Binder jetting is a somewhat low-cost form of advanced 3D printing. It is a cross between SLS and material jetting in terms of mechanics. The material cost is relatively low but large amounts of post-processing is generally required. The resulting parts are also weaker than parts from SLS printers.
The basics
The print bed is covered with a smooth thin layer of powdered material, just as in SLS printers. A print head – similar to those found in material jetting printers – then passes over the print bed and jets tiny droplets of glue onto the powder. If the print is to be coloured, one or more inks can also be printed at the same time as the glue, allowing for full-colour prints. Once the layer is complete, the build area moves down by the height of a layer, it is then re-covered with material before the print arm resumes. This process continues until the print is complete. When the print is finished, it is then left in the printer for the glue to cure. Once the glue has cured, compressed air is used to recover the unused powder.
Depending on the material, you will need one or more post-processing steps. Metal parts need to be sintered or infiltrated with a low melting temperature metal, such as bronze. Full-colour prints are infiltrated with acrylic before being coated with a second layer of acrylic. This increases the vibrancy of the colours. Models made from sand do not need post-processing
The results
Binder jetting prints are very porous, with metal prints can having a density as low as 40%. This makes prints very brittle. The infiltration or sintering process helps with this, increasing the mechanical properties of the print. The resulting parts are still comparatively brittle, however, and are generally not suitable for functional parts. Sand-based models are typically used as moulds. The low price of sand or sand-like material makes them ideal for one-use moulds. This type of mould is single-use and is typically broken as the final metal part is removed from them.
The main selling point of binder jetting is for prototypes or moulds. The material cost of prints is very low, as are production times. As an additive manufacturing technique, structures are possible that would not be replicable with traditional manufacturing techniques. The use of a powder bed also means that you don’t need to use supports. This is because the powder itself provides support for the model. Being able to reclaim and recycle unused material at the end of the print also helps to keep costs down.
The main downsides of binder jetting are related to the poor mechanical properties of the prints. Full-colour prints especially are pretty much only suitable for display purposes. It is also difficult to create fine details with binder jetting as they will generally not survive post-processing.
Binder jetting is generally intended for industrial mould creation and prototyping rather than for functional models. Have you got a project that could make use of binder jetting? Let us know down below.
