Critical operating factors of a jetting dispenser driven by piezostack actuators: statistical analysis of experimental results

In this work, critical operating factors of a jetting dispenser driven by a dual type of the piezostack actuators are experimentally identified. As a first step, geometrical information and working principle of the jetting dispenser are briefly addressed. Subsequently, in order to investigate jetting performance eight important operating (or working) factors of the dispenser such as exciting stroke and frequency are chosen based on two levels for each factor. Then, in order to reduce the number of experiments, one-sixteenth fractional factorial design method is adopted and an experimental apparatus to measure the weight of a single dot is established. After measuring the weight of a single dispensed dot under each test condition, the effect of each operating factor on the jetting performance is analyzed using a statistical program. The main effects and interaction effects on the average and standard deviation of the weight of a single dispensed dot are then analyzed and discussed in details. In addition, the analysis of variance results for average single dot weight is undertaken to determine the specific values of the critical factors which can provide optimal jetting performances. Consequently, critical operating factors for a small amount and small weight variation of a single dot are identified, which directly represent the performances of a non-contact jetting dispenser driven by piezostack actuators such as dotting accuracy and dotting speed.