How 3D print metal ?
3D print : FDM
When we talk about 3D printing the most popular technique, which generally comes to everyone's mind, is FDM (Fused Deposition Modeling), which consists by printing deposited molten material layer after layer, this is generally used for thermoplastics as; ABS, PLA, Nylon, etc. But its range of materials does not end there. This is not the only technique used in 3D, there are many others such as SLA, SLS, etc.
This article aims to present the different techniques that dominate the market today when we talk about 3D metal printing, those for other materials will not be presented there even if some are similar.
3D metal printing
When we talk about 3D metal printing, it's the same, several techniques are available, it's a new technology constantly under development. Each company can perfect or create its own technique, we not sure that in a few years we will print metal the same way as we do today. They are always research and development of techniques that would bring characteristics equal to forging metals , or even superior, with good precision and at a lower cost.
3D printing lost wax and casting
The most classic method when you want to print precious metals or alloys such as; gold, silver, brass, etc. Is 3D printing lost wax and casting.
This method consists in 3D printed a model, the first time, in wax. This is then placed in plaster, once the plaster has hardened it will serve as a mold, it will be placed in the oven beforehand to melt the wax model. Once finished, a molten metal will be poured into the mold to obtain the model in the chosen metal after solidification of this one.
The main advantages of this technique are the precision of the details that we can obtain, the ease of working with precious metals and its advantageous production cost.
3D printing : SLM
Another technique used is SLM (Selective Laser Melting), which are into the family of powder bed technologies.
We first place a layer of powdered metal on a platform where a laser will draw a pattern, on contact with the laser the powder will harden, then we put another layer of metal on top and the laser will keep continue, and so on, to harden the powder, forming the desired model layer after layer.
We usually confuse SLM and DMLS, because these are similar in their mode of operation, and use the same technology, the difference is that SLM fuses the metal powder at the same temperature constantly, which will fuse the metal completely. In order to have characteristics even superior to forged metals. As for DMLS, it will merge metal particles at different temperatures and pressures. The metal will be sintered and not melted as in SLM. The primary advantage of this technique is that metal alloys can be printed where SLM can only print pure metals. But the downside is that we have a more porous final model with poorer characteristics.
The cost of production with these techniques is higher, which is why these technologies are not suitable for parts that can be easily manufactured using traditional methods.
We can also quote the EBM which is similar to these two technologies except that it uses an electron beam instead of the laser.
3D printing : DED
DED (Direct Energy Deposition) is a mixt between FDM and SLM. The metal powder will be directly applied by the printer head with a laser to harden the powder where it sits. This technique is useful for working on existing parts, in order to add material to them, for repairs for example. However, it can print a complete model without any problem. These advantages and disadvantages are similar to SLM.
FDM with metal
Some companies have developed their own filament consisting of a mix of a base metal and a polymer (preferably biodegradable), so that these can be printed with the "classic" method of FDM.
Unfortunately this method has certain disadvantages, in particular it requires a post-processing in order to melt the plastic particles present in the model, the final model will therefore have a higher porosity, a loss of volume and a non-isotropy.
Binder Jetting is a technology using an additive manufacturing process. It's sort of a mix of powder bed technologies and classic 2D printers.
First, a layer of powdered metal is placed on a platform, then the printer head, similar to 2D printers head, will deposit droplets of a binder polymer to bind the metal particles together. Then we put another layer of metal on top to create the model layer by layer. This method requires the same post-processing as with FDM metal, but get better characteristics and precision.
Keep in mind ~
Keep in mind that metal printing is not just about a specific technique, and there are many others. These above being just the most popular and used on the market, but it is not said that they will remain so, these can be improved or changed.
Metal 3D printing is mainly focused on the aerospace, automotive and aeronautic sectors, which is why there is, unfortunately, not much research in precious metals or alloys, because these are more complicated to deal with and less interesting for their sectors.
However, 3D printing remains a new technology with enormous potential. This is starting to be exploited and much remains to be discovered.