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FLEXO Magazine : June 2014
wise: Before you proceed, be sure to match the ink’s ability with your end print expectations. Accomplish this by obtaining printed examples from your ink supplier that demonstrate printing methods that are at least adaptable to your existing capability. PREPARING “POP” Sowhatdoweneedtodofirst?Setupa meeting with your ink supplier, anilox supplier and production staff to discuss goals and review how to pre qualify the variables prior to going to production. Request the technical data sheet and MSDS sheets for your specialty ink. These are very informative documents that you and your anilox supplier will need to make decisions. You can expect to find informa- tion regarding particle sizes, which can be particularly helpful when dealing with glitter, pearlescent and metallic inks. Often the particle size determines volume requirements because the particles have to be able to fit and sometimes flow within the cells. These sheets will also indicate an ink’s shelf life, which is often much shorter than standard ink systems. You may be surprised to find a batch life with an expiration date only a month from receiving. Many of these inks have longer lead times because they are not kept on the shelf, but are made to order when needed, due in large part to the short shelf life. Plan your tests accordingly. Don’t order the ink and then push off the testing for months. Make the commitment to test. Specialty inks may also be somewhat less stable thermally, so the inks must be kept within their temperature window. This means no freez- ing, no high humidity and storage in a stable window of operating temperature. Make sure you know what you can or cannot add to these inks for reduction and what to use for cleanup. Shocking a batch of ink can be very frustrating in the middle of a trial or during an anilox cleanup. You will also need to verify the type of substrate you are using to make sure the ink you want to use is compatible with the substrate. Learn what drying requirements are needed. If you are working with an older press running a water based application where you have only successfully dried ink films from 10 bcm volume aniloxes, and you are now going to put in a 30 bcm roll for glitter, you will find out that your drying capacity becomes a great hindrance to run speed and may not dry enough between stations. You are going to want to fully represent your printing process in the trial run. Testing should include the substrate you plan on running in production, the same inks and, where possible, the same setup. This will also give you some indica- tion of potential drying or curing issues you may need to consider when going to production. ANILOX SELECTION Once you have decided what your goal is and have the technical in- formation on your ink or coating, it is time to select your anilox. Keep in mind the particle size of your ink grind when dealing with glitter, pearlescent and metallic inks. A good rule of thumb when selecting an anilox is to maintain a minimum anilox opening to particle size ratio of 2:1. This method helps to select an anilox specification with a large opening and shallow depth. With this minimum ratio you will have a greater chance of enabling your ink particles to flow into and out of your anilox, transfer to your photopolymer and result in your desired specialty effect. Guidance from your anilox supplier will help determine which type of engraving will be the best fit. Thankfully, today there is a wide range of different anilox engravings to choose from: • 30 degree channel • 45 degree trihelical channel • 60 degree hexagonal • Elongated hex • 70 degree hexagonal • 90 degree XTR channel Regardless of the type of engraving chosen, keep in mind that with this kind of application, you will need to lay down a lot of ink to achieve the desired effect. For example, working with your anilox sup- plier, if the pigment grind of your ink is 35-40 microns, you will need to select engravings with minimum cell openings of 70-μm. to 80-μm. and 280 cells per inch (cpi) or lower. At 280 cpi, the cell opening is 85- μm. and engravings with lower specifications will have even larger cell openings. There are exceptions to every rule, so you must also inquire about the particle shape. Some particles require depth, as well as opening because the shape may be more round where most particles are a rod or flat flake and fit in the cells. Round particles need room to fit inside the cell. Using the engraving specification of 280 cpi with an opening of 80-μm., we can then review how much volume will be required. Consulting your ink supplier, if it happens that you’ll need 7.0 bcm 48 FLEXO | JUNE 2014