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FLEXO Magazine : November 2010
Technologies & Techniques treatment could improve that by 2 to 4 dynes (39-42). The unit must be checked and maintained with a proper air gap of the electrodes. They are maintained at .60in. (1.5mm). Also a proper ground is needed for the system to work properly. Corona treatment could improve dot structure, ink laydown and dust problems in some cases. With proper testing, when a green bond (lamination) strength issue is found, it could be possible to fix, or at least eliminate a variable. UV Dryer. Monitoring, testing, and proper documentation is the key. Are there proper hours on the bulb? Are the bulb or reflectors damaged or dirty? Is the power source given to the lamp in specs? Monitoring and documenting the proper hours on the bulb is a must! Possible concerns include lamp faulting. If this occurs frequently, it could damage or reduce the bulb’s life. Another issue is inconsistent power source to the lamp. You could get more bulb life through proper preven- tive maintenance. Most UV blubs are guaranteed around 1,000 hours, but are some being used more than others with long runs, and are power levels always at 100 percent? This could be affecting the bulb life. If a lamination green bond strength issue occurs, the bulb should be checked first. There are UV test strips available that give you a cure rate, but you need to have first tested them when the UV blub and unit are in peak working condition, then compare initial readings with current results to effectively utilize them. Chiller. Is it functioning and is it being used properly? If they are setting it below or close to the dew point, water and condensation can buildup on the chill rollers and introduce moisture as a possible variable or contaminant. For unsup- ported films, +/- 2 degrees Fahrenheit is the standard. It is a press component that could induce issues if not run properly. Tooling Dies and Cylinders. How do you store them and prevent damage from occurring? What is the condition of your gears? Are they dirty and damaged? Do you have documen- tation on the amount of revolution—the die’s suggested life? Do you have pressure gauges regulating the amount of pres- sure you are adding? Do you document footage or revolution used after each job on the die box to get an estimated amount of revolution that the die has had since its last retool? What about the condition of the printing cylinders and their gears? Keep all documentation. Regularly inspect gears, dies, and cylinders. Having gauges to regulate the amount of pressure applied and working with your tooling vendors on proper stor- age, documentation, and inspection is the key. They will work with you on a program. Anilox and Doctor Blade. Is the anilox and doctor blade being properly maintained? Anilox rolls can carry inconsis- tent amounts of ink, due to damage. Some of the factors that contribute to cell and surface damage are poor housekeep- ing and the type of cleaning chemical/system used. The doctor blade should typically get a full shift’s worth of use, but there are too many things that can change that, so be sure, discuss this with your supplier. With doctor blades, the biggest issue is pressure. When you compensate for a bad blade, bad holder, or incorrect setup, it often causes excessive pressure. This can cause anilox dam- age (scoring) by forcing the blade tip to flex, possibly sliver or even break off. This also creates hydroplaning, which causes more ink to push under the blade (flood coating) creating inconsistent ink film thickness and drying issues. Other guidelines include: • Avoid letting water-based ink sit on the anilox to dry for more than 45 seconds; it will plug cells. • Revisit cleaning procedures on the aniloxes. • Have the anilox rolls periodically audited. • Once they have been audited, analyze the results and begin to send one anilox a month to be reconditioned. • The doctor blade type, its thickness and tip type are the makeup of how a blade performs. You should always be on the lookout for excessive blade wear, spitting, and hydroplaning. Anilox rolls and doctor blades are the backbone of the inking system. In my travels, I have seen rolls in the press not turning up to five minutes at a time, and rolls set on the cleanup rack and left with dried ink on them. Also, nearly every print shop has rolls that have deteriorated, are clogged and have damage to them and their cells. Your vendor can audit your anilox and, in the same visit, properly train your press operators on cleanup procedures and preventive main- tenance. They will also work within your budget to improve your anilox inventory. Inks and Drying. Are your inks drying or curing correctly? Is your ink consistent from batch to batch? Does it have the rheology (makeup and flow characterization) needed with your print and press configuration? If so, can it maintain its rheology with higher speeds and still cure or dry properly? Are your idlers properly cleaned and wrapped to give opti- mum dwell time for the ink to flash the amines, dry, and not pickoff? Most print shops house a wide variety of ink types, sometimes from different vendors. What is the date on these inks? Has any additive(s) been, well, added? What about contaminants that could effect drying and the overall makeup of the ink system? These questions are part of the variables of inks and drying that need to be addressed when pushing the press to its threshold. UV Adhesive. Is this the proper adhesive for your needs? Is any contaminant being introduced into the equation? Is it consistent from batch to batch? Proper testing procedures are what will make sure you are covered. UV adhesive are typically guaranteed for a year. Even though they seem to be doing a sufficient enough job, will they still perform when you push the speed of the press? Always make sure adhesives are clearly marked with an expiration date and remember that there is always the possibility of contaminates. Press Conditions. Is the press and its components cleaned and maintained on a daily basis? Do you have a preventive maintenance program set up to keep it in optimum printing condition? Are contaminants being introduced into the equa- tion because of the housekeeping or due to a lack of it? Work with and monitor operators on properly cleaning and maintaining the press on a daily, weekly and monthly basis. Here are some things to think of and ask yourself about your printing department. • Is the production area properly maintained and cleaned, including the press and its components? • Have you setup periodic preventive maintenance proce- dures as per your press manufacture’s guide? • How about utilizing input from the plant on preventive maintenance with operators’ suggestions. Look over how you now address preventive maintenance, then write down and highlight any daily and weekly issues that occur in your plant. Try to build a preventive maintenance How many revolutions can your die have before it needs replacing? 94 FLeXO november 2010 www.flexography.org FLX_Nov10_mech.indd 94 11/1/10 2:27 PM
Sustainable Fall 2010