32 results on '"Pedersen, David"'
Search Results
2. 3D-printing a cost-effective model for mastoidectomy training
- Author
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Frithioff, Andreas, Weiss, Kenneth, Frendø, Martin, Senn, Pascal, Mikkelsen, Peter Trier, Sieber, Daniel, Sørensen, Mads Sølvsten, Pedersen, David Bue, and Andersen, Steven Arild Wuyts
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- 2023
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- View/download PDF
3. The effect of layer height and post-curing temperature on the shape memory properties of smart polymers in vat photopolymerization
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Danielak, Anna, Chauhan, Siddharth Singh, Islam, Aminul, Andrzejewski, Jacek, and Pedersen, David Bue
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- 2023
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4. Applying systems engineering principles to develop an open source laser based metal powder bed fusion system.
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Kjer, Magnus Bolt, Nadimpalli, Venkata Karthik, Budden, Christian Leslie, and Pedersen, David Bue
- Abstract
Purpose: Conventional powder bed fusion systems, with their high costs, proprietary nature and restrictive fees, limit research opportunities. This study aims to unveil an affordable, open-source hardware, open-source software laser-based metal powder bed fusion system. Recognizing the distinction between DIY and open-source hardware is crucial for widespread acceptance. Design/methodology/approach: The authors present a comprehensive system architecture using object process methodology for functions and architecture, a design structure matrix to model system dependencies and classical technical drawing exploded views for select subsystems. Modularization enables high adaptability, fostering potential adoption. Findings: The fully open system enables unrestricted research, mirroring common industrial metal laser-based powder bed fusion (L-PBF) systems. While "open" systems are available for purchase, they remain closed-source, lacking source code and technical drawings sharing, hindering contribution and co-development. The authors' is the pioneering and sole open-source metal L-PBF system, boasting 1,500+ print hours. A series of industrial and academic adopters are currently implementing the system. Originality/value: The open system, slicer software and controller offer unique process control, supporting multimaterial printing. The authors shared the design on the OpenAM GitHub page under the CERN-OHL-P v2 Open Source Hardware license. While it is functional for additive manufacturing (e.g. aluminum, tool steel, titanium and stainless steel), the entire process chain is actively evolving, ideal for co-development with the additive manufacturing community. [ABSTRACT FROM AUTHOR]
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- 2024
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- View/download PDF
5. Measurements in Additive Manufacturing
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Pedersen, David Bue, Andersen, Sebastian Aagaard, Hansen, Hans Nørgaard, Zhang, Liangchi, Section Editor, and Gao, Wei, editor
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- 2019
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6. Integration of Fiber-Reinforced Polymers in a Life Cycle Assessment of Injection Molding Process Chains with Additive Manufacturing
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Hofstätter, Thomas, Bey, Niki, Mischkot, Michael, Stotz, Philippe M., Pedersen, David B., Tosello, Guido, Hansen, Hans N., Meboldt, Mirko, editor, and Klahn, Christoph, editor
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- 2018
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7. Performance Simulation and Verification of Vat Photopolymerization Based, Additively Manufactured Injection Molding Inserts with Micro-Features
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Mischkot, Michael, Hofstätter, Thomas, Michailidou, Ifigeneia, Chavarri, Carlos Herrán, Lunzer, Andreas, Tosello, Guido, Pedersen, David Bue, Hansen, Hans Nørgaard, Meboldt, Mirko, editor, and Klahn, Christoph, editor
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- 2018
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- View/download PDF
8. Augmented Reality Interfaces for Additive Manufacturing
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Eiriksson, Eythor R., Pedersen, David B., Frisvad, Jeppe R., Skovmand, Linda, Heun, Valentin, Maes, Pattie, Aanæs, Henrik, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Sharma, Puneet, editor, and Bianchi, Filippo Maria, editor
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- 2017
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9. Value chain and production cost optimization by integrating additive manufacturing in injection molding process chain
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Tosello, Guido, Charalambis, Alessandro, Kerbache, Laoucine, Mischkot, Michael, Pedersen, David Bue, Calaon, Matteo, and Hansen, Hans Nørgaard
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- 2019
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10. Surface Roughness and Grain Size Variation When 3D Printing Polyamide 11 Parts Using Selective Laser Sintering.
