TCT interview with Florian Bechmann, Concept Laser GmbH

...continued from The TCT Magazine, Vol. 18, Issue 4, page 39.


TCT: Looking back to reproducibility of process, can you reassure readers about your statements?

Dr. Bechmann: Our quality assurance system makes parts assembly transparent by monitoring the construction process in real-time. We thereby tackle all process components: melt pool, documentation, process gas, powder and temperature. A key element here is the real-time monitoring of the melt pool. In practice, for us this means the monitoring of the melt pool at very high sampling rates. As SLM/LaserCUSING is a micro-welding process in a confined space (track width approx. 100 µm with a layer height of approx. 20–50 µm), a high resolution is required. The melt pool module follows the running construction process with several thousand images per second. It analyses the relevant melt track data in real-time. These are recorded and evaluated by our own software. Another key element is the powder module. It is important for us that the powder module operates in isolation from the production plant. This means that the sieving of the metal powder can take place in parallel to the construction process. In addition, it allows high throughput rates with a fine sieve mesh width of down to less than 50 µm. The powder module may be rendered inert; i.e. it contains is a protective gaseous atmosphere which excludes oxygen. As a rule we use the inert gas argon, which ensures the constant chemical composition of the metal powder.
These are our quality criteria, which are reflected in the quality of the component, surface and component structure. Finally, a comprehensive documentation of the process is intended to bring us closer to the aim of zero defect manufacturing. Currently, we are also working on monitoring of the volumetric flow rate in the process gas module. We already have constant monitoring and regulation of the oxygen concentration in the process gas. The regulation of the volumetric flow rate is our current development task. The eventual aim of these measures is a self-regulating process of the highest quality, with high degrees of freedom in the geometry and assured economic efficiency.


TCT: What are your opinions on surface quality? What efforts are you making in this area?

Dr. Bechmann: We are making great strides in terms of surface finish. The once proverbial rugosity of the SLM/LaserCUSING component surface is no where near as pronounced as in the past. For precision parts, today we can eclipse casting with our microwelding process as far as component quality and, in particular, density and surface finish are concerned. We can also overcome their tendency to form blow-holes and separate, as we are working with a very fine build-up of layer using a laser.


TCT: How are you developing the mechanical properties of your SLM parts?

Dr. Bechmann: For this Concept Laser have developed a patented process under the name ‘Island principle’. Stochastically selected, the segments of a layer (so-called ‘islands’) are processed successively. We melt the metal powder in one segment and then move off to a distant segment, thereby ensuring thermal equilibration on the surface. In the melting process, this strategy guarantees a significant reduction in stresses within the component.


TCT: Price is king in manufacturing, and AM is still regarded by many as being prohibitively expensive. Where do you see the balance between SLM and traditional technologies now and in the future on price?

Dr. Bechmann: There is a limit to established industrial processes when considering die casting. We have already been able to free ourselves from prototype construction and move in the direction of small series production. We are increasingly more capable of mass production under the catchphrase ‘mass customization’. For us the boundary is now moving to higher numbers of units. The reason for this lies in the possible speed of component construction today using more powerful lasers. Factors such as cheaper powder prices or the simultaneous and multiple construction of several components in one process room, also come into play. Undoubtedly, the batch size is always the cut-off point for die casting. The unit costs define the choice between conventional manufacture as opposed to toolless, generative production – always considering factors such as quality required, mechanical strength and functionality. Our big chances lie in these three final points, with additional cost degression and further developments of the SLM/LaserCUSING process technology to be undertaken. We have already been able to make that choice swing in our favour in the mass production of dental crowns and bridges.


TCT: What developments do you see in the future?

Dr. Bechmann: We really are broadening our horizons. SLM/LaserCUSING still offers plenty of potential. On the one hand, I see this in the increasing performance of the laser. 200 W lasers are fitted in our machines as standard. However, we have already successfully launched the first installed systems with 400 W fibre lasers onto the market. We are assuming that the trend towards more powerful lasers will continue and promise ourselves additional visible improvements in construction rates over the next few years. Materials are another factor. Let’s consider applications within implant technology. High-purity titanium alloys are used here, which meet the strict requirements of the ASTM standard for surgical implants. High performance alloys will be in greater demand in aeronautical and astronautical engineering in the future. Our partnership with the DLR (German Aerospace Centre), that already uses our machines in its technical laboratories, indicates that things are moving in this direction. I am also thinking about precious metal applications, such as gold or silver, for the dental technology or jewellery industry. It is precisely these sectors that we will, in future, be able to supply products to that are capable of producing truly unique pieces. SLM/LaserCUSING is predestined for producing unique pieces. From my point of view, the bottom line would be that SLM/LaserCUSING is increasingly becoming a materials and product development platform.