by SknyRussianHillbilly » Thu Aug 08, 2013 3:55 pm
At one time rule the of thumb was 3 lpi (or cells per inch) engraving for every 1 lpi of halftone screen frequency.
At that time a 120 line process halftone would typically run on a 360 or 400 line anilox because that was high end on the engraving.
As the sciences of engraved rollers improved it moved to 4:1, then 5:1, and some even use 6:1.
The bottom line is that finer engravings seem to run cleaner, be less likely to produce plate plugging, and a type of dot gain.
There is a lot of sales hype on newer and different engravings, if you stick with the tried and true 60 degree engraving angle you should not be disappointed.
As far as cell volume or BCM goes they should be the same for all colors. Adjustments for strength values can ge made on the ink side. And the inks do need to be maintained for consistency.
The science of process printing is pretty good in flexo nowadays, but you need to do be able to do some measuring and testing ahead of time to make good use of those applications. They will likely involve your plate, anilox, and ink people to one degree or another. Name of the game is consistent repeatability.
I may guess that you could be "winging" a process job here and there. Skilled craftsmen with a 'bag of tricks' did it well for years. The best of them we may be thankful to for developing the sciences that can be found documented in nice publications like the aforementioned FIRST 4.0.
Good luck to you my friend.