The Anilox Roll Audit - A Smart Buying Decision By: Jill Salzman, Technical Analyst, Harper Corp. of America Maintaining a good budget is important to the success of any business. For a flexographic printing company, producing a high quality product that sustains business with their customers is the bottom line. Flexographic printing is scientific. If a press job is set up correctly, all components that come together are supported by numbers: required volume and line screen of the anilox roll, viscosity of ink, precision of plate image, components within thousandths of an inch. Once this is all in place, the system relies heavily on the skill and accuracy of the press operator to bring it all together and produce a product that meets a customer’s quality expectations. Doing this on a daily basis lies within their control... to a certain point. Many components go into setting up a press job, and when something goes wrong, there are a series of troubleshooting tasks to make it right again. This takes place under a significant amount of pressure; there’s the cost of expensed time, cost of waste, the list goes on. An operator can check the ink train, plates, doctor blades, etc, and finally the anilox roll. If the anilox roll is in defective condition, the only option remaining is to physically remove the roll and hope there is another roll in inventory with the same line screen and volume in good condition. By knowing the condition of the anilox roll at the start, this can be avoided. So, let’s get back to basics. An anilox roll audit. Anilox rolls are not cheap and a well-managed anilox inventory can help your bottom line profitability. Your anilox supplier can provide you with this tool to help you maintain a useful anilox inventory, help better your process, and make proof positive buying decisions. Besides determining the condition of your anilox inventory, this valuable resource can aid in:
The main purpose of an anilox roll audit is to determine the condition of your anilox inventory, to provide you with facts and logic. There are many technologies available in the industry to determine the integrity of an anilox roll and reasons for ill performance. First, there is interferomic measurement. This form of volume measurement scans the surface of a roll engraving and produces a volume reading +/- as fine as 10 nanometers; the most accurate known in industry. It is able to produce the line screen, depth and volume of a roll. It’s a live scan of the roll surface, where most cases you can physically see the anilox roll condition. The unit is very delicate and expensive to use. The real proof of your anilox condition lies in an actual picture of the roll surface. At Harper Corporation, we use what is called an Echochek™, or small piece of foil known as indium. Indium is a soft, pliant, flexible, silver-white metallic element. Its properties can be used to form a mirror surface that is corrosion-resistant, and does not oxidize at room temperature. Figure 1 The Echochek™ (see Figure 1, above) is pressed on the surface of an anilox roll. The impression of the engraving can be examined and photographed under a microscope. Using Echochek foils, Harper derives useful anilox engraving information and factors of the anilox condition that may directly relate to the quality of your print. Because of the flexibility of the echochek foil, it can capture exact mirror imprints, with limitless ability to capture precise impressions, regardless of line screen or cell characteristic of the anilox roll. Echocheks show all and tell all about the integrity of your roll. These photos can be very revealing, and of great benefit in reassuring printers, their rolls are in proper condition for optimum printing. Once each roll is evaluated, interferomic measurement information and echocheks work hand in hand. A qualified technician can interpret the data to produce a report. Information generated includes (see Figure 2, below): Figure 2
Quality of the Anilox Engraving Condition of the Anilox Roll Line Screen Cell Wall Size Cell Shape Consistency of Engraving The picture is the most important part of the report and can show the quality of engravings not viewable by the human eye. The primary objective is to view cell engravings under a microscope; a technician measures the cell opening size, the cell depth and calculates the volume. The formula used to determine volume is accurate for a very small range of cell shapes; therefore, the accuracy of "calculated volumes" is approximate at best. There are limitations in calculating the volume of line screens below 100. Because the volumes of these rolls are so high, the thickness of the foil simply does not reach the bottom of the cells and the volume should be determined with another form of measurement. What is the depth window? Can we purchase a thicker echochek? The sole purpose of your anilox-inspecting technician’s job should be to work from an objective standpoint. A truthful analysis should include an image generated from the anilox roll surface with scientific data to support any recommendations and comments. To build a brand of quality your customers can rely on; every roll in your inventory should be maximized to work in conjunction with one another. Whether you have an inventory of 10 or 200 rolls, each should be analyzed individually to ensure the consistent delivery of quality results when on press. A roll audit does not necessarily mean costly replacement of the roll. The need to replace your roll depends upon its function. For example, if you are an envelope or newspaper printer, it may not be critical to recondition your roll inventory although the anilox roll is showing wear worn. You may be able to continue to maintain color strength for line work. On the other hand, for a tag and label printer, 7-color process, it’s critical to maintain color strength with the volume of the anilox originally ordered. Wasted time and material are too costly to continue printing with a worn anilox. Scoring is another form of damage, and can be detected with the human eye and the severity can be measured. Though the score line may not be in an area on the anilox roll that affects your print results at all, the cell integrity may be weakened, providing the opportunity for further more serious damage to occur to the anilox roll. A roll audit can help you determine the need for roll replacement (see Figure 3, below). Figure 3
The audit should ultimately provide you with the ability to take a serious look at what is needed to print the product you produce and provide a benchmark for future reference. Most anilox manufacturers provide a quality certification of the roll that includes a picture. This can be key to managing your valuable inventory. When your roll is evaluated, you will have a reference point to make a visual comparison. It’s also important to work with an anilox manufacturer who provides you with a product that is consistent and repeatable. The quality of the rolls you order lies solely in the quality standards of your anilox manufacturer. If the roll is poorly engraved from the beginning, possible print problems will never go away. When an audit is complete, the technical support of your anilox supplier shouldn’t stop at images in a booklet. A roll audit can also provide an opportunity to implement corrective action to help reduce and eliminate future damage (installing filter magnets, doctor blade quality, assessing doctor blade pressure, etc.). An acceptable assessment of your anilox inventory should leave no questions unanswered. If you are uncertain or have any inquiry regarding the results of your roll audit, question your anilox supplier until you are clear. The anilox roll audit contributes to making logical buying decisions and managing a smart business.
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