A few years ago, 3D printing with metal was only used in industry. That has all changed now that metal 3D printing is now possible on desktop FDM 3D printers and more professional machines, producing high-quality parts at a more affordable price.
△The Forge1 3D printer launched by Raise3D can print metal parts (Source: Raise3D)
Metal 3D printing parts case
Currently, there are about 10 methods on the market for 3D printing metal parts. These methods are roughly divided according to the form of raw materials used and the energy source, such as whether the material is wire, metal powder or metal wire. Some even use metal resins, metal rods, and metal pellets as raw materials, each method producing parts with different properties. In the global 3D printing product library https://product.nanjixiong.com/, more than a dozen types of metal 3D printing technology equipment have been included.
Choosing which metal technology to use takes into account factors such as part detail, shape, size, strength, metal type, cost, print speed and quantity. If analyzed from these aspects, each technology has advantages and disadvantages. Unfortunately, there is no one method that can quickly, cheaply and perfectly 3D print super strong parts, so the choice of which one to use depends on the application needs. technology.
Let’s look at some examples of metal parts
△Parts 3D printed with metal wires like this often require post-processing (Source: BCN3D)
The small steel nozzle above is a wire-printed part. Parts like this are perfectly suited to using metal filament and can be quickly 3D printed on-site in a workshop or office using an affordable FDM 3D printer and then handed over to a third party for post-processing. Overall, the process may only take a few days. Using other manufacturing methods, making this part would be expensive and slow.
△Zenith Tecnica uses GE’s electron beam melting technology to 3D print titanium alloy orthopedic implants (Source: Zenith Tecnica)
These hip and knee implant samples (above) were printed using electron beam melting (EBM). They are intricately constructed using expensive titanium and manufactured to extremely high material quality and tolerances to meet medical implant standards. The EBM 3D printer’s vacuum environment ensures clean and controlled printing conditions, while the high-powered electron beam enables the printer to produce multiple parts per build for high productivity.
△Crane hook printed using WAAM 3D printing technology (the Antarctic Bear website www.nanjixiong.com has also previously reported in detail)
The giant crane hook above was printed using wire arc additive manufacturing (WAAM) and then post-processed. A large and heavy part like this is ideal for using WAAM, as this technology is faster than any traditional metal fabrication method (such as forging or casting) and is just as strong. Additionally, such parts can be produced in factories closer to the point of demand or even on site, such as on an oil rig.
△Cobra Golf launched the 3D printed King Supersport-35 golf putter in 2020, which was 3D printed using HP Multi Jet metal binder jetting technology (Source: Cobra Golf
These golf clubs on Cobra Golf are 3D printed using HP’s metal binder jetting technology. This unique shape is not possible with any other manufacturing technology. With thousands of identical parts required, manufacturers chose binder jetting technology for its speed and high throughput. At the same time, this technology also enables printing with excellent surface finish. Cobra Golf will transfer club manufacturing to a local additive manufacturer in the United States, eliminating the need to manufacture and ship from manufacturing centers in Asia.
△Selective laser melting components from TRUMPF (Source: TRUMPF)
How to choose the metal 3D printing technology that suits you?
As you can see in the image above, not all metal 3D printing technology characteristics are measured the same way, especially when it comes to build speed. Some technologies record build speed by the weight of deposited material, while others measure it by the molded volume of the material. These speeds are also affected by the shape of the part being printed. Furthermore, it is unlikely that every 3D printer within a technology will achieve the same speed.
Layer height is usually a parameter of the ability to print fine details, but it is affected by the material used, the shape of the part and the printing speed. Before investing in any one technology, ask for sample parts (the same parts) from multiple 3D printer manufacturers. Sample parts should come with a report stating how long it will take to print the part, how many parts of that size and shape the printer can print at once, the price of each part, and material consumption.
