Needle dropping means that when the dispensing valve closes, glue overflows from the needle. In fact, 95% of the reasons are caused by the uneven diameter of the needle used. Too small diameter needle will affect the flow of liquid and cause back pressure, leading to the failure of backdraft. Only when the needle diameter is too small, will it affect the effect of bubble discharge. Too small needle will also affect the action of bubble removal, as long as the larger needle is replaced. This problem can be solved.
In dispensing needles, the back pressure produced by using tapered or inclined needles is the smallest. If dispensing is carried out with a smooth liquid, it will have a better effect. Using tapered needles is one of the ways to solve the problem of needle leakage.
When there is a drawing problem on the needle, close the glue valve immediately, but the glue will still overflow from the dispensing needle. In fact, there is air or air bubble in the liquid, which is one of the reasons for the leakage of the needle. Therefore, the air in the liquid should be removed beforehand, or the glue without bubbles should be used. In fact, the centrifugal defoaming method can be used to remove the glue, which is also one of the effective solutions for needle leakage.