After 3D printed parts are unloaded from the 3D printers, the first step of post-processing is cleaning. In order to ensure that the liquid resin is completely removed from the 3D printed parts, ultrasound waves (20-40 kHz) are used in the cleaning process. This action also penetrates holes, cracks, and recesses. Appropriate solvent such as Isopropyl Alcohol (IPA) or other specialized solution can be used to enhance the cleaning process.