VCN AQUEOUS UNITS FOR POWDER REMOVAL FROM ADDITIVE MANUFACTURING PARTS

Surfactant solutions are perfect fluids for use in the VCN process. Vapor formation is instantaneous in surfactant solutions due to the low surface tension. The instantaneous explosion of vapor on a part’s internal surfaces forces liquid rapidly from the part, carrying residual powder out to the bulk fluid. The rapid formation is intense; however, the vapor bubbles formed are gentle on the internal surfaces, preventing damage even to the most delicate parts. Air is used to collapse the vapor and force fluid into the part for the next cycle. Repeating the cycles every few seconds results in a fast removal of powder from the part.

Surfactants can also assist in removing the powder from a surface. The polar nature of surfactants can neutralize surface charges that can resist the removal of small powder particles. Mild acid solutions can slightly etch surfaces, breaking solid bonds at the surface. Particles act as nucleation sites, and as the solution evaporates near a particle, the acid concentration can increase, making it more effective.

Particles in aqueous systems are periodically removed and filtered to maintain a fresh solution. Repeating washes with particle-free solutions or rinses removes residual particles. The process is fast, so many washes or rinses can be repeated without significantly extending the total removal time. Generally, a one- or two-minute VCN time removes most of the powder. The surfactant concentration does not need to be high to keep operating costs and waste disposal volumes low.

The above video shows an aqueous unit removing powder from a basket of small printed parts. The fluid level can be preset on a PLC to a maximum of 2 feet. A typical VCN cycle is 1 minute, and the chamber can be drained to remove and filter the powder. The wash cycle can be repeated with a clean heated solution as many times as required. Multiple VCN rinses can be run to remove residual powder and surfactant. The parts are then dried with heated air under vacuum.