The High Cost of Old Technology
One of the biggest weaknesses in many traditional and legacy hot melt adhesive systems lies in the melting process, which relies on tanks to heat the adhesive. This "crock pot" style of tank not only takes a lot of time to heat the material, but also generates adhesive char that leads to plugged hot melt nozzels and equipment failure.
Some new hot melt systems utilize specially-designed heating chambers with a significantly improved surface to adhesive ratio for fast, efficient melting. Buyers must educate themselves in order to ask tough questions and make sure they are getting reliable, efficient equipment that will drive profitability over the long term.
Six questions to ask when buying equipment
Before making a hot melt equipment purchase, be sure to ask these questions:
1. Is the machine reliable, or is the supplier more interested in selling spare parts?
2. Is adhesive charring an issue?
3. What about hot melt nozzle plugs?
4. What's the ROI over the long term?
5. Is adhesive tracking built-in as a standard feature?
6. Is the equipment safe for my operators?
It is not always clear if a system is truly Tank-FreeTM as some suppliers market their equipment as "tank-less". For example, in Figure 1, the image on the left is from a system billed as tank-less, while the melter shown in the bottom image is clearly an example of Tank-Free technology.
Viscosity variations and wasted hot melt adhesive
Viscosity changes can result in poor adhesive performance and fluctuations in the amount of adhesive dispensed. If too much glue is dispensed, material is wasted and money is left on the table. If too little is dispensed, there will be pop opens which could lead to scrap or returned product.
Some newer hot melt technologies available today use an integrated vacuum system to feed hot melt adhesive to the melter. With this approach, an ultrasonic sensor constantly monitors adhesive in the chamber. Additional adhesive is automatically added as needed, depending on the application's demands. Material is added at a rate of only about one-quarter cup at a time, eliminating thermal shock to the molten glue that could directly result in problematic viscosity changes.
These integrated vacuum feed systems also save labor costs, as it doesn't depend on anyone to keep an eye on adhesive. The system automatically keeps adhesive at optimum levels while keeping heat in, and dust and debris out. It also promotes consistent bead weights by eliminating thermal shock.
Surface area to adhesive volume ratio
The high surface area to volume ratio found in Tank-Free hot melt adhesive systems is responsible for the decreased charring and minimal startup times. By eliminating heated tanks and increasing the melting surface, hot melt equipment performance improves dramatically. The higher this ratio is, the lower the likelihood of charring and shorter the startup time will be.
When systems aren't dependant on a tank, adhesive pellets can be melted on demand and then dispensed quickly, which greatly reduces char and material degredation caused by prolonged exposure to heat.
Adhesive char and hot melt nozzle plugs
While traditional heated tanks store anywhere from 4-50 liters of adhesive material, Tank-Free designs heat less than two liters of adhesive at a time, which means the adhesive is brought to temperature more quickly - under 10 minutes in most cases. This decreased startup time makes a great difference in uptime and yield over the course of a hot melt system’s lifetime, and therefore translates directly into greater profitability.
The shortened exposure of the hot melt adhesive to heat in vacuum-based Tank-Free systems also reduces the amount of char formation within the system. With a minimal melted volume, hot adhesive spends less time at temperature and is quickly replenished with a fresh supply. Reducing char also reduces material waste and nozzle plugs leading to less overall system maintenance and less production line downtime.