Analysis of process efficiency in laser fusion cutting and some single- and multi-objective optimization aspects

For an efficient use of laser cutting technology, it is of great importance to analyze the impact of process parameters on different performance indicators, such as cut quality criteria, productivity criteria, costs as well as environmental performance criteria (energy and resource efficiency). Having this in mind, this study presents the experimental results of CO2 laser fusion cutting of AISI 304 stainless steel using nitrogen, with the aim of developing a semi-empirical mathematical model for the estimation of process efficiency as an important indicator of the achievable energy transfer efficiency in the cutting process. The model was developed by relating the theoretical power needed to melt the volume per unit time and used laser power, where the change of kerf width was modeled using an empirical power model in terms of laser cutting parameters such as laser power, cutting speed, and focus position. The obtained results indicated the dominant effect of the focus position on the change in process efficiency, followed by the cutting speed and laser power. In addition, in order to maximize process efficiency and simultaneously ensure high cut quality without dross formation, a laser cutting optimization problem with constraints was formulated and solved. Also, a multi-objective optimization problem aimed at simultaneous optimization of process efficiency and material removal rate was formulated and solved, where the determined set of Pareto non-dominated solutions was analyzed by using the entropy method and multi-criteria decision analysis method, that is, the Technique for Order of Preference by Similarity to Ideal Solution. The optimization results revealed that in order to enhance process efficiency and material removal rate, while ensuring high cut quality without dross formation, focusing the laser beam deep into the bulk of material is needed with particular trade-offs between laser power and cutting speed levels at high pressure levels of nitrogen.

Melting Cell Based Compensated Design Method for Improving Dimensional Accuracy of Additively Manufactured Thin Channels

Powder-bed fusion additive manufacturing technology makes it possible to produce parts with complicated geometry and high accuracy. However, dimensional deviation caused by powder overmelting and dross formation is still a challenge for manufacturing thin channels. In this study, the origins of the overmelting of printed thin channels were analyzed and a concept called “melting cell” is proposed to describe and quantify the geometric error. Based on the geometrical relationship between the melting cell and target channel, a method for predicting and optimizing the final geometry of thin channels is outlined. In order to verify the method, geometries of thin horizontal circular channels in various sizes are studied as examples. The predicted results by the proposed method show a remarkable agreement with available experimental results. Moreover, a new egg-shaped compensated design, which is able to improve the dimensional accuracy of thin horizontal circular channels, is presented. The proposed method is simple yet very effective. It can be easily extended to the manufacturing of thin channels with various shapes, materials, and different powder bed fusion processes.

Analysis of Laser Cutting of 1.2mm Thick Austenitic Stainless Steel

Stainless steel 304 is one of the most commonly used steel types for corrosion resistance applications, but higher melting point is a limitation in industries from a manufacturing point of view. The non-conventional and subtractive manufacturing technique of laser cutting — a beam directed method, is suitable for these applications. A Gaussian laser beam is directed at the material that melts, burns, vaporizes, or is blown away by a jet of gas, leaving a fine edge with good surface finish. In this study, a numerical study was performed to study the multi-physical fluid processes of laser cutting. Towards this, modeling was performed using 1.2 mm thick austenitic stainless-steel coupons that was cut using a continuous width neodymium-doped yttrium aluminum garnet (CW Nd: YAG) laser. The results showed smoother surface cut, little dross formation, lower temperature rise in heat affected zones, and less finish time at a cutting speed of 8m/min, higher laser power above 1000 W, gas pressure of 11 bars, and focus distance of −1.0 mm. It was observed that an increase in laser power at a faster cutting speed led to an increase in kerf width, reduction in dross formation, lower temperature rises in heat affected zones and a reduced finish time. The simulation results were compared with published experimental data and found to be well within a maximum difference of 15%.

State-Of-The-Art and Trends in CO2 Laser Cutting of Polymeric Materials—A Review

Carbon dioxide (CO2) laser cutting finds one of its most relevant applications in the processing of a wide variety of polymeric materials like thermoplastics and thermosetting plastics. Different types of polymeric materials like polypropylene (PP), polymethyl methacrylate (PMMA), low- and high-density polyethylene (LDPE, HDPE), are processed by laser for different household as well as commercial products in the industry. The reason is their easy availability and economical aspect in the market. The problems associated with laser cutting include heat-affected zone (HAZ) generated on the cut surface, kerf width (KW), surface roughness (SR), dross formation, and striations formation. Furthermore, other related problems include taper cutting for deep parts and high-power consumption. The primary purpose of this work is a comprehensive literature review in CO2 laser cutting of polymeric materials. The influence of parametric variation on the cut quality is also explained. Cut quality in terms of KW, SR, HAZ, dross formation, and striations formation is analyzed by optimizing cutting variables like laser power (PL), cutting speed (CS), assist gas pressure (Pg), pulse frequency, nozzle type and its diameter, and stand-off distance (SOD). The effects of the laser cutting on the properties of different thermoplastics/thermosetting materials are also reported. However, this topic requires further studies on exploring the range of polymeric materials, and their optimal parameters selection to improve the cut quality. Therefore, the research gaps and future research directions are also highlighted in the context of CO2 laser cutting for polymeric materials.

The Evaluation on Corrosion Resistance and Dross Formation of Zn–23 wt% Al–0.3 wt% Si–x wt% Mg Alloy

: A comparative study of the corrosive resistance and dross formation of 55Al–Zn–1.6Si (wt%) (55AZS) and 23Al–Zn–0.3Si–xMg (wt%) (23AZS–xMg, x = 0, 1.5, 3) alloys are performed using immersion corrosion and dross formation test, respectively. The result of immersion corrosion testing shows that corrosive rate of the 23AZS alloy is lower than that of 55AZS alloy in the latter stage of immersion and 23AZS–1.5Mg alloy shows the optimal corrosive resistance compared to other alloys relatively. The result of dross formation test shows that the number of bottom dross particle formed in 23AZS–xMg (x = 0, 1.5, 3) alloy is less than that in 55AZS alloy. Moreover, the thermodynamic calculation is performed to reveal the solubility of Fe in the alloys, the result shows the solubility of Fe reduces as a decrease of Al content in the alloy, and the number of dross particle (Fe4Al13 and 6 (Al9Fe2Si2) phase) generated in 23AZS alloy is more than that in 55AZS alloy. In general, 23AZS–1.5Mg alloy has an advantage of less dross and a certain corrosion resistance and it is expected to be applied for the hot stamping process of coating.