Tesi sul tema "Hybrid additive manufacturing"
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1
Bandiera, Nicholas Graham. "Hybrid inkjet and direct-write multi-material additive manufacturing". Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/111774.
Abstract (sommario):
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 77-79).
Recently there has been a trend towards combining multiple forms of additive manufacturing together for increased functionality, freedom and efficiency. In this work, two forms of multiple-material additive manufacturing technologies - inkjet and direct-ink writing - are combined in a hybrid system. Several advantages are realized due to the increased material library and geometric freedom as a result of new printing modalities. Initially, models of each process are reviewed and the processes are evaluated for compatibility. Then, the precision machine design of a passively-indexed, carousel-style, syringe tool holder is completed. An error budget employing Homogeneous Transformation Matrices was maintained to estimate the tooltip errors. In order to register these two non-contact printing processes, a unique approach to their registration to a common global origin was necessary. A single non-contact optical CCD micrometer is used to register the three spatial coordinates of the syringe tooltip. Measurements are performed to characterize the repeatability of the nozzle registration scheme and the constructed gantry and carousel system, which well exceeds the requirements and the predictions from the conservative error budget. This novel system can print with a wide array of inks, including those that solidify via polymerization or crosslinking, two part chemistries, solvent evaporation or sintering, as well as liquids, gels and pastes. These materials can have a wide range of mechanical properties and functionalities, for example electrical conductivity or force sensitive resistivity. Models for the extrudate flow rate are used alongside experimental determination of the extrudate cross-section to ensure accurate process congruence. Finally, printed results demonstrate the various printing techniques, highlight the expanded material library, and display novel assemblies not possible with conventional additive processes. One such example is a fully printed pressure sensor array.
by Nicholas Graham Bandiera.
S.M.
2
Bandiera, Nicholas Graham. "Hybrid inkjet and direct-write multi-material additive manufacturing". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111774.
Abstract (sommario):
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 77-79).
Recently there has been a trend towards combining multiple forms of additive manufacturing together for increased functionality, freedom and efficiency. In this work, two forms of multiple-material additive manufacturing technologies - inkjet and direct-ink writing - are combined in a hybrid system. Several advantages are realized due to the increased material library and geometric freedom as a result of new printing modalities. Initially, models of each process are reviewed and the processes are evaluated for compatibility. Then, the precision machine design of a passively-indexed, carousel-style, syringe tool holder is completed. An error budget employing Homogeneous Transformation Matrices was maintained to estimate the tooltip errors. In order to register these two non-contact printing processes, a unique approach to their registration to a common global origin was necessary. A single non-contact optical CCD micrometer is used to register the three spatial coordinates of the syringe tooltip. Measurements are performed to characterize the repeatability of the nozzle registration scheme and the constructed gantry and carousel system, which well exceeds the requirements and the predictions from the conservative error budget. This novel system can print with a wide array of inks, including those that solidify via polymerization or crosslinking, two part chemistries, solvent evaporation or sintering, as well as liquids, gels and pastes. These materials can have a wide range of mechanical properties and functionalities, for example electrical conductivity or force sensitive resistivity. Models for the extrudate flow rate are used alongside experimental determination of the extrudate cross-section to ensure accurate process congruence. Finally, printed results demonstrate the various printing techniques, highlight the expanded material library, and display novel assemblies not possible with conventional additive processes. One such example is a fully printed pressure sensor array.
by Nicholas Graham Bandiera.
S.M.
3
Joshi, Anay. "Geometric Complexity based Process Selection and Redesign for Hybrid Additive Manufacturing". University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin151091601846356.
4
Strong, Danielle B. "Analysis of AM Hub Locations for Hybrid Manufacturing in the United States". Youngstown State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1495202496133841.
5
Gamaralalage, Sanjeewa S. J. "Additive Based Hybrid Manufacturing Workstations to Reuse and Repair PrismaticPlastic Work Parts". Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1480512115077584.
6
Momsen, Timothy Benjamin. "Hybrid additive manufacturing platform for the production of composite wind turbine blade moulds". Thesis, Nelson Mandela Metropolitan University, 2017. http://hdl.handle.net/10948/19091.
Abstract (sommario):
This dissertation discusses the application of additive manufacturing technologies for production of a large-scale rapid prototyping machine, which will be used to produce moulds for prototype composite turbine blades for the emerging renewables energy industry within the Eastern Cape region in South Africa. The conceptualization and design of three complete printer builds resulted in the amalgamation of a final system, following stringent theoretical design, simulation, and feasibility analysis. Following the initial product design cycle stage, construction and performance testing of a large-scale additive manufacturing platform were performed. In-depth statistical analysis of the mechatronic system was undertaken, particularly related to print-head locational accuracy, repeatability, and effects of parameter variation on printer performance. The machine was analysed to assess feasibility for use in the mould-making industry with accuracy and repeatability metrics of 0.121 mm and 0.156 mm rivalling those produced by some of the more accurate fused deposition modellers commercially available. The research data gathered serves to confirm that rapid prototyping is a good alternative manufacturing method for wind turbine blade plug and mould production.
7
Northrup, Nathan Joseph. "Durability of Hybrid Large Area Additive Tooling for Vacuum Infusion of Composites". BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7759.
Abstract (sommario):
The purpose of this research was to scientifically validate potential cost-saving measures for production of large area additively manufactured tooling for vacuum infusion of composites. These cost saving measures included using a hybrid additive/subtractive manufacturing system to fabricate the mold, requiring lower capital cost and creating shorter lead times. Fiberglass reinforcement was used instead of carbon in the mold material. The validation was done by designing and fabricating a mold for a custom test artifact and analyzing the surface geometry over the course of multiple infusions until tool failure.After printing and machining, the mold required a sealer in order to maintain vacuum integrity. The mold was able to produce 10 parts successfully before the sealed tool surface began to tangibly roughen, resulting in increased difficulty of demolding and a rougher surface finish. After the 14th infusion, the part required destructive force to be removed from the mold. The surface geometry remained consistent within ±0.5 mm of the design over the course of the infusions, and no significant trends in tool wear were observed during this time. In order to quantify the change in roughness, profilometry measurements were taken on the finished mold, and the measured area roughness value SA changed from 0.293 μm to 2.27 μm over the course of the infusions.Based on these results, it was concluded that an increase in surface adhesion is the principal mode of tool failure over the life of these tools. In addition, it was concluded that the minimum tool life for this combination of mold making methods and materials is 14 parts, as this result was obtained under an extreme case in abrasive part geometry and materials for vacuum infusion processing. Thus, this combination of methods and materials is suitable for prototyping of composite parts or short production runs.
8
Perini, Matteo. "Additive manufacturing for repairing: from damage identification and modeling to DLD processing". Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/268434.
Abstract (sommario):
The arrival on the market of a new kind of CNC machines which can both add and remove material to an object paved the way to a new approach to the problem of repairing damaged components. The additive operation is performed by a Direct Laser Deposition (DLD) tool, while the subtractive one is a machining task. Up to now, repair operations have been carried out manually and for this reason they are errors prone, costly and time consuming. Refurbishment can extend the life of a component, saving raw materials and resources. For these reasons, using a precise and repeatable CNC machine to repair valuable objects is therefore very attractive for the sake of reliability and repeatability, but also from an economical and environmental point of view. One of the biggest obstacles to the automation of the repairing process is represented by the fact that the CAM software requires a solid CAD model of the damage to create the toolpaths needed to perform additive operations. Using a 3D scanner the geometry of the damaged component can be reconstructed without major difficulties, but figuring out the damage location is rather difficult. The present work proposes the use of octrees to automatically detect the damaged spot, starting from the 3D scan of the damaged object. A software named DUOADD has been developed to convert this information into a CAD model suitable to be used by the CAM software.
DUOADD performs an automatic comparison between the 3D scanned model and the original CAD model to detect the damaged area. The detected volume is then exported as a STEP file suitable to be used directly by the CAM. The new workflow designed to perform a complete repair operation is described placing the focus on the coding part. DUOADD allows to approach the repairing problem from a new point of view which allows savings of time and financial resources.
