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  • 1.
    Ilar, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    A method for supporting implementation of semi-automated manufacturing cells: production modelling and parallel process development1997Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 2.
    Ilar, Torbjörn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kinnander, Anders
    Luleå tekniska universitet.
    A new modelling approach to support identification and development of secondary processes in an industrial AMT implementation1997Ingår i: Computer Integrated Manufacturing: Proceedings of the Fourth International Conference: ICCIM '97 21-24 October 1997, Singapore / [ed] A. Sen, Singapore: Springer-Verlag Singapore , 1997Konferensbidrag (Refereegranskat)
  • 3.
    Ilar, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    A simplified modeling approach for human system interaction2008Ingår i: 2008 Winter Simuation Conference: (WSC 2008) ; Miami, Florida, USA, 7 - 10 December 2008 / [ed] Scott J. Mason, Piscataway, NJ: IEEE Communications Society, 2008, s. 903-908Konferensbidrag (Refereegranskat)
    Abstract [en]

    Despite increasing dependency on technology, the importance of humans is expected to increase and to provide a realistic basis for decision support; both technical and organizational processes must be included in simulation models. In a rapidly changing environment, skill development is also important and should be considered when developing simulation models. This paper describes a three step straightforward method that support the implementation of supporting (human dependent) processes, operators competence and competence development using learning curves to obtain a more representative simulation of system performance. The effect on the performance measures are also demonstrated based on a case study of a highly automated press line. The advantages and disadvantages with the proposed method are also discussed.

  • 4.
    Ilar, Torbjörn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    An extended feasibility study to identify laser welding and laser.arc hybrid welding business cases and business models2013Ingår i: 14th NOLAMP Conference: The 14th Nordic Laser Materials Processing Conference, August 26th – 28th 2013, Gothenburg, Sweden / [ed] Alexander Kaplan; Hans Engström, Luleå: Luleå tekniska universitet, 2013, s. 217-226Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The laser research group at Luleå University of Technology has, in collaboration withSwedish industries, performed more than 20 laser welding and laser arc hybrid welding casestudies during the last decade. Most of them can be considered as successful and havedemonstrated improved mechanical properties, new design opportunities and higher weldingproductivity. Nevertheless, very few of the successful case studies have resulted in anindustrial application and the number of industrial implementations is still very limited. Thereare of course several reasons, like company organisation, human factors or lack of experience,but usually it is a rational analysis based on return of investment. The case studies are alsousually limited to one component at one company without any further evaluation and analysisof other business opportunities, i.e. other components/products within the company orforming a cluster of companies in a geographic region. This paper presents an extend analysesof a number of the performed case studies with the objectives to evaluate and identifybusiness cases. Different business models, such as investigate product families for laserwelding within a company and company clusters with common laser welding resource, isevaluated and analysed.

  • 5.
    Matti, Ramiz
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Ilar, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Analysis of laser remote fusion cutting based on a mathematical model2013Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 114, nr 23, artikel-id 233107Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Laser remote fusion cutting is analyzed by the aid of a semi-analytical mathematical model of the processing front. By local calculation of the energy balance between the absorbed laser beam and the heat losses, the three-dimensional vaporization front can be calculated. Based on an empirical model for the melt flow field, from a mass balance, the melt film and the melting front can be derived, however only in a simplified manner and for quasi-steady state conditions. Front waviness and multiple reflections are not modelled. The model enables to compare the similarities, differences, and limits between laser remote fusion cutting, laser remote ablation cutting, and even laser keyhole welding. In contrast to the upper part of the vaporization front, the major part only slightly varies with respect to heat flux, laser power density, absorptivity, and angle of front inclination. Statistical analysis shows that for high cutting speed, the domains of high laser power density contribute much more to the formation of the front than for low speed. The semi-analytical modelling approach offers flexibility to simplify part of the process physics while, for example, sophisticated modelling of the complex focused fibre-guided laser beam is taken into account to enable deeper analysis of the beam interaction. Mechanisms like recast layer generation, absorptivity at a wavy processing front, and melt film formation are studied too.

