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FLEXO Magazine : August 2010
Technologies & Techniques Anilox CleAning It cannot be emphasized enough how vital good house- keeping is to helping maintain the quality of print and overall profitability. It never ceases to amaze me when so much effort is put into the selection of the anilox, how little, if any, effort is made to keep the anilox clean in any serious way. Rinsing off with a solvent-soaked rag, hose pipe and plain water or even scrubbing manually with a brush from time to time will not do the job that is needed. Yet, this is the case in many print departments where the mantra is “must keep the press running at all times. ” If there was ever a misconception, then the idea that it is possible to run a press 100 percent of the time must be top of the list. In reality, many presses run less than 50 percent of the time. If you don’t believe me, check out your own equipment; you may be in for a shock! The reality is presses are being stopped or slowed down continually in an effort to adjust inks, clean plates, adjust plates, clean anilox and so on. It is, however, the cleaning of the anilox, or lack there of, that is often the root cause of poor color strength, inconsistent lay down, and dirty print that the operators have to contend with on a daily basis. Manual cleaning is the most used process and, if done reg- ularly and conscientiously, this can be remarkably successful. That said, how much time do you allocate for your operator to do this? What tools and cleaning solutions are provided for the operator to use? All too often, operators either do not have enough clean- ing solutions, cleaning cloths, brushes, the correct type of cleaning solution or even adequate time to clean the anilox. As to what should be used for chrome rolls, you cannot use anything other than a brass or nylon brush. For ceramic, you must only use a stainless brush. Brass is too soft on ceramic and will just plug the cells even more. Nylon has a nasty habit of its bristles breaking off and getting into the ink system. As for the correct cleaning solution, if you have a solvent ink, then solvent should be used. Water-based inks generally can be cleaned well with a detergent. UV systems require a modified solution to suit the particular chemistry. Because manual cleaning, by its very nature, is labor inten- sive. Mechanical systems have been developed to aid in the process, which include: • Ultrasonics. • Baking soda. • Plastic media. • Dry Ice. • High pressure water (detergent). • High pressure solvent. • Laser. All of these systems can and do work well. Most compa- nies, however, tend to over use them, with the logic being that more must be better. Certainly regular cleaning is highly recommended, but it needs to be understood that mechanical cleaning systems are very powerful. Ceramic coatings are relatively brittle, so over exposure to them can lead to dam- age to the engraved cell and coating itself. With the exception of the ultrasonic cleaning, all the other systems depend on air pressure or water pressure, clean- ing particle size, rotational speed, traverse speed, nozzle distance from engraved surface. All of these, unfortunately, are often manually controlled and therefore subject to abuse, which can and often will result in damage to the engraved surface, if not maintained at the manufacturers’ recommend- ed settings. Now, to be fair, most equipment manufacturers have locked out and preset controls that limit what the opera- tor can adjust. Modern ultrasonics also have preset cleaning times, alternating generators and auto rotation and are non-labor intensive, which makes them very consistent regardless of the screen count and volume being cleaned. Other cleaning solu- tions that are used for manual cleaning can be overly acidic or caustic. While they do get the engraved surface clean, solution residue left behind can attack the underlying steel or aluminum and cause complete bond failure between the inner core and ceramic coating. The reality is that most printers, managers want to minimize the amount of down time in having to clean the anilox and expect the cleaning agent to be a silver bullet that will clean anything off any surface. True, there are some solutions that appear to achieve this goal, but I have to again say that they usually do it to the detriment of the ceramic coating and steel core. The truth is, if you clean your rolls regularly; then ag- gressive cleaning solutions or excessive mechanical cleaning is not necessary. It may sound much easier than having to choose the right combination of doctor blade, Photo courtesy Harper Corporation of America 98 FLeXO August 2010 www.flexography.org DoCtor BlADe Q&A (con’t.) MAny suppliers Are now ClAiMing CoAteD BlADes hAve greAter Benefits thAn trA- DitionAl BlADe MAteriAl. is this true, AnD if so, whAt Are those Benefits? Coated blades started to be introduced in the mid- 1990s and seem to have gained some popularity in the last few years. Most manufacturers claim that coated blades give a cleaner print, less friction, help to reduce burrs and—the big one—that they supposedly last several times longer than uncoated blades. While many manufacturers promote some softer coatings as provid- ing a softer contact with the anilox and can even heal smaller nicks in the blade, others advocate ceramic coated tips that do give extended blade life. Other coatings can help reduce corrosion and splitting of the blade so, all in all, coated blades do seem to be produc- ing benefits that the manufacturers are telling you. August2010_mech.indd 98 8/13/10 1:23 PM
Sustainable Summer 2010