Julien Le Duigou
email: julien.leduigou@irccyn.ec-nantes.fr

Alain Bernard
email: alain.bernard@irccyn.ec-nantes.fr

Nicolas Perry
email: nicolas.perry@iut.u-bordeaux1.fr

Jean-Charles Delplace
email: jean-charles.delplace@cetim.fr

Application of PLM processes to respond to mechanical SMEs needs

Keywords: Product Lifecycle Management, Product-Process modelling, Information System

PLM is today a reality for mechanical SMEs. Some companies implement PLM systems very well but others have more difficulties. This paper aims to explain why some SMEs do not success to integrated PLM systems analyzing the needs of mechanical SMEs, the processes to implement to respond to those needs and the actual PLM software functionalities. The proposition of a typology of those companies and the responses of those needs by PLM processes will be explain through the applications of a demonstrator applying appropriate generic data model and modelling framework.

INTRODUCTION

Due to globalisation, the enterprises have to work in networks more and more diversified and geographically dispersed. To allow this, optimizing the cost, quality and delay, enterprises implement new information and communication technologies. The mechanical SMEs are in the same logical. But those enterprises, even if they are more flexible, have difficulties in front of those new possibilities of exchange and share of information. PLM systems are one solution to structure and share product information. Nevertheless, in 2007, only 3% of those enterprises have implemented such a system [START_REF] Cetim | Enquête de besoin sur le travail collaboratif[END_REF][START_REF] Balocco | Innovare e competere con le ICT -Il ruolo delle tecnologie dell'informazione e della comunicazione nella crescita delle PMI[END_REF]. Our hypothesis is that the functionalities of the actual systems do not feat with the needs of those enterprises. This paper introduces first the functionalities of PLM systems. Section 3 explains our research approach based on immersions in mechanical SMEs from a PLM dedicated typology. Then the needs of those companies are identified, the processes to respond to those needs are formalised and finally the application of a demonstrator based on a generic model is proposed. Discussion and perspectives conclude this paper.

PLM PROCESSES

CimData [START_REF]Product Lifecycle Management "Empowering the future of business[END_REF] define the PLM as "a strategic business approach that applies a consistent set of business solutions in support of the collaborative creation, management, dissemination and use of product definition information across the extended enterprise from concept to end of life -integrating people, processes, business system, and information". The actual definitions of PLM [START_REF] Stark | Product Lifecycle Management: Paradigm for 21st century Product Realisation[END_REF][START_REF] Terzi | Element of Product Lifecycle Management: Definitions, Open Issues and Reference Models[END_REF] focus on the product data, but do not include the processes management notion. To improve that point, the following definition centred on the activities is proposed: "PLM is a business strategy to manage on a collaborative way the product centred activities during the whole lifecycle and across the extended enterprise". PLM encompass not only the definition of the product, but also the definition of the product lines, of the technologies used, of the organization, of services associated to the product (services during it use, but also during it maintenance, it end of life…). In a mechanical SMEs context, the production lines are not redefined with the creation of a new product. SMEs have to produce new products with the existing work centres, which is not the case for the firms from automobile or aeronautical sectors where a new production line can be create for the creation of a new product. It is quite the same for technologies used and the organization that do not change with the arrival of a new product. The services are not taken into account by mechanical SMEs, maybe because they are not yet in charge of the maintenance and end of life of their product or because they have to manage the definition of their product before manage their maintenance or their end of life. PLM is support by business software. The PLM systems help to pass the product definition information from one business solution to another (Figure 1). Interoperability and modularity are important issues in those systems [START_REF] Dutta | Sustaining product innovation thru PLM[END_REF]. It encapsulates and then diffuses the information for the product development. It is realized by links between the PLM systems and the other software (Figure 1), as CAD, CAM, ERP, SCM… It ensures the traceability [START_REF] Terzi | Element of Product Lifecycle Management: Definitions, Open Issues and Reference Models[END_REF], the archiving [START_REF] Lowe | Information access, storage and use by engineering designers[END_REF] and the reuse [START_REF] Gzara | Les patterns pour l'ingénierie des systèmes d'information produit[END_REF] of information.

Figure 1: PLM and business software

The PLM systems offer numerous functionalities, the most classical are: Vault: the data and documents are stocked in a server. The data are stocked in a database and structured through the data model implement in the database. Right access: the user must have sufficient right access to operate on the data (read, modify, validate…). Check in / check out: the user must check out the document before modified it. Then he checks in the modified document. This assures that two users cannot modify a document at the same time. Versioning: it traces the change of a document or a data. At a second level, a revision serves to trace major modifications. Notification: notification is the sending of an email with a link to the data or document subject of the email. Automatic notification for change, validation… is called subscription. Workflow: this system simulates processes and automates some activities of the process. It is principally use for documentation processes like validation. State: they are associated to document and define their maturity level (creation, in validation, validated, obsolete). Actual tools are mainly dedicated to documentation and communication management. The possibility to automate and manage activities more business oriented is not in the actual functionalities. SMEs are looking for more advanced business functionalities. Notice that the majority of the works done on PLM are related to firm, often automobile or aeronautic assemblers [START_REF] Seine | [END_REF][START_REF] Braudel | Overall presentation of ENANCE Project, Production cost & time to market -Aircraft Technologies[END_REF]11]. Deductive approaches are used to integrate SMEs in the assemblers' point of view. An inductive approach will be more appropriated to include SMEs needs.

RESEARCH APPROACH

To propose processes and functionalities appropriate to SMEs to structure and to exchange product information, our approach inverse the traditional V cycle. It starts with a first inductive and raising step to formalise the needs and the processes to implement. The second step is deductive and downing to validate the propositions (Figure 2). For the enterprises of which the products have a few components work on the manufacturing of the parts. The product information are then in the routings. So the proposed typology has as differentiation axis the number of components per product. The different companies are grouped according to the number of components of the products that they design and/or produce (Figure 3). The companies producing components.

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The companies producing craft parts. The equipment manufacturers are companies of which the products contain numerous components. They produce special machines, agricultural machines, stevedoring machines… they have problematic about BoM management and traceability, well known of the PLM systems because they match to the needs of the big firms of the automobile and aeronautic sectors which introduce those software. The solutions to implement are lighter and less complex than the big firms' solutions. The component manufacturers are companies of which the product contains a medium number of components. These enterprises design and/or produce compressors and motors, tools, transmissions (hydraulic, mechanic or pneumatic)… They have various needs from the customer needs analysis to the manufacturing. The craft parts manufacturers have a few components in their products. They produce discrete parts from the forging, foundry, machining, drawing… these enterprises have problematic about the routings management.

After have apply the approach on three different enterprises, the result is three needs' maps, three processes models and three data models [START_REF] Duigou | Inductive approach for the specification of a generic PLM system in an extended enterprise context[END_REF][START_REF] Duigou | A constraints driven Product Lifecycle Management framework[END_REF]. The aggregation of those results permits to define a generic model for the mechanical SMEs (Figure 4).

Identification of the needs

The principal problems of each enterprise were identified in [START_REF] Duigou | Inductive approach for the specification of a generic PLM system in an extended enterprise context[END_REF][START_REF] Duigou | A constraints driven Product Lifecycle Management framework[END_REF]. A list of PLM needs is created from those immersions. The needs retain in the list are those which are not fully implement in the actual PLM systems. Following our study, six classes of needs are identified: Configuration management: it comes from the equipment part manufacturers. The PLM systems must manage the alternative, the options, the versions, the families and the differentiation between internal and external products. Collaboration: the exchange with the customers (for the parts and components manufacturers) and with the suppliers (for the components and equipments manufacturers) must be facilitated and standardized, especially for the CAD files exchanges. Multiple views: the information has to be visible with the structure and the names of each department. It is particularly need for the BoM in design and production departments, corresponding to the structures of the CAD and the ERP. Routing management: the raw parts manufacturers need that the routings and the whole information that it includes (operations, work centres, tools…) could be manage from the PLM systems. Interoperability: the interoperability with the ERP and the CAD is asked from the three types of SMEs, especially for the BoM and routing update. Decision aid indicators: the cost is the indicator the most asked, to choice between alternative products for the equipments manufacturers or to choice between alternative operations in a routing for the raw parts manufacturers. Those needs have to be resolve by the PLM systems to interest the mechanical SMEs. The processes implement in the pilot enterprises solve those needs. The generalisation of those processes should help to solve the generic needs.

Formalisation of the processes

The processes covert by the pilot companies could be aggregate to represent a complete development product in an extended enterprise. The required level of detail of the SADT makes appear the intermediaries. To know the processes of creation, use and decommission of those intermediaries in the information system, it is necessary to know those processes in the real life with the same level of detail.

Moreover it is necessary to reach this level of detail in the three companies to be able to generalize appropriately the processes. Indeed the same intermediaries are in several companies, continuing their life cycle passing from a company to another. This exchange of intermediaries allows linking the processes from one company to another, like in an extended enterprise.

Figure 5: PLM processes The global process Figure 5 is a development process. It includes the need analysis, the design and the industrialization. The production, the sale, the distribution and the end of life of the product are not covert by this process which is focus on the SMEs context. As explain previously, the mechanical SMEs do not express the wish to include those processes. To manage those processes, an appropriate data model is required. The objects to include in the data model are those used by the processes and which appear as input and output of the activities.