  • 6.
    Kinnander, Anders
    et al.
    Luleå tekniska universitet.
    Ilar, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Eriksson, Ulf
    Competence requirements and their impact on manufacturing system performance1998Ingår i: CIRP annals, ISSN 0007-8506, E-ISSN 1726-0604, Vol. 47, nr 1, s. 385-388Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Research into `Next generation manufacturing systems' stresses the use of semi-automated systems to handle short product life cycles and customer oriented production. Despite increasing dependency on technology, the importance of humans is expected to increase and to provide a realistic basis for decision support, both technical and organizational processes must be included in simulation models. In a rapidly changing environment, skill development is also important and should be considered when developing simulation models. This paper describes two case studies where competence and skill development were modelled using learning curves to obtain a more representative simulation of system performance.

  • 7.
    Ilar, Torbjörn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Magnusson, Claes
    Development of a flexible manufacturing system with high power laser1986Ingår i: Proceedings of the 5th International Conference on Flexible Manufacturing Systems: 3-5 November 1986, Stratford-upon-Avon, U.K / [ed] Keith Rathmill, Bedford :: IFS , 1986, s. 343-52Konferensbidrag (Refereegranskat)
    Abstract [en]

    It is a great opportunity for the Laser Research Group at the University of Lulea to participate in the development of a flexible manufacturing system including a laser welding cell, in co-operation with a small Swedish company. The laser research group have, in the progress of the system build-up, contributed with welding tests of the work-pieces, design of a flexible laser welding cell including fixture units and material handling equipment. We have also given our recommendation of the purchase of a laser-system. This paper presents the planning of this flexible laser processing cell, where the additional advantages with laser welding and flexibility are the main objectives with the installation.

  • 8.
    Mishra, Pragya
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ilar, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Brueckner, Frank
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Energy efficiency contributions and losses during selective laser melting2018Ingår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 30, nr 3, artikel-id 032304Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Selective Laser Melting technique, SLM, requires remelting of adjacent tracks to avoid cavities and other imperfections. Usually, very conservative process parameters are chosen to avoid imperfections, resulting in a low building rate. The process efficiency relates the energy required for the generation of a new track to the laser beam power. For SLM this efficiency is determined by the process parameters, specifically hatch distance, layer depth and scanning speed, independent of the resulting process mechanisms. For SLM the process efficiency often very low, typically 2‑20%. Apart from beam reflection losses of normally 50-60%, significant energy losses result from the remelting of surrounding layers. Some areas can even experience multiple remelting cycles. Further losses originate inevitably from substrate heating. A simplified mathematical model of the track cross section and the corresponding layer overlap geometry has been developed, to analyze the different loss contributions from remelting with respect to the process parameters. The model explains why increasing the hatch distance or the layer depth proportionally increases the process efficiency. However, these increases are limited by cavity formation. The cross section of the overlapping tracks generated by SLM can be regarded as an experimental fingerprint linked to the process conditions. The track cross section geometries can significantly fluctuate, in terms of area and coordinate position. The fluctuations require additional reduction of the hatch distance or layer depth, to ensure robust, cavity-free processing. Examples are presented for stainless steel where a 180 W laser beam has led to a process efficiency of 5-11%, proportional to a hatch distance that was increased from 50 to 110 µm, for 40 µm powder layer depth, at a speed of 50 m/min.

  • 9.
    Kaplan, Alexander
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Frostevarg, Jan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Ilar, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Bang, Hee-Seon
    Chosun University, Department of Welding & Joining Science Engineering.
    Bang, Han-Sur
    Chosun University, Department of Welding & Joining Science Engineering.
    Evolution of a Laser Hybrid Welding Map2015Ingår i: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 78, s. 2-13Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Laser arc hybrid welding combines the advantages but also the complex physical mechanisms of gas metal arc welding and laser keyhole welding. From manifold mainly experimental but also theoretical research results a map with versatile functions was initiated for the first time. The purpose is to survey the overall context and to facilitate navigation to the various phenomena that are shown through case studies accompanied by theoretical explanations and guidelines for optimization. Though not complete, the map enables systematic and graphical navigation to relevant publications. Based on a fundamental structure of the map, which was decided early, it is inherently extendable in the future by adding existing and new knowledge, also from other research groups, enabling evolution. The fundament of the map structure comprises gouge thickness, joint type and metal grade, in coherence with product and weld designers’ starting points. The next hierarchy level of the map offers options in the joint type as well as in hybrid welding techniques. The latter contains techniques like double-sided welding, pulse shaping management of the arc or laser, CMT arcs, tandem arcs, or remelting of undercuts. In addition to laser-arc hybrid welding, other hybrid laser techniques like multilayer hot-wire laser welding of narrow gaps or hybrid laser friction stir welding can be taken into account. At the other end of the hierarchy, the map offers via a database-like archive electronic navigation to research results like weld macrographs, high speed imaging or numerical simulation results of the welding process.

