Prediction of laser drilled hole geometries from linear cutting operation by way of artificial neural networks

AbstractThis paper deals on artificial intelligence (AI) application for the estimation of kerf geometry and hole diameters for laser micro-cutting and laser micro-drilling operations. To this aim laser cutting and laser drilling operation were performed on NIMONIC 263 superalloy sheet, 0.38 mm in nominal thickness, by way of a 100 W fibre laser in modulated wave regime. Linear cuts and holes (by trepanning) were performed fixing the average power at 80 W and changing the pulse duration, the cutting speed, the focus depth and the laser path (the latter only for the drilling operations). Kerf width and the holed diameter, at the upper and downsides, were measured by digital microscopy. Different artificial neural networks (ANNs) were developed and tested to predict the kerf widths and the diameters (at the upper and downside). Two ANNs were addressed to the linear cutting process modelling; also, two further ANNs were developed for micro-drilling on the base of the linear cutting process features. The networks were trained with a subset of data containing the process conditions and the kerf/hole geometry. The ANN test was performed with the remaining data. The results show that ANNs can model the cut and hole geometry as a function of the process parameters. Moreover, the ANN trained with kerf geometry is more efficient. Therefore, a functional correlation between the kerf geometries achievable in the linear cutting process and micro-drilling was assessed

Laser Texturing to Increase the Wear Resistance of an Electrophoretic Graphene Coating on Copper Substrates

In the present paper, different surface preparations are investigated with the aim of increasing the wear behaviour of an electrophoretic graphene coating on a copper plate. The study was divided into two steps: In the first step (pre-tests), to detect the most promising pretreatment technology, five different surface preparations were investigated (electropolishing, sandblasting, degreasing and pickling, laser cleaning and laser dots).In the second step, on the basis of the results of the first step, a 3(2) full factorial plan was developed and tested; three treatment types (pickled and degreased, laser-cleaned, and laser dots) and three different voltages (30, 45 and 60 V) were adopted. Analysis of variance (ANOVA) was used to evaluate their influence on wear resistance; in particular, the maximum depth and width of the wear tracks and the coating break distance were investigated. The results of this study show that, in optimal conditions, laser treatment (particularly laser dots) canlead to as high as a four-fold increase in wear resistance

optimization of the sandblasting process for a better electrodeposition of copper thin films on aluminum substrate by feedforward neural network

Abstract The influence of a proper surface preparation is essential for a better adhesion of copper thin films on aluminum substrate. In this work, the surface properties of the aluminum substrate have been modified through sandblasting process, in order to influence the quality of electroplating. To evaluate the correct adhesion of the thin film to the substrate non-destructive measurements of diffusivity by infrared thermography have been made. A combining of a feedforward artificial neural network (FFANN) and an external optimized algorithm (EOA) is proposed to optimize the substrate surface preparation process. A FFANN model is developed to map the complex non-linear relationship between the surface process conditions of the substrate and the thermal diffusivity of the electroplated sample. A good performance of the FFANN model is achieved. An EOA is used for the optimization of the sandblasting process conditions, in order to maximize the adhesion of the thin film to the substrate

Prediction of Poly-methyl-methacrylate Laser Milling Process Characteristics Based on Neural Networks and Fuzzy Data☆

Abstract Laser milling is a recent technology adopted in rapid prototyping to produce tool, mould and polymer-based microfluidic devices. In this process, a laser beam is used to machine a solid bulk, filling the area to be machined with a number of closely spaced parallel lines. Compared to traditional machining, this method has some advantages, such as: greater flexibility of use, no mechanical contact with the surface, a reduction in industrial effluents, a fine accuracy of machining, even with complex forms, and the possibility to work different kind of materials. While it is relatively easy to predict the depth of the area worked, the surface roughness is more difficult to predict due to the materials behaviors at microscopic level. This is truer when polymer processing is considered due to the local thermal effects. The paper addresses the application of an artificial neural network computing technique to predict the depth and the surface roughness in laser milling tests of poly-methyl-methacrylate. The tests were carried out adopting a CO 2 laser working in continuous and pulsed wave mode. The obtained results showed a good agreement between the model and the experimental data. As a matter of fact, despite the thermal degradation that occurs on the PMMA surface, neural network processing offers an effective method for the prevision of roughness parameters as a function of the adopted process parameters

Experimental Study on Fiber Laser Microcutting of Nimonic 263 Superalloy

Abstract Laser cutting of NIMONIC 263 sheet was investigated by using a 100 W Yb:YAG fiber laser. The study was divided in two phases. In the first one, the critical cutting speeds were found fixing the average power (80 W), changing the pulse duration, the cutting speed, the nozzle diameter and the focus position. Then, a full factorial design was adopted according to the DoE methodology. In order to determine which of the process parameters affect the kerf geometry and how, Analysis Of Variance (ANOVA) was used. Experimental results show the possibility to obtain kerf characterized by narrow width and low taper angle values

