This experimental study investigated the effect of laser parameters on the machining of SS41 and SUS304. The metallic materials play an important role in engineering applications. They are widely used in high-tech industries such as aerospace, automotive, and architecture. Due to the development of technology and high-tech industrialization, the various processing technologies are being developed with the requirement of high precision. However, the conventional cutting process is difficult to meet high precision processing. Therefore, to achieve high precision processing of the SS41 and SUS304, laser manufacturing has been applied. The current study investigated the process quality of laser cutting for SS41 and SUS304, with the usage of a continuous wave CO2 laser cutting system. The experimental variables are set to the laser cutting speed, laser power, and different engineering materials. The results are significantly affected by the laser parameters. As the result, the process quality of the laser cutting has been observed by measuring the top and bottom kerf widths, as well as the size of the melting zone and Heat Affected Zone (HAZ) according to volume energy. In addition, the evaluation of the laser processing parameters is significantly important to achieve optimal cutting quality. Therefore, we observed the correlation between the laser parameters and cutting quality. These were evaluated by analysis of variance (ANOVA) and multiple regression analysis. The experimental results of kerf top, kerf bottom, melting width, and HAZ on the laser parameters are properly predicted by multiple regression. In addition, the effect of laser parameters on the materials is determinant by the percentage of contribution of ANOVA.

https://www.mdpi.com/1996-1944/13/20/4596/pdf

The Effect of Laser Parameters on Cutting Metallic Materials.

Laser cutting parameters synergistically affect, although in different quantitative and qualitative manners, multiple process performances, such as the resulting cut quality characteristics, material removal rate, cutting time, and costs, and the determination of the most appropriate laser cutting conditions for a given application is of prime importance. Given the existence of multiple mutually opposite performances, assessment and laser cutting conditions and performance can be considered a multiple-criteria decision-making (MCDM) problem. In order to overcome the possible inconsistency of rankings determined by different MCDM methods while solving the same decision-making problem, the present study promotes a novel methodology for the assessment and selection of laser cutting conditions by developing a robust decision-making rule (RDMR) that combines different decision-making rules from six MCDM methods and Taguchi’s principles of robust design. In order to illustrate the application of the proposed methodology, CO2 laser cutting in a stainless-steel experiment, based on the use of the Box–Behnken design, was conducted. On the basis of the experimental results, a comprehensive laser cutting MCDM model was developed with seven criteria related to cut quality (i.e., kerf geometry and cut surface), productivity, variable costs, and environmental aspects. It was observed that there was no laser cutting condition that could be considered as the best regime with respect to the different laser cutting process performances. Kendall’s and Spearman’s rank correlation coefficients indicated a certain level of disagreement among the resulting rankings of the laser cutting conditions produced by the considered MCDM methods, whereas the application of the proposed RDMR ensured the highest level of ranking consistency. Some possibilities for modeling of RDMR and its further use for the assessment of arbitrarily chosen laser cutting conditions and the use of the derived model to perform sensitivity analysis for determining the most influential laser cutting parameters are also discussed and addressed. It was observed that laser cutting parameters in different laser cutting conditions may have a variable effect on the resulting overall process performances. The comparison of the obtained results and the results determined by classical desirability-based multi-objective optimization revealed that there exists substantial agreement between the most preferable and least preferable laser cutting conditions, thus justifying the applied methodology.

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Application of a Robust Decision-Making Rule for Comprehensive Assessment of Laser Cutting Conditions and Performance

Laser cutting of advanced engineering materials has now become quite attractive due to its various unique characteristics, like no tool wear, no built-up edge formation, no residual stress generation, no vibration etc. In order to enable this machining process to operate at its maximum competency, its’ different input parameters are often set at their optimal operating levels. This paper presents the applicability of superiority and inferiority multi-criteria ranking (SIR) method for determination of the best-suited parametric combinations for an Nd:YAG and a pulsed CO2 (carbon dioxide) laser cutting processes. The derived optimal parametric mixes obtained for the two considered laser cutting processes are validated based on the developed regression equations. In the Nd:YAG laser cutting process, an optimal parametric combination of gas pressure = 3 kg/cm2, pulse width = 0.6 ms, pulse frequency = 23 Hz, and cutting speed = 20 mm/min reduces the values of kerf width, kerf deviation, and kerf taper angle by 1.71, 2 and 25.88%, respectively. For the pulsed CO2 laser cutting process, the optimal mix determined as laser beam power = 3000 W, cutting velocity = 10 mm/s, gas pressure = 1.2 MPa and pulse frequency = 10 Hz causes reduction of 25.81, 6.65 and 2.84% in the values of surface roughness, kerf width and cut edge slope, respectively. Thus, it can be established that the response values estimated using the SIR method are better than those derived by the other optimisation techniques, while demonstrating its potentiality for parametric optimisation of laser cutting processes leading to enhanced performance.

Application of Superiority and Inferiority Multi-criteria Ranking Method for Parametric Optimization of Laser Cutting Processes

This paper presents an experimental research that proposes to determine the influence of process parameters on CO2 laser cutting of 8 mm thick Hardox 400 steel, for which Kerf has a minimum value. The experimental research was conducted according to a complete factorial plan with laser power, assistant gas pressure and cutting speed as the input parameters, and cutting width as the dependable variable. The Design of Experiment (DOE) consisted of 27 references and was completed with four replicas to determine the variation of the Kerf average. Functional, linear and quadratic relations were determined, which describe the Kerf dependence on the cutting parameters in order to establish the most influential parameter. The results show that the independent parameter with the most significant influence was the laser power, with minimum Kerf obtained if the laser power and the assistant gas pressure were adjusted to average values. The interaction between laser power and auxiliary gas pressure at constant cutting speed was investigated to improve Kerf and reduce the laser processing cost. The study offers the right combination of process parameters that leads to a minimum value of the cutting width.