  • 10.
    Engström, Hans
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Ilar, Torbjörn
    Flexibla tillverkningssystem med högeffektslaser1987Rapport (Övrigt vetenskapligt)
  • 11. Bylesjö, Hans
    et al.
    Eriksson, U.
    Ilar, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kinnander, Anders
    Luleå tekniska universitet.
    Holistic design of manufacturing systems1995Ingår i: Colloquium / Institution of Electrical Engineers, ISSN 0963-3308, nr 238, s. 4/1-4/5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To design, implement and operate an efficient manufacturing organizations today, a systems view is necessary; this picture is further complicated as manufacturing systems are also dynamic in nature. Holistic design of manufacturing systems, that is using dynamic systems thinking based on business strategy, can help to optimize technical, organizational and human factors in new system implementation. During the last decade numerous packages for the simulation of manufacturing systems have been developed as a support for the analysis and design of these systems. Simulation has traditionally concentrated on details, which is important at the design stage, but many of the total system aspects such as machine, organization and human aspects are lost. This paper presents the concept of a virtual arena as a means of approaching the holistic design of manufacturing systems; the literature relating to this concept is also presented in outline. Special interest is placed upon work relating to the total or holistic view of manufacturing organizations. Current research initiatives in Scandinavia are also presented.

  • 12. Ilar, Torbjörn
    et al.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Hybright - generic understanding of the mechanical strength of hybrid welds2007Ingår i: 11th NOLAMP Conference: 11th NOLAMP Conference in Laser Processing of Materials ; Lappeenranta, August 20 - 22, 2007 / [ed] Veli Kujanpää, Lappeenranta: Lappeenranta University of Technology Press, 2007Konferensbidrag (Refereegranskat)
  • 13.
    Pocorni, Jetro
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Ilar, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Schwarz, A.
    Laser Expertise Ltd., Acorn Park Industrial Estate, Nottingham.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Measuring the State-of-the-Art in Laser Cut Quality2013Ingår i: 14th NOLAMP Conference: The 14th Nordic Laser Materials Processing Conference, August 26th – 28th 2013, Gothenburg, Sweden / [ed] Alexander Kaplan; Hans Engström, Luleå: Luleå tekniska universitet, 2013, s. 101-108Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    This paper discusses the strategy appropriate to investigating the state of the art of laser cutting from an industrial point of view. The importance of creating the samples in a high quality industrial environment is emphasised and preliminary results are presented.

  • 14. Ilar, Torbjörn
    et al.
    Powell, John
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Modelling, simulation and analyses of systems with breakdown imposed scrapping2009Ingår i: Journal of Simulation, ISSN 1747-7778, Vol. 3, nr 2, s. 107-113Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study shows that, for many manufacturing processes (such as welding and injection moulding), a machine breakdown will result in the scrapping of a component, and goes on to explain the effect that this can have on process simulation models. Breakdown-related scrapping events are ignored by commercially available process simulation packages and this reduces their usefulness in decision support. This paper explains the different types of breakdown/scrapping dynamic possible and clearly demonstrates the scrapping dynamics effect on one of the major performance measures in LEAN-based manufacturing systems, namely the Overall Equipment Effectiveness. The paper also demonstrates the effect on model accuracy of a miss interpretation of part scrap behaviour or none deliberately simplified modelling of part scrap. This uncertainty in model accuracy will reduce the usefulness of the simulation model as a decision support tool.

