More and more functional inks are developed to enlarge the applications of inkjet printing. Yet, the stability of the inks is often challenging. For example, particles might agglomerate and clog the printhead, eventually compromising the whole printing process. Having a reliable filtering system is therefore key for complex inks. Here, we present a novel passive filtering system based on the inertial microfluidic concept that can potentially be used to filter inkjet inks in a continuous manner. The system has been first optimized thanks to numerical simulations and then characterized experimentally.
The design of today’s inkjet printheads is often limited by the micromanufacturing methods used. Furthermore, today’s inkjet technology suffers from several limitations in term of ink viscosity, particle size and jetting distance. Yet, new micromanufacturing technologies have been recently developed. In this work, we explore the potential of using femtosecond laser glass micromanufacturing to fabricate inkjet printheads parts. The performance of such modified printheads is compared to their commercial counterparts.
3D printing with current multi-nozzle drop on demand print heads is lacking in terms of surface quality (without post treatment) or printing of overhanging structures without support material in contrast to single nozzle inkjet 3D printing (where the part perimeters are printed with a CNC motion), which in turn is lacking in terms of volume throughput (and therefore only used for the fabrication of small parts) as everything has to be printed with one nozzle. In order to print with enhanced surface quality and overhanging structures - free of support material – as well as reasonable productivity for the production of larger 3D parts, a printing process for industrial multi nozzle printheads with CNC printing motion was developed. First 3D parts printed with paraffin wax were produced and characterized to estimate the potential of this process.
Inkjet is gaining popularity in digital production for its high flexibility, productivity and compatibility with many substrates. The core of the inkjet system is the printhead, a sophisticated device depositing ink accurately and on demand through thousands of independent nozzles. However, the complexity of the printhead presents challenges for maintenance and stable operation. Therefore, maintaining precise control over all process parameters is essential to ensure consistent quality and optimal performance. Ink rheology is an important process parameter to control. Changes in rheology caused by solvent evaporation, ink aging, sedimentation or simply a slightly different formulation of the manufacturer can lead to major quality flaws in the printing process. Commercial solutions for rheology measurements can typically only measure viscosities at frequencies of up to 10 kHz and the measurement takes place outside of the printing process. Here, a measurement system has been developed, which can monitor the rheology in the process at internal resonance frequencies of 100-200 kHz using only the printhead as the measurement device together with printing electronics which has piezo self-sensing capabilities. This system is an upgrade to a previously developed and industry tested nozzle status monitoring system that uses the piezoelectric effect to map printhead internal acoustics for nozzle failure detection.
The popularity of inkjet technology is growing in the industry due to the many benefits it brings. However, the complexity of the process and hardware required to deliver a drop on demand accurately and at high speed poses a reliability challenge. With many complex parameters in the ink and printhead affecting drop quality, maintaining a stable environment is key. There has been increasing interest in sensing technologies that use the piezoelectric actuator in the nozzle to measure the acoustic response of the nozzle chamber. Several papers have been published on the use of piezo sensing to detect nozzle status. The aim of this paper is to present an innovative way of measuring the ink pressure within the nozzle chamber by sensing the piezoelectric response. Driving and measurement are performed using custom hardware to quantify the acoustic response of the system after actuation of the piezo. The variations in the dominant frequency of the response signal can then be correlated with variations in pressure. This method makes it possible to measure pressure variations along the print head, opening up a range of new possibilities for identifying events that can have a direct impact on print quality.
Rub resistance is a parameter of major importance for the quality of inkjet printouts used in marking and coding. Yet, it becomes challenging to evaluate when the substrate has been bent prior to testing, like in the case of electrical cables, wires, or optical fibers. This communication presents a solution embodied by a prototype machine specifically designed and built for this purpose and a testing method associated with it. In particular, all the parameters of interest, i.e. the bending speed, angle and radius, and the rubbing speed and applied force can be adjusted over a range representative of the real industrial constraints. The processing of the data allows for a precise quantification of the rub resistance of the ink printed on previously bent substrates.