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  • 1.
    Beno, Tomas
    et al.
    University West, Trollhättan, Sweden.
    Repo, Jari
    University West, Trollhättan, Sweden.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    The use of machine tool internal encoders as sensors in a process monitoring system2013In: International Journal of Automation Technology, ISSN 1881-7629, E-ISSN 1883-8022, Vol. 7, no 4, p. 410-417Article in journal (Refereed)
    Abstract [en]

    Tool wear in machining changes the geometry of the cutting edges, which affects the direction and amplitudes of the cutting force components and the dynamics in the machining process. These changes in the forces and dynamics are picked up by the internal encoders and thus can be used for monitoring of changes in process conditions. This paper presents an approach for the monitoring of amulti-toothmilling process. The method is based on the direct measurement of the output from the position encoders available in the machine tool and the application of advanced signal analysis methods. The paper investigates repeatability of the developed method and discusses how to implement this in a process monitoring and control system. The results of this work show that various signal features which are correlated with tool wear can be extracted from the first few oscillating components, representing the low-frequency components, of the machine axes velocity signatures. The responses from the position encoders exhibit good repeatability, especially short term repeatability while the long-term repeatability is more unreliable.

  • 2.
    El-Amine, Karim
    et al.
    Örebro University, School of Science and Technology. Suzuki Garphyttan AB, Garphyttan, Sweden.
    Larsson, Joakim
    Örebro University, School of Science and Technology. Department of Mechanical Engineering.
    Pejryd, Lars
    Örebro University, School of Science and Technology. Department of Mechanical Engineering.
    Experimental comparison of roller die and conventional wire drawing2018In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 257, p. 7-14Article in journal (Refereed)
    Abstract [en]

    In this work, the application of roller dies as an alternative to conventional dies in the wire drawing process – claimed in earlier works to offer many advantageous improvements – is evaluated. To this end, experimental procedures using a single stage drawing machine were conducted, drawing low and medium carbon steel wires using both roller dies and conventional dies. The two reduction processes were compared with respect to drawing force and the resulting wire temperature. Also the mechanical properties of the drawn wires were investigated. The obtained results have not shown any large differences between the two processes, and the main improvement using the roller die method was a better wire surface. This advantage was counteracted with downsides including higher wire temperature and lower strain at fracture.

    Moreover, a formula to theoretically calculate drawing force for the conventional drawing process was modified and used to calculate drawing force for the two reduction steps in the roller die cassette. The results showed that the proportion of inhomogeneous deformation was much higher in the rolling process as compared to the conventional process.

    In view of the outcomes in this work, the alternative of drawing wire through roller dies was not considered to be offering more improvements with respect to the conventional drawing method.

  • 3.
    El-Amine, Karim
    et al.
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Study and optimization of changeover procedures in wire drawing2016In: 7th Swedish Production Symposium (SPS 16), 2016Conference paper (Refereed)
  • 4.
    Hällgren, Sebastian
    et al.
    Örebro University, School of Science and Technology. Saab Dynamics Development, Karlskoga, Sweden.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Ekengren, Jens
    Örebro University, School of Science and Technology.
    3D data export for Additive Manufacturing - improving geometric accuracy2016In: 26th CIRP Design Conference, Amsterdam: Elsevier, 2016, p. 518-523Conference paper (Refereed)
    Abstract [en]

    3D data exchange between different CAD systems and from design to manufacturing has largely moved to ISO STEP based formats. The Additive Manufacturing (AM) process today requires an approximate, planar triangle tessellated 3D model as an input. Improving accuracy in STL file exports is done differently in different CAD systems. Poor tessellation accuracy results in built parts with poor geometric accuracy because of errors in source data. In this study, results of tessellation from six different CAD systems are compared. Roundness accuracy for the different settings is calculated. Results show that tessellation effects may be visible even when roundness requirements are fulfilled. A method for 3D data exchange for AM using STEP and geometric requirements is proposed until better accuracy AM formats can be used.

  • 5.
    Hällgren, Sebastian
    et al.
    Örebro University, School of Science and Technology. Saab Dynamics Development, Karlskoga, Sweden.
    Pejryd, Lars
    Örebro University, School of Science and Technology. Sch Sci & Technol, Univ Orebro, Orebro, Sweden.
    Ekengren, Jens
    Örebro University, School of Science and Technology.
    Additive Manufacturing and High Speed Machining - Cost comparison of short lead time manufacturing methods2016In: 26th CIRP Design Conference, Amsterdam: Elsevier, 2016, p. 384-389Conference paper (Refereed)
    Abstract [en]

    Additive Manufacturing (AM) using Powder Bed Fusion (PBF) allows part with abstract shapes, that otherwise would need costly tooling, to be manufactured with short lead time. In this study AM build time simulations are used to predict series part cost for eight parts that are possible to cut from rod blanks using High Speed Machining (HSM). Results indicate that when the part shape can be cut from rod blanks, AM is more expensive than HSM even for series of one. If post processing machining is added to the printed AM blank part, the cost difference increases further. Finally, the model is used to predict part-cost in series production if print speed increases, if machine cost is reduced or if part mass is reduced as a result of redesign for AM.

