M.A. Sebastián

Systemic criterion of sustainability in agile manufacturing

Agile manufacturing systems work in a constantly changing global market, particularly assembly systems at the last stage of product differentiation. Meanwhile, sustainability is becoming a key issue for manufacturing strategy. This paper formulates a systemic criterion of sustainability in agile manufacturing and computes it through flexibility and complexity. It is defined as a ratio of utility and entropy as a sustainability measurement. Under a unified framework, utility allows one to quantify the contributions to agility, in particular system flexibility. Complexity is measured by entropy. Thus, an original complementary role of flexibility and the complexity of the system are proposed. Developed from the distribution of system states, the systemic approach to sustainability in terms of output evolution is enriched. Based on a simple assembly line integer model simulation, a first quantitative analysis illustrates the concepts introduced.

Surface Finish Optimization of Magnesium Pieces Obtained by Dry Turning Based on Taguchi Techniques and Statistical Tests

Magnesium is one of the lightest metallic materials and is used in industries such as aeronautics or aerospace because of its excellent weight to resistance ratio. The surface finish is a key quality characteristic in dry turning of magnesium pieces and is often affected by multiple factors within the machining process. Factors such as feed rate, cutting speed, tool coatings, and the interactions among these were investigated in this experimental study. The objectives of this work were to identify the main factors that influence the dry turning of magnesium and to select the optimal manufacturing conditions that result in minimum surface roughness. To achieve these objectives, the “smaller-the-better” characteristic from the Taguchi method was applied to the average roughness R a . Using an orthogonal experimental design approach, the signal-to-noise (S/N) ratio was used to quantify the amount of variation present in the surface roughness. Then, graphical exploratory data analysis was conducted, and the variability in the S/N ratio of surface roughness was modeled via analysis of variance (ANOVA) fixed-effect analysis and Snedecors F-tests. This statistical modeling, together with Least Significant Difference testing permitted different combinations of cutting conditions to be classified into two groups: (I) optimal combinations and (II) the remaining combinations.

A decision support system for sheet metal blanking process parameters selection

Abstract Once manufacturing criteria have been established, a well-founded decision support system (DSS) may solve the problem of selecting the optimum set of parameters. An axiomatic approach has been used in order to quantify final part quality. The present case takes into account form errors in blanking process and an equation model that enables quality quantification through part complexity has been developed. The measurement of complexity in blanked parts may be simplified to a study of the effect of the fundamental parameter (clearance) on the form errors. In order to consider economic influences, technical cost modelling (TCM) has been implemented. With the purpose of uniting both aspects under one common criterion, a function that evaluates them in a single measuring system has been defined. Based on this function, the developed DSS integrates a formal multi-attribute decision model with a relational database. The decision model enables representation of the user’s preferences as regards decision factors. Due to the great number of parameters and variables that intervene in the system, a computerised graphical interface application has been developed allowing decision makers to compare, justify and evaluate different alternatives in a friendly environment.

Virtual reality applications for the next-generation manufacturing

Virtual reality (VR) is a very helpful and valuable work tool for the simulation of manufacturing systems. It can be used in both industrial and academic/researcher fields allowing the systems behaviour to be learnt and tested. VR provides a low-cost, secure and fast analysis tool. It also provides benefits, which can be reached with many different system configurations. The work presented in this paper reviews some of the most recent developments that have been made in this way and proposes a general methodology for the creation of virtual environments applicable to manufacturing systems. The application samples of this procedure are focused on flexible manufacturing systems (FMS), in which the economic and safety problems are heightened.

Implementation of Technological and Geometrical Parameters in Forging Processes by Means of the Upper Bound Element Technique

Present work is applied to the upper bound elemental technique (UBET) with the triangular rigid zones model in forging processes. This application allows incorporating different technological and geometrical parameters, not usually used at this analytic method. The strain hardening and the influence of the temperature are someone of these parameters considered. In the other side, friction with shear factor and sliding (Coulomb) factor are estimated, even simultaneously. A fundamental advantage in the application of the proposed method is its adaptation on a free die‐block profile not limited to parallel and plane surfaces, by means of combined profiles with different inclinations.