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Tonello, Riccardo, Conradsen, Knut, Pedersen, David Bue, and Frisvad, Jeppe Revall
- Subjects
SELECTIVE laser sintering ,SURFACE roughness ,THREE-dimensional printing ,POLYAMIDES ,MELTING points ,LASER beams ,GRAIN size - Abstract
Selective laser sintering (SLS) is a well-established technology that is used for additive manufacturing. Significant efforts have been made to improve SLS by optimizing the powder deposition, laser beam parameters, and temperature settings. The purpose is to ensure homogeneous sintering and prevent geometric and appearance inaccuracies in the manufactured objects. We evaluated the differences in the surface roughness and grain size of curved objects manufactured by using upcoming SLS technology that features two CO laser sources. Our analysis was carried out on polyamide 11 (PA11), which is a sustainable biobased polymer that has been gaining popularity due to its high-performance properties: its low melting point, high viscosity, and excellent mechanical properties. By using a Taguchi experimental design and analysis of variance (ANOVA), we examined the influence on the surface roughness and grain size of the build setup, the presence of thin walls, and the position of the sample on the powder bed. We found significant differences in some surface roughness and grain size measurements when these parameters were changed. [ABSTRACT FROM AUTHOR]
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- 2023
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11. Performance evaluation of in-situ near-infrared melt pool monitoring during laser powder bed fusion.
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Moshiri, Mandaná, Pedersen, David Bue, Tosello, Guido, and Nadimpalli, Venkata Karthik
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POWDERS , *LASERS , *THREE-dimensional imaging , *PHOTODIODES , *QUALITY assurance , *NEAR infrared radiation - Abstract
In-situ co-axial meltpool monitoring has become a popular tool for digitising the laser powder bed fusion (L-PBF) process, providing baseline data for certification. Each layer produces an image where the pixel position represents the laser coordinates and the pixel intensity denotes the sensor response. The 3D image stacks represent the infrared emission during the manufacturing of the physical component. However, interpreting monitoring data remains a challenge. To address this issue, this study evaluates the performance of a near-infrared photodiode in detecting typical geometrical features such as porosity and overhanging structures ranging from the micro-to-meso scale. Monitoring data is highly sensitive to heat accumulation around overhanging structures and can quantify dross formation based on hotspots. Cold spots, which represent a lack of fusion porosity at scan track intersections, can indicate a probability of defect formation. However, the sensitivity and predictive value of monitoring data for porosity are low due to the healing of defects in subsequent layers. Local process variables, such as the scan strategy and part orientation, significantly influence dross and hot spot formation. This study shows the potential of NIR photodiodes in deriving metrics for in-line certification of L-PBF components, leading to improved process control and quality assurance. [ABSTRACT FROM AUTHOR]
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- 2023
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12. In-process 3D geometry reconstruction of objects produced by direct light projection
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Andersen, Ulrik Vølcker, Pedersen, David Bue, Hansen, Hans Nørgaard, and Nielsen, Jakob Skov
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- 2013
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13. Precision Injection Moulding with Inserts made of Mortar Material
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Krüger, Kilian, Regi, Francesco, Calaon, Matteo, Pedersen, David B., and Tosello, Guido
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Mortar ,Injection moulding ,Additive manufacturing ,Tooling - Abstract
Over the last years, Additive Manufacturing (AM) technologies have developped rapidly, making it now possible to manufacture duromer-based soft moulds for polymer precision injection moulding. The tool inserts fabrication process is fast and cost-effectivewhich reduces time-to-market as well as mould fix costs for the polymer component to be produced. Yet, a major drawback is the inserts’ limited lifetime (100 to a few 1 000 injection moulded parts) which cannot compete with the lifetime of high-end steel moulds. We present a new AM concept based on mortar material for rapid fabrication of inserts used in precision injection moulding of micro-structured polymer parts. The tooling process chains starts with the 3D CAD design of the master form containing the desired micro features. This master form is then fabricated by either Fused Deposition Modeling (FDM), Stereolithography Aparatus (SLA) or by Soft Lithography (SL). The master form is filled with a freshly-mixed cementious paste that hardens within some days, generating a mortar copy of the master form. Even a very smooth, almost mirror-like surface finish can be achieved, depending on the composition of the mortar paste and the surface characteristics of the master form. This AM-made mortar insert is supposed to have a long lifetime making it suitable for low to medium scale production and was validated in the present study. Furthermore, we employed the Autodesk Moldflow injection moulding simulation software in order to determine the optimum thermal conductivity of the mortar insert. The thermal conductivity of the mould material needs to be tailored individually in order to balance polymer melt quenching (poor micro replication fidelity) and extended cooling time (low productivity and high variable costs). The mixture of the mortar material can be adjusted accordingly. The presented process chain exploits the advantages of AM / rapid tooling yet avoids the disadvantages of soft moulds. Therefore, it has the potential to become a game changer in polymer precision manufacturing.
