PVA is an abbreviation for polyvinyl alcohol, a water-soluble material. It is often used with multi-extruder FDM 3D printers as a support material. The biggest advantage of PVA filament is its ability to dissolve in water. This means there are no ugly marks left on the print after the support material is removed.
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.
Imagine printing a very complex structure with an FDM printer that has only one extruder. When that print finishes, it requires some post processing but first of all, you need to remove support material, but that’s the main problem because the support material is the same material out of which the part is made. It is extremely hard and challenging to manually remove support from the complex geometry part. That is when PVA is used because it dissolves in water, there is no need to manually reach challenging places of a complex part to remove supports.
PVA in general works very well with PLA and Nylon filaments since it requires same operating conditions such as the desired temperature.
Parts printed with PVA supports usually need to be placed in water for a few hours (depending on the manufacturer’s specifications), until there‘s no undissolved material left.
Remember, PVA is a hydrophilic material, “it likes water” so the material connects with water molecules which results in PVA dissolving in water. PLA is a hydrophobic material so it “doesn’t like water” which means PVA and PLA are a perfect match because putting a PLA part in water does not affect it since it’s made out of a hydrophobic material, it doesn’t absorb water.