Application Cases

Experiment Title: Piezoelectric Inkjet Printing Unit Drive

Experimental Principle:
Piezoelectric inkjet printheads operate based on the inverse piezoelectric effect. Vibration testing of piezoelectric actuators serves two main purposes: firstly, to physically measure the vibration amplitude of piezoelectric actuators with different dimensional parameters, and secondly, to analyze additional vibration information from the test results to guide the design of piezoelectric inkjet waveforms. Conventional contact-based vibration measurement methods require attaching various sensors to the test object, making them unsuitable for measuring small objects or subtle vibrations. In contrast, laser Doppler vibration measurement technology is a high-precision, high-resolution, non-contact, and non-destructive measurement method. When a laser beam is directed onto the surface of a vibrating object, the reflected laser carries motion information about the vibrating object, and its frequency changes—a phenomenon known as the Doppler shift.

Test Equipment:
Signal generator, ATA-2021 high-voltage amplifier, laser Doppler vibrometer, oscilloscope

Figure: Laser Doppler Vibration Measurement Experimental System Diagram

Experimental Procedure:
Laser Doppler vibration testing allows for the determination of both the vibration direction of the vibrating plate and its natural frequency and step response time. Initially, a positive single trapezoidal waveform (defined here as a waveform where the upper electrode potential is higher than the lower electrode potential) is applied between the upper and lower electrodes of the inkjet printing unit actuator. The waveform parameters are: rise time = 5 µs, voltage hold time = 35 µs, fall time = 5 µs, driving voltage U = 10 Vpp, frequency = 10 kHz. The displacement-time graph of the center of the piezoelectric vibrating plate is obtained from the laser Doppler vibration measurement system (as shown in the figure below).

Figure: Experimental Displacement Curve of Piezoelectric Actuator Under Unipolar Trapezoidal Wave Drive

Experimental Results:
Based on the above figure and the displacement direction calibration method of the Doppler vibrometer, the vibration direction of the vibrating plate can be determined:

• During the voltage rise time, the vibrating plate moves outward from the chamber, increasing the chamber volume and generating negative pressure, which draws ink from the supply reservoir into the pressure chamber through the flow restrictor.

• During the voltage hold time, the vibrating plate oscillates near its equilibrium position with minimal displacement, generating no pressure wave. The pressure wave generated during the voltage rise edge propagates within the chamber.

• During the voltage fall time, the vibrating plate returns to its original position, reducing the chamber volume and generating positive pressure, which expels ink through the nozzle.

Recommended Voltage Amplifier: ATA-2021B

Figure: ATA-2021B High-Voltage Amplifier Specifications