Droplet analysis in an inkjet-integrated manufacturing process for nylon 6

With the recent progress in inkjet technology, it has been employed to develop manufacturing processes to deposit a range of functional materials for various applications. The authors have researched the possibility of a novel inkjet-integrated process for nylon 6. The concept requires stable jetting and deposition of activator and catalyst mixtures of caprolactam. This paper reports on droplet formation characteristics of the molten mixtures in the inkjet system using high-speed imaging and quantitative image analysis. By varying the process parameters, the droplet shape and kinetics were studied in addition to the stability of droplet generation. Results showed the jetting frequency did not have an effect; and with low jetting voltages, instability occurred due to the low kinetic energy, which made the droplets vulnerable to the air motion caused by convection around the heated printhead. The catalyst mixture which had a particulate nature was also investigated for consistency, to ensure the droplet characteristics were unaffected by this. Increasing the vacuum level decreased the droplet kinetics due to the higher surface energy which existed on the meniscus, which was found to be inside the nozzle. It was possible to have satellite-free and stable droplet generation conditions.