Introduction
Addressing Challenges in Metal Additive Manufacturing
Laser-based additive manufacturing (AM) technologies produce components of varying sizes, from millimeters (PBF-LB/M) to meters (DED-LB/M). Regardless of scale, the local temperature distribution and melt-pool dynamics significantly impact the mechanical properties of the final part. Unfavorable temperature distributions lead to process instabilities, manifesting in issues like melt ejection, spatter, and defects such as delamination and porosity. Key issues include:
Inadequate Control of Mechanical Properties
An inappropriate energy input causes defects such as lack of fusion or porosity affecting not only the density but also the microstructure and therefore the variability of mechanical properties of the final part.
Necessity of Post-Processing
Time-consuming post-processing operations are necessary to improve dimensional and surface quality (e.g. surface roughness) of the final part.
High cost per part due to low productivity
Despite the ability to manufacture complex part geometries the costs per part are high due to limited process speeds.
Limited Material Portfolio
The portfolio of printable metal alloys is limited due to inherent material failure such as cracking causes by inappropriate thermal conditions during the printing job.
The root cause of these challenges lies in the steep thermal gradients and high cooling rates associated with traditional laser material processes. The inability to dynamically and precisely shape the laser energy input in both time and space, leaves manufacturers constrained in their ability to meet diverse material and design requirements. This whitepaper introduces dynamic beam shaping to additive manufacturing applications and demonstrates the potential of coherent beam combining to transform the industry.
Control of energy input in space and time required to minimize process-related defects (e.g. lack of fusion, porosity, internal stresses) and gain control of the process outcome (e.g. microstructure, surface roughness).
Dynamic Beam Shaping for Superior Results
Civan’s Dynamic Beam Laser (DBL) technology offers transformative capabilities through dynamic beam shaping, enabling real-time modulation of the laser energy distribution. Two key applications where DBL delivers significant advantages in laser-based additive manufacturing are demonstrated in the following:
PBF-LB/M Increase in Productivity with DBL
In single track experiments with light-weight titanium alloy Ti6Al4V, the influence of different laser beam shapes on the weld seam geometry in PBF-LB/M was investigated.. The experiments were performed under constant process conditions employing a laser power of 1000 W, a scan velocity of 1 m/s and a powder layer thickness of 50 µm. A ring-shaped beam profile and a spiral-shaped beam profile were compared to a standard Gaussian beam profile. The results show a significant improvement in weld seam width for the advanced beam shapes as visualized in Fig. 2:
The ring-shaped beam profile increased the weld seam width by 23% compared to the standard Gaussian beam.
The spiral beam shape achieved an even greater increase of the weld seam width by 134% compared to the standard Gaussian beam.
Why does this matter? A wider weld seam allows the use of a higher hatch distance between consecutive weld tracks during the printing process. This reduces the number of tracks required to cover the same area, leading to (1) faster printing times and consequently (2) an increase in productivity. Further, by dynamically switching between beam shapes, such as ring or spiral intensity profiles, within a millisecond range, the technology additionally allows for flexible adjustment of the weld seam geometry during the printing process. This is of high relevance for the printability of parts that combine small, precise structures with large, expansive areas. This real-time adaptability ensures optimal weld seam performance based on the part's geometrical conditions.
DED-LB/M: Control of Melt Pool Geometry with DBL
Unlike PBF-LB/M, which relies on melting predeposited powder layers, DED-LB/M involves the direct deposition of powder or wire material into the molten pool to generate a volumetric build-up. To understand how dynamic beam shaping influences the DED-LB/M-process, the performance of two beam shapes – snowflake and hourglass – were compared. Whereas the snowflake beam shape resembles a static energy input approach, the use of the hourglass beam shape relies on the dynamic change of the energy input between the leading and trailing edge of the melt pool. The experiments were performed under constant process conditions using a laser power of 500 W, a feed rate of 400 mm/min and a powder mass flow of 3 g/min of hot working steel powder AlSlH11.
This highlights the effectiveness of dynamic beam shaping in enhancing productivity by allowing precise control over melt pool geometry in DED-LB/M.
Potential of DBL for Metal AM
Summarizing the first results in the context of additive manufacturing, the following potentials of DBL can be derived:
Enhancing productivity:
Combining high-speed production capabilities by adapting the beam profile to match part geometry, enabling higher feed rates.
Reducing post-processing time.
Steering the unit cell of additive manufacturing::
Microstructure control: Adjustment of microstructural and resulting mechanical properties through adaption of local cooling rates.
Enhancing printability of hard-to-print materials: For example, additive manufacturing of high-strength materials like nickel-based superalloys while minimizing the risk of cracking by influencing the solidification process.
Unlocking New Possibilities in Metal AM
DBL technology represents a paradigm shift in metal additive manufacturing. By enabling real-time dynamic beam shaping, this innovation addresses longstanding challenges in microstructure control, part quality, and productivity. Investing in DBL lasers empowers manufacturers to push the boundaries of design and material performance, ensuring a competitive edge in a rapidly evolving industry. With its adaptability and precision, this technology is poised to redefine the future of additive manufacturing.