<p>Among all additive manufacturing processes, material jetting, or inkjet 3D printing, builds the product similar to the traditional inkjet printing, either by drop-on-demand or continuous printing. Aside from the common advantages as other additive manufacturing methods, it can achieve higher resolution than other additive manufacturing methods. Combining its ability to accept a wide range of functional inks, inkjet 3D printing is predominantly used in pharmaceutical and biomedical applications. A height profile model is necessary to achieve better estimation of the geometry of a printed product. Numerical height profile models have been documented that can estimate the inkjet printing process from when the droplet hits the substrate till fully cured. Although they can estimate height profiles relatively accurately, these models generally take a long time to compute. A simplified model that can achieve sufficient accuracy while reducing computational complexity is needed for real-time process control. In this work, a layer-to-layer height propagation model that aims to balance computational complexity and model accuracy is proposed and experimentally validated. The model consists of two sub-models where one is dedicated to multi-layer line printing and the other is more broadly applicable for multi-layer 2D patterns. Both models predict the height profile of drops through separate volume and area layer-to-layer propagation. The layer-to-layer propagation is based on material flow and volume conservation. The models are experimentally validated on an experimental inkjet 3D printing system equipped with a heated piezoelectric dispenser head made by Microdrop. There are notable similarities between inkjet 3D printing and inkjet image printing, which has been studied extensively to improve color printing quality. Image processing techniques are necessary to convert nearly continuous levels of color intensities to binary printing map while satisfying the human visual system at the same time. It is reasonable to leverage such image processing techniques to improve the quality of inkjet 3D printed products, which might be more effective and efficient. A framework is proposed to adapt image processing techniques for inkjet 3D printing. Standard error diffusion method is chosen as a demonstration of the framework to be adapted for inkjet 3D printing and this adaption is experimentally validated. The adapted error diffusion method can improve the printing quality in terms of geometry integrity with low demand on computation power. Model predictive control has been widely used for process control in various industries. With a carefully designed cost function, model predictive control can be an effective tool to improve inkjet 3D printing. While many researchers utilized model predictive control to indirectly improves functional side of the printed products, geometry control is often overlooked. This is possibly due to the lack of high quality height profile models for inkjet 3D printing for real-time control. Height profile control of inkjet 3D printing can be formulated as a constrained non-linear model predictive control problem. The input to the printing system is always constrained, as droplet volume not only is bounded but also cannot be continuously adjusted due to the limitation of the printhead.  A specific cost function is proposed to account for the geometry of both the final printed product and the intermediate layers better. The cost function is further adjusted for the inkjet 3D printing system to reduce memory usage for larger print geometries by introducing sparse matrix and scaler cost weights. Two patterns with different parameter settings are simulated using model predictive controller. The simulated results show a consistent improvement over open-loop prints. Experimental validation is also performed on both a bi-level pattern and a P pattern, same as that printed with adapted error diffusion for inkjet 3D printing. The model predictive controlled printing outperforms the open-loop printing. In summary, a set of layer-to-layer height propagation profile models for inkjet 3D printing are proposed and experimentally validated. A framework to adapt error diffusion to improve inkjet 3D printing is proposed and validated experimentally. Model predictive control can also improve geometric integrity of inkjet 3D printing with a carefully designed cost function to address memory usage. It is also experimentally validated.</p>

