The glue dispenser sends compressed air into the glue bottle (syringe) and presses the glue into the feed pipe connected with the piston chamber. When the piston is in the upward stroke, the cavity of the piston is filled with glue, and when the piston pushes the glue dropping needle downward, the glue is squeezed out from the needle mouth. The amount of glue dripped is determined by the downward distance of the piston, which can be adjusted manually or controlled by software.

Control methods of dispensing machine: time pressure method, screw pump distribution method, piston pressure method and spray dispensing.

1. The time pressure method used in SMT in the early days, by controlling the time and air pressure, can obtain the predetermined glue amount and glue point diameter. Generally, the amount of coating increases with the increase of pressure and time, and the volume of glue droplets dispensed is a function of the application time of glue pressure in the syringe.

2. Screw pump distribution method uses rotary pump pressurization technology to drive glue solution for coating, which has high repeatability and can be used for coating adhesives with poor performance. It uses the motor to drive the screw to rotate the distance or angle, and its working mode can produce rubber drops with better repeatability than the time pressure mode.

3. Piston pressure type. This method uses a closed-loop dispensing machine and works by matching the piston and cylinder. The piston moves downward in the cavity to push the glue solution, and the volume of the cylinder determines the glue application amount, thus obtaining the glue application amount and shape.