Managing Ink Systems for Flexo Perfection

One of the things we know, as ink systems experts, is that a well-managed system helps ensure every job runs smoothly. The issues we’ve seen are all related, although some may focus on one component more than another.

Still, one or more of four basic points always seems to come up, no matter where we go.

Size Matters

It turns out that size matters—blade size, that is. In fact, when a customer asks us to evaluate their inking systems, one of the first things we check is the type and size of the doctor, metering and containment blades they are using.

We have found inaccurately or inconsistently cut blades to be leading causes of chamber leaks and excess consumption of blade material. It is easy to overlook a blade that’s a fraction of an inch too short, but the wasted ink can add up quickly over a long pressrun, increasing the cost for a job. This seemingly minor issue is one that must be addressed to optimize performance and help keep costs under control.

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Keeping chamber pressure as low as possible can avoid ink control problems with both doctor blades and end seals.
All photos courtesy of Provident LLC

On a visit to one mid and wide web packaging printer, for instance, blades cut just a little short were causing leaks on three different presses, dripping money every time they ran. We recommended purchasing blades pre-cut to the specific lengths required. Our technical sales rep measured the correct sizes and shop management agreed to blade lengths of 49.6755-in., 45.725-in. and 65.475-in. We shipped two samples of each size to verify proper length before ordering pre-cut blades.

Note here that the measurements were to the thousandth and even ten-thousandth of an inch, further proof that size can really matter. Remember, your ink chambers are pressurized, so even a small leak on a 6-, 8- or 10-color central impression (CI) press can have a big impact on the amount of ink used, especially on a run of, say, 180,000 6-color, 35-lb. dog food bags.

It’s also important to remember that all blades on a press are equally valuable, so your containment and metering blades must be precisely measured and correctly installed.

Begin with exact measurements, such as those supplied by the press manufacturer. However, there are four or more anilox rolls on a CI press and we know firsthand that blade lengths are not always interchangeable across those rolls. So be precise when you place your order.

Accuracy is especially important when taking your own measurements. You need to either buy a tool for precise measurement—and use it correctly—or have your press or doctor blade supplier make the measurements for you.

Right Blade, Right Job

Still, even if you measured twice and verified the exact size blade you need, the effort can be wasted if you aren’t specifying the right type of blade. Like so many other things about these seemingly innocuous strips of steel, plastic or polyester laminate, there is more to doctor blades than first appears. So, you absolutely must order the right blade for every job.

“One of the greatest differences between shops that are growing and consistently profitable is paying attention to these basic best practices.”

For example, I think of a customer who was running a lot of titanium inks but not buying coated blades for use on his white decks. Coated blades are resistant to titanium inks, providing a longer service life. The seemingly less-costly option of normal blades wound up costing money because titanium inks—as you well know—tend to chew up normal, uncoated steel blades very quickly. When you do the numbers and compare the cumulative costs of continually replacing normal blades versus the longer life of coated ones, it is clear you can be spending money you could instead be saving. And it’s not just the cost of the blades: changing blades takes your press offline when it could be productive, adding to the real cost of the cheaper choice.

One seemingly minor factor is the blade evaluation forms provided by many blade suppliers. These provide information that can highlight subtle differences in blades, so when there’s an option, use the more detailed version of the forms available. Your blade supplier may also be able to use the info when evaluating other products in your facility. For instance, the forms may document blade choices that could be influencing anilox roll wear or poor metering.

On a related note, be sure you measure blade wear and life consistently across all your presses. They won’t all be the same, of course, but using a consistent measure, such as counters, on all presses can lead you to a decision point based on a metric you can refer back to, or revise, over time. Moreover, don’t fall into the trap of assuming that all blades should routinely be changed after a specific amount of substrate run. This results in changing some blades too early, and others when they are past their practical life. Both cost money.

Many successful shops base blade changes on experience, such as counts when using a specified substrate or type of ink (such as white). Some go so far as to run certain types of jobs only on specific presses because it takes one more variable out of the process. This is a “work smarter, not harder” kind of thing that makes a lot of sense.