Influence of Process Parameters on Cutting Width in CO2 Laser Processing of Hardox 400 Steel

For the successful implementation of innovative automated technological processes, such as high speed machining, 3D laser welding, 3D laser cutting and laser cladding it is necessary to provide highly effective control of the working tool movement speed in multi-axis space of cyber-physical system. A simplified three-interval model S-shaped feedrate profile with smoothly-limited jerk using the sin2 function are proposed. An algorithm for pre-scheduling of the feedrate before the start of motion control, which has no constraints on the number of analyzed blocks and the scheduling execution time is proposed. Modeling the scheduling process on the example of a test trajectory has shown the high efficiency of the proposed model. Reduction of the processing time of the control section of the trajectory by 7.4% to 10.7% in comparison with the Heidenhain iTNC530 system with the same acceleration and jerk limitations are obtained.

S-Shape Feedrate Scheduling Method with Smoothly-Limited Jerk in Cyber-Physical Systems

Analysis and optimization of surface quality of stainless steel miniature gears manufactured by CO2 laser cutting

The feasibility of joining laser metal deposited Ti6Al4V sheets using laser beam welding was investigated in this article. The additive manufactured sheets were joined using a 3 kW CW YLS-2000-TR ytterbium laser system. The mechanical properties and microstructure of the welded additive manufactured parts (AM welds) were compared with those of the wrought sheets welded using the same laser process. The welds were characterized and compared in terms of bead geometry, microhardness, tensile strength, fractography, and microstructure. The differences in characteristics are majorly found in the width of the bead and tensile strength. The bead width of AM welds appear wider than the wrought welds, and the wrought welds exhibited higher tensile strength and ductility than the AM welds. 

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Joint integrity evaluation of laser beam welded additive manufactured Ti6Al4V sheets

Effect of power and deposition time on sputtered hydroxyapatite thin film coatings on stainless steel 304

High entropy alloy (HEA) thin films of CrCoCuFeNi are grown on stainless steel substrate using radiofrequency (RF) magnetron sputtering method at different sputtering times (30, 60 and 90 minutes), substrate temperatures (room temperature, 100 and 200 deg. Celsius) and RF powers (100, 150 and 200 W). The nanoscale morphology and topography of the thin films are obtained using an atomic force microscopy (AFM) method. The average surface roughness, interface width, fractal and multifractal characteristics of the films are presented. It is shown that the average surface roughness and interface width decrease with the time of deposition while considering the combination of the other factors. The autocorrelation and height-height correlation functions reveal that these surfaces are self-affine and exhibit fractal characteristics. The increase in sputtering power, with different combinations of time and temperature, is related to large fractal dimension and small lacunarity coefficient. The increase in substrate temperature (for different combinations with time and RF power) is shown to enhance the spatial roughness of the HEA thin films. A multifractal analysis undertaken using generalized fractal dimension, mass exponent against moment order and multifractal spectrum reveal that all the films have a multifractal character; and the films deposited at high temperatures and powers exhibit the strongest multifractal behaviour. 

Nanoscale surface dynamics of RF-magnetron sputtered CrCoCuFeNi high entropy alloy thin films

Cutting fluids have a known negative impact on productivity, human health, and the environment in the manufacturing sector. A suitable method for reducing the effect of cutting fluids on human health and the environment is minimum quantity lubrication (MQL). In this experiment, AISI 1039 steel was machined using vegetable oil lubricant and MQL. A chemical method was used to extract vegetable oil from palm kernel seeds. Then, using established techniques, the physicochemical and lubricity properties of palm kernel oil (PKO) were ascertained. The Taguchi L9 (33) orthogonal array served as the basis for the planning of the experimental design. Process parameters such as surface roughness, chip thickness ratio, cutting temperature, and material removal rate were measured during the turning operations. The multi-response outputs from TGRA were considered to simultaneously optimize the cutting parameters namely depth of cut, feed rate, and spindle speed. At a temperature of 55°C, 180 minutes, and particle sizes of 0.2–0.5 mm, an oil yield of 55% by weight was obtained. The viscosity at 40°C, specific gravity, pour, fire, cloud, and flash points of the raw PKO were 117.6 mm2/s, 0.8940 mg/ml, 21°C, 231°C, 22.3 °C and 227°C, respectively. The surface roughness and cutting temperature of PKO improved by 44% and 12%, respectively, when compared with mineral oil. The findings of this research confirmed the effectiveness of the integrated Taguchi-grey relational analysis (TGRA) optimization method and established an experimental foundation for the use of PKO minimum quantity lubrication turning. 

T.C. Jen

Papers

Analysis and optimization of surface quality of stainless steel miniature gears manufactured by CO2 laser cutting

Joint integrity evaluation of laser beam welded additive manufactured Ti6Al4V sheets

Effect of power and deposition time on sputtered hydroxyapatite thin film coatings on stainless steel 304

Nanoscale surface dynamics of RF-magnetron sputtered CrCoCuFeNi high entropy alloy thin films

Evaluation of palm kernel oil as cutting lubricant in turning AISI 1039 steel using Taguchi-grey relational analysis optimization technique