  • 6.
    Hällgren, Sebastian
    et al.
    Örebro University, School of Science and Technology. Saab Dynamics Development, Karlskoga, Sweden.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Ekengren, Jens
    Örebro University, School of Science and Technology.
    (Re)Design for Additive Manufacturing2016In: 26th CIRP Design Conference, Amsterdam: Elsevier, 2016, p. 246-251Conference paper (Refereed)
    Abstract [en]

    3D-printing has been used to create prototypes during the development phase for more than 20 years. Now, functional parts can be printed directly in specific metal powders using similar layer-by-layer techniques. The additive method is unlike traditional mass production manufacturing methods in many ways, creating new possibilities for designers to realise new and different design ideas previously impossible to manufacture. When products are mass produced, there is a desire to improve manufacturability. This is traditionally done by a designer with knowledge about certain manufacturing methods altering design choices to make it cheaper to manufacture.

    This paper shows different design for AM (DfAM) methods where performance and part cost are both of interest. It adds to existing research by classifying design for additive manufacturing in two different classes; process-driven and designer-driven shaping of parts. A cost-prediction model for Selective Laser Melting (SLM) printed parts is suggested as an initial step to choose parts for redesign from an economical perspective. A case study of a missile launcher beam redesigned for additive manufacturing using three different approaches is presented. Differences and similarities in design methods are discussed and the redesigned parts are compared for mass and cost. It is shown that redesigning for AM can reduce mass but depending on part size and print speed, the part can become more expensive than the original design, creating a need to know the customer value of what the redesigned part provides, in this case, the value of reduced mass.

  • 7.
    Jansson, Anton
    et al.
    Örebro University, School of Science and Technology.
    Ekengren, Jens
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Numerical analysis of compression strength in network structures based on trusses, and periodic surfaces aimed for additive manufacturing2018In: Proceedings of the International Conference on Progress in Additive Manufacturing / [ed] C.K. Chua, W. Y. Yeong, M. J. Tan, E. J. Liu, S. B. Tor, Singapore: Nanyang Technological University , 2018, Vol. 1, p. 328-333, article id D45P4RConference paper (Refereed)
    Abstract [en]

    In this paper, the compressive response for a number of truss- and surface-based networks with equal relative density was compared. The effect of errors in the structures were also investigated. The results show that surface networks are, in general, more efficient structures than truss-lattices in compression. The results also show that surface networks are significantly more resilient to fabrication errors than their truss-lattice counterparts.

  • 8.
    Jansson, Anton
    et al.
    Örebro University, School of Science and Technology.
    Ekengren, Jens
    Örebro University, School of Science and Technology.
    Zekavat, Amir Reza
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Effects of X-ray Penetration Depth on Multi Material Computed Tomography Measurements2016In: iCT 2016, NDT.net , 2016, p. 143-150Conference paper (Refereed)
    Abstract [en]

    The complexity of today’s products and materials is ever increasing. There is a demand on the industry to produce lighter, stronger, and more precise products. A common practice to achieve such products is to combine different materials to enhance strengths and reduce weaknesses; multi material products. Fabricating complex parts using multi materials does, however, lead to an increased difficulty in metrological verification and material characterisation. The use of computed tomography is today widespread within the industry, providing new possibilities for internal measurements, but there are still many uncertainties associated with the method. It is well known that large variations in density of multi materials greatly affects the contrast obtained by computed tomography, resulting in difficulties to scan and acquire reliable data from certain material setups.In this work the effects on internal measurements as a consequence of differences in X-ray penetration depth have been studied with regards to multi material setups. The main interest was the ability to acquire measurements from internal features of material compositions that are commonly used in the industry. In the result, difficulties and uncertainties associated with computed tomography of multi materials are highlighted and suggestions on how to reduce problems and obtain a more reliable test method are discussed.

  • 9.
    Jansson, Anton
    et al.
    Örebro University, School of Science and Technology.
    Hermanek, Petr
    University of Padova, Vicenza, Italy.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Carmignato, Simone
    University of Padova, Vicenza, Italy.
    Multi-material gap measurements using dual-energy computed tomography2018In: Precision engineering, ISSN 0141-6359, E-ISSN 1873-2372, Vol. 54, p. 420-426Article in journal (Refereed)
    Abstract [en]

    X-ray computed tomography is a highly versatile investigation method with applications in a wide range ofareas. One of the areas where the technique has seen an increased usage, and an increased interest from industry,is in dimensional metrology. X-ray computed tomography enables the measurement of features and dimensionsthat are difficult to inspect using other methods. However, there are issues with the method when it comes tomeasurements of objects that consist of several materials. In particular, it is difficult to obtain accurate computedtomography results for all materials when the attenuation of materials differs significantly. The aim of this workwas to measure small air gaps between different materials using dual-energy X-ray computed tomography. Thedual-energy method employed in this work uses two energy spectra and fuses the data in the projections spaceusing non-linear fusion. The results from this study show that the dual-energy method used in this work was ableto capture more measurements than regular absorption computed tomography in the case of specimens withhighly different attenuation, enabling, in particular, the measurement of smaller gaps. The contrast-to-noise ratiowas also increased significantly with the use of dual-energy.

  • 10.
    Jansson, Anton
    et al.
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    A dual-energy approach for improvement of the measurement consistency in computed tomography2016In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 27, no 11, article id 115013Article in journal (Refereed)
    Abstract [en]

    Computed tomography is increasingly adopted by industries for metrological and material evaluation. The technology enables new measurement possibilities, while also challenging old measurement methods in their established territories. There are, however, uncertainties related with the computed tomography method. Investigation of multi-material components with, in particular, varying material thickness can result in unreliable measurements. In this paper the effects of multi-materials, and differing material thickness, on computed tomography measurement consistency has been studied. The aim of the study was to identify measurement inconsistencies and attempt to correct these with a dual-energy computed tomography approach. In this pursuit, a multi-material phantom was developed, containing reliable measurement points and custom-ability with regards to material combinations. A dual-energy method was developed and implemented using sequential acquisition and pre-reconstruction fusing of projections. It was found that measurements made on the multi-material phantom with a single computed tomography scan were highly inconsistent. It was also found that the dual-energy approach was able to reduce the measurement inconsistencies. However, more work is required with the automation of the dual-energy approach presented in this paper since it is highly operator dependant.

