What is Binder Jetting? How it works?
Binder Jetting is an additive manufacturing process which was developed in 1993. It is primarily used for printing parts using metal, ceramic and can also be used to print sand-moulds for casting. In binder jetting, a liquid binder is selectively deposited on a powder bed (can also be called the build platform) using a print head. Let us dive into its working and what benefits it has over other metal 3D printing processes.
The printing starts by importing a 3D model of the part into the printer software, which will direct the printer about the deposition of the binder. Once the printer is ready to create the part, a thin layer of powder is uniformly spread across the build platform using a re-coater. The thickness of this layer determines the resolution of the printer and the printed part.
As the layer of powder is spread, the print head moves horizontally in the x-y axis and deposits the binder according to the 3D model provided. After selectively projecting the binder on the layer, an incandescent lamp moves across the build platform to evaporate the solvents present in the freshly deposited binder.
After the incandescent lamp moves across, the powder bed is lowered by exactly one thickness of the powder layer spread by the re-coater. The re-coater then moves across the powder bed spreading another fresh, thin layer of powder. The binder is again deposited accordingly and this process repeats till the entire part is printed.
After the entire part is printed, it is completely encapsulated in unbound powder. Certain post processing steps are necessary in Binder Jetting before the part can be used. The part isn’t removed from the unbound powder yet and the entire powder bed is placed in a furnace to cure the binder, with the part still encapsulated in the unbound powder. The temperature of the furnace depends on the binder used.
As the binder is cured, the powder bed container is removed from the furnace and the unbound powder is removed to obtain the actual printed part. The sand-moulds are ready to use at this point but metal and ceramic parts need further post processing before they can be used. The metal and ceramic parts must be further sintered or infiltrated with low-melting temperature metal before they are ready to be used.
Binder Jetting can print full colour 3D parts using sandstone powder or PMMA powder, although this will require the printer to support dual printhead. The main printhead deposits the binder while the second printhead jets a coloured ink. Different colours of inks can be combined to increase the range of colour options.
Binder Jetting has a typical layer height of around 100 microns for full color models, 200-400 microns for sand-moulds and 50 microns for metal parts.
One of the biggest advantages of Binder Jetting its independence of support structures. The surrounding unbound powder provides the necessary support required (similar to SLS). This helps in reducing the waste materials generated in the printing process.
In Binder Jetting, the bonding occurs at room temperature which prevents any distortion or warping due to high temperatures, which can be a problem in other 3D printing processes.
This process can also be used to print multiple parts at a time as the entire powder bed is in the reach of the print head. Design engineers will have to incorporate this in the original 3D model to make full use of Binder Jetting printers.
It can print full colour parts while costing considerably less than SLM/DMLS 3D printing methods. Parts with complex geometries can be printed using Binder Jetting as it is not restricted by any support structures. It can also print relatively larger parts because it is not affected by thermal distortion and warping. Not to mention, the ability to print multiple parts at a time is a bonus that not many printing methods can provide.
Parts have lower mechanical strength as compared to other additive manufacturing processes. It does not perform well if parts have minute details and smooth surface as Binder Jetting parts normally have rough surface, which can be smoothen to some extent using further post processing but adding to the cost of printing and time required.
Binder Jetting is a useful metal 3D printing process which provides benefits which other processes cannot. Although metal 3D printers, in general, are not affordable for an average person as they can cost anywhere in between hundreds of thousands to a few million dollars, Binder Jetting is relatively cheaper than other metal printing processes. It won’t be a surprise if Binder Jetting becomes the most widely used metal 3D printing method in the near future.