Hot-melt adhesives have played a key role in the packaging process for decades, but traditional technology using heated tanks is less efficient when compared to new systems available today. Traditional melters are more likely to require char-induced maintenance than systems that do not incorporate tanks. Unplanned downtime and lost production due to this maintenance can cost businesses thousands of dollars each year.
New technology has eliminated many of the drawbacks of the previous generation of hot-melt adhesive equipment. This increases the working uptime of packaging lines and improves the efficiency of hot-melt adhesive applications. Advances in material usage monitoring and system performance result in better management of adhesive costs.
Package and container sealing is a key component of today’s complex manufacturing processes. Manufacturers require a system that quickly delivers consistently applied adhesive that can fit into streamlined packaging lines. Many companies turn to hot-melt adhesive delivery systems for their packaging needs.
Traditional hot-melt systems feature heated tanks; however, their limitations impact the efficiency and cost effectiveness of packaging lines. These limitations include long startup times, adhesive charring and contamination, nozzle plugging, and potential danger or discomfort to operators.
Heated tanks are slow to warm up to the point where they are ready for use; they can take more than 35 minutes to heat adhesive to operating temperature, which leads to packaging facilities spending more time waiting for the system to heat up and less time in operation. In addition, tank systems maintain large volumes of molten adhesive for hours or days at a time, and the level of molten glue tends to vary widely. These long heat soaks and varying molten glue levels lead to charring, or overheated and burned adhesive. The adhesive on the side walls, exposed to the atmosphere, chars very quickly. The charred material causes plugging in nozzles and requires routine cleaning, leading to downtime on the packaging line. This excessive charring can also lead to premature failure of fluid seals in pumps and guns.
Nozzle plugging represents one of the most problematic elements of traditional tank operation. Plugs cause unplanned downtime and are thus quite costly. As a plugged nozzle typically must be repaired when hot, maintenance to remove nozzle plugs can be a dangerous task.
In addition to unplanned maintenance due to nozzle plugs and other issues, heated tank systems require routine cleaning and maintenance to avoid excessive char buildup. These cleanouts can be labor and time intensive, further impacting production line uptime. Large tank sizes result in a significant amount of wasted material whenever flushing is necessary. As a result, cleaning and routine maintenance are costly to packaging operations, but are necessary when using heated tanks. Filling, cleaning and performing maintenance on traditional hot-melt tanks puts operators in close proximity to hot adhesive and hot system components, and, again, may be dangerous. Even when operators are not injured by heated tank systems, the smell of hot and charring adhesive is frequently unpleasant.
Finally, the traditional tank systems do little to protect against contamination of hot-melt adhesive. Environmental exposure, combined with the continual need for manual filling, allows dust and debris from the facility to enter the tank. Foreign material reduces adhesive effectiveness and increases the chance of nozzle plugging.
Recent advances in hot-melt equipment technology, however, have dramatically improved upon the overall efficiency of traditional adhesive systems. The elimination of heated tanks, increased attention to material consumption statistics, and a focus on reliability has limited or removed many of the drawbacks of the previous generation of hot-melt adhesive dispensing systems.
One of the most apparent weaknesses of traditional hot-melt systems lies in the tanks themselves. As described, these tanks take a lot of time to heat material, generate adhesive char, and expose operators to potentially dangerous hot adhesive.
Systems that do not incorporate these tanks instead use a vacuum feed to draw adhesive pellets into specially designed heating chambers (see Figure 1). Pellets are melted on demand and are dispensed quickly, without overheating. The elimination of heated tanks dramatically improves hot-melt equipment performance. By reducing the amount of adhesive exposed to heat, this process allows for faster heating times.
