Specification of a generic PLM system dedicated to SMEs based on a PPRO meta-model

Specification of a generic PLM system dedicated to SMEs based on a PPRO meta-model Julien Le Duigou 1, 2, Alain Bernard 1, Nicolas Perry 3, Jean-Charles Delplace 2 1 IRCCyN, Ecole Centrale de Nantes, France 2 Centre technique de l industrie mécanique, France 3 LGM 2 B, Université de Bordeaux1, France Abstract Integration of PLM systems in the Small and Medium Enterprises (SMEs) is an important way of improvement for the extended enterprise. The proposition is an inductive approach that enables the specification of a PLM system dedicated to SMEs in the field of mechanical engineering. This study proposes, at the conceptual level, a generic solution with specific solutions proposals, based on three immersions in SMEs. The paper presents the inductive process and a Product Process Resource Organization meta-model for the specification of a generic PLM system in the framework of an extended enterprise in the mechanical engineering field. Keywords: Product Life Cycle Management; Meta-Model; Extended Enterprise; Information System 1 INTRODUCTION In 2007, the Cetim (French industrial technical centre that represents 7800 French mechanical industry companies) has performed a survey on digital and collaborative engineering for the mechanical engineering companies. This survey shows that only 5% of SMEs of fewer than 100 people use a PLM system to manage their technical data. However, more than 70% of these same SMEs consider as important the reuse of knowledge, the share of information within the company and outside, the security of information access and storage and the follow-up of modifications [1]. These are some of the functionalities offered by the PLM software tools. The actual systems fit to the prime contractors needs, but little to the SMEs capabilities. To solve this problem, SMEs in the mechanical field, need the implementation of specific methods and information system models adapted to their needs. The first section introduces the scientific studies that enable to establish the starting point of the proposed approach. Section 3 presents the work method, an inductive research/action approach, based on a spiral cycle structured on successive phases of analysis, development, experimentation, and then linking up with the methods and models enriched by experience feedback. Section 4 describes the immersions in three different companies chosen with respect to a typology of the mechanical engineering SMEs. This immersion phase will specify the generic meta-model and deployment method for a PLM system mainly dedicated to product data integration and management. 2 PLM: FROM CONCEPT TO META-MODEL This chapter focuses on the design of PLM and examines the different modelling methods for information structure on which the PLM functionalities are based. It is conclude by an analysis of the different standards that enable the communication and sharing of information and practical technical data between companies that do not have the same data model and the same business processes. 2.1 The PLM concept PLM is first an enterprise strategy. It involves managing all the data concerning a product, throughout its life-cycle, and all the internal and external actors involved in the development of this product. As explain by Sudarsan [2], the Product Lifecycle Management (PLM) concept holds the promise of seamlessly integrating all the information produced throughout all phases of a product s life cycle to everyone in an organization at every managerial and technical level, along with key suppliers and customers. PLM systems are tools that implement the PLM concept. Much work has been done in this field, especially in the aeronautic and automobile sectors in order to propose technical data management methods [3, 4]. Some others try to address the SME specificities and propose solutions such as Delplace for sand casting foundries [5]. 2.2 The modelling of business objects PLM relies on a data model being composed of business objects that intervene in the business processes. Several modelling methods and languages have been developed so as to model these objects. Many modelling languages represent these objects and the related activities, such as SADT, IDEF3, BPMN [6] or FBS-PPRE [7]. The establishments of patterns, based on this modelling language, describe an approach to represent the processes (CIMOSA [8], ARIS [9], GERAM [10], GRAI [11], PERA [12] ). These methods contribute to the adjustment of methods and data models required for PLM implementation. Nevertheless, in an extended enterprise context, it is necessary for these different models to be able to communicate or interoperate together. Therefore different methods allow this interoperability based on enterprise

