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Influence of Heat Treatments on Microstructure of Electron Beam Additive Manufactured Ti-6Al-4V Alloy
Damir Skuhala, 2020, master's thesis

Abstract: Additive manufacturing of metallic parts is increasing in popularity and starting to emerge as a new competitive manufacturing process. Printed structures from Ti-6Al-4V titanium alloy, produced by electron beam additive manufacturing (EBAM), possess columnar prior β grains and layer bands, alongside an ultrafine lamellar microstructure, which is prone to low ductility and thus requiring thermal post-processing. Several heat treatments were performed in α + β and β field, in one or multiple stages. The results showed that bi-lamellar microstructure can be obtained, and that selection of annealing temperature and cooling rate determines the morphology, thickness, and distribution of both primary and secondary α features. Mechanical properties were evaluated on three selected heat treatments. Annealing of the As-built condition was performed at 710°C (HT1) and 870°C (HT2), resulting in lamellar microstructure with basketweave morphology. In two-stage heat treatment (HT3), the temperature in the first stage has exceeded β transus, while in the second, annealing was performed again at 870°C. The microstructure was characterized as a mixture of lamellar and bi-lamellar with large α colonies inside the rearranged prior β grains. Air cooling was performed in all HT from the final annealing stage. Strength and hardness have decreased with increasingly coarser microstructural features, while fracture toughness was improved, except in HT1, where the decrease in the fracture toughness was mainly attributed to reduced intrinsic toughening. As-built and HT1 conditions were effected by microstructural texture, causing inconsistent fracture morphology, reduced crack roughness and scattering in results. The influence of texture was decreased by coarser microstructure in HT2, while crack tortuosity was increased. Very unpredictable fracture behaviour was observed in HT3 due to large α colonies, as their orientation determines the areas of ductile or cleavage crack propagation.
Keywords: Titanium alloys, Ti-6Al-4V, additive manufacturing, EBAM, heat treatments, microstructural optimization, mechanical properties, fracture toughness
Published: 11.05.2020; Views: 567; Downloads: 143
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Material and energy balance in the planning of production costs
Manuela Ingaldi, Dorota Klimecka-Tatar, 2016, independent scientific component part or a chapter in a monograph

Keywords: material, energy, manufacturing system model, production costs, planning
Published: 11.05.2018; Views: 825; Downloads: 68
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Selection criteria for six sigma projects in Slovenian manufacturing companies
Dušan Gošnik, Matej Hohnjec, 2009, original scientific article

Abstract: Researches reveal that successful six sigma implementation is related to proper six sigma project prioritisation and selection. This research is limited to the selection of six sigma projects in some manufacturing companies in Slovenia. The purpose of this study is to identify what criteria are considered for prioritisation and selection of six sigma projects and how six sigma projects are selected. A research sample is limited by the number of companies which have implemented six sigma so far. The results indicate that Slovenian manufacturing organisations tend to select six sigma projects based on criteria such as customer satisfaction, connection with a business strategy financial benefits, and growth of the organisation. Several tools and techniques such as quality cost analysis, brainstorming and interviews are used to identify and prioritise projects. Identification of the most commonly used criteria to select six sigma projects can help practitioners to select projects based on multiple criteria by using tools and techniques identified in this study. This topic has not been applied in the field of Slovenian manufacturing companies and thus it presents the first study in this field in Slovenia.
Keywords: manufacturing, quality, six sigma, projects, management, case study, Slovenia
Published: 22.01.2018; Views: 582; Downloads: 268
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Lean manufacturing effects in a Serbian confectionery company
Ilija Djekic, Dragan Zivanovic, Sladjana Dragojlovic, Radoslava Dragovic, 2014, original scientific article

Abstract: Background and Purpose: The objective of this paper was to evaluate effects of implementing lean manufacturing in a Serbian confectionery production company during a period of 24 months, emphasizing observed benefits and constrains. Company ‘case study’ is a leading confectionery producer in Serbia with annual production of more than 25,000 t. Methodology/Approach: The research method was case study. The approach in implementing lean manufacturing was structured in five phases, as follows: (i) training, (ii) analysis of lean wastes on one technological line, (iii) choice of lean tools to be implemented in the factory, (iv) implementation of lean tools in production and maintenance, (v) development of continual improvement sector and further deployment of lean tools. Results: Lean manufacturing tools implemented in the production process were visual control and single minute exchange of dies (SMED). Maintenance process implemented 5S with total productive maintenance (TPM) and problem solving sessions being the tools implemented in both processes. During the observed period, results of these tools showed the following: visual control tables initiated 61 improvement memos out of which 39% were fully implemented; a total of 2284 minor problems had been recorded, with over 95% of issues revealed in due time; total SMED time decreased for 7.6%; 19 problem solving sessions were initiated with 58% of solving effectiveness, and the remaining converted to on-going projects. In maintenance 5S improved from 29.9 to 60.3; overall equipment effectiveness (OEE) indicator increased from 87.9% to 92.3%; mean time between failure (MTBF) increased for 16.4%. Conclusion: As a result of all activities, 20 in-house trainings and 2 ‘kaizen’ events including motivational training have been initiated with 54 documents being revised and improved in order to contribute to more efficient processes.
Keywords: lean manufacturing, confectionery production, benefits, constraints
Published: 04.12.2017; Views: 644; Downloads: 101
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Innovation and human resource management
Anastasia Katou, 2008, original scientific article