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- 2019
14. 3D-Printed Models for Temporal Bone Surgical Training: A Systematic Review.
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Frithioff, Andreas, Frendø, Martin, Pedersen, David Bue, Sørensen, Mads Sølvsten, and Wuyts Andersen, Steven Arild
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Objective: 3D-printed models hold great potential for temporal bone surgical training as a supplement to cadaveric dissection. Nevertheless, critical knowledge on manufacturing remains scattered, and little is known about whether use of these models improves surgical performance. This systematic review aims to explore (1) methods used for manufacturing and (2) how educational evidence supports using 3D-printed temporal bone models. Data Sources: PubMed, Embase, the Cochrane Library, and Web of Science. Review Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, relevant studies were identified and data on manufacturing and validation and/or training extracted by 2 reviewers. Quality assessment was performed using the Medical Education Research Study Quality Instrument tool; educational outcomes were determined according to Kirkpatrick's model. Results: The search yielded 595 studies; 36 studies were found eligible and included for analysis. The described 3D-printed models were based on computed tomography scans from patients or cadavers. Processing included manual segmentation of key structures such as the facial nerve; postprocessing, for example, consisted of removal of print material inside the model. Overall, educational quality was low, and most studies evaluated their models using only expert and/or trainee opinion (ie, Kirkpatrick level 1). Most studies reported positive attitudes toward the models and their potential for training. Conclusion: Manufacturing and use of 3D-printed temporal bones for surgical training are widely reported in the literature. However, evidence to support their use and knowledge about both manufacturing and the effects on subsequent surgical performance are currently lacking. Therefore, stronger educational evidence and manufacturing knowhow are needed for widespread implementation of 3D-printed temporal bones in surgical curricula. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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15. Additive manufacturing with vat polymerization method for precision polymer micro components production
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Davoudinejad, Ali, Péreza, Lucia C. Díaz, Quagliotti, Danilo, Pedersen, David Bue, Garcíaa, José A. Albajez, Yagüe-Fabra, José A., and Tosello, Guido
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Micro precision manufacturing ,Additive manufacturing ,Polymer components - Abstract
The direct fabrication of miniaturized polymer components by Additive Manufacturing (AM) processes is a remarkable method at the microdimensional scale. However, the measurement of complex micro products and the evaluation of the related uncertainty are still particularly challenging and necessary in the micro AM field. In the DTU, a proprietary Vat Photopolymerization machine able to produce micro features has been designed, built and validated. This study evaluates the capability of the machine in terms of printed dimensions and the corresponding uncertainty assessment. For this purpose, two test parts with micro features of different geometries and dimensions have been designed and five samples of each test part have been printed. The dimensions of the micro features have been evaluated for quality control capability assessment and to stablish procedures for verification of AM machines
- Published
- 2018
16. Geometrical shape assessment of additively manufactured features by direct light processing vat polymerization method
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Péreza, Lucia C. Díaz, Ali Davoudinejad, Quagliotti, Danilo, Pedersen, David Bue, Garcíaa, José A. Albajez, Yagüe-Fabraa, José A., Tosello, Guido, Billington, D., Leach, R. K., Phillips, D., Riemer, O., and Savio, E.
