There are three different kinds of inks used in flexographic printing: solvent-based water-based and UV-curing Inks. This article is about adding water based inks to a flexographic press.
Gather all of the different colors of inks that you plan to use on the production run. For four color process,
this will be yellow, magenta, cyan, and black. Arrange the inks from light to dark.
Start with yellow at the first station of the press. For the second station, add magenta, then, cyan on the third station, and finally, black on the last.
Pour in the ink. If you have a short run, it may be better to “pan” the inks. This means that the ink will be poured directly into the pan on the ink station, and the rubber hose that is used for draining, will be tied off, so that no ink will drain out. If using this method, you should keep a close watch on the ink station while the press is running to ensure that the ink remains at the correct level, so that the proper amount of ink is transferred to the anilox roller. You may have to add more, as needed, during the run.
If you have a long run, you will usually pump the inks. On each ink pump, place a liner in the pail that you are going to add ink to. Place the pump cover on the pail, and then pour the amount of ink that you plan to use through one of the holes on the cover. Place the hose that drains the ink from the ink station tray, into one of the drainage holes on the pail cover, so that it can drain back into the pail. Place the hose coming from the pump into the pan on the ink station. Don’t forget to double check that each hose is secure and will not slip during a run.
Turn on the pump so that ink begins to flow into the pan. If you need a higher level of ink, place a thick washer over the drain so that it acts a dam, and raises the level of ink. As the level of ink begins to rise, adjust the flow from the pump. If it is too slow, it could stop pumping, as the ink will thicken due to evaporation. If the flow is too fast, it can overflow the tray and drip ink on the web, ruining the printed material, and creating a big mess.
You should keep a check on all of the ink stations throughout a production run. Make sure that the pumps are working correctly, the ink flow is steady, and the ink levels are where they should be. When using a water based ink, you may need to add an ounce or two of water, so that the correct consistency and drying time are maintained. If the ink is drying to fast, you may need to add PH Adjuster.
No matter how careful you are while handling inks, a spill is bound to happen. While this can be messy and troublesome, it happens to press operators with years of experience. Fortunately, water based inks can be cleaned up with a damp rag and a little elbow grease.
