Adhesive challenges: Top 5 issues with plate mounting

If you’re a printer, you know that plate mounting causes all kinds of issues.

But which ones are the most pressing?

We knew you’d want to know, so we sat down with our R&D team to get the answers you need!

Here are the top five challenges for mounting plates with adhesives:

 

 

1. Plate lift

Plate lift is when either the lead or trail edge of the plate is lifting off the tape. Plate lifting causes other issues because the press may start printing where it shouldn't, and the plate may need to be remounted. At the very least, you’ll need to take enough downtime to re-stick the tape on that part of a plate.

You may wonder what causes this particular issue, and there are a lot of culprits!

The plates could be:
• Old or deformed so that they curl back towards the image side.
• Dirty so that they don’t stick well.
• Contaminated on the edges from leftover primer or solvents so that the edge of the plate lifts off the tape.

Aside from problems with the plates, if the dryer temperature is too high or blowing air the wrong angle onto the sleeve, that can cause the plate to lift as well.

So how do you prevent plate lifting?

• Keep your plates in as good a condition as possible for easier mounting and easier re-use over time.

• Make sure the back of a plate is clean, so nothing gets between the plate and the adhesive.

• Be sure the plate is sticking directly to the adhesive.

• Use enough pressure to apply the plates so there's no chance of them springing back up.

• Use less solvent while cleaning in the press to prevent solvent from getting underneath the plate and lifting it up.

• Try using an edge-sealing tape to keep solvent from getting in.

• Apply a primer to the plate edge.

• Be sure the dryer is sealed correctly, and nothing is missing in a unit that might cause the air to create problems.

If you’ve checked all that and you're still having issues, you’ll want to reevaluate the tape you're using. There are definitely adhesives out there that can be a better solution! (ahem)

2. Compound lift

Compound lift is similar to plate lift in that it also involves the edge of the plate lifting. But in compound lift, the tape is pulling away, too.

The tape is actually coming off the sleeve or the cylinder at the edge of the plate. This problem leads to similar effects as plate lifting, including plates printing in areas where they shouldn't.

And again, downtime is needed to either re-adhere the tape and the plate or potentially remove the entire plate and tape and then remount them.

Compound lift can happen in storage or on press, and it’s important to be aware of some of the things that cause it:

 

• Insufficient pressure on the tape during the application process on a sleeve or cylinder.

• Temperature or humidity that’s too high in storage.

• Storage time that’s too long.

• Adhesion to the part of the sleeve or cylinders that’s too low.

• High temperatures in the press.

• Plate edges that are directly on top of the tape’s edge, often caused when press operators trim the tape and plate together.

With so many things causing compound lift, what can you do to prevent it?

Here are some ideas:

• Remount the plate rather than trying to cut it out.

• Use stretch films or flexible films to wrap the sleeves in storage.

• Use a squeegee for the tape application process.

• Keep the job in a conditioned area to prevent performance loss.

• Prevent hot air from running through the sleeves.

• Never cut the plate on the sleeve either during mounting or in the press.

• Be sure tape edges overlap the plate edges during the application.

And then if that's all been done and you're still having issues, tesa has several adhesive packages that use our X adhesive, which is our more aggressive sleeve-side adhesive. This extra adhesion can be really helpful in preventing any compound lifting during mounting or during press time!

 

3. Hard demount of the plate

Hard demount occurs anytime it's particularly difficult to remove a plate from the tape or the tape from the sleeve or the cylinder.

The trouble with hard demounts is that they cause bigger problems!

If it's difficult to remove the plate…
• The tape might tear and make a bigger mess.
• Adhesive residue may stay stuck on the plate, which then needs to be cleaned off.

One of the worst things that can happen with a hard demount is a plate tearing altogether, meaning it will need to be remade before that job can be run again. This situation can be so hard on operators. It takes so much more time to remove the plates and clean the plates. And the reality is… operators cannot reuse damaged plates.

It’s obvious, isn’t it, that preventing hard demounts is really important to the production process? As if we needed to tell you that…! If you’ve had trouble with this particular issue, you already know preventing it is a top priority.

But how can you prevent it?

Again, let’s hear what our R&D folks have to say:

 

 

"The best way to try to prevent hard demounting from both sides is making sure the backs of the plates are clean. Any previous residues from inks or adhesion promotors have to be cleaned off. The sleeves or cylinders must be clean as well. In short, be sure there's no residue that can cause the tape to stick.”