The successful application of the entire process to repair a damaged die for injection molding is reported as a case study. In the last part of this work the strategies used to apply new material on the worn area are described and discussed. This work also highlights the importance of using optimal parameters for the deposition of the new material. The procedures to find those optimal parameters are reported, underlying the pros and cons. Although the DLD process is very energy efficient, some issues as thermal stresses and deformations are also reported and investigated, in an attempt to minimize their effects.
9
Perini, Matteo. "Additive manufacturing for repairing: from damage identification and modeling to DLD processing". Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/268434.
Abstract (sommario):
The arrival on the market of a new kind of CNC machines which can both add and remove material to an object paved the way to a new approach to the problem of repairing damaged components. The additive operation is performed by a Direct Laser Deposition (DLD) tool, while the subtractive one is a machining task. Up to now, repair operations have been carried out manually and for this reason they are errors prone, costly and time consuming. Refurbishment can extend the life of a component, saving raw materials and resources. For these reasons, using a precise and repeatable CNC machine to repair valuable objects is therefore very attractive for the sake of reliability and repeatability, but also from an economical and environmental point of view. One of the biggest obstacles to the automation of the repairing process is represented by the fact that the CAM software requires a solid CAD model of the damage to create the toolpaths needed to perform additive operations. Using a 3D scanner the geometry of the damaged component can be reconstructed without major difficulties, but figuring out the damage location is rather difficult. The present work proposes the use of octrees to automatically detect the damaged spot, starting from the 3D scan of the damaged object. A software named DUOADD has been developed to convert this information into a CAD model suitable to be used by the CAM software.
DUOADD performs an automatic comparison between the 3D scanned model and the original CAD model to detect the damaged area. The detected volume is then exported as a STEP file suitable to be used directly by the CAM. The new workflow designed to perform a complete repair operation is described placing the focus on the coding part. DUOADD allows to approach the repairing problem from a new point of view which allows savings of time and financial resources.
The successful application of the entire process to repair a damaged die for injection molding is reported as a case study. In the last part of this work the strategies used to apply new material on the worn area are described and discussed. This work also highlights the importance of using optimal parameters for the deposition of the new material. The procedures to find those optimal parameters are reported, underlying the pros and cons. Although the DLD process is very energy efficient, some issues as thermal stresses and deformations are also reported and investigated, in an attempt to minimize their effects.
10
Juhasz, Michael J. "In and Ex-Situ Process Development in Laser-Based Additive Manufacturing". Youngstown State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ysu15870552278358.
11
Falck, Rielson [Verfasser]. "A new additive manufacturing technique for layered metal-composite hybrid structures / Rielson Miler Moreira Falck". Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2020. http://d-nb.info/1224270835/34.
12
Maturi, Mirko <1993>. "Advanced Functional Organic-Inorganic Hybrid (Nano)Materials: from Theranostics to Organic Electronics and Additive Manufacturing". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9739/1/Maturi_Mirko_tesi.pdf.
Abstract (sommario):
This work is going to show the activities performed in the frame of my PhD studies at the University of Bologna, under the supervision of Prof. Mauro Comes Franchini, at the Department of Industrial Chemistry “Toso Montanari”. The main topic of this dissertation will be the study of organic-inorganic hybrid nanostructures and materials for advanced applications in different fields of materials technology and development such as theranostics, organic electronics and additive manufacturing, also known as 3D printing.
This work is therefore divided into three chapters, that recall the fundamentals of each subject and to recap the state-of-the-art of scientific research around each topic. In each chapter, the published works and preliminary results obtained during my PhD career will be discussed in detail.
13
Gingerich, Mark Bryant. "Joining Carbon Fiber and Aluminum with Ultrasonic Additive Manufacturing". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461161262.
14
Chamberlain, Britany L. "Additively-Manufactured Hybrid Rocket Consumable Structure for CubeSat Propulsion". DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7285.
Abstract (sommario):
Three-dimensional, additive printing has emerged as an exciting new technology for the design and manufacture of small spacecraft systems. Using 3-D printed thermoplastic materials, hybrid rocket fuel grains can be printed with nearly any cross-sectional shape, and embedded cavities are easily achieved. Applying this technology to print fuel materials directly into a CubeSat frame results in an efficient, cost-effective alternative to existing CubeSat propulsion systems. Different 3-D printed materials and geometries were evaluated for their performance as propellants and as structural elements. Prototype "thrust columns" with embedded fuel ports were printed from a combination of acrylonitrile utadiene styrene (ABS) and VeroClear, a photopolymer substitute for acrylic. Gaseous oxygen was used as the oxidizer for hot-fire testing of prototype thrusters in ambient and vacuum conditions. Hot-fire testing in ambient and vacuum conditions on nine test articles with a combined total of 25 s burn time demonstrated performance repeatability. Vacuum specific impulse was measured at over 167 s and maximum thrust of individual thrust columns at 9.5 N. The expected ΔV to be provided by the four thrust columns of the consumable structure is approximately 37 m/s. With further development and testing, it is expected that the consumable structure has the potential to provide a much-needed propulsive solution within the CubeSat community with further applications for other small satellites.
15
Zhu, Zicheng. "A process planning approach for hybrid manufacture of prismatic polymer components". Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648939.
Abstract (sommario):
The 21st century demand for innovation is leading towards a revolution in the way products are perceived. This will have a major impact on manufacturing technologies as current product innovation is constrained by the available manufacturing processes, which function independently. One of the most significant developments is the emergence of hybrid manufacturing technologies integrating various individual manufacturing processes. Hybrid processes utilise the advantages of the independent processes whilst minimising their weaknesses as well as extending application areas. Despite the fact that the drawbacks of the individual processes have been significantly reduced, the application of state of the art hybrid technology has always been constrained by the capabilities of their constituent processes either from technical limitations or production costs. In particular, it is virtually impossible to machine complex parts due to limited cutting tool accessibility. By contrast, additive manufacturing (AM) techniques completely solve the tool accessibility issue, but this increased flexibility and automation is achieved by compromising on part accuracy and surface quality. Furthermore, the shape and size of raw materials have to be specific for each hybrid process. More importantly, process planning methods capable of effectively utilising manufacturing resources for hybrid processes are highly limited. In this research, a hybrid process, entitled iAtractive, combining additive, subtractive and inspection processes is proposed. An experimental methodology has been designed and implemented, by which a generative reactionary process planning algorithm (GRP2A) and feature-based decision-making logic (FDL) is developed. GRP2A enables a complex part to be accurately manufactured as one complete unit in the shortest production time possible. FDL provides a number of manufacturing strategies, allowing existing parts to be reused and transformed into final parts with additional features and functionalities. A series of case studies have been manufactured from zero and existing parts, demonstrating the efficacy of the iAtractive process and the developed GRP2A and FDL, which are based on a manual process. The major contribution to knowledge is the new vision for a hybrid process, which is not constrained by the capability of the individual processes and raw material in terms of shape and size. It has been demonstrated that the hybrid process together with GRP2A and FDL provides an effective solution to flexibly and accurately manufacture complex part geometries as well as remanufacture existing parts.
16
Almerbati, Nehal. "Hybrid heritage : an investigation into the viability of 3D-printed Mashrabiya window screens for Bahraini dwellings". Thesis, De Montfort University, 2016. http://hdl.handle.net/2086/12482.
