The call for 3D printing, also known as additive manufacturing (AM), is on the rise because it brings flexibility, customization, speed and reduced costs to manufacturing. 3D printing can produce objects from a variety of materials including photo-polymeric resins, extruded filament, powders of plastics and pure metals and alloys.
Metal additive processes such as metal powder bed fusion and directed energy deposition are potentially capable of producing high-quality, functional and load bearing parts from a variety of metallic powder materials.
What is metal 3D printing?
Two common metal additive manufacturing processes are Selective Laser Melting (SLM) and Direct Metal Laser Sintering (DMLS) that belong to the powder bed fusion 3D printing category. The two technologies have a lot in common: both use a laser to scan to build a part layer-by-layer by selectively fusing or melting the metal powder particles, therefore bonding them together. The materials used in both processes are called powder metals.
The differences between SLM and DMLS come down to the fundamentals of the particle bonding process (and also patents): SLM uses metal powders with a single melting temperature and fully melts the particles, while in DMLS the powder is composed of materials with variable melting points that fuse on a molecular level at elevated temperatures.
How does additive manufacturing compare to traditional manufacturing?
The powder bed fusion process in additive manufacturing allows for intricate and complex designs. It also makes possible combining multiple parts into one complex design, reducing manufacturing, assembly and machining costs. Thin-walled components, fine meshes and integrated conformal cooling channels are all possible. Traditional manufacturing methods require tooling that is only cost-effective when the economies of scale are realized.
Since AM processes allow for direct manufacturing from CAD files, it is possible to economically produce customized components and smaller quantities of parts. Designers can also optimize the use of valuable build materials to simultaneously reduce weight, retain structural strength and cut costs. Traditional manufacturing methods also often require time-consuming subtractive machining that generates excess waste. However, when traditional manufacturing methods are well-suited to certain aspects of production, it is possible to simply integrate AM into the process where it is particularly advantageous. In numerous applications, 3D printing reduces the number of steps from object design to finished product. This often cuts the time-to-market, enhancing an enterpriseâ€™s competitive position.
What types of metal powders are used in what situations?
SLM and DMLS can produce parts from a large range of metals and metal alloys including:
- Stainless steel
- Cobalt chrome
These materials cover the needs of most industrial applications, from aerospace to medical.
Whatâ€™s important to know when purchasing powdered metals
High-quality metal powder is very important for successful powder bed fusion. In such processes, build material flow rates are optimized through the use of closely packed, spherical metal particles of similar size. Consistent metal particles also optimize object density.
ASTM International continues to work toward standardizing specifications for AM metal powders.
Powder Metals are typically spherical shaped to ensure good flow/coating ability and a high packing density Particle size is usually below 50 Î¼m or 150 Î¼m depending on machine type and surface finish or productivity required, particle size distribution tailored to the application and properties, controlled chemical composition and gas content.
For optimum performance, metal powders are precisely fabricated via gas atomization or plasma atomization. In the gas atomization process, molten metal shooting from a nozzle is dispersed and solidified by a stream of nitrogen or argon gas. Spherical metal particles drop to the bottom of the enclosure where they are subsequently collected.
Although less commonly used, plasma atomization is used with reactive metals that have very high melting points, like titanium alloys. Wire filament is melted with a plasma torch, resulting in the production of spherical particles as the molten metal cools.
See our Guide for Understanding Powdered Metals and Their Uses. Or, for assistance in choosing the right powder metal for your application, contact us for a consultation.