The powder must be perfectly shaped in order to hold an even surface. A super-thin layer of steel powder is spread out with a roller. Then, a printer head places tiny drops of glue on the areas of the layer that are part of the design.

The Technology of 3D Metal Printing
The Technology of 3D Metal Printing

Len Calderone for |

3D metal printing is additive manufacturing, which is a technology that produces three-dimensional parts layer by layer from metal. The method relies on a digital data file being transmitted to a machine that then builds the component. Metal additive manufacturing produces complex parts without the design constraints of traditional manufacturing methods.

A few years ago, metal components could not have been made using 3D printing. They can now be manufactured to a high-criteria using a wide range of metal powders. 3D metal manufacturing is no longer exclusively a prototyping technology. It is now being used for the production of components for the most demanding functions.

In traditional manufacturing, making metal parts is a wasteful process. When aircraft manufacturers make metal parts, as much as 90% of the material is cut away. Using the 3D process, less energy is used and waste is reduced to a minimum. Finished 3D printed products can be up to 60% lighter than their machined counterparts.

Most powder-bed based additive manufacturing systems use a powder deposition method entailing a coating mechanism to spread a powder layer onto a substrate plate and a powder reservoir. Once the powder layer is dispersed, a 2D slice is bound together (3D printing). An energy beam can also be directed to the powder bed to melt the powder.

GKN Powder Metallurgy

Direct process powder bed systems are branded as laser melting processes and are available under different trade names such as Selective Laser Melting (SLM), Laser Cusing and Direct Metal Laser Sintering (DMLS). The requirements of the user will decide on the choice of machine with the type of laser unit, powder handling and build chamber being some of the foremost features of the system to take into account.

There is a variety of metal material that is available for metal 3D systems. The most common materials used are stainless steel, aluminum, nickel, cobalt-chrome and titanium alloys. Other materials are tool steels, nichol based alloys, precious metal alloys, and copper alloys. When deciding on a material, properties such as tensile strength, hardness and elongation are important. Because there is a wide variety of material, the right material for a project can be easily factored in the specification of a product.

3D metal printing does not include any filaments. Instead, it is based on a very fine steel powder. The powder used by 3D printers can’t just be any kind of powder, since it will be used for ultra-thin printing layers.  The powder must be perfectly shaped in order to hold an even surface. A super-thin layer of steel powder is spread out with a roller. Then, a printer head places tiny drops of glue on the areas of the layer that are part of the design. The layer is then dried using powerful overhead heaters. The 3D printer will continue to spread out one layer of powder after another, and the printer head will systematically glue the correct spots of each layer together.

From tooling inserts with cooling channels to lightweight assemblies for aerospace, any objective that involves intricate metal parts can benefit from metal 3D printing. Some of the popular applications for metal 3D manufacturing are fully functional prototypes, production tools, mold and insert tooling, rigid housings, ductwork, spare parts, heat exchangers and heatsinks.

The car industry has been the most active industry, investing into additive manufacturing for both prototypes and mass-produced parts. Car companies are improving their prototypes and are starting to mass produce more of their parts and specific tools.

Weight is a vital concern for the aeronautics and aerospace industry. By using metal 3D printing, Aerospace companies can use the same materials as they do with traditional methods. This is important for the industry since they have specific materials that must withstand the conditions of flight. As an example, 3D printed titanium has the same mechanical characteristics of strength, weight and sturdiness of forged titanium. It is imperative that the industry have lightweight materials like aluminum or strong and resistant materials like titanium to build specific parts for spacecraft or engines.

3D metal printing is also making a lot of progress with prosthetics, implants and custom tools, along with bio-printing and organic implants. Doctors and surgeons use 3D printing to make specific instruments. They can design prototypes that will look very close to the final product.

Hand made with Stratasys Mojo 3D printer

The industry is constantly coming out with newer machine capabilities. During the 2018 International Manufacturing Technology Show, HP unveiled the HP Metal Jet, an advanced metal 3D printing technology that is capable of creating production-grade metal parts at a high volume.

HP claims that the new additive manufacturing system will provide users with up to 50 times more productivity at a significantly lower cost compared to other metal 3D printing methods. Similar to HP Multi Jet Fusion technology, HP Metal Jet utilizes voxel-level binder jetting. It offers a print volume of 430 x 320 x 200mm, four times the nozzle redundancy and two times the print bars. This potentially groundbreaking system will use significantly less binder by weight while delivering exceptional productivity and reliability.

There are several advantages to the metal 3D process. Metal printing processes can be used to manufacture complex, custom-made parts that conventional manufacturing methods are unable to produce. Metal 3D printed parts can be optimized to make the most of their application while reducing their weight and the total number of components in a fabrication. Metal 3D printed parts have superior physical properties.  The available variety of material includes difficult to process materials, such as metal superalloys. If a design needs to be changed, the process is effortless and only requires a few buttons to be pressed rather than an expensive and lengthy re-design. The finished products are strong and robust, as the design is made as a continuous piece rather than having multiple welds and joins.

Of course, there are downsides to metal manufacturing. The material and manufacturing costs associated with metal 3D printing is high.  Therefore, some parts can be manufactured more easily using traditional methods. Since exact manufacturing conditions and process controls are essential, the build size of the metal 3D printing systems is limited. Existing 3D designs might not be appropriate for metal 3D printing and may need to be modified.

3D metal printing continues to deliver solutions and growth with no indication of slowing. We can anticipate incremental improvements in the future for printers and materials.

The content & opinions in this article are the author’s and do not necessarily represent the views of ManufacturingTomorrow

Comments (1)

A problem with SLM of metals is the fatigue resistance of the items. Vacuum heat treatments can affect the fatigue performance of components made with Selective Laser Melting technology. Relevant improvements can be obtained on products for the aerospace, medical and automotive sectors, thanks to the vacuum furnace posts‑processes of the components made with additive manufacturing (SLM). I wrote an article on these laboratory results, take a look:

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