Cleaning the adhesive application system properly

21. December 2023 6 min.

Robert Seiferth, Technical Account Manager and Trainer at Robatech Germany

Contamination and deposits in the adhesive application system are the most common causes of malfunctions. To counteract this, it is important to keep the whole system clean at all times. In this blog, you can learn how to easily clean your adhesive application system to ensure smooth operation, extend its service life and achieve optimum application quality.

Sauberes Schmelzgerät Easy: Blick ins Tankinnere

The cleaning requirements of an adhesive application system depend, among other things, on the type of adhesive system, its use and the ambient conditions. Generally speaking, the shorter the throughput time and the lower the processing temperature of the hot melt adhesive, the lower the risk of deposits in the system. Factors that lead to the need for more frequent cleaning of the equipment or system include:

Changing of the type of hot melt adhesive
High processing temperature
High processing volumes
Use of hot melt adhesives with low thermal stability
Dusty production environment

CLEANING THE ADHESIVE APPLICATION SYSTEM: WHEN IS THE RIGHT TIME?

When is the best time to clean or maintain your adhesive application system? It depends. The question is: How important is the constant availability of your adhesive application system?

The more important system availability is to you, the sooner you should take preventive measures to protect your system from possible failures. However, if system failure has a relatively small impact, for example because you have a replacement system, then things are different. In this case, preventive maintenance may be too time-consuming or too expensive for you.

However, it's never good to wait until the machine comes to a standstill, as this risks major damage. For example, coking can cause heated hoses to become so clogged that they can no longer be cleaned and need to be replaced. Or, if adhesive spills around the tank opening during filling and is not removed, it can flow along the tank wall into the inside of the unit, forming lumps of adhesive. If the overtemperature switch is glued, the system switches off. And this means one thing: time-consuming repairs.

Adhesive melter without hood. Clumps of adhesive adhere to the outside of the adhesive tank Lumps of adhesive on the outside of the adhesive tank cripple the entire system

I recommend that you regularly use maintenance windows and other downtimes for preventive cleaning. Look at the following points, and then decide when is the right time for you.

Optical state of your system: Is it free of dust and adhesive residues?
Error messages: Turn on system messages to be reminded to clean or check filters, hoses, and nozzles.
Changes in adhesive flow: The adhesive measuring system AMS (Adhesive Measuring System) provides you with information that indicate, among other things, blockages of adhesive filters in the adhesive melter or application head or of the application nozzle.

WHAT TO CONSIDER WHEN CLEANING YOUR ADHESIVE APPLICATION SYSTEM

Once you have worked out when to clean, the question is how to do it. I am often asked what cleaning agents should be used to clean an adhesive application system. Normally with none at all! The most important thing – and you don’t even need a maintenance plan for this – is to keep your appliances clean on the outside. This means wiping any adhesive residue on the nozzle of the application head regularly with a lint-free cloth or paper, cleaning the tank lid, and keeping the environment free of dust and dirt. And remember: systems that have obviously not been cleaned lose their warranty entitlement.

Dirty Vision adhesive melter External cleaning is particularly important in a dusty environment

CLEANING THE ADHESIVE TANK

Check your adhesive tank regularly. If the adhesive is clean and clear, everything is fine – you don’t have to do anything. But if the adhesive turns dark or you notice dirt – even if it’s just poppy seed-sized dark spots floating in the liquid adhesive – it’s time to clean the adhesive tank. To do this, the entire adhesive must be drained. It is therefore advisable to do this at the end of the shift when there is little adhesive left in the tank. Adhesive residues in the adhesive tank can usually be removed with a wooden scraper and a lint-free cleaning cloth.

White adhesive granules on yellowish adhesive surface The darker the discoloration of the adhesive, the more necessary cleaning is

Fabric adhesive filters can be placed in heated technical white oil if they are heavily soiled. This melts the adhesive so that it dissolves from the filter. Robatech uses a deep fryer with two separate containers: one for pre-cleaning and one for final cleaning. Filters made of sintered bronze cannot be cleaned in this way and must therefore be replaced.

After cleaning the adhesive tank and filter, you can fill the system with new hot-melt adhesive. A cleaned adhesive tank with a clean filter is a prerequisite for the subsequent cleaning of the heated hoses and application heads.

CLEANING THE HEATED HOSE

A heated hose can only be cleaned by rinsing with new adhesive. Rinsing replaces the old adhesive with the new adhesive. No cleaning agents or any tools are necessary. Never drill into the heated hose with foreign objects!

Reduce the temperature in the adhesive tank and heated hose by about
20° C. As a result, the adhesive becomes tougher and better absorbs dirt and coking.
Feed clean adhesive through the hose until the adhesive flows clear out of the heated hose.

Cleaned heated hoses last longer

Rinse the heated hose regularly – e.g. once a year as part of a full clean of the entire adhesive application system. It doesn’t take more than 10–15 minutes. On the other hand, if you don’t, coking can take hold inside the hose, and the hose diameter becomes smaller. . When there is not enough adhesive flowing through the hose, the operator often increases the pump pressure. However, this only provides a short-term remedy. Then they raise the temperature so that the adhesive becomes thinner and flows again. But the problem is that it burns even faster. Instead of solving the problem, they exacerbate it.

CLEANING THE APPLICATION HEAD

The application heads can also be easily rinsed with clean adhesive. First, remove the heated application nozzles and filters and clean them. Gently insert the cleaning pin into the hole of the nozzle to remove dirt. Remove adhesive residue from the outside of the nozzle with a fine abrasive or insert the nozzle in hot cleaning oil. Then blow out the application nozzle with compressed air.

Left dirty application nozzle, right cleaned application nozzle Cleaned application nozzles ensure perfect application

Like the nozzle, you can insert the adhesive filter of the application head into hot cleaning oil, but never together! This is because the coarse dirt particles that are released from the filter should never get into the thin hole of the nozzle. It could clog up otherwise.

Left new adhesive filter for application head, right charred adhesive filter With such a heavily charred filter, cleaning is no longer worthwhile. It can be replaced.

CONCLUSION

As you can see, some simple cleaning can have a huge impact on the lifespan and availability of your adhesive application system. You're in control. You don't need sophisticated technology; all you need is common sense and the wisdom to use the available opportunities efficiently. What do you think?

Robert Seiferth, Technical Account Manager and Trainer at Robatech Germany

Robert Seiferth is a Technical Account Manager and Trainer at Robatech Germany. For the past 12 years, he has overseen the service hotline, supporting customers from a wide range of industries with technical problems. He passes on his know-how to customers in user training courses.