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FLEXO Magazine : October 2010
Technologies & Techniques coated or uncoated, paper or film? You shouldn’t have to test every substrate. You may run a variety of substrates that have similar color, absorption, etc. Trial and resulTs Now that our components are selected, you need to con- duct the following during the run trial: • Visually check color and dot structure. • Measure solid ink density and color along with dot area side to side (control bands) to verify even impression. • Collect samples and document, document, document. Once trial is completed, have a group review data and make recommendations. If you were targeting one specific cpi/bcm combination, this would be set by your weakest link. For example, if all colors except reflex hit the desired strength at 3.5bcm, but reflex needed 4.5bcm you have a couple of options. • Option 1: Go with 4.5 bcm as your workhorse for spot / combo. • Option 2: See what can be done from an ink standpoint to increase strength of reflex. • Option 3: When formulating or running colors containing reflex use 4.5bcm and run 3.5bcm for everything else. Even when ink systems are not calibrated for a single volume, you can benefit from the exercise of testing your base inks to understand their required volumes and make for much shorter matching times. In most cases getting a calibrated set of base inks is not difficult and allows your inventory to be as standardized as possible. CommuniCaTion and doCumenTaTion Documentation is key throughout the entire trial pro- cess. Be sure to document not only the components used, but also the measurable aspects of each as well. This will ensure they have met the recommend- ed or predetermined targets. This includes plate relief (pos- sibly screen value of running targets), ink viscosity, pH of water-based inks, etc. If results show that, with the cpi/bcm combo chosen, the min dot achievable is 4 percent at 150lpi, then graphics should not come to press set up to run a vignette from 100 percent to a min of 1 percent. Simple, right? If you measure and document it, then you can repeat it. So, develop an SOP (standard operating procedure) for plate generation, ink preparation and anilox selection. CorrelaTion ink room To Press Unlike plate generation and anilox selection, which should be truly defined by this point in the process, ink preparation still allows for variability if left unchecked/unmeasured. These following suggestions deal with this particular issue. For starters, now that you have determined the specs for your workhorse anilox roll, it’s time to choose a method of proofing inks prior to them going to press. Multiple meth- ods are available. The two methods I am a big fan of are hand proofers and table proofers, as long as the units use a ceramic anilox, doctor blade and rubber metering roll. The main advantage of these proofing devices is they eliminate pressure as a variable. By doing so, it makes it easier to re- peat color matching shift to shift/operator to operator. Figure 5. Documentation of results. A table proofer. 54 FLeXO october 2010 www.flexography.org FLX_Oct10_mech.indd 54 10/15/10 9:28 AM
Sustainable Fall 2010