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Changing end seals regularly—weekly is suggested—minimizes unplanned downtime.

To get started, pick a couple of presses for testing and monitor the results over, say, a three- or six-month period. Mount the counters and new doctor, metering and containment blades. Then document every job run: run lengths, types of inks and substrates used, and carefully track any other variables. Over the course of the test, you will be able to identify and begin reducing inconsistencies, so you can run your shop more efficiently and better control and predict your costs.

Blades, Chambers & More

It’s interesting to note the things you see when visiting printers across North America. We recently saw firsthand the importance of blade size, but it was width, not length. A mid web machine was having an ink contamination problem on just one deck. We traced it to a plastic containment blade that was much wider than needed, which resulted in some of the plastic actually melting, fouling the ink in that chamber, causing flow issues and degraded print quality.

The wider blade had probably been put on because it was the only one available and the job had to be run, but using it caused a problem requiring immediate attention and slowing production. It amply demonstrated why every blade must be correct for the press, the deck and the application.

Other issues we encounter are also in mid and wide web presses with pressurized ink chambers. For instance, it’s not unusual for operators to run excessive chamber pressures. This almost inevitably leads to ink control problems with blades and end seals, so we recommend keeping chamber pressures as low as possible. This is definitely a place where the “some is good, more is better” approach does not apply! Talk with your press manufacturer or doctor blade and end seal supplier to determine the optimal chamber pressures to use.

“It’s also important to remember that all blades on a press are equally valuable, so your containment and metering blades must be precisely measured and correctly installed.”

Other details that matter keep showing up. Even when using the correct pressures on every deck, we’ve found that using chamber-wrap blades can save time and money. These blades have a plastic film that wraps around the blade holder and is fastened in place with double-sided tape. This helps direct ink that would otherwise go to the doctor blade chamber onto the plastic film. The real money-saving part comes at removal time. All the chamber hardware (pins, bars, bolts and clamping assembly) stays clean, reducing cleanup time.

And don’t ignore end seals, perhaps the most innocuous of consumables. End seals come in a variety of styles and are made of different materials that can mean the difference between daily or weekly changes, and whether they leak a little, too much or not at all. Talk with your favorite ink system specialist to make sure your seals will do what you need. We recommend changing seals at weekly press maintenance periods to minimize unplanned downtime—like when a seal blows out in the middle of long run.

Keep Rolls Clean

The last point is one you’d think would be obvious, but we find it is anything but. Keep those expensive anilox rolls as pristine as possible! We see rolls that are rarely cleaned thoroughly, resulting in a range of imaging and ink system problems. We recommend dedicating a tank to only anilox cleaning, and religiously maintaining a clean solution.

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The chambered wrap blade features plastic film wrap applied to the blade holder, fastened in place with double sided tape. It directs ink onto the plastic film.

Clean rolls after every shift or after long-run jobs—and this doesn’t mean a casual wipe with a dirty rag. Improper or inadequate cleaning leads to downtime, degraded print quality and wasted product. Run the numbers in your plant to see the impact improperly cleaned rolls may be having, and institute some rules and procedures to address the issue. Too often we see printers sending rolls out for deep cleaning, to re-engrave older ones, and be poised to buy new rolls when all that’s really required is implementation of comprehensive cleaning practices.

One of the greatest differences between shops that are growing and consistently profitable is paying attention to these basic best practices. It takes some diligence to make these habits, but the results are ones you can take to the bank.

About the Author

headshot Andy Gillis
Andy Gillis is general manager of Provident LLC, a wholly owned subsidiary of Anderson & Vreeland Inc. He is responsible for sales, manufacturing, customer service, purchasing, warehousing, technical service and support. A 20-year veteran of the flexographic printing industry, his past experience includes service as managing director, print division, Green Bay Converting. His early career was spent in sales roles at Paper Converting Machine Co.