Possible Problems When Bonding Hot-Melt Adhesive
- Cooling of the adhesive during application that prevents making a good seam. A "good" tackiness can be formed, which is broken when the force is applied later on. Cooling can be caused by the following factors:
- open time of the adhesive is too short for application;
- application temperature is too low;
- not enough glue;
- air movement around the application area;
- low ambient temperature;
- cold material to be bonded.
- Effects of package contents.
- physically introduces additional stress into the seam;
- chemicals or solvents soften the gluing seam.
- insufficient pressing;
- movement of the bonded surfaces during consolidation of the joint.
- reusable material;
- more difficult for gluing material;
- the coated material (wax, lacquer) or impregnation.
When the box leaves the packaging machine, the valve opens
- Open time is too short - the adhesive cools down before pressing.
- The temperature of the adhesive is too high - gluing does not occur on time.
- There is too much hot-melt applied - the adhesive does not seize on time.
- Poor alignment of the packaging surface – it increases the tension in the "raw" joint.
- The ambient temperature is high - the adhesive does not seize on time.
- The temperature of the substrate to be bonded:
- too high - the adhesive does not seize on time;
- too low - the adhesive cools down before pressing.
- Bad pressing.
- The TM of hot melt is incorrectly selected.
Formation of filaments from the glue applicator
- Application temperature is too low.
- Screws because of the open doors of the room.
- The nozzle is too far from the application surface.
- Unsuitable adhesive for this application method.
- Malfunction of the applicator.
Lack of hot-melt in the head of applicator
- There is not enough equipment to melt the glue.
- The temperature of the melting system is too low.
- Low glue melting speed.
- The level of glue in the tank was allowed to drop too low to replenish.
- Too low voltage of the applicator.
- Blocking of the glue in the pre-melting device or feed system; possibly due to the wrong size or shape.
Excessive occurrence of vapors or odor
The temperature of the glue is too high:
- incorrect adjustments may have been made;
- the thermostat may be defective;
- There may be a heater problem;
- The glue tank may need to be cleaned.
Color change of hot melt in work
- Contamination of the hot melt adhesive.
- Thermal decomposition due to work at a temperature higher than recommended. This can lead to the following consequences:
- carbonization to form solid particles;
- Carbon deposits on the walls of the reservoir, the supply hose and the injector;
- change the viscosity of the hot melt adhesive;
- congealing throughout the system;
- clogging the injectors.