Instrumentation économique et changements industriels : le pilotage d'une unité de mécanique automobile

Abstract

Management tools and industrial change : the case of a car plant. Since the early 80's, French auto plants have been experimenting revolutionary changes associated with the new productive paradigm : Lean Production. How can objectives such as "zero inventory, zero breakdown, zero quality default" be integrated operationally in the economic instruments with which people appreciate situations on the shop floor and select production planning strategies ? This article adresses this question in the case of a mechanical components plant. This industrial context is characterised by a diversified production, high technical sophistication in the product and the process line, great complexity in the product flow, which integrates batch and line processing. It shows the inadequacy of existing decision-making processes : the economie perception on the shop floor emphasizes the direct labor costs, whereas the economic results are essentially driven by the performances of the machines ; economic consequences of incidents (especially process breakdowns) are not quantified, which leads to misoriented options in the maintenance strategy ; interaction between different sections of the process are not well estimated, the local responses being very unoptimised, when evaluated on the global level of the product line. Therefore, the plant engaged a general reorganization of its structure, in order to create coherence between responsability patterns and the process flow logics. The research then proposed models in order to help the reorganized productive teams to evaluate properly the economic impact of different decisions. The application of these models within the plant led to signifiant changes in production practices : the economic solidarity of different subsystems was demonstrated and advocated new communication processes ; the cost of breakdowns was reappreciated by calculating the economic consequences of flow desorganizations, a result that led to reallocations in maintenance resources ; the tradeoff between production cost and delivery risk was analysed, which favoured new production programs. The modelling was not very sophisticated, because the purpose was not to simulate very realistically the shops but to demonstrate the importance of new productive concepts. The models were elaborated with the production team, the discussions on the modelling choices having, in themselves, a great pedagogical effect on the modelling visions about production strategies. Major change in productive practices, such as the Lean Production Revolution, are generally introduced at a technical and political level : new technologies and processes introduced are in the workshops, new objectives are advocated. The article shows how that changes in individual and collective practices cannot be carried operationnally without developing also, at all levels, new managerial apparatus : new organizational patterns and new models which helps actors to analyse situations "in the right way". This leads to a modelling perspective which has not the ambition to replace human decision making, but to help the human evaluating and negociating process.