Abstract (sommario):
Current debates on design and manufacturing support the claim that the ‘Third Industrial Revolution’ has already started due to Additive Manufacturing (AM) and 3D Printing. The process of solidifying liquid or powder using a binding agent or a melting laser can save time and transportation costs associated with importing primary material if locally sourced material is available. This research investigates a framework approach, titled SAFE, for discussing the functionality, economic viability, production feasibility, and aesthetic and cultural value lent by 3D printing on an architectural scale through a construction known as a Mashrabiya. This traditional window screen has distinguished aesthetic, cultural yet functional constraints, and there is a manufacturing gap in the market that makes it a viable product option to be 3D printed. The practical element and design process related to reviving this screen are examined, from complex geometry development to cost and fabrication estimations. 3D printing technologies potentially offer solutions to solve issues in construction and assembly times, reduce labour costs, and address the loss of hand craft making skills in a variety of cultures, typically Middle Eastern ones; this was a factor in the abandonment of old Mashrabiya in houses typified with Bahrain as a case. Presently, there is a growing wealth of literature that highlights not only the strength of Mashrabiya as a design concept but also as a possible 3D printed product. Interviews with a total of 42 local Bahraini manufacturers, academics and architects as well as 4 case studies and 2 surveys and 11 focus groups are hybrid mixed methods used to define a new 3D printed Mashrabiya (3DPM) prototype. The future of the 3D Mashrabiya prototype is further supported by economic forecasts, market research, and interviews with global manufacturers and 3D printing designers’ insights into the subject in an accretive design process. The research contributes to an understanding of the implications of technologies that enable mass customisation in the field of 3D-printed architecture in general and in the Bahraini market in particular. The process for developing a prototype screen and in determining its current economic value will prove significant in predicting the future benefits and obstacles of 3D-printed large scale architectural products in the coming five years as advised by industry experts. The main outcomes relate to establishing boundaries determining the validity of using 3D printing and a SAFE framework to produce a parametric Mashrabiya and other similar heritage architectural archetypes. This can be used to enhance the globalism of the design of Middle Eastern dwellings and to revive social identity and cultural traditions through innovative and reasonable yet superior design solutions using a hybrid architectural design language.
17
Habib, MD Ahasan. "Designing Bio-Ink for Extrusion Based Bio-Printing Process". Diss., North Dakota State University, 2019. https://hdl.handle.net/10365/32045.
Abstract (sommario):
Tissue regeneration using in-vitro scaffold becomes a vital mean to mimic the in-vivo counterpart due to the insufficiency of animal models to predict the applicability of drug and other physiological behavior. Three-dimensional (3D) bio-printing is an emerging technology to reproduce living tissue through controlled allocation of biomaterial and cell. Due to its bio-compatibility, natural hydrogels are commonly considered as the scaffold material in bio-printing process. However, repeatable scaffold structure with good printability and shape fidelity is a challenge with hydrogel material due to weak bonding in polymer chain. Additionally, there are intrinsic limitations for bio-printing of hydrogels due to limited cell proliferation and colonization while cells are immobilized within hydrogels and don’t spread, stretch and migrate to generate new tissue. The goal of this research is to develop a bio-ink suitable for extrusion-based bio-printing process to construct 3D scaffold. In this research, a novel hybrid hydrogel, is designed and systematic quantitative characterization are conducted to validate its printability, shape fidelity and cell viability. The outcomes are measured and quantified which demonstrate the favorable printability and shape fidelity of our proposed material. The research focuses on factors associated with pre-printing, printing and post-printing behavior of bio-ink and their biology. With the proposed hybrid hydrogel, 2 cm tall acellular 3D scaffold is fabricated with proper shape fidelity. Cell viability of the proposed material are tested with multiple cell lines i.e. BxPC3, prostate stem cancer cell, HEK 293, and Porc1 cell and about 90% viability after 15-day incubation have been achieved. The designed hybrid hydrogel demonstrate excellent behavior as bio-ink for bio-printing process which can reproduce scaffold with proper printability, shape fidelity and higher cell survivability. Additionally, the outlined characterization techniques proposed here open-up a novel avenue for quantifiable bio-ink assessment framework in lieu of their qualitative evaluation.
18
Chen, Tianran. "Generation of Recyclable Liquid Crystalline Polymer Reinforced Composites for Use in Conventional and Additive Manufacturing Processes". Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103439.
Abstract (sommario):
The application of glass fiber reinforced composites has grown rapidly due to their high strength-to-weight ratio, low cost, and chemical resistance. However, the increasing demand for fiber reinforced composites results in the generation of more composite wastes. Mechanical recycling is a cost-effective and environmentally-friendly recycling method, but the loss in the quality of recycled glass or carbon fiber composite hinders the wide-spread use of this recycling method. It is important to develop novel composite materials with higher recyclability. Thermotropic liquid crystalline polymers (TLCPs) are high-performance engineering thermoplastics, which have comparable mechanical performance to that of glass fiber. The TLCP reinforced composites, called in situ composites, can form the reinforcing TLCP fibrils during processing avoiding the fiber breakage problem.
The first part of this dissertation is to study the influence of mechanical recycling on the properties of injection molded TLCP and glass fiber (GF) reinforced polypropylene (PP). The processing temperature of the injection molding process was optimized using a differential scanning calorimeter (DSC) and a rheometer to minimize the thermal degradation of PP. The TLCP and GF reinforced PP materials were mechanically recycled up to three times by repeated injection molding and grinding. The mechanical recycling had almost no influence on the mechanical, thermal, and thermo-mechanical properties of TLCP/PP because of the regeneration of TLCP fibrils during the mold filling process. On the other hand, glass fiber/PP composites decreased 30% in tensile strength and 5% in tensile modulus after three reprocessing cycles. The micro-mechanical modeling demonstrated the deterioration in mechanical properties of GF/PP was mainly attributed to the fiber breakage that occurred during compounding and grinding.
The second part of this dissertation is concerned with the development of recyclable and light weight hybrid composites through the use of TLCP and glass fiber. Rheological tests were used to determine the optimal processing temperature of the injection molding process. At this processing temperature, the thermal degradation of matrix material was mitigated and the processability of the hybrid composite was improved. The best formulation of TLCP and glass fiber in the composite was determined giving rise to the generation of a recyclable hybrid composite with low melt viscosity, low mechanical anisotropy, and improved mechanical properties.
Finally, TLCP reinforced polyamide composites were utilized in an additive manufacturing application. The method of selecting the processing temperature to blend TLCP and polyamide in the dual extrusion process was devised using rheological analyses to take advantage of the supercooling behavior of TLCP and minimize the thermal degradation of the matrix polymer. The composite filament prepared by dual extrusion was printed and the printing temperature of the composite filament that led to the highest mechanical properties was determined. Although the tensile strength of the TLCP composite was lower than the glass fiber or carbon fiber composites, the tensile modulus of 3D printed 60 wt% TLCP reinforced polyamide was comparable to traditional glass or carbon fiber reinforced composites in 3D printing.Doctor of Philosophy
The large demand for high performance and light weight composite materials in various industries (e.g., automotive, aerospace, and construction) has resulted in accumulation of composite wastes in the environment. Reuse and recycling of fiber reinforced composites are beneficial from the environmental and economical point of view. However, mechanical recycling deteriorates the quality of traditional fiber reinforced composite (e.g., glass fiber and carbon fiber). There is a need to develop novel composites with greater recyclability and high-performance. Thermotropic liquid crystalline polymers (TLCP) are attractive high performance materials because of their excellent mechanical properties and light weight. The goal of this work is to generate recyclable thermotropic liquid crystalline polymer (TLCP) reinforced composites for use in injection molding and 3D printing. In the first part of this work, a novel recyclable TLCP reinforced composite was generated using the grinding and injection molding. Recycled TLCP composites were as strong as the virgin TLCP composites, and the mechanical properties of TLCP composites were found to be competitive with the glass fiber reinforced counterparts. In the second part, a hybrid TLCP and glass fiber reinforced composite with great recyclability and excellent processability was developed. The processing conditions of injection molding were optimized by rheological tests to mitigate fiber breakage and improve the processability. Finally, a high performance and light weight TLCP reinforced composite filament was generated using the dual extrusion process which allowed the processing of two polymers with different processing temperatures. This composite filament could be directly 3D printed using a benchtop 3D printer. The mechanical properties of 3D printed TLCP composites could rival 3D printed traditional fiber composites but with the potential to have a wider range of processing shapes.
19
Liu, Fengyuan. "Design, fabrication and evaluation of a hybrid biomanufacturing system for tissue engineering". Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/design-fabrication-and-evaluation-of-a-hybrid-biomanufacturing-system-for-tissue-engineering(13717125-61ac-4f95-a83b-62a706a5ea15).html.