  • 11.
    Jansson, Anton
    et al.
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Characterisation of additive manufacturing metal: carbon-fibre composite bond by dual-energy computed tomography2017In: EUSPEN, Conference Proceedings, Special Interest Group: Dimensional Accuracy and Surface Finish in Additive Manufacturing, Octrober 2017, KU Leuven, Belgium: EUSPEN , 2017, p. 189-192Conference paper (Refereed)
    Abstract [en]

    Joining of dissimilar materials is a topic of high interest for the industry. The ability to seamlessly join materials with significant differences in properties would advance the development of efficient designs and concepts within many fields. In this work, bonds between aluminium and carbon-fibre reinforced plastic have been studied. The aluminium side of the bonds were fabricated using classical methods (milling) and additive manufacturing. Two types of bonds were fabricated using additive manufacturing, one flat, relying on the rough surface for adhesion in the bond, and the other with surface features designed to hook into the carbon-fibre plies. All the bonds were fabricated using wet layup of carbon-fibre, the idea was that the aluminium parts would bond to the plastic composite in one step. The bonds were characterised using dual-energy computed tomography. The method used in this work was non-linear and based around fusing of projections acquired with different energy spectra. The mechanical strength of the bonds was also evaluated, both through tensile tests and four-point bending.It was found that the bonds including additive manufactured aluminium was stronger than the milled samples in general. In the computed tomography data, it could be seen that the adhesion in those bonds were better, most likely due to the rough surface. The strongest bonds were those with additive manufacturing surface features. However, the computed tomography data revealed that these bonds have difficulties with integration between the surface features and the carbon-fibre plies.

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  • 12.
    Jansson, Anton
    et al.
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Characterisation of carbon fibre-reinforced polyamide manufactured by selective laser sintering2016In: Additive Manufacturing, ISSN 2214-8604, Vol. 9, p. 7-13Article in journal (Refereed)
    Abstract [en]

    Polymers and reinforced plastics are employed in various load-bearing applications, from household objects to aerospace products. These materials are light, strong, and relatively cheap but can be difficult to form into complex geometries. However, the development of additive manufacturing processes has made it easier to manufacture reinforced plastics in complex shapes. The aim of this work was to study the internal features and mechanical properties of carbon fibre-reinforced polyamide (CF/PA12) fabricated with the additive manufacturing technique of selective laser sintering. The test specimens were studied using computed tomography to analyse the internal geometry, and the material proved to be highly porous. Moreover, the test specimens revealed an internal layered structure, which was found to have a great effect on the tensile properties of the material. The results highlight that there is room for further optimisation of the manufacturing parameters for CF/PA12, because the layered structure makes it challenging to design end user parts with acceptable mechanical properties.

  • 13.
    Jansson, Anton
    et al.
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Dual-energy computed tomography investigation of additive manufacturing aluminium: carbon-fibre composite joints2019In: Heliyon, ISSN 2405-8440, Vol. 5, no 2, article id e01200Article in journal (Refereed)
    Abstract [en]

    In this work, aluminium–carbon-fibre reinforced plastic joints have been studied. Three types of samples were designed as double lap joints where the aluminium inserts were fabricated using both classical methods (milling) and additive manufacturing. Two versions of the joint were fabricated using additive manufacturing, one flat, and the other with small teeth designed to hook into the carbon-fibre plies. The joints were characterised using a non-linear, dual-energy computed tomography method to evaluate the bond between the composite and the metal inserts. The mechanical strength of the bonds was evaluated, both through tensile tests and four-point bending. A simple finite element model was used to discuss the joints behaviour. It was found that the joints fabricated using additive manufactured inserts were more resistant to peel stress than the milled inserts. In four-point bending tests the moment that the joint could withstand was increased by roughly 300% with the use of additive manufacturing and 400% with the use of additive manufacturing and small teeth. However, in tensile tests it was found that the teeth design reduced the maximum load capacity of the joints by roughly 30% due to porosity. Further, it was found that the additive manufactured samples did not add to the capability of withstanding shearstress. The information gained with the dual-energy computed tomography method was highly valuable as the behaviour of the joints would have been difficult to explain without the porosity information.

    Download full text (pdf)
    Dual-energy computed tomography investigation of additive manufacturing aluminium–carbon-fibre composite joints
  • 14.
    Jansson, Anton
    et al.
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    In-situ computed tomography investigation of the compression behaviour of strut, and periodic surface lattices2019In: iCT 2019 / [ed] Rolf Diederichs, NDT.net , 2019, p. 221-227Conference paper (Refereed)
    Abstract [en]

    In this work the effects of fabrication errors in the Body Centered Cubic strut lattice, and the periodic surface lattice Schwarz Diamond has been investigated. The lattices were both fabricated as-is and with induced errors to evaluate the lattices response to fabrication errors. The behaviour of the lattices were studied using compression test and in-situ computed tomography investigation. The results show that the Schwarz Diamond lattices in general are stronger than the Body Centered Cubic lattices in all of the measured aspects. Often up to five times stronger. It was also found that the elastic behaviour of the Schwarz Diamond lattices were mainly unaffected by fabrication errors while the Body Centered Cubic lattices experienced severe losses in performance. The behaviour of the lattices under compression could be followed using computed tomography which aided in the understanding of their behaviour.