Introduction to 10 metal 3D printing technologies
1. FDM and extrusion molding
△Metal parts 3D printed using BASF Forward AM’s stainless steel filament on an FDM 3D printer (Source: Ultimaker, IGO3D）
There are several 3D printing technologies that fall under the category of extrusion. One is the familiar fused deposition modeling (FDM), which uses filaments made from a plastic base into which metal particles are evenly injected. The metal filament used to print metal parts must contain a high proportion of metal powder (about 80%) and needs to undergo post-processing such as degreasing and sintering to remove plastic components and obtain metal parts. Some desktop FDM 3D printers on the market can print with metal wires, which are stainless steel (316L, 17-4 PH), copper and titanium.
Another technology uses metallic filaments with a higher concentration. So much so that it’s actually a solid metal rod, but can still be heated and extruded. These materials are often unique to a particular 3D printer, such as Markforged or Desktop Metal, and cost more than regular FDM but less than other metal 3D printing methods.
A third method of metal extrusion (although there are more in the industrial sector) is extrusion using metal pellets, which can be the same material as injection molding and therefore less expensive, or specially made pellets.
2. Metal powder bed melting using laser – Selective Laser Melting (SLM)
△The powder bed fusion equipment of metal printer manufacturer SLM Solutions uses lasers to melt metal powder (Source: SLM Solutions)
3D printers that use high-power lasers to selectively melt metal powder. This technology accounts for the majority of metal 3D printers and is often called selective laser melting (SLM) or powder bed melting (PBF). Printers can use “pure” metal materials or alloy materials.
SLM 3D printers use powdered metal raw materials. After being put into the printing chamber, the metal powder is spread out by a scraper or roller to form a thin layer on the substrate or building platform. Next, a high-power laser follows the sliced pattern to selectively melt the powdered material. The build plate is then lowered to the level of a small layer and a coater spreads another new layer of powder over the surface. The printer repeats these steps until it has a finished part.
SLM technology can print with better initial surface finish and higher accuracy than EBM technology.
3. Metal powder bed fusion using electron beam – electron beam melting (EBM)
△Powder bed fusion technology using electron beams is respected for its fast printing speed and high output. These surgical implants were printed using GE Additive’s Arcam 3D printer (Source: GE Additive)
Electron beam melting is a 3D printing technology that uses electron beams as the energy source, mainly for conductive metals. All EBM 3D printers consist of an energy source capable of emitting an electron beam, a powder container, a powder feeder, a powder recoater and a heated build platform. It should be noted that the printing process must be carried out in a vacuum. This is because the electrons from the electron beam will collide with gas molecules, which will “kill” the electron beam.
Due to the higher energy of the electron beam, EBM can be faster than SLM and produce parts with lower residual stress than SLM.
4. Metal binder injection
△Metal parts manufactured using the metal binder jetting technology of 3D printer manufacturer ExOne (acquired by Desktop Metal) (Source: ExOne)
Metal binder jetting can print parts with complex designs instead of being solid, resulting in parts that are equally strong while being significantly lighter. The porosity characteristic of adhesive jetting can also be used to achieve lighter end parts in medical applications, such as implants. Like other additive manufacturing processes, binder jetting can produce complex parts with internal channels and structures, eliminating the need for welding and reducing part number and weight. Redesigning your metal parts for adhesive jetting can significantly reduce the amount of material used and wasted.
Overall, the material properties of metal binder jetted parts are comparable to those produced with metal injection molding, one of the most widely used manufacturing methods for mass production of metal parts. Additionally, the adhesive-jet components exhibit higher surface smoothness, especially in the internal channels.
5. Wire arc additive manufacturing (WAAM)
△WAAM steel parts from MX3D (Source: MX3D)
Arc wire feed additive manufacturing uses metal wire as the material and arc as the energy source, which is very similar to welding. The arc melts the wire, which is then deposited layer by layer onto a forming platform by a robotic arm. As with welding, inert gases are used to prevent oxidation and improve or control the properties of the metal.
This process gradually fabricates the material into a complete three-dimensional object or repairs an existing object. There are no support structures to remove and finished parts can be CNC machined to tight tolerances or surface polished if necessary. Typically, printed parts require heat treatment to relieve residual stress.
