Chieh-Wen Wang

Method and apparatus for measuring the droplet frequency response of an ink jet printhead

To speed up the printing speed of an inkjet printer, the manufacturers normally focus on increasing the droplet frequency response. Hence, it has become a very important technique to measure the droplet frequency response of an inkjet printhead. A magneto-electric method is proposed to measure the droplet frequency response. The magneto-electric apparatus contains a metallic detecting plate and a magnetic ring with a gap of about 100 micrometers filled with a nonmagnetic insulating material. The magnetic ring itself is made of a high-permeability alloy consisting of about 78% nickel and 22% iron. When an ink drop jetted from a nozzle makes a contact with the metallic detecting plate, which is perpendicular to the nozzle plate of a printhead, a current is conducted through the detecting plate immediately, and detected as a portion of expected signal. The expected signal is then processed by a signal processing circuit for counting the number of jetted drops, and determining the maximum droplet frequency response of the inkjet printhead as a function of the driving frequency of an applied voltage across the printhead.

Meniscus oscillation of ink flow dynamics in thermal ink-jet print head

Meniscus oscillation usually occurs after jetting drops in Drop-on-Demand inkjet head. It is important for ink refill motion. Ink refill motion affects many jetting performance in inkjet technology. Therefore it is very important to understand ink refill motion process for designing inkjet head dimensions and ink properties, such as nozzle diameter, barrier thickness, ink viscosity and surface tension. This meniscus oscillation is a kind of under-damped oscillation. The refill time is defined, as the time required returning to the initialization, the free surface obeys damped oscillation and oscillates between meniscus mounding and recession when the amplitude of the oscillation reduces to dispersion. This study researches several inkjet heads using computational fluid dynamics simulation. CFD solver, such as FLOW_3D, is used to solve the problem. After calculation, the results are plotted with post-processor such as plot software and output to printers. This paper shows the break- off time, the refill time and operation frequency of the inkjet head.

Driving technology for prolonging the lifetime of thermal bubble ink-jet printhead

Based upon the purpose of prolonging the lifetime of an ink- jet head, we have attempted to apply double pulse to a heater during a drop ejection cycle. There are five parameters (pulse widths and voltages and the time delay) to define the double pulse. Taguchis method is used to investigate the effects of these parameters. The experimental results show that under the optimized condition with (18 V, 2 microseconds), (14 V, 4 microseconds) and delay time 12 microseconds double pulse can prolong the life of ink jet heads up to an averaged drop counts of 4.8 X 108 as compared with that of 3.0 X 108 using single pulse. Also, improper parameters can dramatically shorten the life of an ink-jet head, or disturb the drop formation.