    Download full text (pdf)
    In-situ computed tomography investigation of the compression behaviour of strut, and periodic surface lattices
  • 15.
    Jansson, Anton
    et al.
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Surface vs Truss lattice networks, benefits and limitations2018In: NAFEMS nordic: Exploring the Design Freedom of Additive Manufacturing through Simulation, NAFEMS , 2018, p. 217-218Conference paper (Refereed)
    Abstract [en]

    The use of additive manufacturing is growing rapidly among industries within many different fields of fabrication. The benefits of applying additive manufacturing can be many and an application that have received special interest is the ability to design lightweight components. Lightweight components can be fabricated with additive manufacturing with the use of lattices that have a high stiffness to weight ratio and topology optimised, complex, designs. The most commonly used lattices today are based on trusses, however, there is also the possibility to generate lattices based around continuous surfaces. In this study, the properties of the popular body-centred-cubic lattice are compared the properties of the lesser known Schwartz diamond surface lattice. The mechanical compression properties, the fabrication processes, and the possibilities of the lattices are discussed and analysed.

  • 16.
    Jansson, Anton
    et al.
    Örebro University, School of Science and Technology.
    Zekavat, Amir Reza
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Measurement of internal features in additive manufactured components by the use of computed tomography2015Conference paper (Refereed)
    Abstract [en]

    Additive manufacturing (AM) is a set of manufacturing processes currently in rapid development providing designersnew freedoms in their designs. One distinct difference from other manufacturing methods is the ability to makecomplex internal features which can be of great benefit for applications in many industries. These features can bechannels, cavities, filled or not filled with powder, parts in parts etc. In order for these advantages to be industriallyapplicable there is a need for robust verification methods for these internal features. X-ray computed tomography (CT)holds the promise of being one of the few powerful tools for non-destructive imaging of internal features. In this work,selective laser sintering (SLS) has been used to manufacture parts of a complex geometry containing internal cavities.The test specimens were manufactured in two different materials; Polyamide12 and Titanium (Ti6Al4V). In order toinvestigate the limitations and controllability of the process, the dimensions of the internal cavities were determinedby a correlation of tactile measurements on external features and CT-data. The results were also compared to computeraided design (CAD) data. This work provides some insight concerning part accuracy of today’s frontier of AM systemsand the ability to measure and characterize internal features using CT.

  • 17.
    Johansson, Anders
    et al.
    Global Industrial Development, Scania CV AB, Södertälje, Sweden; Department of Engineering Science, University West, Trollhättan, Sweden.
    Christiernin, Linn Gustavsson
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Manufacturing system design for business value, a holistic design approach2016In: 26th CIRP Design Conference, Amsterdam: Elsevier, 2016, p. 659-664Conference paper (Refereed)
    Abstract [en]

    When designing and developing manufacturing systems, many aspects need to be considered. Typically, the manufacturing design objectives are specified to achieve certain operational requirements around quality, capacity, cost etc. They are also specified with the intention to ensure efficient processes related to manufacturing, such as maintenance, logistics, not to mention the main process of manufacturing the actual part. This study proposes that a wider company perspective should be considered during manufacturing system design, to achieve a greater business value. The manufacturing system should be designed to create value to other core business processes, such as product development, marketing, sales and services. This paper also presents examples on value perspectives to consider and how this approach can be implemented.

  • 18.
    Johansson, Anders
    et al.
    Global Industrial Development, Scania CV AB, Södertälje, Sweden; Department of Engineering Science, University West, Trollhättan, Sweden.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Christiernin, Linn Gustavsson
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Consideration of market demand volatility risks, when making manufacturing system investments2016In: 13th Global Conference on Sustainable Manufacturing - Decoupling Growth from Resource Use, Elsevier, 2016, Vol. 40, p. 307-311Conference paper (Refereed)
    Abstract [en]

    When investing in new manufacturing systems, many aspects must be taken into consideration to ensure a sustainable business. In respect to the financial aspect, both the one-off investment cost and the continuous operational cost must be analysed to ensure that the life-cycle cost perspective is appreciated. However, one detail in the cost analyses that is often overlooked is the composition of fixed and variable cost elements. These details are important to be able to better manage the risk of market demand volatility, and accordingly make appropriate investment decisions. This case study demonstrates that when there is a low risk for reduced market demand, investing in a manufacturing system with low variable cost is favourable. However, if there is a high risk for reduced market demand, the importance will instead be to have a low fixed cost, as this will be the dominant cost factor. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of International Scientific Committee of the 13th Global Conference on Sustainable Manufacturing

  • 19.
    Johansson, Anders
    et al.
    Global Industrial Development, Scania CV AB, Södertälje, Sweden; Department of Engineering Science, University West, Trollhättan, Sweden.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Christiernin, Linn Gustavsson
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Production support model to manage market demand volatility risks2016In: Factories of the Future in the digital environment: Proceedings of the 49th CIRP Conference on Manufacturing Systems / [ed] Westkamper, E; Bauernhansl, T, Elsevier, 2016, p. 664-668Conference paper (Refereed)
    Abstract [en]

    In the investment selection process during the design of new manufacturing systems, both the technical attributes and the expected financial performance need to be evaluated. To manage the financial risks with market volatility, it is important to understand the composition of fixed and variable cost factors in relation to the expected volume interval. The support model developed in this paper will in a simple and intuitive way visualise the effect on production cost due to changes in market demands. It can also be used to evaluate the volume sensitivity of existing manufacturing systems, even compare systems making different products. (C) 2016 The Authors. Published by Elsevier B.V.