modelling approaches [13]. A solution is based on standardized models required to enable sharing or communication between companies that have not made the same choice of modelling. 2.3 The standards data models Much work in different sectors tries to increase the interoperability of data models with standards, using mainly the STEP norm for example (STandards for the Exchange of Product model data) [14, 15]. STEP is an international exchange standard of ISO (ISO 10303), that describes how to represent and exchange product models by covering the whole life-cycle [16]. STEP uses a formal representation language of data called EXPRESS [17], and its graphical representation, EXPRESS-G. The Application Protocols (AP) are information models of STEP specific for an industry and/or a life-cycle phase. In the mechanical field, AP214 [18] is specific to the automobile sector, and AP239 [19] is dedicated to the aeronautic sector. Those models are not fully interoperable, despite having common integrated resources. The main reason comes from the semantic difference of the objects and their attributes depending on the sector of application. Hence the creation of PDM Schema [20] tried to unify the different information models of STEP APs using their common objects. It seems that if many methods exist for modelling business objects, their use for the creation and maintenance of a data model that supports PLM is not detailed enough for industrial exploitation in SMEs. FBS-PPRE modelling proposal enables the dynamic representation of objects independently of their roles (the same object can be a product, a resource or a process, depending on the context), which seems to be an innovative way to manage objects in an extended enterprise context. Moreover, despite the existence of standards, it is still difficult to get data models both adapted to the company and interoperable with the standards. So the approach developed must use the maximum of the appropriate standards for SMEs in the field of mechanical engineering industry. The following paragraphs explain the proposition to obtain this result. 3 RESEARCH APPROACH The approach proposes a methodology in order to structure and manage the product data of extended enterprise. Id est methods to structure and manage product models and data. To define these methods and to reach a common approach for the different companies, an inductive three-step research approach is implemented: Immersion: needs analysis and integration of specific methods. Generalization: creation of a generic approach. Validation: experiment of the approach, back to an extended enterprise. 3.1 Immersion: needs analysis and integration of specific methods The first phase relies in interviews of companies to extract their practices in terms of digital and collaborative engineering and the best practices of implementation. Moreover, a bench was done on the PLM software tools to list the functionalities and their ability to meet SMEs needs. The pilot companies, representative of the mechanical industry and their common requirements were selected. Then, the immersions into the different companies were done in order to directly and inductively integrate the technical data structuring and managing methods. This phase was coupled with the implementation of the methods with real data in the companies to verify the gap between the proposal and the objectives. 3.2 Generalization: a generic proposal In this phase, based on the analysis of the different pilot companies, the method of managing product data is generalized, and a meta-model is created. This approach has to be compatible with the standards and applicable to all the types of companies in the mechanical industry so that it may be use in an extended enterprise context. One of the main points of the generalization phase is the interoperability of the applications. Chen [21] distinguishes three different approaches for interoperability: - the integrated approach uses a common model for the whole enterprise, - the unified model uses a neutral formalism to express the concepts and their relations while the users models are unchanged - the federated approach couples the individual models with a common ontology. To create a generic meta-model, the paper focus on the integrated approach, considers as consistent, but not easy to be adopted by users who want to preserve their own models or tools [22]. To unlock this point, an approach is proposed in the last chapter. 3.3 Validation: experiment of the proposal The experiment feedback will test, improve and validate the Information System structure proposal. The model will be implemented by the creation of a software prototype, base on an object database and a client interface link via web services. Tested in an extended enterprise environment, the implementation method and its suitability to the requirements of product data management will be implemented playing use cases on real data. 4 IMMERSION IN COMPANIES In this paragraph a typology to choose the pilot companies is proposed. Then the initial situation and the proposal in one company of each SME of the typology will be explained. Finally, assess of those immersions is proposed. 4.1 Typology of mechanical engineering SMEs The pilot companies for the research experiment have to be chosen. To obtain results that allow generalizing to the whole extended enterprise, a typology of the different companies that could be integrated into this kind of enterprise is proposed. The differentiation axes are the number of parts in the product (produced by the SME). Indeed, the companies with a large number of parts by product often manage BoM to manage their product data. At the opposite, the companies with a little number of parts by products manage routes and operation to manage their product data. And last, some companies manage both BoM and routes. Thereby three types of SME are identified in the proposed typology (Figure 1).

