Metal 3D printing is advancing in both technological and print speed fronts. These advancements mean the process is opening up new applications. However, it has never been easy to get grips with all the available technologies and integrating them into the existing workflows. This guide is meant to help you get a better understanding of metal 3D printing, ranging from the available technologies to the benefits and limitations.
Metal 3D Printing: The Technologies
Many metal 3D printing technologies are currently available on the market. As much as all of them have unique advantages and disadvantages, they all follow the fundamental metal 3D printing principle or creating parts layer after the other.
Commonly used metal 3D printing technologies include:
- Powder Bed Fusion
- Direct Energy Deposition
- Metal Binder Jetting
- Ultrasonic Sheet Lamination
Powder Bed Fusion 3D Metal Printing Technologies
Metal powder bed fusion is the most advanced and well-established of all metal 3D printing technologies. With this technology, there is an even distribution of layers of powdered metal onto the build platform of the machine. An energy source, which can either be laser or electron beam, is then used to fuse the layers. Tow crucial metal 3D printing processes fall under the Powder Bed Fusion category, and they are:
- Selective Laser Melting (SLM) or Direct Metal Laser Sintering (DMLS)
- Electron Beam Melting (EBM)
Selective Laser Melting /Direct Metal Laser Sintering
Selective laser sintering and direct metal laser sintering are the most predominant metal 3D printing technologies. Direct metal laser sintering has the vastest installed base globally. Both selective laser sintering and direct metal laser sintering use a powerful, fine-tuned laser to apply layers of metal powder selectively. Metal particles are then fused to create a complete part.
A build chamber that is filled with inert gas, for instance, argon, is an essential requirement for both metal 3D printing processes. This arrangement helps in preventing the contamination of the metal powder when it comes into contact with oxygen. It also helps in maintaining the right temperature during the metal printing process.
Electron Beam Melting
Electron beam melting (EBM) is another metal 3D printing process in the Powder Bed Fusion category. Electron beam melting works in the same way as selective laser sintering in the sense that metal powders are melted to create complete metal parts. Electron beam melting happens in a vacuum environment to prevent contamination of the metal powder through oxidation.
The most notable difference between selective laser sintering or direct metal laser sintering and electron beam melting is the source of energy used in the process of printing metal parts. Instead of a laser, electron beam melting uses high-powered electron beams to melt the layers of metal powder.
Additionally, metal parts made through electron beam melting tend to lack detailed precision compared to metal parts made through selective laser sintering or direct metal laser sintering. This is mainly because, in selective laser sintering, the thickness of every layer is thinner than in electron beam melting. Therefore, it is easier to achieve more precision and accuracy in selective laser sintering and direct metal laser sintering compared to electron beam melting.
Electron beam melting is often used with high-temperature metal superalloys to print metal parts for highly demanding applications such as gas turbines and jet engines. This mainly because electron beams are more powerful compared to laser energy. The metal parts that are formed through electron beam melting are highly dense, making them ideal for applications in the aerospace industry.
Companies looking to invest in the electron beam melting technology should consider the high cost of systems involved. Additionally, the technique relies on electrical charges. Therefore, electron beam melting can only be used with metals that conduct electricity such as titanium and chromium alloys. These are some of the drawbacks of electron beam melting.
All metals parts that are produced through powder bed fusion technology require some form of post-processing, whether you apply selective laser sintering, direct metal laser sintering, or electron beam melting. Post-processing is necessary since it improves the aesthetics of metal parts and their mechanical properties. Additionally, post-processing helps to meet precision in the design of metal parts, which is suitable for more demanding applications.
Direct Energy Deposition
Direct energy deposition is a metal 3D printing technology that works by melting metallic materials using laser energy or electron beam as the parts get deposited through a nozzle found on the build platform. Direct energy deposition has high metal deposition rates. Accordingly, the process can work with metallic materials in either wire or powdery form. This helps in creating highly dense parts with near-net shapes.
In comparison, powder bed fusion processes create smaller components with high accuracy level, while direct energy deposition processes can be used to create large metal parts. For instance, Sciaky’s proprietary Electron Beam Additive Manufacturing (EBAM) is a technology that has been used to create metal parts that are larger than 6M in length.
Direct energy deposition technology is suitable for repairing damaged metal components and parts. For instance, the process can come in handy when repairing spoilt turbine blades, and injection molding tools inserts. These applications would be difficult and nearly impossible when other conventional metal 3D printing technologies are used.
Metal Binder Jetting
Metal Binder Jetting is considered to be one of the most affordable and cost-effective metal 3D printing technology in the market at the moment. The process of producing metal parts using metal binder jetting is almost similar to how ink printing on papers work since the procedure involves the use of a print head. During the process of producing metal parts, the print head moves over the build platform as it deposits droplets of a binding component on the layers of metal powder. This is how the metal particles are fused to produce complete metal parts. The process can be made faster by using multiple print heads.
Metal binder jetting machines can be used to offer the fastest metal printing speed and also produce a large volume of metal parts. Additionally, these machines are more affordable compared to powder-bed systems.