  • 15.
    Matti, Ramiz
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Ilar, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Modelling the cutting geometry for laser remote fusion cutting of metals2013Ingår i: 14th NOLAMP Conference: The 14th Nordic Laser Materials Processing Conference, August 26th – 28th 2013, Gothenburg, Sweden / [ed] Alexander Kaplan; Hans Engström, Luleå: Luleå tekniska universitet, 2013, s. 121-132Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The high brilliance fibre and disc lasers that were developed during the last decade providelong range focusing that enables remote laser techniques without assist gas, including remotelaser welding and cutting. In combination with industrial robots these lasers offer industry ahighly flexible production solution, including quick positioning with scanner optics across aworkpiece. The paper presents the state of the art in the field of remote metal cutting with thefocus on analytical models and the physical process analyses. Several remote cuttingtechniques can be distinguished, in particular remote ablation cutting, remote fusion cuttingand remote gravity cutting. The three-dimensional cutting process and kerf geometry isconcluded to an extensive impact on the melted metal flow and the cutting processperformance. A semi-analytical mathematical model has been developed that enables tocalculate and analyse the cutting front with respect to absorption, heat conduction, recoilpressure and melt film flow. Beside analysing the remote laser fusion cutting process, theregimes and their transitions from remote fusion cutting to keyhole laser

  • 16.
    Ilar, Torbjörn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kinnander, Anders
    Luleå tekniska universitet.
    Modelling the impact of supporting processes on manufacturing system performance: experiences from an industrial case study1999Ingår i: New supporting tools for designing products and production systems: The 32nd CIRP International Seminar on Manufacturing Systems : proceedings : May 24-26,1999, Leuven, Belgium / [ed] H. van Brussel; J.P. Kruth; B. Lauvers, Heverlee: Katholieke Univ. Leuven , 1999, s. 505-510Konferensbidrag (Refereegranskat)
  • 17.
    Moradi, Mahmoud
    et al.
    Department of Mechanical Engineering, Faculty of Engineering, Malayer University.
    Salimi, Nahid
    Department of Computer Engineering, Malayer Branch, Islamic Azad University.
    Ghoreishi, M.
    Faculty of Mechanical Engineering, K.N. Toosi University of Technology, Tehran.
    Abdollahi, Hadi
    Department of Mechanical Engineering, Urmia University of Technology.
    Shamsborhan, Mahmoud
    Department of Engineering, Mahabad Branch, Islamic Azad University.
    Frostevarg, Jan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Ilar, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Parameter dependencies in laser hybrid arc welding by design of experiments and by a mass balance2014Ingår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 26, nr 2, artikel-id 22004Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reinforcement, undercut, and root drop-through during laser hybrid arc welding of steel were studied in dependence of gap width, welding speed, and wire feeding rate. Generalized trends were obtained through design of experiments. Most of the trends could be explained by a mass balance while some parameter impacts relied on more complex mechanisms. In particular, different levels of complexity of parameter dependencies were distinguished, ranging from monotonous behaviour to maxima and to changing signs of the trends. The findings are of high practical relevance to optimize the process with respect to the weld quality. Moreover, the potential and limits of the design of experiments method, of a mass balance, and of the matrix flow chart method are discussed.

