CIJ

Continuous inkjet (CIJ) is a non-contact printing technology that propels tiny droplets of ink toward a moving surface at high speed, typically 4 to 12 meters per second. Unlike contact printing methods, the printhead remains separated from the substrate, making CIJ ideal for surfaces that cannot tolerate pressure, heat, or direct contact. The ink droplets are charged electrostatically and steered toward or away from the target by deflection plates, allowing precise placement even on irregular or fragile materials.

In operation, a CIJ system pressurizes liquid ink through a microscopic nozzle, creating a continuous stream that breaks into uniform droplets at a frequency between 50 and 200 kHz, depending on the printhead design. A timing circuit selectively charges each droplet; charged droplets are deflected by electric fields into a gutter and recycled, while uncharged droplets reach the substrate. This binary on/off mechanism produces dot-matrix-style characters and codes rather than the continuous lines of thermal or UV-cured technologies.

CIJ dominates applications where speed and non-contact printing are non-negotiable. Food and beverage producers use CIJ to print expiration dates, batch codes, and variable graphics on packaging, cans, and bottles at line speeds exceeding 1,000 meters per minute. The pharmaceutical, chemical, and cosmetic industries rely on CIJ for date coding without risk of contaminating or damaging product surfaces. Cables, pipes, and extruded profiles are also common targets because the printhead does not interfere with the production line geometry.

Ink, maintenance, and operational constraints

CIJ inks are typically solvent-based, fast-drying formulations with viscosity between 1 and 3 centipoise to ensure proper atomization and droplet stability. The continuous stream and recycling gutter mean that unused ink is drawn back into the supply system; this circulation also prevents nozzle clogging during idle periods, though many systems require periodic flushing and cleaning cycles. Printhead wear from debris and ink degradation necessitates regular replacement, often every 12 to 18 months depending on duty cycle and ink chemistry.

The term 'continuous' distinguishes CIJ from drop-on-demand (DOD) inkjet systems, which fire droplets only when needed. Continuous systems consume more ink but tolerate higher line speeds and are less sensitive to electrical noise or pressure fluctuations. CIJ is also fundamentally limited in resolution and color reproduction because it relies on binary droplet deflection; advanced multi-color or high-resolution printing instead uses DOD or thermal inkjet printheads. In industrial settings, CIJ remains the workhorse for fast, robust, single-color coding and marking.