Abstract (sommario):
The combined use of additive manufacturing (AM), biocompatible and biodegradable materials, cells and biomolecular signals is the most common biomanufacturing strategy applied in scaffold fabrication. AM processes offer a better control and the ability to actively design the porosity and interconnectivity of the scaffolds. When combined with clinical imaging data, these fabrication techniques can be used to produce constructs that are customised to the shape of the defect or injury. However, due to the hydrophobicity of the commonly used synthetic biopolymers, cell-seeding and proliferation efficiency are limited. Moreover, due to the tortuosity of the scaffolds, non-uniform cell distribution with rare cell adhesion in the core region also commonly exists. Additionally, the commercial available machines are not able to create multi-material and material gradient scaffolds that are required to mimic the nature of nature tissues. To overcome the above limitations, this thesis describes the development of a hybrid bio-additive manufacturing system, called plasma-assisted bioextruson system (PABS), to produce smart scaffold by combining multi-head polymer extrusion and the plasma surface modification layer by layer, in the same chamber. PABS allows not only multiple biomaterials printing with the multi-extrusion heads, but also enables in-process plasma surface modification for zonal plasma-treated scaffolds fabrication. The in-house user interface enables a high degree of scaffold design freedom as it allows users to create single or multi-material constructs with uniform pore size or pore size gradient by changing process parameters such as lay-down pattern, filament distance, feed rate and layer thickness. Water contact angle tests and in vitro biological tests confirm that the hydrophilicity of synthetic polymers is improved and cell attachment and proliferation are enhanced after the in-process plasma modification. The effect of plasma treatment is also investigated by using different plasma modification strategies and various plasma modification parameters, including the plasma deposition velocity and the distance between the plasma jet and the printed scaffolds. The biological results also show dependence between the surface modification strategies and cell proliferation. The mechanical compression results show that for a fixed plasma deposition velocity, the effect of changing the distance between the plasma head and the deposited material is not significant. However, for a fixed distance, the compressive modulus increases with the increase in the plasma deposition velocity.
20
Lan, Di. "Development of 3-D Printed Hybrid Packaging for GaAs-MEMS Oscillators based on Piezoelectrically-Transduced ZnO-on-SOI Micromechanical Resonators". Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7690.
Abstract (sommario):
Prior research focused on CMOS-MEMS integrated oscillator has been done using various foundry compatible integration techniques. In order to compensate the integration compatibility, MEMS resonators built on standard CMOS foundry process could not take full advantage of highest achievable quality factor on chip. System-in-package (SiP) and system-on-chip (SoC) is becoming the next generation of electronic packaging due to the need of multi-functional devices and multi-sensor systems, thus wafer level hybrid integration becomes the key to enable the full assembly of dissimilar devices. In this way, every active circuit and passive component can be individually optimized, so do the MEMS resonators and sustaining amplifier circuits. In this dissertation, GaAs-MEMS integrated oscillator in a hybrid packaging has been fully explored as an important functional block in the RF transceiver systems.
This dissertation first presents design, micro-fabrication, simulation, testing and modeling of ZnO piezoelectrically-transduced MEMS resonators. A newly designed rectangular plate with curved resonator body fabricated in-house exhibits a very high Q of more 6,000 in the air for its width-extensional mode resonance at 166 MHz. In addition, a rectangular plate resonator with multiple Phononic Crystal (PC) strip tethers shows low insertion loss of -11.5 dB at 473.9 MHz with a Q of 2722.5 in the air. An oscillator technology with high-Q MEMS resonator as its tank circuit is presented to validate its key functionality as a stable frequency reference across a wide spectrum of frequencies. Particularly, a piezoelectrically-transduced width-extensional mode MEMS resonator is strategically designed to operate at two distinct layout-defined mechanical modal frequencies (259.5MHz and 436.7MHz). These devices were characterized and modeled by an extracted equivalent LCR circuit to facilitate the design of the oscillator using a standard circuit simulator. MEMS resonators have been integrated with the sustaining amplifier circuit at PCB level using wire-bonding technique and coaxial connectors. As shown by the time-domain measurements and frequency-domain measurements, these oscillators are capable of selectively locking into the resonance frequency of the tank circuit and generating a stable sinusoidal waveform. Meanwhile, the phase noise performance is rigorously investigated within a few oscillator designs. At last, 3-D printed hybrid packaging using additive manufacturing and laser machining technique has been developed for integrating a MEMS resonator on a silicon-on-insulator (SOI) substrate and a GaAs sustaining amplifier. Fabrication process and fundamental characterization of this hybrid packaging has been demonstrated. On-wafer probe measurements of a 50 Ω microstrip line on ABS substrate exhibit its insertion loss of 0.028 dB/mm at 5 GHz, 0.187 dB/mm at 20 GHz and 0.512 dB/mm at 30 GHz, and show satisfactory input and output return loss with the 3-D printed package. Parylene N is also experimentally coated on the package for improving water resistance as a form of hermetic packaging.
21
Mathias, Spencer D. "Investigation of Thermoplastic Polymers and Their Blends for Use in Hybrid Rocket Combustion". DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7416.
Abstract (sommario):
This thesis set out to find a blend of thermoplastics that had better combustion properties than the current ABS (acrylonitrile butadiene styrene) plastic or “Lego TM plastic” used by Utah State University. The current work is in an effort to eliminate toxic propellants from small space applications. High and low density polyethylene plastics were used because they are common plastic waste items. In this way rocket fuel can be made from these items to reduce the waste found in landfills. Three plastics were considered for replacement and as mixture components with the ABS plastic, namely low and high density polyethylene, and high impact polystyrene. These plastics failed to have superior combustion properties when used in rockets designed to achieve 12 pounds or less of thrust compared to the current ABS plastic.
22
Neff, Clayton. "Analysis of Printed Electronic Adhesion, Electrical, Mechanical, and Thermal Performance for Resilient Hybrid Electronics". Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7551.
Abstract (sommario):
Today’s state of the art additive manufacturing (AM) systems have the ability to fabricate multi-material devices with novel capabilities that were previously constrained by traditional manufacturing. AM machines fuse or deposit material in an additive fashion only where necessary, thus unlocking advantages of mass customization, no part-specific tooling, near arbitrary geometric complexity, and reduced lead times and cost. The combination of conductive ink micro-dispensing AM process with hybrid manufacturing processes including: laser machining, CNC machining, and pick & place enables the fabrication of printed electronics. Printed electronics exploit the integration of AM with hybrid processes and allow embedded and/or conformal electronics systems to be fabricated, which overcomes previously limited multi-functionality, decreases the form factor, and enhances performance. However, AM processes are still emerging technologies and lack qualification and standardization, which limits widespread application, especially in harsh environments (i.e. defense and industrial sectors).
This dissertation explores three topics of electronics integration into AM that address the path toward qualification and standardization to evaluate the performance and repeatable fabrication of printed electronics for resilience when subjected to harsh environments. These topics include: (1) the effect of smoothing processes to improve the as-printed surface finish of AM components with mechanical and electrical characterization—which highlights the lack of qualification and standardization within AM printed electronics and paves the way for the remaining topics of the dissertation, (2) harsh environmental testing (i.e. mechanical shock, thermal cycling, die shear strength) and initiation of a foundation for qualification of printed electronic components to demonstrate survivability in harsh environments, and (3) the development of standardized methods to evaluate the adhesion of conductive inks while also analyzing the effect of surface treatments on the adhesive failure mode of conductive inks.
The first topic of this dissertation addresses the as-printed surface roughness from individually fusing lines in AM extrusion processes that create semi-continuous components. In this work, the impact of surface smoothing on mechanical properties and electrical performance was measured. For the mechanical study, surface roughness was decreased with vapor smoothing by 70% while maintaining dimensional accuracy and increasing the hermetic seal to overcome the inherent porosity. However, there was little impact on the mechanical properties. For the electrical study, a vapor smoothing and a thermal smoothing process reduced the surface roughness of the surfaces of extruded substrates by 90% and 80% while also reducing measured dissipative losses up to 24% and 40% at 7 GHz, respectively.
