A Generalised Approach on Kerf Geometry Prediction during CO2 Laser cut of PMMA Thin Plates using Neural Networks

Abstract

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 CO 2 laser cutting. A three-parameter three-level full factorial array has been used, and twentyseven (3 3 ) 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.

Laser cutting of 3D printed acrylonitrile butadiene styrene plates for dimensional and surface roughness optimization

“…A low power continuous CO 2 laser (1325B, BCL) was used for conducting the experiments [15]. Assist gas was air, set at 1 bar (constant pressure), tip diameter of 2 mm was used (convergent nozzle, [16]), and the focal length was 46 mm when laser nozzle stand-off distance was set at 8 mm (0.3 mm spot diameter in focal length).…”

“…The spot diameter and the airflow distribution at the upper kerf surface changed when the SoD changed. Mirrors and lenses of the CO 2 laser configuration are presented in [15].…”

“…The tested parameters and their selected levels follow previous works and preliminary experiments [15,20,26]. The 4-mm plate thickness was selected for benchmarking with…”

“…; see Fig. 1) is influenced by several process parameters such as the focusing distance, spot diameter, cutting speed, and assistgas pressure and laser power [14][15][16].…”

“…Low power laser processing was also applied in literature to cut simple polymethyl methacrylate (PMMA) thin polymeric plates for dimensional and surface improvements [15,[20][21][22][23]. Average surface roughness of 0.6 μm and kerf angles close to 0° were obtained, by varying the processing parameters (laser power, cutting speed, etc.).…”