Day three of the FTA Fall Conference didn't disappoint! With opening speakers taking a deep dive into color science and the math behind it, the audience had to put on their thinking caps from the very beginning. I think that's one of the best things about the Fall Conference - it gets quite technical!
Mark Mazur (formerly of DuPont) opened the session with a talk about the importance of hue angle, as opposed to solid ink density for color accuracy. We are looking for a color match after all, so shouldn't we focus our measurements on color? Mark's main points were as follows:
- Solid ink density specifications in FIRST basically have not changed in 20 years.
- Solid ink density is not as critical as hue angle for color matching.
- Increasing SID does not usually increase Chroma.
- Matching hue angle makes achieving gray balance much easier, therefore improving color communication across the supply chain.
- This ties in perfectly with the concept of SpotOn Flexo! Read more here!
Next up, John Seymour (John the Math Guy)spoke about the equations behind color measurement as we know it. It all got quite complicated, but in John's unique style, he made it all make sense to all "non-geniuses" in the audience (even me!). John explained some of the shortfalls of the widely-used Murray-Davies equation, but how it is still useful for process control. Here are some highlights from John's presentation:
- Murray-Davies equation (est 1936) : an explanation...
- Picture a halftone, 20% printed area, 80% paper exposed...
- 100 photons hit paper > 80 hit paper > 72 reflect/8 absorb (90% reflectance)
- 100 photons hit paper > 20 hit ink > 1 reflect/19 absorb (5% reflectance)
- Total of 73 photons reflect back in this scenario
- According to this formula, 50% acts like 70%.
- Murray-Davies prediction is really just used for process control (not great)
- M-D prediction error is “enshrined” as the target “dot gain” for printing
- Works well for CMYK but not for spot colors
- SCTV Equation is a better way!
- Spot Color Tone Value
- Defined in ISO 20654
- Loosely based on human vision
- Equation to quantify halftones – also defines target values
- Not compatible with TVI:
- Use TVI for process colors (ISO 12647.15339
- Use SCTV for spot colors (ISO 20654)
- Use SCTV for OGV in expanded gamut printing
Day Three wrapped up with a question and answer session, featuring a panel of industry experts. There was a lot of discussion about issues that face packaging printers on a daily basis. Here is a summary of that discussion:
Panel: Carl Cecil (Color Resolutions International), Jean Jackson (PraxAir), Jim Kulhaneck (DuPont), Paul Lancelle (Kodak), Al Bowers (RR Donnelly), and Rory Marsoun (Esko)
- How big of a factor is press maintenance?
- Jim – absolutely essential to maintain uptime.
- Carl – crucial so that you can schedule production, not let the press determine your schedule
- Explain the difference between bump, dot gain, and calibration curves.
- Al – explained all three (I think we know this) J
- What is the best way to extend the life of an anilox roll?
- Jean – ensure that team members understand the importance and structure of the anilox roll, so they can handle rolls/sleeves properly. Proper press maintenance and blade settings are also crucial to prevent scoring. Utilize your suppliers to get training.
- Audience: What one thing will have the biggest impact on packaging in next 5 years
- Carl – Digital printing
- Jean – Hybrid printing (Digital + Flexo)
- Jim – Plate screening
- Al – Low migration UV inks
- Paul – The skills gap
- What is the expected life of an .067” plate?
- Paul – from 15,000 to 15 million impressions. Application, press setup, and many other factors contribute, so it varies greatly. Like tires on your car, if something is out of alignment or extreme conditions exist, plate life can be shortened. The best practice is to track plates in your process to get a standard and find those situations where plates do not meet the standard – and prevent those situations.
- Al – conversation should be “what can I do to improve my plate life” and not “how long will your plate material last.”
- Rory – plate handling is key, especially in narrow web applications.
- Customer specific issue asking about bounce issue:
- Jim – long plate exposure times can cause bounce (?!) and also check tape selection. Also try using a new doctor blade to eliminate any chatter. Check ink sequence to ensure there is not a trapping issue.
- Jean – check blade setting first (get supplier involved), and ensure the bevel is facing away from the anilox. Also check anilox to plate impression.
- Rory – check image layout and stagger if possible.
- What’s the best way to minimize hard edges from a prepress perspective?
- Al – screening technologies and plate options that area geared to printing fine highlights. Take advantage of new technologies. If you’re using older equipment, try buying an advanced screened plate from a trade shop to see what it can do for your print results.
- Rory – How about on press?
- Jim – Check anilox volume and make sure it’s appropriate for the LPI.
- Jean – Use proper plate cleaning practices
- In the corrugated market, high end graphics are increasing. Consistency from run to run is an issue. What is the best way to get more consistency across the board?
- Jean – Manage your anilox roll inventory. Consider a different doctor blade choice if using a standard poly blade.
- Carl – Training and education are key. Accurate drawdowns onto the substrate for the specific job, minimize variables throughout the process.
- Rory – dedicate the time to proper QC, and get buy in from management.
- How can a blade potentially damage the anilox, and how can I determine my blade unit is set up optimally?
- Jean – when using steel blades, use filters/magnets. Poly blades can allow particles to embed in the blade and cause scoring. Ensure correct blade angle is being used to prevent excess wear. Send worn doctor blades to your supplier for analysis.
- What are best practices for keeping each ink type printing optimally?
- Carl – control pH on water based inks. Always check viscosity.
- Jean – don’t mix ink brands. Only use “extender A” for “vendor A”
- Audience: What is the origin of the YMCK print sequence?
- Al – depends on the ink system, and should be optimized (recent Flexo magazine article). We only say CMYK because its conventional. With heavy GCR, it is a good idea to put black down first.
- Joe Tuccitto - Also press technology for registration may dictate ink laydown order.
- Carl – Ink trapping determines the ink sequence. It is also substrate-dependent. In corrugated, KCMY is the typical ink order.
- What is the best method for ink drawdowns?
- Carl – mechanical proofer for consistency from proof to proof
- What is the recommended temperature for running solvent based inks in wide web?
- Jean – There is an FQC project based on this, starting with narrow web. You can do your own optimization to determine the best temp for your plant.
- Jim – around 80F is the point where problems usually start to occur.
If you would like more information on what Fall Conference was all about this year, we are happy to answer any questions! Email me at [email protected] and let's discuss!