1. Focus on the heat tunnel, with an eye to throughput. A properly functioning heat tunnel is the key to successful long-term operation. Heat tunnels are more than simple caverns with a conveyor where heat is applied; they are highly engineered machines, and each is specifically designed to meet the unique packaging line conditions. It is virtually impossible to create an apples-to-apples comparison of heat tunnels from different manufacturers based solely on specifications because the heat shrink process is too complex. Look instead at throughput. In specifying machinery, require a written commitment of throughput efficiency while evaluating machines. You’ll likely choose a vendor who commits to a 99.5% throughput efficiency vs. another that claims 85%. However, it’s just as important to specify that the throughput rate must be confirmed prior to placement of the order.
2. Always consider size and shape. Package size and shape are two critical production variables for specifying heat shrink label equipment. For example, the shrink characteristics of a film label for a straight side-walled container will be different from an hourglass-shaped package. The equipment supplier must take shape and size into consideration when designing the system.
To achieve lowest total cost of ownership, the brand owner should determine whether the size and shape of the package might change in the next three to five years. If change is likely, provide the equipment supplier with enough information to design a system today that incorporates the flexibility to accommodate changes tomorrow.
3. Don’t forget material composition. The material composition of the package also affects the design considerations of the shrink label solution. For example, a glass jar can absorb more heat than a PET one and various compositions of PET handle heat differently. With all the effort to make packaging more sustainable, brand owners are light weighting and using materials with greater recycled content. These changes may affect the shrink label process. Look three to five years ahead and envision potential changes to the composition
of the package. Work with the equipment manufacturer to include the flexibility needed to accommodate a range of materials.
4. The need for speed. The speed of the line impacts the configuration of the applicator and heat tunnel. You should identify the machine with the greatest throughput upstream of the sleeve applicator and heat tunnel, and then determine tunnel throughput based on that speed. Engineer the shrink label process to have 20% higher throughput so that it can serve as a buffer. You should also plan for scenarios that call for higher-speeds over a reasonable time period, even three to five years, to reduce total cost of ownership.
5. Take care with film selection. Every type and formulation of shrink film, whether PET-G, PLA or PVC, has its own shrink characteristics. A film’s specifications and cost are only starting points in the selection process. How that film will conform to the size and shape of the package at the line speeds required is a function of actual conditions in the heat tunnel.
For example, simply assuming that the label will shrink uniformly may not be correct; dark colors on a label absorb heat more quickly than light colors. Certainly, you may wish to start out with a first choice for a film, but work with the equipment manufacturer and film supplier for package lab testing prior to making a final decision on film choice.
6. Buy a service contract. Shrink labeling is a process that needs to be maintained within precise parameters. Having a service technician visit the plant on a regular basis to adjust the process, replace worn components, and provide ongoing training for operators pays dividends in terms of less downtime and waste as well as high throughput.