Realisation of the processes

The model generalizes the objects used in the pilot companies to obtain generic objects. The semantic alignment was the principal difficulty. One object can be named differently depending of the enterprise. The fact that one consultant have done the three models makes easier the concatenation of the objects. The generic objects are represented in the UML class diagram Figure 6. The different identified objects are the activity, the product, the material, the function, the resource, the trigger, the organization and the document. The activity specializes into task and operation, the organization into customer and supplier and the resource into material, human and software resource. More explanations about the generic model are in [START_REF] Duigou | Specification of a generic PLM system dedicated to SMEs based on a PPRO meta-model[END_REF]. The objects at the generic level are not enough specific to be really useful in a particular company. A framework that proposed an instantiation of the generic model is proposed to match with the particular objects of each enterprise keeping a high level semantic alignment. Based on modelling approaches like CIMOSA or GERAM [START_REF] Kosanke | CIMOSA modelling processes[END_REF][START_REF] Geram | GERAM: Generalised Enterprise Reference Architecture and Methodology v1.6.3[END_REF], the framework proposes a system with needs, processes and data model coherent for the three pilot enterprises. Figure 7 shows a cube representing the framework. The abscissa represents the three results of the modelling method: the needs map, the processes model and the data model. The ordinate represents the instantiation of the three components, the generic, partial or particular levels. And the depth represents the different views of the systems, process, information, resource and organization. The generic model proposes a union of the views process, information and resource. It also integrated the organizational view that coordinates the other views. This axe notices the different views that are modelled, even if they are all integrated in the generic model. The proposed generic model is implemented in the demonstrator, with the generic classes, attributes and methods. Each class is specialisable in sub-class, inheriting of the attributes and methods of the father class. New attributes could be added to the new class. A new specialization is applicable to the sub-classes and so on. The interface is constitued of a tool bar, a treeview, a fileview, a data card and a viewer (Figure 9).

APPLICATION OF THE DEMONSTRATOR

The application is chosen to cover the maximum of identified needs. The study needs are: the configuration management, the link with the supplier, the multiple views, the link with the CAD and ERP, the routings management and the cost indicator. The configuration management is partially covered by actual PLM systems. It is principally a request from the equipment manufacturer. The creation of product family and the differentiation between internal and external products is nevertheless simplified in the demonstrator. To create a product family, the user right clicks on the generic class of product on the treeview and select new. A new sub-class (a family of product) is created, inheriting of the attributes of the product class plus the new that the user defines for this family. Each product create in this family will obtain the attribute of the family. Sub family can be created reproducing the same method on a family. The internal and external products are in the referential of the enterprise with different colours (yellow for the internal products and green for the external products). The external product can be taken directly from the supplier PLM systems. The different suppliers identified are present in a specific folder. A drag and drop from a component of the supplier to the demonstrator imports the product, all the attributes and the attached files. The composition of a product is not the same depending of the user's work in the enterprise. There is no universal view appropriate for all the business units and each business view gives advantages to their users. In the present work, three views are retained: functional, structural and manufacturing [START_REF] El Kadiri | Current situation of PLM systems in SME/SMI: Survey's results and analysis[END_REF]. In the structure view (Figure 10), the components of the product are decomposed in the treeview. To obtain a functional view, the user has to change the view clicking on the function button. Then he can create functions under the product (the internal functions) and add in the components of the product (the functions of service of the components). So the product is decomposed from a functional point of view. In the manufacturing view, the assembling operations are linking to the product and to the component (Figure 11). It gives a manufacturing structure of the product through a product -assembly -component decomposition of the product. In each view, some objects can be added separately. The object is visible in the selected view and not in the others. It could be the case for the addition of grease in the manufacturing BoM that do not have to be visible in the design BoM. The interoperability of the PLM systems with the CAD and the ERP are the most important link to create [START_REF] Salau | La Conception Distribuée : Théorie et Méthodologie[END_REF]. For the CAD link, the designer imports the assembly treeview of the product with a drag and drop of the CAD file from the office to the demonstrator. The CAD treeview is then copied in the structure view. The components are created and the corresponding CAD files are imported in the right component objects. With the import of the CAD file, a link is created between the CAD attributes and the object attributes (for the attributes with the same name in the CAD system and in the demonstrator). Those attributes are then synchronized. The implementation is done on SolidWorks from Dassault Systems.

The manufacturing view can be synchronised with the ERP of the enterprise to obtain BoM and routings up to date. A mapping with an ERP is implemented in the demonstrator. It synchronised the items, the operations, the work centres, and all their respective attributes, updating the BoM and the routings. This is done on the ERP EFACS from EXEL Computer System, using the data base Informix from IBM.

The management of the routings directly in the PLM systems is a wish of the components and raw parts manufacturers.

To create a routing, the user creates the different operations in the product (Figure 12). He can define optional operations, alternative operations and external operations (appearing in green and not in yellow as the internal operations). Then he loads the resources useful to each operation dropping the input items, the work centres, the tools…

DISCUSSION

The contribution of this work is in two parts: in one hand the identification of the needs of mechanical SMEs in terms of PLM, and in the other the resolution of those needs based on a generic data model.

The identification of the needs of mechanical SMEs is done based on three representative companies. The number of studied companies is few for a generalisation but we assume that the choice of the companies based on the typology explain in section 3, combining with the immersion in those companies gives a realistic view of the problems encounter by the mechanical SMEs on this subject.

The second point is the realisation of the processes based on the generic model and adapted to the particular company following a modelling framework. The demonstrator implements the objects of the generic model and its specialisation. The implementation of this demonstrator in an enterprise on a major project will validated the robustness and the appropriateness of our approach.

CONCLUSIONS AND PERSPECTIVES

The SMEs do not integrated easily the PLM systems. Their needs do not match to the actual PLM functionalities. Our approach classifies the needs of mechanical SMEs based on immersions in representatives companies. Then the processes to be implemented in those enterprises to respond to those needs are formalized. And then the data model to implement in the PLM system is deduced from the processes. Finally the data model is implement in a demonstrator and it use to solves identified needs showing the technical feasibility and the applicability of our approach. The next contribution will be a detailed explanation of the generic model and the modeling framework to allow its use by other companies.

Figure 2 :

 2 Figure 2: Research approach

Figure 3 :

 3 Figure 3: Typology of mechanical SMEs

Figure 4 :

 4 Figure 4: Generalisation approach

Figure 6 :

 6 Figure 6: Class diagram of the generic model

Figure 7 :

 7 Figure 7: Modelling framework

Figure 8 :

 8 Figure 8: Demonstrator's architecture

Figure 9 :

 9 Figure 9: Demonstrator's interface

Figure 10 :Figure 11 :

 1011 Figure 10: Structural decomposition of a grinding machine

Figure 12 :

 12 Figure 12: Routing of a crankshaft

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.


INTRODUCTION

Concurrent engineering taking into account product life-cycle factors seems to be one of the industrial challenges of the next years. Companies have to elaborate more accurate an reactive plans in order to be able to be in accordance with economical challenges.

Cost estimation and management are two main strategic tasks that imply the possibility of managing costs at the earliest stages of product development.

This is why it is indispensable to let people from economics and from industrial engineering collaborates in order to find the best solution for enterprise progress for economical factors mastering.

But such target is not so easy to define and to characterize. So, consequently, this is always difficult to understand the different mechanisms that are on the critical path on each of the enterprise processes.

The objective is not to re-invent economical evaluation methods but to try to adapt them to the new industrial context and configuration in order to give pertinent decision aid for product and process choices.

A second very important factor is related to cost management problems when developing new products. How to let product development actors have referenced elements to product life-cycle costs and impacts? How to let them have idea bout economical indicators when taking decisions during the progression of the project of product development?

The following paragraphs give some fundamentals about economic methods related to the determination of value chains and the evaluation of industrial costs. An industrial application to casting industry is described and argues as a first application of our approach for economical factors evaluation and control.

CONTEXT EVOLUTION

The new international market context increases, for the design and manufacturing enterprises, the need of reactivity and agility. However, customer's requirements change: high quality, shorter time to market, innovative and custom products, various services and of course lower prices. For a few decades, the companies have faced significant environment modifications and then had to adapt their management tools, mainly cost management tools.

First, the concept of enterprise evolves to a more dynamic structure that implies the necessity of new methods for performance evaluation and mainly cost estimation.

The development of automation in the production's operations involves the reduction of the labour ABSTRACT: Concurrent engineering taking into account product life-cycle factors seems to be one of the industrial challenges of the next years. Cost estimation and management are two main strategic tasks that imply the possibility of managing costs at the earliest stages of product development. This is why it is indispensable to let people from economics and from industrial engineering collaborates in order to find the best solution for enterprise progress for economical factors mastering. The objective of this paper is to present who we try to adapt costing methods in a PLM and CE point of view to the new industrial context and configuration in order to give pertinent decision aid for product and process choices. A very important factor is related to cost management problems when developing new products. A case study is introduced that presents how product development actors have referenced elements to product life-cycle costs and impacts, how they have an idea bout economical indicators when taking decisions during the progression of the project of product development.

direct costs. In opposition, the indirect costs, related for example to the maintenance of the reconfigurable manufacturing systems, are more important.

However, in the traditional accountancy systems (method based on homogeneous sections), the overheads are often arbitrary. This does not have any incidence when the percentage of overheads is weak (the impact on the unit costs can be negligible); for example, the time cost of labour can be raised by a coefficient representing a quota of the administration expenses. But when these indirect parts, instead of being residual, represent the major part of the costs, it is necessary to apply finer methods of analysis.

