ESTCB - Livros ou capítulos de livros
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Browsing ESTCB - Livros ou capítulos de livros by Field of Science and Technology (FOS) "Engenharia e Tecnologia"
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- Combining DDMRP and CONWIP: A simulation study of the pool-sequencing rulePublication . Fernandes, Nuno O.; Almeida, João; Ferreira, Luís Pinto; Ávila, Paulo; Silva, Sílvio ,Two essential tasks in production planning and control are the generation and the release of orders to the shop floor. In this study order, generation is based on the Demand Driven Materials Requirement Planning system, while order release is based on the CONstant Work-in-Process system. Although the two systems alone have been extensively studied, their combination has received much less attention. In this paper, we address the problem of sequencing replenishment orders generated by the Demand Driven Materials Requirement Planning system to be released by the CONstant Work-in-Process system. Four pool-sequencing rules have been considered. Two of these are used by Demand Driven Materials Requirement Planning for establishing priorities for order planning and order execution. The other two are the First-Come-First-Served rule and a virtual due date rule. Results of a simulation study show that the rules proposed in the Demand Driven Materials Requirement Planning literature for planning and for execution are not the best options for pool-sequencing, particularly for restricted levels of workload allowed on the shop floor.
- Design for automation, edge services, and manufacturing – A React Native interface for collaborative robot palletizing systemsPublication . Torres, Pedro; Esteves, Arthur; Ribeiro, Fillipe; Barbosa, FláviaThis work is part of the PRODUTECH R3 mobilizing agenda project and provides a comprehensive overview of the concepts of Design-for-Automation (DfA), Design-for-Edge Services (DfES), and Design-for-Manufacturing (DfM), highlighting their importance within the Industry 4.0 paradigm. These principles are crucial for developing smart, efficient, and scalable industrial solutions. As a case study, the paper presents the development of an automatic configuration system for a collaborative robotic palletizer, implemented in React Native. The graphical interface simplifies the mosaic configuration process, improves the user experience, and ensures integration with the collaborative robot. Using cutting-edge computing resources, the solution achieves real-time performance and scalability, offering significant value to the company involved and its customers. The study demonstrates how the adoption of these design principles can drive innovation and efficiency in industrial processes, reinforcing the fundamental role of user-centered solutions in the digital transformation of production systems.
- A simulation study of DDMRP and MRP manufacturing planning and control systemsPublication . Guedes, N.; Ferreira, Luís Pinto; Silva, F.J.G.; Fernandes, Nuno O.; Silva, Sílvio C.Demand Diven Material Requirements Planning (DDMRP) is a manufacturing planning and control system for fast response to customer requirements in varying and volatile demand and supply markets. DDMRP is an extension of the Material Requirements Planning (MRP) approach that explores the principles of Lean and Theory of Constraints production philosophies to reduce manufacturing response time and make good use of manufacturing resources. It achieves this by promoting flow through selective, reduced, and continuously adjusted inventory levels to synchronize manufacturing and supply with customer market demand. Only a few studies compared the performance of both approaches. However, these studies have not fully addressed the relationship between inventory and service levels. Therefore, this research contributes to a better understanding of this relationship by evaluating and comparing the performance of these two approaches in a multi-product, multi-stage production system. The results of a discrete-event simulation study show that DDMRP outperforms MRP regarding the work-in-process and finished-goods-inventory levels required to achieve a given service level.
- A simulation study of walking-workers assignment strategies based on work zonesPublication . Fernandes, Nuno O.; Thürer, Matthias; Matos, P.This study addresses an “U” shaped assembly line with walking workers and flexible worker assignments. Workers, rather than machines, are the constraining resource in a dual-resource production system. Assignment strategies for walking workers based on Takt Time or restricted time zones of overlap are compared under different production conditions, including processing time variability and worker efficiency conditions. Four strategies have been considered namely: dedicated zoning, relaxed zoning, float zoning, and overlapped zoning. Discrete event simulation is used to assess the performance of these strategies under the controlled release of jobs to the assembly line based on a Constant Work In Process policy. Results show that heterogeneous worker efficiencies strongly impact the performance of all strategies. However, this impact depends on the specific strategy. The study contributes to a better understanding of the behavior of walking workers’ strategies in “U” shaped assembly lines controlled by a Constant Work In Process policy.