Introduction to the Jet Glue Fluid Dynamics Model

Spray dispensing principle

1. The impact type spray dispensing valve is normally a normally closed valve, and the impact needle is in close contact with the nozzle to seal the fluid flow.

2. The driving force drives the firing pin to lift, and the firing pin disengages from the nozzle. The liquid in the flow channel is sent to the gap between the firing pin and the nozzle under pressure.

3.When the firing pin hits the nozzle, an instantaneous high pressure is formed between the firing pin and the nozzle, which forces the glue to quickly spray out of the nozzle.

Basic properties of fluids

During the process of spraying the adhesive liquid with a piezoelectric injection valve, a complex flow is formed in the flow channel. Therefore, the flow characteristics of the adhesive liquid directly affect the performance of the injection. A fluid whose dynamic viscosity does not change with the velocity gradient is called a Newtonian fluid; A fluid whose dynamic viscosity changes with velocity gradient is called a non Newtonian fluid. In the field of electronic packaging, UV glue, epoxy resin, Tufy, Silicone, hot melt adhesive, anaerobic adhesive, etc. generally exhibit non Newtonian fluid characteristics. Non Newtonian fluids can be divided into the following types of fluids:; Bingham plastic body, plastic expansion body, pseudo plastic expansion body with yield stress, etc.

Jet fluid theory

The jet fluid theory of piezoelectric jet valves in dispensing and spraying work directly affects the jet performance of the jet valve by the velocity of the glue passing through the nozzle.

1.If the spraying speed of low viscosity glue is too high during the spraying process, it will break due to inertial force when forming a single droplet after passing through the nozzle, resulting in satellite droplets during the spraying process and poor dispensing.

2. High viscosity glue spraying. Due to the high viscosity of the glue, a certain speed must be maintained when the glue passes through the nozzle to cut it into individual droplets for spraying. If the spraying speed is too low, the glue cannot be sprayed by hanging on the nozzle hole.