Materials and processes is often a freshman level course in college. With the expansion of new technology, some engineers might find a refresher course that includes additive manufacturing, also called 3D printing, valuable. It can be difficult when looking for new solutions and become inundated with new technology.
This article will mention some of the difference between metal 3D printing processes and selection criteria to help understand this technology better. This does not cover all the processes. There is a lot of great research happening in this area, but the following introduces some of the more common processes.
First, I always suggest checking with a professional, and specifically one that works with multiple processes. For example, if a service bureau only has electron beam melting (EBM), it might say that it can processes soft metals like magnesium (Mg)or zinc (Zn) alloys. While it is possible, the high temperatures of EBM might not be the best for your specific application. Mg/Zn may even vaporize at EBM processing temperatures. Basically, a company that only offers EBM will find a way to make the process work, but it might not be the best solution.
When it comes to metal 3D printing, the most used technology is powder bed process. There are multiple powder bed processes such as binder jetting (BDJ), selective laser melting (SLM), and EBM. Other processes might say selective laser sintering, but they may not be the same as selective laser melting. Sintering normally uses a lower power laser. The energy is enough to compact, but not melt the powder. This might also be a term that is lost in hype and marketing, so it is important to understand whether a company offers sintering, melting, or both.
Metal sintering, also called direct metal laser sintering (DMLS) can reduce internal stresses cause by excessive heat. Without the thermal stresses caused by some of the other processes, including 3D printing and traditional, DMLS parts are capable of operating in the aerospace and automotive industry for applications that may see high stresses. DMLS can also eliminate post-thermal processing such as annealing. The strength, elongation, and hardness charts show an idea of common materials and material properties associated with DMLS.
It can handle metals and alloys, including aluminum, copper, iron, nickel, and cobalt-based alloys. In addition, BDJ can process ceramics, including glass, sand, and graphite. BDJ is said to work with any powder that allows for color printing. For applications BDJ is often not suitable for structural applications due to porosity that may occur from the conventional sintering process. Sintering also means green parts that are not near net tolerance. There is software the will compensate for shrinkage during processing, and scale green parts accordingly. However, it is imperative that a designer understand whether software they are using will scale for shrinkage or not. Below are some further pros and cons for BDJ.