Moreover, the organization of the companies changed. Due to the just in time methodologies, the old functional structure, which means a vertical hierarchical management, changed in a horizontal management including a higher coordination between the services. Therefore, the functional cost division is no longer useful for management. For example, the cost of an after-sale, use to be linked with the commercial function, can be caused by a manufacturing defect; consequently these are the process but not the products that had to be reconsidered. The activities that related to the concept of "value chain", popularised by Mr. Porter (Porter & al. 1995[START_REF] Ambec | A theoretical foundation of the Porter hypothesis[END_REF], made much in the awakening of these phenomena.

Second, a widen competing field has to be taken into consideration.

The growing width of the competing field led the companies to reduce on the one hand the times of decision (through the availability of correct economic information at the good time.), and on the other hand the risks of bad decisions (complete visibility of the impacts during the totality of the product life cycle). Therefore, it is essential to have reliable metrics making it possible to quantify the costs and times a priori resulting from an evolution from the products/process at one unspecified time of their life-cycle. Such indicators, which integrate the technique and economic points of view with various steps of the product/process life cycle do not yet exist, or if they do, give an incomplete or not reliable answer. In 1998, this report was a prelude to the formulation of the project METACOG (Methodology of design to total cost objective, part of the French national PROSPER project), which aims to define these metrics.

Third, a horizon evolution has also implied many consequences in the methods and factors for cost evaluation.

Whereas since its beginnings, the calculation of costs is used to improve knowledge of the products costs in production, its application gradually moved towards the future products cost. This change of object does not come out from developments in the technology of costs calculation but from a change in the comprehension and modelling of costs. Then the consideration of the life cycle targets and factors seems an extension, on a longer horizon, of the movement started in the seventies on the costs management tools. Their construction is contingent, taking into account of the economic, the structure and the operating environment of the company.

COST EVALUATION

First of all, it is essential to clearly define the basic notions of cost management and their evolutions. The old way to consider the selling price was calculated according to the cost price plus the margin. But today, the selling price is market driven, depending on the fee, which the customer is ready to pay according to the functions, and the services expected. Consequently, the margin is not used to calculate the selling price but it results from it, equal to the selling price minus the cost price. Consequently, the selling value and the margin must be the objectives, and then an "objective maximum cost price", known as "objective cost" can be evaluated as an objectiveselling price minus the objective margin. This is this concept which will drive design services during their study phase.

But, it still remains some problems depending on the concept of a product complete cost price and one the margin applied to find the selling price. So cost management methods tried to deal with all this problems [START_REF] Brodier | La dictature des prix de revient-Harvard-L'Expansion -1990[END_REF][START_REF] Perrin | Cohérence, pertinence et évaluation économique des activités de conception[END_REF]. For example, the respect of the product cost is the base of the target costing methods' and Activity Based Costing (you have to aim an objective target cost and then make correspond the final product cost after what you can measure the gap between the effective and the objective cost). The respect of the budgets, mainly the studies' budgets, is the second key factor for success at the financial level. Formerly, the costs used to take into account a majority of direct costs (often about 70%), i.e. easily affected with the products. The costs not directly easily affected with the products could be the subject of total distributions (the choice of the scale little influenced the result). But now, the proportions between direct to indirect costs are reversed (see figure 1). In addition, the early phases of the product design decisions' impose more than 85% of the final cost, witch means that the early mistakes or miss evaluations affect in a very large way the costs (see figure 2). The curve above shows the evolution of the expenses really engaged by the company. The main effort for cost management should be focus on the first step of the product life cycle. At the end of the studies, approximately 85% of the complete cost of the program is fixed. Statistically, the share of responsibility in the establishment for the costs is 85% at the engineering and design department, 10% at the office "methods industrialization" and approximately 5 % with manufacture itself and the service purchase.

Figure 2: Cost evolution during a project [START_REF] Alcouffe | Standardisation et évaluation des activités de conception dans le secteur aérospatial[END_REF] As indicates it the following figure, more the product's definition advances, less the modifications are easy and the costs increasingly expensive. There is thus an obvious economic interest to concentrate on the search for a product optimisation earlier as possible in the process, the potential saves are significant and the committed costs weak.

Thus, the cost of a product relies on the engineering and design department. Then, the design choices, inexpensive in terms of resources consumption appear in the manufacturing costs when it becomes very hard and expensive to carry out modifications (Bellut 2002[START_REF] Mevellec | Le coût global, nouvelle frontière du calcul de coûts[END_REF].

So, we tried to point out that cost management is hard to handle due to the lack of efficient tools or methods and the very strong effects of decisions in the earlier phases of the product development.

APPLICATION CASE STUDY

Based on these facts, we developed, with SMC CO-LOMBIER FONTAINE company, a dynamic method balancing, at the quotation level, the effects of a production on the economical results of the so-ciety. This method integrates the enterprise processes in order to manage from the customer requests to the parts to be delivered. The value added unit, chosen for measuring the performance is the time for each step of the product lifecycle in the enterprise. This method follows the product life cycle in the enterprise and is implemented thanks to a collaborative and concurrent engineering approach between all the actors.

SMC COLOMBIER FONTAINE is a French industrial company in the AFE METAL group. The core process is steel sand casting used to manufacture primary parts. They manufacture about 1000 references per year and design an average of 15 new tooling per month.

At the beginning of this work (1999), two factors led the manager develop a complete numerical technology and traceability supporting the product lifecycle in the enterprise (Bernard & al. 2002-a and b):

First the time (then the cost) needed for a new product's industrialisation takes from 20 to 40 hours to complete a CAD study (model the part, the master pattern, the pattern-plates, the cluster and simulate the fill up and the solidification). Furthermore, the same technicians answer to quotations asks, design the tooling, simulate and optimise the complexes parts. Then, the method's service cannot generalize this complete study to all the parts. Furthermore, all these indirect costs took a bigger place in the enterprise financial results due to the important mix of product.

Secondly, the selling price was completely disconnected from the real value added by the enterprise, without taking into account the exact costs of the tooling developments (cores and core boxes, the master patterns…). Finally, the technician globally evaluated the complexity of the part; the price was then calculated on the base of its weight and a ratio depending on the complexity. Production So, in order to reduce the "time to market" (and optimise the efficiency of the tooling office) and to exactly master the costs of the parts, SMC developed a complete numerical technology to support his improvements. This is based on a shared CAD/CAM data and environment, supported by SolidWorks application (see figure 3), and developed for each view required during the PLM in the enterprise (see. figure 4): -design the part at the quotation level (initial model), -enriched with the cast rules (skins, machining stock allowance…), -tooling design (cluster CAD model, master pat-tern…) and manufacturing (CAM tooling model and NC files), -process validation and optimisation (fill up and solidification simulations), -moulds and parts control... This collaborative approach allowed on the one hand a drastic reduction of time to market. Indeed, the old way of development took nearly six weeks before validating the parts prototype whereas a complete integrated solution allow in two weeks and half this validation with the adequate tools (see figure 5) presenting the evolution of the time needed for the several steps of the industrialisation development: study, CAM, wait of pattern maker availability, model machining, master pattern elaboration and prototype validation).

Figure5: Time to process validation delay On the other hand, the quotation service can now reply efficiently at each new request with a complete optimised study and a perfect knowledge of the exact time required for the study, the validation and manufacturing of the part. The enterprise processes are completely described in a knowledge database. The time factors, related to the various activities and operations during the product life cycle (time needed for a study, for tooling manufacturing, for the rate of production and so on), are closely looped in order to keep a coherency between the total time evaluation and the exact times spent. This time evaluation is given through a particular Excel's sheet application developed in collaboration with the head director of the enterprise (presented on figure 6) linked with all the processes indicators. This allows estimating the impact on the production capacities and the financial results of the company. This is a very efficient method of capitalizing in detail the characteristic factors of each of the product realization elementary processes.

Figure 6: Economical impact estimations So, when the quotation technician gives a selling price for a new part to be delivered, he sells the time spent for its manufacture with respect to the definition of the characteristic factors of the processes (in addition with the direct costs like raw material for example). It is to be noticed that, with regard to the charge of the process validation (presented above), the time is up to now evaluated and not exactly measured.

In addition, the financial goals of the enterprise, in term of turnover and profit, give a cost rate objective per hour of work, which balances the budget. The technician immediately knows whether, or not, this order will be benefit for the enterprise. Two different kinds of orders can be identified: the "contributive" ones (that cover both fix and variable costs) or the "marginal" ones. It would be easier to only take into consideration the first ones but the production lines should work at their maximum capacities in order to keep a production economic cost. So, some marginal orders are included in the production scheduling to maintain a manufacturing activity for social and economical reasons.

By fulfilling the form, linked with the CAO information's and the manufacturing process (the numerical shared technology starts at this first initial level), the result given by the form is an estimated selling price relying on the time estimated and the objective cost rate. Depending on the final selling price, the order is seen as contributive or marginal. Consequently, each quotation technician had to manage his own impact on the enterprise, taking into account of the effects of his sold parts. The Excel application helps this management with an automatic drawing of curves giving the relative position of all the orders engaged by the technician for the ongoing year and the objective cost rate per hour to adjust the price strategy of the quotations (cf. Figure 7). The two main outputs of this research are on one hand the necessity of the definition of effective cost indicators (direct or indirect ones) in order to be able to qualify and quantify the relationships between the process characteristics and their impact on the results of the company. On the other hand, it is of major interest to propose a complete numerical and methodological integration based on a PLM and CE way of thinking. The information system scenarios have been developed in order to be able to deploy a complete closed-loop integrated and collaborative structure and processes.

In parallel, a permanent study of the processes and of the different cost effects allows defining in details the major relationships between the company activity and the value/cost characterization.

