Additive manufacturing: studio delle non conformità geometriche e dimensionali in componenti realizzati mediante tecnica fused deposition modelling

La fabbricazione additiva è una classe di metodi di fabbricazione in cui il componente viene costruito aggiungendo strati di materiale l’uno sull’altro, sino alla completa realizzazione dello stesso. Si tratta di un principio di fabbricazione sostanzialmente differente da quelli tradizionali attualmente utilizzati, che si avvalgono di utensili per sottrarre materiale da un semilavorato, sino a conferire all’oggetto la forma desiderata, mentre i processi additivi non richiedono l’utilizzo di utensili. Il termine più comunemente utilizzato per la fabbricazione additiva è prototipazione rapida. Il termine “prototipazione”’ viene utilizzato in quanto i processi additivi sono stati utilizzati inizialmente solo per la produzione di prototipi, tuttavia con l’evoluzione delle tecnologie additive questi processi sono sempre più in grado di realizzare componenti di elevata complessità risultando competitivi anche per volumi di produzione medio-alti. Il termine “rapida” viene invece utilizzato in quanto i processi additivi vengono eseguiti molto più velocemente rispetto ai processi di produzione convenzionali. La fabbricazione additiva offre diversi vantaggi dal punto di vista di: • velocità: questi processi “rapidi” hanno brevi tempi di fabbricazione. • realizzazione di parti complesse: con i processi additivi, la complessità del componente ha uno scarso effetto sui tempi di costruzione, contrariamente a quanto avviene nei processi tradizionali dove la realizzazione di parti complesse può richiedere anche settimane. • materiali: la fabbricazione additiva è caratterizzata dalla vasta gamma di materiali che può utilizzare per la costruzione di pezzi. Inoltre, in alcuni processi si possono costruire pezzi le cui parti sono di materiali diversi. • produzioni a basso volume: molti processi tradizionali non sono convenienti per le produzioni a basso volume a causa degli alti costi iniziali dovuti alla lavorazione con utensili e tempi di setup lunghi.

Additive manufacturing of tissues and organs

Additive manufacturing techniques offer the potential to fabricate organized tissue constructs to repair or replace damaged or diseased human tissues and organs. Using these techniques, spatial variations of cells along multiple axes with high geometric complexity in combination with different biomaterials can be generated. The level of control offered by these computer-controlled technologies to design and fabricate tissues will accelerate our understanding of the governing factors of tissue formation and function. Moreover, it will provide a valuable tool to study the effect of anatomy on graft performance. In this review, we discuss the rationale for engineering tissues and organs by combining computer-aided design with additive manufacturing technologies that encompass the simultaneous deposition of cells and materials. Current strategies are presented, particularly with respect to limitations due to the lack of suitable polymers, and requirements to move the current concepts to practical application.

Electrospinning and additive manufacturing : converging technologies

A well-engineered scaffold for regenerative medicine, which is suitable to be translated from the bench to the bedside, combines inspired design, technical innovation and precise craftsmanship. Electrospinning and additive manufacturing are separate approaches to manufacturing scaffolds for a variety of tissue engineering applications. A need to accurately control the spatial distribution of pores within scaffolds has recently resulted in combining the two processing methods, to overcome shortfalls in each technology. This review describes where electrospinning and additive manufacturing are used together to generate new porous structures for biological applications.

In vitro and in vivo assessment of bioactive composite scaffolds fabricated via additive manufacturing technology

Additive manufacturing (AM) technology was implemented together with new composite material comprising a synthetic materials, namely, polycaprolactone and bioactive glass with the ultimate aim of the production of an off-the-shelf composite bone scaffold product with superior bone regeneration capacity in a cost effective manner. Our studies indicated that the composite scaffolds have huge potential in promoting bone regeneration. It is our contention that owing to the fruits of such innovative efforts, the field of bone regeneration can metamorphose into a technology platform that allows clinicians worldwide to create tissue-engineered bone with economies of scale in the years to come.

