I’ll begin with a story. The problem became evident because the anilox rolls were wearing quickly and affecting print quality. Press operators were searching the plant to find rolls that would deliver sufficient quality on jobs for key customers. Their searches were cutting into production time, throughput and impacting the quality of jobs being produced. Frustrated production staff felt they were not being given the right tools to do their job.
But the question remained: Why were the anilox rolls wearing so quickly?
Working upstream from the pressroom, it turned out that a purchasing agent had negotiated attractive pricing on low-cost doctor blades. He didn’t know inexpensive blades could cause excessive wear on anilox rolls, necessitating recovery or even replacement of those costly items.
In this case, lack of communication between the purchasing agent and the production team meant the agent lacked vital information about the flexographic printing process. But in a broader sense, the purchasing agent was not unlike his counterparts in many label and packaging businesses who think of doctor blades and end seals as consumable commodities to be acquired for the lowest possible price. To be fair, this can work some of the time, but because these consumables can have an impact on a converter’s operations—all the way to its bottom line—it is important to think of doctor blades and end seals in terms of ROI.
In another instance, a converter was sending out anilox rolls for recovering, because its doctor blades were too hard and were damaging the rolls. The financial hit was adding up to more than $15,000 a month, not counting the opportunity cost of work that was turned away or couldn’t be scheduled. As some veteran print executives might say, “Whenever you’re not printing, you’re not making money.” And in these instances, the losses were because someone decided an important part of the ink train was a commodity item.
[perfectpullquote align=”right” cite=”” link=”” color=”#00FFFF” class=”” size=””]In the best shops, consumables are replaced whether or not they are technically due for replacement, because it is less expensive to replace a consumable before it is worn out, than it is to stop the press during a job to replace the same part.[/perfectpullquote]
Doctor Blade Magic
Just as there is a difference between unbranded razor blades from the dollar store and those of the major brands, there is a difference in doctor blades. Most are made of a steel alloy with the best grades of steel having a high carbon content for wear reduction. Higher quality blades are also made to tight tolerances, and are straight so they wear evenly, run longer and minimize wear on anilox rolls. Beyond the physical characteristics, details matter when to comes to blade selection. For example, it’s important to match blades to the inks being used.
White inks, for instance, contain titanium dioxide, essentially a finely ground mineral about three times more abrasive than normal inks. This translates into greater wear on the doctor blade and the anilox roll used to put down that shot of white. So, unless the blade used is of sufficient hardness or has the correct ceramic coating, it will wear three times faster than normal. This means that on a job putting down white as the base layer for the other colors, using the wrong blade can result in up to three blade changes on the deck where that white ink is being used. It this case, it can make sense to use a more durable, higher-quality blade for the white ink deck and a lesser blade on the remaining decks, with the goal of running the entire job without stopping the press to change a blade.
I made white ink the culprit here, but it is hardly the only abrasive ink converters encounter. Metallic inks all put more wear on doctor blades and anilox rolls than do normal inks, and new haptic inks, which create a textured feel to a printed image, also put greater demands on doctor blades. And because these more abrasive inks are being used on more and more labels and packaging, it is important converters adapt to these changes by thinking more about their entire ink system, beginning with the humble doctor blade, and looking at consumables as productivity tools.
Optimizing Downtime—and Productivity
Three blade changes may not seem bad until you look at the economics. Let’s say your best press operator and helper can change a doctor blade on your central impression (CI) press in 20 minutes. If you are running a white or other abrasive ink with normal blades, you would have to change that blade for the most abrasive ink up to three times over the production run, which can add up to an hour when the press is not running.
Do the math: Begin with the per-hour cost for your press. If it’s a mid-sized CI press, that number is between $750 and $1,500 per hour. So, when the press is down for an hour (three stops at 20 minutes each) while operators swap in a new doctor blade, it is costing you press time, the cost of another blade, plus the substrate wasted while the press gets back up to speed and colors return to where they were. Then, several thousand feet of substrate later, you get to do it again. And maybe again. So, by the time the job is done, you’ve burned a couple grand in labor and press time while you saved a whopping $10-$15 on a doctor blade.
There is no economic argument that can make sense of this approach, especially when you look at the loss of productivity. Consider this or a similar scenario over the course of a week. How many other jobs—and how much revenue—might do more for your business than those hours of downtime?
[perfectpullquote align=”left” cite=”” link=”” color=”#00FFFF” class=”” size=””]In visiting countless converters, we’ve found the best companies have cultures that have a productivity and quality connection running from the president to the guys on the shop floor. Larger companies are sometimes better at this than smaller ones, but there are plenty of smaller firms where everyone pays attention to the ROI of everything they buy, including consumables like doctor blades and end seals. As a result, productivity is always high, joined at the hip with quality.[/perfectpullquote]
Blades are not the only consumable on the ink train. You probably don’t spend much time thinking about end seals—those little plugs of foam, rubber or felt in the ends of your ink trays—or at least you don’t think about them until one blows out and costs you half a shift or more of production. On a narrow web label press, a seal failure is mostly just messy, but when it happens on an upper ink tray on a big CI press, it shuts down the entire operation for a few hours while the press and floor are cleaned up. Then, the press is re-webbed, damaged materials are thrown away, and the job is restarted. It makes for a long day—and is a painful way to burn through a few hours of press time along with a few hundred feet of substrate and a few gallons of ink.
The best strategy is to include replacement of doctor blades and end seals in the time you typically schedule for normal planned or preventive maintenance. Most shops allow for a couple hours per week—Monday mornings are a common choice—for doing all normal preventive and scheduled maintenance on their presses. Because this is a set time each week, it does not interrupt production or result in any unplanned downtime. Many of the most successful and profitable converters replace doctor blades and end seals during these periods, using high-quality parts that can last a full week or more.
In the best shops, consumables are replaced whether or not they are technically due for replacement, because it is less expensive to replace a consumable before is worn out than it is to stop the press during a job to replace the same part. This approach optimizes downtime and helps reduce the chance of any surprises during the week. Some 24/7 shops with heavy volumes have two scheduled downtimes, such as on Monday and Friday mornings, when all maintenance is done, including swapping out consumables. No matter the schedule, the business owners, the supervisors and press operators all know the value of planned and preventive maintenance because it is part of the company’s DNA as a standard operating procedure (SOP). Productivity is the first big benefit and the extension of that is quality.
Productivity & Quality
In visiting countless converters, we’ve found the best companies have cultures that have a productivity and quality connection running from the president to the guys on the shop floor. Larger companies are sometimes better at this than smaller ones, but there are plenty of smaller firms where everyone pays attention to the ROI of everything they buy, including consumables like doctor blades and end seals. As a result, productivity is always high, joined at the hip with quality.
We’ve also noticed that converters with household-name customers selling upscale products are more likely to invest in better doctor blades because they realize the blades help ensure more consistent print quality throughout the length of a printrun than blades made of lower-quality steel. In contrast, customers producing high-volume generic items, such as plastic grocery bags, are content with lower-cost blades because print quality is typically not as important.
Press and operational knowledge, along with understanding the tools being used, are crucial to productivity and quality. To foster this, the best converters have made training part of their culture, ensuring that even the most experienced employees are always learning. This way, business 
owners, shop supervisors and press operators all understand their inking system and the relationships between inks, rollers, bearers, anilox rolls, plates, doctor blades and end seals, so they are better able to diagnose a problem—like anilox rolls that are wearing too fast or any lapses in productivity and print quality. Spread across a company, understanding the entire operation helps deliver the best results.
About the Author: Randy Carter is senior technical sales representative at Provident.
You must be logged in to post a comment.