Our current research are oriented to the improvement of use and integration of pricing and costing estimating in order to be able to consider economical factors as performance objectives at the same level that all technical and organisational ones. This corresponds to a very present demand from industry mainly due to shorter time-to-market and to the new virtual enterprise structures.

Figure 1 :

 1 Figure 1: Direct and indirect costs evolution

  Concurrent Engineering 2003: the Vision for the Future Generation in Research and Applications, ISBN 90 5809 623 8, p.817-822. Title Volume 1 -Enhanced interoperable systems, J.Cha et al. (eds) © 2003 Swets & Zeitlinger, Lisse.

Figure 3 :

 3 Figure 3: Complete numerical technology[START_REF] Bernard | Quotation for the value added assesment during product develeopment and production processes[END_REF]

Figure 4 :

 4 Figure 4: Place of the quotation tool in the numerical loop

  Concurrent Engineering 2003: the Vision for the Future Generation in Research and Applications, ISBN 90 5809 623 8, p.817-822. Title Volume 1 -Enhanced interoperable systems, J.Cha et al. (eds) © 2003 Swets & Zeitlinger, Lisse.

Figure 7 :

 7 Figure 7: Time to process validation delay

ACKNOWLEDGEMENTS

The authors would like to thank for their very important contribution to this work SMC Colombiers Fontaine company and more especially MR J.C. Delplace, PhD student, and Mr S. Gabriel, General director of the company and R&D manager of AFE group.


Alain Bernard

Nicolas Perry

Jean-Charles Delplace

Serge Gabriel

QUOTATION FOR THE VALUE ADDED ASSESSMENT DURING PRODUCT DEVELOPMENT AND PRODUCTION PROCESSES

Keywords: design and production, cost driving system, numerical traceability

whether they are published or not. The documents may come

INTRODUCTION

SMC COLOMBIER FONTAINE is a company in the AFE METAL group, which uses a sand casting process to manufacture steel primary parts. To reduce the "time to market", primary part producers need to reduce the time and cost of the industrialisation process. These factors, in addition to the global goal of improving process performance levels, brought SMC to develop numerical technologies and traceability from quotation to part delivery [START_REF] Bernard | CAD and rapid manufacturing techniques for design optimisation in sand casting foundry[END_REF].

Nowadays, these improvements are incorporated into company culture. The next step in reducing the time and cost of the production process is to introduce a complete methodology of use and experience feedback of these new models and methods.

To be able to generalise this approach, a CAD methodology imposes and thus becomes a step in the industrialisation process. The amount of improvements engendered by the numerical technologies largely justifies the time investment made to obtain a numerical definition of all the different elements in the sand casting process [START_REF] Bernard | Optimisation of complete design process for sand casting foundry[END_REF].

The objective of our approach is to optimise the product and its production process by generating a complete numerical reference, through the integration of quotation, CAD, simulation, new manufacturing technologies and effective production processes. This approach is the base of the integration of the three decision levels of a company, strategic, tactic and operational (Figure 1). At the strategic level, the quotation elaboration is directly linked to the economical impact of each production. At the tactic level and due to a complete numerical integration, quotation indicators are used to configure the processes parameters based on the CAD definitions of parts and tools. At the operational level, the This approach is the base of the integration of the three decision levels of a company, strategic, tactic and operational. At the strategic level, the quotation elaboration is directly linked to the economical impact of each production. At the tactic level and due to a complete numerical integration, quotation indicators are used to configure the processes parameters based on the CAD definitions of parts and tools. At the operational level, the processes are monitored and a complete numerical traceability and control is used in order to provide feedback of the value chain costs from design and production to the quotation application. This paper presents the key factors of the approach's efficiency.

Quotation for the value added ASSESSMENT during product development and production processes

INDUSTRIAL CONTEXT OF THE PROJECT

SMC has a wide product range with 7 different automatic casting lines, about 1000 references per year and an average of 15 new tooling per month. Currently, during the sand casting process it takes from 20 to 40 hours to complete a CAD study; that is to say, model the part, the master pattern, the pattern-plates, the cluster and simulate the fill up and the solidification. At this time, generalizing this kind of study to all parts is possible due to the introduction of the new CAD methodology in the technical office. For this reason, toolmaker suppliers can use different moulding techniques to manufacture the pattern plates from the CAD models of the parts, but mainly from the CAD models of the tools. In this approach, the simulation's accuracy is hindered by the random repeatability associated with the tooling. All clusters are simula ted and thus the results guide the designers to improve the rules supporting tooling definition. Because of the adequacy of the CAD model and the real cluster geometry, reliable simulation results are obtained. It optimises overall product industrialisation time and cost by reducing the iterations needed to perfect the serial production design. The use of a complete design methodology for both casting parts and tooling is one of the key factors of the project for the validation of a numerical engineering in sand casting. The performance factors give the fundamental orientations for the CAD design of parts and tooling and are completely process dependant. These factors are linked to the economical indicators that characterise the influence of a production on the economical balance of the company. The main difficulty is to have a dynamic interaction between strategic decision indicators and effective industrial processes behaviour (time, quality).

POSITION OF THE PROB LEM

The objective is to define on one hand, a complete numerical reference model of parts and tools and on the other hand, enterprise processes driven by costs estimations. In such a context, a design methodology for casting parts and tooling is indispensable in order to increase the efficiency of the design phase (decreasing time and cots) and to improve the quality control of the complete processes.

So, our approach refers to a proposition of a knowledge-based engineering approach [3][4][5] and also to a methodology for integrating economic criteria in design and production decisions [START_REF] Tornberg | Activity-based costing and process modeling f or cost-conscious product design: A case study in a manufacturing company[END_REF].

A major problem of cost estimation comes from the increasing ratio of indirect cost in the global price of the part (mainly due to the evolutions of the market and the process cycle). Several analytics methods try to evaluate the exact price to be applied.

First, cost accounting gives no efficient solution to this problematic (mainly due to the lack of connections between the repartition keys of fixed costs and their real consumption).

Secondly, the ABC method (Activity Based Costing) focuses on cost drivers from the design to the delivery phase of the part cycle process [START_REF] Gunasekaranh | Activity based costing in small and medium enterprises[END_REF][8] [START_REF] Mevellec | Activity-Based Costing: a Call for a French Approach[END_REF]. Consequently, the cost estimation becomes more relevant, but this method is long to adjust and can be complex (each activity should be evaluate and associate with a cost driver).

Thirdly, the Value Added Unit method [10][11] has the same vision than ABC, but uses a single cost driver unit for all the steps. Its objective consists in determining the profitability of each sale. This becomes a very efficient tool to manage the effect of a part on the global economic balance of the enterprise. Our approach refers to this third method.

The cost definition is linked to intrinsic parameters of the product and time key-factors of enterprise processes. For example, the design phase is considered as generating uncompressible costs and is one of the heavier indirect charges for the product. So one of the main interests of our approach is to increase the efficiency of the technicians' work, that is to say, to increase the number of CAD definitions for a given period of time (increasing the productivity of the design phase).

Due to these considerations, the proposed approach can be considered as a valuable new approach for efficient cost-driven of enterprise processes. Quotation allows characterizing both a cost for a given batch of parts and the complete choices of the key factors of the industrial processes that will be used to produce this batch of parts.

The second very important point concerns the fact that all the processes are closed-loop monitored in order to readjust the quotation indicators depending on realistic time capabilities of the processes. Up to now, this updating data is manual but should be automated.

DEFINITION OF THE PR OPOSED APPROACH

To be able to validate these concepts, SMC decided to act on different areas of the process' cycle of the casting products. This cycle is divided in three main steps: quotation, industrialization and production.

Quotation consists in evaluating the possibility to have benefit in realizing the production of a given part.

When this first step is validated, industrialization allows defining the raw (casting) part, the cluster and simulates the process parameters in order to validate the CAD definitions.

Then the production planning system takes into account the production order and defines the best repartition of the parts' flow on the automatic casting lines.

The main originality of our approach is that these three phases are completely connected and integrated to quotation indicators and the enterprise processes are driven coherently depending on these indicators.

QUOTATION CONTEXT AND OBJECTIVES

The industrial context is characterized by a large variety of parts. This mix-product has administrative consequences (large number of quotations, of commercial propositions, of client communications) and also industrial consequences (obligation to increase the design productivity, to improve the process efficiency, to decrease the scrap ratio, to monitor the real capability of the resources).

All these services and means have consequent effects on the costs. But, generally the market drives the price and the companies hardly integrate these costs for the parts. This point shows the importance of a very efficient costs management and the need of closed-loop interaction between quotation indicators' (that determine the processes parameters and characteristics) and the effective processes that are used for production.

Costs can be considered in two categories: fixed costs (that depends on salaries and enterprise structure) and variable costs (related to the number of

Alain Bernard(1), Nicolas Perry(1), Jean-Charles Delplace(2),

Serge Gabriel [START_REF] Bernard | Optimisation of complete design process for sand casting foundry[END_REF] manufactured parts, to the consumable used in the production processes like materials, energy, etc…). According to the cost management method presented paragraph 3, each production can be considered as contributive (that covers both fixed and variable costs) or marginal (if it does not cover). The basic unit used for the computation is the time spent by activity. The economic objectives of the enterprise for the current year give an average's cost per hour for the global balance. With these data the quotation service can quickly decide to take or not a command, depending on the negotiation's results with the client and the corresponding price decided. The interest for the company is to have a maximum of contributive productions but some marginal ones are necessary in order to obtain the volume of production, a regulation of the mix product and the production scheduling (the company has to produce every day).