Biofabrication of customized bone grafts by combination of additive manufacturing and bioreactor knowhow

This study reports on an original concept of additive manufacturing for the fabrication of tissue engineered constructs (TEC), offering the possibility of concomitantly manufacturing a customized scaffold and a bioreactor chamber to any size and shape. As a proof of concept towards the development of anatomically relevant TECs, this concept was utilized for the design and fabrication of a highly porous sheep tibia scaffold around which a bioreactor chamber of similar shape was simultaneously built. The morphology of the bioreactor/scaffold device was investigated by micro-computed tomography and scanning electron microscopy confirming the porous architecture of the sheep tibiae as opposed to the non-porous nature of the bioreactor chamber. Additionally, this study demonstrates that both the shape, as well as the inner architecture of the device can significantly impact the perfusion of fluid within the scaffold architecture. Indeed, fluid flow modelling revealed that this was of significant importance for controlling the nutrition flow pattern within the scaffold and the bioreactor chamber, avoiding the formation of stagnant flow regions detrimental for in vitro tissue development. The bioreactor/scaffold device was dynamically seeded with human primary osteoblasts and cultured under bi-directional perfusion for two and six weeks. Primary human osteoblasts were observed homogenously distributed throughout the scaffold, and were viable for the six week culture period. This work demonstrates a novel application for additive manufacturing in the development of scaffolds and bioreactors. Given the intrinsic flexibility of the additive manufacturing technology platform developed, more complex culture systems can be fabricated which would contribute to the advances in customized and patient-specific tissue engineering strategies for a wide range of applications.

The foundations of a new approach to additive manufacturing: Characteristics of free space metal deposition

In this paper, we report on the realisation of a free space deposition process (FSD). For the first time the use of a moving support structure to deposit tracks of metal starting from a substrate and extending into free space is characterised. The ability to write metal shapes in free space has wide ranging applications in additive manufacturing and rapid prototyping where the tracks can be layered to build overhanging features without the use of fixed support structures (such as is used in selective laser melting (SLM) and stereo lithography (SLA)). We demonstrate and perform a preliminary characterisation of the process in which a soldering iron was used to deposit lead free solder tracks. The factors affecting the stability of tracks and the effect of operating parameters, temperature, velocity, initial track starting diameter and starting volume were measured. A series of 10 tracks at each setting were compared with a control group of tracks; the track width, taper and variation between tracks were compared. Notable results in free space track deposition were that the initial track diameter and volume affected the repeatability and quality of tracks. The standard deviation of mean track width of tracks from the constrained initial diameter group were half that of the unconstrained group. The amount of material fed to the soldering iron before commencing deposition affected the taper of tracks. At an initial volume of 7 mm3 and an initial track diameter of 0.8 mm, none of the ten tracks deposited broke or showed taper > ∼1°. The maximum deposition velocity for free space track deposition using lead-free solder was limited to 1.5 mm s-1. © 2011 Elsevier B.V. All rights reserved.

Prototipazione rapida di interesse biomedico mediante stampa 3d / manifattura additiva

Descrizione delle caratteristiche della manifattura additiva e delle principali tecniche di stampa 3d. Esempio di impiego di questa tecnica in ambito biomedico per la fabbricazione di prototipi di dispositivi pronti all'uso utilizzabili per test e studi ulteriori.

Studio e sviluppo di una protesi cinematica per amputazioni parziali di mano mediante prototipazione rapida

Questo elaborato descrive il lavoro svolto nell'Area ricerca e formazione del Centro Protesi INAIL volto all'integrazione della tecnologia di stampa 3D con i processi produttivi dell'azienda stessa al fine di ottenere una protesi cinematica e funzionale per pazienti con amputazioni parziali di mano (a livello metacarpale e transmetacarpale) che risulti economica e in grado di restituire la funzionalità di grasping della mano.

Ansätze zum Management der Additive Manufacturing Supply Chain

Da sich Additive Manufacturing (AM) von traditionellen Produktionsverfahren unterscheidet, entstehen neue Möglichkeiten im Produktdesign und im Supply Chain Setup. Die Auswirkungen der Aufhebung traditionellen Restriktionen im Produktdesign werden unter dem Begriff „Design for Additive Manufacturing“ intensiv diskutiert. In gleicher Weise werden durch AM Restriktionen im traditionellen Supply Chain Setup aufgehoben. Insbesondere sind die folgenden Verbesserungen möglich: Reduktion von Losgrössen und Lieferzeiten, bedarfsgerechte Produktion auf Abruf, dezentrale Produktion, Customization auf Ebene Bauteil und kontinuierliche Weiterentwicklung von Bauteilen. Viele Firmen investieren nicht selbst in die AM Technologien, sondern kaufen Bauteile bei Lieferanten. Um das Potential der AM Supply Chain mit Lieferanten umzusetzen, entstehen die folgenden Anforderungen an AM Einkaufsprozesse. Erstens muss der Aufwand pro Bestellung reduziert werden. Zweitens brauchen AM Nutzer einen direkten Zugang zu den Lieferanten ohne Umweg über die Einkaufsabteilung. Drittens müssen geeignete AM Lieferanten einfach identifiziert werden können. Viertens muss der Wechsel von Lieferanten mit möglichst geringem Aufwand möglich sein. Ein mögliche Lösung sind AM spezifische E-Procurement System um diese Anforderungen zu erfüllen