6. Laser-based directed energy deposition (DED)
△Using laser directed energy deposition technology to 3D print metal parts on DMG Mori’s machines (Source: DMG Mori)
Laser directed energy deposition technology is used to melt metallic materials while being deposited by a nozzle. Metallic materials can be in powder or wire form. Although it is possible to build complete parts with DED technology, the technology is often used to repair or add material to existing objects. When combined with CNC machining, it can produce a precise finished part.
DED systems may differ from PBF systems in that the powders used are generally larger in size and require higher energy density. Compared with PBF system, it has faster build rate. However, it results in poorer surface quality and may require additional processing. The support structures typically used for PBF systems are rarely or never used for DEDs, which typically use multi-axis turntables to rotate the build platform to achieve different features. DED systems can repair or print on existing parts without the need for a powder bed.
7. Based on electron beam directed energy deposition (DED)
△The xBeam DED printer uses electron beams to melt metal wires to 3D print parts. Half of these printed parts are CNC machined to meet the final part quality requirements (Source: xBeam
Electron beam directed energy deposition uses an electron beam to melt a metal wire (rather than a powder) while being deposited by a nozzle. Much like the WAAM above, electron beam DED is prized for its speed. Unlike WAAM, these printers require a vacuum chamber. Typically, parts are printed to a near-net shape and then CNC machined to tight tolerances, as shown in the photo above.
8. Metal stereolithography technology
△Metal prints made of resin materials mixed with metal often appear in micro-3D printing (Source: Incus)
Metal lithography, also known as lithography-based metal manufacturing (LMM), uses a slurry of a mixture of photosensitive resin and metal powder as raw material. This light-sensitive slurry is selectively polymerized layer by layer under the influence of light. Metal stereolithography has excellent surface quality and is mostly used for (but not limited to) micro-3D printing, so it has extremely high details.
9. Cold spraying
△Source: Impact Innovations
Cold spraying is a manufacturing technique that sprays metal powder at supersonic speeds, bonding them without melting, which creates virtually no thermal stress. It has been used as a coating process since the early 2000s, but recently several companies have adopted cold spray for additive manufacturing because it can print at speeds about 50 to 100 times higher than typical metal 3D printers. Layer the metal to the nearest centimeter.
On the additive manufacturing side, cold spray is being used to rapidly manufacture metal replacement parts, as well as for on-site repair and restoration of metal parts, such as military equipment and machinery in the oil and gas industry. Reconditioned parts can, in some cases, be better than new.
10. Micro-nano metal 3D printing
△Micro-nano metal 3D printing from 3D MicroPrint (Source: 3D MicroPrint)
There are two methods for making tiny metal 3D printed parts: metal stereolithography, mentioned above, and micro-nano selective laser sintering (μSLS), a small-scale laser powder bed fusion technology, also mentioned above . Also known as microlaser sintering or microlaser melting, this industrial technology uses a powder bed and a fine laser.
Metal materials in 3D printing
△FDM printing metal filament from The Virtual Foundry (Source: The Virtual Foundry)
Almost any metal can be 3D printed. In addition to part complexity and speed, one of the main advantages of 3D printing metal is the savings in raw materials and virtually no waste. This is extremely important when printing with expensive materials such as titanium.
Some 3D printing methods can use materials already used for injection molding, such as some powders, filaments, and pellets, while other materials are uniquely formulated for 3D printing. If you know what material your part needs to be printed in, check out our guide below to learn about all the ways you can print titanium, aluminum, and steel.
Metal 3D printing services
△BeamIT metal 3D printing service (Source: BeamIT)
In order to benefit from all the advantages that 3D printing brings to metal parts and products, you don’t necessarily need to invest in your own 3D printer. There are a growing number of 3D printing service providers around the world who can not only print your product or prototype in the metal of your choice, but they can even provide advice on the best methods, materials and designs for your parts.
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