The main interest of our approach is to exploit the numerical reference model from this management strategic level. This level is based on three applicative layers, the quotation, the industrial and commercial planning and the dynamic stabilization point. The first level is necessary in order to evaluate the kind of production (contributive or not) and to measure the impact of such a production on the exploitation account. One should remind that the objective is not to determine the price of the production but to evaluate the contribution of the production by computing the corresponding hour's rate (which corresponds to the sell price of a production hour without consumables). This value can be compared to the ratio that has been determined as the base for a positive financial result of the company.

Of course, the quotation phase is based on a knowledge database that contains the major variables characterizing the enterprise processes with an Excel interface. This is a dynamic tool through the consequences immediate visualization of one of these variables modification (value of the hour rate). These functionalities allow mastering the economical characteristics of the manufacturing processes. Due to the complete integration with technical indicators of the processes, quotation step is possible in less than ten minutes and, when considering the past productions and when comparing the effective results with the previsions, the precision is less than 5%. Then the industrial and commercial plan indicates the contribution of the production to the enterprise result thanks to the comparison with the dynamic stabilization point.

The numerical reference model used for the quotation computation is also used for design and production stages. All the information is stored in the same knowledge database and is accessible for all the process cycle applications (from quotation to delivery).

Quotation for the value added ASSESSMENT during product development and production processes

PARTS AND TOOLING DESIGN METHODOLOGY

The second step of the numerical chain is the design of parts and tooling. This stage is based on a design methodology that allows validating the productions processes by taking into account the corresponding constraints.

At the beginning (Figure 2), the traditional manufacturing of a part was based on the definition of a 2D drawing and to manual fabrication of the tooling. Numerical integration that allows using the knowledge database has been developed and the technicians of the design office elaborate and validate each of the intermediately objects of design for parts and tooling. They also validate the production processes by using simulation software for temperature and metallurgical studies.

On a practical and methodological point of view, technicians use personal computers (laptops) which contain for each study simultaneously the quotation application and data, the knowledge database and the CAD application. Particular developments, based on the design methodology, have been implemented and each technician can validate coherently step-by-step the design process and the different mode ls created for the parts and the tools. This is possible due to the fact that each production sub process (mainly tooling geometry control and also core placement control) is closed loop. For example, the use of this unique referential model, based on what has been decided during quotation phase, allow controlling presence of cores and geometry and damages of joining surfaces. This last point is very important due to an important proportion of manual tasks dedicated to the suppression of exes of material (defaults on joining surfaces).

The decided process plan is traced using analogical codes. The operators validate the productions using a STL viewer that presents graphically the 3D graphical model of the parts. Then this is possible to evaluate the exact impacts of each production and let dynamically to re-actualize the economical factors of quotation indicators.

At present, SMC Colombier Fontaine company economical results are very positive due to this complete numerical integration from quotation to parts delivery. All the elementary processes (design and production) are completely closed loops and allow obtaining a global coherency for the mastering of the overall industrial activity at all company levels.

SYNTHESIS OF THE PROPOSED APPROACH

The following picture (figure 4) summarizes the complete process based on the quotation attributes and on the common, collective and distributive database that represents and memorizes the complete data related to each production. The time, from quotation to parts' delivery, represents in fact the main periods of the life-cycle of the casting parts. Sometime SMC asks subcontractors for part machining in order to deliver to the client finished parts, ready for assembly. During all these steps, data are memorized. These data are necessary and sufficient in order to be able to reproduce the same process in the future. These data, based on product models [12] for life-cycle [START_REF] Brissaud | Product models for life-cycle[END_REF], contribute to the increasing of the knowledge related to the company processes. These models are the key factors of the complete methodology proposed in this project. Serge Gabriel(2) For each industrial study, the completion of the data is tested by the existence of wanted and effectively realized value chain parameters for all the industrial processes. The measure of the differences allows re-actualizing the quotation parameters. These differences are mainly related to quality and time. Concerning the design phase, time has been reduced due to the use of the complete methodology and to the structure of the database for all the parts and tools components (logical dependency between the part, the cores and the corresponding core-boxes, link between the part, the parting line and the corresponding geometry on the patterns and the tools, etc…).

CONCLUSIONS AND PERSPECTIVES

With the accomplishment of this study, SMC has introduced a complete economical and numerical integration. After the economical, numerical and technical validations, the payback highlights a very significant progress for costs, which confirms the successful introduction of knowledge-based elementary decision processes in the company. The design methodology proposed in this project reduces part design time and the CAD hourly rate. The design costs have been reduced enough thanks to the generalisation of the numerical models for tooling design. All of these improvements should facilitate SMC's generalised implementation of numerical integration and help them make their offer, in the field of sand casting, more competitive.

Figure 1 .

 1 Figure 1. Main steps of the proposed approach

7

 7

Figure 2 .

 2 Figure 2. Conventional process

Figure 4 .

 4 Figure 4. Complete industrial process based on two common references (quotation and collective database)

Alain Bernard [START_REF] Bernard | CAD and rapid manufacturing techniques for design optimisation in sand casting foundry[END_REF], Nicolas Perry [START_REF] Bernard | CAD and rapid manufacturing techniques for design optimisation in sand casting foundry[END_REF], Jean-Charles Delplace [START_REF] Bernard | Optimisation of complete design process for sand casting foundry[END_REF], Serge Gabriel [START_REF] Bernard | Optimisation of complete design process for sand casting foundry[END_REF] core boxes) is less than one week. As a result, cost has been decreased by a factor two. All the numerical information needed for the production phase are automatically generated (tooling quality and topology, tooling manufacturing processes, production plan and parameters, casting parts and tooling references for traceability, numerical models of the cluster for the automatic cutting of the parts from the cluster, for the quality control of the tooling, for the quality control of the parts at the end of the production process). All the hypothesis concerning the production configuration are managed and closed-loop by the product planning application, based on the same knowledge database (Figure 3).

When the numerical simulation and validation of the process has been proceeded, all the technical and temporal data are sent to the production planning application in order to execute the production phase.

PRODUCTION NUMERICAL TRACEABILITY

The first phase of the manufacturing process is the manufacturing of few parts before the mass production phase. The benefit of such pre-production (good geometry, good material characteristics, good process) gives very important information about tooling geometry and capability, about the mass of the clusters and of the parts, about the cycle time, about the global robustness of the production process. This means that in priority the


Nicolas Perry
email: nicolas.perry@irccyn.ec-nantes.fr

Magali Mauchand

Alain Bernard
email: alain.bernard@irccyn.ec-nantes.fr

COSTS MODELS IN DESIGN AND MANUFACTURING OF SAND CASTING PRODUCTS

Keywords: cost management, enterprise -product -cost modelling, cost entity

In the early phases of the product life cycle, the costs controls became a major decision tool in the competitiveness of the companies due to the world competition. After defining the problems related to this control difficulties, we will present an approach using a concept of cost entity related to the design and realization activities of the product. We will try to apply this approach to the fields of the sand casting foundry. This work will highlight the enterprise modelling difficulties (limits of a global cost modelling) and some specifics limitations of the tool used for this development. Finally we will discuss on the limits of a generic approach.

Introduction

In the early Seventies, studies in the United Kingdom and in the United States highlight the strategic role of the design activities. The conclusions lead both companies and authorities towards new approaches in order to improve the economic performances of companies. At the end of the Eighties, the paramount role of the quality in the design was reinforced in the United States by the Made-in-America report from the MIT "Commission on the Productivity". The Improving Engineering Design confirmed these conclusions in 1991: Designing for Competitive Advantage report, from the United State Nation Research Council "Engineering Design Theory and Methodology". As resumed by Perrin [START_REF] Perrin | Cohérence, pertinence et évaluation économique des activités de conception[END_REF], the design phase is the key factor of the product development process. The ability to product new products with a high quality, a low cost and witch fit with the customer requests is fundamental to improve the nation competitiveness. Consequently, the costs (and cost management from the early design to the end delivery) become as important as the other technical requests.

Due to the global market and the worldwide competition, reactivity and agility are the only way to maintain the enterprise competitiveness. This can be characterized by the ability to change its products and/or processes in very short times and at minimal cost. The cost control, at the early step of design, becomes a key factor of success, since this phase fixes an average up to 70 to 80% of the end product costs (depending on the kind of production).

Moreover, the costs distribution (respectively direct and non direct) is changing: more time and services are dedicated to the studies for smaller products batches and shorter product life. The former fees sharing-out methods, the analytic or analogical cost-accounting methods, no longer give efficient results. Then, thanks to studies from CAM-I (Computer Aided Manufacturing-International) and authors like Johnson and Kaplan, the increasing gap between "traditional methods" of cost estimation and the new management requirements were highlighted.

All these works lead to new approaches integrating the complete cost and spread accounting methods based on the enterprise activities (ABC for instance). French economist, G.Perrin [START_REF] Perrin | Prix de revient et contrôle de gestion par la méthode GP[END_REF], since the Sixties, also developed a method based on one single cost-inductors through all the steps of the product development process (Added Value Unit method). We implemented such a costing management in a French sand casting foundry in order to allow a several-level management, based on indicators linked to the exact costs of the product to be delivered [START_REF] Bernard | Optimization of complete design process for sand casting foundry[END_REF][START_REF] Perry | CE : the Vision for the future generation in research and applications[END_REF]. During this PHD thesis we validated the concepts but also the methodology required for a complete numerical traceability.

