Papers by Keyword: Laser Beam Machining (LBM)

Abstract: This work presents the results of manufacturing three-dimensional tensile test specimens using widespread hardware usually deployed for laser cladding. Using a laser cladding processing head with coaxial powder feed and a 3-axis-CNC-system macroscopic three-dimensional tensile test specimens have been built by means of additive manufacturing process from cobalt-based Stellite 21 powder on a substrate made of S235JR steel. The additive process has been made by generating a CAD-model of the geometry under investigation and translating it into G-Code using VisCAM RP4.0 software from Marcam Engineering usually used for selective laser melting devices. An interface translating G-Code into program code which is executable by a CNC-system has been developed, additionally the CNC-code has been extended in order to trigger the processing laser. The specimens have been generated under consideration of three different exposure strategies with respect to path orientation in order to investigate their influence on mechanical properties of processed material. After the post-processing by milling and deburring the specimen underwent tensile tests, additionally metallographic investigations and hardness measurements have been done in order to investigate the influence of process parameters on porosity, cracks distribution and hardness of Stellite 21. It has been found that there are connections between process parameters and porosity and cracks of generated samples. Compared with cast material the Young’s Modulus has been found to decrease slightly without significant relation with path orientation, while ultimate tensile strength has been found to be higher than that of cast material, with a significant dependency of the orientation of the laser path. Achieved results show the technical possibility of creating three-dimensional samples by the widespread laser cladding process and hardware. Furthermore, static mechanical properties of generated parts prove to be competitive to as-cast parts in terms of elasticity and ultimate tensile strength.

Abstract: A finite element model has been developed utilizing the commercial ANSYS software to determine the temperature distribution & heat affected zone in laser cutting of titanium alloy (Ti-6%Al-4%V).The main aim of this paper is to determine the temperature reached in the vicinity of the location where the laser interaction with the work piece material takes place. This model is based on Fourier law of heat conduction and Gaussian distribution of laser. Temperature dependent thermal and mechanical properties of material are assumed in this analysis. Result obtained are then analyzed and thermal effect is then understood for the effective control of the process.

Abstract: Laser cutting is a well-established sheet metal processing method. Nowadays a trend towards the cutting of thick plates (> 15 mm) can be observed. However for these thick plates the process window in which good cutting results can be obtained is more narrow compared to that for thin sheets due to the very difficult balance to be found between the different process parameters. Even after determination of the process window, a good cutting quality cannot always be guaranteed. Therefore cutting of thick plates is still characterized by a large scrap percentage, which impedes a breakthrough to large scale industrial use. A solution to this problem is to incorporate a sensor system in the laser cutting machine that monitors the cut quality on-line. This monitoring system could then be integrated in a process control system, which adapts the process parameters in function of the observed cut quality in real time. In this way a good cut quality could always be guaranteed. In this study, the first step in this direction, the determination of an appropriate monitoring system, is dealt with. The applicability for monitoring purposes of two types of sensors is investigated: a microphone and a photodiode. For both types, correlation between the sensor output and the cut quality is investigated in a qualitative way. The scope of the reported research was not limited to contour cutting, also piercing is covered in the study.

Abstract: Compared to welding, laser brazing offers a suitable possibility to lower the working temperature and to join unweldable material combinations, while maintaining the numerous advantages of the laser joining process. Beside an acceptable joint strength, the brazed joints are characterised by a smooth surface and seams with almost no pores. As a result of this laser brazing combines the advantages of conventional brazing and laser welding. Within the scope of this paper the laser brazing process and its characteristics are explained in detail. In particular the interrelation of temperature progress, available processing time for brazing/diffusion and the thickness of the diffusion layer is discussed. Subsequently the material specific particularities of laser brazing aluminium alloys are described and discussed with respect to recently gained results.