Imagine you are rolling out a sheet of cookie dough. Once you decide on a shape, you take a cookie cutter and press it into the dough. After removing the excess dough around the shape, you’re left with a finished design.
This is exactly what die strikes do to labels.
Die strikes are a crucial part of the pressure sensitive label manufacturing process. These cuts must be done precisely with the perfect amount of pressure for labels to peel off the liner in a consistent and accurate release during application.
When labels release easily, production is able to run promptly and efficiently. When labels release poorly, production becomes disrupted due to equipment jamming or labels failing to apply.
If this release is difficult, one culprit to consider is die strikes.
The Converting Process
Like the cookie cutter analogy above, different shapes and sizes of labels are cut out of a large, continuous sheet of label material called laminate.
To produce a roll of labels from the laminate, it must go through a process called converting.
Converting happens when a large roll of paper or film laminate is fed through a machine press that cuts individual labels from the material on the lining with a tool called a die.
Dies are specially made pieces of metal tooling used to cut out shapes of the laminate. As the laminate makes its way through the press, pressure is applied to the die so it cuts into the material.
This cutting process is called the die strike.
At this stage, consistent pressure and alignment are key. Cuts must be precise so they go through the laminate but not the liner underneath.
Once the die strike occurs, the excess material surrounding the shape is removed, leaving behind the finished label. From here the large roll of material is fashioned down into smaller, individual rolls of labels for end users.
How Die Strike Issues Affect Label Release
One major reason labels fail to release easily from the liner is inaccurate die strikes.
When the label material passes through the die-cutting station, pressure is applied to the die with an anvil. The pressure and alignment of the die strike must be precise to maintain an even cut that goes through the material but not so much that it pierces the silicone on the liner underneath.
Unsuccessful die strikes result in labels not fully releasing from the liner, which affects the application process. These can be in the form of light or heavy die strikes.
Light Die Strikes
Die strikes that are too light do not fully cut into the label material.
When this happens, the web between each label fails to separate properly. As the webbing between labels is removed, the label goes with it, leaving a blank space on the liner.
These errors are thrown away and don’t make it to end users.
Heavy Die Strikes
Heavy die strikes occur when the die cuts too deep through the label material and into the silicone on the liner. This can be the result of incorrect operator settings or utilizing the wrong label die with the wrong label material.
When this happens, adhesive from the back of the label seeps through the cuts and into the liner through the silicone layer. This excess of adhesive sticks to the back of the label, preventing it from fully separating or being unable to peel.
One key way to tell if your labels have heavy die strikes is by using a marker on the outline of the liner.
Remove several labels and color heavily around the outline where the label was. If the marker is visible on the underside of the lining, heavy die strikes may have occurred.
Effects on Print & Apply Automation
In print and apply automation, labels need to peel away from the liner at an exact moment in order to be applied efficiently.
When labels have a difficult time releasing from the liner due to ineffective die strikes, they end up disrupting this process and halt operations, which can cost companies time and money.
So what exactly do die strike issues look like with print and apply automation? Some examples include:
- Labels completely staying on the lining
- Labels only partially separating from the lining
PET vs Die Strikes
PET (Polyethylene Terephthalate) is a type of film liner made from polyester.
While paper is more commonly used as a material for release liners, PET liners offer many benefits for users, especially when it comes to durability against heavy die strikes.
With paper, heavy die strikes are less forgiving. As previously mentioned, when this happens adhesive from the label spills into the liner through the silicone layer and under the base of the label, ultimately making for a more difficult release.
Added Benefits of PET
- 100% Fully Recyclable
- Drop In Replacement
- No Changes from Humidity
- Lighter Rolls
PET is more lenient when heavy die strikes occur.
Due to a combination of durable material, minimal silicone coating, and a thinner liner it still maintains a steady, successful release. This also means fewer jams in printers and applicators, which can be problematic for auto-apply applications and peel-and-present mode.
Understanding the importance of die strikes can help you recognize their purpose in print and apply automation as well as how to recognize issues when your labels fail to release easily from the liner.
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