Flat-Top Dots
Let’s start by stating what is meant by the term flat-top dot. A flat-top dot on a photopolymer plate is one that accepts the transfer of data from an imaging device to the finished plate at a 1:1 ratio. The 1:1 imaging ratio is measured in the file, post-CDI imaging, and ultimately on the final plate.
Now, let's dive into the details of what we have identified as the most frequent questions people ask about flat-top dots. We will release one question and answer over this 10-week timeframe.
Week #7. Aside from great ink laydown and solid ink density (SID) are there any other significant improvements to print quality that flat-top has to offer?
Most understand that flat-top technology is a forgiving plate that offers great ink laydown and SID. But for those who have already dialed in their process and inks are laying down without graininess (a.k.a pinholing) and mottle (a.k.a. orange peel) is the difference that great within overall print quality – assuming you're plates are also running clean?- Short answer, it is a differentiator. Benefits of flat-top dot print quality do reach beyond just SID and clean running screens/plates. But before going into additional benefits, lets first ask ourselves how we have come to the conclusion that what we already have is good enough. After all, ink transfer is one of the most overlooked areas of analysis.
- Graininess is another word for pinholing. The amount of pinholing is measured in terms of percentage of reflectance. When identifying this print characteristic, if a sample has 5% reflectance when measured then 95% of the area is covered with ink and 5% is left void or with pinholes. If put on a simple PASS or FAIL methodology 2% or less would be a pass or an indicator of exceptional level of coverage. Above 2% graininess/pinholing can be detected by the naked eye upon close examination. Note: this is only a measurement of coverage, not of the uniformity of the ink film thickness delivered to the substrate. Are you actively measuring graininess or is the assumption that if SID is achieved then pinholing is good enough?
- Smoothness is often a word to describe the uniformity of the ink laydown. The opposite of smooth would be mottle, or an orange peel effect. The amount of mottle is also measured in terms of percentage of reflectance. When identifying this print characteristic, if a sample has 5% reflectance when measuring for mottle then 95% of the sample appears to be smooth whereas 5% of the area experiences darker or lighter areas than the uniform area. Because mottle doesn’t necessarily mean you have a void in the ink (just a variation in thickness) it is more difficult to pick up with the naked eye. That being said, because you have dark/light areas of variations our eye perceives the combined optical difference of 5% being more like a 10% total variation. Therefore, we stick to the PASS - FAIL methodology of 2% or less would be a pass or an indicator of an exceptional level of smoothness. Are you actively measuring mottle or is the assumption once again that if SID is achieved then ink laydown is good enough?
- Circling back to the original question; "What can I expect beyond clean print and great ink laydown?" The detail flat-top plate material adds to HD Flexo and other MicroCell screening technologies is simply award-winning. You don't have to look far beyond the annual FTA's Excellence in Flexography Awards to understand the highest level of printability is being executed with flat-top and the industries latest screening technologies. Flat-tops combined with improved screening solutions deliver fantastic ink coverage, often eliminating problematic edge skips, reducing dot gains, improving circularity, and minimizing slur. Because they offer more consistency, it translates on press into higher built ink densities, rich expanded gamut, and far greater contrast. That's about 9 more print attributes that can be a true differentiator.
Check us out next week when we answer the question, “Using Flat-top dots, you will likely experience faster press set-ups with fewer adjustments through the run. How?" Watch for our upcoming BLOG "Optimal Plate and Print Analysis - the TSG Difference." This BLOG explains how some of the above-mentioned improvements to Circularity and Slur are measured, and so much more!
If you want to learn more about this subject, please feel free to reach out to us by calling 1-800-445-4017, or by e-mail at [email protected].
All Printing Resources has formed our Technical Solutions Group (TSG) to encompass our full range of expertise in all critical areas of the flexo process. This team is made up of industry professionals dedicated to being up-to-date on new technologies along with best practices. They are armed with the latest in diagnostic tools and are experienced in problem-solving that can achieve sustainable results. The TSG has walked in your shoes, and have felt your pain.
Click here to read: Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9, Part 10.