Too small a needle will affect the flow of liquid back pressure, resulting in the formation of dripping phenomenon shortly after the closure of the valve, too small a needle will also affect the start of the glue valve bubble action, as long as the replacement of larger needles can be solved this problem.
The conical angled tip produces the least back pressure and the smoothest liquid flow. Air within the liquid in the dispenser glue valve closure will produce dripping phenomenon, it is best to exclude the air within the liquid in advance, or change the glue is not easy to contain air bubbles, or first will be centrifugal defoaming of the glue in the use of the first.