UV inks are notorious for spitting issues. How does your technology solve it?
BATISTATOS: On our Ultra Z, we have changed the dynamic of how ink flows on and off the surface of the roller. Instead of air being trapped in cells, the open concept of the channel doesn’t trap air, causing the ink to be turbulent. Instead, ink is allowed to flow smooth, which eliminates or reduces the spitting effect.
HARVEY: Spitting is not only an anilox issue—ink rheology, temperature, the doctor blade and the press also contribute. Apex’s GTT guarantees against spitting for the life of the anilox roller. Why is that important? Did you ever have an anilox roller that worked perfect for 12 months or two years, and then suddenly began to spit? Open-cell structures that rely on broken walls and slightly lower walls always have the risk that when the surface wears down, the open structure will become closed. When it becomes closed, the risk of spitting is increased significantly.
WOODARD: We find that extended or elongated hexagonal open-cell engravings relieve pressure on the doctor blade and offer improved ink flow and decreased spitting. However, we feel that the cleanliness of the press and type of doctor blade used play a major role, as well.
POULSON: Harper’s new XCAT is an open cell with a complete formed cell pocket below the channel floor. It has the open channel for better release, but the cell pocket keeps better control of ink transfer than your typical open-channel engravings. It has proven to eliminate spitting across volume ranges from 1 bcm to 15 bcm. Other benefits of use reported to date include: no chatter at low volumes, elimination of trail end voids and improvement in quality of reverse prints. This can be utilized for all types of graphics—screen, combo and line work—as well as coatings. The improved print quality will also work well on cold seal, matte and other coatings.
XCAT geometry has shown improvement with water and solvent, as well as UV inks. It has been primarily utilized by UV printers, mainly for its improvement with spitting. Eventually, word will get around.
MIDDLETON: There are variables when it comes to reducing spitting. Interflex Laser Engravers offers a UVFlex cell designed as a good alternative for those who are seeing spitting and/or misting issues, particularly if they are currently using 60-degree or 30-degree hexagonal engravings. The stepped design of the UVFlex helps to reduce the chance of ink building up on the wrong side of the doctor blade and can reduce spitting and/or misting issues.
RASTETTER: Here’s where a channeled engraving comes into play. Back in the 1980s, Pamarco patented the first channeled engraving called RotoFlo; an engraving with a defined cell to hold and control the ink while providing a channel between cells. These channels are created by reducing a portion of the cell wall by one-half to one-third. This reduction allows limited ink movement to relieve pressure buildup in the cell—one of the key causes of UV ink spitting. RotoFlo’s modern equivalent is our EFlo UV.
It is important to note that before deciding on which engraving is best suited to your application, it is first necessary to determine a few other things. For this reason, Pamarco’s methodology for creating engraving recommendations always starts with a client consultation to establish a relationship and learn about their objective. Motivation ranges from improving what they are doing today to new jobs that require different or unique anilox specifications.
After this initial consultation, we identify the bcm required to print the given jobs. Only then do we start talking about lpi and the type of engraving that will best fit the application. As I said, the most critical aspect of producing a quality engraving is to ensure we are maintaining a 25 percent to 30 percent depth-to-opening ratio. Doing so produces an efficient cell from an ink transfer standpoint and one that is capable of remaining clean for longer periods of time. This means that you don’t have to experience dirty print and you get a cell that is robust for the longest possible life.
BEESON: UV inks provide vibrant colors and super high resolution, but due to the highly viscous nature of the inks, have always been at the mercy of ink spitting. Using closed-cell technology has only made the issue worse. By understanding the problem, Sandon succeeded in overcoming it. See, you cannot compress a liquid. If you do, hydraulic pressure builds up in the cell and forces the blade to lift. You get ink spitting or ink passing. We created the Fluid HEX and Fluid UV channeled open-cell systems that give a mechanical solution to the problem, via an open channel, which acts as a release valve for the pressure. It takes the hydraulic force away, so the blade cannot lift and the ink cannot spit or pass. We still retained a conventional cell structure so the anilox can be accurately measured, cleaned and monitored.
What is your method for providing engraving recommendations?
BATISTATOS: We combine a little bit of experience with a little bit of science. You can usually look at a job and be able to make initial recommendations but in today’s world, with so many variables, from higher technology plates to stronger inks, the best method is a banded roll, where you can test multiple engravings to really finetune what you need.
HARVEY: Anilox specs are not just numbers. To be an ethical and professional supplier, it is key to understand each customer’s needs, but it is more important to be able to advise the risk and consequences of providing the anilox a customer requests.
Apex takes the responsibility to advise and supply a product that is fit for its purpose seriously, we advise a product that meets the needs of our customers at the same time ensuring that the decision our customers make is based on all the facts related to the performance of that anilox.
Apex has a technical specialist in ceramic coating, roll body and sleeve construction, laser engraving and anilox performance as an application. These four key areas of specialty ensure customers have access to the best advice when they are considering the significant investment.
WOODARD: There are numerous variables to consider when making an anilox roller recommendation—type of press, press speed, type of ink, substrate—coated or uncoated, plates, screen or process printing, etc. If print samples are available, we certainly use these for further analysis.
POULSON: As long as I know the screen percentage of the plates a customer is running, I can make a recommendation; but if we are looking into heavier applications, like coating ranges, we need to look at the product’s coat weight. To determine that weight, we need the technical data sheet, safety data sheet and percent of solids used, as well as pounds per gallon. Once the technical team has this information, it can make the proper recommendation and then make sure the customer understands how we got to that specification.
MIDDLETON: Because there is no one answer that applies to all applications and each customer will have its own unique printing needs, the first step in our methodology is to understand the customer’s process. This includes familiarizing ourselves with the substrate(s), ink type, plate technology, doctor blade, and history—what has worked in the past. This information is needed to understand their requirements.
BEESON: There are lots of moving parts to this question. When we work with customers to achieve what’s needed, volume is vital, as this will control the optical density in most cases.
The next step requires that we look at linescreen of the anilox. Yet, there are many things to consider:
- What plate is the customer using: conventional or flat top dot?
- What is the plate linescreen?
- What ink system: UV, solvent, water based or a combination?
- Is there a coat weight the customer wants to achieve for haptic or metallic?
- What is the substrate: OPP, kraft, vellum or EVOH?
- Is there an existing standard that needs to be considered?
All these factors play a significant part in the recommendation process.