For instance, one tankless system can warm adhesive to operating temperature in less than 10 min.** This is due to the greater surface area to volume ratio—a measure that compares the heated surface area in a melter to the adhesive volume contained in that melter. In this case, more surface area with less volume—a larger ratio—indicates the system will warm up faster and melt adhesive quicker. While traditional heated tanks store anywhere from 4 to 50 L of adhesive material, tank-free designs heat less than 2 L of adhesive at a time. Decreased startup time makes a great difference in production 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 adhesive to heat in vacuum-based tank-free systems also reduces the amount of char formation within the system. Quite simply, less time at temperature results in less adhesive char. With a minimal melted volume, hot adhesive is dispensed quickly and replenished with a fresh supply. The reduction of char leads to less material waste, fewer nozzle plugs, less overall system maintenance, longer fluid seal life and less production line downtime.
All of these benefits spell out improved operator conditions as well. With a tank-free system, an operator no longer has to hand-fill hot-melt pellets and the task of tank scraping is eliminated. The elimination of the heated tank and reduced operator interaction with the system decreases the chance of burns and other injury, while reduced odor provides an overall better operator experience.
Finally, the use of a vacuum feed system keeps the ambient adhesive contained and closed from the outside environment. This dramatically reduces the chances of material contamination. Barring contaminants from the adhesive improves the dispensing process and helps to ensure consistent adhesive application.
Traditional hot-melt tank systems lack intelligence in terms of adhesive usage monitoring. This information is vital to tracking expenses related to the packaging process. With adhesive costs at the forefront of the manufacturing industry’s mind, monitoring solutions are becoming increasingly more important.
Emerging hot-melt technology offers the detailed adhesive usage information many manufacturers desire. For example, one system incorporates an intuitive user interface and USB downloadable operating data, making it possible to clearly track material usage throughout a given period of time. This allows packaging managers to examine the amount of adhesive used over a single shift, a product run or other set amount of time. The increased tracking information leads to improved record keeping, better understanding of adhesive consumption and needs, and better control over costs in the packaging process.
In addition to adhesive consumption, operators have the ability to track a number of other important factors, including fluctuations in adhesive temperatures, system errors and key event history. This information is invaluable, as running routine reports can pinpoint inconsistencies in the process, optimize the packaging line and identify cost saving opportunities. The process control and reporting data that the customers of many packaging companies are demanding is now available with this monitoring technology. Add in remote monitoring, and plant managers and operators can have access to all of this operational data and more from anywhere in the world.† Manufacturers have access to hot-melt equipment and adhesive data that allows them to make decisions that control costs and improve efficiencies in real time.
Increased Adhesive Options
Some packaging companies find themselves transitioning to more expensive, temperature-stable adhesives in an attempt to negate some of the drawbacks of hot-melt tank equipment. While these adhesives have value to offer in their own right, adhesive choice should not be dictated by the capability of the processing equipment. Some new tank-free hot-melt systems have been designed around the broad spectrum of adhesives traditionally used in the packaging market. In those cases, all packaging-grade adhesives are available for use, including metallocene, EVA and others, expanding the options for packaging managers.
In addition, adhesive materials once viewed as incompatible with traditional heated tank systems due to their brief pot life stability or tendency to char have now become viable options for use with tank-free systems. The viability, and often increased affordability, of these materials further expands the number of adhesive options accessible to the manufacturer.
The expansion of viable adhesive options and more efficient adhesive use may lead to reduced adhesive costs. By exploring additional adhesive options, packaging managers may find savings in both the cost per pound of inventory ordered and the actual amount consumed per unit produced.
Traditional hot-melt adhesive dispensing systems, while playing a large role in the packaging process, suffer from inefficiencies and weaknesses that can impact the effectiveness of the line. Emerging tankless technologies eliminate many of the drawbacks of traditional heated tank systems and vastly improve the efficiency of the packaging process. The advancements in hot-melt dispensing technology offer many potential benefits for manufacturers and packaging managers, including reduced downtime, lower adhesive costs, improved operator experiences, and improved information management. These improvements over heated tank systems have generated a dramatic ROI for many companies using tank-free hot-melt delivery systems.
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