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Due to their high speed and versatility, laser processing systems are now commonplace in many industrial production lines. However, as the need to reduce the environmental impact from the manufacturing industry becomes more urgent, there is the opportunity to evaluate laser processing systems to identify opportunities to improve energy efficiencies and thus reduce their carbon footprint. While other researchers have studied laser processing, the majority of previous work on laser systems has focused on the beam–material interaction, overlooking the whole system viewpoint and the significance of support equipment. In this work, a methodical approach is taken to design a set of energy modelling terminologies and develop a structured power metering system for laser systems. A 300 W fibre laser welding system is used to demonstrate the application of the power characterization system by utilizing a purpose-built power meter. The laser is broken down according to sub-system, with each part analysed separately to give a complete overall power analysis, including all auxiliary units. The results show that the greatest opportunities for efficiency improvements lie in the auxiliary units that support the laser devices as these were responsible for a majority of the electrical draw; 63.1% when the laser was operated at 240 W, and increasing as the beam power reduced. The remaining power draw was largely apportioned to electrical supply inefficiencies. In this work, the laser device delivered a maximum of 6% of the total system power. The implications of these results on laser processing system design are then discussed as is the suitability of the characterization process for use by industry on a range of specific laser processing systems.

In laser cladding, the potential benefits of wire feeding are considerable. Typical problems with the use of powder, such as gas entrapment, sub-100% material density and low deposition rate are all avoided with the use of wire. However, the use of a powder-based source material is the industry standard, with wire-based deposition generally regarded as an academic curiosity. This is because, although wire-based methods have been shown to be capable of superior quality results, the wire-based process is more difficult to control. In this work, the potential for wire shaping techniques, combined with existing holographic optical element knowledge, is investigated in order to further improve the processing characteristics. Experiments with pre-placed wire showed the ability of shaped wire to provide uniformity of wire melting compared with standard round wire, giving reduced power density requirements and superior control of clad track dilution. When feeding with flat wire, the resulting clad tracks showed a greater level of quality consistency and became less sensitive to alterations in processing conditions. In addition, a 22% increase in deposition rate was achieved. Stacking of multiple layers demonstrated the ability to create fully dense, three-dimensional structures, with directional metallurgical grain growth and uniform chemical structure.

Within the family of thin-film photovoltaics (PV), cadmium telluride has the fastest growing market share due to its high efficiencies and low cost. However, as with other PV technologies, the energy required to manufacture the panels is excessive, encompassing high environmental impact and manufacturing energy payback times of the order of 2-3 years. As part of the manufacturing process, the panels are annealed at temperatures of approximately 400 °C for 30 min, which is inherently inefficient. Laser heating has previously been investigated as an alternative process for thin-film annealing, due to its advantages with regard to its ability to localize heat treatment, anneal selectively, and its short processing time. In this investigation, results focusing on improvements to the laser-based annealing process, designed to mitigate panel damage by excessive thermal gradients, are presented. Simulations of various laser beam profiles are created in COMSOL and used to demonstrate the benefit of laser beam shaping for thin-film annealing processes. An enabling technology for this, the holographic optical element, is then used to experimentally demonstrate the redistribution of laser beam energy into an optimal profile for annealing, eliminating thermal concentrations.

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Laser cladding with wire utilises a focussing lens to melt the surface of the substrate, into which the wire is fed to build up a clad track on the surface. Process reliablity issues in practice include; clad tracks with high levels of dilution, surface cracking and other defects. Key to this is wire reflectivity calculations. Here using Fresnel equations that relate angle of incidence to heat absorption, we are able to show a direct correlation between the applied heat profile of the laser beam and the absorption profile of the wire surface; this has been modelled using COMSOL multiphysics conduction simulations which showed that the heat profile of the applied laser beam has a direct effect on the size and shape of the resulting melt pool. Using computer generated Holographic Optical Elements (HOE), a novel form of optic that alters the heat profile of the laser beam to a user-specified 3d profile, a conventional 1.25 mm diameter Gaussian beam shape and a 1.25 mm square uniform 'pedestal' HOE-derived beam shape were tested and compared, using a 1 mm diameter AISI 316 stainless steel wire on a 0.8mm mild steel substrate. These results were also compared to an enlarged 3.5 mm diameter Gaussian beam, in order to evaluate different methods of altering the heat distribution applied to the wire. The HOE generated beam gave superior results, due to its shorter thermal cycle, which reduced the amount of heat going into the clad track and resulted in lower dilution.

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