The second topic of this dissertation addresses the survivability of printed electronic components under harsh environmental conditions by adapting test methods and conducting preliminary evaluation of multi-material AM components for initializing qualification procedures. A few of the material sets show resilience to high G impacts up to 20,000 G’s and thermal cycling in extreme temperatures (-55 to 125ºC). It was also found that coefficient of thermal expansion matching is an important consideration for multi-material printed electronics and adhesion of the conductive ink is a prerequisite for antenna survivability in harsh environments.
The final topic of this dissertation addresses the development of semi-quantitative and quantitative measurements for standardizing adhesion testing of conductive inks while also evaluating the effect of surface treatments. Without standard adhesion measurements of conductive inks, comparisons between materials or references to application requirements cannot be determined and limit the adoption of printed electronics. The semi-quantitative method evolved from manual cross-hatch scratch testing by designing, printing, and testing a semi-automated tool, which was coined scratch adhesion tester (SAT). By cross-hatch scratch testing with a semi-automated device, the SAT bypasses the operator-to-operator variance and allows more repeatable and finer analysis/comparison across labs. Alternatively, single lap shear testing permits quantitative adhesion measurements by providing a numerical value of the nominal interfacial shear strength of a coating upon testing while also showing surface treatments can improve adhesion and alter the adhesive (i.e. the delamination) failure mode of conductive inks.
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Armstrong, Isaac W. "Development and Testing of Additively Manufactured Aerospike Nozzles for Small Satellite Propulsion". DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7428.
Abstract (sommario):
Automatic altitude compensation has been a holy grail of rocket propulsion for decades. Current state-of-the-art bell nozzles see large performance decreases at low altitudes, limiting rocket designs, shrinking payloads, and overall increasing costs. Aerospike nozzles are an old idea from the 1960’s that provide superior altitude-compensating performance and enhanced performance in vacuum, but have survivability issues that have stopped their application in satellite propulsion systems. A growing need for CubeSat propulsion systems provides the impetus to study aerospike nozzles in this application. This study built two aerospike nozzles using modern 3D metal printing techniques to test aerospikes at a size small enough to be potentially used on a CubeSat. Results indicated promising in-space performance, but further testing to determine thermal limits is deemed necessary.
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Bradford-Vialva, Robyn L. "Development of a Metal-Metal Powder Formulations Approach for Direct Metal Laser Melting of High-Strength Aluminum Alloys". University of Dayton / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1620259752540201.
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Jacques, Marjorie. "Développement d'une méthode de conception de moules et noyaux hybrides en fonderie". Thesis, Reims, 2019. http://www.theses.fr/2019REIMS021.
Abstract (sommario):
Ces travaux de recherche ont pour objectif de définir une méthodologie de conception de moules hybrides en fonderie. Cette méthodologie est définie à partir des limites technico-économiques des procédés traditionnels de moulage et de l’impression 3D sable. Dans un premier temps, ces limites sont évaluées par la caractérisation mécanique et dimensionnelle des moules imprimés. Cette caractérisation mécanique a été réalisée à partir d’essais de flexion 3 points et de compression en fonction de différents paramètres. La capabilité dimensionnelle de l’imprimante 3D a été évaluée par la mesure d’éprouvettes imprimées dans différentes directions. Dans un second temps, la méthode de conception des moules traditionnels a été formalisée à partir du recueil de l’expertise des partenaires fondeurs du projet ANR MONARCHIES et testée sur différents cas. Les règles métiers inhérentes à l’imprimante 3D sable ont été établies à partir des travaux du laboratoire ITHEMM et complétées par l’étude de pièces. Le processus de conception des moules imprimés a été élaboré à partir de ces règles métiers et validé sur des études de cas. Le coût de fabrication des moules imprimés a été défini par une méthode analytique et paramétrique. La méthodologie de conception des moules hybrides s’appuie sur l’ensemble des travaux précédents et sur la notion d’indice de complexité. En fonction de la valeur de ces indices de complexité, des contraintes de remmoulage et de coût de fabrication, le choix optimal du procédé de fabrication est défini pour les différentes parties du moule. Enfin, cette méthodologie a été testée sur un panel représentatif de pièces de fonderie permettant d’évaluer sa robustesseThe aim of this works is to define a design methodology of hybrids casting molds. This methodology is based on technical and economical limits of conventional process and 3D sand printing. Firstly, these limits were evaluated by mechanical and dimensional characterization of 3D sand printing molds. Mechanical characterization was realised by three points bending test and compression testing with different parameters. 3D printer dimensional capability was determined by samples measure printed in different directions. Secondly, the design method of conventional molds was established from smelters know-how which are ANR MONARCHIES project partner from different case study. Inherent design rules of sand 3D printer were defined from the ITHEMM laboratory research works and completed with parts studies. 3D printing molds design process was created by design rules and validated with studies cases. Manufacturing cost of printing molds was defined by analytic and parametric method. The hybrids molds design methodology relies on all previous works and on complexity index. Optimal manufacturing process for different molds parts was selected according to the complexity index value, mould assembly restraint and manufacturability cost. Finally, this methodology was tested on representative sample group of casting parts, allowed to evaluate the robustness
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Laplanche, Etienne. "Filtres à forts facteurs de qualité accordables continument". Thesis, Limoges, 2019. http://www.theses.fr/2019LIMO0064/document.
Abstract (sommario):
De nouveaux besoins dans le domaine des télécommunications par satellite ont amené les industriels du secteur à se pencher sur l’optimisation des ressources en créant des systèmes reconfigurables, capables d’adapter leur fonctionnement fréquentiel en cours de mission. Cette thèse s’intéresse plus particulièrement aux multiplexeurs et à la manière de les rendre agiles à travers les filtres qui les composent ainsi qu’une adaptation de leur architecture.Dans un premier temps, le présent manuscrit dresse l’état de l’art des dispositifs accordables réalisés par les équipes de recherche du monde entier, avant de proposer des solutions mettant en œuvre une topologie de multiplexage à coupleurs hybrides. Dans un second temps, des études sont présentées portant sur une pluralité de concepts de cavités ou d’éléments de couplage accordables. Certains de ces concepts sont ensuite sélectionnés et assemblés afin de former des fonctions de filtrage et de multiplexage accordables. La dernière partie présente ainsi deux multiplexeurs accordables, l’un permettant une reconfiguration en bande étroite, l’autre en bande large, le premier ayant donné lieu à une réalisation expérimentaleNew needs in the field of satellite telecommunications have led manufacturers in the sector to focus on optimizing resources by creating reconfigurable systems able to adapt their operating frequencyplan during the mission. This thesis focuses on multiplexers and how to make them agile through their architecture and the filters that compose them.This manuscript starts by realizing the state of the art oftunable filtering devices through analysis of contributions made by research teams around the world. Based on this state of art,solutions to the problematic are proposed using a hybrid coupler multiplexing topology. Then studies are presented on various tunable cavities or coupling elements concepts. Some of these concepts have been selected and assembled to form tunable filtering and multiplexing functions. The last part thus presents two tunable multiplexers, allowing narrowband or broadband reconfiguration. An experimental realization has also been conducted on the narrowband version
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Ushakov, Ilia. "Établissement des structures et propriétés mécaniques de l’alliage d’Inconel 625 dans les procédés d’élaboration additive à grande vitesse : arc fil, laser fil, laser poudre et hybride". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0147.
