Abstract
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.
Highlights
Laser metal deposition (LMD) is an additive manufacturing (AM) technique in which a high-power laser melts a filler material in the form of powder or wire, resulting in layer-by-layer manufacturing along a predefined robot or machine path [1].AM allows near net-shape components to be produced for specific sectors in a process which is costly
It is possible to monitor the size of the molten pool and control it by varying input parameters such as power or scanning speed
This paper presents presents a novel methodology to apply local corrections within the layer, based on the dynamic a novel methodology to apply local corrections within the layer, based on the dynamic variation of variation of the scanning speed asofathe function height of each region
Summary
Laser metal deposition (LMD) is an additive manufacturing (AM) technique in which a high-power laser melts a filler material in the form of powder or wire, resulting in layer-by-layer manufacturing along a predefined robot or machine path [1]. By placing a coaxial camera on the deposition head, it is possible to obtain a measurement independent of the deposition direction In this way, it is possible to monitor the size of the molten pool and control it by varying input parameters such as power or scanning speed. Motta and Demir [17] described the issues concerning height deviation using a high-speed vision camera Defects were observed such as stubbing when the working distance was too small and dripping when it was too large. Donadello et al [25] developed a novel system of coaxial camera and laser projection which estimated the height of the piece by triangulation This allowed a measurement of the height during deposition, the accuracy for more complex geometries was not verified.
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