Nikolaos Papakostas

Digital manufacturing: History, perspectives, and outlook

Abstract Digital manufacturing has been considered, over the last decade, as a highly promising set of technologies for reducing product development times and cost as well as for addressing the need for customization, increased product quality, and faster response to the market. This paper describes the evolution of information technology systems in manufacturing, outlining their characteristics and the challenges to be addressed in the future. Together with the digital manufacturing and factory concepts, the technologies considered in this paper include computer-aided design, engineering, process planning and manufacturing, product data and life-cycle management, simulation and virtual reality, automation, process control, shopfloor scheduling, decision support, decision making, manufacturing resource planning, enterprise resource planning, logistics, supply chain management, and e-commerce systems. These technologies are discussed in the context of the digital factory and manufacturing concepts.

An approach to operational aircraft maintenance planning

This paper describes a short-term planning methodology of the line maintenance activities of an airline operator, at the airports, during turn-around time (TAT). The proposed methodology supports decision making for deferring maintenance actions that affect the dispatching of the aircrafts, aiming at high fleet operability and low maintenance cost. Based on health assessment and additional information regarding operational and economical constraints at the operators fleet level, a multi-criteria mechanism evaluates a set of generated maintenance plan alternatives. An alternative is defined as the possible allocation of all deferred maintenance tasks to a set of suitable airport resources. The selected decision making criteria are cost, remaining useful life (RUL), operational risk and flight delay. A series of experiments is conducted in order to validate and test the approach.

On industrial learning and training for the factories of the future: a conceptual, cognitive and technology framework

The manufacturing education addresses significant challenges in view of paving the way for the human capital of the Factories of the Future. This paper introduces a specification framework for the delivery of industrial learning and training, addressing the needs for the “knowledge” workers of the factories of the future. A review of the relevant background, including the activities associated with the industrial learning and its basic methods as well as some emerging paradigms, is first provided. A Teaching Factory based paradigm is then suggested as the conceptual foundation of this framework. A cognitive framework, addressing the major building blocks of the industrial learning process, namely the attitude the knowledge the skills and the competences is being defined. An appropriate technology framework, dealing with the needs of engineers and blue-collar workers, for practising the manufacturing knowledge content within digital environments, is suggested at this point. Finally, the approach of the future implementation of the specific framework is being discussed.

Flexibility and complexity: is it a trade-off?

The aim of this paper is to investigate the relationship between flexibility and complexity. A number of flexibility measurement approaches are presented and are connected with the flexibility types they address. A series of measures and methods for the analysis and assessment of static and dynamic complexity are provided. A new measure for the assessment of static complexity, based on network complexity, is introduced. The relationship between flexibility and complexity is investigated with the help of two sets of indicative, simple and yet realistic manufacturing systems.

DESYMA: assessing flexibility for the lifecycle of manufacturing systems

The objective of this work is to describe a method of assessing the flexibility of a manufacturing system, in an uncertain market environment, under lifecycle considerations. The flexibility of a manufacturing system is determined by statistical analysis of the discounted cash flow (DCF) estimates of the manufacturing systems lifecycle cost, over a time horizon and for a large variety of market scenarios. The systems lifecycle cost is calculated at a minimum level with the help of a specially developed algorithm. The method is used in a test case for investing in a production system, using real-life data derived from the automotive industry.

Refinery short-term scheduling with tank farm, inventory and distillation management: An integrated simulation-based approach

This work addresses primarily the scheduling of a refinery importing various types of crude oil. The refinery operation discussed in this paper involves the unloading of crude oil to storage tanks, the transfer and blending from storage tanks to charging tanks and crude oil distillation units, and the arrangement of the temperature cut-points for each distillation unit. The paper describes a simulation-based approach to the refinery operation, which is modelled as a pooling problem. The proposed approach uses a random-search formulation, which allows for controlling search depth, breadth and solution quality, as well as computational effort. An implementation of the proposed approach is presented in a real case scenario.

Industrial applications with cooperating robots for the flexible assembly

This article discusses the key features of cooperating robotic cells in the automotive assembly, highlighting the key elements in the engineers’ decision-making process, while designing and implementing an assembly line for the Body In White. The main issues, affecting the performance of cooperating robotic cells, are discussed with the aid of a case study, where two different scenarios are compared. The first scenario uses a conventional fixture-based configuration of a robotic cell for performing a welding operation, while the second features the use of cooperating robots. The cases are compared with the aid of a simulation platform, and future potential developments are also discussed.

The role of simulation in digital manufacturing: applications and outlook

Digital manufacturing technologies have been considered an essential part of the continuous effort towards the reduction in a product’s development time and cost, as well as towards the expansion in customisation options. The simulation-based technologies constitute a focal point of digital manufacturing solutions, since they allow for the experimentation and validation of different product, process and manufacturing system configurations. This article investigates simulation-based applications in a series of different technological and manufacturing domains. First, this article discusses the current industrial practice, focusing on the use of information technology. Next, a series of simulation-based solutions are explored in the domains of product and production process design, as well as in the area of enterprise resource planning. The current technologies and research trends are discussed in the context of the new landscape of computing hardware technologies and the emerging computing services, including the initiatives comprising both the Internet cloud and the Internet of things.

Quantifying the flexibility of a manufacturing system by applying the transfer function

This paper discusses a method of estimating the flexibility of a manufacturing system. The proposed approach is motivated by the dynamic behaviour analogy between a mechanical and a manufacturing system. The main hypothesis is that the flexibility of a manufacturing system can be calculated in the same manner as the damping factor of a mechanical system. In order for the validity of the proposed method to be tested and discussed, a set of experiments has been designed and executed, initially for a simple production system. An industrial production system has also been studied using the same approach. The results prove that this method can be used for the estimation of a manufacturing systems flexibility.

On the Configuration and Planning of Dynamic Manufacturing Networks

Manufacturing organizations have been attempting to improve the operation of supply networks through efficient supply chain management. Dynamic manufacturing networks (DMNs) constitute chains of diverse partners, whose operation and interaction may change in a rapid and often not predictable way. While the existing supply chain models are quite static and examine transportation modes, product changeover and production facility options with fixed suppliers and over a long period of time, the DMNs address operations and risks on a daily basis. In this paper, a novel decision-making approach is proposed for supporting the process of configuring a DMN from a holistic perspective, taking into account production, transportation and time constraints as well as multiple criteria such as time and cost.