Objective: The aim of this study is to describe additive manufacturing and evaluate how dentistry can take advantage of this technique today in general and for chair-side production of customized interim prostheses in particular. Method: Searches was made in the databases PubMed and ScienceDirect for information about additive manufacturing for dental applications. Searches was also made in the Rapid Prototyping Journal. Contacts was established with companies working with additive manufacturing for dental applications. The search engine Google was also used to find information about the additive manufacturing techniques in general and for dental applications. Results: Additive manufacturing is a rapidly expanding industry and can currently be used for several different applications in dentistry. It is today possible to use this technique, with materials approved for intraoral use, for chair-side fabrication of customized interim prostheses. Conclusion: Today it is possible to use additive manufacturing for chair-side production of interim prostheses. However, currently this production technique is still far too time consuming to be used effectively chair-side. With the current advancements in the area of additive manufacturing there is no doubt the technique can be utilized in the future and hopefully serve as a more reliable and safe way of producing interim prostheses. / Objective: The aim of this study is to describe additive manufacturing and evaluate how dentistry can take advantage of this technique today in general and for chair-side production of customized interim prostheses in particular. Method: Searches was made in the databases PubMed and ScienceDirect for information about additive manufacturing for dental applications. Searches was also made in the Rapid Prototyping Journal. Contacts was established with companies working with additive manufacturing for dental applications. The search engine Google was also used to find information about the additive manufacturing techniques in general and for dental applications. Results: Additive manufacturing is a rapidly expanding industry and can currently be used for several different applications in dentistry. It is today possible to use this technique, with materials approved for intraoral use, for chair-side fabrication of customized interim prostheses. Conclusion: Today it is possible to use additive manufacturing for chair-side production of interim prostheses. However, currently this production technique is still far too time consuming to be used effectively chair-side. With the current advancements in the area of additive manufacturing there is no doubt the technique can be utilized in the future and hopefully serve as a more reliable and safe way of producing interim prostheses.

To increase capacity, lower latency, and boostdata rates, new higher gain antennas that can transmitmillimeter-waves are needed. Dielectric lens antennas arean attractive potential solution. The J1-project investigatedthe permittivity and losses of four 3D printing filamentsin four frequency bands, to better design a hyperboliclens antenna in the Ka-band with a WR-28 StandardGain Horn Antenna acting as a feed. To measure thedielectric filaments, the TRL calibration method wasevaluated in simulation and employed in measurementstogether with the NRW method for permittivity extraction.Shortcomings of these methods near resonant frequencieswere marginally analyzed in simulation, and the results ofthe processed measured permittivities were shown to havesignificant uncertainty in the loss tangent. Nevertheless thedatasheet specified&lt;(r) =3 was shown to have meanrelative permittivity∗r= 3.53−0.13jin the Ka-band.Using the measurement data, a hyperbolic lens antennawas designed and optimized in simulation for the centerfrequency of the Ka-band at 33.25 GHz. The simulatedresults show an aperture efficiency of 36.2% and a gainof 30.4 dBi. / För att öka kapaciteten, sänka för- dröjningen samt höja datahastigheterna så behövs högre förstärkta antenner som kan transmittera millimetervågor. Här är dielektriska linsantenner en attraktiv, potentiell lösning. J1-projektet undersökte permittiviteten och förlusterna av fyra 3D-utskriftsfilament i fyra frekvensband, för att bättre designa en hyperbolisk linsantenn i Ka- bandet för en matande WR-28 “Standard Gain Horn Antenna”. För att kunna mäta de dielektriska filamenten så var TRL-kalibreringsmetoden utvärderad i simulering och nyttjad vid mätning tillsammans med NRW-metoden för att betsämma permittiviteten. Nackdelarna bakom dessa metoder nära resonanta frekvenser var marginellt analyserade i simulering och resultaten av de behandlade, mätta permittiviteterna visade sig ha märkbara osäker- heter i deras förlusttangens. Oavsett så blev medelvärdet på det uppmätta resultatet; av det databladsspecificerade materialet R (∈r) = 3; ∈*r = 3,53 -0,13j i Ka-bandet. Med hjälp av databladsspecifikationerna, så designades samt optimiserades en hyperbolisk linsantenn i simulering för Ka-bandets mittfrekvens på 33,25 GHz. De simulerade resultaten visar på en apertureffektivitet på 36,2% och en förstärkning på 30,4 dBi. / Kandidatexjobb i elektroteknik 2020, KTH, Stockholm

