Less is More
Choosing the adhesive characteristics of flexographic mounting tapes should not rely on a “some is good, more is better” strategy. Here’s why: two challenges plate mounters face almost every day are difficulty in removing plates and plates tearing during removal. A leading cause of this is strong, high-tack adhesives being used to attach the plate to the cylinder.
The strength of such adhesives can quickly translate to increased operating costs. First, a plate that is torn or damaged during removal can be a costly replacement, and second, plates that are difficult to remove can result in operators incurring injuries when peeling large plates off the cylinder.
The Pros of Low
Almost counterintuitively, low-tack adhesives can provide a superior solution that offers benefits on the pressroom floor and in operating costs. However, because not all low-tack options are alike, it’s important to revise some common thinking, as well as understand the advantages of low-tack adhesives, so you can make informed decisions about the best ones for your operation.
To start, it’s not a good practice to rely on the time-honored “thumb-tack” test; peeling back a bit of the liner to see how tacky the adhesive is on one’s thumb. The trouble with this is that tackiness and adhesion are different properties of tape. Rather than testing the tackiness on your thumb, pay attention to how well the adhesive bonds to plates. You’ll find low-tack tapes have better adhesion properties specifically designed for printing plates.
Next, think about your operation and how it may be changing. If you are seeing shorter runs and more frequent job changes, it likely means mounting and demounting of plates is a pain point in your operation. These pain points can be mitigated by using tapes that allow plates to be more easily removed from cylinders. Some printers and converters try to work around high-tack adhesives by using shellac, soap, baby powder or other additives to deaden the adhesion. These “Band-Aid” solutions can work, but still require additional time and labor. Not only are these processes not repeatable, they may lead to larger problems, such as bubbles and plate lift, resulting in more downtime when plates need to be removed and remounted.
And finally, because some high-tack adhesives have a tendency to lift at the edges, operators may use edge sealing tape or glue that further complicate the mounting process and increase plate changeover times.
Low-Tack Adhesives Can Mean High Profit
To wrap some numbers around all this, consider the time your operators spend changing plates when using a high-tack adhesive, whether or not you are using an additive to facilitate removal of the plate from the cylinder. Reducing that time by 25 percent to 50 percent using a low-tack adhesive provides an immediate savings in labor, a more-repeatable SOP and an increase in throughput. Whether the change is one plate or the entire job, the difference in cost goes directly to your bottom line. For many shops, the difference can mean running several additional jobs each week.
Costs add up in other ways, too. Plates are becoming more high-tech and expensive, increasing the need to reuse them whenever possible. Low-tack adhesives can prolong plate life by limiting the likelihood of damage and helping ensure they can be reused.
Another advantage of low-tack adhesives is the ability to easily reposition a plate on a cylinder. It’s a fact of life that plates aren’t always perfectly positioned the first time and may need to be repositioned to ensure accurate registration. Low-tack adhesives make it much easier to remove and reattach a plate, again saving time and labor cost.
Despite these advantages, low-tack adhesives are not the best choice for all operations. For shops that face challenging environments, such as cold, heat and humidity, or where cleanliness is difficult, the added grip of a high-tack adhesive is probably a better choice.
Adhesive Choices for All Pressrooms
Because there is no one-size-fits-all type of mounting tape, many tape manufacturers and suppliers offer both high- and low-tack adhesives that meet multiple pressroom requirements. And, while the adhesives are of critical importance, the foam and backing used are also key parts of the printing process.
Tapes that make use of closed-cell foam can deliver good compression and recovery, which can then lead to better print quality, especially during long runs. Printers using these options report the tape can last up to 50 percent longer than competing products before losing print quality. This poses an operational advantage in that when print quality begins to decline, press operators often increase the pressure on the impression cylinder, which can lead to increased dot gain and ultimately poorer print quality.
A quality tape’s foam backing should also be conformable, allowing the adhesive to bond better by accommodating surface irregularities on thin-walled or scratched sleeves. This means customers can get more uses out of their sleeves before replacement is required—yet another cost savings. By comparison, the polyester reinforcement used on some tapes can cause it to “tent up” over scratches or grooves because the irregularities reduce the contact area of the adhesive. This can result in improper ink transfer and other imperfections in print quality.
Making the Right Choice
By understanding the benefits low-tack adhesives can provide, a printer can determine which ones will work best for its particular needs, possibly resulting in decreases in operating costs. As mentioned, not all low-tack options are alike, so take your time and do your research in order to come to the best decision.Learn More About Tesa Tapes
This article originally appeared in the October 2017 issue of Flexo Magazine available here.