Filling the adhesive tank correctly is crucial – yet mistakes are often made here. Filling too much adhesive at once is particularly problematic. This is often done in an attempt to save time. However, melted adhesive should only remain in the tank for as long as necessary, otherwise it will burn. In addition, too much adhesive can overflow and burn on the outside of the tank or – even worse – flow into the interior of the melter and damage the electronics. If the overtemperature switch fails, the adhesive melter is shut down and the entire production line may come to a standstill. What was intended to save time then ends up in costly repairs and production downtime.
Another risk associated with overfilling is the drop in temperature in the tank: if too much adhesive is added at once, the adhesive melts unevenly, leading to application errors. On the other hand, the adhesive also burns on the inside wall of the tank because that is where the temperature is highest. And burnt adhesive – as we know – causes clogging in the long term.
However, the opposite – refilling too little adhesive at a time – is also problematic. If you constantly run the tank almost empty, you have to refill more often, which costs time and interrupts the production. In addition, too small an amount of adhesive burns faster, which in turn leads to clogging in the system.
The right balance is therefore crucial to ensure smooth and reliable adhesive application.
How to optimize:
When the adhesive flow decreases, it’s tempting to turn up the adhesive pressure or the temperature slightly to get more adhesive out. But this is never the right move. The adhesive pressure is usually not the cause of the problem. Nor is the temperature – if it is set to the optimum, it should not be changed at random. Most often, the issue lies with clogged filters or nozzles, or mechanical wear in the solenoid valve or jetting element. Increasing the temperature above the optimum value causes the adhesive to decompose and increases the risk of clogged nozzles and poor adhesion.
How to optimize:
The optimum application temperature depends – of course – on the adhesive. Always refer to the adhesive manufacturer’s data sheet! As a rule, one can say that the higher the temperature, the lower the viscosity and elasticity of the hot melt adhesive. And the lower the elasticity of the adhesive, the less stringing occurs when the adhesive is applied.
In addition, I recommend heating the adhesive gradually. This protects the adhesive and reduces wear on the system because less charring will occur. For this reason, it is important to set the temperatures of the three heating zones individually. The following heating zone temperatures serve as a reference, but they can vary depending on the amount of adhesive consumption and application.
Proceed step by step when adjusting the settings, as even differences of 1 to 2 °C can change the viscosity of the adhesive. And be sure to have the heating zone temperatures confirmed by an expert!
How to optimize:
Every minute that the adhesive is kept at full operating temperature in the system increases the risk of problems. If the melted adhesive is heated and left standing for a long time, it begins to decompose. Stringing and discoloration of the adhesive are the first signs of this. The adhesive becomes thicker, the adhesive pressure decreases, the adhesive begins to burn, and coking clogs the heated hoses and application heads.
The good news? Robatech systems are equipped with a temperature standby function, which reduces the temperature in the adhesive melter during an interruption without switching it completely off. Restarting after an interruption therefore does not last long.
How to optimize:
Read more in this blog post about how to avoid charring with the temperature reduction function.
Contaminated adhesive is a major cause of downtime. Even tiny particles – which can come from picking up spilled granules from the floor, for example – can clog filters or even destroy gear pumps.
Storage matters too: open bags in dusty environments increase the risk of contamination, and excessive temperatures or humidity can impair the adhesive’s performance. Please refer to the information on the adhesive manufacturer's data sheet. There you will also find the expiration date, after which you should no longer use the adhesive.
If you want to change the adhesive, it is very important not to mix the two different adhesives. Even different batch numbers can sometimes cause problems.
How to optimize:
As you can see, small changes in how you handle hot melt adhesive can make a big difference. Ensuring that the rules discussed here are followed will definitely increase the uptime of your machine. Regular cleaning and proper maintenance will further enhance the availability of your systems.
Do you need support optimizing your hot melt system? Robatech experts are available worldwide to provide training, consulting, and expertise to find solutions tailored to your operation.