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.
Transitions on the end seal between varying thicknesses of film created by the fin seal, lap seal, gussets, and wrinkles make it more difficult to maintain the operating window necessary for quality seals:
- Too little pressure leaves gaps, or leakers, at these transition zones.
- 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 at transition zones or “moons,” before the seal can set.
The end results can be packages that fail to protect the product or have little appeal to consumers, as well as lost production time spent attempting to meet package quality standards.
Crimper and Sealing Jaw Design Options
What combination of serrations patterns, special options, and materials will perform best for your packaging application? Start by identifying problem areas and unmet goals. Your objectives might include:
- Reducing or eliminating end seal leaks
- Preventing crushing or splitting at the end seal
- Improving package appearance
- Increasing line speeds
- Decreasing downtime associated with package quality issues
- Achieving quality seals where different package sizes and styles, or different films, are run on the same machine
Crimper and sealing jaw design, as well as the consistency and quality with which they have been manufactured, have a major impact on the distribution of the pressure and heat necessary to achieve quality end seals across varying thickness of film. The optimal design depends upon the unique combination of variables of your packaging operation, such as equipment design and condition, product, packaging film, and line speeds.
Sealing pressure is applied by the force of the crimpers or jaws coming together with the film between them, and controlled through machine adjustments. In addition, as the film is drawn across and stretched over the serrations, the resulting “shearing” action helps push the inner sealant layer into gaps that would otherwise cause leaks.
The precise geometry of the serration pattern should be matched to the structure and thickness of the film in use, the presence of a lap or fin seal, gussets, persistent wrinkles, and other factors such as machinery design and condition and line speeds.
Special Design Features
A number of special designs for crimpers and sealing jaws work in combination with the proper serration pattern to provide more consistent, controlled pressure across end seals by accommodating extra layers from a fin or lap seal, gussets, or unavoidable wrinkles.
Flexible Sealing Faces
Easy Seal Flexible Inserts conform to extra film layers, allowing crimpers to apply the consistent pressure and heat (where applicable) required to effectively seal gaps at transition zone between varying thicknesses of film without distorting the package. These flexible, durable sealing faces can be provided for heat seal or cold seal applications.
Easy Seal Quick Change Inserts facilitate the precision serration alignment necessary to apply sufficient pressure across multiple thicknesses of film at the end seal without crushing or splitting the package, and at the same time reduce crimper changeover time from hours to minutes.
A precision relief in the serration pattern can be provided to accommodate the extra layers of film from the fin seal. A fin seal relief works best on applications where the fin seal size and tracking is consistent.
A special serration profile on the leading edge of the crimper sealing face helps eliminate excess pressure that can damage or cut through the packaging film.
New design solutions can be created to match your production needs or for special projects such as new film qualifications, changes in package size, and cross-platform crimper standardization.
Optimizing the materials that crimper and sealing jaw materials are made from helps produce the consistent pressure and heat transfer (where applicable) necessary to achieve quality seals.
Wear and damage to the sealing faces of crimpers and sealing jaws can make it challenging or even impossible to transfer the proper pressure and heat across the end seal. This wear may not be readily visible on the sealing face, but becomes obvious when crimpers or jaws are evaluated using carbon paper (as shown). For more details see Assessing Crimper and Sealing jaw Set-Up.
Crimper and sealing jaw materials that resist wear and damage can be specified to match the variables of your packaging operation, for flexible or standard sealing faces and for heat seal or cold seal applications. There is no need to sacrifice durability in order to achieve quality seals.
Heat: Consistency and Responsiveness
On heat seal applications, heat and pressure work together with time to produce quality seals. (For more details see Basic Sealing Theory.) Consistent, responsive heat transfer across the length of the sealing face eliminates the need to increase temperature and pressure settings to the point where the film is distorted or crushed in order to seal gaps between varying thicknesses of film on the end seal. The crimper and sealing jaw set-up required for achieving quality seals and meeting production goals becomes much easier to establish and maintain.
Crimpers and jaws made from Dura-Therm provide the consistent temperature profiles and the long-term durability necessary for sealing across extra layers of film at the end seal. (For more details see our post on Heat.)
Optimizing Crimper and Sealing Jaw Design
The best design for your crimpers or sealing jaws depends on the operational goals of your packaging operation. Taking a little time to evaluate your needs is a worthy endeavor that can significantly improve package quality and productivity.
Greener’s technical experts can help you refine your goals and determine the solutions that will accomplish your objectives. If you would like assistance with this process or have questions, please contact us. For additional information please visit our website.