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Additive manufacturing ,Micro Manufacturing ,Vat Polymerization ,Polymer - Abstract
The importance of Additive Manufacturing (AM) in the field of micro manufacturing is increasing. Vat Polymerization Methods are one of the lead AM technologies to produce polymer micro parts. In the Technical University of Denmark (DTU), a vat photopolymerization AM machine able to print features in a micro scale was developed, build and validated. The work here presented analyses the capability of the machine in terms of geometry, when printing features of different sizes and geometries. For this study, two test parts have been designed, a circular stepped pyramid and a square stepped pyramid, both having micro size steps at the top of the pyramids. Five batches of each test part have been printed to evaluate the variability of the results in a single and in various prints.
- Published
- 2018
17. Performance Simulation and Verification of Vat Photopolymerization Based, Additively Manufactured Injection Molding Inserts with Micro-Features
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Mischkot, Michael, Hofstätter, Thomas, Michailidou, Ifigeneia, Herrán Chavarri, Carlos, Lunzer, Andreas, Tosello, Guido, Pedersen, David Bue, Hansen, Hans Nørgaard, Meboldt, M., and Klahn , C.
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Additive manufacturing ,Soft tooling ,Micro injection molding ,Simulation - Abstract
Injection molding soft tooling inserts manufactured additively with vat photopolymerization represent a valid technology for prototyping and pilot production of polymer parts. However, a significant drawback is the low heat conductivity of photopolymers influencing cycletime and part quality. In this research, the thermal performance of a 20x20x2.7 mm3 injection molding insert was simulated. A thermal camera was used to assess the quality and accuracy of the simulation. Both, simulation and measurements showed that the temperature cycle during injection molding becomes stationary within 3 to 5 cycles. After 2800 injection molding cycles, the experiment was stopped and the insert was still intact.
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- 2017
18. Dimensional accuracy of Acrylonitrile Butadiene Styrene injection molded parts produced in a pilot produc
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Mischkot, Michael, Ali Davoudinejad, Charalambis, Alessandro, Hofstätter, Thomas, Tosello, Guido, Pedersen, David Bue, and Hansen, Hans Nørgaard
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Additive manufacturing ,Soft tooling ,Micro injection molding - Abstract
Injection molding inserts manufactured additively by vat photopolymerization have become a serious option for significantly faster and more economical prototyping and pilot production due to technological progress and advancements in photopolymer materials in the recent years. 10 000 parts of a geometry including micro-features have been injection-molded in Acrylonitrile Butadiene Styrene (ABS) with a single 20x20x2.5 mm^3 injection molding insert manufactured in a photopolymer composite material. This research investigates the dimensional accuracy of the injection molded parts as a function of inserts wearing and deformation with increasing shot number.
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- 2017
19. Considerations on the Construction of a Powder Bed Fusion Platform for Additive Manufacturing
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Andersen, Sebastian Aagaard, Nielsen, Karl-Emil, Pedersen, David Bue, and Nielsen, Jakob Skov
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3D-printing ,Additive Manufacturing ,Selective Laser Melting ,Selective Laser Sintering - Abstract
As the demand for moulds and other tools becomes increasingly specific and complex, an additive manufacturing approach to production is making its way to the industry through laser based consolidation of metal powder particles by a method known as powder bed fusion. This paper concerns a variety of design choices facilitating the development of an experimental powder bed fusion machine tool, capable of manufacturing metal parts with strength matching that of conventional manufactured parts and a complexity surpassing that of subtractive processes. To understand the different mechanisms acting within such an experimental machine tool, a fully open and customizable rig is constructed. Emphasizing modularity in the rig, allows alternation of lasers, scanner systems, optical elements, powder deposition, layer height, temperature, atmosphere, and powder type. Through a custom-made software platform, control of the process is achieved, which extends into a graphical user interface, easing adjustment of process parameters and the job file generation.
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- 2017
20. Augmented Reality Interfaces for Additive Manufacturing
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Eiríksson, Eyþór Rúnar, Pedersen, David Bue, Frisvad, Jeppe Revall, Skovmand, Linda, Heun, Valentin, Maes, Pattie, and Aanæs, Henrik
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3D Printing ,Additive manufacturing ,Augmented reality - Abstract
This paper explores potential use cases for using augmented reality (AR) as a tool to operate industrial machines. As a baseline we use an additive manufacturing system, more commonly known as a 3D printer. We implement novel augmented interfaces and controls using readily available open source frameworks and low cost hardware. Our results show that the technology enables richer and more intuitive printer control and performance monitoring than currently available on the market. Therefore, there is a great deal of potential for these types of technologies in future digital factories.