Abstract: The purpose of this paper is to investigate the pathways leading from innovation to organisational performance by using structural equation modelling. Specifically, we used this analytical tool to test a research framework that is constituted by a set of causal relationships between organisational contingencies, innovation, HRM policies (resourcing, training, rewards, relations), HRM outcomes (skills, attitudes, behaviour), and organisational performance. Employing data from organisations operating in the Greek manufacturing sector, results indicate that the impact of innovation on organisational performance is positive and mediated through HRM policies and HRM outcomes, and moderated by organisational context (management style, organisational culture).
Keywords: human resources, innovation strategy, HRM policies, causality, structural equation modelling, Greek manufacturing
Published: 30.11.2017; Views: 611; Downloads: 96
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Competency based training need assessment
Shulagna Sarkar, 2009, original scientific article

Abstract: Training is a usual formula for organisations through which employees are introduced to learning, but the challenge lies in identifying the appropriate training needs of employees. The success of a training program depends primarily on the need assessment. The paper discusses the process of competency mapping and focuses on how competency mapping can be used for conducting training need assessment. The paper is an empirical research based on both public and private manufacturing units in India. Primary and secondary data was collected using number of techniques. Gap analysis has been performed for employees and it has also been aimed to verify the changes in competency gaps on applying need based training. On providing need based training, significant difference was measured in the level of competencies of employees. The paper shares a practical insight on the implementation of competency mapping for training need analysis. The research is focused on manufacturing units only, whereas there is a huge scope for it to be implemented in service industries also. The paper is an original piece of research where a model has been designed to resolve training issues of manufacturing industries.
Keywords: competency, competency mapping, training, training need assessment, manufacturing
Published: 29.11.2017; Views: 386; Downloads: 85
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Advances in production and industrial engineering
2017, scientific monograph

Abstract: This publication, scientific monograph, offers comprehensive chapter series from scientific researchers conducted by regional authors, authorities in the fields and summarizes the principal scientific contributions. The chapters deal with range topics from optimization techniques in production development, quality in production processes, product and process development, technologies for business development and factors of social and economic development. Edited by two editors with contributions from chapters’ authors, this scientific monograph presents advanced topics for students, educators and practitioners. The editors would like to thank all chapters’ authors for devoting of the research results and expertise with the great enthusiasm. We encourage all of them to continue successful highly valuable cooperation, between Faculty of Mechanical Engineering at the University of Maribor and Faculty of Mechanical Engineering at the Ss. Cyril and Methodius University in Skopje.
Keywords: mechanical engineering, production management, manufacturing, artificial intelligence, process development, economic development
Published: 19.07.2017; Views: 829; Downloads: 301
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Mathematical model for the selection of processing parameters in selective laser sintering of polymer products
Ana Pilipović, Igor Drstvenšek, Mladen Šercer, 2014, original scientific article

Abstract: Additive manufacturing (AM) is increasingly applied in the development projects from the initial idea to the finished product. The reasons are multiple, but what should be emphasised is the possibility of relatively rapid manufacturing of the products of complicated geometry based on the computer 3D model of the product. There are numerous limitations primarily in the number of available materials and their properties, which may be quite different from the properties of the material of the finished product. Therefore, it is necessary to know the properties of the product materials. In AM procedures the mechanical properties of materials are affected by the manufacturing procedure and the production parameters. During SLS procedures it is possible to adjust various manufacturing parameters which are used to influence the improvement of various mechanical and other properties of the products. The paper sets a new mathematical model to determine the influence of individual manufacturing parameters on the polymer product made by selective laser sintering. Old mathematical model is checked by statistical method with central composite plan and it is established that old mathematical model must be expanded with new parameter beam overlay ratio. Verification of new mathematical model and optimization of the processing parameters are made on SLS machine.
Keywords: manufacturing system, inteligent methods, 3D scanning
Published: 12.07.2017; Views: 731; Downloads: 303
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