The coaxial Laser Double-wire Directed Energy Deposition (LD-DED) process is capable of providing two wire materials simultaneously into a common processing zone. Thus, in-situ production of alloys in a local manner or across the entire sample can be realized with the characteristic high material utilization of the laser wire Directed Energy Deposition (DED) processes. Fabricated samples show a homogenous distribution of alloying elements across single welding seams enabling a functionally graded transition zone along multi-layer samples. This work shows the potentials of the LD-DED process for the production of Functional Graded Materials (FGM). Therefore, the process is displayed and single welding seams are examined regarding the element distribution along the seam with a graded material distribution. The samples are produced with a horizontally graded material transition using 1.4430 and 1.4718 stainless steel wires. All samples are fabricated using the multiple Diode Coaxial Laser (DiCoLas) processing head of the Laser Zentrum Hannover e.V. The processing head provides the materials under a small angle of incidence and utilizes three fiber coupled laser diodes to supply the necessary thermal energy for the melting process of the base and wire materials. Using Energy-Dispersive X-ray spectroscopy (EDX) line-scans and mappings to determine the element constituents along the cross-section, a graded transition of elements in the horizontal direction can be detected. Images captured with a Keyence VK-X1100 3D-laser-scanning microscope provide information of the cross-section quality regarding material defects and surface quality. Furthermore, the Vickers hardness progression along the building direction is measured.
Additive Manufacturing of glass opens up new possibilities for the design and integration of optical components. By varying the shape and size of optical elements, optical systems specifically adapted to various applications can be fabricated cost-effectively. The Laser Glass Deposition (LGD) process uses a CO2 laser with a wavelength of 10.6 μm to locally generate temperatures above 2000 °C in fused silica fibers. This enables the Additive Manufacturing and Rapid Prototyping of glass by melting and then layer-by-layer deposition of fibers. However, these high temperatures can result in very high residual stress in the material. The development of a coaxial LGD process aims for a more uniform heating of the glass fiber during the printing process in order to enable a direction-independent process and to reduce the residual stresses within the printed components. In this work, a novel concept for the coaxial LGD process and its successful experimental application is presented. Further, a numerical simulation model is developed to describe the temperature distribution in the glass fiber during the coaxial LGD process. Based on experimental results and on the numerical simulation, the potentials and challenges of the coaxial LGD process are discussed.
The use of additive manufacturing methods in research and industry has led to the possibility of designing more compact, light and low-cost assemblies. In the field of laser development, new opportunities resulting from additive manufacturing have rarely been considered so far. We present a compact, lightweight solid-state amplifier system for low-power applications where the optomechanical components are manufactured completely additive via Fused Filament Fabrication (FFF). The amplifier system is based on a Nd:YVO4-crystal pumped with an external, fiber-coupled diode at a wavelength of 808nm and a maximum output power of 3 W. The seed source is a Nd:YVO4-crystal based solid-state laser with an emission wavelength of 1064 nm. The commercial optical components, such as lenses and crystal, are firmly imprinted via FFF in the optomechanics and thus secured against misalignment. Additionally, sensor technology for temperature measurement is implemented into the devices. The use of FFF, in which the components are printed from polymers, results in a lightweight yet stable construction. We have shown, that optical components can be imprinted without adding mechanical stress. To increase the mechanical and thermal robustness of the system different types of polymers as well as post process treatments are tested and the use of Laser Metal Deposition for this application is investigated. The thermal stability of the printed structures is evaluated to determine the maximum power level of the system without damaging the polymer-optomechanics. Furthermore, output power, optical-to-optical efficiency, beam pointing, and beam shape are measured for several on- and off-switching processes as well as long-term operation.
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