Abstract
The needle-type inkjet dispenser has been widely used for various research and industrial purposes. The droplet jetting from the dispenser is closely related to the needle motion, which strikes against the nozzle seat. The strike of the needle on the nozzle seat often cause additional impact due to the bounce back, which may produce multiple droplets per jetting trigger. However, the needle motion is difficult to measure, and the actual behaviors have been known little. In this study, we measured the needle motion using an accelerometer and visualized jetting images to understand jetting behavior in relation to the needle motion. Then, we investigated various parameter effects on needle motion and jetting behaviors based on our proposed measurement methods. From the experimental results, we found that needle travel distance should be in the optimal range in order to produce single droplet per jetting trigger. In conclusion, we proposed an effective parameter selection method for the optimal jetting based on understanding of the jetting physics.
Highlights
The needle-type inkjet dispenser has been widely used for various research and industrial purposes
For better understanding of jetting physics, we propose a measurement method using an accelerometer to estimate the needle motion, by measuring the vibration caused by collision of the needle either on the nozzle seat, or on the stopper
Since the needle motion is difficult to measure during the jetting process, we propose an indirect measurement method based on the vibration signal measured from an accelerometer attached to the dispenser housing
Summary
The needle-type inkjet dispenser has been widely used for various research and industrial purposes. The strike of the needle on the nozzle seat often cause additional impact due to the bounce back, which may produce multiple droplets per jetting trigger. We investigated various parameter effects on needle motion and jetting behaviors based on our proposed measurement methods. Due to handling of large number of images, the use of high-speed camera might not be suitable for observing jet behavior over a long period of time. To overcome the drawbacks of using high speed camera imaging methods, drop visualization based on strobe LED has been used to investigate the drop formation from piezo inkjet heads[14,15]. We extended previous strobe LED visualization using a CCD (charge coupled device) camera with a low frame rate of 30 fps (frames per second) in order to understand the jet behavior from needle type dispensers
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