Piezoelectric devices are commonly used in inkjet printing technology to control the ejection of ink droplets for various applications, including packaging printing. In an inkjet printer, the piezoelectric device plays a crucial role in generating pressure pulses that lead to the controlled ejection of ink droplets from the printhead nozzles. Here's how the process works:
Printhead Structure: The printhead in an inkjet printer consists of a series of tiny nozzles or orifices through which ink droplets are expelled onto the printing substrate. These nozzles are arranged in a grid pattern, and they need to be controlled individually or in groups to create the desired image or text.
Piezoelectric Actuators: Each nozzle in the printhead is associated with a piezoelectric actuator. A piezoelectric material is one that generates an electric charge when mechanical stress is applied to it and, conversely, deforms when an electric field is applied. The piezoelectric actuator consists of this material and is located near the nozzle.
Ink Reservoir: The printhead is connected to an ink reservoir that holds the ink to be used for printing. The ink is usually a liquid that needs to be accurately and precisely controlled for the printing process.
Control Circuitry: The inkjet printer is equipped with control circuitry that manages the entire printing process. This includes receiving image data from the computer, processing it, and sending signals to the piezoelectric actuators.
Droplet Ejection Process:
Charge Application: When a printing command is issued, the control circuitry sends an electric voltage pulse to a specific piezoelectric actuator associated with a particular nozzle. This voltage pulse causes the piezoelectric material to rapidly deform, creating a mechanical stress.
Pressure Generation: The mechanical stress applied to the piezoelectric material generates a pressure pulse. This pressure is transmitted to the ink in the nozzle chamber.
Ink Ejection: The sudden pressure increase in the nozzle chamber forces a droplet of ink to be ejected from the nozzle. The size and velocity of the droplet are controlled by the duration and intensity of the voltage pulse applied to the piezoelectric actuator.
Multiple Nozzles: The printhead contains numerous nozzles arranged in a grid. By selectively applying voltage pulses to the piezoelectric actuators associated with different nozzles, the printer can control which nozzles eject ink at any given moment. By coordinating the timing and intensity of these pulses, the printer can create precise patterns of ink droplets on the printing substrate, resulting in the desired image or text.
In packaging printing, this technology allows for high-resolution and high-speed printing with accurate control over droplet size and placement. It's worth noting that there are other inkjet printing technologies as well, such as thermal inkjet, that use different mechanisms to control droplet ejection.