  • 20.
    Karlsson, Patrik
    et al.
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Oikonomou, Christos
    Uddeholms AB, Hagfors, Sweden.
    Factors Influencing Mechanical Properties of Additive Manufactured Thin-Walled Parts2017In: Euro PM2017 Congress Proceedings, European Powder Metallurgy Association (EPMA) , 2017Conference paper (Refereed)
    Abstract [en]

    By using the Additive Manufacturing (AM) method it is possible to manufacture components with thin-walled sections and complex geometry. However, it is not clear when the surface becomes the strength limiting factor on thin-walled sections in the components or if the thickness of the components is reduced. Also, the microstructure of AM produced specimens may be heterogeneous and it is not clear how the build direction influence the strength of thin section components. In the present study, the influence of component thickness, surface roughness and build direction on the strength of AM produced components were investigated. Test specimens were manufactured using EOS M290 3D-printer and EN 1.2709 maraging steel powder. To investigate when the part thickness, surface and built orientation becomes the strength limiting factors tensile testing using thin samples built in both  horizontal and vertical build orientation with thicknesses ranging from 0.2 mm to 4 mm was performed. Results on strength limiting factors are discussed.

  • 21.
    Larsson, Joakim
    et al.
    Örebro University, School of Science and Technology.
    Jansson, Anton
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Process monitoring of the wire drawing process using a web camera based vision system2017In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 249, p. 512-521Article in journal (Refereed)
    Abstract [en]

    Wire drawing is a cold metal forming process where a wire is drawn through a series of dies, reducing the wire dimension, and enhancing the material properties. The wire drawing process requires lubrication to function, as discrepancies in the lubrication can cause failure of the entire process. Such incidents can be costly and there is a need to monitor the process so that changes in the lubrication can be detected, and addressed, before failures occur. The aim of this work was to determine whether a CCD-camera could be used to monitor the wire drawing process. The purpose of the monitoring was to detect if the process was about to fail. In this work the failure of the process was initiated by removal of the lubricant, causing galling between the wire and the die. The signal from the CCD-camera was compared to the signal from a drawing force measurement that clearly indicates when the friction in the die increases, which in turn indicates imminent failure of the process. It was found that the CCD-camera signal clearly indicated the removal of lubricant, and thus failure. In this work, the CCD-camera was tested on two different wire materials and two different lubricant, both with positive results. All tests were performed in an industrial wire drawing setup.

  • 22.
    Larsson, Joakim
    et al.
    Örebro University, School of Science and Technology.
    Jansson, Anton
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Wire 4.02019Conference paper (Other academic)
    Abstract [en]

    Today many manufacturing plants are getting increasingly digitized to stay competitive. Data from the production machines can be transferred to a central storage/cloud for process/factory surveillance and for optimizing the processes. However, first data must be acquired. Wire drawing machines are seldom equipped with sensors that measure product quality, tool wear or the condition of the lubrication. This work presents concepts, experience and applications, of such sensors for wire drawing machines.

  • 23.
    Larsson, Joakim
    et al.
    Örebro University, School of Science and Technology.
    Karlsson, Patrik
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    The effect of bearing length on the surface quality of drawn wire2019Conference paper (Refereed)
    Abstract [en]

    In wire drawing, the geometry of drawing dies influences the performance of the wire process. This study investigates the effect of bearing lengths on the surface quality of the drawn wire. Wire drawing tests were done using an industrial wiredrawing machine utilizing drawing dies with different bearing lengths. The influence of bearing length on surface quality is discussed.

  • 24.
    Larsson, Joakim
    et al.
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Preliminära resultat från jämförelse mellan konventionell dragning och dragning med Roller Dies2015Conference paper (Other academic)
    Abstract [en]

    The use of roller dies instead of conventional dies has been discussed for a long time. Already in the 1960s there where lectures at “Nordisk trådteknisk förenings” annual meetings about the use of roller dies. But still today the method haven’t had its breakthrough. This paper is based on a research project conducted by Örebro University in association with some of the leading wire drawing companies in Sweden and the Swedish steel producers association. Experiments have been carried out to compare process parameters and wire properties of wire that has been produced with conventional dies and with roller dies. Three different types of steel wire has been included in the study, low carbon, high carbon and stainless.

  • 25.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Evaluation of internal defects in additive manufactured metallic network structures by Computed Tomography2018Conference paper (Refereed)
    Abstract [en]

    The ability to manufacture complex internal features is one of the distinct differentiators of Additive Manufacturing (AM) as compared to other manufacturing methods for metal components. This manufacturing process provide designers with new opportunities in the design, such as e.g. networks and curved and non round cooling channels. To fully take advantage of metal AM in industrial use, robust methods for the detection of potential internal defects is however needed. A method that holds the promise of being one of the few tools for non-destructive evaluation (NDE) of internal features and defects is X-ray computed tomography (CT). The applicability and limitations of CT, especially for defect determination in products with complex internal structures is however not fully understood. In this work, parts with different sizes of controlled internal defects in the form of slots of varying width, 0,1 – 0,4 mm was manufactured by AM, using Selective Laser melting (SLM). The parts were produced in both titanium and aluminium alloys and both with internal networks and as solid pieces. For both of the designed types of samples, containing the pre designed defects, the ability to detect the defects by industrial computed tomography (CT) was evaluated. The evaluation of defects using CT data can be done by a trained operator. For solid components this can be done with some assistance of analysis modes that are available in comersial software. For components with complex internal structures, the result is more operator dependant and more work is needed to develop methods for CT inspection that can enable automation of the inspection process and/or to assist a trained operator.