The work that will be presented in this paper concerns this former study and uses a concept called cost entity [START_REF] Mida | L'approche entité coût pour l'estimation des coûts en production mécanique[END_REF]. It includes several concepts: the cost inductors from the activity based accounting methods, the feature from the CAD and the homogeneity from the analytical cost accounting. Consequently, in order to define a cost entity, it is necessary to fill in several attributes linking technical and economical variables. The product model uses the concept of manufacturing feature. The cost are evaluated on the base of specific knowledge and reasoning models with the tool "Cost Advantage", giving information on costs to the CAD model. This is adding a cost semantic level to the CAD model. This models (called costgramme) put the expertise of the manufacturing cost available to the designer. Some models, dedicated to the sand casting production of primary parts, were created with the wish to evaluate a meta-model that could be deployed in all the sand casting industries. Thus, the goals of this study are, on the one hand, to create the more generic as possible model related to the sand casting job, and on the other hand, to determine how they are transposable from a company to another (or from a production line to another…). So we will have to define and discuss which are the limits of the concepts from the triptych product/process/cost, and what level of detail is necessary to implement the methodology in most of the industrial environment.

This study is realized in collaboration with Cognition Europe, software developer of the tool Cost Advantage, and based on an industrial experimentation in the already-mentioned SMC Colombier Fontaine casting enterprise.

Value and cost management

The concept of cost or value strongly evolved with the context. Today, the selling price depends on the price the customer is ready to pay according to the value that it appreciates. Consequently, the margin is not used to calculate the selling price, it results from it. The selling margin and price must be defined beforehand; they determine an "objective maximum cost", known as "objective cost".

According to Perrin the indicators relating to the costs are mainly to be classified among the results' indicators [START_REF] Perrin | Cohérence, pertinence et évaluation économique des activités de conception[END_REF]. The two criteria considered are on one side the cost of the product and on the other side the respect of the budget:

-the respect of the product cost is proposed within the framework of the development of the target costing methods (management by cost-target) and ABC (Activity Based Costing). The idea is to fix a target cost as an objective to which one must make correspond the cost of the product. The indicator then used, is the relationship between the effective and the objective product cost, -the respect of the budgets, in particular of the studies' budgets, is the second element to be taken into account at the financial level. The indicator is then naturally the ratio between the exceeding and the initially fixed budget.

The contextual industrial evolutions change the nature of the costs in the company. Formerly, the final costs included a large majority of direct costs (often about 70%), i.e. directly assigned to the products (labour or raw material). The other costs could be the subject of global distributions; the choice of the scale hardly influenced the result. The method of the cost accounting with indirect expenses shared through a fixed percentage, can be admitted as long as their proportion is not too big. But the proportions are reversed, the direct costs do not constitute often any more that 30 % of the total cost. Not only the indirect expenses, according to odd sharing keys, create an arbitrary factor in the calculation of the costs, but it make the control difficult. These two concerns gave place to many researches that ended up in deeply modifying the systems of costs evaluation.

Let us analyse the product life cycle and the impact of decisions in term of generated costs. The early phase of design implies between 70 and 85% of the product cost and, at the end of the detailed design the margin on the final cost is thus very limited (cf. Fig 1). Contrary, the evolution of the costs really engaged by the company are very limited in these upstream phases. However, it is there that the control of the costs should be really exerted.

Consequently, the more the product is defined, the less the cost reduction is easy. The modification becomes increasingly expensive. There is thus an obvious economic interest to have a product optimisation at the early step of the process. The profits potentialities are significant and the committed costs weak. The design choices, inexpensive in terms of resources consumption can be very expensive in production, when it becomes extremely difficult to carry out modifications [START_REF] Bellut | Estimer le coût d'un projet[END_REF][START_REF] Mevellec | Le coût global, nouvelle frontière du calcul de coûts[END_REF].

Fig.1 : Cost evolution during the PLM [6] 3 Design to Cost

The design to cost can be defined as a principle of action aiming the establishment of rigorous objectives. It allows compromises between performance and cost [START_REF] Delafollie | Analyse de la Valeur[END_REF][START_REF] Petitdemange | La maîtrise de la valeur » La gestion de projet et l'ingénierie simultanée -Paris-La Défense[END_REF]. The "cost" constraint becomes capital and this data should be managed on the same level than technical performances. Then the cost objectives become constraints and the technical performances, variables.

The interest to integrate the cost management at the design phase is shared either by the customer and the seller since it makes it possible to control the development according to the exact needs for the future users (it incites in the search of new ideas required by the economic constraints), in addition, it makes possible to prepare and organize its production very early and to better control its margin [START_REF] Giannopoulos | Embedded systems software cost estimating within the concurrent engineering environment[END_REF].

This method of design takes again the steps of activities or tasks with a focus on the costs limits. This led to an extension of the design time due to the successive iterations needed to agree on the solutions after negotiation (technical or economic). This leads to cross the functions within the company and can be used jointly with methods of costs analysis like ABC. This also allows a very thorough analysis of the product functions linked to its costs [START_REF] Kieffer | Méthodes du pilotage des systèmes de production[END_REF].

One can however point out that the design phase is longer. But, the debugging step (preproduction) is no longer disturbed by modifications as it occurs in a traditional step. We then accept in fact "to waste" time with the design phase, therefore with the quasi-certainty to regain it downstream before the delivery date.

The Cost Entity concept and the modelling logic

The aim of our study is to sharply manage the costs (direct and indirect) during the production of sand casting parts. As illustrated previously, it is imperative to give a tool to the engineers of the engineering and design department in order to help them to control the costs of the parts design. In collaboration with the company Cognition Europe, and on the basis of the tool Cost Advantage, we work on the costs models to apply in the case of the steel sands casting parts. We are based on a preceding work, proposing an integrated approach for the sand foundry, realized within the framework of a thesis in partnership with SMC Colombier Fontaine (France) of group AFE Metal [START_REF] Perrin | Prix de revient et contrôle de gestion par la méthode GP[END_REF]. This work allowed formalizing the base of knowledge trade necessary to the control of the product life cycle in a foundry company. In addition, we validated an approach, a methodology and a deployment leading to ensure an exact knowledge of the parts costs and their impact on the output of the company [START_REF] Perry | CE : the Vision for the future generation in research and applications[END_REF].

Let us start with the concept of cost entity and context, which are our modelling bases.

Costs Entities

A Cost Entity is a grouping of costs associated with the resources consumed by an activity. The general condition is due to the homogeneity of the resources, which makes it possible to associate a single inductor: the entity cost [START_REF] Mida | L'approche entité coût pour l'estimation des coûts en production mécanique[END_REF]. The model allows expertise formalisation, knowledge capitalisation and to have, at the early design phase, some information about the production step. Moreover, it helps the communication between all collaborators during the product life cycle.

Contexts

The contexts specify defined entities in three levels in our model. The first is defined in a process level, the second on a material level and the last is directly related to the feature. This context is a cross between a process, a material and a feature, connected to an environment (cf. Fig. 2).

Fig.2 : Sand casting Modelling

Sand casting modelling

Based on this analysis we created a generic model using Cost Advantage Software. The first step closely defines the production process dedicated to this industry. The master parameters acting upon the product cost must be identified in order to enrich the cost semantic of the model.

The generic approach quickly highlights the problems of the contexts characteristics. How to define a significant cost for the part and with which level of detail in order to be generic?

We will not answer this question, but we will present the paths or solutions we used.

First, let us describe the sand casting organisation through the part life cycle in the enterprise. This model is based on the SMC Colombier Fontaine foundry (France), from AFE Metal group. We will reduce our cost model to the primary parts through its life cycle in the enterprise and focus on the production phase, from the sand elaboration, the tooling machining and the parts perfecting.

Step induced by the use of Cost Advantage

Figure 3 presents a functional view of the process with the compound (raw material, tooling) and the elements needed to manufacture a part linked with the major indicators dealing with the final cost (loss, scrap ratio, production rate).

4: Cost Advantage modelling example, at the assembly level

Figure 4 represents a transposition under the concepts of Cost Advantage of this model gathering the three levels of entities defined in the software. To illustrate this, for example, the mould, the tooling and the cores are components required to carry out the assembly named moulding by the operation (feature) of remould. It is thus necessary to define the final part, to carry out the two assemblies, which are the moulding then the casting.

In term of model design, the functional view identifies the assemblies needed, it is then necessary to define the components and choose and define the related operations. An ascending step must be practiced, starting with the components up to the definition of the assemblies. The costs calculation is presented in figure 5 and the structure of the implemented data in figure 6. Calculations are simply taking into account volumes of material, rates of production, losses and the machine and labour costs. To say nothing about the difficulty in knowing the exact parameters, the problems we met were model organization, more than process modelling.

Pi

Fig.5: Process cost structure sample

The rules of calculation then implemented will make possible to the future user to inform only the relevant data about its study. Indeed, only the operational process, rates, dimensions, numbers of cores (etc.) will be required (or deduced directly in a CAD software) to allow an automatic calculation of the cost of the part according to its particular characteristics.

Discussion

The principal remark on this model, implemented with Cost Advantage platform, comes to that it doesn't integrate the global aspect of the costs management. For instance, the indirect share due to the development and the design of the tools (master pattern, cores boxes…) isn't taken in account.

But let us keep in mind the framework of use of such a tool: to help the designer to achieve a cost objective related to expected technical functions. He can then propose design modifications (joint section, cores, quality…) or process (number of parts in the mould…) to achieve its goal. Moreover, when the whole partners validate this design, the parameters costs are fixed (in agreement or not with the objective laid down initially), the cost is well known and will not be any more a consequence of later decisions.