Rapid prototyping of multi-scale biomedical microdevices by combining additive manufacturing technologies

The possibility of designing and manufacturing biomedical microdevices with multiple length-scale geometries can help to promote special interactions both with their environment and with surrounding biological systems. These interactions aim to enhance biocompatibility and overall performance by using biomimetic approaches. In this paper, we present a design and manufacturing procedure for obtaining multi-scale biomedical microsystems based on the combination of two additive manufacturing processes: a conventional laser writer to manufacture the overall device structure, and a direct-laser writer based on two-photon polymerization to yield finer details. The process excels for its versatility, accuracy and manufacturing speed and allows for the manufacture of microsystems and implants with overall sizes up to several millimeters and with details down to sub-micrometric structures. As an application example we have focused on manufacturing a biomedical microsystem to analyze the impact of microtextured surfaces on cell motility. This process yielded a relevant increase in precision and manufacturing speed when compared with more conventional rapid prototyping procedures.

Ku band waveguide diplexer design for satellite communication. Implementation by additive manufacturing and experimental characterization

Gran cantidad de servicios de telecomunicación tales como la distribución de televisión o los sistemas de navegación están basados en comunicaciones por satélite. Del mismo modo que ocurre en otras aplicaciones espaciales, existe una serie de recursos clave severamente limitados, tales como la masa o el volumen. En este sentido, uno de los dispositivos pasivos más importantes es el diplexor del sistema de alimentación de la antena. Este dispositivo permite el uso de una única antena tanto para transmitir como para recibir, con la consiguiente optimización de recursos que eso supone. El objetivo principal de este trabajo es diseñar un diplexor que cumpla especificaciones reales de comunicaciones por satélite. El dispositivo consiste en dos estructuras filtrantes unidas por una bifurcación de tres puertas. Además, es imprescindible utilizar tecnología de guía de onda para su implementación debido a los altos niveles de potencia manejados. El diseño del diplexor se lleva a cabo dividiendo la estructura en diversas partes, con el objetivo de que todo el proceso sea factible y eficiente. En primer lugar, se han desarrollado filtros con diferentes respuestas – paso alto, paso bajo y paso banda – aunque únicamente dos de ellos formarán el diplexor. Al afrontar su diseño inicial, se lleva a cabo un proceso de síntesis teórica utilizando modelos circuitales. A continuación, los filtros se optimizan con técnicas de diseño asistido por ordenador (CAD) full-wave, en concreto mode matching. En este punto es esencial analizar las estructuras y su simetría para determinar qué modos electromagnéticos se están propagando realmente por los dispositivos, para así reducir el esfuerzo computacional asociado. Por último, se utiliza el Método de los Elementos Finitos (FEM) para verificar los resultados previamente obtenidos. Una vez que el diseño de los filtros está terminado, se calculan las dimensiones correspondientes a la bifurcación. Finalmente, el diplexor al completo se somete a un proceso de optimización para cumplir las especificaciones eléctricas requeridas. Además, este trabajo presenta un novedoso valor añadido: la implementación física y la caracterización experimental tanto del diplexor como de los filtros por separado. Esta posibilidad, impracticable hasta ahora debido a su elevado coste, se deriva del desarrollo de las técnicas de manufacturación aditiva. Los prototipos se imprimen en plástico (PLA) utilizando una impresora 3D de bajo coste y posteriormente se metalizan. El uso de esta tecnología conlleva dos limitaciones: la precisión de las dimensiones geométricas (±0.2 mm) y la conductividad de la pintura metálica que recubre las paredes internas de las guías de onda. En este trabajo se incluye una comparación entre los valores medidos y simulados, así como un análisis de los resultados experimentales. En resumen, este trabajo presenta un proceso real de ingeniería: el problema de diseñar un dispositivo que satisfaga especificaciones reales, las limitaciones causadas por el proceso de fabricación, la posterior caracterización experimental y la obtención de conclusiones.