- Published
- 2017
21. Integration of Fiber-Reinforced Polymers in a Life Cycle Assessment of Injection Molding Process Chains with Additive Manufacturing
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Hofstätter, Thomas, Bey, Niki, Mischkot, Michael, Stotz, Philippe Maurice, Pedersen, David Bue, Tosello, Guido, Hansen, Hans Nørgaard, Meboldt, M., and Klahn, C.
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Additive Manufacturing ,technology, industry, and agriculture ,Injection Molding ,Life Cycle Assessment ,Fiber-reinforced Polymers ,Process Chains - Abstract
Additive manufacturing technologies applied to injection molding process chain have acquired an increasingly important role in the context of tool inserts production, especially by vat polymerization. Despite the decreased lifetime during their use in the injection molding process, the inserts come with improvements in terms of production time, costs, exibility, as well as potentially improved environmental performance as compared to conventional materials in a life cycle perspective.This contribution supports the development of additively manufactured injection molding inserts with the use of fiber-reinforced vat polymerization technology. The life cycle assessment of the prototyping process chain for rapid prototyping with high exibility provides a base for industrial applications in injection molding.
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- 2017
22. Characterization of near-zero pressure powder injection moulding with sacrificial mould by using fingerprint geometries.
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Zhang, Yang, Basso, Alberto, Christensen, Simon Emil, Pedersen, David Bue, Staal, Lasse, Valler, Peter, and Hansen, Hans Nørgaard
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POWDERS ,RAPID tooling ,INJECTION molding of metals ,PRESSURE ,METAL powders - Abstract
This paper presents a process chain of powder injection moulding with sacrificial moulds. The mould is fabricated by vat polymerization based additive manufacturing, which enables production of complex metal parts. A special metal feedstock is developed, which allows near-zero injection pressure. The part is ejected together with the polymer mould. After the mould is dissolved, the released part is debinded and sintered. Micro features are printed on the mould surfaces, and the quality of the part is correlated with the replicated features in each process step. In this way the micro features are used as quality indicator, namely, a fingerprint. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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23. Evolution of Additively Manufactured Injection Molding Inserts Investigated by Thermal Simulations.
- Author
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Hofstätter, Thomas, Pedersen, David B., Tosello, Guido, and Hansen, Hans N.
- Subjects
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THREE-dimensional printing , *INJECTION molding , *SIMULATION methods & models , *FIBER-reinforced plastics , *THERMAL conductivity , *POLYMERS - Abstract
Injection molding using inserts from vat polymerization, an additive manufacturing technology, has been investigated for pilot production and rapid prototyping purposes throughout the past years. A standard mold is equipped with additively manufactured inserts in a rectangular shape of (20 x 20 x 2.7) mm³ and (60 x 80 x 10) mm³ produced with vat photo polymerization. This contribution discusses the heat transportation within the inserts made from a thermoset material, brass, steel, and ceramic material. It therefore elaborates on the possibilities of injection molding as well as the thermal challenges connected with the use of polymer inserts. They are an essential part for further calibrations of the injection molding process, which suffers from reduced lifetime due to the poor thermal conductivity of polymer inserts as compared to metal inserts. Multiscale inserts combining micro features at larger inserts in the cm-range. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
24. Internal Fiber Structure of a High-Performing, Additively Manufactured Injection Molding Insert.
- Author
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Hofstätter, Thomas, Baier, Sina, Trinderup, Camilla H., Gundlach, Carsten, Pedersen, David B., Tosello, Guido, and Hansen, Hans N.
