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FLEXO Magazine : June 2013
Plants & Processes Doctor Blade to Anilox Cell Count the ration & the relationship By Johnny stamey Look back as little as five years ago. One of the biggest drivers in the flexo market was pushing press speeds to over 2,000 fpm. For the most part, all of the press manu- facturers accommodated the printer. It seems as of late; it is not about the speed of the press, but the speed of the press crews and how fast they can change from job to job. The average print job running on press today is about one-third the length that it had been in the past. A printer cannot keep rolls of printed stock on the shelf as in previous years. Today ’s directive: “Print on demand” for the customers. Customers want more shelf appeal for their products. They are achieving this with brighter colors, sharp images and year-round promotional packaging. Good news—printers have done a nice job and adapted to this type of pressroom atmosphere of short runs. Bad news—they are short runs. Now, the dilemma for the printer is how to make a profit for the company. Is the answer to be found in actual printing or on job changes? Either way, printers must be very efficient in what they do. We are going to look at one aspect of how a printer can make it efficient for the pressroom. CHOOSE CORRECTLY With four basic tip configurations (see boxed sidebar) available, we can plan on using a few parameters to decide what doctor blade fits your printing type/style best. First make TIP CONFIGURATIONS If you have to change doctor blades on every makeready, you are wasting valuable press time and you may be in need of a doctor blade makeover. Let’s look at a few things doctor blade and anilox roll related to help speed up the process of job changes. First let’s review the four basic styles of doctor blades. • The base of any doctor blade is straight steel as seen in Figure 1. This simply means, as stated, “straight” with no machine tip on the blade. You can place either edge to the anilox roll and it will perform the same. • In Figure 2 is a radius tipped blade. As you can see, both edges have a rounded tip and also both can be placed against the anilox roller (only use one edge of blade, never flip the blade and use both tips, this is a safety hazard and also can cause anilox roll damage). • In Figure 3, we get into the detailed tip configurations with the bevel blade. The most common beveled angles would be 3, 5 , 10, 15 and 45 degree. There are exceptions for special printing and coating applications, where bevel angles go outside of these parameters. • Looking at Figure 4, we have the Lamella tip (often referred to as a stepped blade), this doctor blade was first manufactured and patented by Max Daetwyler Corp. in the early 1970s. Since then, it has become the largest selling and most standard doctor blade around the world. The Lamella tip blade comes in many different tip thicknesses. Every manufacturer has standard tip sizes that they use. Lamella tip thicknesses range from 50 microns up to 200 microns, the most common being 75, 95, and 125 microns. Figure 4: standard lamella tip Figure 1: straight steel Figure 2: Flexolife radius tip Figure 3: 15° Bevel 78 FLEXO June 2013 www.flexography.org