  • 26.
    Pejryd, Lars
    et al.
    Örebro University, School of Science and Technology.
    Beno, Tomas
    University West, Trollhättan, Sweden.
    Carmignato, Simone
    University of Padova, Padova, Italy.
    Computed tomography as a tool for examining surface integrity in drilled holes in CFRP composites2014In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 13, p. 43-48Article in journal (Refereed)
    Abstract [en]

    In light weight structures the joining of composite materials and of composites to metals are key technologies. A manufacturing method associated with joining is the drilling of holes. The hole creation in CRFP through drilling is associated with several defects related to the process, both on the entry and exit sides of the hole and also with dimensional and surface roughness issues of the hole wall. The detection of damage due to the process is not trivial. Especially interesting is non-destructive methods.

    In this work X-ray computed tomography is used to determine defects due to drilling of holes in a CFRP composite using twist drills with different geometrical features at different drilling parameters. The results can be used to establish relationship between different geometrical features of drills in combination with cutting parameters and resulting surface integrity of holes.

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  • 27.
    Pejryd, Lars
    et al.
    Örebro University, School of Science and Technology.
    Hällgren, Sebastian
    Örebro University, School of Science and Technology. Saab Dynamics AB, Karlskoga, Sweden.
    Product- and knowledge centric Additive Manufacturing research in Sweden2016In: 7th Swedish Production Symposium 2016, 2016Conference paper (Refereed)
    Abstract [en]

    Additive Manufacturing (AM) is a new manufacturing method capable of creating complex shapes that previously was not possible or required long lead time tooling. Different AM methods exist, each with their own strength and weaknesses. Research of AM is done by both industry and academia to better understand the AM methods capabilities. This paper categorises AM research methods in product-centric and knowledge-centric research. Through a literature survey, Sweden’s contributions in AM research are highlighted and categorised. Interviews of designers and manufacturers of metal AM parts are done to find the research challenges of AM for Swedish industries today. Parts manufactured during 2015 using Powder Bed Fusion (PBF) AM processes are shown with examples of AM advantages used. Results show that Sweden contributes well to AM research in mainly knowledge-centric research of material properties and microstructure. A large portion of published papers are done by or in cooperation with Swedish industry. AM is industrially used today mainly for prototypes during development but some Swedish industries are designing specifically for AM. By improving part performance, these parts may reach series production. The biggest challenge is the immature process control of the AM processes, causing uncertain part properties.

  • 28.
    Pejryd, Lars
    et al.
    Örebro University, School of Science and Technology.
    Karlsson, Patrik
    Örebro University, School of Science and Technology.
    Hällgren, Sebastian
    Örebro University, School of Science and Technology.
    Kahlin, Magnus
    Linköping University, Linköping, Sweden.
    Non-destructive evaluation of internal defects in additive manufactured aluminium2016Conference paper (Refereed)
  • 29.
    Pejryd, Lars
    et al.
    Örebro University, School of Science and Technology.
    Larsson, Joakim
    Örebro University, School of Science and Technology.
    Additively manufactured tool holder for wire drawing processes2018In: Euro PM 2018 Congress and Exhibition, EPMA , 2018, article id 3987660Conference paper (Refereed)
    Abstract [en]

    Manufacturing of wires, where metal rods and/or wire are drawn through a series of dies to produce the final dimensions, generates heat in the tool. The cemented carbide tool is enclosed in a tool holder of steel that also serves as a cooling body. Earlier work have shown that reducing the temperature of the tool through the tool holder may lead to increased life time for the tool. In this work, the additive manufacturing technique (AM) selective laser melting was used to produce a steel tool holder with conformal cooling channels, without having to take into account the restrictions of machining processes for the placement of these channels. The cooling capacity of the tool holder, was studied by experiments measuring temperature of the tool holder and of the cooling liquid as well as flow. A heating-probe having the shape of the tool, mimicking the thermal conditions of a wire drawing process, was used. The increased cooling was also compared to FEM modelling results.

  • 30.
    Pejryd, Lars
    et al.
    Örebro University, School of Science and Technology.
    Larsson, Joakim
    Örebro University, School of Science and Technology.
    Olsson, Mikael
    Dalarna University, Falun, Sweden.
    Process monitoring of wire drawing using vibration sensoring2017In: CIRP - Journal of Manufacturing Science and Technology, ISSN 1755-5817, E-ISSN 1878-0016, Vol. 18, p. 65-74Article in journal (Refereed)
    Abstract [en]

    Automating the detection of processing conditions that may lead to defects in the wire during the wire drawing process is of high interest to the industry. Current practise is based primarily on operator experience. Increasing demands on product quality and process robustness emphasises the need for development of robust in-process detection methods. This work is focusing on investigating the potential of using vibration monitoring to detect process deficiencies or variations that may lead to defects in the product. Wire drawing of a carbon steel in different lubricating situations was used to investigate vibration signal response together with force measurements and surface investigation of the wire product. The results show that vibration measurement is capable of detecting loss of lubrication that leads to poor surface quality of the wire.

