PVA, or Polyvinyl Alcohol, is a soft and biodegradable polymer that is highly sensitive to moisture. When exposed to water, PVA will actually dissolve, which makes it a very useful support structure material for 3D printing. When printing extremely complex shapes or ones with partially enclosed cavities, PVA supports can be used and easily removed by dissolving in warm water. Standard supports may have been difficult to print or remove in these situations. PVA can also be used as a model material if there is a need to make quick prototypes.
Some 3D printers such as the Ultimaker 3 have two extruders which means the machine can print with two different materials. “Classic” FDM 3D printers have only one extruder which means that the part itself and the support material are printed from the same material. After the print is finished, the supports need to be removed which can be a difficult job, especially if the part has complex geometries.
When the supports are made out of the same material as the part itself, it is a common issue that after you remove the supports marks are left on the surface of the print. With PVA that issue is avoided since it is a material that dissolves in water. Because PVA filament dissolves in water, it is a great choice for a support material when printing complex geometries, large overhangs and detailed features on models.