Since many years Additive Manufacturing (AM) is seen with flourishing enthusiasm due to the shift of paradigm over traditional production processes, providing new manufacturing technologies such as Laser Metal Deposition (LMD). This additive manufacturing process is able to produce large dimensions and highly customized parts layer by layer with high flexibility, starting from a Computer Aided Design (CAD) file, reducing the costs. Nonetheless, high efficiency process is required in order not to invalidate the huge advantages that this technology could offer in terms of material saving. Nowadays different formulations for process efficiency can be found in literature, but the definitions proposed are static and untied with the deposition development, completely neglecting a possible change throughout the process, leaving a blank space in the characterization of the phenomenon. This work has the innovative purpose of studying the efficiency of LMD technology in detail, its evolution throughout the process and any possible change of it. The comprehension of the phenomena occurring is fundamental as it is the identification of the process parameters that compete in the determination of the efficiency, in order to understand which elements can contribute to its optimization. A compressive model, including the main process parameters, was developed to describe the efficiency during the deposition. With such a model the efficiency can be defined as a function of the layer height. Accordingly, the efficiency estimation was possible thanks to the layer height measurement in real time by means of a custom coaxial triangulation system, which allows to avoid the usage of intrusive monitoring devices. To validate the model and to monitor the efficiency, a dedicated measuring system was designed and built. This prototype, created ex novo based on a new idea, is capable of collecting data of the deposition weight in real time and observe the evolution of the process. The results obtained during the different steps of the work were compared to each other, to the process parameters and to traditional methods to measure the efficiency. This revealed the correct functioning of the measurement system created ad hoc, highlighted a certain dependency with the process parameters, enshrining the accuracy of the model and defining validity limits for it. The peculiar efficiency behavior shown has been deeply studied and analyzed in order to promote and encourage future developments in this field.
Da diversi anni l’Additive Manufacturing (AM) è visto con crescente entusiasmo a causa del cambio di paradigma rispetto ai tradizionali processi di produzione, fornendo nuove tecnologie come il Laser Metal Deposition (LMD). Questo processo di produzione è in grado di realizzare forme complesse di grandi dimensioni e componenti altamente personalizzati, con grande flessibilità, strato dopo strato, partendo da un file CAD (Computer Aided Design), riducendo i costi. Tuttavia, un processo ad alta efficienza è richiesto per non inficiare i grandi vantaggi che questa tecnologia può offrire in termini di risparmio di materiale. Attualmente è possibile trovare in letteratura diverse formulazione per l’efficienza di questo processo, ma le definizioni proposte sono statiche e slegate dallo sviluppo della deposizione, trascurando completamente ogni possibile cambiamento durante il processo, lasciando un vuoto nella caratterizzazione del fenomeno. Questo lavoro ha come obiettivo l’innovativo studio nel dettaglio dell’efficienza del processo di LMD, la sua evoluzione ed ogni suo possibile cambiamento. La comprensione dei fenomeni che avvengono è fondamentale, cosi come l’identificazione dei parametri che concorrono alla determinazione dell’efficienza, al fine di capire quali elementi contribuiscono alla sua ottimizzazione. Un modello completo, comprensivo dei principali parametri di processo è stato sviluppato per descrivere l’efficienza durante la deposizione. Con questo modello, l’efficienza può essere definita in funzione dell’altezza dei layers. Pertanto, la stima dell’efficienza è stata resa possibile dalla misura in tempo reale dell’altezza dei layers, attraverso un sistema di triangolazione coassiale personalizzato, che permette di evitare l’uso di intrusivi sistemi di monitoraggio. Per validare il modello e monitorare l’efficienza, è stato costruito un sistema di misura dedicato. Questo prototipo, creato ex novo basandosi su una nuova idea, è capace di raccogliere i dati del peso di deposizione in tempo reale ed osservare l’evoluzione del processo. I risultati ottenuti durante le diverse fasi del lavoro sono stati confrontati tra di loro, con i parametri e con i metodi tradizionali di misurare l’efficienza. Questo ha rivelato il corretto funzionamento del sistema di misura creato ad hoc ed evidenziato una certa dipendenza con i parametri di processo, sancendo la correttezza del modello e definendone i limiti di validità. Il peculiare comportamento mostrato dall’efficienza è stato studiato e analizzato approfonditamente al fine di promuovere e incoraggiare sviluppi futuri in questo settore.
Laser metal deposition : modeling and monitoring of process efficiency
CACCIA, RICCARDO
2018/2019
Abstract
Since many years Additive Manufacturing (AM) is seen with flourishing enthusiasm due to the shift of paradigm over traditional production processes, providing new manufacturing technologies such as Laser Metal Deposition (LMD). This additive manufacturing process is able to produce large dimensions and highly customized parts layer by layer with high flexibility, starting from a Computer Aided Design (CAD) file, reducing the costs. Nonetheless, high efficiency process is required in order not to invalidate the huge advantages that this technology could offer in terms of material saving. Nowadays different formulations for process efficiency can be found in literature, but the definitions proposed are static and untied with the deposition development, completely neglecting a possible change throughout the process, leaving a blank space in the characterization of the phenomenon. This work has the innovative purpose of studying the efficiency of LMD technology in detail, its evolution throughout the process and any possible change of it. The comprehension of the phenomena occurring is fundamental as it is the identification of the process parameters that compete in the determination of the efficiency, in order to understand which elements can contribute to its optimization. A compressive model, including the main process parameters, was developed to describe the efficiency during the deposition. With such a model the efficiency can be defined as a function of the layer height. Accordingly, the efficiency estimation was possible thanks to the layer height measurement in real time by means of a custom coaxial triangulation system, which allows to avoid the usage of intrusive monitoring devices. To validate the model and to monitor the efficiency, a dedicated measuring system was designed and built. This prototype, created ex novo based on a new idea, is capable of collecting data of the deposition weight in real time and observe the evolution of the process. The results obtained during the different steps of the work were compared to each other, to the process parameters and to traditional methods to measure the efficiency. This revealed the correct functioning of the measurement system created ad hoc, highlighted a certain dependency with the process parameters, enshrining the accuracy of the model and defining validity limits for it. The peculiar efficiency behavior shown has been deeply studied and analyzed in order to promote and encourage future developments in this field.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/151474