Bead Mill for Digital Inkjet Ink & High-End Paint: Achieving Sub-Micron Pigment Dispersion Without Printhead Clogging Digital printing demands zero tolerance for oversize grains: while D50​ must reach 80–150 nm, the true commercial threshold is eliminating the tail (D99​<200–300 nm) to prevent immediate piezo and thermal printhead nozzle clogging.