Analysis of the Energy Vanished by Friction in Tube Drawing Processes with a Fixed Conical Inner Plug by the Upper Bound Method

In this work, an analysis of the energy vanished by friction of thin-walled tube drawing processes in conical converging dies with a fixed conical inner plug has been conducted. The method used for analysis is the upper bound method (UBM), and the plastic deformation zone has been modelled by three triangular rigid zones (TRZ). The tube inner diameter is considered constant during the process, and therefore, a state of plane strain can be assumed. In addition, the existent friction between the external surface of the tube and the die (material-die), as well as that between the inner surface of the tube and the plug (material-plug) has been modeled by Coulomb friction (μ1 and μ2, respectively). Some significant findings emerged from this study are: the establishment of explicit expressions for evaluating the non-dimensional energy vanished by friction in the die and in the plug, the ability to select the plug that enables the process to be performed with a lower requirement of energy under defined conditions, and the detection of coupled effects between the friction coefficients define above.

Surface roughness model based on force sensors for the prediction of the tool wear.

In this study, a methodology has been developed with the objective of evaluating the surface roughness obtained during turning processes by measuring the signals detected by a force sensor under the same cutting conditions. In this way, the surface quality achieved along the process is correlated to several parameters of the cutting forces (thrust forces, feed forces and cutting forces), so the effect that the tool wear causes on the surface roughness is evaluated. In a first step, the best cutting conditions (cutting parameters and radius of tool) for a certain quality surface requirement were found for pieces of UNS A97075. Next, with this selection a model of surface roughness based on the cutting forces was developed for different states of wear that simulate the behaviour of the tool throughout its life. The validation of this model reveals that it was effective for approximately 70% of the surface roughness values obtained.

Novel Ergonomic Postural Assessment Method (NERPA) Using Product-Process Computer Aided Engineering for Ergonomic Workplace Design

Background Musculoskeletal disorders (MSDs) that result from poor ergonomic design are one of the occupational disorders of greatest concern in the industrial sector. A key advantage in the primary design phase is to focus on a method of assessment that detects and evaluates the potential risks experienced by the operative when faced with these types of physical injuries. The method of assessment will improve the process design identifying potential ergonomic improvements from various design alternatives or activities undertaken as part of the cycle of continuous improvement throughout the differing phases of the product life cycle. Methodology/Principal Findings This paper presents a novel postural assessment method (NERPA) fit for product-process design, which was developed with the help of a digital human model together with a 3D CAD tool, which is widely used in the aeronautic and automotive industries. The power of 3D visualization and the possibility of studying the actual assembly sequence in a virtual environment can allow the functional performance of the parts to be addressed. Such tools can also provide us with an ergonomic workstation design, together with a competitive advantage in the assembly process. Conclusions The method developed was used in the design of six production lines, studying 240 manual assembly operations and improving 21 of them. This study demonstrated the proposed method’s usefulness and found statistically significant differences in the evaluations of the proposed method and the widely used Rapid Upper Limb Assessment (RULA) method.

Deep drawing tool for e-learning: A didactic approach for manufacturing engineering education

Manufacturing processes are an important element in industrial engineering education. In distance education, the learning of engineering subjects has a special difficulty, which can be reduced by means of the use of new technologies, and the practice of mixed models of learning. One of these processes is the deep drawing due to its relevance in the industry. This paper presents a deep drawing tool for e-learning. The tool has been realized for its use in the Master degree because it requires advanced knowledge in manufacturing processes. The instrument has been developed with the objective of the students who can: a) Select input data for get the formability of material to deep drawing; b) Select the process that provides the best solution from a technological perspective; c) Optimize the process for saving the material; d) Know the influence of the punch in the results; e) Consideration of the process cost. The structure of the system has three subsystems: a) Solve, module for data processing and the generation of results; b) Materials, module for management data of the system; and c) Interface, module for user interaction. The tool has been implemented in the software tool programming, developed in Java. This language has been selected because it provides a methodology of object-oriented programming and its execution is possible in multiple operating systems. The paper describes each step of the tool, from the input data to final analysis and they are shown through the results given by the tool.

An educational software to reinforce the comprehensive learning of materials selection

An educational software, called CalSev 1.0.2, has been developed for supporting the teaching in materials selection seminars. As a case study, a selection of materials for nuclear reactor pressure vessels has been chosen, because it is a representative example of the relationship between chemical composition, mechanical properties, and in‐service behavior. This software has been developed to improve the students’ understanding of the materials selection tasks, providing an interactive user‐friendly platform that allows to modify—in real time—the content of chemical elements and mechanical requirements to obtain a materials performance evaluation. Due to its versatility, this informatics tool represents a great value for educational purposes, with special impact in blended and distance learning, by simplifying the arduous task of materials selection for a wide range of applications and promoting a collaborative working environment by easing the creation of small groups analyzing different study cases. Finally, to evaluate the functionality, interest, user‐friendliness and the educational characteristics of CalSev 1.0.2, a survey among 36 undergraduate students has been carried out.