Most of the reasons the VCN method works so well for cleaning parts also applies to support material removal. The extracting liquid is continuously delivered to the internal material and then removed to carry out any dissolved or insoluble material generally every 2 to 5 seconds. Because the internal material is constantly in contact with fresh bulk fluid and is physically carried from the internals so quickly, your part is finished much faster and more efficiently than any other process on the market. Because of the high throughput, one VCN machine can handle parts produced from multiple printers. The VCN process is the only process in the world supporting a continuous 3D printing line in the industry.
As with cleaning parts, VCN works equally as well with solvents as with aqueous solutions. Although excess liquid monomer removal can be much faster than solid support material, safety and costs are generally a major concern. Physical methods are labor intensive and often pose environmental or quality control hurdles to overcome. The most reliable method for monomer removal is liquid extraction.
The solvents chosen for the removal task are generally alcohols because of the chemical nature of the solvents. Alcohols are both lipophilic and hydrophilic and actually have a limited solubility with polymers. This is exactly why they are good as a monomer removal after printing. The task is to either solubilize or physically remove monomer without softening and damaging the solid structure. Physical methods such as letting drip, spinning or shaking can remove much of the monomer but monomer left on internal surfaces and dead end areas need to be solubilized or forced out with a liquid of some type. Physical removal of the monomer with a liquid also has the benefit of the less chance of damage that can be associated with a lot of handling. Because the alcohol is partially soluble with monomers, the alcohol can lift the monomer from surfaces and reach into tight areas. When the VCN process produces alcohol vapors within the internal channels, the expanding vapor actually pushes the monomer out of the part. The removal process is in this case is both physical and chemical in these processes. Physical removal dominates initially in the process and chemical dissolution refines the extraction process at the end.
The main problem with using alcohols however is the flammability of the solvent. Heating and extracting in batches where air is present is not safe and is often done in enclosed areas having expensive fire suppression systems if done at all. The VCN process operates in a vacuum and the absence of air is a requirement to produce vapor. The process is therefore safe for flammable solvents and our VCN equipment is built to NFPA 69 standards when required. See the video below for liquid monomer extraction from 3D printed parts.
YOUTUBE VIDEO: INTERNAL CLEANING OF INDUSTRIAL PARTS. The video shows the removal of excess liquid monomer from a 3D printed part. In the field these parts are cleaned with a one minute VCN cycle time.