  • 18.
    Ilar, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Production simulation as a management tool2008Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis focuses on process simulation and modelling in the context of production engineering. The thesis is presented in the form of seven papers which range in content from the holistic analysis of the application of modelling (papers 1-5) to a detailed examination of some of the areas of weaknesses in commercially available software (papers 6 and 7). The papers can be summarised as follows; Paper 1, The Use of Virtual Reality Tools in Complex Work Cell Implementation - Experiences from Scandinavian Industry; The main contribution of this work is a demonstration of the ability of process modelling tools to predict risks and disturbances during the implementation of robotic based manufacturing cells. Paper 2: The Virtual Arena; experiences from the first industrial application of a new AMT implementation methodology; The main contribution here is a preliminary outline of a methodological approach for the application of process modelling tools in the development and implementation of AMT (advanced manufacturing systems). Paper 3: A new Modelling Approach to Support Identification and Development of Secondary Processes in an Industrial AMT Implementation; The main contribution of this paper is a demonstration of extended process mapping and a modelling approach involving both main and supporting processes and the importance of staff competence. Paper 4: Competence requirements and their impact on manufacturing system performance; This paper explains how staff competence can be implemented into process models to obtain a more representative simulation of overall system performance. Paper 5: Modelling the impact of supporting processes on manufacturing system performance - experiences from an industrial case study. This paper demonstrates the use of the method introduced in paper 5 and its applicability in small cell configurations and SMEs. Paper 6: The effect of process interruption and scrap on production simulation models; This paper investigates an area of weakness in commercially available simulation software; the treatment of breakdown related scrapping events. The paper explains the different types of breakdown/scrapping dynamic possible for any given machine and demonstrates the effect of these scrapping dynamics on the Overall Equipment Effectiveness. The paper demonstrates (for the first time) the need for careful analysis and the correct choice of breakdown/scrapping dynamics in simulation models. Paper 7: Simulation of production lines involving unreliable machines: the importance of machine position and breakdown statistics; This paper the importance of choosing the correct values and statistical distributions for breakdown frequency and duration when simulating production line productivity. The pitfalls of making the wrong choices from those offered in commercially available software are pointed out. The paper also demonstrates that the common technique of reducing the standard deviation of variables to obtain a more deterministic model can lead to inaccurate results. Also, it is demonstrated that the productivity of a production line can be improved by simply re-arranging the order of unreliable machines in the line.

  • 19.
    Ilar, Torbjörn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Eriksson, Ingemar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Root humping in laser welding: an investigation based on high speed imaging2012Ingår i: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 39, s. 27-32Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Regular drop formation (humping) along the weld root during laser welding was studied by high speed imaging of the melt pool underneath the workpiece. The formation of droplets towards the rear of this weld pool was seen to be primarily caused by the pumping of melt from the bottom of the keyhole and the influence of gravity drawing melt into a sagging hump. This is a different process from the one which creates humps on the top surface of welds.

  • 20.
    Ilar, Torbjörn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Simulation of production lines involving unreliable machines: the importance of machine position and breakdown statistics2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper demonstrates the importance of choosing the correct statistical distributions for breakdown frequency and duration when simulating production line productivity. Statistical distributions with a wide range tend to reduce the productivity of the line. Also, it is demonstrated that the productivity of a production line can be improved simply by re-arranging the order of unreliable machines in the line. If the line consists of similar or exchangeable machines, productivity can improved if the most unreliable machines are placed towards the end of the line.

  • 21. Ilar, Torbjörn
    et al.
    Powell, John
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Simulation of production lines: The importance of breakdown statistics and the effect of machine position2008Ingår i: International Journal of Simulation Modelling, ISSN 1726-4529, Vol. 7, nr 4, s. 176-185Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper demonstrates the importance of choosing the correct values and statistical distributions for breakdown frequency and duration when simulating production line productivity. Statistical distributions with a wide range tend to reduce the productivity of the line but this trend can be disrupted by poor choice of mean values for the variables in question. Also, it is demonstrated that the productivity of a production line can be improved simply by re-arranging the order of unreliable machines in the line. If the line consists of similar or exchangeable machines, productivity can improved if the most unreliable machines are placed towards the end of the line. The paper also demonstrates the risks of reduction of the standard deviation to obtain a more deterministic model.

  • 22.
    Ilar, Torbjörn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    The effect of process interruption and scrap on production simulation models2007Ingår i: CARV 2007: 2nd International Conference on Changeable, Agile, Reconfigurable and Virtual Production, Toronto, Ontario, Canada, july, 23-24 2007 : today's reaction, tomorrow's challenge / [ed] Michael F. Zäh; Hoda A. ElMaraghy, CARV , 2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    This study shows that, for many manufacturing processes (such as welding and injection moulding), a machine breakdown will result in the scrapping of a component, and goes on to explain the effect that this can have on process simulation models. Breakdown related scrapping events are ignored by commercially available process simulation packages and this reduces their usefulness in decision support. This paper explains the different types of breakdown/scrapping dynamic possible and provides equations which can be used to describe them in future generations of simulation software. This work clearly demonstrates the scrapping dynamics effect on one of the major performance measures in LEAN based manufacturing systems, namely the Overall Equipment Effectiveness.