Abstract (sommario):
Ce travail porte sur l'étude de l'établissement des structures et la caractérisation des propriétés mécaniques d'alliage d'Inconel 625 produites dans le cadre du projet PAM-PROD visant à réaliser des pièces de grande dimension par élaboration additive à grande vitesse. Trois techniques de dépôt sont étudiées : Arc/Fil, Laser/Fil et Laser/Poudre ainsi que la combinaison Laser/Fil et Laser/Poudre pour réalisation d'un mur hybride. Pour chaque procédés les macrostructures et microstructures sont caractérisées. Les procédés Arc/Fil et Laser/Poudre utilisés conduisent à une macrostructure mixte colonnaire équiaxe. Le procédé Laser/Fil conduit à des structures majoritairement colonnaires. Des mécanismes de formation des structures et transitions colonnaires/équiaxes sont proposés. Ces mécanismes sont alors repris et complétés pour interpréter la formation de la zone de transition dans le cas d'un mur hybride Laser Fil/Poudre. La réponse au traitement thermique de mise en solution et vieillissement est ensuite présentée en détaillant et comparant les cinétiques et mécanismes propres à chaque procédé. Les propriétés mécaniques en traction suivant 3 directions sont alors caractérisées et reliées aux structures. Pour l'ensemble des procédés une grande reproductibilité est obtenue et aucun procédé ne présente de caractère fragile. Les meilleures propriétés sont obtenues avec le procédé Laser/Poudre et le test de la jonction hybride montre que la zone de transition ne présente pas un point faible dans la structureThis work focuses on the establishment of microstructures and the characterization of the mechanical properties of Inconel 625 alloy produced as part of the PAM-PROD project aimed at producing large parts using high deposition rate additive manufacturing. Three deposition techniques are being studied: Arc/Wire, Laser/Wire and Laser/Powder, as well as a combination of Laser/Wire and Laser/Powder to produce a hybrid wall. Macrostructures and microstructures are characterized for each process. The Arc/Wire and Laser/Powder processes used lead to a mixed columnar - equiaxed macrostructure. The Laser/Wire process leads to predominantly columnar structures. Mechanisms for the formation of columnar/equiaxed structures and transitions are proposed. These mechanisms are then taken up and completed to interpret the formation of the transition zone in the case of a hybrid Laser Wire/Powder wall. The response to solution heat treatment and ageing is then presented by detailing and comparing the kinetics and mechanisms specific to each process. The tensile mechanical properties along 3 directions are then characterized and related to the structures. For all the processes, a high degree of reproducibility is obtained and none of the processes has a brittle character. The best properties were obtained with the Laser/Powder process, and the hybrid junction test showed that the transition zone was not a weak point in the structure
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Keerthi, Sandeep. "Low Velocity Impact and RF Response of 3D Printed Heterogeneous Structures". Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1514392165695378.
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Silva, Eva Carolina Ferreira da. "Thermal performance of additive manufacturing materials for hybrid moulds". Master's thesis, 2018. http://hdl.handle.net/1822/65006.
Abstract (sommario):
Dissertação de mestrado integrado em Engenharia de PolímerosHybrid moulds are an increasingly considered alternative for prototype series or short production runs, where the moulding inserts are produced by Additive Manufacturing (AM) in alternative materials, namely polymers. However, one of the main issues associated with the use of these materials is their thermal behaviour due, mainly, to the low thermal conductivity values. This study aims to evaluate the thermal performance of moulding inserts produced via Rapid Prototyping (RP) and conventional manufacturing techniques as well as the resulting moulded part quality, supported by Computer-Aided Engineering (CAE) simulations results, through Moldex3D software. The first part of this research was centered on the analysis and characterization of eight different materials from three different technologies (Material Jetting, Fused Deposition Modelling (FDM) and Direct Metal Laser Sintering (DMLS)) in order to define the suitable materials to apply in hybrid moulds. Therefore this first investigation permitted to narrow the Additive Manufacturing (AM) materials to just two polymeric materials that were further studied. Three insert materials and technologies were evaluated: Objet500 Connex3 using Digital ABS Thin Walls, Fortus 900mc using PPSF and machining using P20 steel. Dimensional accuracy, temperatures along the cycles, longevity of the moulding inserts, part quality and shrinkage behaviour of Polyoxymethylene (POM) mouldings were recorded. In the end, it was found that PPSF moulding inserts had worse surface finishing than Digital ABS Thin Walls, which originated parts with worse quality. However, Digital ABS Thin Walls was suitable for this application and using spray air as a complement of cooling decreased significantly the cycle time and had not any consequences in the shrinkage of the moulded parts.
Os moldes híbridos são uma alternativa cada vez mais procurada para a produção de protótipos ou séries curtas, onde os insertos moldantes são produzidos por manufatura aditiva, em materiais alternativos, nomeadamente polímeros. No entanto, uma das principais questões associadas ao uso destes materiais é a sua performance térmica, principalmente ao nível da condutividade. Este estudo pretende não só avaliar e comparar a performance térmica de insertos moldantes produzidos por prototipagem rápida e por técnicas de maquinação convencionais, como também a qualidade da peça resultante. Estes resultados foram validados por simulações CAE, através do software Moldex3D. Assim, numa primeira fase, a pesquisa focou-se em analisar e caracterizar oito materiais distintos, de três tecnologias distintas (Material Jetting, FDM e DMLS) para aplicação em moldes híbridos. Estes resultados permitiram selecionar dois materiais poliméricos de manufatura aditiva, que continuaram a ser estudados. Posteriormente, foram avaliadas três tecnologias e materiais: Objet500 Connex3 com Digital ABS Thin Walls, Fortus 900mc com PPSF e maquinação convencional com aço P20, ao nível da precisão dimensional, temperaturas ao longo dos ciclos e longevidade dos insertos moldantes e a qualidade e contração das peças produzidas em POM. No final, observou-se que os insertos moldantes em PPSF tiveram pior acabamento superficial, o que originou peças com pior qualidade do que usando Digital ABS Thin Walls. Contudo, este último mostrou-se uma boa solução para aplicação em moldes híbridos e usar ar comprimido como complemento de arrefecimento diminui significativamente o tempo de ciclo, não trazendo consequências na contração das moldações.
This work was funded by National Funds through FCT - Portuguese Foundation for Science and Technology, Reference UID/CTM/50025/2013 and FEDER funds through the COMPETE 2020 Programme under the project number POCI-01-0145-FEDER-007688 and by the European Structural and Investment Funds in the FEDER component, through the Operational Competitiveness and Internationalization Programme (COMPETE 2020) [Project nº 002814; Funding Reference: POCI-01-0247-FEDER-002814 and Project nº 002797; Funding Reference: POCI-01-0247-FEDER-002797].
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Jayant, Hemang Kumar. "Design and Development of Hybrid Metal and Polymer Additive Manufacturing System". Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5854.
Abstract (sommario):
Additive manufacturing (AM) is a layer-based manufacturing process aimed at producing parts directly from a Computer-aided design (CAD) model. There are various types of AM systems, which can be classified based on: (i) the base material being used for fabrication, such as polymers, ceramics, and metals; (ii) indirect and direct processes depending on the bonding method; and (iii) the state of the input raw material, i.e., liquid, molten, powder, and solid layer. The current research in AM processes includes technology development for the printing of multi-material parts using two or more materials such as metal, polymer, glass, ceramics, and graphene. The multi-material additive manufacturing (MMAM) processes are complex and challenging due to the significant differences in material deposition techniques, material processing temperature, or pre/post-processing methods involved for an individual material. Our work focuses on the hybrid metal/polymer printing process where liquid metal printing is achieved using a novel design of a molten metal droplet-on-demand (MMDoD) system. The metal is fed into the MMDoD system in the form of solid wire and is melted using a zero-voltage-switching circuit based induction heater. The magnetic field, eddy current density, and power transfer from the induction coil to the molten metal pool are studied using experiments, theoretical formulation, and FEM simulations. The influence of workpiece geometry on the induction heating process is also studied for solder alloy and aluminum billets. These studies show that for a given geometry of induction coil and workpiece, the power transferred to the workpiece is a non-monotonic function of the workpiece’s resistivity. Also, the heating rate of the workpiece depends on the thermal mass and the magnetic field flux in and around the workpiece. Using these studies, the resistivity of the workpiece, and the geometry of the workpiece and induction coil, can be chosen to achieve faster heating and melting of the metal.