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THREE-dimensional printing ,INJECTION molding ,COMPUTED tomography ,TENSILE tests ,LIFE cycle costing ,COST effectiveness - Abstract
A standard mold is equipped with additively manufactured inserts in a rectangular shape produced with vat photo polymerization. While the lifetime compared to conventional materials such as brass, steel, and aluminum is reduced, the prototyping and design phase can be shortened significantly by using flexible and cost-effective additive manufacturing technologies. Higher production volumes still exceed the capability of additively manufactured inserts, which are overruled by the stronger performance of less-flexible but mechanically advanced materials. In this contribution, the internal structure of a high-performing, fiber-reinforced injection molding insert has been analyzed. The insert reached a statistically proven and reproducible lifetime of 4,500 shots, which significantly outperforms any other previously published additively manufactured inserts. Computer tomography, tensile tests and life cycle analysis have been performed in order to provide an understanding of the internal structure of the fiber-reinforced, additively manufactured injection molding inserts. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
25. Flow Characteristics of a Thermoset Fiber Composite Photopolymer Resin in a Vat Polymerization Additive Manufacturing Process.
- Author
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Hofstätter, Thomas, Spangenberg, Jon, Pedersen, David B., Tosello, Guido, and Hansen, Hans N.
- Subjects
THERMOSETTING composites ,POLYMERIZATION ,FIBERS ,PHOTOPOLYMERS ,THREE-dimensional printing ,INJECTION molding - Abstract
Additive manufacturing vat polymerization has become a leading technology and gained a massive amount of attention in industrial applications such as injection molding inserts. By the use of the thermoset polymerization process inserts have increased their market share. For most industrial applications, strength and stiffness are crucial factors to a successful implementation of cured photopolymer thermosets. Hence, fiber-reinforced polymers have recently been introduced. The behavior and especially orientation of fibers during the vat photopolymerization process has yet not been fully understood. Research indicates an orientation within the manufacturing layer and efforts have been made to achieve a more uniform orientation within the part. A vat polymerization machine consisting of a resin vat and a moving build plate has been simulated using the fluid flow module of Comsol Multiphysics™. A moving mesh with hyper-elastic behavior was utilized to simulate the flow of the photopolymer during the lifting of the build plate after a successful curing of a single layer. The velocity profile can thereafter be used to estimate a prediction for the orientation of the short fibers added to the liquid photopolymer resin. The prediction can be used to identify potential clusters or misalignment of fibers and in the future allow for optimization of the machine design and manufacturing process. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
26. Toolpath Strategies for 5DOF and 6DOF Extrusion-Based Additive Manufacturing.
- Author
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Jensen, Mathias Laustsen, Mahshid, Rasoul, D'Angelo, Greta, Walther, Jeppe U., Kiewning, Malte K., Spangenberg, Jon, Hansen, Hans Nørgaard, and Pedersen, David Bue
- Subjects
SINGLE-degree-of-freedom systems ,MANUFACTURING processes ,REMANUFACTURING - Abstract
This paper introduces two new deposition-strategies for five degrees of freedom (5DOF) and 6DOF extrusion-based additive manufacturing (AM), called the tool path projection- and parent-child-approach, respectively. The tool path projection method can be automated, and allows for the generation of concentric shells layers, which remedy geometrical deviations (known as the stair-case effect) that are typically seen in 3DOF AM processes that potentially require secondary post treatment by machining or grinding of the final part. In the parent-child approach, the designer specifies the manufacturing direction for each distinct feature, thereby helping to remove the need for support material, as well as enabling new features to be dynamically added to the part. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
27. Experimental investigation and thermo-mechanical modelling for tool life evaluation of photopolymer additively manufactured mould inserts in different injection moulding conditions.
- Author
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Davoudinejad, Ali, Bayat, Mohamad, Pedersen, David Bue, Zhang, Yang, Hattel, Jesper Henri, and Tosello, Guido
- Subjects
INJECTION molding ,MANUFACTURING processes ,TOOLS ,THREE-dimensional printing ,COST effectiveness ,PLANT propagation - Abstract
There is a growing interest for integrating additive manufacturing (AM) technology in different manufacturing processes such as injection moulding (IM) due to the possibility of achieving shorter manufacturing times and increased cost effectiveness. This paper evaluates IM inserts fabricated by the AM vat photopolymerisation method. The inserts are directly manufactured with a photopolymer material, integrated on an injection moulding tool and subsequently used for IM. Therefore, particular attention has to be paid in order to develop the soft tooling process chain and the IM experimental procedure as detailed in this study. Different combinations of IM parameters are investigated in this work in order to determine the influence of the various process settings on the inserts' performance (lifetime, crack propagation, consistency of the mould surface features). The mould inserts were analysed by three-dimensional optical metrology and evaluated with regard to the different surface features that were affected by the IM process. A three-dimensional thermo-mechanical with phase change model for the analysis of the effects of the IM process on the additive manufactured tools was accomplished in the FE software COMSOL Multiphysics. The potential causes for the insert failure are identified both by means of the IM experiments and the numerical model. The developed model could also predict the thermally induced deformations produced in the mould and identify where this phenomenon would eventually lead to defects in the shape of the parts. The influence of three different temperatures of the insert at 25 °C, 50 °C and 100 °C on the failure of the insert was investigated. Also a detailed discussion about the solidification and temperature changes is given. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
