Adaptive control for a dual laser beam solution for the welding of high reflectivity dissimilar materials

The laser welding technology delivers high flexibility and adaptability to the welding process being able to adjust to complex joint geometries. Additionally, the application of a laser beam minimises the microstructural changes in the material due to the low heat application and low thermal distortion that the technology offers. Due to these advantages, laser welding technology is being adopted in technologically demanding markets such as EV battery manufacturing. However, these new application areas present challenges that must be overcome, such as joining dissimilar materials with different melting points and high reflectivity values in the typical laser wavelengths (Al, Cu). This work presents an adaptive control method for joining high reflectivity dissimilar materials using a dual laser beam setup to overcome these problems. As a result, a comparative study of different pulsed and continuous-wave laser arrangements through static and dynamic optics and the obtained joining qualities is presented.The presented work has been carried out under the framework of the Neotec Project SOLAMARE, which has been funded by the Spanish Ministry of Science and Innovation through the Centre for the Development of Industrial Technology (CDTI) under agreement No. SNEO- 2019129

Dynamic control for LMD processes using sensor fusion and edge computing

The quality of an LMD manufactured object highly depends on different process parameters such as the speed of powder deposition, the applied laser power, the powder feed rate, and other physical parameters such as the substrate temperature, resulting in a complex process. Consequently, applying corrections to the process parameters can be critical to improving the properties of the manufactured part. Some control approaches rely on open-loop techniques that use physical models and expert knowledge to adjust the tool path program in advance to compensate for deviations from the theoretical 3D model. Other approaches apply closed-loop control techniques to either control the melt pool during the process or adjust the tool path between layer depositions. This work presents a closed-loop control algorithm that dynamically controls three critical process parameters: the melt pool size, deposition speed, and standoff distance, combining data from a laser line profiler and a high-speed infrared camera.The work presented in this publication has received funding from the European Union’s Horizon 2020 research and innovation programme within the framework of the Pulsate Project funded under grant agreement No [951998] as part of the experiment CESFAM selected in the Pulsate 1 st TTE open call. PULSATE is supported by the Photonics Public Private Partnership

Influence of Axial Depth of Cut and Tool Position on Surface Quality and Chatter Appearance in Locally Supported Thin Floor Milling

Thin floor machining is a challenging and demanding issue, due to vibrations that create poor surface quality. Several technologies have been developed to overcome this problem. Ad hoc fixtures for a given part geometry lead to meeting quality tolerances, but since they lack flexibility, they are expensive and not suitable for low manufacturing batches. On the contrary, flexible fixtures consisting of vacuum cups adaptable to a diversity of part geometries may not totally avoid vibrations, which greatly limits its use. The present study analyses the feasibility of thin floor milling in terms of vibration and roughness, in the cases where milling is conducted without back support, a usual situation when flexible fixtures are employed, so as to define the conditions for a stable milling in them and thus avoid the use of ad hoc fixtures. For that purpose, the change of modal parameters due to material removal and its influence on chatter appearance have been studied, by means of stability lobe diagrams and Fourier Transform analysis. Additionally, the relationship between surface roughness and chatter frequency, tooth passing frequency, and spindle frequency have been studied. Ploughing effect has also been observed during milling, and the factors that lead to the appearance of this undesirable effect have been analyzed, in order to avoid it. It has been proven that finish milling of thin floors without support in the axial direction of the mill can meet aeronautic tolerances and requirements, providing that proper cutting conditions and machining zones are selected.This research has received funding from the ELKARTEK program of the Basque Government within the project OPTICED, grant number KK-2021/00003

Development of an Intra-Layer Adaptive Toolpath Generation Control Procedure in the Laser Metal Wire Deposition Process

