Do you run different makes or models of flow wrappers or vertical form-fill-seal baggers?
If you do, you probably use a variety of knife and sealing jaw styles that you need to keep in stock. With different knife or sealing jaw designs, the seal quality and appearance of your packages may vary, depending on which machine, line, or facility produced them. Read more
This Greener Tech Bite, with the help of our partner Kenray Forming, explores six key design and set-up principles to help you identify the source of forming and sealing problems and develop solutions for quality packages. Read more
When cutting problems occur on horizontal flow wrappers during a production run, what are the best procedures to get packaging lines up and running again and to keep them running? Minimizing downtime, producing consistent quality packages, and managing costs require a balanced approach that includes:
There is no one-size-fits-all solution for the design of crimpers and sealing jaws on horizontal flow wrappers and vertical baggers; they should be specified according to the packaging film, products, and conditions of your packaging operation.
This post, the last in our four-part series, reviews design options for crimpers and jaws. The optimal combination of serration patterns, materials, and special features can dramatically improve seal quality and productivity when sealing across extra film layers at the end seal. Read more
The first two parts of this series explored the potential problems created by end seal wrinkles and creases and ways to eliminate or reduce them on horizontal flow wrappers (Part 1) and vertical baggers (Part 2). In some situations wrinkles or creases are unavoidable, and, even without those issues, most packages have the inevitable transition between multiple film layers created by either a fin or a lap seal. This can make it more difficult to achieve quality seals, and attempts to do so can lead to additional issues:
• Excess pressure can easily crush or split the end seal.
• Overheating distorts the seal and can cause poor hot tack, where the film springs back open, or “moons,” before the seal can set.
The operating window for creating quality seals can be elusive, resulting in packages that leak or are distorted and either fail to protect the product or have little appeal to consumers.
This post reviews some of the detailed solutions in Greener Corporation’s Knowledge Center that will help you seal over extra layers of film at the end seal by refining the set-up and adjustment of crimpers, sealing jaws, and knives.
Varying thicknesses of film at the end seal can cause sealing problems, especially at the transition point between two and four layers created by the fin seal, gussets, wrinkles and creases, as well at the corners. Applications of pressure and heat (if applicable) must be great enough to cause the sealant layer to flow into and seal off these voids. Excess pressure can easily crush or split the end seal, while overheating distorts the seal and can cause poor hot tack, where the film springs back open, or “moons,” before the seal can set.
The operating window for creating quality seals can be elusive, resulting in packages that leak, are distorted, and have little appeal to consumers.
An important step in troubleshooting these issues is to eliminate unintended wrinkles and creases. This post, the first in a four-part series, will examine this process on horizontal flow wrappers; Part 2 considers these issues on vertical baggers.
When end seal issues such as leakers or splitting occur, an important initial step is to determine where, and how often, the trouble shows up. For problems that occur inconsistently—perhaps leakers on every other package, or splits only on the top or trailing end seals of the package—you need to determine if the bad seals show up randomly or according to a pattern. Do the problems occur on every package? On both ends of the package?
Start out by collecting a series of packages produced by the machine during production conditions. Number the packages sequentially and mark the machine flow direction. If you are working on a horizontal wrapper with multiple crimpers, label each pair (ex: A, B) and mark each seal according to the set of crimpers it came from. Now you can trace the problem seals back to the place they occur.
Set-up procedures for knives and anvils can vary according to the make and model of the packaging machine, knife adjustment style, and other factors. There are, however, some general principles that make these adjustments more effective and efficient, reducing downtime and parts costs.
♦ Optimize Knife Design
- Knives ground on a diagonal, or bias–whether they have a zig zag or a straight cutting edge—require less pressure to cut so they are easier to set up and typically last longer.
- Zig zag knives with smaller (more) teeth are also easier to set up and provide longer life.
♦ Set Up the Crimpers First
For heat seal applications, each packaging film structure has a Seal Initiation Temperature (SIT), at which the sealant layer is heated enough to flow into and seal off gaps in the end seal and provide a minimally acceptable seal, and a Maximum Temperature, beyond which the film distorts, fractures, or has inadequate hot tack (seal strength and integrity while the seal is still warm). The temperature range between the minimum and maximum is the film’s Operating Window.
For a number of reasons, regulating heat is not as straightforward as simply adjusting the temperature setting within the operating window for the film you are running.
♦ The sealing face of crimpers and sealing jaws is often hotter in the middle than at the ends, where heat dissipates more quickly. These inconsistencies are readily apparent in the thermal profile shown below:
Stainless Steel Crimper Thermal Profile