This project draws upon material culture, digital humanities, and archival theory and method in the service of public history investigations. After selecting an artifact and performing object analysis, I will digitize the artifact and materialize a new object. I will then perform another object analysis on the 3D printed object. This exercise will provide the familiar benefits of object analysis, but the decisions and interactions necessary to digitize and materialize the object provide a fresh perspective. I will propose approaches for performing similar investigations in repositories, along with a pedagogical argument for doing so. By emphasizing modularity, flexibility, and minimal capital requirements, I hope these approaches can be adapted to a variety of institutions and audiences. Researchers will reap the benefits of intellectual and emotional engagement, hands-on learning, and technological experimentation. Public historians will have the opportunity to engage in outreach and innovative education and exploration of their collections. / History

<p> Ink-jet printing onto flat paper is a widely established process. In this thesis, we make extensions to printing on target surfaces such as metals and glass, using a 5-axis orientable head. Original artwork is created using CAD, and is sampled to create the ink jet point cloud. The target surface location is registered using a standard Coordinate Measuring Machine (CMM) 5-axis touch trigger probe. The probe is then replaced with the ink jet head and the printing process is carried out. Demonstration of the system is illustrated using flat metal and glass samples, as well as rapid prototyped 3-D plastic shapes.</p> / Thesis / Master of Applied Science (MASc)

Fused deposition modeling (FDM) is gaining an ever increasing attention for its ability to fabricate complex geometry parts and prototypes at lower cost. The technology is striving to produce parts with high mechanical resistance that can withstand and perform under high stress environment. The adhesion strength between layers, transverse strength, is a limiting factor that need to be quantitatively evaluated to further understand and improve the bonding behavior of thermoplastic polymer in FDM. This interfacial adhesion is derived by the diffusion and penetration of polymer chains across the interface allowing the chain entanglement to form a bonding medium. This study investigates the bonding behaviour of polylactic acid (PLA) as a function of chain branching. The adhesion strength is quantitatively evaluated by developing and performing a peel test of a two-printed layer samples. It is possible to increase chain branching of PLA by bulk modification with epoxy chain extender. The modification of PLA was carried out using an internal batch mixer with four different concentrations of chain extender. The modified PLA was processed into print filament and characterized by parallel plate rheometry and DSC. It was found that the addition of chain extender increased molecular weight and degree of branching of PLA and in return the peel testing results reflected a significant increase in adhesion strength. Such improvement can be attributed to the long branched chains of PLA and its ability to create entanglements between layers. These findings can help in producing better PLA filaments to provide a higher stress resistance for FDM fabricated functional parts. / Thesis / Master of Applied Science (MASc) / Fused Deposition Modeling (FDM) is a recent popular method of plastic 3D printing technique, in which plastic filament is heated to a molten state to be then deposited through a layer-by-layer fashion to successfully fabricate parts. One of the drawbacks of that technology is the low bonding strength developed between layers as compared to strength along the length direction of layers. This study focuses on developing a testing methodology to evaluate the adhesion strength between layers and altering the material structure to maximize such strength. Four types of polylactic acid with different degrees of chain branching were successfully processed, printed and tested. Material with higher degree of branching yielded higher adhesion strength.

