Lightweight, complex mechanical parts can now be “built to order” quickly and automatically, thanks to Additive Manufacturing (AM) technologies.
AM involves building up a structure by adding material to it layer by layer, with each layer being a precise cross section of the structure. Originally used for rapid prototyping, AM – now based on various laser processes - holds promise for series production of critical components, even in applications as demanding as medical devices and aerospace. For example, a recent study proposed providing future long-term space missions with all their medical equipment by means of AM; that way, instead of carrying a fully equipped hospital on board, an AM system would simply produce medical tools as they are needed, from digitally stored templates. Early AM techniques typically involved polymer materials, and the resulting structures would serve as prototypes for visualization, as well as serving as models for casting of molten metal to create molds for production.
In contrast, more modern techniques such as Direct Metal SLM (Selective Laser Melting) are very different: lasers selectively melt metal powders, and the system actually produces functional parts – not just prototypes. Such systems use fiber lasers, with typical powers of several hundred Watts, and often have up to 4 laser beams operating in parallel.
We now run head-on into the big difference between prototypes and serial production. The parts produced must meet the final specs demanded of them for the intended application. Moreover, in contrast to machining (and to some degree molding), in AM the laser system not only determines the shape of the outcome but also its physical properties (strength, surface quality, etc.), making re-work impossible.
Similarly to the semiconductor industry, fabrication 'recipes' are developed for different AM applications involving different AM techniques, precursors (metals and polymers), and part morphology. These recipes include precise laser parameters, such as power, beam shape and size, laser pulse energy, etc.
Reproducibility is the key word here, and that means tight monitoring of the relevant laser parameters. The beam’s power, as well as its focal spot location and shape, must be very stable across the full working field, for every layer, across multiple beams and perhaps multiple systems, over time. And all this for a technology that is complex and still quite new. Not a trivial demand!