Bowel preparation for elective colorectal resection: multi-treatment machine learning analysis on 6241 cases from a prospective Italian cohort

background current evidence concerning bowel preparation before elective colorectal surgery is still controversial. this study aimed to compare the incidence of anastomotic leakage (AL), surgical site infections (SSIs), and overall morbidity (any adverse event, OM) after elective colorectal surgery using four different types of bowel preparation. methods a prospective database gathered among 78 Italian surgical centers in two prospective studies, including 6241 patients who underwent elective colorectal resection with anastomosis for malignant or benign disease, was re-analyzed through a multi-treatment machine-learning model considering no bowel preparation (NBP; No. = 3742; 60.0%) as the reference treatment arm, compared to oral antibiotics alone (oA; No. = 406; 6.5%), mechanical bowel preparation alone (MBP; No. = 1486; 23.8%), or in combination with oAB (MoABP; No. = 607; 9.7%). twenty covariates related to biometric data, surgical procedures, perioperative management, and hospital/center data potentially affecting outcomes were included and balanced into the model. the primary endpoints were AL, SSIs, and OM. all the results were reported as odds ratio (OR) with 95% confidence intervals (95% CI). results compared to NBP, MBP showed significantly higher AL risk (OR 1.82; 95% CI 1.23-2.71; p = .003) and OM risk (OR 1.38; 95% CI 1.10-1.72; p = .005), no significant differences for all the endpoints were recorded in the oA group, whereas MoABP showed a significantly reduced SSI risk (OR 0.45; 95% CI 0.25-0.79; p = .008). conclusions MoABP significantly reduced the SSI risk after elective colorectal surgery, therefore representing a valid alternative to NBP

Abdominal drainage after elective colorectal surgery: propensity score-matched retrospective analysis of an Italian cohort

background: In italy, surgeons continue to drain the abdominal cavity in more than 50 per cent of patients after colorectal resection. the aim of this study was to evaluate the impact of abdominal drain placement on early adverse events in patients undergoing elective colorectal surgery. methods: a database was retrospectively analysed through a 1:1 propensity score-matching model including 21 covariates. the primary endpoint was the postoperative duration of stay, and the secondary endpoints were surgical site infections, infectious morbidity rate defined as surgical site infections plus pulmonary infections plus urinary infections, anastomotic leakage, overall morbidity rate, major morbidity rate, reoperation and mortality rates. the results of multiple logistic regression analyses were presented as odds ratios (OR) and 95 per cent c.i. results: a total of 6157 patients were analysed to produce two well-balanced groups of 1802 patients: group (A), no abdominal drain(s) and group (B), abdominal drain(s). group a versus group B showed a significantly lower risk of postoperative duration of stay >6 days (OR 0.60; 95 per cent c.i. 0.51-0.70; P < 0.001). a mean postoperative duration of stay difference of 0.86 days was detected between groups. no difference was recorded between the two groups for all the other endpoints. conclusion: this study confirms that placement of abdominal drain(s) after elective colorectal surgery is associated with a non-clinically significant longer (0.86 days) postoperative duration of stay but has no impact on any other secondary outcomes, confirming that abdominal drains should not be used routinely in colorectal surgery

