LABEL ISSUES

When problems occur with labeling, some of us have a tendency to blame the machine and start adjusting. True, there are often machine based issues. They get out of adjustment, wear or even break. But the materials can cause a lot of issues too. This month I want to talk about some common problems that can occur with pressure sensitive labelers.

Web breakage

In most cases, labels are supplied on a backing web of coated paper. This paper needs good tensile strength which allows it to be pulled through the labeler. Strong as it is, any damage such as a slight nick in the edge or an excessively deep die cut will rob it off of almost all its strength.

Nicks can occur during handling of the label roll or while in the labeling machine. As the label web passes over the various guides and nip rollers any misalignment of the rollers will move the web out of its desired path. Some operators and even mechanics will try to use guide collars on the rolls to force the web to the desired position. This seldom works as expected. It usually drags along the web edge causing nicks and weak spots.

Another cause of web breakage is improper die cutting. At the converter a knife must cut completely through the label without cutting into the web. If it cuts too deeply, into the web, it will cause a weak spot. The depth of cut may be checked with a felt tip marker. Place a section of web without labels on a sheet of white paper, rub the marker over the suspected areas, if it’s cut, the ink will bleed through to the paper below.

Adhesives

Label adhesives must be carefully matched to the product. There are several hundred types available and one size does not fit all. An adhesive that is fine for room temperature glass may not adhere at all to a plastic bottle at 40 degrees.

If a label/container combination has been working fine but begins to cause problems, check to see that the supplier has not changed adhesives.

Changes to the container can cause similar issues. In one instance a label had been running well for more than a year when it suddenly started wrinkling on application. After considerable head-scratching it turned out that the converter had changed from flame treatment of the bottles to plasma treatment. This prevented the adhesive from achieving proper initial tack.

Excessive adhesive and/or rolls that are too tightly wound can cause the adhesive to squeeze out from under the label. When this happens the label face can stick to the back of the web, the web itself can stick together, glue can accumulate in the labeler rollers or all of the above. If the labels have the right amount of adhesive but are too tightly wound, all of the above can occur plus there may not be enough adhesive left on the label to properly adhere to the container.

These are only a few of the label issues that can drive you nuts on the line. My main point today is don’t immediately assume the machine is at fault and start adjusting. Before touching anything, figure out what the problem really is.