8. Metal Binder Jetting
uses Binder Jetting for the fabrication of metal objects. The metal powder is bound using a polymer binding agent. It allows the production of objects with complex geometries that are far beyond the capabilities of conventional manufacturing techniques.
Functional metal objects do require a secondary process like infiltration or sintering, without which the part would have poor mechanical properties.
With infiltration, the metal powder is bound by a binding agent. Once cured, the object is placed in a furnace, where the binder is burned out. This leaves the object at about 60% density, with voids left throughout by the burned-out binder.
Bronze is then added by capillary action to infiltrate the voids, which results in an object of about 90% density and much greater strength. It should be noted objects made by Metal Binder Jetting typically have lower mechanical properties than those made with Powder Bed Fusion.
Common applications for Sand and Metal Binder Jetting are sand casting, functional metal parts, and full-color models.
Strengths include low-cost and large build volumes plus functional metal parts.
A limitation is mechanical properties are not as good as with metal powder bed fusion.
After the parts are fully cured, they are taken out of the loose unbonded powder and cleaned. An infiltrant (a fast-curing resin for strengthening 3D printed models) is often introduced to enhance mechanical properties. Coatings can also be added to enhance colors.
Sand Binder Jetting is a low-cost technology for producing parts and sand cast molds and cores. After printing, the cores and molds are removed from the build area and cleaned, removing any loose sand. They are then ready for immediate casting. After casting, the mold is broken apart and the final metal component is removed.