  • 31.
    Sadeghimeresht, Esmaeil
    et al.
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Karimi, Paria
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Zhang, Pimin
    Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Peng, Ru
    Department of Management and Engineering, Linköping University, Linköping, Sweden.
    Andersson, Joel
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Joshi, Shrikant
    Department of Engineering Science, University West, Trollhättan, Sweden.
    Isothermal Oxidation Behavior of EBM-Additive Manufactured Alloy 7182018In: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications / [ed] Ott, E.; Liu, X.; Andersson, J.; Bi, Z.; Bockenstedt, K.; Dempster, I.; Groh, J.; Heck, K.; Jablonski, P.; Kaplan, M:, Nagahama, D.; Sudbrack, C, Springer, 2018, p. 219-240Conference paper (Refereed)
    Abstract [en]

    Oxidation of Alloy 718 manufactured by electron beam melting (EBM) process has been undertaken in ambient air at 650, 700, and 800 degrees C for up to 168 h. At 800 degrees C, a continuous external chromia oxide enriched in (Cr, Ti, Mn, Ni) and an internal oxide that was branched structure of alumina formed, whereas at 650 and 700 degrees C, a continuous, thin and protective chromia layer was detected. The oxidation kinetics of the exposed EBM Alloy 718 followed the parabolic rate law with an effective activation energy of similar to 248 +/- 22 kJ/mol in good agreement with values in the literature for conventionally processed chromia-forming Ni-based superalloys. The oxide scale formed on the surface perpendicular to the build direction was slightly thicker, and more adherent compared to the scale formed on the surface along the build direction, attributed to the varied grain texture in the two directions of the EBM-manufactured specimens. The increased oxygen diffusion and high Cr depletion found on the surface along the build direction were attributed to the fine grains and formation of vacancies/voids along this grain orientation.

  • 32.
    Surreddi, K. B.
    et al.
    Materials Science, Dalarna University, Falun, Sweden.
    Oikonomou, C.
    Uddeholms AB, Hagfors, Sweden.
    Karlsson, Patrik
    Örebro University, School of Science and Technology.
    Olsson, M.
    Materials Science, Dalarna University, Falun, Sweden.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    In-situ micro-tensile testing of additive manufactured maraging steels in the SEM: Influence of build orientation, thickness and roughness on the resulting mechanical properties2018In: La Metallurgia Italiana, ISSN 0026-0843, no 3, p. 27-33Article in journal (Refereed)
    Abstract [en]

    Selective laser melting (SLM) is frequently used additive manufacturing technique capable of producing various complex parts including thin-wall sections. However the surface roughness is a limiting factor in thin sections produced by SLM process when strength is the main criterion. In this study, the influence of build orientation, thickness and roughness on the resulting mechanical properties of as-built test samples was investigated. Various thin sheets of EN 1.2709 maraging steel built in horizontal and vertical orientations produced by SLM were investigated using in-situ micro-tensile testing in a scanning electron microscope. The mechanical strength and deformation mechanisms were analyzed and explained based on thickness and build orientation. Increased ductility was observed in thicker samples as well as in the horizontal build samples. The results illustrate the potential of the in-situ test technique and aspects important to consider in design guidelines for thin AM structures.

  • 33.
    Zekavat, Amir Reza
    et al.
    Örebro University, School of Science and Technology.
    Adibi, Pooya Tahib Zadeh
    RISE, Borås, Sweden.
    Johannesson, Pär
    RISE, Borås, Sweden.
    Karlsson, Patrik
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Sjögren, Torsten
    RISE, Borås, Sweden.
    An experimental approach to investigatethe influential parameters on mechanical strength of AlSi10Mgthin-wall structures manufactured by selective laser meltingManuscript (preprint) (Other academic)
  • 34.
    Zekavat, Amir Reza
    et al.
    Örebro University, School of Science and Technology.
    Jansson, Anton
    Örebro University, School of Science and Technology.
    Gundlach, Carsten
    Technical University of Denmark, Kongens Lyngby, Denmark.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Effect of X-ray Computed Tomography Magnification on Surface Morphology Investigation of Additive Manufacturing Surfaces2018In: 8th Conference on Industrial Computed Tomography, 2018Conference paper (Refereed)
    Abstract [en]

    Additive manufacturing (AM) in the last decade has become a widespread manufacturing process. The possibilities that such technologies have provided for manufacturing of complex geometries compared to conventional manufacturing processes has made them popular in many branches of industry. Despite the advantages of these methods, there are limiting issues which needs to be thoroughly investigated. A limiting factor, especially for powder bed AM parts is their undesired surface finish. AM surfaces can be investigated using various methods such as optical or tactile methods, however for complex AM surfaces they are incapable of capturing all details such as deep valleys at surface level. X-ray computed tomography (CT), can provide 3D information of complex AM surfaces and does not have limitations that line of sight and tactile methods have. There are several parameters in CT investigation, which can potentially alter the obtained results. Depending on the CT magnification at which the data is acquired the result specifically surface level detail might be affected. The aim of this study is to investigate the effect of different CT magnifications on surface texture measurement of additively manufactured surfaces. Surface features, including highest peaks and deepest valleys contributing to maximum and minimum thickness of specimen from different magnifications were compared with each other. The result shows that, the lower magnification scans underestimate both peak and valley measurements in comparison to the highest magnification scan. Measurement of valleys and re-entrant features were underestimated at more considerable level. The results from this study provide some understanding regarding surface morphology assessment of AM parts and the level of detail which can be expected depending on the CT magnification.

