High-Frequency Spray Valves, Dispensing Valves, Conformal Coating Valves, Pneumatic Adhesive Dispensing Valves, High-Precision Micro-Adjustment Fully Automatic Dispensing Machines, Adhesive Dispensing Guns

Frequently Asked Questions

Q: How is the air inlet tube installed on a dispensing valve?

A: Dispensing valves are controlled by solenoid valves, which have one air inlet and two air outlets. The direction is selected by closing the valve; A is normally open, and B is normally closed. For “suction-type, plunger-type, and diaphragm-type” valves, the normally open A tube is connected to the middle position of the valve, while the normally closed B tube is connected to the last air fitting. For “ejector-type” valves, the connection method is exactly the opposite: the normally open (A) line connects to the last air tube on the valve, while the normally closed (B) line connects to the middle position. Air flows through the solenoid valve to direct the movement, thereby controlling the up-and-down motion of the valve’s cylinder piston.

Q: How can I tell if there is a problem with the valve?

A: First, when both the dispensing valve and the feeder are properly pressurized and adhesive flows from the delivery tube into the valve (with no needle installed), visually inspect the valve outlet for any adhesive leakage. If leakage is present, it indicates that the valve’s sealing ring or sealing head is not airtight and needs to be replaced. Second, if the valve needle drips during use, remove the needle first to purge the adhesive. The purged adhesive should form a continuous, unbroken line without bubbles, and no adhesive should continue to flow once the dispensing stops. At this point, observe the valve: if the flow stops immediately, it indicates the valve seal is intact. Reinstall the needle, purge the system, and check the flow stoppage again; if it is normal, there is no issue. However, if the needle’s inner diameter is too small and the feed rate is too high, a vacuum may form inside the needle, preventing the adhesive from draining completely, resulting in dripping after stopping. In this case, there are two options: 1. Replace the needle with one that has a larger inner diameter. 2. Reduce the feed pressure to decrease the adhesive flow rate and lower the amount of adhesive entering the valve body. With a slower flow rate and a smaller needle bore, the negative pressure will be reduced.