DyMePCo - Dynamic Meniscus Pressure Control for Inkjet Printing
Ingénierie et Architecture
The request of directly print with inkjet on large 3D objects thanks to a robot is booming, and this not only for graphical applications. Inkjet printing allows the precise deposition of picolitre sized droplets at high throughput. However, its reliability strongly depends on the drop formation process. The latter requires a stable meniscus at each nozzle. If the pressure at the meniscus is not properly controlled, leakage or air ingestion and bubble entrapment can occur, jeopardizing the entire process.
The DyMePCo project was initiated as a collaborative effort between KNF Flodos and the iPrint institute of the HEIA-FR. The primary focus was on utilizing KNF Flodos newly developed pumps for dynamic control of printhead meniscus pressure, specifically tailored for direct-to-shape applications.
The pumps employed in ink supply systems to bring the ink to the printhead nozzles often induce pressure pulsations which are deleterious for the meniscus stability. KNF Flodos AG recently developed a new pump featuring low pulsation and fast response. Yet, the pressure variations induced by fast accelerations of the printhead (e.g. in direct-to-shape printing) remain problematic. KNF already developed a prototype controller for such dynamic ink supply systems. Unfortunately, the employed test setup was very simplistic (no real ink, printhead, and no real motion) and had to be improved with a more realistic experimental setup, additional measurements and modelling, to develop an industry relevant meniscus pressure controller that can go on the market.
The project was divided into phases to achieve its objectives. The initial phase focused on building an experimental setup with a printhead and an ink supply system integrating the KNF diaphragm pumps. The entire system was mounted on a 3-axis robot to introduce motion in the system. The setup was designed both for industrial printing applications and hydraulic characterization. Several sensors were installed as part of the second phase of the project, which aimed to characterize the printhead and study its hydraulic behaviour. Both stationary and frequency-dependent measurements were performed to provide a detailed description of the printhead’s characteristic impedances. This enabled the completion of the model developed by KNF, providing a more accurate description of the overall ink system. The model was validated by comparing final experimental measurements from the test setup with model predictions when the system was subjected to step perturbations, induced either by the pumps or through jetting.
The accurate description of the overall system facilitated the design of various controller strategies with precise parameters, ensuring fast and stable control of the meniscus pressure.
Un appel à projets destiné aux entreprises pour stimuler leur innovation, leur compétitivité et leur durabilité
Le projet décrit ci-dessus fait partie d'un appel à projets extraordinaire intitulé "Innovation, compétitivité et durabilité", lancé par le domaine Ingénierie et Architecture de la HES-SO. Ces fonds sont destinés aux professeur-es proches des sociétés de services et d'entreprises suisses. Les hautes écoles concernées par cet appel à projets sont :
- HE-Arc Ingénierie ;
- Haute école d'ingénierie et d'architecture de Fribourg - HEIA-FR ;
- Haute école du paysage, d'ingénierie et d'architecture de Genève (HEPIA) ;
- HES-SO Valais-Wallis - Haute Ecole d'Ingénierie - HEI ;
- Haute Ecole d'Ingénierie et de Gestion du Canton de Vaud - HEIG-VD ;
- CHANGINS - Haute école de viticulture et œnologie.