  • 23.
    Kaplan, Alexander
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Barsoum, Z.
    Royal Institute of Technology, Department of Aeronautical and Vehicle Engineering, Stockholm.
    Alam, Md. Minhaj
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Ilar, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    The impact of weld shape on fatigue cracking of eccentric geometry laser hybrid welds under bending load2010Ingår i: Istanbul IIW 2010: proceedings of the International Conference on Advances in Welding Science & Technology for Construction, Energy & Transportation, AWST 2010, Swissôtel "The Bosphorus", Istanbul/Turkey, from July 15 - 16. July, 2010 ; [is being held in conjunktion with the 63rd Annual Assembly & International Conference of the International Institute of Welding] / [ed] Mustafa Kocak, Istanbul: Ridgeview Publishing Company, 2010, s. 253-259Konferensbidrag (Refereegranskat)
    Abstract [en]

    A butt joint of two 10 mm thick stainless steel plates, but 5 mm vertically eccentric to each other, was laser hybrid welded. The weld experiences four point bending fatigue load such that the root stress remains compressive. Thus only the stress formation at the top of the weld was studied, both by fatigue testing and by linear elastic fracture mechanics analysis. The location of the peak stress for crack initiation as well as the direction and speed of crack propagation can be well explained. Weld throat depth, weld toe radii and surface roughness compete against each other for determining the peak stress. It was also shown why occasional lack of fusion has only limited impact on the peak stress and fatigue life. Optimization of the laser beam contribution is responsible for full penetration and for avoiding lack of fusion. Optimization of the MIG-process is essential, as governing the top shape. Beside stress analysis including the topography, the propagation of the cracks along surface resolidification ripples was an indicator that surface roughness has essential impact. Several approaches were developed and studied for systematic documentation and generalization of the discovered knowledge.

  • 24.
    Ilar, Torbjörn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Legge, H.
    Bylesjö, U.
    Kinnander, Anders
    The Virtual Arena: Experiences from the First Industrial Application of a New AMT Implementation Methodology1996Ingår i: 29th International Symposium on Automotive Technology and Automation: Florence, Italy, 3rd - 6th June 1996; the largest European automotive forum with international participation: Virtual vehicle design : it's sample with Saber, the leaders in automotive mechatronics simulation ; proceedings / [ed] Dieter Roller, Croydon: Automotive automation , 1996, s. 299-308Konferensbidrag (Refereegranskat)
  • 25.
    Ilar, Torbjörn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Legge, D.
    Kinnander, Anders
    Luleå tekniska universitet.
    Use of Virtual Reality Tools in Complex Work Cell Implementation: Experiences from Scandinavian Industry1996Konferensbidrag (Refereegranskat)
  • 26. Powell, John
    et al.
    Ilar, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Frostevarg, Jan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Torkamany, Mohammad
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Na, Suck-Joo
    Department of Mechanical Engineering, KAIST, Daejeon.
    Petring, Dirk
    Fraunhofer-Institute for Laser Technology, Aachen.
    Zhang, Linjie
    Department of Physics, Xi'an Jiaotong University.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Weld root instabilities in fiber laser welding2015Ingår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 27, nr Suppl. 2, artikel-id S29008Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fiber laser welding and fiber laser-arc hybrid welding have been developed into very useful industrial processes over the past few years. However, the use of fiber lasers can be associated with quality problems at the weld root such as intermittent penetration, melt ejection, and humping. This paper explains the mechanisms which create these instabilities and suggests a repair technique which would alleviate the problems in some cases. The main difference between fiber and CO2 laser welding is that during fiber laser welding there is a strong downward thrust on the melt in the keyhole.(This is not the case during CO2 laser welding.) The downward thrust on the melt is generated as a result of the fiber laser evaporating the top faces of bumps on the melt surface. The downward flow has two main effects;(a) the melt can achieve velocities which result in melt ejection from the root of the weld-which can result in intermittent penetration,(b) the supply of hot metal to the bottom of the weld makes the process much more thermally uniform at the top and bottom of the weld. This uniformity means that the melt is extended backward several millimeters on the top and bottom surfaces-which can result in melt humping in the weld root as well as on the top surface. This paper examines these weld root instabilities and also describes a technique of weld root remelting which has been shown to be effective in smoothing out the root of the weld to improve its tensile and fatigue properties

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