One of the major technical challenges with creating 3D artificial tissue constructs is the lack of simple and effective methods to integrate vascular networks within them. Without these vascular-like networks, the cells embedded within the constructs quickly become necrotic. This thesis details the use of a commercially available, low-cost, 3D printer modified with a microfluidic printhead in order to generate instantly perfusable vascular-like networks integrated within gel scaffolds seeded with cells. The printhead featured a coaxial nozzle that allowed the fabrication of hollow, gel tubes (500µm–2mm) that can be easily patterned to create single or multi-layered constructs. Media perfusion of the channels caused a significant increase in cell viability. This microfluidic nozzle design was further modified to allow for multi-axial extrusion in order to 3D print and pattern bi- and tri-layered hollow channel structures. Most available methodologies lack the ability to create multi-layered concentric conduits inside natural extracellular matrices, which would more accurately replicate the hierarchal architecture of biological blood vessels. The nozzle used in this work allowed, for the first time, for these hierarchal structures to be embedded within layers of gels in a fast, simple and low cost manner. This scalable design allowed for versatility in material incorporation, thereby creating heterogeneous structures that contained distinct concentric layers of different cell types and biomaterials. This thesis also demonstrates the use of non-extrusion based 3D biofabrication involving planar processing by means of hydrogel adhesion. There remains a lack of effective adhesives capable of composite layer fusion without affecting the integrity of patterned features. Here, silicon carbide was found for the first time to be an effective and cytocompatible adhesive to achieve strong bonding (0.39±0.03kPa) between hybrid hydrogel films. Multi-layered, heterogeneous constructs with embedded high-resolution microchannels (150µm-1mm) were fabricated in this way. With the new 3D fabrication technology developed in this thesis, gel constructs with embedded arrays of hollow channels can be created and used as potential substitutes for blood vessel networks as well as in applications such as drug discovery models and biological studies. / Thesis / Doctor of Philosophy (PhD) / Additive manufacturing (AM) involves any three-dimensional (3D) fabrication technologies that is used to produce a solid model of a predetermined design. AM techniques have recently been used in tissue engineering applications for fabrication of 3D artificial tissues that resemble architectures and material properties similar to that of the native tissue. Utilizing AM for this purpose presents the advantage of increased control in feature patterning, which leads to the realization of more complex geometries. However, there still remains a lack of simple and effective methods to integrate vascular networks within these 3D artificially engineered scaffolds and tissue constructs. Without these vascular-like networks, the cells embedded within the constructs would quickly die due to a lack of nutrient delivery and waste transport. This remains one of the biggest challenges in true 3D tissue engineering. This thesis presents a number of fast, effective and low-cost AM biofabrication techniques to address this challenge.

Silicones are industrially important polymers characterized by a wide spectrum of chemical and physical properties with a number of important applications including automotive components, construction materials, isolating parts in electronic devices, flexible electronics, and medical products. Development of additive manufacturing methods for silicones enable production of complex and custom designed shapes and structures at both the micro- and macro-scale, economically feasible. In general, such materials can be fabricated using stereolithographic, extrusion-based, or inkjet printing techniques, in which silicones are polymerized using either photo- or heat-initiators. Silicones can also be crosslinked based on chemical reactions. Although this approach is supposedly the simplest, it has not been widely applied in additive manufacturing, as suitable technology for mixing and curing reactive inks without clogging nozzles has not be developed yet. To address this issue, a new 3D printer, that enables the fabrication of highly reactive and low viscous materials, has been developed and tested experimentally. The proposed fabrication method involves the ejection of two reactive droplets simultaneously from individual dispensers, merging and mixing them in free space outside the nozzle followed by deposition of the merged drop in a patterned format on a substrate. It was shown that the printing process is robust and stable more than 4 hours and it can be used on demand. By incorporating an XYZ positioner, it was possible to deposit droplets in an overlapping fashion to print any programmable shape featuring homogeneous structure, with a small number of pores. Moreover, due to the almost instantaneous reaction between two components (< 10s), the fabrication of very high aspect ratio (AR > 50) objects is possible. Lastly, the presented method can be easily adapted to print in free space without the use of support materials. / Thesis / Master of Applied Science (MASc)

No description available.

This thesis seeks to establish whether recycled E-waste rABS from Stena Recycling AB in Halmstad, Sweden, can be effectively utilized in additive manufacturing processes and if it can be applied similarly to virgin ABS. Results show that it is possible to apply the rABS granules on 3D-printing but with mechanical property losses and cosmetic losses. The result shows a loss in tensile strength between rABS and virgin ABS.The difference of the best performing rABS versus the best performing virgin ABS results in a mean loss of 32% and best performing loss of 25%. The research is confined to filament extrusion and experiments were conducted in FabLab Halmstad utilizing 3Devo Composer with 15 different temperature settings. The filament was then used in Prusa MK4 where three tensile tests in 0, 45 and 90 degrees with 5 iterations per test and per setting. The 3D-printed recycled tensile tests results are compared to tensile tests made from virgin ABS. The conclusion is that there are significant mechanical property losses  and with poor printability compared to store bought ABS filament.