Once the raw material is in the liquid state, it can be used to generate molten metal droplets (MMDs). To generate the MMD, a novel MMDoD system is designed and developed using a thermally insulating piston and magnetostrictive actuator. Using the MMDoD mechanism, the molten metal is deposited on the printing bed surface (glass) or partially formed part (metal or polymer – PLA/ABS). To find the optimal parameters of MMD generation process, a parametric study of the MMDoD mechanism is conducted by varying the size and material (Brass, Stainless-Steel, Nickel-plated steel alloy) of the nozzle, the gap between nozzle and piston, unfiltered vs. low-pass filtered actuation pulse, and the actuation pulse amplitude. This shows the following regions where, DoD process is not achieved, and the DoD is achieved with the generation of single or multiple droplets for each actuation. The droplet size, Feret width and length, and standard deviation are measured using snapshots from the high-speed camera of the droplet formation process. The region where a single MMD is generated for each actuation of the MMDoD mechanism with the least standard deviation is most desirable for the reproducible metal AM process. A parametric study is conducted to find the optimal printing parameters of the metal AM system by varying the gap between each droplet to print the 2D connected metal lines on the substrate. Other parameters like the size of MMDs, droplet ejection rate (20Hz), and liquid metal temperature are kept fixed. The 3D metal printing can be achieved by printing these metal lines layer-by-layer.
MMDoD system is extended to multi-material additive manufacturing (MMAM) system by combining it with polymer extrusion system. The designed MMAM system consists of a controller board to control the overall system, an induction heater, a computer numeric control (CNC) build platform/positioning system, MMDoD mechanism, and the polymer extruder. The system is designed and developed to print metal (Solder alloys - Sn99Cu1, Sn63Pb37, and Sn96.5Ag3.5) with polymer (PLA and ABS). To demonstrate the hybrid AM of metal and polymer, a few mechanical structures (2D planar text, hollow tube, hollow square pyramid, hollow hexagon) and electronic device (RC-LED circuit) are fabricated. The deposition of molten metal on polymer substrate leads to good bonding of metal on polymer due to remelting of the polymer surface. The working of the printed, electronic device is tested and found satisfactory. The testing is conducted by checking the electrical connectivity along the track and the functionality of the electronic device by measuring the output signal waveform. In the future, the combined metal and polymer AM system can be combined with a pick-and-place mechanism that can help achieve a rapid AM of functional 3D electronic devices.
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Montevecchi, Filippo. "Analysis and optimization of hybrid WAAM-milling process". Doctoral thesis, 2018. http://hdl.handle.net/2158/1126901.
Abstract (sommario):
The hybrid additive-subtractive manufacturing processes combine the advantages provided by the metal additive manufacturing with the high accuracy of the machining processes. Among these technologies the combination of WAAM (Wire-Arc-Additive-Manufacturing) and milling is an attractive option. The WAAM process is a metal additive manufacturing technology that uses arc welding to create metal components. It provides a high deposition rate and enables to manufacture large components. It requires a reduced investment compared laser based technologies both in terms of installation and operation. Moreover, WAAM operations can be performed on existing machine tools by a simple retrofitting to provide them arc welding capability. Despite its advantages, the hybrid WAAM-milling process has several drawbacks which limit its diffusion among the manufacturing companies. The goal of the Ph.D. work presented in this thesis is to analyze such criticalities, proposing solutions to overcome or mitigate the process issues. Since the considered technology is a hybrid process, the overall performance depends on both the involved technologies. Hence, part of this thesis is strictly related to the WAAM process, while a further one is related to the milling of WAAM manufactured parts. For what concerns the WAAM process, this thesis is focused on the thermal issues induced by the arc welding. The heat input of the process can cause large distortions, residual stresses and even lead to the structural collapse of the workpiece. This thesis pinpoints the process simulation as an efficient and effective approach to overcome the WAAM thermal issues. The current simulation techniques are analyzed, proposing improvements that aim at increasing the simulation time efficiency without losing accuracy. The proposed modelling techniques are validated comparing simulations with the actual process, both in terms of temperature field and workpiece distortions, confirming their accuracy. The proposed simulation techniques are applied to tackle the heat accumulation issues, responsible for the structural collapse of WAAM workpieces. To overcome this issue, two different approaches are proposed: i) an innovative cooling system, developed by using the proposed simulation technique ii) a simulation-based algorithm to schedule inter-layer idle times for workpiece cooling. These techniques are validated by simulation and experiments, showing their effectiveness in preventing the detrimental effect of the heat accumulation phenomenon.
For what concerns the milling of WAAM components, this thesis pinpoints two main criticalities: the poor machinability of WAAM material and the issues related to machining the thin walled features of the WAAM workpieces. The machinability aspect is tackled by a comparative cutting force analysis on a reference material. This analysis highlights an increase of specific milling cutting forces on an AM processed material with respect to the traditional material. To overcome the issues related to thin walled features, the thesis proposes a spindle speed optimization algorithm based on FE modelling of the workpiece. The algorithm is experimentally validated, highlighting its accuracy in predicting the workpiece dynamics and comparing the results achieved by different optimization strategies. In summary, the aim of the thesis is to contribute to the development of the hybrid WAAM-milling, providing tools to support the process planning of such operations.
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(5929505), Eduardo Barocio. "FUSION BONDING OF FIBER REINFORCED SEMI-CRYSTALLINE POLYMERS IN EXTRUSION DEPOSITION ADDITIVE MANUFACTURING". Thesis, 2020.
Abstract (sommario):
Extrusion deposition additive manufacturing (EDAM) has enabled upscaling the dimensions of the objects that can be additively manufactured from the desktop scale to the size of a full vehicle. The EDAM process consists of depositing beads of molten material in a layer-by-layer manner, thereby giving rise to temperature gradients during part manufacturing. To investigate the phenomena involved in EDAM, the Composites Additive Manufacturing Research Instrument (CAMRI) was developed as part of this project. CAMRI provided unparalleled flexibility for conducting controlled experiments with carbon fiber reinforced semi-crystalline polymers and served as a validation platform for the work presented in this dissertation.
Since the EDAM process is highly non-isothermal, modeling heat transfer in EDAM is of paramount importance for predicting interlayer bonding and evolution of internal stresses during part manufacturing. Hence, local heat transfer mechanisms were characterized and implemented in a framework for EDAM process simulations. These include local convection conditions, heat losses in material compaction as well as heat of crystallization or melting. Numerical predictions of the temperature evolution during the printing process of a part were in great agreement with experimental measurements by only calibrating the radiation ambient temperature.
In the absence of fibers reinforcing the interface between adjacent layers, the bond developed through the polymer is the primary mechanisms governing the interlayer fracture properties in printed parts. Hence, a fusion bonding model was extended to predict the evolution of interlayer fracture properties in EDAM with semi-crystalline polymer composites. The fusion bonding model was characterized and implemented in the framework for EDAM process simulation. Experimental verification of numerical predictions obtained with the fusion bonding model for interlayer fracture properties is provided. Finally, this fusion bonding model bridges the gap between processing conditions and interlayer fracture properties which is extremely valuable for predicting regions with frail interlayer bond within a part.
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(9012281), Pasita Pibulchinda. "The Effects of Fiber Orientation State of Extrusion Deposition Additive Manufactured Fiber-Filled Thermoplastic Polymers". Thesis, 2020.
Abstract (sommario):
Extrusion Deposition Additive Manufacturing (EDAM) is a process in which fiber-filled thermoplastic polymers are mixed and melted in an extruder and deposited onto a build plate in a layer-by-layer basis. Anisotropy caused by flow-induced orientation of discontinuous fibers along with the non-isothermal cooling process gives rise to internal stresses in printed parts which results in part deformation. The deformation and residual stresses can be abated by modifying the fiber orientation in the extrudate to best suit the print geometry. To that end, the focus of this research is on understanding the effect of fiber orientation state and fiber properties on effective properties of the printed bead and the final deformation of a part. The properties of three different orientation tensors of glass fiber-filled polyamide and carbon fiber-filled polyamide were experimentally and virtually characterized via micromechanics. A thermo-mechanical simulation framework developed in ABAQUS© was used to understand the effects of the varying fiber orientation tensor and fiber properties on the final deformation of printed parts. In particular, a medium-size geometry that is prone to high deformation was simulated and compared among the three orientation tensors and two material systems. This serves to be a good preliminary study to understand microscopic properties induced deformations in EDAM.
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Oliveira, Hugo Miguel Lopes de. "Development, programming and start-up of an interchangeable 3D-printing module". Master's thesis, 2017. http://hdl.handle.net/10400.8/3254.