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    Effect of X-ray Computed Tomography Magnifi cation on Surface Morphology Investigation of Additive Manufacturing Surfaces
  • 35.
    Zekavat, Amir Reza
    et al.
    Örebro University, School of Science and Technology.
    Jansson, Anton
    Örebro University, School of Science and Technology.
    Larsson, Joakim
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Investigating the effect of fabrication temperature on mechanical properties of fused deposition modelling parts using X-ray computed tomography2019In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 100, no 1-4, p. 287-296Article in journal (Refereed)
    Abstract [en]

    Fused deposition modeling (FDM) is one of the most common additive manufacturing (AM) techniques for fabricating prototypes as well as functional parts. In this technique, several parameters may influence the part quality and consequently mechanical properties of fabricated components. In this paper, an experimental investigation on effects of fabrication temperature as one of the influential parameters on mechanical properties of manufactured parts is presented. A series of specimens fabricated at temperatures ranging from 180 to 260 C were used for this investigation. X-ray computed tomography (CT) was used in order to non-destructively analyze the internal geometry of the specimens especially the bond between extruded filaments. Finally, the specimens were subjected to a uniaxial tensile load for evaluation of mechanical properties. The results showed that the specimens fabricated at lower temperatures have relatively lower tensile strength despite their considerably higher strain at break. In addition, the specimens fabricated at higher temperature range had significantly higher tensile strength because of the better bond between extruded filaments. The different mechanical responses were highly related to the internal geometry of the specimens and not necessarily the porosity. CT showed great potential as a non-destructive tool for investigation and development of FDM process.

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    Investigating the effect of fabrication temperature on mechanical properties of fused deposition modeling parts using X-ray computed tomography
  • 36.
    Zekavat, Amir Reza
    et al.
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Surface characterization of additively manufactured Al10SiMg thin-walled structures2016In: 7th Swedish Production Symposium, 2016Conference paper (Refereed)
    Abstract [en]

    Additive manufacturing (AM) is a newly developed technique for fabrication of parts with complexgeometries. Despite the fact that this technique has made it possible to fabricate near net shape and complexgeometries, there can be a mismatch between as-designed and as-fabricated geometries. These geometricalimperfections can hinder the structural response of fabricated structures by not fulfilling the strength theyare designed for. These mismatches, specifically surface morphology become even more important factorin case of manufacturing of thin-walled structures by AM. This is due to the fact that the surface regionwhich is mainly consist of partially melted powders does not necessarily contribute in strength. Thus, theeffect of surface morphology on mechanical properties in such structure should be investigated and takeninto account in the design stage. In this study high resolution X-ray computed tomography (micro-CT) hasbeen used for qualitative investigation of surface morphology of specimens made of AlSi10Mg. Flatspecimens with different thicknesses has been fabricated by selective laser melting (SLM). Using micro-CT it was possible to non-destructively measure the surface region in thin-walled builds. The measurementfrom micro-CT as well as result from optical profilometry showed the usefulness of micro-CT for thoroughinvestigation of AM parts. The study showed that micro-CT is a robust method for qualitative measurementof surface morphology of parts made of AlSi10Mg using SLM technique. It also gave an insight on wherethe geometrical mismatch specifically at micro scale become an important factor in design of such structuresfabricated using SLM technique. The result from this study lead to development in design stage of AMprocesses.

  • 37.
    Zekavat, Amir Reza
    et al.
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Ekengren, Jens
    Örebro University, School of Science and Technology.
    Tracking the shape deformation of voids from tensile loading by the use of computed tomography2015In: Digital Industrial Radiology and Computed Tomography (DIR 2015), 2015, article id 18034Conference paper (Refereed)
    Abstract [en]

    The understanding of interaction between voids such as pores or holes in additive manufactured open structures is of importance in understanding the strength of components. Behavior in three dimensions is of particular interest. X-ray tomography is one of the few techniques that has the possibility to nondestructively aid in analyzing issues such as shape deformation. In this work, X-ray computed tomography was applied as a nondestructive tool for tracking the shape deformation of voids.

    A simplified model representing three dimensional voids is used to investigate the effect of influential parameters like void size, their distance from each other and orientation of voids in respect to the uniaxial tensile load. A set of ex-situ X-ray micro tomography tensile test is performed on flat aluminum (6082-T6) tensile bars with drilled through holes representing different configuration of voids. Digital image correlation was used to measure the strain localization in the adjacent area of the holes. Corresponding Finite Element (FE) analysis is performed to predict the shape deformation and by this validate the model. This modelling may give a better insight of pores interaction under more complex loading scenarios and leads to better controllability of internal structure design of additive manufactured (AM) parts.

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    Tracking the shape deformation of voids from tensile loading by the use of computed tomography
  • 38.
    Zekavat, Amir Reza
    et al.
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Gundlach, Carsten
    Technical University of Denmark, Copenhagen, Denmark.
    Effect of X-Ray Computed Tomography Magnification on Porosity Analysis of Additively Manufactured Parts2018In: World PM2018 Congress Proceedings, 2018Conference paper (Refereed)
    Abstract [en]

    X-ray computed tomography has been widely used for inspection of parts manufactured using additive manufacturing (AM) and powder metallurgy (PM). The ability of this method to non-destructively evaluate the porosity content of parts fabricated using AM and PM has made it a reliable method for such inspection. The results obtained from this method are highly dependent on CT acquisition parameters such as the magnification (resolution) at which the part has been scanned. Depending on the size of the parts the scan might need to be performed at lower magnifications which results in loss of information for porosity analysis. Therefore the effect of changing CT magnification on the obtained porosity of an additively manufactured specimen made of AlSi10Mg is investigated in this study. The specimen was scanned at various magnifications resulting in data sets with different resolutions. The porosity content was measured for each data set and the results showed that the porosity measurement using CT is highly dependent on the magnification (resolution) at which the data sets are acquired. The results from this study provided essential information about the porosity content which should be expected depending on the CT magnification.

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