The Experimental Study on the Influence Factors in Adhesive Dispensing Dot Diameter of Impact Jetting Valve

To obtain much higher accurate jetting dispensing, an investigation on a jetting valve with ball needle and conical nozzle is done in this paper. The theoretical model on the relationship among needle, nozzle, and adhesive during the impact process is established first. The experiments are done on a jetting valve prototype, and the results show that there are two factors that influence the ball needle impact speed: the spring compression and the impact stroke. The spring compression has little influence on the dispensing dot diameter from jetting, while the impact stroke greatly influences the dispensing dot diameter. Within a certain range, the dispensing dot diameter increases with stroke until the impact stroke reaches a certain value, then the dispensing dot diameter remains stable. Besides, when the nozzle structure stays the same, increasing the ball diameter of the needle will also increase the dispensing dot. The experimental result matches the theoretical model well. After the needle structure and impact parameter optimization on the prototype, the dispensing diameter can achieve
$\Phi 0.22$
mm, while the jetting viscosity is 1200 cps, the nozzle diameter
$\Phi 0.06$
mm, impact needle diameter
$\Phi 1.5$
mm, and stroke 0.06 mm. Therefore, the investigation, in this paper, can be used as the design basis for a high-accuracy jetting valve.