Re: implementing G7
Greetings,
Favorite flexographer, interesting title. Michael is correct in stating that there are many variables that need to be considered when doing press tests of any nature, especially using the G7 methodology. A gentleman I know that does press optimization for a major flexographic plate manufacturer once told me that he stop counting when he got to 70 different variables.
That said, my advice is that you invite to the press runs all vendors that cover the print process, including prepress, that you are not knowledgeable about. You will also need to contact your ink company and discuss their familiarity with G7. I have worked with 4 popular flexo ink companies and none were aware of G7 until I mentioned it.
I think the G7 methodology has been very helpful and I would recommend the purchase of IDEALink to help determine the curves. I have also found that averaging press runs is a must to smooth out the curves that I see from my press runs. This averaging can be done by measuring multiple sheets or by the use of averaging software. If you decide to do it by measuring make sure you have a target and a measuring device that will not force you to measure in spot mode. Life is just too short for that. The number of sheets to average is open to debate and I feel can only be discovered after a few press runs.
One of my most challenging tasks, much to my surprise, has been to get presses to run evenly across the web in reference to density (Lab values) and TVI. Press operators seem not to be instructed as a QC check to be concerned about evenness across the web, even though we in prepress have been placing QC graphic elements on both sides of the web for many, many years.
Be sure to take very thorough notes as the G7 methodology takes a few press runs to get final results and you want to make sure all press components, the ones that Michael noted, are the same from run to run. Good luck, it can be done!!
-Bill-