Additive manufacturing simulation
Additive manufacturing has shifted over the last decade from being used primarily as a prototyping method to taking a foothold in production processes. In order to industrialize, methods such as selective laser melting must overcome conditions that limit quality and productivity. Bosch Research used high-fidelity computational fluid dynamics (CFD) simulations to do just that.
What is additive manufacturing?
Traditionally, parts are manufactured subtractively – in other words, by carving out a final design from a bigger block of material. Additive manufacturing (AM), on the contrary, builds a part by adding layers of material in a precise way to create it. There are many processes that comprise additive manufacturing – one widely adopted by industry for metal part production is selective laser melting (SLM).
Additive manufacturing technologies are not yet industrialized on the same scale as traditional methods, but they offer some key advantages.
SLM, for example, enables the production of parts with high resolution, complexity, and density, from a variety of metal alloys. Part design files can also be optimized for functionality and manufacturability far beyond subtractively manufactured designs.
Complex physical challenges must be overcome in order to further industrialize SLM, however.
3D Printing – a common term for additive manufacturing, describing a variety of processes in which material is layered under computer control to create a three-dimensional object.
Clearing the laser’s path
The rapidly moving laser in SLM melts metal powder to create the layers of a part in precise detail. A lot is happening as the laser moves across the powder. Material is being melted and solidified, heat is being transferred, and the molten metal – or melt pool – contains fluid dynamics and also gives off emissions. These emissions can be the most challenging to handle, and they can interfere with the laser or become embedded in the part and affect its quality. Since these emissions can’t be avoided, the challenge arises: How can we control their removal and ensure quality manufacturing?
Computational fluid dynamics offer solutions
Removing emissions during the SLM process is achieved by using a gas flow system. It must be done carefully, however. If gas is blown at a high velocity, it will disrupt the metal powder waiting to be melted. A precise gas velocity and flow field must be found that will effectively remove emissions but also not disturb the metal powder bed.
Enter high-fidelity computational fluid dynamics (CFD) simulations. Bosch Research simulated byproducts of the melting process to create realistic conditions inside the process chamber. A gas flow system was then simulated to design a system that overcomes the manufacturing challenge.
The redesigned gas flow system enables 99 percent of emissions to be removed without disturbing the powder bed. It increases quality, reduces cost and broadens the usable part design space. That in turn means it is possible to manufacture quality parts with better functionality, lower weight, and customizations in an economic way.
Additive manufacturing also carries implications for sustainability. It improves energy efficiency by enabling the production of part designs that otherwise today would require assembly, reducing inventory and logistics, and consuming lower energy during production. The high material yield of AM processes also contributes to the sustainability of the manufacturing method.
Additive manufacturing processes face a number of significant challenges as they industrialize. Emissions in the SLM process can lead to poor quality parts. Bosch Research used high-fidelity CFD simulation to design a system for excellent control of the emissions and improve product quality.