Every business that uses hot melt adhesives knows the importance of keeping the production line running efficiently. Over time, degraded adhesive, or char, builds up in the nozzles, filters, hoses, and tanks, impairing the quality of the adhesive and leading to a range of mechanical problems. In this article, we discuss the six most common problems with hot melt systems (HMS) and how to resolve them.
1) Charred Adhesive In The Melting Tank
Char and gel appear in the melting tank when the temperature is set too high. Check what temperature the adhesive manufacturer recommends. Lower the temperature if the machine is set too high for the adhesive and ensure the temperature controller is functioning correctly.
2) Bubbles In The Adhesive
If air bubbles appear in your adhesive, the root cause can be overheating and thermal decomposition. Check that the HMS temperature setting is correct and, if you suspect your adhesive is contaminated, empty the tank, and clean the applicator. If the level of adhesive in the tank is low, refill it and clear the supply hose.
3) Nozzle Drips
If hot melt flows excessively or drips when the applicator is off, check the module, nozzles and tip. Replace any component that is worn or faulty. Dripping can also result from the air pressure being too low. Increase it as required.
4) Hot Melt “Stringing” Down The Line
When hot melt stays on the nozzle and “strings” down the line, ensure the nozzle is the correct distance from the substrate and adjust the spacing. The viscosity of the hot melt could be too high, or the HMS temperature set too low. Check and adjust as required.
5) Bead Squeezing Out Past The Flap
This can be the result of incorrect glue application in terms of quantity of glue or using the wrong size nozzle for your machine. If there is too much adhesive being delivered and leaking out from the substrate, lower the tanks air pressure to dispense less glue. Alternatively you can use a smaller sized nozzle.
6) Adhesive Failure
Adhesives are designed to ‘stick’ within a specific temperature range, so in case of poor penetration or adhesion failure, first check if the HMS temperature is set too low. Next, check the application pressure at the nozzle and ensure this is correct for your adhesive. If the pressure isn’t high enough, your HMS may be unable to deliver sufficient adhesive volume to your substrate to form the required bond strength.
Prevention Is Better Than Cure
Regular, scheduled maintenance is essential to keep your hot melt equipment working efficiently. Expert care sustains machine performance and avoids problems that impede high volume production runs.
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