3D printing is a known technology since early 1980s. 3D Metal printing is one of the latest chapters of the evolution of additive manufacturing.
The conventional manufacturing methods use excessive amount of energy and material to produce a single metallic object. Also, the amount of metal waste during those processes is
massive. On the other hand, in 3D metal printing the amount of waste becomes negligible as this same waste is firstly used as the model’s supports.
We have discussed Why the evolution of manufacturing starts with Metal 3D printing in a previous blog. Nowadays, 3D metal printing has a plethora of applications across the board in the industrial sector. Manufacturing, aerospace, jewelry, medical and dental sectors are among those which already make use of metal 3D printing technology.
In 3D metal printing the cost is driven from the volume or weight of the object rather than the size or the complexity of the part.
Let’s discuss now the most widely used metal 3D printing technologies.
Most Important 3D Metal printing technologies
The most important and well-known metal 3d printing technologies are:
➢ DMLS (Direct Metal Laser Sintering) or DMP (Direct Metal Printing)
➢ SLM (Selective Laser Melting)
➢ EBM (Electron Beam Melting)
DMLS (Direct Metal Laser Sintering) or DMP
This is the most well-known metal 3D printing technology. It uses a laser for sintering very thin layers of metal powder in order to create a 3D metal object. It is used to produce very
complex geometries in high detail which is a clear advantage compared to the conventional manufacturing methods.
The 3D printed part has excellent mechanical properties as its isotropic, and they tend to have higher strength and degree of hardness comparing to the parts made by traditional
manufacturing techniques.
DMLS / DLP Applications
DMLS additive manufacturing technology is ideal for functional prototypes and for parts with challenging geometries. It is also applicable to objects with high level of detail and very tight tolerances such as tools and manufacturing small batches of parts. It is used in aerospace and automotive industries, medical devices, dental sector, jewellery and chemistry.
SLM (Selective Laser Melting)
This technology is very similar to DMLS as the main principle of using a laser for sintering metal powder is the same. The main difference is that while DMLS creates parts from metal
alloys, SLM creates final objects from single metals. In this method the metal is actually melted in the build chamber which is filled with inert gas. Thin layers of metal powder laid on the bed of the 3D printer.
Every time the layer scans and lays the metal on top of the previous one repeating the steps until the completion of the 3D
model. In SLM the produced part has even higher strength and better mechanical properties comparing to DMLS due to the actual melting process of the metal which creates a more
isotropic result of the part with extremely low porosity.
SLM Applications
The application of SLM is very much the same as DMLS. However, this method’s advantage is that the produced parts will perform better where more fatigue and high stress is required.
SLM produces parts equal to castings making it the ideal method for applications where better mechanical properties are needed.
Materials in 3D Metal printing
➢ Aluminium
➢ Stainless Steel
➢ Titanium
➢ Cobalt Chrome
➢ Nickel Superalloys (Inconel)
In 3Dtechnologies4U ltd. we are offering 3D metal printing in stainless steel and aluminium.
Post-Processing
This step is important in order to finally produce a clean and aesthetically excellent 3D metal
part with the methods of DMLS or SLM.
➢ Remove the model supports
➢ Remove any loose metal powder
➢ Manually clean the part
➢ Heat treat the produced part (if required) to improve and stabilize its mechanical properties as well as to relief any residual stresses left inside the part during the process.
➢ CNC machining (if required) for fine details
➢ Apply blasting (if required) to improve surface quality and part’s appearance
➢ Metal plating (if required)
➢ Polishing to improve surface quality and part’s appearance
EBM (Electron Beam Melting)
In Electron Beam Melting technology, the name self explains the application as an electron beam is produced by an electro-gun is used (instead of a CO2 laser as in DMLS or SLM) to fuse metal particles and form one layer after the other the 3D model. Firstly, the metal powder will fill the printer’s tank and it will be laid in very thin layers. After that it will be preheated and will be fused by the electro-gun repeating those steps and printing layer by layer a very highly detailed 3D object. Important to mention is that for such a technique the material must be conductive otherwise this method is not applicable.
EBM Applications
This approach is mostly used in aeronautical and military industries as well as in medical engineering and design of implants such as hip prosthetic using titanium alloys.
Materials
➢Mainly Titanium Alloys
EBM Post-Processing
After allowing some time for the parts to cool down there are a number of options that can be followed for post processing to EBM manufacture a 3D printed model.
➢ Remove the model supports
➢ CNC machining (if required) for fine details
➢ Apply blasting (if required) to improve surface quality and part’s appearance
➢ Coating (if required)
➢ Polishing to improve surface quality and part’s appearance
The main benefits of 3D metal printing
• In conventional methods the cost is decreasing as the volume increases meaning in very high volumes a normal fabrication process becomes very cheap. In other methods
like casting or injection molding there is always the excessive cost of the matrix (tool) in order to start producing parts which they need to be produced in such volumes to
exceed the cost of tooling. On the other hand, the cost in 3D metal printing as well as the rest of 3D printing methods, is irrelevant to volume and is consistent regardless of
whether it is one part or a batch is to be produced.
• In 3D metal printing the complexity is irrelevant to cost too. Selecting 3D metal printing is an automated process and the higher the complexity of a geometry the
more justifiable is the cost of manufacturing. Again, in conventional manufacturing operations, the cost will be skyrocketed as the manufacturing of a high-level detailed
part needs to pass a few methods which every time add on more cost.
• 3D metal printing has less than 5% waste of material as the loose metal powder can be reused in the next printing task. To be able to produce a very challengeable
geometry with ordinary manufacturing techniques it will have to be a result of milling, CNC machining, micro-machining or casting followed by machining. With all those methods the waste is excessive and exceeds 40% of the material while also significant
is the amount of energy need to be consumed to operate the above machines. Hence, is reasonable to say that the automated 3D metal printing method has significantly less material waste and smaller environmental footprint comparing to conventional
manufacturing operations.
Design Principles for 3D metal printing
1. Think twice to design once the supports really needed for your part. Supports needed are to reduce the overhang of the printed model while printing and sintering. Too
many supports mean more waste of material, more printing time and more time to be spent as post process. Important to mention is that the supports need to be positioned
in such a location that even if the 3D model is small, they can be accessible by tools to be cut off and the part’s surface to be cleaned. Supports also serve as a structural platform for the next layer to be laid off properly.
2. Optimize the contact face between the part and the printer’s bed. It’s a significant factor to reduce the printing time as well as for fewer supports. It is also a smart way
to reduce the material waste even more.
3. Orientation of the part. It is extremely important for parts that are top-heavy to be positioned upside-down in order to lower as much as possible the center of gravity
during sintering. Again, it also acts as a reasonable method to reduce the supports.
4. Sintering. For parts that will be subjected into sintering operation, it is worth paying extra attention in the design process. The part due to the thermal stresses,sometimes
experiences warping or curling. Therefore, in order to maintain a good quality surface and a intact wall thickness the designer should add fillets and chamfers as they act like
stress relief features and increase the chances for a part to be printed without local deformations.
Other external sources with 3D metal printing content can be found: