Binder Jetting is a lesser used but versatile 3D printing technology which has applications in a variety of industries. Binder Jetting is similar to Selective Laser Sintering in that it requires powder on a build platform to 3D print. However, there is no laser used as with SLS, and Binder Jetting does not involve the use of any heat.
Read our guides to other 3D printing technologies here.
Approx time to read: 4 minutes.
- 1 Binder Jetting Post-Printing
- 2 Binder Jetting Materials
- 3 Advantages and Disadvantages of Binder Jetting
Before you start printing with Binder Jetting
To 3D print, you require a digitized model of the part you wish to create. These can be downloaded online from sites such as Thingiverse, or you can design them yourself. Compatible file types with most 3D printers include .stl, .obj, and .gcode files. These can then be sent to the 3D printer for slicing and printing.
Binder Jetting Process
Binder Jetting involves depositing a binding agent onto a powder bed, layer-by-layer, to form a part. These layers are formed, one after another, until the full part is created.
A printhead passes over the powder surface, depositing binder droplets (that are around 50 microns in diameter) which bind the powder particles together to form each layer of the eventual 3D model.
Once a layer is finished, the powder bed is lowered a layer, and a new layer of powder is spread over the previously printed layer for the printhead to pass over.
The accuracy and finish of the binder jetted object depends on a variety of factors. Firstly, the layer heights are important in determining the smoothness of the finish. In addition, the droplet size and powder size are important for accuracy and how well the complex geometry will be captured.
With Binder Jetting, supports are not required, in contrast to FDM or SLA. This is because parts are surrounded by powder. This also helps to reduce post-processing time, and also less materials are used up.
Binder Jetting Post-Printing
Once printed, the part is left to cure and gain strength. After this, the part is removed from the powder bed. Any powder that hasn’t been bound is removed via compressed air.
Like SLS, Binder Jetting uses a powder bin. However, parts are printed without heat so there is no differential cooling and therefore no warping. This means that multiple parts can be printed easily during the printing process. This makes Binder Jetting a good candidate for low to medium volume metal part manufacturing.
If 3D printing full-color sandstone accuracies, are usually limited to 100 microns, whereas cores/molds are limited to between 240-380 microns. However, some printers are able to print as low as 50 microns if an especially smooth surface is required, though this makes printing more expensive and slower. Due to the lack of heating, parts have very good dimensional accuracy. However, there are potential shrinkage issues during the infiltration or sintering processes. These are hard to predict and can cause parts to shrink by 0.8-2% of the part’s total size.
Here’s another video explaining the process:
Binder Jetting Materials
There are two main types of materials used with Binder Jetting, sandstone and metals. Their applications vary greatly which we will explain in the next part.
Binder Jetting with Sand
Binder Jetting is a low-cost alternative to traditional manufacturing processes to 3D parts made from sand. A benefit of using Binder Jetting with sand is that it can create models in full color, which is a rarity in 3D printing. This is done through mixing plaster-based powders with the liquid binding agent.
The printhead jets the binding agent whilst another (secondary) printhead jets the material to create the full-color model. The part is then cured and cleaned to retrieve the finished part.
This method is usually used for creating molds. These molds are created and then casted, before being broken apart so the metal part inside can be removed. This allows for complex geometric shapes, in addition to being low-cost.
Binder Jetting with Metal
Binder Jetting can also be used to produce metal parts. The process involves metal powder being bound using the polymer binding agent. Like with sand, Binder Jetting allows for the creation of geometrically complex parts that traditional manufacturing methods simply cannot do.
Metals compatible with Binder Jetting include stainless steel, inconel, and tungsten carbide.
To create metal parts through Binder Jetting, a secondary process is required however. This is usually a process called ‘infiltration’, though sometimes ‘sintering’ is performed.
Once the part has cured, it is removed and put inside a hot furnace. The binding agent is heated until is burns off, reducing the part to approximately 60% density. Bronze is then used to fill in these non-dense parts until the part is has over 90% density and better strength. Parts created through this technique however are usually less strong than parts created through powder bed fusion.
Once the part is cured, it is sintered in the furnace until it reaches a high density of at least 97%. This procedure is different however as it can cause shrinkage and potential warping in the part.
Advantages and Disadvantages of Binder Jetting
Binder Jetting Advantages
- Doesn’t require supports. Means less post-processing time and less materials are used up compared to technologies such as fused deposition modeling and stereolithography.
- 100% of unused powder can be reused in future prints.
Binder Jetting Disadvantages / Limitations
- Even with sintering or inflitration, parts created through Binder Jetting are not as strong as parts created through powder bed fusion. They often have less mechanical strength, and break/elongate at lower force.