Modelli per l’ottimizzazione dei processi industriali: incisioni laser

La recente introduzione sul mercato (2001-2002) di nuovi tipi di laser da marcatura (Nd:YAG con impulsi dell’ordine dei nanosecondi), con costi relativamente contenuti ha permesso una notevole diffusione di questi sistemi in ambito industriale. Questi sistemi, grazie alle loro peculiarità, costituiscono attualmente una reale ed efficace alternativa ai tradizionali metodi di marcatura (incisione, elettroerosione, verniciatura, ecc.). Ciò nonostante, la bibliografia scientifica e quella tecnica appaiono abbastanza carenti sia nella descrizione dei sistemi che nella creazione di modelli atti a descrivere i loro effetti sui materiali lavorati. Nel presente lavoro si è quindi inteso realizzare una sperimentazione per caratterizzare la marcatura prodotta da un laser Nd:YAG di nuovissima generazione (2004). Tale sistema è costituito da un laser pompato in continuo e funzionante in regime di impulsi giganti (Q-switch), le cui caratteristiche principali sono: lunghezza d’onda = 1,064 μm; max potenza media = 20 W; durata del singolo impulso = 150 ns e fattore di qualità del fascio M2 > 1 Il lavoro svolto affronta l’influenza dei parametri di lavorazione sulle caratteristiche geometriche del solco e si propone di costruire un modello analitico che permetta di scegliere i parametri di lavorazione in dei risultati desiderati. Sono state effettuate varie prove su due acciai inossidabili (AISI 304 e AISI430), variando opportunamente i parametri impostabili dal software proprietario della macchina. Successivamente si sono analizzate le principali caratteristiche della geometria dell’impronta, ovvero profondità e larghezza. I parametri analizzati sono: la frequenza di ripetizione degli impulsi, la velocità di marcatura e la corrente di alimentazione dei diodi; per ogni terna di questi parametri si ha a disposizione una determinata potenza media, a cui corrispondono precisi valori in termini di potenza di picco e/o energia ceduta dal singolo impulso. Pur essendo il termine energetico sicuramente il fattore che domina il processo e quindi la geometria finale della marcatura, da un punto di vista pratico si è focalizzata l’attenzione sui parametri menzionati (frequenza, velocità e corrente) in quanto sono quelli che vengono richiesti dal software primo della lavorazione. Abbiamo analizzato, fra i diversi presenti in bibliografia, il modello teorico proposto da G. Chryssolouris, perché è quello che tratta il processo di incisione laser. Il modello teorico non segue i dati sperimentali, quindi è stato sviluppato un modello empirico (di tipo analitico) che, partendo dai dati richiesti dal software, riesce a prevedere la profondità di marcatura con buona approssimazione. Il modello sviluppato sui risultati ottenuti con l’AISI 304 ha trovato conferma sull’altro acciaio. Nelle figure successive si riportano per entrambi i materiali la profondità prevista in funzione della profondità misurata. I principali risultati possono essere riassunti nelle seguenti osservazioni: •La profondità di marcatura risulta fortemente influenzaa dalla tensione di alimentazione dei diodi, dalla velocità di movimentazione del fascio e dalla frequenza di ripetizione degli impulsi; in particolare aumenta all’aumentare della corrente e al diminuire della velocità, mentre presenta un massimo per valori di frequenza intorno ai 6.000 – 8.000 Hz. •La larghezza della marcatura al contrario è poco influenzata dalla velocità e dalla corrente, mentre risulta debolmente decrescente con la frequenza fino a un valore prossimo ai 5.000 Hz, per poi mantenere un andamento sostanzialmente costante. •E’ stato individuato un valore di frequenza ottimale: 8.000 Hz. A tale valore infatti corrisponde una geometria del solco regolare e la profondità massima. •Il modello empirico conduce a risultati che sono in buon accordo con quelli sperimentali. •Il modello trovato è particolarmente utile poiché permette di prevedere la profondità dell’incisione utilizzando direttamente i parametri impostabili dalla macchina

Nuove prospettive nella decorazione laser dei pellami, Applicazioni LASER NEW PERSPECTIVES IN LASER DECORATION OF LEATHER

Il lavoro illustra lo stato dell'arte sull'applicazione delle sorgenti laser nella decorazione dei pellami e raccoglie i risultati delle ricerche condotte dal Gruppo di Ricerca di Tecnologie e Sistemi di Lavorazione dell'Università degli Studi di Napoli Federico II in collaborazione con il Centro Interuniversitario di Ricerca sulle Tecnologie Innovative per i Beni Strumentali (CIRTIBS). In particolare, sarà illustrata l'applicazione delle sorgenti verdi nella decorazione dei pellami, evidenziandone i vantaggi rispetto alle sorgenti laser attualmente in uso in ambito conciario (sorgenti CO2); i diversi meccanismi d'interazione e le tecniche di decorazione. Quanto detto sarà discusso attraverso l'illustrazione di alcuni esempi di lavorazioni ottenuti su diverse tipologie di pellami. Infine saranno prospettati i possibili sviluppi futuri della tecnologia. This paper summarizes "the state of art of the application of laser decoration on leather, by reporting the results of research conducted at the University of Naples Federico II by the Technologies and Manufacturing System Research Team. in collaboration with the CIRTIBS Research Centre. The use of the green laser sources, in leather decoration, will be presented. The main advantages will be showed, comparing the green laser interaction modes to the: obtainable adopting a CO2 laser source. The process strategies and decoration techniques will be presented showing some examples of work carried out on different leather kinds. Finally, the possible trends going into the future will be discussed

Nuove prospettive nella decorazione laser dei pellami

Il lavoro illustra lo stato dell’arte sull’applicazione delle sorgenti laser nella decorazione dei pellami e raccoglie i risultati delle ricerche condotte dal Gruppo di Ricerca di Tecnologie e Sistemi di Lavorazione dell’Università degli Studi di Napoli in collaborazione con il Centro Interuniversitario di Ricerca sulle Tecnologie Innovative per i Beni Strumentali (CIRTIBS). In particolare, sarà illustrata l’applicazione delle sorgenti verdi nella decorazione dei pellami, evidenziandone i vantaggi rispetto alle sorgenti laser attualmente in uso in ambito conciario (sorgenti CO2); i diversi meccanismi d’interazione e le tecniche di decorazione. Quanto detto sarà discusso attraverso l’illustrazione di alcuni esempi di lavorazioni ottenuti su diverse tipologie di pellami. Infine saranno prospettati i possibili sviluppi futuri