It is well known that most inkjet systems require careful pressure control of the ink inside the printhead. This is because the quality of print is often determined by the precision with which ink droplets are formed and land on the substrate – misshapen ink droplets and landing errors can results in costly mistakes. The stable control of meniscus pressure in particular (the pressure in the surface curve of the ink droplet when in contact with the nozzle) is critical for quality output.
Too high a meniscus pressure can lead to air ingestion and starvation (Figure 2) too low a pressure can result in nozzle plate flooding or ‘wetting-out’ (Figure 3) and pulsatility in meniscus pressure can lead to periodic effects in print output (Figure 4). All of these effects lead to irregular jetting and compromised print quality.
Many current systems use a motor-driven diaphragm pump to provide the meniscus bias pressure. Such pumps are pulsatile and offer limited controllability, meaning that additional components such as pulsation-dampers and proportional valves are required to achieve acceptable printhead performance.
The resulting system size and complexity is a disadvantage, particularly where there is pressure to make systems more modular (e.g. for ease of servicing, or where tuning of bias pressure is advantageous for a given printhead, or group of printheads).
The Lee Company’s range of disc pumps solves this problem. The pulsation-free output of the disc pump and controllability reduce system complexity and size, increasing design freedom. The disc pump is small enough to be directly integrated with the printhead, enabling a modular approach, with vacuum levels delivered tailored for each head.
The disc pump is perfectly positioned to integrate easily into ink delivery systems without the need for additional pneumatic components – making it possible to achieve precise, stable control of meniscus pressure in industrial inkjet systems.