for its development can be summarized into: define the goals of the scenario, define the supporting process where the scenario will be used, define the content of the scenario 0.
The complexity of developing a ‘what-if’ scenario depends greatly on the scope and goals to be addressed. As a first step, it was decided to define a pilot case study. Such case study limits the scope of application but it allows illustrating perfectly the process of how to create a scenario. The Assembly Line Design Process Model 0, the AIRBUS A400M FAL specification 0, and the Information Model supporting such process 0, are the result of prior works used in the development of the ‘what-if’ scenario case study.
CASE STUDY
The case study scope is based on the FAL (Final Assembly Line) of the AIRBUS A400M aircraft, and particularly in the Station 60. The goal is to decide between an automatic assembly process and a manual one. The quantitative model of the case study was created using Excel. The values of the different variables that define the case study are stored in cells and scripts were created to implement rules.
One of the main tasks done in the Station 60 is the Fuselage join-up. The fuselage join-up is the process to assemble two parts of a cylindrical fuselage, in the case study the rear fuselage and the nose fuselage (Figure 2). The assembly process includes an exact positioning of both parts and a process of drilling, sealing and riveting. Industrial process involves more than 4000 lock-bolt rivets fixing fuselage skins-strap and stringers, more than 1200 fixing skins and straps and more than 800 universal rivets
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for stringers coupling. The average in diameter of the rivets is 4.8 mm, with a thickness of skins between 3.0 and 4.0 mm.
FIGURE 2. Fuselage and Nose Fuselage Join-Up Conceptual Assembly Process
The selected pilot case study illustrates some basic rules applied to the definition of the industrialization of the fuselage join-up. This communication presents the pilot model created, its variables and its associated rules. Rules are based on the knowledge of the experts that traditionally conduct the conceptual design of assembly lines.
The responsible to define the scenarios is the PMO (Project Management Office). All the conceptual functional aircraft definition, mainly ‘as design’ and ‘as planned’ definition of the Product, is responsibility of the DE (Design Engineering) in collaboration with ME (Manufacturing Engineering). The ME (Manufacturing Engineering) is responsible to run the case and to define the iDMU (industrial Digital Mock Up) based on the product configuration and the scenario. The final decision is responsibility of the PMO (Project Management Office).
In general, the output of a ‘what-if’ scenario is part of the iDMU (industrial Digital Mock Up) 0 and relates to the following elements:
� Product ‘as design’ and ‘as planned’ definition and requirements. � Plant requirements. � Jigs & tools requirements. � Industrial Means requirements. � Human resources and associated skills requirements. � Non recurrent Cost.
Table I. Variables of the pilot scenario considered in the case study. VARIABLE Acronym Type Unit Value
Assembly technology AT enumeration none manual/automatic Plant logistics strategy PL enumeration none internal/outsourced
Crane availability CA logical None yes/no Crane capacity CC real number Tons T
Table I shows the variables of the pilot scenario selected to present the case study. Associated to each element is the type of variable, the unit (if applicable) and the possible values. For the crane capacity the value selected is represented by T.
The starting point to develop the case study is the definition of the assembly process for the fuselage join-up. The basic functional specification of the expected assembly process is:
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� Positioning rear fuselage on references on jigs. � Positioning nose fuselage on references on jigs. � Nose fuselage approach for nesting. � Measurement interfaces and alignment. � Nesting.� Join-up (drilling, sealing and riveting/fastening operations).� Final measurement of interface. � Removal from jig.
Based on the scenario, rules are applied in each assembly operation. For the first two operations, ‘Positioning rear fuselage on reference on jig’ and ‘Positioning rear fuselage on jig’; the rules to apply are listed in the Table II.
Table II. Rules to apply for the ‘Positioning fuselage on reference on jig’. Rules Assembly
Process Jigs & tools
Industrial Means
Human Resources
PL CA CC Positioning Ref. Jig Type Cost Skills # outsourced yes T>weight = = Crane C1 Outsourced 0 outsourced yes/no T<weight = = Tool C2 Outsourced 0
internal yes T>weight = = Crane 0 Logistics N1 internal yes/no T<weight = = Tool C3 Logistics N2
Depending on the value selected for the scenario variables, rules are applied and the corresponding output calculated. Table II shows all possible values of the variables and the associated rules (Scenario acronyms are defined in Table I and weight represent the fuselage weight). Functional assembly process and the reference tool is always the same, but depending on the value of the three scenario variables: Plant Logistics Strategy, Crane availability and Crane capacity; the output values: Industrial Means attributes (type and cost) and Human Resources attributes (skills and quantity); are different.
As an example of scenario, what would happen if the following values for the variables: Plant Logistics (PL=internal), Crane Availability (CA=yes) and Crane Capacity (CC<weight) are selected? Then it is not possible to elevate the fuselage using the crane. As a consequence, it is needed a transfer tool to load the fuselage on the reference on the jig. The transfer tool has a cost of C3 and N2 workers with logistic skills are needed to complete the process. The routines to calculate C1, C2, C3, N1 and N2 are triggered by the result of the rule.
A similar set of rules can be applied to the ‘join-up’ assembly operation. For this assembly operation, the most relevant scenario variable is the Assembly Technology (AT).
