Inkjet Print Head Wave Reflection for High Viscosity Ink
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Solution Overview
Problem
Existing inkjet print heads face inefficiencies in expelling droplets due to trapped dirt or air bubbles, especially with high viscosity inks, leading to reduced actuation efficiency and nozzle blockages, and continuous flow print heads are not suitable for all ink types.
Innovation Solution
The design incorporates actuation chambers with piezo actuators, chamber inlets, nozzles, and outlets, along with a reservoir and pump, utilizing a compliance mechanism at the chamber outlet to reflect pressure waves and generate sufficient pressure for droplet ejection, maintaining efficiency even with high viscosity inks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuous flow arrangement is used to prevent trapped dirt and air bubbles, then reliability is improved, but actuation efficiency decreases significantly (about 50% lower)
Solution Approach 1:
The ink delivery system is segmented into distinct functional zones: a pressure chamber for ink storage and a separate actuation chamber for droplet ejection. This segmentation allows the pressure chamber to maintain continuous flow for reliability while the actuation chamber optimizes pressure generation for actuation efficiency, resolving the contradiction between these two requirements.
Solution Approach 2:
A piezo actuator is introduced as an intermediary device between the pressure chamber and the nozzle. The piezo actuator generates precise pressure waves in the actuation chamber to expel droplets, decoupling the continuous flow requirement from the actuation mechanism. This intermediary enables both continuous flow operation and high actuation efficiency to coexist.
2Power
If the nozzle is arranged at an end of the pressure chamber, then actuation efficiency is maximized, but dirt and air bubbles become trapped near the nozzle
Solution Approach 1:
The system is divided into a pressure chamber where ink is supplied with continuous flow, and a separate actuation chamber where the nozzle is positioned. This spatial segmentation allows the pressure chamber to prevent bubble trapping while the actuation chamber maintains optimal nozzle positioning for efficient droplet ejection.
Solution Approach 2:
Ink undergoes preliminary filtration and continuous circulation through the pressure chamber before entering the actuation chamber. This preliminary action removes potential contaminants and air bubbles before the ink reaches the nozzle, preventing blockages while maintaining actuation efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution achieves a droplet ejection efficiency decrease of 10% or less compared to traditional designs, allowing for effective operation with high viscosity inks and reducing the risk of nozzle blockages.
Implementation Method 1
Each actuation chamber is associated with a respective piezo actuator. The piezo actuator is arranged to generate a pressure wave in the main part of the actuation chamber
Implementation Method 2
The print head further comprises a means for reflecting the pressure wave which means is provided at the second end of the actuation chamber
Data Source
AI summary
In an inkjet print head an actuation chamber substantially extends in a first direction and the actuation chamber is associated with a piezo actuator arranged to generate a pressure wave in the actuation chamber. The pressure wave propagates in said first direction. A nozzle is associated with the actuation chamber such that a droplet may be expelled through the nozzle upon generation of the pressure wave in the actuation chamber. A reservoir is in fluid communication with the actuation chamber via an inlet and an outlet of the actuation chamber. A pump means is provided for pumping ink from the reservoir, via the inlet, through the actuation chamber, via the outlet back into said reservoir. The print head is provided with a means for reflecting the pressure wave at the outlet of the actuation chamber for enabling to generate a sufficient pressure at the nozzle for expelling the droplet.