comparing rf with other sealing technology
With RF sealing, everything between the upper and lower dies heats evenly, at least in theory. In actual use, however, the dies heat-sink the plastic on contact, such that a temperature profile would indicate the hottest spot is at the interface of the two materials. This works to great advantage in bonding, since the interface is where the most heat is required.
Other methods, such as thermal, impulse (a switched thermal), or ultrasonic sealing, do not share this advantage. For example, temperature profiles taken during thermal and impulse processing indicate that the hottest spot is where the dies touch the outside of each layer of plastic—a condition that often causes degradation of the outside of each layer before the interface reaches melt temperature. (Thermal and impulse sealing functions best with certain very thin [<0.006 in.] films and with polyethylene, polypropylene, or polystyrene.) Ultrasonics, on the other hand, works like a jackhammer, pounding the plastic from 20,000 to 40,000 times per second, with the resulting friction creating heat and thus melting the plastic. Again, the temperature profile is less desirable than that with RF. These alternative processes are limited in area of seal, lack repeatability of acceptable seal quality, and do not have the ability to produce tear seals. They are often employed in small-area spot sealing or in applications for which product appearance is not important, such as polybagging or tack sealing to locate parts.
Few products are as well suited for a particular manufacturing process as are medical bags for RF sealing. No other bag-sealing method yields the consistency, capacity, and quality afforded by RF technology. Depending on the type of bag produced, the required quantity, the manufacturing environment (e.g., labor costs), and the unit price, there are several processing options available to the RF sealer, ranging from completely manual to fully automated techniques.
In addition to choosing the most efficient RF sealing technique for a particular job, bag makers should work with reputable RF companies to ensure the proper design of equipment and tooling. It is also important to remember that RF interference can affect many sensitive electronic devices within a manufacturing facility, and appropriate shielding meeting or exceeding OSHA, IEEE, and FDA regulations should be verified during equipment selection. The fact that, in many cases, data feedback from sealing equipment can help validate the manufacturing process and eliminate costly product testing is another important consideration.
Although RF sealing is a long-established technology, new product developments and option packages have solidified its performance, reliability, and safety. At first glance, RF sealing may seem complicated—the term "black magic" has even been used to describe it. However, RF sealing merely obeys the laws of physics, and is in fact a predictable, dependable, and robust manufacturing process.