Table III. Rules to apply for the ‘join-up’. Rules Assembly Process Jigs & tools Industrial Means Human
Resources AT Join-up Ref. Jig Type Cost Skills #
Manual = = Templates C1 Assemblers N1 Automatic = = CN machine C2 Machinist N2
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The results to apply rules are different depending on the ‘manual’ or ‘automatic’ value of the scenario variable. Table III shows both values and the associated rules. Functional assembly process and the reference tool is always the same, but Industrial Means attributes (Type and Cost) and Human Resources attributes (Skill and Quantity) are different.
If the scenario is defined considering a manual Assembly Technology (AT=manual), then it is necessary to built templates for drilling/riveting the fuselage with a cost of C1. The skills of the workers are the corresponding to mechanical assemblers. The quantity of workers needed is then N1.
On the other hand, what would happen if an automatic Assembly Technology (AT=automatic) is considered? Then it is necessary to have a CN machine to drill the fuselage with a cost of C2. The skills of the workers are the corresponding to CN machinist and the quantity of required workers is then equal to N2. The routines to calculate C1, C2, N1 and N2 are triggered by the result of the rule.
RESULTS AND DISCUSSION
The result presented is a pilot text-based case study illustrating the evolution of the input requirements for the conceptual design of aerospace assembly lines. The rationale of the scenario and the rules are explained to understand the impact that the input requirements have on the output to be created.
Similar type of rules should be defined for the rest of the operations of an assembly line. This pilot case study shows the implications of creating a quantitative model to define ‘what-if’ scenarios. Adding more variables to the scenario should improve its prediction capabilities. However, it should keep in mind that when the number of variables increases then the number of rules to define also increases, and the complexity of the model is higher.
A relevant aspect to estimate is the uncertainty that is expected from the model and if such uncertainty is suitable for the goals of the scenario. Ultimately, the scope and goals of the scenario should determine the establishment of a complete set of variables, the corresponding decision rules and the routines to calculate the scenario output. An extended scenario is the aim to let the engineers to define early, during the Conceptual Design Phase, the different technologies to be used in the product and in the process: industrial means, human resources and skills, main machinery and tooling. The impact on requirement changes or design alternatives can be checked with a ‘what-if’ analysis.
When considering the Conceptual Design Phase 0 0, the main assembly line characteristics to be defined can be grouped into four main outputs:
� Assembly Process: Conceptual ‘as prepared’ configuration � Assembly Resources: Conceptual jigs & tools and industrial means
requirements � Scenario Results. To feedback Program management Office. � Industrialization requirements: Conceptual ‘as planned’ requirements.
The four set of result comprises the technical definition of the assembly processes and resources and planning related information. The results of the scenario include
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also an indication for necessary human resources and their skills, recurrent and non recurrent cost and for the impact on the lead times and delivery dates. With all the information, the Program Management Office can establish a business plan to evaluate the different solutions and can take a final decision on what to implement.
The main advantage of ‘what-if’ scenarios in the earlier phases of the lifecycle is the possibility to define very soon a set of requirements that have a long lead time. Once the Program Management Office has taken a decision using the information derived from the different ‘what-if’ analysis it is possible to launch actions like the procurement of complex jigs & tools or CNC machines, training for new workers, etc. More complex scenarios could include the building of new hangars or complete new assembly plants. Aircraft assembly cost, lead-times and delivery dates can be secured and establish in the beginning.
FIGURE 3. Fuselage and Nose Fuselage Join Up Final Assembly Process.
As an example, Figure 3 shows a partial view of the AIRBUS A400M final iDMU for the fuselage join-up assembly process in the Station 60, with the associated jigs & tools and industrial means. The result was obtained after following the complete design process of the assembly line. At the Conceptual Phase the work was conducted by experts making use of spreadsheets, drawings, CAD models, etc. Scenarios were defined and executed manually. The ultimate aim of the presented pilot case study was to show the implication of the aimed development. With the formalization into a software application of the scenarios definition and execution, it is possible to reduce the design time needed and to facilitate its documentation and inclusion into the iDMU.
CONCLUSIONS
This paper presents a pilot ‘what-if’ scenario for a process view approach adopted for the conceptual design of aerospace assembly lines. The objective was to show the implications of creating a quantitative model to define ‘what-if’ scenarios in such design phase. A fuselage join-up process was selected, and rules for the fuselage
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positioning and assembly technology were showed. The process view approach and the ‘what-if’ scenario proposal are innovative and the main contribution of this paper. Literature review points out the interest of this area of work and the need for further contributions.
The case study presented focuses on the conceptual phase and possible ‘what-if’ scenarios. Depending on the values of the scenario variables feasible outcomes are derived with their associated values for their attributes. The scenario helps to define the design solutions that will meet the functional and industrial requirements. Therefore defines the basic requirements of functional design and industrialization. Several alternatives are studied considering the most attractive in terms of performance and cost. Although the pilot case study is very limited, it shows the direction where the overall research is aimed and the procedure to follow. It also helped to identify the difficulties that arise when extracting and documenting procedure knowledge from personnel. The ‘what-if’ scenario is a predictive tool that allows checking a large number of alternatives and it is a huge advantage over the current method based on people knowledge and expertise, CAD and office tools.
ACKNOWLEDGEMENTS
The authors want to express their most sincere gratitude to the colleagues of UPM and AIRBUS Military, who kindly collaborated in this project.
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