28. Applications of Fiber-Reinforced Polymers in Additive Manufacturing.
- Author
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Hofstätter, Thomas, Pedersen, David B., Tosello, Guido, and Hansen, Hans N.
- Abstract
Additive manufacturing technologies are these years entering the market of functional final parts. Initial research has been performed targeting the integration of fibers into additive manufactured plastic composites. Major advantages, among others, are for example increased tensile strength and Young's modulus. Key challenges in the field, as of now, are proper fiber placement, fiber seizing, an increased knowledge in the used materials and how they are applied into engineering solutions through proper control of the additive manufacturing process. The aim of this research is the improved understanding of fiber-reinforcement in additive manufacturing in terms of production and application. Vat polymerization and material extrusion techniques for composite additive manufacturing were investigated with respect of increasing adhesion between the matrix material and the fibers. Process optimization was performed in order to avoid matrix cracks and delamination. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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29. A self-calibrating robot based upon a virtual machine model of parallel kinematics.
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Pedersen, David Bue, Eiríksson, Eyþór Rúnar, Hansen, Hans Nørgaard, and Nielsen, Jakob Skov
- Subjects
- *
VIRTUAL machine systems , *KINEMATICS , *ROBOTS , *CALIBRATION , *ERROR analysis in mathematics - Abstract
A delta-type parallel kinematics system for Additive Manufacturing has been created, which through a probing system can recognise its geometrical deviations from nominal and compensate for these in the driving inverse kinematic model of the machine. Novelty is that this model is derived from a virtual machine of the kinematics system, built on principles from geometrical metrology. Relevant mathematically non-trivial deviations to the ideal machine are identified and decomposed into elemental deviations. From these deviations, a routine is added to a physical machine tool, which allows it to recognise its own geometry by probing the vertical offset from tool point to the machine table, at positions in the horizontal plane. After automatic calibration the positioning error of the machine tool was reduced from an initial error after its assembly of ±170 µm to a calibrated error of ±3 µm. Excelling by speed, the calibration was executed in less than 3 min. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
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- View/download PDF
30. 3D-printed temporal bone models for training: Does material transparency matter?
- Author
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Frithioff, Andreas, Weiss, Kenneth, Senn, Pascal, Mikkelsen, Peter Trier, Sørensen, Mads Sølvsten, Pedersen, David Bue, and Wuyts Andersen, Steven Arild
- Subjects
- *
RAPID prototyping , *THREE-dimensional printing , *MEDICAL cadavers , *MASTOIDECTOMY , *DISSECTION - Abstract
To investigate the impact of 3D-printed temporal bone models with two different material transparencies on trainees' mastoidectomy performance. Eleven ORL residents performed two anatomical mastoidectomies with posterior tympanotomy on two 3D-printed models with different transparency and VR simulation training. Participants where divided into two groups based on their experience. Within each group participants were randomized to start with the model printed in a completely opaque material or in a material featuring some degree of transparency. After drilling on 3D-printed models, the participants performed two similar mastoidectomies on human cadavers: one on the left side of one cadaver and one on the right side of another cadaver. After drilling 3D-printed models and cadavers, the final-product performances were evaluated by two experienced raters using the 26-item modified Welling Scale. Participants also evaluated the models using a questionnaire. Overall, the participants performed 25 % better on the 3D-printed models featuring transparency compared to the opaque models (18.6 points vs 14.9 points, mean difference = 3.7, 95 % CI 2.0–5.3, P < 0.001)). This difference in performance was independent of which material the participants had drilled first. In addition, the residents also subjectively rated the transparent model to be closer to cadaver dissection. The experienced group starting with the 3D-printed models scored 21.5 points (95 % CI 20.0–23.1), while the group starting with VR simulation training score 18.4 points (95 % CI 16.6–20.3). We propose that material used for 3D-printing temporal bone models should feature some degree of transparency, like natural bone, for trainees to learn and exploit key visual cues during drilling. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