Recently developed concentric laser metal wire deposition (LMWD) heads allow metal addition processes which are independent of the deposition direction, thus enabling complex paths to be generated. The sensitivity of the process to height deviations has experimentally been observed to be greater with this type of head than with powder ones, therefore requiring more precise and local process control algorithms to be implemented. This work developed a methodology for measuring the part, layer by layer, using a 3D scanner based on structured laser light. Height corrections were applied to the mean and intra-layer height deviations by recalculating the deposition trajectories of the next layer to be deposited. Local height deviations were adjusted by varying the scanning speed, thus increasing the feed rate in the lower areas and decreasing it in the higher ones. Defects generated in the purpose, with height differences within the layer, were successfully corrected. A flat layer was re-established through the application of the control strategy. The internal integrity of the parts due to the scanning speed variation was analyzed, resulting in fully dense parts. The structured light measurement and height correction systems are found to be an affordable and time-efficient solution that can be integrated into an LMWD environment, thereby improving the process robustness.The authors wish to acknowledge the financial support given by IHOBE and the ERDF through the Addieco project and by the Basque Government through the Addisend project which is part of the Elkartek 2018 programme

Analysis of the Influence of the Use of Cutting Fluid in Hybrid Processes of Machining and Laser Metal Deposition (LMD)

Hybrid manufacturing processes that combine additive and machining operations are gaining relevance in modern industry thanks to the capability of building complex parts with minimal material and, many times, with process time reduction. Besides, as the additive and subtractive operations are carried out in the same machine, without moving the part, dead times are reduced and higher accuracies are achieved. However, it is not clear whether the direct material deposition after the machining operation is possible or intermediate cleaning stages are required because of the possible presence of residual cutting fluids. Therefore, different Laser Metal Deposition (LMD) tests are performed on a part impregnated with cutting fluid, both directly and after the removal of the coolant by techniques such as laser vaporizing and air blasting. The present work studies the influence of the cutting fluid in the LMD process and the quality of the resulting part. Resulting porosity is evaluated and it is concluded that if the part surface is not properly clean after the machining operation, deficient clad quality can be obtained in the subsequent laser additive operation.This study was supported by the H2020 FoF13 PARADDISE Project (Grant Agreement No. 723440)

Latest Developments in Industrial Hybrid Machine Tools that Combine Additive and Subtractive Operations

Hybrid machine tools combining additive and subtractive processes have arisen as a solution to increasing manufacture requirements, boosting the potentials of both technologies, while compensating and minimizing their limitations. Nevertheless, the idea of hybrid machines is relatively new and there is a notable lack of knowledge about the implications arisen from their in-practice use. Therefore, the main goal of the present paper is to fill the existing gap, giving an insight into the current advancements and pending tasks of hybrid machines both from an academic and industrial perspective. To that end, the technical-economical potentials and challenges emerging from their use are identified and critically discussed. In addition, the current situation and future perspectives of hybrid machines from the point of view of process planning, monitoring, and inspection are analyzed. On the one hand, it is found that hybrid machines enable a more efficient use of the resources available, as well as the production of previously unattainable complex parts. On the other hand, it is concluded that there are still some technological challenges derived from the interaction of additive and subtractive processes to be overcome (e.g., process planning, decision planning, use of cutting fluids, and need for a post-processing) before a full implantation of hybrid machines is fulfilledSpecial thanks are addressed to the Industry and Competitiveness Spanish Ministry for the support on the DPI2016-79889-R INTEGRADDI project and to the PARADDISE project H2020-IND-CE-2016-17/H2020-FOF-2016 of the European Union's Horizon 2020 research and innovation program

Study of the flexural behaviour and bonding strength of WC-Co metal matrix composite coatings produced by Laser Directed Energy Deposition

Surface coatings enable more durable and sustainable solutions to face the degradation of the functional surfaces of high-added-value components. Particularly, metal matrix composites (MMC) are known to mitigate friction efficiently. However, the bonding strength of MMCs severely limits their durability. Hence, it is not sufficient to focus on wear performance. In this work, the flexural strength and interfacial bonding of Stellite 6/WC MMCs produced by Laser Directed Energy Deposition were investigated. The manufactured coatings exhibited a strong bond to the substrate regardless of the WC content, as no delamination was observed. Additionally, all MMC coatings produced under different processing conditions and with the same composition showed similar elastoplastic behaviour, while specimens containing a higher WC% failed prematurely. This was ascribed to the local embrittlement of the reaction layer surrounding the WC particles, which were found to be crack initiation sites.Authors would like to acknowledge the Basque Government (Eusko Jaurlaritza) in call IT 1573-22 for the financial support of the research group

