Relationship Between Waveforms and Ink in Inkjet Printing
When voltage is applied to PZT (piezoelectric ceramic material), the piezoelectric ceramic deforms, thereby changing the volume of the ink chamber and causing the ink to move and eventually be ejected.
The method of applying this varying voltage to the PZT is called the waveform. In other words, the waveform controls the piezoelectric ceramic to drive ink ejection.
1. Influence of Ink Sound Velocity on the Waveform
-
Inks with higher sound velocity (such as water-based inks) require shorter waveform pulse widths, while inks with lower sound velocity (such as oil-based inks) require longer pulse widths.
-
Impact on printing performance: If the pulse width does not match the ink characteristics, it may cause unstable droplet flight, satellite droplets, or angled jetting, thereby affecting printing accuracy.
2. Influence of Ink Viscosity on the Waveform
-
High-viscosity inks require greater jetting energy (such as higher voltage).
Viscosity also affects the pressure oscillation decay time between two waveform pulses, so the pulse interval must be adjusted accordingly. -
Impact on printing performance: Viscosity mismatch can easily cause ink misting, filament formation, or nozzle clogging. Poor waveform optimization may further aggravate these problems.
3. Influence of Ink Density on the Waveform
-
Density affects the speed of sound in the ink, therefore the pulse width must be adjusted accordingly to obtain the optimal pulse peak point.
-
Impact on printing performance: If density and waveform parameters do not match, it may affect the integrity of droplet formation and the stability of droplet flight.
Synergistic Effects Between Waveforms and Ink
▲ Resonance Phenomenon:
A waveform that works well at one printing frequency may perform poorly at another. This is because as the frequency increases, the pressure wave generated by the previous pulse may not have fully decayed. It may either overlap with the new pulse (resonance enhancement) or cancel it out. Therefore, when determining the printing speed, the resonant frequency points of the equipment should be avoided.
▲ Multi-Pulse Technology:
By applying multiple precisely timed pulses to each droplet, it is possible to generate larger and faster droplets, or stabilize the jetting of low-viscosity inks. This requires precise control of pulse timing to utilize pressure wave resonance for secondary amplification.
Key Considerations in Practical Applications
☆ There is no universal waveform solution:
Waveform optimization is a fine-tuning process tailored to a specific combination of ink and printhead. When changing the ink brand or model, even if the ink type is the same, the waveform may need to be re-optimized.
☆ Be cautious with “high drop height” modes:
Significantly modifying waveform parameters (such as increasing voltage or pulse width) to sacrifice printing speed in exchange for greater jetting distance may cause frequent problems such as ink misting or color mixing, and requires a high level of technical expertise from equipment manufacturers.
☆ Importance of temperature control:
Ink viscosity is highly sensitive to temperature. Therefore, many high-end industrial printheads are equipped with built-in heaters and cooling systems to maintain the ink temperature at the optimal level, ensuring consistent waveform performance and stable printing results.