How to Prevent Your Glue from Stringing

One of the most common issues that many packaging line operators experience with their adhesive melter is stringing. Stringing is when the adhesive is applied to the box, but before the flaps are closed on the cartoner, the glue starts to dry and string like cotton candy floating through the air.

There are a couple of fixes for this issue. Whether you are using a straight, right angle or swirl pattern nozzle, try moving the applicator gun closer to the box flap where you are applying the adhesive. The stringing could be caused because it is travelling too far of a distance from the applicator gun to the box. The shock from hitting the cooler factory air could be causing it to lose viscosity and start drying before it even hits the box. Not only will that cause stringing, that might also compromise the integrity of the glue hold on your product packaging.

Another cause of stringing glue could be temperature. Every adhesive is different and each one might require a different melt temperature. In order to keep the adhesive a consistent viscosity, make sure that the temperature on your glue tank and applicator guns are set correctly per the adhesive requirements. If the adhesive is too viscous then you might need to increase the tank temperature or change to an adhesive with a lower viscosity. If your tank temperature is correct, but your guns are not hot enough, then the glue could start to cool while travelling from the tank to the applicator gun. In this scenario, you would see that the thickness of the glue as it leaves the nozzle. Some line operators might try fixing the issue by putting a larger diameter nozzle on the module, which could be a temporary fix, but the real issue could be the temperature setting on the gun. Simply increase the gun temperature as needed to ensure a smooth, consistent adhesive flow.

There could also be an issue with the adhesive you are using on your packaging line. Like many products, if the adhesive is too old, has been sitting for too long, or has been heated and cooled too many times, this could cause stringing. We recommend that you drain all old adhesive from your tank, clean the tank with a cleaner such as Purge Plus™, and refill with fresh adhesive.

Universal Systems SE recommends trying to correct stringing if it is happening to your packaging line. Some line operators may think it is not that big of an issue, or they might blame the adhesive manufacturers, when in fact it could be a simple and important fix.

For more information or technical support to help you better understand how to fix your stringing glue, please call Universal Systems SE at (561) 272-5442 or email

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Nozzle Engagement

Nozzle engagement is rarely discussed because not many people understand what it truly is. Well, it’s simple, nozzle engagement details the length of the orifice hole. This means that engagement length will impact the flow of adhesive from the module onto the package. So as the engagement increases, making the length of the nozzle orifice longer, the flow of adhesive will decrease. For example, if a nozzle’s specifications are .018″ diameter x .075″ engagement, it means that the length of the .018″ diameter orifice is .075″ in length.

There are a few other key factors, along with engagement, to consider when understanding hot melt adhesive nozzle applicators. Review all of these in order to deliver the correct amount and pattern of glue for the products you are gluing.

Gluing pattern: Choose from bead, slot or spray pattern, depending on your application

Number of orifices: Single or multiple for adequate coverage

Style of gun: Verify that the nozzle you are choosing is compatible with your gun

Nozzle angle position: Straight or right angle are the most common, but make sure whatever you need suits your application gluing process

Orifice diameter: .008” for reduced flow up to .040” for high flow

Engagement: The length of orifice channel — nozzle seat to nozzle tip

For more information on nozzle engagement, please call (800) 848-5018 or email Universal Systems SE is offering FREE nozzle cleaning kits through the end of June for new clients. Take advantage of this free gift when you order 20 or more nozzles.

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