31. Influence of thermal ageing on the fracture and lifetime of additively manufactured mold inserts.
- Author
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Davoudinejad, Ali, Khosravani, Mohammad Reza, Pedersen, David Bue, and Tosello, Guido
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FRACTOGRAPHY , *THERMOCYCLING , *INJECTION molding , *CHEMICAL molding , *SURFACE cracks , *SURFACE roughness , *THREE-dimensional printing - Abstract
• Fabrication of the components with injection molding (IM), soft tooling method. • Influence of thermal ageing on the fracture and lifetime behavior of polymer printed inserts. • The surface roughness of the unaged, aged before IM and aged after IM experiments were evaluated. • Measurement and comparison of the IM unaged and aged parts components. • Thermal ageing leads to crack formations in different areas in the mold inserts. Due to the significant technical benefits of additive manufacturing (AM), its application has grown considerably in recent years. In this respect, the integration of AM in the injection molding (IM) process chain for tooling purposes is an ongoing research topic. In the current study, the design, fabrication and use of a tool inserts for injection molding process fabricated by a vat photopolymerisation technique. Since molds during the injection molding process are subjected to cyclic thermal variation, accelerated thermal ageing was applied on the AM mold inserts to emulate the effect of continuous production on the tool lifetime. The additively manufactured mold inserts were exposed to thermal cycling loading in the range between room temperature up to 100 °C, and then, they were used in the actual injection molding process. According to the obtained results, effects of thermal ageing on behavior of the mold inserts are demonstrated. Moreover, fractographic analysis is performed on the fractured surfaces to determine crack initiation and propagation on the mold inserts. The current study provides insight about ageing and fracture of IM mold inserts produced by vat photopolymerisation , and these results can be used for the development of computational models, future material design and load-carrying capabilities of additively manufactured mold inserts to expand the use of AM for tooling purposes. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
32. Fabrication of micro-structured surfaces by additive manufacturing, with simulation of dynamic contact angle.
- Author
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Davoudinejad, Ali, Cai, Yukui, Pedersen, David Bue, Luo, Xichun, and Tosello, Guido
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CONTACT angle , *THREE-dimensional printing , *DYNAMIC simulation , *STEREOLITHOGRAPHY , *HYDROPHOBIC surfaces , *SURFACE roughness , *SURFACE structure - Abstract
This work presents an Additive Manufacturing (AM) based method for production of components with micro-structured surfaces. Vat photopolymerization was used for the experiments by an AM custom-build machine at the Technical University of Denmark (DTU). Components with micro holes were printed in different sizes and the uniformity of them analyzed. Subsequently, in order to assess the functionality of the surface, the water droplet contact angle was measured to evaluate the wettability of the different components with micro holes. It was found that it was possible to fabricate the components with micro holes using precision AM process. The printed substrate exhibited hydrophobicity as a hydrophilic material (intrinsic contact angle of 65°). A hydrophobic surface was achieved with the printed features exhibiting a maximum contact angle of 113°. Additionally, the volume of fluid (VOF) method was employed to predict the surface contact angle. The predicted results were validated by comparison against the experiments. The average value from experiments was predicted by the model. However, it was noted that the cross-sectional height profile of the structures and the surface roughness of the printed samples, were not precisely replicated as designed, which slightly affects the prediction results, though, similar prediction trend was observed. Unlabelled Image • Direct fabrication of the components with micro structured surfaces by digital light processing method. • Digital Light Processing method was pushed to its limit for fabrication of the components with micro holes. • Measurement of the components with micro holes present uniformity of the print in different areas of the structure. • The printed substrate realized hydrophobicity on the hydrophilic materials (intrinsic contact angle of 65°). • 3D dynamic impact behavior simulation for contact angle prediction was used to estimate wettability of the surface. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
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