During this work we have identified a principal difficulty, which for this modelling impact the multiplicity of the elements on the availability for their characterization and for their organization. Even if the manufacturing sand casting process seems simple, it uses many components (alloy, cores, mould…), and we limited the definition in term of model refinement since each one of these components could be the subject of a finer modelling. We tried to choose this limitation in order to represent the general process without going closer into enterprise specificities. For example, the cores or fusion process of realization are not completely defined since depending on the machines, uses and other specificities of the workshop. In fact this remark is shareable for all the components entering into the realization of the finished part. But we think that we defined a basic minimal skeleton, transposable from one company to another using the sand casting process.

Conclusion

To conclude on this work, we started to apprehend logic of cost oriented modelling through a tool using the concept of cost entity. In order to ensure a generic aspect of our work, we deliberately limited the details of the operations, components and assemblies. Indeed, the development of these elements takes into account many parameters that it seemed to us initially overflowing to define.

We thus defined a structure that we think minimal, as well as indicators necessary to evaluate the whole costs without the indirect part. The two next steps of this study are in the first hand among other sand casting companies, to apply this modelling, configure the model with the existing processes and informing the exact values of the indicators. But also in the other hand, to calibrate the model and the results on real studies already done. These two last steps allow comparing the effectiveness of the various companies and could be used as Benchmark. A foreseeable difficulty is the possibility of reaching this information. Moreover, these factors are often managed in a total cost accounting. As a result, the efficient indicators may be sunk in a not very transparent accounting system or may be aggregated with not relevant others.

The other significant continuation to give to this work is the taking into account of the global costs mainly related to the indirect shares (structural). Our introduction puts forward the lack of management of these aspects and our first approach did not give place to a better control of these factors. However the work is done and the workers must be paid (designer, maintenance, buyers, logistics…) even if their work is not as well managed through a cost management system. A better specification (by the means of indicators, of metric) of the tools design phases, tools lifespan, etc. could integrate a real cost of the complete series. The question of the relevance of the tool used for this type of approach arises then. Some solutions come from the use of single or very limited number of cost inductors such as the time and they define a minimal global enterprise cost per hour to balance its financial objectives. Such an approach allow a multi-level management of the parts impact and give real time information to asses the enterprise objectives and manage strategies and operational decisions.

Fig. 3 :

 3 Fig.3: Process view of a sand casting production cycle

Fig. 6 :

 6 Fig.6: Structure of data with Cost Advantage


MD Fanny Mochel
email: fanny.mochel@upmc.fr

Sandrine Duteil

Cécilia Marelli

Céline Jauffret

Agnès Barles

Janette Holm

Lawrence Sweetman

Jean-François Benoist

Daniel Rabier

Pierre G Carlier

Alexandra Durr

Dietary therapy in Huntington disease 1 Dietary anaplerotic therapy improves peripheral tissue energy metabolism in patients with Huntington disease

Keywords:

We previously identified a systemic metabolic defect associated with early weight loss in patients with Huntington disease (HD) suggesting a lack of substrates for the Krebs cycle. Dietary anaplerotic therapy with triheptanoin is used in clinical trials to promote energy production in patients with peripheral and brain Krebs cycle deficit, as its metabolites -C5 ketone bodiescross the blood brain barrier. We conducted a short-term clinical trial in six HD patients (UHDRS= 33 13, 15-49) to monitor the tolerability of triheptanoin.

We also assessed peripheral markers of short-term efficacy that were shown to be altered in early stages of HD, i.e. low serum IGF1 and 31 P-NMR spectroscopy (NMRS) in muscle. At baseline, 31 P-NMRS displayed two patients with end-exercise muscle acidosis despite a low work output. On day 2, the introduction of triheptanoin was well tolerated in all patients, and in particular, there was no evidence of mitochondrial overload from triheptanoinderived metabolites. After 4 days of triheptanoin-enriched diet, muscle pH regulation was normalized in the two patients with pre-treatment metabolic abnormalities. A significant increase of serum IGF1 was also observed in all patients (205 ng/ml 60 versus 246 ng/ml 68, p=0.010). This study provides a rationale for extending our anaplerotic approach with triheptanoin in HD.

Introduction

Huntington disease (HD) is an inherited severely disabling disorder without curative or preventive treatment. We showed that early weight loss in HD is associated with a systemic metabolic defect, and that branched chain amino acids (BCAA) levels can be used as a biomarker, indicative of disease onset and early progression. [START_REF] Mochel | Early energy deficit in Huntington disease: identification of a plasma biomarker traceable during disease progression[END_REF] Levels of IGF1, which is regulated by BCAA, were also significantly lower in the HD group. [START_REF] Mochel | Early energy deficit in Huntington disease: identification of a plasma biomarker traceable during disease progression[END_REF] The decrease in plasma BCAA observed in our HD group suggested the activation of a compensatory mechanism to provide energy substrates to the Krebs cycle, as described in cachexia-producing illnesses. [START_REF] Bandt | Therapeutic use of branched-chain amino acids in burn, trauma, and sepsis[END_REF] Likewise, dietary compounds such as triheptanoin have been used in human therapeutic trials for their ability to refill the pools of intermediates of the Krebs cycle, a key energetic process called anaplerosis. [START_REF] Roe | Anaplerotic diet therapy in inherited metabolic disease: therapeutic potential[END_REF] Because of additional evidence for triheptanoin metabolites to cross the blood brain barrier, [START_REF] Mochel | Pyruvate carboxylase deficiency: clinical and biochemical response to anaplerotic diet therapy[END_REF] anaplerotic therapies represent promising molecules for reversing the energy deficit observed in both the brain and the periphery in HD patients. Based on the hypothesis that there is a need for Krebs cycle energy substrates in HD, we conducted a pilot study using a dietary anaplerotic approach to assess safety and short-term metabolic correction.

Methods

Study design

We included six HD patients with abnormal CAG repeats expansions (mean= 46 3) in the HTT gene with a mild to moderate disease, measured by the clinical scale UHDRS (Unified Huntington Disease Rating Scale) of 33 13 (Table 1). All participants were enrolled in a clinical protocol promoted by INSERM (COS 07-26, http://bir.inserm.fr), and approved by the local ethics committee. Written informed consent was obtained for all participants.

On the screening dayapproximately one month prior to the therapeutic trial motor dysfunction was evaluated with the UHDRS, and each HD participant underwent 31 P-NMRS testing in muscle. The six HD patients were asked to fill an opened-ended questionnaire during three consecutive days so that the dietician could determine caloric intake and devise daily menus ensuring that the triheptanoin oil provide 40% of an isocaloric diet, as previously established. [START_REF] Roe | Anaplerotic diet therapy in inherited metabolic disease: therapeutic potential[END_REF][START_REF] Mochel | Pyruvate carboxylase deficiency: clinical and biochemical response to anaplerotic diet therapy[END_REF] At day 1, the six HD participants were hospitalized and height and weight were recorded to calculate the body mass index (BMI). Blood and urine samples were collected after an overnight fast for standard analyses as well as plasma acylcarnitines, amino acids and ketone bodies, serum IGF1 and urine organic acids as described. [START_REF] Mochel | Pyruvate carboxylase deficiency: clinical and biochemical response to anaplerotic diet therapy[END_REF] At day 2, HD patients ingested the first doses of triheptanoin (1g/Kg/day divided in four meals). Repeated blood samples were collected before and, sequentially, after the first meal (30, 60, 90, 120 and 180 minutes after triheptanoin ingestion) for assessment of acylcarnitines profile, amino acids and ketone bodies. Urine samples were collected before and after the first ingestion of triheptanoin (90 and 180 Dietary therapy in Huntington disease 6 minutes) for analyses of organic acids. During the next 3 days, HD participants kept consuming an isocaloric diet enriched with triheptanoin (1g/Kg/day). At day 5, standard analyses were repeated fasting, as well as plasma acylcarnitines, amino acids and ketone bodies, serum IGF1 and urine organic acids. UHDRS scoring was performed and muscle 31 P-NMRS was repeated. In view of the low risks to subjects participating in this protocol, continuous and close monitoring by the Principal Investigator was done on an ongoing basis during the days the patients were taking triheptanoinalmost all triheptanoin-derived metabolites being utilized 3 to 4 hours after its administration. [START_REF] Mochel | Pyruvate carboxylase deficiency: clinical and biochemical response to anaplerotic diet therapy[END_REF]

P-NMR spectroscopy in muscle

NMR was carried out as described. [START_REF] Duteil | Metabolic and vascular support for the role of myoglobin in humans: a multiparametric NMR study[END_REF] Data were analyzed semi-automatically to provide: perfusion time-course, PCr rephosphorylation time constant (τPCr) and end-exercise acidosis level (pH). Intensity of exercise (W/S) was determined by correcting work output (W, in Joules) developed during exercise to calf muscle area section (S, in cm 2 ).

Statistics

The data are expressed as the mean ± standard error of the mean. Paired ttests (SPSS) were used to compare the values of plasma acylcarnitines, serum IGF1 and UHDRS before and after triheptanoin.

Results

Patients' BMI ranged from 19 to 25. There was no correlation between CAG repeats and metabolic measurement at baseline, except for an inverse correlation with plasma glutamine (p<0.001). All patients tolerated the treatment well and no adverse event was monitored during the trial and beyond. As a result of feeding triheptanoin, urinary excretion of derivatives of heptanoate oxidation were detectedpimelate, 6-hydroxyheptanoate, 3hydroxypentanoate (BHP), 3-ketopentanoate (BKP), 3-hydroxypropionate, and methylcitratebut there was no evidence of mitochondrial overload from triheptanoin-derived metabolites. Among plasma triheptanoin-derived metabolites, there was no substantial increase in either pentanoylcarnitine (C5) or heptanoylcarnitine (C7) (data not shown) but propionylcarnitine (C3) increased significantly in all patients (Table 1) indicating complete betaoxidation of heptanoate to propionyl-CoA. Substantial increases of C5 ketone bodies were observed after meal and triheptanoin administration (data not shown), with BHP to BKP ratios between 2.1 to 2.8. Plasma BCAA initially decreased after triheptanoin administration and then returned to their baseline levels on day 5 (data not shown). There was no significant change in the UHDRS scores before and after triheptanoin (Table 1). There was no correlation either between CAG repeats and the levels of triheptanoin metabolites (data not shown).