 

 

We suggest many, many, many times to make sure to clean the backside of the plates with either a 100 percent IPA or using up to 20 percent Acetate in the IPA solution before mounting and if possible, even before the storage time.

You simply don't want to have any contamination stay on the backside of the plate for a prolonged time during storage. The longer it stays on the backside of the plate, which is a PET surface, the longer it will adhere and the better it'll stick to the plate. That means it’ll be much harder to clean up!

Aside from making sure the plates, sleeves and cylinders are clean, here are some other possible solutions:

• Remove the plate with a slight angle. Pulling the plates in with a straight edge is always basically putting more strain on the plate and can lift up the tape seam. A slight angle while removing the plate always helps to avoid any tape lifting on the seam.

• Use chalk or apply some permanent marker on the tape’s seam to avoid the seam coming off from the sleeve or the cylinder and making the removal process harder.

• Use the right adhesive! We have some plate-side adhesive options like FE, Secure and TP  that all provide really easy plate removal in clean environments. They’ve all been designed to release plates easily. And then the Flex design can help with the removal of tape from the sleeve. The Flex design is less likely to split and comes off as a whole piece much easier than the classic design, so it won't leave residues or pieces of tape on the sleeve or cylinder.

 

4. Air bubbles between the tape and cylinder or sleeve

Air bubbles between the tape and cylinder or sleeve sound pretty self-explanatory, don’t they?

Let’s take a closer look anyway!

Bubbles are actually air pockets, and sometimes they form between the tape and the sleeve or a cylinder. This can happen during mounting, in storage, or while on press.

Bubbles sound innocent enough, but they actually cause a boatload of trouble. Here’s how they form.

How air bubbles form:

• The cleaning agents we use on a sleeve can cause air bubbles when they get trapped under the tape in deep scratches or gouges that are on the surface of the sleeve or the cylinder.

• A large temperature difference between the tape and the sleeve during application can trap humidity that creates air bubbles.

• Air pressure that forces thin-walled sleeves to expand and contract can stretch and deform tape, which also causes air bubbles.

• When the adhesion to the plate is higher than the adhesion to the sleeve or cylinder, the tape sticks to the plate more and creates the potential for air bubbles. The plate is always pulling on the tape, as if it wants to pull it away from the sleeve or cylinder, and that’s the real culprit!

How to keep air bubbles from forming:
It's really important to let that surface dry properly before mounting the tape so that the cleaning agents don't evaporate and create bubbles. It’s also important to keep the tape and cylinder or sleeve at similar temperatures to keep humidity from getting trapped between them.

Tapes like our Flex tapes that stretch to compensate for sleeve movement are a solution to the bubbles that result from expansion and contraction. And tapes such as FE, Secure or TP that allow for easier plate repositioning is the answer to the plate pulling on the tape.

 

5. Bubbles between the tape and plates

Did you know bubbles can also form between the tape and plate? This challenge is similar to the issues with other air bubbles except here the air is trapped between the tape and the plate.

If this happens during mounting, it's usually fixed simply by pulling the plate up and remounting it.

If it happens during storage or on press when smaller air pockets are forced together and form a larger bubble, it may actually be difficult to see, making it harder to address.

Just like with other issues, bubbles between the tape and plates can cause big problems, one being the plates printing in areas that aren't intended to print. This is especially troublesome when sufficient pressure isn’t being applied to a plate as it's mounted.

Wondering what to do to fix these bubble troubles? Here are some ideas to get you started:

• Make sure you're using a good hard roller to roll down the plate.

• Use the roller on your mounting machine.

• Roll slowly because rolling too fast can cause insufficient pressurization and create air bubbles.

• Check the backside of the plate to be sure it’s not dirty or contaminated.

• Clean off any soap, oil, grease, or polymer residues.

• In areas where the plate wants to pop up from the tape, be sure to keep it as flat as possible or add a little bit of adhesion promoter just in that one spot to help the plate stay down.

And one final option… Check out tesa® plate-mounting solutions on our link below!

Our FE adhesive, which we know has great hold for up to 72 hours, may be helpful. Especially if you're storing plates for a long time, this adhesive can ensure the plate is secure for up to three days.

In a less clean environment where you know that there are some residues or maybe the cleaning isn’t as great, we’ve found really good success with our SteelMaster tapes or our STM tapes.

If it's more of an SOP issue, bring in your tesa Sales Specialist or your Application Solution expert to really help uncover what the issues are and eliminate them before swapping tape!