A limitation of metal binder jetting technology is that metal parts produced are often limited in terms of mechanical properties due to the nature of the printing process. Accordingly, these metal parts become highly porous as a result of the binder burning out in the process of printing metal parts, more details click here.
As a result of this limitation, metal parts produced using metal binder jetting technology require a considerable amount of post-processing before they can be used for some demanding applications. Some of the post-processing activities may include metal curing meant to harden the parts, sintering, and bronze infiltration that reduce porosity and improve metal strength.
Ultrasonic Sheet Lamination
Ultrasonic Sheet Lamination is a metal 3D printing technology that requires low temperatures. It is also called a low-temperature hybrid metal additive production process. This technology works by welding thin layers of metals (foils) together using ultrasonic vibrations under high pressure. CNC milling is applied to the method to remove excess materials from the finish parts once the entire metal printing process is complete.
Since this metal 3D printing process happens at low temperatures, it does not melt metal parts. Additionally, Ultrasonic Sheet Lamination technology can be used to fuse dissimilar metal types.
Critical advantages of Ultrasonic Sheet Lamination are that it is cost-effective, has fast printing speed, and can also create parts with fused electronics and sensors from a wide range of metal types.
New metal 3D printing processes
Metal 3D printing technology has seen a rapid revolution with hardware manufacturers continually looking to develop more advanced and cost-effective processes. The trends in this industry are many, and we have compiled some of the newly-developed metal 3D printing technologies that may revolutionize the methods of producing metal parts in terms of speed and cost.
Extrusion-based metal 3D printing
A newer approach in metal 3D printing technology is the production of parts additively through the extrusion of metal filaments. Markforged and Desktop Metal are the two companies that have shown progress by working with this method. The two companies have established their metal 3D printing systems using extrusion-based metal 3D printing technology.
Extrusion-based metal 3D printing works in a way that is closely related to how Fused Deposition Modelling (FDM) works. In both processes, the metal filament is heated and extruded through a nozzle to create metal parts layer by layer.
However, metal extrusion uses powder metal filaments or pellets encased in plastic binders as opposed to fused deposition modeling, which uses plastic threads.
Any metal part that is produced using extrusion-based metal 3D printing technology remains in the “green state” until it undergoes post-processing. Some post-processing activities include de-binding to remove the remaining plastic components through burning out and sintering to fuse the metal particles.
Extrusion-based metal 3D printing is considered to be one of the most cost-effective metal additive manufacturing methods. This can be attributed to the fact that the process uses metal injection molding (MIM) materials that are considerably more affordable compared to metal powders used in powder bed metal 3D printing processes.
Material Jetting is a process that uses inkjet printing type of technology in which print heads are used to deposit photoreactive components in the liquid form layer by layer onto the build platform. Material jetting has been used in applications such as prototyping technology to create full-color plastic models with a lot of precision.
An Israeli company, XJet, has tried successfully to apply material jetting as a technology for metal 3D printing. The company developed an ink-jetting technique that can be used for metals to achieve a high level of accuracy and detailed finish.
The XJet’s NanoParticle Jetting (NPJ) technology applies metal inks suspended in a liquid formula using print heads. The entire process takes place in a heated chamber, where the hot plate evaporates the liquid formula, leaving only the metal particles behind. The metal inks are deposited onto a hot building tray. The metal particles come with some small coating of a bonding agent, which allows them to be fused in all three dimensions.
Once the printing process is complete, metal parts are moved to an oven where they are sintered. The material jetting technology can be used for functional prototyping and on-demand manufacturing of small and mid-sized metal parts.
Metal Jet (HP)
HP first came into the limelight by moving the metal 3D printing market in 2016 when the company launched the polymer multi-jet fusion system. By 2018, the company had taken its binder jetting technology to new levels by announcing the new metal 3D printing system called the Metal Jet.
The metal jet system is based on a binder jetting process by HP. The process has been enhanced to make metal 3D printing faster and more affordable. The process works similarly to other binder jetting machines. However, the system by HP uses a proprietary binder that is developed by the company’s Latex Ink Technology.
The new binder formula by HP is faster, more cost-effective, and straightforward when used in sintering metal parts. Additionally, Metal Jet applies Metal Injection Moulding (MIM) powders and can be used to manufacture isotropic metal parts.
A vital feature of the Metal Jet technology is that it has many print heads, making it 50 times faster and more productive compared to other binders and laser sintering machines available in the market today.
Joule Printing (Digital Alloys)
The commercial release is scheduled to be late in the year (2020). However, the Joule Printing technology from Digital Alloys is another new metal 3D printing technology that is worth looking at. The process is a high-speed metal 3D printing technology that uses metal wires instead of metal powder.
The metal wire (filament) is placed inside a precision motion system using a precision wire feed. Once the metal wire is in position, some current is passed through it and the print bed. The metal wire is then melted using the current while the print heads move, fusing metal droplets to form a complete metal part.
Metal 3D printing technologies are vast. You need to identify the one that works for based on the mechanical property of metal parts you need. Accordingly, you can consider the cost and speed of metal 3D printing systems to ensure that you are not inconvenienced in the process.
Lastly, for any Metal 3D service needs, do not hesitate to contact us.