• Energy Research

This paper focuses on optimizing the laser engraving of acrylic plastics to reduce energy consumption and CO2 gas emissions, without hindering the production and material removal rates. In this context, the role of laser engraving parameters on energy consumption, CO2 gas emissions, production rate, and material removal rate was first experimentally investigated. Grey–Taguchi approach was then used to identify an optimal set of process parameters meeting the goal. The scan gap was the most significant factor affecting energy consumption, CO2 gas emissions, and production rate, whereas, compared to other factors, its impact on material removal rate (MRR) was relatively lower. Moreover, the defocal length had a negligible impact on the response variables taken into consideration. With this laser-process-material combination, to achieve the desired goal, the laser must be focused on the surface, and laser power, scanning speed, and scan gap must be set at 44 W, 300 mm/s, and 0.065 mm, respectively.

Abstract A methodological approach for analytical modelling of deep penetration laser beam welding (LBW) of stainless steels and its experimental verification is provided. After an analysis of the problem in general terms and a review of the modelling activity, a particular double source model is proposed and discussed. The model allows the derivation of penetration and width of melting zone caused by moving laser beam. Dependences of penetration length, width of the melting zone and aspect ratio of the zone were derived as a function of welding speed and laser power. The theoretical results obtained using the particular model are discussed and analyzed in comparison with experimental data obtained on a typical test case. Optimal conditions for obtaining a preliminary optimization of the process parameters were derived based on experimental results. The case study in the present paper, referred to the assembly of fuel injectors for automotive industry, demonstrates that when laser welding is performed at high speeds on thin wall components the energy released by the laser per unit of surface (energy density, ED) can be used to describe the heat transfer to the material and to shorten the experimental phase avoiding the dependencies on each single process parameter.

Abstract The paper analyzes energy consumption as a performance indicator for micro-manufacturing. A comparative analysis between micro-EDM and ultrashort pulse laser drilling is performed on the basis of similar process outputs like drilled thickness of 350 μm, hole diameter of 180 ± 3 μm, drilling time, micro-hole shape and inner surface quality. Experimental data revealed that ultrashort pulse laser drilling enabled root mean squared surface roughness of about 100 nm in a drilling time of 2.5 s, whereas using a conventional micro-EDM drilling operation with a 10 s duration yielded surface roughness of 380 nm. For ultrashort pulse laser ablation the specific energy consumption is increased, as the drilling time is decreased due to an increase of the adopted pulse energy up to 50 μJ but the surface roughness and the capability of obtaining very sharp edges remain unchanged. With a calculated energy intensity in the order of 10 10 J/kg and a process rate in the order of 10 −6 kg/h, ultrashort pulse laser drilling can be considered as a valid alternative from both technology point of view and specific energy consumption to similar drilling process, like micro-EDM which is characterized by a lower process rate and a higher energy intensity.

Abstract This paper presents an analysis of Selective Laser Sintering (SLS) from an energy standpoint. Selective Laser Sintering (SLS) has a potential as an environmental benign alternative to traditional processes but only few authors deal with the process optimisation including energy aspects. In the present paper an analysis of the energetic aspect of SLS is proposed. In addition, with respect to the classical technological parameters (resolution, productivity) attention is paid to energetic elements (energetic productivity, laser parameters) showing how the perspective of a sensible development of such a kind of technology could be beneficial not only from a technological point of view, but also for energy saving in a lot of manufacturing fields. A polyamide powder is the material tested to acquire some characteristics data of the process. It is shown that the Volumetric Energy Intensity (VEI) of the process in optimal condition could be of the order of 0.2 J for each mm3 of material agglomerated.

Abstract This paper presents an analysis of Laser Sintering (LS) process from an energy standpoint. LS has a potential as an environmental benign alternative to traditional processes but only few authors deal with the process optimization including the energy aspects. This work evaluates the effect of the energy density in processing of two polymeric materials: polyamide powder and a phenolic resin coated sand. The different behaviour of the two materials is studied by analysing the geometrical features (depth and width) of linear sintered structures. In particular the volumetric productivity and the energy intensity of the process are calculated to characterize the sintering process. It is shown how an upper limit to the energy consumption can be remarked. Measurements reveal that within the energy density range of 0.02–0.1 J/mm 2 the whole energy input is useful for the agglomeration process. The use of higher energy density produces different results for both the cases analysed. A proper selection of energy density maintains the energy requirement below the level of 10 6 J/kg which is considered a lower limit for manufacturing process.