Historical stained-glass window laser preservation: The heat accumulation challenge

Abstract In laser processing, the possible throughput is directly scaling with the available average laser power. To avoid unwanted thermal damage due to high pulse energy or heat accumulation during MHz-repetition rates, energy distribution over the workpiece is required. Polygon mirror scanners enable high deflection speeds and thus, a proper energy distribution within a short processing time. The requirements of laser micro processing with up to 10 kW average laser powers and high scan speeds up to 1000 m/s result in a 30 mm aperture two-dimensional polygon mirror scanner with a patented low-distortion mirror configuration. In combination with a field programmable gate array-based real-time logic, position-true high-accuracy laser switching is enabled for 2D, 2.5D, or 3D laser processing capable to drill holes in multi-pass ablation or engraving. A special developed real-time shifter module within the high-speed logic allows, in combination with external axis, the material processing on the fly and hence, processing of workpieces much larger than the scan field.

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Modeling of three-dimensional exciplex pumped fluid Cs vapor laser with transverse and longitudinal gas flow

High Power Laser Science and Engineering ◽

10.1017/hpl.2021.8 ◽

2021 ◽

Vol 9 ◽

Author(s):

Chenyi Su ◽

Xingqi Xu ◽

Jinghua Huang ◽

Bailiang Pan

Keyword(s):

Wall Temperature ◽

Laser Power ◽

Gas Flow ◽

Particle Density ◽

Fluid Velocity ◽

Three Dimensional ◽

Heat Accumulation ◽

Vapor Laser ◽

Output Laser Power ◽

Output Laser

Abstract Considering the thermodynamical fluid mechanics in the gain medium and laser kinetic processes, a three-dimensional theoretical model of an exciplex-pumped Cs vapor laser with longitudinal and transverse gas flow is established. The slope efficiency of laser calculated by the model shows good agreement with the experimental data. The comprehensive three-dimensional distribution of temperature and particle density of Cs is depicted. The influence of pump intensity, wall temperature, and fluid velocity on the laser output performance is also simulated and analyzed in detail, suggesting that a higher wall temperature can guarantee a higher output laser power while causing a more significant heat accumulation in the cell. Compared with longitudinal gas flow, the transverse flow can improve the output laser power by effectively removing the generated heat accumulation and alleviating the temperature gradient in the cell.

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Parameters Optimization of Auxiliary Gas Process for Double-Wire SS316L Stainless Steel Arc Additive Manufacturing

Metals ◽

10.3390/met11020190 ◽

2021 ◽

Vol 11 (2) ◽

pp. 190

Author(s):

Wei Wu ◽

Jiaxiang Xue ◽

Wei Xu ◽

Hongyan Lin ◽

Heqing Tang ◽

...

Keyword(s):

Stainless Steel ◽

Additive Manufacturing ◽

Process Parameters ◽

Evaluation System ◽

Gas Flow ◽

Interactive Effect ◽

Parameters Optimization ◽

Heat Accumulation ◽

Auxiliary Process ◽

Strength And Stiffness

Serious heat accumulation limits the further efficiency and application in additive manufacturing (AM). This study accordingly proposed a double-wire SS316L stainless steel arc AM with a two-direction auxiliary gas process to research the effect of three parameters, such as auxiliary gas nozzle angle, auxiliary gas flow rate and nozzle-to-substrate distance on depositions, then based on the Box–Behnken Design response surface, a regression equation between three parameters and the total score were established to optimized parameters by an evaluation system. The results showed that samples with nozzle angle of 30° had poor morphology but good properties, and increasing gas flow or decreasing distance would enhance the airflow strength and stiffness, then strongly stir the molten pool and resist the interference. Then a diverse combination of auxiliary process parameters had different influences on the morphology and properties, and an interactive effect on the comprehensive score. Ultimately the optimal auxiliary gas process parameters were 17.4°, 25 L/min and 10.44 mm, which not only bettered the morphology, but refined the grains and improved the properties due to the stirring and cooling effect of the auxiliary gas, which provides a feasible way for quality and efficiency improvements in arc additive manufacturing.

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