Temperature and Time: Your Formula for Perfect Shrink Labels

2/5/2019

Achieving a perfect shrink on a sleeve label is often easier said than done. Even with a custom built system some experimentation may be necessary as you dial in the settings needed to achieve that all-important perfect shrink on your bottle, can or other packaging. Two of the primary variables to adjust are Temperature and Time; it is important to ensure they are in balance in order to achieve an acceptable final product ready for display and sale.

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Temperature

One of the advantages of air heated shrink tunnels is their wide temperature range. This offers another variable that can be altered to compensate for increasing line speeds, beyond simply extending the length of the shrink tunnel. The operating temperature of the shrink tunnel may need to be increased if labels are exiting wrinkled or with uneven shrinking. Or the temperature may need to be decreased if labels are tearing or over-shrinking.

The best temperature setting depends on a number of factors:

Sleeve material
Container material
Container contents
Line speed
Residence time
Tunnel design

Time

Heating time, or residence time, is related to the physical length of the tunnel and the speed with which the bottle moves through the tunnel. Increasing the residence time can increase the degree of shrink (similarly to increasing temperature). However, increasing residence time and increasing temperature will not always yield the same result and should not be considered perfect substitutes for one-another.

Balancing Temperature and Time

Achieving consistently good quality shrink results is a balancing act between temperature and time. We recommend changing only one variable at a time while testing to dial in the best parameters for your application. Generally, higher temperatures can allow for increased line speeds – although there are limits. Higher temperatures can also enable shorter heat tunnels.

This is a simplistic review of heat shrinking and there are many more variables that come into play when designing a quality heat shrink system.

Building a Heat Tunnel?

Before you start calling heat tunnel suppliers there are a few things you should know about your process:

What is your current line speed?
Do you have plans for line speeds to increase in the future?
What is the shrink label material? It is likely PVC or PET.
Do you have a specification sheet available for your label?
Will the system need the flexibility to do more than one bottle and/or label type?
What is the shape and size of your container(s)? What is the spacing between containers?
Are there are space constraints on the production floor or on the conveyor belt?

These are all questions a reputable equipment supplier should be asking when you approach them. Having the answers at your fingertips will make your interactions with them more efficient.

Let us do the work: We can engineer, test, and build you a custom heat tunnel to help you achieve that perfect shrink.