Browsing by Author "Ninikas, Konstantinos"

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    An experimental study of laser cutting of PLA-wood flour 3D printed plates using a modified Taguchi design
    (Inderscience, 2023-05-30) Kechagias, John D.; Ninikas, Konstantinos; Salonitis, Konstantinos
    Wooden powder flour blended with thermoplastic polylactic acid (WPLA) is an eco-friendly composite material used in filament material extrusion (MEX) additive manufacturing (AM). This work investigates the effect of CO2 laser cutting (LC) of filament MEX WPLA thin plates with variable cutting parameters on mean kerf width (Wm) and means surface roughness (Ra). The experimental design consists of three parameters with three levels each, i.e., the beam cutting direction (CD: 0, 45, 90°), the cutting speed (CS: 8, 13, 18 mm/s), and the beam power (BP: 82.5, 90, 97.5 W). Eleven experiments were performed following the Taguchi L9 orthogonal array plus two in the central point. Finally, additional combinations were run and validated the suggested modified Taguchi design resulting in acceptable mean average percentage errors (MAPE). The optimum parameters' values combination (90° CD, 18mm/s CS and 97.5W BP) results in about 8.44 μm Ra and 0.355 mm Wm.
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    A generalised approach on kerf geometry prediction during CO2 laser cut of PMMA thin plates using neural networks
    (Springer, 2021-08-16) Kechagias, John D.; Ninikas, Konstantinos; Stavropoulos, Panagiotis; Salonitis, Konstantinos
    This study presents an application of feedforward and backpropagation neural network (FFBP-NN) for predicting the kerf characteristics, i.e. the kerf width in three different distances from the surface (upper, middle and down) and kerf angle during laser cutting of 4 mm PMMA (polymethyl methacrylate) thin plates. Stand-off distance (SoD: 7, 8 and 9 mm), cutting speed (CS: 8, 13 and 18 mm/sec) and laser power (LP: 82.5, 90 and 97.5 W) are the studied parameters for low power CO2 laser cutting. A three-parameter three-level full factorial array has been used, and twenty-seven (33) cuts are performed. Subsequently, the upper, middle and down kerf widths (Wu, Wm and Wd) and the kerf angle (KA) were measured and analysed through ANOM (analysis of means), ANOVA (analysis of variances) and interaction plots. The statistical analysis highlighted that linear modelling is insufficient for the precise prediction of kerf characteristics. An FFBP-NN was developed, trained, validated and generalised for the accurate prediction of the kerf geometry. The FFBP-NN achieved an R-all value of 0.98, in contrast to the ANOVA linear models, which achieved Rsq values of about 0.86. According to the ANOM plots, the parameter values which optimize the KA resulting in positive values close to zero degrees were the 7 mm SoD, 8 mm/s CS and 97.5 W LP.
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    The impact of process parameters on surface roughness and dimensional accuracy during CO2 laser cutting of PMMA thin sheets
    (MDPI, 2021-07-07) Ninikas, Konstantinos; Kechagias, John; Salonitis, Konstantinos
    This study investigated the impact of the laser speed and power, and the position and orientation of the samples, on the average surface roughness (Ra) and dimensional accuracy (DA) during CO2 laser cutting of polymethyl methacrylate (PMMA) thin sheets. A mixed five-parameter fractional factorial design was applied, and thirty-six measurements for the Ra and DA were obtained. The experimental results were analysed using ANOM diagrams, ANOVA analysis and interaction plots of all parameters. It was concluded that the laser speed is the critical parameter for both surface roughness and dimensional accuracy, resulting in strong interactions with laser power and positioning parameters. It was also shown that Ra values are affected by the orientation of the specimen and can be minimized when the samples are aligned in the laser travel direction. Finally, it was proved that lower laser speed improves the average roughness but reduces the dimensional accuracy.