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In this study, the parameters for underwater laser cutting of 50-mm thick stainless steel, which is typically used in nuclear power structures, are investigated. The focal position of laser beam significantly affects the cutting quality. In particular, in the cutting of the thick sample, change in the focal position determines the kerf width and the roughness of the cut surface. Moreover, the effects of the variation of kerf width and the cut surface characteristics on the focal position of the laser beam are investigated. As the focal position moved to the inside of the material, the upper kerf width increased, but the quality of the cut surface was improved.

The reactors, in which underwater laser cutting is applied, are usually more than 10m high, and the inside of the reactor is filled with coolant. It is necessary to investigate underwater laser cutting by constructing a pressurized water tank that simulates a 10-meter-deep environment in consideration of the 10-meter-deep environment where underwater cutting will be performed during actual reactor dismantling. Therefore, this study aims to first examine the effect of water pressure on laser cutting in an underwater environment and then analyze the quality of the cut part according to the cutting direction and nozzle diameter.

A basic study was conducted to investigate the correlation between assist gas pressure and the amount of secondary waste generated during underwater laser cutting for nuclear decommissioning. The assist gas pressure, i.e. the main parameter, was changed from 2 to 15 bar. Cutting quality was evaluated based on the shape of the cutting cross-section and the roughness of the cutting surface. In addition, the weight loss closely related to the generated secondary waste was calculated, and the schlieren method was used to check the gas flow according to the assist gas pressure. Satisfactory cutting quality could be obtained at a minimum assist gas pressure of 10 bar, and the weight loss related to secondary waste was less. When the cutting quality was good, the weight loss was less, and secondary waste generated was minimum.

In this paper, we present a new method that is capable of manufacturing microfluidic chips of polymethyl methacrylate (PMMA) rapidly and cheaply. This technique, which we call Tape adhering-Laser Cutting and Sealing Integration (TLCSI), only utilizes a CO₂ laser and a piece of double-sided tape to produce a microfluidic chip in several minutes. It only has three main steps. First, the double-sided tape sticks to the surface of a PMMA substrate. Second, the microchannel should be cut on the surface of the double-sided tape. At last, a PMMA cover plate with liquid pools is pressed onto the surface of the double-sided tape and a CO₂ laser is used to cut edges of the chip for sealing the chip. We present a qualified microfluidic chip with regular microchannels and sealing strength of 1.2Mpa. Compared with most current fabrication methods, TLCSI is a quick and cost-effective way to produce microfluidic chips of PMMA.

In this study, the effect of cutting parameters on kerf quality and surface roughness in laser cutting of Al 5083 alloyed material was investigated both experimentally and statistically (Taguchi & Gray Taguchi). Experimental design was determined using the Taguchi L${}_{18}$ (2¹x 3${}^2)$ orthogonal array. Experiments were carried out by using two different gas pressures (GP) (8 and 10 bar), three different cutting speeds (CS) (3500, 4000 and 4500mm$\cdot$min${}^{-1})$ and laser power (P) (2600, 3100 and 3600W) in the cutting of Al 5083 alloyed material. As a result of the study, top kerf width (TKW), bottom kerf width (BKW) and average surface roughness (Ra) were measured as output parameter values. Using the measured top and BKW results, kerf taper (KT) was calculated. The lowest values of TKW, BKW, KT and Ra were 2.219mm, 2.010mm, 0.984^∘ and 2.394$\mu$m, respectively. To determine the optimum values of laser cutting parameters for minimum output parameters, signal-noise (S/N) ratio, variance and regression analysis, validity experiments and GRA methods were used. When S/N ratios were examined, the most ideal cutting parameters were determined as A₁B₃C₁ for TKW and BKW, A₂B₁C₃ for KT and A₂B₃C₃ for Ra. When the variance results were examined, it was determined that the most effective processing parameter for TKW, BKW and KT was at 46.04%, 50.58% and 56.45% CS, respectively, and the most effective processing parameter for Ra was laser power with 46.57%. According to gray relationship analysis, optimum laser cutting parameters for the smallest values of all output parameters were determined as A₁B₃C₁. According to gray relationship analysis, optimum laser cutting parameters for the smallest values of all output parameters were determined as A₁B₃C₁.

Laser cutting is a one of the efficient manufacturing processes in industry to cut the hard materials by vaporizing. Stainless steel (SS347) is the most popular material for many applications due its unique characteristics such as efficiency to retain good strength with no inter-granular corrosion even at elevated temperatures. However, the cutting or machining of this material is very difficult. On the other side, the machining cost of laser process is high when compared with other processes. In this work, GRA and TOPSIS techniques are used to study the laser cutting process parameters of SS347. The obtained results were compared with the data mining approach. The input parameters are power, speed, pressure and stand-off distance (SOD) and the output responses of surface roughness, machining time and HAZ are considered. The set of experiments were constructed by using the Taguchi’s L9 method. The predicted closeness value of TOPSIS is greater than the GRA technique and the predominant factor observed is SOD followed by pressure, speed and power. In this work, C4.5-decision tree algorithm is applied to find the most influential parameter. It also represents the low-level knowledge of data set into high level knowledge (If-Then rules form). This investigation reveals that both TOPSIS and data mining suggested the SOD as predominant factor. This result of the optimized process parameters supports the laser assisted manufacturing industries by providing optimized output. Better results were obtained using the optimized set of parameters with the machining time, HAZ and surface roughness being 7.83 s, 0.09 mm and 0.86 $\mu$m, respectively. The results of this work would be very useful for automobiles and aircrafts industries where SS347 is highly employed.

Due to the strict requirements from the government for CO₂ emission of vehicles, Light-Weight design is now one of the most important and popular topic in automotive manufacturing. Therefore, the hot forming steel, as a high strength material, is used for manufacturing of more and more automotive body parts. And the laser is now a mandatory tool in the manufacturing. TRUMPF, as a leader of Laser manufacturing technology, is devoting its effort to improve the existing laser processes, such as 3D laser cutting, laser ablation of Al-Si coating and laser welding of patchwork. Meanwhile, we're also developing new applications for manufacturing of hot forming parts, such as laser softening of the hot forming parts on a certain area for diverse purpose. This paper demonstrates our latest development and new trends of the laser applications for hot forming parts.

In this study, the parameters for underwater laser cutting of 50-mm thick stainless steel, which is typically used in nuclear power structures, are investigated. The focal position of laser beam significantly affects the cutting quality. In particular, in the cutting of the thick sample, change in the focal position determines the kerf width and the roughness of the cut surface. Moreover, the effects of the variation of kerf width and the cut surface characteristics on the focal position of the laser beam are investigated. As the focal position moved to the inside of the material, the upper kerf width increased, but the quality of the cut surface was improved.