Instability behaviours of a jet array in inkjet printing of molten caprolactam

Purpose - The purpose of this paper is to present the findings on jet array instabilities of molten caprolactam. Initial investigations showed that although a suitable range of parameters was found for stable jetting, there were cases where instabilities occurred due to external sources such as contamination.Design methodology approach - The inkjet system consisted of a melt supply unit, filtration unit and printhead with pneumatic and thermal control. A start-up strategy was developed to initiate the jetting trials. A digital microscope camera monitored the printhead nozzle plate to record the jet array stability within the recommended range of parameters from earlier research. The trials with jet instabilities were studied to analyse the instability behaviour.Findings - It was found that instabilities occurred in three forms which were jet trajectory error, single jet failure and jet array failure. Occasionally, the jet with incorrect trajectory remained stable. When a jet failed, bleeding of melt from the nozzle due to the actuations influenced the adjacent jets initiating an array of jets to fail similar to falling dominos.Originality value - The research concept is novel and investigating the jet array instability behaviours could give an understanding on jetting reliability issues.