Abstract (sommario):
This report has as main objective the development and application of a 3D printing module (additive manufacturing) in a computer numeric control (CNC) milling machine (subtractive manufacturing) creating a hybrid manufacturing environment that could offer the advantages of both methods. Every CNC milling machine using this 3D printing module could be converted in a 3D printer by changing from a regular tool to the 3D printing module which is applied in the spindle of the machine in a very simple process. This module is equipped with a system capable of reading the spindle rotation speed, and uses that information to set up different commands and actions.
Focused in the development of a low-cost system, there is used an Arduino board to control all the systems needed to work with the module. Most of the parts of the module are printed in a 3D printer that uses the stereolithograph technology, being able to create parts with complex shapes, high precision and good surface finishing.
The experimental results obtained in the first tests were not as expected. Many problems that haven’t been taken in consideration when the initial development of the module was done. Many solutions were found and some corrections were done to eliminate or minimize those problems.
The temperature control system and the revolutions per minute reading system shown very good results in the experimental tests.
The biggest issue faced was related with filament feeding system. Many structural modifications were implemented to improve it, with better performance, obtaining acceptable final results, however with significant possibilities for improvement.
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(11189886), Diane Collard. "Enhancing Solid Propellants with Additively Manufactured Reactive Components and Modified Aluminum Particles". Thesis, 2021.
Abstract (sommario):
A variety of methods have been developed to enhance solid propellant burning rates, including adjusting oxidizer particle size, modifying metal additives, tailoring the propellant core geometry, and adding catalysts or wires. Fully consumable reactive wires embedded in propellant have been used to increase the burning rate by increasing the surface area; however, the manufacture of propellant grains and the observation of geometric effects with reactive components has been restricted by traditional manufacturing and viewing methods. In this work, a printable reactive filament was developed that is tailorable to a number of use cases spanning reactive fibers to photosensitive igniters. The filament employs aluminum fuel within a printable polyvinylidene fluoride matrix that can be tailored to a desired burning rate through stoichiometry or aluminum fuel configuration such as particle size and modified aluminum composites. The material is printable with fused filament fabrication, enabling access to more complex geometries such as spirals and branches that are inaccessible to traditionally cast reactive materials. However, additively manufacturing the reactive fluoropolymer and propellant together comes attendant with many challenges given the significantly different physical properties, particularly regarding adhesion. To circumvent the challenges posed by multiple printing techniques required for such dissimilar materials, the reactive fluoropolymer was included within a solid propellant carrier matrix as small fibers. The fibers were varied in aspect ratio (AR) and orientation, with aspect ratios greater than one exhibiting a self-alignment behavior in concordance with the prescribed extrusion direction. The effective burning rate of the propellant was improved nearly twofold with 10 wt.% reactive fibers with an AR of 7 and vertical orientation.
The reactive wires and fibers in propellant proved difficult to image in realistic sample designs, given that traditional visible imaging techniques restrict the location and dimensions of the reactive wire due to the necessity of an intrusive window next to the wire, a single-view dynamic X-ray imaging technique was employed to analyze the evolution of the internal burning profile of propellant cast with embedded additively manufacture reactive components. To image complex branching geometries and propellant with multiple reactive components stacked within the same line of sight, the dynamic X-ray imaging technique was expanded to two views. Topographic reconstructions of propellants with multiple reactive fibers showed the evolution of the burning surface enhanced by the geometric effects caused by the faster burning fibers. These dual-view reconstructions provide a method for accurate quantitative analysis of volumetric burning rates that can improve the accessibility and viability of novel propellant grain designs.
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(5931092), Ehsan Maleki Pour. "Innovative Tessellation Algorithm for Generating More Uniform Temperature Distribution in the Powder-bed Fusion Process". Thesis, 2019.
Abstract (sommario):
Powder Bed Fusion Additive Manufacturing enables the fabrication of metal parts with complex geometry and elaborates internal features, the simplication of the assembly process, and the reduction of development time. However, the lack of consis-tent quality hinders its tremendous potential for widespread application in industry. This limits its ability as a viable manufacturing process particularly in the aerospace and medical industries where high quality and repeatability are critical. A variety of defects, which may be initiated during the powder-bed fusion additive manufacturing process, compromise the repeatability, precision, and resulting mechanical properties of the final part. The literature review shows that a non-uniform temperature distribution throughout fabricated layers is a signicant source of the majority of thermal defects. Therefore, the work introduces an online thermography methodology to study temperature distribution, thermal evolution, and thermal specications of the fabricated layers in powder-bed fusion process or any other thermal inherent AM process. This methodology utilizes infrared technique and segmentation image processing to extract the required data about temperature distribution and HAZs of the layer under fabrication. We conducted some primary experiments in the FDM process to leverage the thermography technique and achieve a certain insight to be able to propose a technique to generate a more uniform temperature distribution. These experiments lead to proposing an innovative chessboard scanning strategy called tessellation algorithm, which can generate more uniform temperature distribution and diminish the layer warpage consequently especially throughout the layers with either geometry that is more complex or poses relatively longer dimensions. In the next step, this work develops a new technique in ABAQUS to verify the proposed scanning strategy. This technique simulates temperature distribution throughout a layer printed by chessboard printing patterns in powder-bed fusion process in a fraction of the time taken by current methods in the literature. This technique compares the temperature distribution throughout a designed layer printed by three presented chessboard-scanning patterns, namely, rastering pattern, helical pattern, and tessellation pattern. The results conrm that the tessellation pattern generates more uniform temperature distribution compared with the other two patterns. Further research is in progress to leverage the thermography methodology to verify the simulation technique. It is also pursuing a hybrid closed-loop online monitoring (OM) and control methodology, which bases on the introduced tessellation algorithm and online thermography in this work and Articial Neural Networking (ANN) to generate the most possible uniform temperature distribution within a safe temperature range layer-by-layer.
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Maleki, Pour Ehsan. "Innovative Tessellation Algorithm for Generating More Uniform Temperature Distribution in the Powder-bed Fusion Process". Thesis, 2018. http://hdl.handle.net/1805/17386.
Abstract (sommario):
Purdue School of Engineering and Technology, IndianapolisPowder Bed Fusion Additive Manufacturing enables the fabrication of metal parts with complex geometry and elaborates internal features, the simplification of the assembly process, and the reduction of development time. However, the lack of consistent quality hinders its tremendous potential for widespread application in industry. This limits its ability as a viable manufacturing process particularly in the aerospace and medical industries where high quality and repeatability are critical. A variety of defects, which may be initiated during the powder-bed fusion additive manufacturing process, compromise the repeatability, precision, and resulting mechanical properties of the final part. The literature review shows that a non-uniform temperature distribution throughout fabricated layers is a significant source of the majority of thermal defects. Therefore, the work introduces an online thermography methodology to study temperature distribution, thermal evolution, and thermal specifications of the fabricated layers in powder-bed fusion process or any other thermal inherent AM process. This methodology utilizes infrared technique and segmentation image processing to extract the required data about temperature distribution and HAZs of the layer under fabrication. We conducted some primary experiments in the FDM process to leverage the thermography technique and achieve a certain insight to be able to propose a technique to generate a more uniform temperature distribution. These experiments lead to proposing an innovative chessboard scanning strategy called tessellation algorithm, which can generate more uniform temperature distribution and diminish the layer warpage consequently especially throughout the layers with either geometry that is more complex or poses relatively longer dimensions. In the next step, this work develops a new technique in ABAQUS to verify the proposed scanning strategy. This technique simulates temperature distribution throughout a layer printed by chessboard printing patterns in powder-bed fusion process in a fraction of the time taken by current methods in the literature. This technique compares the temperature distribution throughout a designed layer printed by three presented chessboard-scanning patterns, namely, rastering pattern, helical pattern, and tessellation pattern. The results confirm that the tessellation pattern generates more uniform temperature distribution compared with the other two patterns. Further research is in progress to leverage the thermography methodology to verify the simulation technique. It is also pursuing a hybrid closed-loop online monitoring and control methodology, which bases on the introduced tessellation algorithm and online thermography in this work and Artificial Neural Networking (ANN) to generate the most possible uniform temperature distribution within a safe temperature range layer-by-layer.