In the early days of Optomec, LENS processing typically included laser powers of around 300 to 500 W (LENS, or “laser engineered net shaping”, is a form of DED using a laser heat source to melt the substrate and metal powder that is blown with argon gas into the molten pool). Nowadays with technical advancements in lasers and processing capabilities, coupled with industry’s desire to process larger and larger parts at faster rates, Optomec LENS systems have increased available laser power ranges in their systems from 500 W to 1 kW, 2 kW, and now even 3 kW systems, making higher-powered laser capability available to all users.
As metal additive manufacturing users continue to seek higher laser powers, faster speeds, and improved deposition rates to maximize production they also don’t want to sacrifice the quality of the build. With DED processing including higher laser powers, the challenge becomes more about harnessing that power to enable optimal DED processing. For processing over today’s ranges of laser power it is important to be able to control power density. The ability to vary the focused laser spot size in order to control power density during processing becomes a critical factor.
What happens when laser power is substantially increased, yet the area to which that power is delivered remains constant? As a very simple analogy, the power density increase from the higher-powered laser would be like the difference between water flowing from a showerhead versus a fire hose – one does the job perfectly while the other is overwhelming. In a similar fashion, the lack of variability in power density during DED processing could have a deleterious effect on the part build.
Optomec’s latest white paper looks at power density in more detail and explains how important it is to maintain proper power density for effective DED processing. As illustrated in the white paper, too much increase in power density can take the process from a conduction mode (desirable) into a keyhole mode (undesirable) in which the laser “digs” very deep into the substrate, vaporizing material and essential elements within the chemical composition of the metal being deposited, creating defects, and essentially wreaking havoc on the process by completely changing the process mode. While power densities that create a keyhole effect may be desirable for some process applications (i.e. keyhole welding or laser cutting applications), the DED process is carried out optimally in the conduction mode only.
With increasing laser powers introduced into its systems, Optomec faced the challenge of how to keep a consistent power density and thus a stable conductive process over a wide range of laser powers. Since power density is defined as power applied over a given area (in this case laser power delivered through a laser spot size area focused at the substrate), the obvious answer would be to increase the laser spot size.
The focused laser spot size is determined by three factors: the laser fiber cable diameter, the collimator lens focal length, and the focus lens focal length. If a customer could identify the power range of their application, then a suitable fiber cable size, collimator, and focusing lens could be chosen for the customer for optimal processing at that given laser power.
However, what if a customer wanted to carry out DED processing over a wide range of laser powers? It would not be practical for a customer to have to switch fiber cables or optics in the optics train in order to accommodate a wide range of laser powers.
If this describes you, a customer who wishes to use DED to process a wide range of parts using a wide range of laser powers, fret not! Optomec now has the solution in its new laser deposition head. Optomec’s newly released LDH 3.X is equipped with a variable optics system that can create three discreet focused spot sizes to accommodate for large changes in laser power, all in one deposition head.
The LDH 3.X was designed specifically for optimal DED processing with laser powers from 500 W to 3 kW. With improved channeling for water cooling the head, the LDH 3.X will not overheat while operating at high powers and for long build times as required in industries today. With the LDH 3.X a 0.6 mm focused spot size can be chosen for processing smaller parts or intricate feature building, then switched to 2 or 3 mm focused spot sizes for increased laser powers for larger builds or clad type operations. All applications, all laser powers, all covered with the new LDH 3.X laser deposition head from Optomec.
In addition to advanced water cooling and variable optics for up to three focused spot sizes in one head, the new LDH 3.X also has a quick connect/disconnect nozzle system where different types of processing nozzles (4-tip, coaxial, high overhang, etc.) can quickly and easily be interchanged to optimize printing for all application types.
For more information on Optomec’s new LDH 3.X laser deposition head, visit our contact page or download the white paper today.