Thermomechanical analysis of additively manufactured bimetallic tools for hot stamping

A comparison between a conventional AISI H13 hot stamping tool and a bimetallic tool consisting of an AISI 1045 core and a laser-deposited AISI H13 coating is performed. In order to analyze the performance of bimetallic tools, the material compatibility and quality of the coating are analyzed. Besides, the mechanical properties are evaluated and compared with those of the conventional tool, obtaining mechanically equivalent results. Nevertheless, the real conductivity of the laser deposited AISI H13 is found to be 16 % lower than the theoretical value. Hence, a thermal model of the hot stamping process is developed, and the performance of various coating thicknesses is evaluated. Results show that, in the present case study, an AISI 1045 tool with a 1 mm AISI H13 coating ensures the mechanical properties and reduces the cycle time by 44.5 % when compared to a conventional AISI H13 tool.e authors gratefully acknowledge the financial support for this study from the European Union, through the H2020-FoF132016 PARADDISE project (contract number 723440) and from the Spanish Ministry of Economy and Competitiveness for the support on the DPI2016-79889-R INTEGRADDI project

The Effect of the Laser Incidence Angle in the Surface of L-PBF Processed Parts

The manufacture of multiple parts on the same platform is a common procedure in the Laser Powder Bed Fusion (L-PBF) process. The main advantage is that the entire working volume of the machine is used and a greater number of parts are obtained, thus reducing inert gas volume, raw powder consumption, and manufacturing time. However, one of the main disadvantages of this method is the possible differences in quality and surface finish of the different parts manufactured on the same platform depending on their orientation and location, even if they are manufactured with the same process parameters and raw powder material. Throughout this study, these surface quality differences were studied, focusing on the variation of the surface roughness with the angle of incidence of the laser with respect to the platform. First, a characterization test was carried out to understand the behavior of the laser in the different areas of the platform. Then, the surface roughness, microstructure, and minimum thickness of vertical walls were analyzed in the different areas of the platform. These results were related to the angle of incidence of the laser. As it was observed, the laser is completely perpendicular only in the center of the platform, whilst at the border of the platform, due to the incidence angle, it melts an elliptical area, which affects the roughness and thickness of the manufactured part. The roughness increases from values of Sa = 5.489 μm in the central part of the platform to 27.473 μm at the outer borders while the thickness of the manufactured thin walls increases around 40 μm.This research was funded by the Spanish Ministry of Industry and Competitiveness under the CDTI JANO project and by Basque Government (Eusko Jaurlaritza) under the ELKARTEK Program, QUALYFAM project, Grant No. KK-2020/00042

Functionally Graded AISI 316L and AISI H13 Manufactured by L-DED for Die and Mould Applications

Tooling in the die and mould industry is subjected to high-wear and high-temperature environments, which often leads to the premature failure of this high-added-value tooling. When severe damage occurs, an alternative to replacing the whole component consists of the repair by laser-directed energy deposition (L-DED). For that end, intermediate layers are commonly employed as buffer material, where introducing a functionally graded material (FGM) might be beneficial to avoid material incompatibilities and improve the overall performance of the tooling. In the present work, an FGM composed of gradient AISI 316L to AISI H13 has been manufactured, and its microstructure and hardness analysed. Firstly, cracking owing to the formation of brittle intermediate phases has been detected. Secondly, an increase of the hardness and a decrease of the corrosion resistance has been observed when transitioning from AISI 316L to AISI H13. Thirdly, despite the FGM composition evolving linearly, nonlinear material properties such as hardness and corrosion have been observed, which are conditioned by the microstructure formed during the L‑DED process and the nonlinear influence of the composition of steel on such properties. Consequently, nonlinear compositional gradients are recommended if linear mechanical properties are to be obtained in the case of steel FGMs.This research was funded by the Basque Government (Eusko Jaurlaritza) under the ELKARTEK Program, QUALYFAM project, grant number KK-2020/00042 and Spanish Ministry of Industry and Competitiveness under the PID2019-109220RB-I00 ALASURF project