Abstract
In this work, the manufacture of thin walls with sharp corners has been optimized by adjusting the limits of a 3-axis cartesian kinematics through data recorded and analyzed off-line, such as axis speed, acceleration and the positioning of the X and Y axes. The study was carried out with two powder materials (SS316L and IN718) using the directed energy deposition process with laser. Thin walls were obtained with 1 mm thickness and only one bead per layer and straight/sharp corners at 90°. After adjusting the in-position parameter G502 for positioning precision on the FAGOR 8070 CNC system, it has been possible to obtain walls with minimal accumulation of material in the corner, and with practically constant layer thickness and height, with a radii of internal curvature between 0.11 and 0.24 mm for two different precision configuration. The best results have been obtained by identifying the correct balance between the decrease in programmed speed and the precision in the positioning to reach the point defined as wall corner, with speed reductions of 29% for a programmed speed of 20 mm/s and 61% for a speed of 40 mm/s. The walls show minimal defects such as residual porosities, and the microstructure is adequate.
Highlights
In Additive Manufacturing (AM) using Directed Energy Deposition (DED) process like Laser Metal Deposition (LMD) it is necessary to keep the process stable in terms of the deposition rate, layer height, and powder efficiency, to avoid imperfections and accumulation of deposited material in certain areas, so it is necessary to adjust process parameters, the drives and the kinematic itself, as well as the powder feeding/delivery system
The laser-based DED process (LB-DED) system used for the LMD process was a 3-axis Cartesian kinematic staequipped with classical computer numerically controlled (CNC) (FAGOR 8070, Spain), see Figure 3, and a solid state tion equipped with classical CNC (FAGOR 8070, Spain), see Figure 3, and a solid laser source Nd-YAG of 3 kW (Trumpf HL-3006D, Germany) in CW mode and wavelength state laser source Nd-YAG of 3 kW (Trumpf HL-3006D, Germany) in CW mode and wave1.06 μm with a spot diameter
The LB-DED system used for the LMD process was a 3-axis Cartesian kinematic station equipped with classical CNC (FAGOR 8070, Spain), see Figure 3, and a solid state laser source Nd-YAG of 3 kW (Trumpf HL-3006D, Germany) in CW mode and wavelength 1.06 μm with a spot diameter of 1.2 mm
Summary
In Additive Manufacturing (AM) using Directed Energy Deposition (DED) process like Laser Metal Deposition (LMD) it is necessary to keep the process stable in terms of the deposition rate, layer height, and powder efficiency, to avoid imperfections and accumulation of deposited material in certain areas, so it is necessary to adjust process parameters, the drives and the kinematic itself, as well as the powder feeding/delivery system. The velocity is decreased in the proximity of the corner or in the change direction point in the trajectory, with a significant variation in their magnitude This variations cause some problems in terms of precision in positioning and in the deposition rate in this zones, the common defect is the over deposition of material and subsequent variation of layer height and track width, affecting the tolerance and can cause loss of geometric tolerances requiring additional post-processing or re-work to achieve a good geometric accuracy on the part. The velocity and acceleration in each axis to generate deposition strategies in 2.5D that correct the problems that currently arise when the deposition trajectory is discontinuous using constant process parameters, that is, where there are abrupt changes of direction or in sharp corners for example. The discontinuous deposition in these trajectories causes uneven deposition, leading to problems of material accumulation, variation in layer height and in some cases defects like lack of fusion and porosity in singular points/zones
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