Learn how Binder Jetting can be used for small-to-medium production runs.
Metal Binder Jetting is rapidly increasing in popularity. Its unique characteristics make it especially suitable for small-to-medium production runs.
In this section, we dive deeper into the steps followed in Binder Jetting and the basic characteristics of the produced metal parts.
A metal Binder Jetting machine in action
Binder Jetting builds parts by depositing a binding agent onto a thin layer of powder through inkjet nozzles. It was originally used to create full-color prototypes and models out of sandstone. A variation of the process is currently raising in popularity due to its batch production capabilities.
The printing step in metal Binder Jetting printing takes place at room temperature. This means that thermal effects (like warping and internal stresses) are not an issue, like in DMLS/SLM, and supports are not required. An extra post-processing step is necessary to create a fully metal part.
Schematic of a typical Metal Binder Jetting machine
Metal Binder Jetting is a two-stage process. It involves a printing step and an essential post-processing step. Here’s how the printing process works:
The result of the printing process is a part in the so-called “green” state. A post-processing step is required to remove the binding agent and create fully metal parts.
There are two variations for this post-processing step:
Today, sintering is used in the majority of the applications, as infiltration creates parts with inferior material properties and not well documented mechanical and thermal behavior.
After sintering, Binder Jetting parts have very similar properties to parts manufactured with MIM. MIM is a manufacturing process that is used to mass-produce almost every small metal part found in consumer electronics or cars today.
MIM is a variation of the plastic Injection Molding process. Metal powder mixed in a plastic binder is injected into a mold to form the “green” part, which is then sintered to become metal.
So, metal Binder Jetting builds upon the know-how of the MIM process.
Binder Jetting is the only metal 3D printing technology today that can be used cost-effectively for low-to-medium batch production of metal parts.
Since no support structures are needed for printing, Binder Jetting systems can use their whole build volume. This allows it to compete in cost with traditional manufacturing, even for low-to-medium volume production.
Additionally, Binder Jetted parts have a smoother finish and sharper edges than DMLS/SLM, so extra finishing operations might not be necessary. Compared to DMLS/SLM, the cost of the raw metal powder is also lower, which plays a big role in the unit price.
On the other hand, parts produced with Binder Jetting will always have an internal porosity of about 0.2 to 2%. Note, that internal voids may not affect the tensile strength shown in the technical data sheets, but can greatly decrease the fatigue strength of a part.
Keep in mind that the sintering step is connected with significant part shrinkage. This shrinkage is non-homogenous and is difficult to predict with high precision. In practice, several trial prints are needed to end up with a CAD file that will produce the part with the desired final dimensions. The repeatability of the process is excellent though. This means that larger volumes of this part can be manufactured after successful calibration.
The table below summarizes the basic technical capabilities of a typical Metal Binder Jetting 3D printer today. For additional design guidelines, jump to the design rules.
|Property||Metal Binder Jetting|
|Material selection||Currently limited
Stainless steel, Tool steel, Tungsten Carbide
|Dimensional accuracy||± 0.2 mm (± 0.1 after trials)|
|Typical build size||400 x 250 x 250 mm
(-20% effective build size after sintering)
|Common layer thickness||35 - 50 μm|
|Typical surface roughness||RA 6 μm|
|Support||Not required for printing|
|Internal porosity||Between 0.2 - 2.0%|
|Cost per part||$$$|