During plantar flexion dynamic 31 P-NMRS, all HD patients presented with a work output about two to four fold lower (Supplementary Table ) than what is seen in healthy individuals -W/S= 34.96 J/cm 2 ±16.35, n=7. Measurements Dietary therapy in Huntington disease 8 of intramuscular pH showed that two patients (P5 and P6) presented with end-exercise muscle acidosis -pH at 6.72 and 6.84, Figure 1 despite even lower exercise intensity compared to the four other patients -W/S at 11.44 J/cm 2 and 9.40 J/cm 2 respectively, Supplementary Table . Creatine rephosphorylation time constant was also increased in these two patients -tPCr respectively of 63.1 and 52.5sbut turned out to be normal when corrected for pH. [START_REF] Iotti | In vivo assessment of mitochondrial functionality in human gastrocnemius muscle by 31P MRS. The role of pH in the evaluation of phosphocreatine and Dietary therapy in Huntington disease 13 inorganic phosphate recoveries from exercise[END_REF] Of note, patient 5 had the lower BMI (i.e. 19) whereas patient 6 had the higher UHDRS score (i.e. 49).

Remarkably, after 4 days of triheptanoin-enriched diet, we observed a correction of end-exercise muscle acidosis -pH at 6.97 and 6.98, Figure 1 in the two patients with pre-treatment metabolic abnormalities (P5 and P6). This was associated with different hyperemic responses after treatment with an earlier return to basal level of perfusion for patient 5 (Figure 2) and the occurrence of a distinct peak of functional hyperemia from the 3 rd minute of recovery for patient 6 (Figure 2). In addition, we observed a significant increase of serum IGF1 in all HD patients (Table 1).

Discussion

Based on our observation of a hypercatabolic profile early in HD, our shortterm study aimed at directly identifying an energy deficit followed by a therapeutic intervention to improve peripheral energy metabolism in HD patients. Our anaplerotic approach using dietary triheptanoin was well tolerated in all HD patients, both clinically and biochemically. Of note, the levels of plasma BCAA decreased temporarily after the initiation of triheptanoin before returning to their baseline levels, likely reflecting the reversible inhibition of branched chain -ketoacid dehydrogenase kinase by medium chain fatty acids. [START_REF] Harris | Mechanisms responsible for regulation of branched-chain amino acid catabolism[END_REF] Furthermore, we analyzed markers of peripheral energy metabolism that were shown to be altered in early stages of HD, i.e. low serum IGF1 [START_REF] Mochel | Early energy deficit in Huntington disease: identification of a plasma biomarker traceable during disease progression[END_REF] or delayed phosphocreatine recovery (tPCr) after exercise measured by 31 P-NMR spectroscopy in muscle. [START_REF] Lodi | Abnormal in vivo skeletal muscle energy metabolism in Huntington's disease and dentatorubropallidoluysian atrophy[END_REF][START_REF] Saft | Mitochondrial impairment in patients and asymptomatic mutation carriers of Huntington's disease[END_REF] Although 31 P-NMR spectroscopy can lack sensitivity to detect mitochondrial dysfunction, [START_REF] Laforet | Exploration of exercise intolerance by 31P NMR spectroscopy of calf muscles coupled with MRI and ergometry[END_REF] the most noticeable finding from our study was that two patients developed muscle acidosis at baseline while performing a low intensity exercise. Their end-exercise pH corresponded to W/S ratios three-fold higher than in normal subjects (data not shown). These two patients also had longer tPCrs but, when corrected for pH, tPCrs appeared to be unaltered. [START_REF] Iotti | In vivo assessment of mitochondrial functionality in human gastrocnemius muscle by 31P MRS. The role of pH in the evaluation of phosphocreatine and Dietary therapy in Huntington disease 13 inorganic phosphate recoveries from exercise[END_REF] This observation differs from previous observations although end-exercise pH was either not reported, [START_REF] Lodi | Abnormal in vivo skeletal muscle energy metabolism in Huntington's disease and dentatorubropallidoluysian atrophy[END_REF] or unaltered in the HD group. [START_REF] Saft | Mitochondrial impairment in patients and asymptomatic mutation carriers of Huntington's disease[END_REF] Of note, our anaplerotic approach with triheptanoin led to a normalization of end-exercise muscle acidosis in the two patients with pre-treatment abnormalities. NMR measurements of muscle perfusion also suggested an effect of triheptanoin on hyperemic responses to exercise. Moreover, the improvement of peripheral energy metabolism in our Dietary therapy in Huntington disease 10 study is supported by the significant increase of serum IGF1 in all HD patients. IGF1 impacts mutant huntingtin by promoting its phosphorylation.

Phosphorylation inhibits mutant huntingtin toxicity by restoring its transport function. [START_REF] Zala | Phosphorylation of mutant huntingtin at S421 restores anterograde and retrograde transport in neurons[END_REF][START_REF] Humbert | The IGF-1/Akt pathway is neuroprotective in Huntington's disease and involves Huntingtin phosphorylation by Akt[END_REF] Therefore, the increase of IGF1 following treatment with triheptanoin may exert direct beneficial effects by restoring huntingtin function and/or blocking huntingtin toxicity in peripheral organs and possibly in the brain. It is not clear how triheptanoin mediates IGF1 levels, especially since triheptanoin did not increase the levels of BCAAknown to regulate IGF1. Ketone bodies cross the blood brain barrier and ketogenic diet was shown to modulate IGF1 metabolism in the rat brain. [START_REF] Cheng | A ketogenic diet increases brain insulin-like growth factor receptor and glucose transporter gene expression[END_REF] Likewise, it would be interesting to assess in vitro whether the ketone bodies derived from triheptanoini.e. BHP and BKPcan modulate IGF1 levels and huntingtin phosphorylation in primary cultures of striatal neurons.

In addition to the prominent role of brain energy deficit in the pathophysiology of HD, [START_REF] Browne | The energetics of Huntington's disease[END_REF][START_REF] Cui | Transcriptional repression of PGC-1alpha by mutant huntingtin leads to mitochondrial dysfunction and neurodegeneration[END_REF] there are several lines of evidence for a more systemic energy deficit. Our findings of hypercatabolism in HD [START_REF] Mochel | Early energy deficit in Huntington disease: identification of a plasma biomarker traceable during disease progression[END_REF] were indeed recently confirmed in both clinical [START_REF] Aziz | Weight loss in Huntington disease increases with higher CAG repeat number[END_REF][START_REF] Goodman | The metabolic profile of early Huntington's disease--a combined human and transgenic mouse study[END_REF] and preclinical studies. [START_REF] Van Der Burg | Increased metabolism in the R6/2 mouse model of Huntington's disease[END_REF][START_REF] Zabel | A large number of protein expression changes occur early in life and precede phenotype onset in a mouse model for huntington disease[END_REF] Our data emphasize that 31 P-NMRS may provide relevant biomarkers of peripheral energy metabolism in HD. This study also provides a rationale for extending our anaplerotic approach with triheptanoin in HD. A double-blind placebo-controlled trial with clinical outcome measurements is planned in order to confirm the potential benefit of anaplerotic therapies to improve, or even reverse, the energy deficit both in the periphery and the brain of HD patients and presymptomatic individuals.

Figure 1 :

 1 Figure 1: End-exercise pH before (1) and after (2) triheptanoin in 6 patients

Figure 2 :

 2 Figure 2: Perfusion kinetics during exercise recovery before and after

  Figure 1

Table 1 :

 1 Clinical characteristics of the six HD patients, as well as UHDRS, plasma propionylcarnitine (C3-carnitine) and serum IGF1 levels, before and after triheptanoin. Paired t-tests were used to compare the values before and after triheptanoin and significant changes are indicated with p values. * Pathological repeats size.

				Age at	Age at	UHDRS	Plasma C3-carnitine ( mol/l)	Serum IGF1 (ng/ml)
		Sex CAG*	onset	examination	Pre-	Post-	Pre-	Post-	p	Pre-	Post-	p
				(years)	(years)	treatment	treatment	treatment	treatment		treatment	treatment
	P1	F	46	49	51	39	43	0.17	0.52		115	136
	P2	M	43	45	60	30	31	0.13	0.29		196	268
	P3	F	51	30	34	43	38	1.16	2.85		282	343
	P4	F	45	45	50	20	15	0.94	1.85		238	254
	P5	F	43	40	48	15	9	0.52	1.78		236	246
	P6	F	50	33	41	49	45	0.88	2.05		165	218
	Total		46 ±3	40 ±7	47 ±9	33 ±13	30 ±15	0.63 0.43 1.56 0.97 0.011 205 60	246 68	0.010

Acknowledgement

Many thanks to the patients and their trust in new therapeutic avenues, to the Centre d'Investigation Clinique and his devoted team, as well as to Josiane Sage for her contribution to the study design, Anne Defarge and the Department of Dietetics for their help with the dietary assessment, and Pr Alexis Brice and Dr Raphael Schiffmann for their critical reading of the manuscript.

Dietary therapy in Huntington disease