TOSS Alloy-20® Straight and Contour Impulse Heat Seal Band Selection
TOSS Alloy-20 impulse heatseal bands are available in over 350 styles, shapes and sizes. Custom designed for any application, new or existing, TOSS Alloy-20 bands are longer lasting and provide for effective sealing at optimum speeds. TOSS’s Norex® impulse heat seal bands are ideal for sealing applications requiring a minimal amount of heat seal band expansion.
Impulse Heat Seal Band Variables
Ideal impulse heat seal band selection is a function of many variables including material composition, material thickness, heat absorption of the jaw, and the nature of the cover strip used over the heat seal band.
In general, the thicker the material to be sealed, the thicker the heat seal band that should be used. Most materials, 1 mil to 6 mil can be sealed efficiently with heat seal band in the thickness range of 0.1 mm to 0.25 mm. With very thick seals (multi-layers to totals of 15 mils or more) it may be well to use thicker bands or consider the possibility of applying heat from both sides.
Custom Contoured Impulse Heat Seal Bands
Most believe that impulse heat sealing is limited to straight seams, which is simply not the case. In fact, with TOSS Technology, special shapes can be created to meet your unique sealing needs.
You can design and develop almost any configuration for sealing plastic films and thin thermoplastic parts. Complex shapes with multiple-power feed tabs for equal heat distribution can be developed to meet your needs.
Have TOSS supply your custom contoured heat-sealing elements or engineer your entire heat sealing system.
Plating of TOSS Alloy-20 Impulse Heat Seal Bands
Plated impulse heat seal bands are subjected to both physical and thermal stresses caused by the repeated heating and cooling of the band and attendant expansion and contraction. This condition is exaggerated at or near the ends of the bands.
The "effective" portion of the band (the portion that is in contact with the work piece), will have heat drawn away by virtue of its contact with the relatively cool work piece. Conversely, the portion of the band that is not in contact with the work piece will tend to overheat. If the heatseal band creates a gap between the end of the Jaw Bar and the Jaw End Block, a small portion of the band will get very overheated.
This is a very common occurrence in bands that are not protected by the addition of a copper-plated heat sink at and near the ends of the band. Band breakage most commonly occurs near the end of the band.
Impulse heat seal band replacement and the machine operator’s down time can be substantially reduced by adding copper plating to the end of the band. Further, operating efficiency and band life can be prolonged by adding additional copper on the band that extends at least 0.25" into the "effective" portion of the band.
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Heat Seal Band Cross-Sections
Selection of the best Heatseal Band for any given application involves several considerations. The band must be of the correct width and configuration to produce the desired seal or cut/seal. In addition, the band must be thick enough (have sufficient mass) to store the heat energy required for delivery to the material being sealed.
When creating an impulse seal, it is desirable to terminate the heating cycle as soon as possible and begin cooling. Remember, the seal is not finally made until the seal area is cool enough to be dimensionally stable. If the Heatseal Band is too thick or the heat energy delivered is too great, the cooling time will be prolonged, thus prolonging the total cycle and limiting production rate.
The common Flat Band is an old stand-by configuration that was originally developed to make seals with widths wider than that which could be made with round wire. In most applications, the Flat Band has been replaced by the Tapered-edge Band or the Reflex Band. The Flat Band has the major disadvantage of sharp square edges that cut into and weaken the film along the edge of the seal. Failures of this kind are called “zipper failures”; the seal itself is well secured and appears good, but the package is dangerously weakened.
This band, usually called Tapered Band, is the contemporary version of the Flat Band. On this band the edges have been tapered down to a very thin edge. This produces two advantages. The tapering removes the sharp outer edge that cuts into the film while heating. It also acts to reduce the temperature of the band along its outer edges. Without a tapered edge the band will cut into the film along the edge of the seal and weaken the package.
This is an excellent band for thick materials, hard to seal materials, and vacuum packaging. Because of the convex configuration of the band, it only makes edge contact with the underlayment backing. This limited contact minimizes heat loss and provides more energy for the sealing of the film. The Reflex Band is also excellent for liquid sealing because the convex face acts to squeeze the liquid out of the seal zone as the seal is made.
The Double Seam Band is used to make two perfectly parallel narrow seals. Double seams, although rarely needed, produce the impression of greater integrity. They are useful in sealing liquids or other hard to seal materials.
This very popular band is used for cutting the film layers and concurrently sealing along both sides of the cut line. It is made with tapered edges as well and comes in a wide variety of sizes. The space behind the bead does not come in contact with the underlayment backing material. As a result heat is not lost from the beaded area; the bead becomes hotter than the adjacent edges, thereby, effecting a cutting action without overheating the sealed edges of the film.
This band, available in four (4) sizes, is made from solid extruded stock. It has a greater mass per unit of length than the Beaded Band and a sharper cutting edge. It is relieved in the back to minimize contact with its underlayment backing. This band retains its heat and is excellent for concurrently sealing and cutting multi-layers of film or thick film.
This special band is a combination of a Tapered Band and a Cutting Wire and is custom made to suit the specific needs of the application. The cut wire can be placed on the centerline of the band or along one edge, depending upon the desired result. (This technique of attaching a cutting wire can also be used on our TOSS custom contoured bands).
Round cutting wire is often used as an inexpensive means of cutting of polymer films, these wires are available in sizes from 0.3 mm to 1.2mm both in rolls and made up into pre-cut lengths with, or without, copper plating at the ends. As with bands, best performance it is obtained with brass end connectors brazed to the ends. When cutting through two or more layers, the layers of film will be sealed with a very narrow seal along the edge.
The Oval Profile Wire, available in two (2) sizes is larger in cross section than the round Cutting Wire. It is most useful for making narrow seals on thick or stacked materials. It is not very effective as a cutting wire.
Half round wire is another variation on the round cutting wire. Though rarely used, it is available in two (2) sizes and function much the same as the oval wire except that it has a better cutting action than the Oval Profile Wire.