1) Dripping and/or stringing at the nozzle
Possible causes and solutions:
A. Adhesive temperature is too low
Increase the temperature setting of the gun zone.
B. The nozzle is positioned too far from the product
Move the nozzle closer to the product.
C. The module does not close properly due to weak spring tension or contamination
Adjust the spring tension and/or clean the module, nozzle, and gun.
D. The hotmelt adhesive viscosity is too low for the nozzle diameter used
Because sealing takes place inside the module itself, a small amount of adhesive always remains inside the nozzle. With relatively thin hotmelt adhesives, this may cause dripping.
Possible solutions:
- Lower the adhesive temperature if possible
(note: excessively low temperatures may cause stringing) - Use a higher-viscosity adhesive
- Install a Zero Cavity module
2) Repeated nozzle blockages
In most cases, this problem occurs because the system has been left heated for long periods without being used. As a result, the hotmelt adhesive burns inside the components, causing contamination from burnt adhesive particles.
If this occurs, do not attempt to manually remove burnt residue or flush the hoses. This may loosen additional burnt particles and make the blockage worse.
The correct solution depends on the severity of the contamination or burning.
A possible temporary solution is to install an inline filter between the hose and the gun head. This filter will capture burnt particles coming from the hose.
After installing the inline filter, remove the nozzle and briefly activate the solenoid valve to flush loose particles from the gun head and module.
It is also recommended to replace all other filters. A drop in adhesive pressure toward the gun head is often an indication of contaminated filters.
In cases of severe contamination or burning, it may unfortunately be necessary to replace at least the hoses and, in exceptional cases, also the guns and/or modules.
3) Spray pattern
The gun does not respond properly to the activation signal
Possible causes and solutions:
A. Incorrect adhesive gun type
The machine speed may be too high for the current gun type. An air-open / spring-closed gun is often not suitable. In such cases, use an air-open / air-closed gun.
B. The solenoid valve is not powerful enough
Install a stronger solenoid valve.
C. Incorrect type of solenoid valve
Hotmelt systems require special solenoid valves suitable for high temperatures. Replace the valve with the correct type.
D. The control system is inadequate
To open a solenoid valve quickly, it must first receive a higher current pulse before returning to normal operating voltage.
E. Air pressure to the solenoid valve is incorrect
Use the pressure values specified on the solenoid valve.
F. The solenoid valve is positioned too far from the gun
Install the solenoid valve as close as possible to the gun and use metal tubing between the valve and the gun.
The swirl pattern is unstable and/or poor
In a swirl nozzle, the outer air holes are drilled inward at an angle. This causes the adhesive stream from the center hole to rotate, creating a circular spray pattern.
Proper adjustment of a swirl pattern requires precision and patience. The final result largely depends on the selected swirl nozzle and swirl module.
There are generally three types of swirl modules:
- Swirl module with a single air hole at the nozzle connection
- Swirl module with a disc at the nozzle connection
- Swirl module with multiple air holes at the nozzle connection
In general, larger nozzle diameters also require larger air holes. If the air holes are too small for the adhesive flow, compressed air may enter the adhesive stream.
With type 1 swirl modules, larger nozzle diameters may result in an unstable swirl pattern. This happens because air distribution becomes uneven: the nozzle holes closest to the air inlet receive more air than those farther away, causing the spray pattern to become distorted or unstable.
Type 1 swirl modules are therefore mainly suitable for smaller nozzle diameters, such as those used in anti-slip applications.
Type 2 and 3 modules are generally suitable for nearly all swirl applications. The swirl modules in our product range are type 2.
Adjusting the swirl pattern
The easiest way to adjust a swirl pattern is to gradually increase both adhesive pressure and swirl air pressure until a proper circular pattern is achieved.
If the adhesive pressure becomes too high, it will no longer be possible to achieve a correct swirl pattern regardless of air pressure settings.
If the air pressure is increased too much after a good pattern has been achieved, the swirl pattern may disappear and sputtering or air bubbles may occur.
A swirl nozzle therefore has limits for both adhesive pressure and air pressure.
Exceeding these limits will result in an unstable or undesirable swirl pattern.