It also allows extracting the knowledge useful to their transfer and especially concerning the multi-view of a product. This multi-view notion is applied using a buffer file that contains all the information of the product, the structuring of the product being specific to each view. Figure 2: Product Project objects Figure 1: Typology of mechanical SMEs This typology classifies the different companies present in an extended enterprise, from the toolmaker to the integrator, through all the intermediaries. Then, three companies covering the three zones of the typology were chosen as pilot companies. By analysing the needs of these different companies, the generic needs is extracted (the needs that are not specific to the activity of the company) and aggregated to obtain the specifications of a generic model for the extended enterprise. The next case studies must enable to put into practice methods of technical data structuring and management, adapted to those specific companies. In order to do this, the study starts by analysing the needs of the company in terms of PLM. Then it proposes a specific approach to improve the initial situation. And finally, the method is validated by integrating a specific solution in the company. 4.2 A machine producer: SMP The first case study is SMP, a grinding machine producer. This company is a type I in the typology. Due to the high number of components of its products and its high customisation, this type of company often encounters bill of material (BoM) problems. After the audit phase, an approach based on a double view of the BoM is proposed. Using a buffer file without structuring the product, a different structuring in each department of the company based on the same data is possible. First of all, the different information needed by the engineering and the production departments are selected. A list of attributes is made for each kind of products, sub assemblies and assemblies. A BoM is created in a spreadsheet for the engineering department extracting from the list of attributes only those wanted by this department and with the same structure as the 3D model. The attributes of this list are link with the CAD files. A second BoM is created for the production department extracting from the same list of attributes only those wanted by this department and with the same structure as the ERP model. This list of attributes is link with the ERP BoM. If a modification occurs, both, the engineering and the production BoM will be automatically changed. If the change is made on a sub-assembly or a part, all the assemblies containing the sub-assembly or the part are updated. This example enables to identify the technical data that is transferred between the engineering department and the planning department in this company. On a generic point of view, four classes of objects are extracted: the product itself, the project link to a product, the task that is an elementary part of the project and the people of the organisation, resources needed by the task. Figure 2 shows the class diagram of those objects. 4.3 An equipment manufacturer: PSL CONCEPT The PSL CONCEPT firm produces and sells equipment for ships. Among these products, there are reserve rudders, pulleys and tackles, sheaves, jam cleats and various accessories. It is a type II company in the typology. This company organizes the main part of its products into families. In fact, as many system integrators and equipment manufacturers, the products are based on standards, customised to fit with the options and modifications required to meet customer needs. The families in PSL CONCEPT are organized by main functions of the products. After the audit, the main need of this company in terms of PLM was to automate the design of their families of products. The study is focused on a major and well-known family of products for the company: the pulleys. A software program was implemented to automatically construct the CAD file of a pulley from the functional requirements. Based on an Axiomatic Design approach [23], the functional parameters of the family of pulleys are linked to the design parameters of each pulley [24]. To create this programme, a breaking down all the possible functionalities of a pulley is done. Then, a functional dimensioning of the different sub-parts of the pulley is carried out and these parameters are set in the CAD file. Then, the dimensioning parameters are brought together in accordance with the functions of the pulley in order to obtain a link between the functions and the parameters in the CAD file. So a parametric model of the family of pulleys is obtain in a single CAD file with a link to the function requirement of each pulley. The software made using Visual Basic language takes the appropriated parameters in a spreadsheet, then calculates those parameters depending on the chosen option, and finally put those parameters in the 3D model. The referencing of the flanges and pulleys is automated in the software. It means that if the part or the assembly is new, the reference is created. If the part is old, the reference is copied. In both cases the references are added to the layouts and the BoM. When the product is an assembly, functionality is added to automate the creation of the BoM, based on the CAD BoM functionality. The drawings were created automatically in order to keep a paper record of the pulleys and its parts. A table for the quotes was also developed to calculate the cost of a pulley depending on its functionalities. Each function has a cost depending on the number of sheaves and the diameter of the fag end. Adding all the costs of the functions required by the customer, the global quote of the pulley is obtained.

A global approach to meet the specific PLM needs of this company is proposed. The implementation of the software based on this approach and the results obtained (the design time for a new pulley has gone from hours to minutes) prove that the approach is adapted to the needs of this kind of company, an equipment integrator (type II) in the mechanical industry. Figure 4: Product Route objects Figure 3: Product Function objects On a modelling level, a product and a function object classes are distinguished. The different attributes of each object (the design parameters and the functional parameters) are link to each other in the elementary level of the product and function. 