Metal 3D printing has been around for quite a few years. However, more recently, it has become a highly competitive solution to traditional machining methods, especially with the development of Direct Metal Laser Sintering (DMLS), which is also referred to as Selective Laser Sintering (SLS).
In this article, we will explore what metal 3D printing is, how it works, its applications, and how it compares to traditional machining methods such as computer numerical control (CNC).
What is Direct Metal Laser Sintering?
Direct metal laser sintering (DMLS) is a metal additive manufacturing process that belongs to the powder bed fusion 3D printing family. The DMLS is one of the few 3D printing technologies that make parts directly from metal. 3D printing can be done in various ways, but as with most powder bed infusion methods, DMLS involves spreading a thin layer of metal powder across a build platform. A laser is then moved across the surface of the metal powder to sinter it.
Sintering involves heating the metal powder particles enough to fuse them but not heated enough to reach their melting point. A re-coater then applies additional layers of powder to be sintered, thus allowing the object to be “printed” one cross-sectional layer at a time. By following this process, DMLS can create a 3D object by building up a series of thin layers.
Metal 3D printing utilizes metal in powdered form to create objects. One of the ways these granular metals are made is through gas atomization. In this process, a high-velocity gas stream flows through an expansion nozzle that siphons molten metal, spraying it into a container that dries in the air and lands in powder form.
The Fabrication Process of DMLS
- The build chamber where printing will occur is filled with an inert gas (one of the noble gases) to mitigate oxidation of the metal powder, and then the chamber heated to the optimum build temperature.
- A thin layer of metal powder is distributed across the build platform and a high-power laser scans the cross-section of the component, fusing the metal particles together and creating the next layer of the part.
- The build platform drops down by one thickness layer when the scanning process is complete and the re-coater spreads another thin layer of metal powder. The new layer of metal powder is then sintered as in steps one and two. This process is repeated until the whole part is finished.
- The excess powder is removed when the build chamber cools to room temperature, and the parts are heat-treated while still attached to the build platform to relieve any residual stresses. This ensures structural solidity of the manufactured parts. The components are then removed from the build plate via cutting or machining and are ready for use or further post-processing.
Applications of Metal 3D Printing
There are many different and interesting applications of metal 3D printing. Medical and dental implants are one of the most popular uses of this technology, and these products are now largely considered the best available option for patients. This is primarily because the fittings can be easily tailored to individual needs and result in a highly customized and close fit on the patient.
The next major industry that uses 3D-metal printers is the automotive industry. BMW, Audi, and FCA are already considering this, not only for prototypes but also for full-time parts production. However, most car companies will use metal 3D printing for prototypes of certain parts of their cars; that way, they can efficiently test how the part will handle certain conditions. Metal 3D printing helps car companies to save time and money in the prototyping process.
Metal 3D Printing in Comparison to Computer Numerical Control
Metal 3D printing is favourable to traditional methods of machining in many aspects. For one, the metal powders in DMLS are easily recyclable. On average, less than 5% of the powder is wasted. The unused powder is collected after each print, unwanted substances are removed, and fresh material is added to the remaining metal powder to produce the next part.
Comparing this to traditional manufacturing, such as computer numerical control (CNC), metal and plastic object manufacturing can be a wasteful process. In CNC, machines are automated to build from sheets of metal or plastic with high levels of accuracy compared to when the same machining is done by hand. However, when aircraft manufacturers who use CNC create metal parts, they still discard up to 90% of the material. None of that material can be reused.
However, using metal 3D printing to build the same metal parts uses less energy and reduces waste. Completed 3D printed parts can also be up to 60% lighter than their machined counterparts. The aviation industry alone would save billions of dollars in the conserved fuel through this weight reduction.
The metal 3D printing takeover has begun thanks to the minimal waste which the process offers compared to traditional manufacturing methods. Unfortunately, a barrier is that metal 3D printing is expensive now, although it will become cheaper soon as it becomes used more.
Eventually, it will become a front runner as the main manufacturing method. The powders can easily be made by a method called gas atomization and the fabrication process is quite simple. A laser sinters the metal powders and fuses them and the part is made layer by layer. This simple automated process creates parts that do not require further machining and are much lighter and stronger than parts produced by traditional methods. Metal 3D printing also has many applications, from making medical and dental implants to being used to manufacture car parts. The amount of applications of metal 3D printing is limitless.
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SOURCES
Castells, R. DMLS vs SLM 3D Printing for Metal Manufacturing. Element. 2016. https://www.element.com/nucleus/2016/06/29/dmls-vs-slm-3d-printing-for-metal-manufacturing
Groover, P. Introduction to Manufacturing Processes (1st ed.). Wiley. 2011
Mensley, M. 2020 Metal 3D Printer Buyer’s Guide. All3DP Pro. 2020. https://all3dp.com/1/3d-metal-3d-printer-metal-3d-printing/
Varotsis, A. Introduction to metal 3D printing. 3D Hubs. 2019 https://www.3dhubs.com/knowledge-base/introduction-metal-3d-printing/