Unlike traditional manufacturing, metal 3D printing does not require cutting, stamping, casting or machining. This technology can produce a wide range of metal alloys for the most demanding applications.
Metal powder processes like SLM and DMLS use lasers to scan and selectively fuse metal powder particles, constructing parts layer-by-layer. These technologies can produce impossible-to-make features such as conformal cooling channels and internal lattice structures.
CAD Modeling
Metal 3D printing (also known as powder bed fusion or direct metal laser sintering, DMLS) is used to build complex functional metal parts from CAD designs. The technology offers limitless design freedom and overcomes limitations of traditional subtractive and casting technologies. Unlike plastics, most metals have high mechanical properties, including strength and fatigue resistance. For instance, nickel-based alloys, such as Inconel and Hastelloy, have great corrosion resistance, are stable at high temperatures, and can withstand strong shocks.
The process uses a high precision laser to heat and sinter metal powder particles, layer by layer. This creates a solid metal object that has the same geometry as the original CAD model. The layer thicknesses can be varied, which allows for the production of complex internal shapes and lattices. In addition, multiple materials can be printed at the same time. Among the most popular are titanium, aluminum and stainless steel.
When it comes to post-processing, it’s also important to consider what kind of finish the part will require. Typical finishing work can include sanding, grinding, cutting, drilling and filing. For metals, these steps can take up to 50% of the total build time. To minimize the amount of time needed for finishing, engineers should avoid using rough surfaces on their designs. In addition, they should save any complicated geometries for interior areas or places that are not cosmetically important. This will allow for the most efficient processing and reduce post-processing time and costs.
Support Structures
Support structures serve a number of purposes for 3D metal printing. They provide stability for overhanging sections of a part and they help to prevent distortion during the print process by absorbing and dispersing excess heat. However, support structures can also limit design flexibility and require a significant amount of time and material to generate and remove.
Powder bed fusion technologies such as selective laser sintering (SLS) and binder jetting require support structures to anchor the printed part to the base plate. They also help to minimize residual stress by drawing heat away from the printed surface, which can lead to cracking, sagging, delamination and warping.
In dual extrusion printers, which are used for polymer-based 3D printing, soluble support materials can be used to quickly dissolve the supports once the printing is complete. Alternatively, the supports can be removed manually or using cutting tools. In the case of metal parts, support removal can be more difficult than for polymer-based printing and may leave marks on the surface of the finished product.
As a result, designers need to plan and build for this additional step in the manufacturing process, taking into account the cost of the soluble support material as well as the labor needed to remove it. It is also important to consider the aesthetics of a finished part as it may be impacted by the presence of support marks or lines. In these cases, it is often necessary to sand or polish the surfaces of a finished part to improve its appearance.
Sintering
When metal powders are deposited onto a build platform, a laser is used to selectively sinter the particles into a solid part. This allows for the creation of complex, functional metal parts that cannot be built using traditional subtractive manufacturing or casting technologies.
While the technology itself is relatively new, engineers already have a number of engineering principles they can use to optimize the process. The first is to avoid overhangs, which can impede the printing process and lead to failure in the sintering stage. The second is to use a high-quality metal powder that offers good sinterability, meaning the particles easily bond together.
This step is important because it ensures that the resulting part will have the physical properties required for its application. It also helps the resulting part meet or exceed material standards established by the American Society for Testing and Materials (ASTM) and Metal Powder Industries Federation (3DPIF).
The sintering step is usually performed in a sintering oven, which can be used to heat and temper the part as it sinters. This helps ensure that the part is sufficiently strong and resistant to cracking.
One technology that has helped open up this process to a wider range of users is Rapidia’s Desktop Metal printing system. It uses a binding agent that is solvent-free, allowing it to produce more intricate parts than other bound metal processing technologies. It also eliminates the debinding and sintering stages, which makes it faster and more cost-effective than other metal AM processes. In addition, the company’s Live Sinter software simulates the complex deformation and compounding forces that a part experiences during printing and then adjusts the geometry accordingly. This eliminates the guesswork involved with sintering and sintering, which can often be a challenge for first-time sinterers.
Melting
Metal printing uses a powder process to build up three-dimensional parts. The powders used vary, depending on the processes and applications. Some print with melted material (like direct metal laser melting or Selective Laser Melting), while others use powdered materials with thermoplastic or wax binders to create the parts (such as injection molding or laminated object manufacturing). The process of printing involves laying down layers of powder, sintering them together, and then removing the support structures.
The sintering process for printing metal is extremely fast, which means that the metal solidifies in a matter of seconds. That speed enables the printing of parts with very complex geometries and features that would be impossible to fabricate through traditional methods. This makes metal 3D printing a very valuable tool for making prototypes and facilitating the creation of production tools.
Researchers have long been seeking to understand the formation of these stress fractures in metal 3D-printed parts. Fortunately, advances in particle accelerator technology have enabled them to peer into the internal structure of steel as it melts and solidifies during printing. Their results, published in Acta Materialia, offer a new computational tool for metal printers and may lead to improvements in the strength and durability of printed parts.
Because of their low melting points, metals are often printed with the aid of a support structure that forms a lattice pattern across the top surface. This structure anchors the printed part to the base plate, prevents warping, and acts as a heat sink. But these support structures can be costly in terms of both the time it takes to make the part and the material wasted on them.
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