4.4 An elementary part manufacturer: Capricorn The last pilot company named CAPRICORN. This company manufactures crankshafts, connecting rods and pistons for the up market automotive industry and racing cars (F1, NASCAR, 24H du Mans, Rally ). It is a type III company in the typology. This kind of company has problematic about manufacturing data. The elementary parts manufacturers directly receive their drawings and CAD models from their customers. Then they add their expertise to draw up the process plan of the product and to machine it. The audit phase focus on the semi automation of the process planning of the products. The study focus on the historical product of the company: the crankshaft. The part file is received from a customer using STEP exchange standard. It is opened with the CAD software of Capricorn. The operator chooses the appropriate macro route in a set of patterns. The macro routes were already defined. Those patterns contain the list of operations and the work centres usually used for this kind of operation. From the customer 3D model, the raw part is reconstructed. Then, each machining route is simulated by a feature of cutting. With a face recognition based on fundamental knowledge, it is possible to find the different entities machined in each operation. The information from the product is directly extracted from the STEP file, the information from the work centres and the craft rules was both collected during the audit phase. As a result, the 3D model of each intermediary part is obtained. All the parameters of the detail operation are changeable directly in a specific window of the CAD software. From these detailed operations, drawings are generated with the intermediary dimensioning, tolerance and a full title block. The generation of documentation is done automatically from the 3D model of the intermediary part. They are saved as PDF files and sent to the production department. This case study enables to identify the product data used by the planning department during the industrialisation phase. It also enables to extract the knowledge use internally as well as externally via the exchange between the customer and the production department [25]. On a generic level, product objects and route objects constituted of operation objects are used. The operations need tool and work centre objects to be operational. Figure 4 shows the class diagram of this case study. 4.5 Conclusion on the immersions The specific application integrated in the pilot companies are too specialised to be directly integrated into a generic model for the extended enterprise. Some of those data and some processes are really specific to the product manufactured by the company or to its production processes (sheave diameter or number of crank pins is not be generic attributes of a product). Nevertheless some other can be processed in a global way in the extended enterprise. The next chapter will generalize the different approach use in each case study to generate a single meta-model applicable to the whole extended enterprise. 5 CREATION OF A GENERIC META-MODEL The first step of this generalization is to have a single metamodel applicable to each company aggregating the different specific model of the pilot companies. Then this meta-model will be adapted and enriched to be applicable to an extended enterprise compose of SMEs. 5.1 Aggregation of the specific model By aggregating the three class diagrams of the three pilot companies, the generic model obtain can be applied to the pilot companies, and by extension, to each SMEs of the mechanical industry that have the same product data problems. To aggregate those three models, new class objects are needed: Process, Activity and Resource. The process is a generalization of a project or a route. The activity is a generalization of a task or an operation. The resource is a generalization of a tool, a work centre or a people.

the object allows for example, for a product in one organisation, to become a resource in one other organisation. A proposition of adding to the FBS method an elements playing role of organisation is done. Indeed, it seems important to be able to modelling the structure of the organisation, the function of the organisation and its behaviour. 6 CONCLUSIONS AND PERSPECTIVES Figure 5: PPR meta-model The three approaches that are developed in the pilot companies are transferable to the meta-model Figure 5. The result is a generic Product Process Resources meta-model. But this model is not applicable to the whole extended enterprise because it does not take into account the other companies. It is centred on a unique generic company. To be able to apply this model to an extended enterprise, the Organisation object is missing. 5.2 Adaptation of the model to the extended enterprise Indeed, the organization object allows using this model in an extended enterprise because it allows adding an owner to the processes and resources. The resources and the process are link to the organization. The product is not directly link to an organization and can move from an organization to an other. It doesn t have a unique owner during its lifecycle. The SMEs processes need to be integrated into the digital chain to be fully efficient in the extended enterprise context. This paper makes a proposal for a single PLM system support frameworks that can structure the product information over the entire product lifecycle. From the immersion in three representative SMEs of mechanical industry, four main components that constituted the kernel of such a framework are described. The proposed product process resource and organisation modelling is able to integrated the necessary information for quotation, design and industrialisation of a product. The three immersions into SMEs validate this approach. The next contribution will map the meta-model with the actual data model standards such as STEP AP 214 to have a more comprehensive language and to be able to extract the strictly necessary objects for the SMEs that needs to be implemented. As explain in the research approach, those method and model will be validated by a second experimentation phase with the integration of a collaborative tool based on this meta-model in an extended enterprise. The last point is to map this PPRO meta-model with other existing model and methods to be able to focus on the specificities of the extended enterprises including SMEs. 7 ACKNOWLEDGEMENTS We would like to thanks PSL CONCEPT, CAPRICORN and SMP companies for allowing us to carry out our study in their companies and for their technical support. 8 REFERENCES Figure 6: PPRO meta-model As explain in the first chapter the FBS PPRE method is chosen to define the business objects. In this methods, Labrousse [26] explain that each object, independently of its role (product, process, resource or external effect), have a function, a behaviour and a structure. The dynamic role of [1] Cetim, 2007, Enquête de besoin sur le travail collaboratif, Document interne. [2] Sudarsan, R., Fenves, S.J., Sriram, R.D., Wang, F., A product information modeling framework for product lifecycle management, Computer-Aided Design 37 (2005), pp. 1399-1411. [3] Bacha, R., 2002, De la gestion des données techniques pour l ingénierie de production. Référentiel du domaine et cadre méthodologique pour l ingénierie des systèmes d information techniques en entreprise, Thèse de doctorat, Ecole Centrale Paris. [4] Nguyen Van, T., 2006, System engineering for collaborative data management systems: Application to design/simulation loops, PhD thesis, Ecole Centrale Paris. [5] Delplace, J.C., 2004, L Ingénierie numérique pour l amélioration des processus décisionnels et opérationnels en fonderie, Thèse de doctorat, Ecole Centrale de Nantes.

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