Catálogo de publicaciones - libros

A problem of designing conflict-free schedules for concurrent repetitive manufacturing processes using resources in mutual exclusion is considered. Processes that share resources can wait for resources (machines) required to complete successive operations in their production routes. Systems of processes sharing only one resource are considered. A problem of finding operation times and starting times of the processes for which a schedule exists, with no process waiting for access to the shared resource has been solved using the constraint programming (CP) approach. The necessary and sufficient conditions for existence of conflict-free schedules have been implemented in the Oz/Mozart constraint programming system used to find the schedules.

The lean manufacturing model through the elimination of waste creates customer value and efficient manufacturing work flows matched to customer demand. Promoters of the lean model contend that lean manufacturing will become the global manufacturing standard across the totality of industrial applications for the 21st century. This assertion is assessed across a variety of industrial sectors and the relevance of the lean model is considered within a Digital Enterprise Technology Environment, a construct that serves to manage product life-cycles on a global scale.

In the early stages of the Steel Detailing Design process (Structural Design), most of the activities are focused in the designer. Nowadays Detailing CAD packages offer a wide range of options that in some cases exceeds the ones needed to fulfill a specific task. Sometimes having such a wide range span can be self-defeating for a smooth process evolution as the designer has to browse repetitively in the user interface for a particular tool. In this paper we present a Knowledge based approach for the exploitation of semantic aspects (e.g. user intentions and tasks) for the real time automatic generation of graphical user interfaces on a Steel Detailing CAD software. We base our approach in international standards (CIS/2) for the specific domain and as test case we present a system implementation of the proposed schema.

Process chains in manufacturing and order processing increasingly depend on the successful usage of information systems. However, available approaches typically lack the opportunity to evaluate the expecting process chain and modeling quality or rely on a system driven in-depth analysis. The presented easy-to-use graphical approach overcomes existing drawbacks and integrates the domains of manufacturing and order processing at the same time.

The current study addresses the accuracy of bend elements and global dimensions with tolerances based on an analytical method, where each deviation in part dimension is represented by type A and type B errors, as instructed by ISO-GUM. Meanwhile, a generic formula is presented to estimate the deviations in the global dimensions of interest in bent parts based on the deviations in the participating bend elements. The deviations in the bend elements formed in each operation are in turn estimated through an analytical simulation model. Therefore, the error propagation in consecutive bending operations using a specified process plan is simulated. Using such a top-down analytical approach, the errors of the global dimensions with tolerances were represented and estimated through the errors encountered for each operation. Finally, a procedure for estimating dimensional errors in bent parts is suggested and illustrated with an example to show the applicability of the method.

For companies which are part of complex supply chains structures, risk management is getting increasingly important. This development is the result of actual trends that can be observed, especially in the automotive industry. Companies reduce their work in progress to cut down the cost level of stock; certainly the delivery performance is expected to be excellent. However, the reduction of work in progress frequently results in missing parts or raw material. Moreover, the logistic environment is continuously getting more turbulent by continuously fluctuating demands and in some cases - like steel for example - increased delivery times for raw materials. Combined with the mentioned reduction of work in progress, achieving the agreed logistic performance is not ensured without a significant additional effort.

An approach, developed by IPH, is the use of discrete-event simulation tools for the combination of production planning and control methods with logistic monitoring tools. Based on the periodic analyses of the logistic supply chain performance and the simulation of different alternative scenarios, the relevant planning parameters are identified and adopted to the planning processes. For this feedback loop, logistic risk management aspects need to be considered as well. By identifying potential risks and developing counter measures, the logistic performance is increased tremendously and consequently the performance of the complete supply chain is improved.

In this paper, the specific challenges of forging companies that are part of an automotive supply chain are described and lined out. The forging industry is subject to the implementation of new forging technologies for being able to battle the competition from low cost countries. Those new technologies are not only beneficial; they bear a lot of risks for the companies as well. For some technologies, the tool life cannot be forecasted accurately; hence the lot sizes are only estimated roughly and not calculated with a well proofed algorithm.

During the last few decades, Manufacturing Enterprises (ME) have been facing increasingly volatile market conditions due to changes such as globalization, reduced product lifetimes and increased competition. Simulation modeling (SM) has been widely deployed to help MEs optimize their operations by assessing uncertainties and possible future organizational behaviours. This paper reports ongoing research study which is developing and testing the use of a unified set of SM concepts within the context of Enterprise Modelling (EM) to facilitate process oriented organizational change related to the planning and control of ME’s operations. Case study research findings are described which focus on optimizing multi-product flows through assembly shop resources available to a furniture making SME based in UK.

The incessant pressure of meeting customer demands at a decreasing cost across the globe is forcing the modern day manufacturers to adopt a paradigm shift from the traditional way of manufacturing. This includes the utilization of digitalized manufacturing information flow in the form of agents to facilitate the collaborative product development and manufacturing across different geographical locations. To meet these growing needs and fierce competition in the current manufacturing arena, the authors in this paper have presented an -an intelligent manufacturing based on internet, intranet, web and agents. The architecture utilizes the distributive and autonomous behavior of the functional agents, CORBA, XML, Java and web.

The establishment of collaboration commitments, represented by contracts or agreements, is a crucial step in a virtual organization (VO) creation process. The contract negotiation shall proceed in parallel with the other phases of the VO creation process, namely preparatory planning, consortia formation, and VO launching. In each step specific elements for the contract / agreement are collected as a result of a focused negotiation processes. The specifications for a contract negotiation wizard in this context are proposed.

The maintenance of complex capital goods wins more and more in importance. This article will describe a method to raise a condition prognostication of modules and spare parts and the corresponding order probabilities of spare parts during the tear down process. It will give an overview how uncertainty can be represented by the use of probabilities. The consideration of different factors of influence, for example external effects such as the operation period of a product, causal relationships and influence of damaged spare parts, can be represented by the use of Bayesian Networks.