Improvements in laser technology, software, processing and ceramics have allowed anilox manufacturers to create new specialized patterns. These new patterns have added opportunities printers never had before. It can be a bit challenging when you are trying to order a new anilox for a project.
Do I go with a standard hex or with an elongated cell? Do I go with a channel or a tri-helical? What angle do I need? Do I stick with what I know or do I try something different? It can be overwhelming (see Image 1)!
I suggest you begin by talking with your anilox roll engraver. They should be able to provide you with information on the product they sell. When I am approached by a customer, I like to ask a few questions. I call them “The Whats.”
- What are you doing now? This information will help us understand what we have to work with such as types of ink, substrate and drying capacity. It also provides us with historical data that we will need to move this project forward
- What are you trying to do? This is critical information to know up front as it will give us the customer’s expectations. It can also allow us to know if what they want is even possible in the first place!
- What is the timeline of this project? Answering this question will let us determine if we need to remove as many variables as possible and use technology the customer currently has, or if we have time to look at different ways to improve the process
Once we have gone over these questions, we can get to work.
One of the most common issues I come across is with white inks. The two questions I most often hear asked are “How can I increase my density?” and “How do I fix my pinholing issue?” Here are some of the recommendations Interflex Laser Engravers has given to help our customers with these issues.
Increasing White Density
Density is the perceived darkness of a substance, material or image which is caused by the absorption or reflection of light encroaching on the material. In printing terms: it’s the “POP” that catches your eye.
The more light the image can absorb, the better the density. Density improvements can be accomplished in many ways. Ink, plates, substrate preparation, volume and smoothness of the ink layer—all of these factor into the density of the image. We have several slight changes as well as cell configurations that have proven effective for white density improvement. It is important to make recommendations based on the information gathered in “The Whats.” Here are a few examples of changes we have used to improve cell density:
- Increasing volume: This is usually the first and the quickest option. Increasing volume is not always an option due to other factors such as line count (lpi) restrictions. White inks are notorious for not flowing well. If you have a high line count with a higher-than-average volume, this can restrict the flow even more. It would decrease the run time due to the roll getting dirty quicker and make cleaning the anilox more difficult. Drying compacity and speed can also prevent increasing volume. More ink can mean more expense as well as unexpected issues later in the process
Changing engraving angle: Switching from a 60 degree to a 30 degree angle can help improve the smoothness of the ink layer. The smoother the ink layer, the better the density becomes
- Elongated cells: This stretches the cell vertically around the roll and enables more volume. An elongated cell allows us to keep a high line count and increase the volume without a deeper cell
- Channel engraving: This is an open cell structure, meaning it only has two completely formed walls. This allows for ink to release more efficiently. More efficient ink release allows for longer runs and easier roll cleaning. It can also be done in the 30 degree angle, which could improve ink smoothness (see Image 2)
- Stepped hex: This is an elongated cell that is “stepped” to break up the pattern of a standard 60 degree hex. This allows for high line counts with higher volumes and also applies a smooth, consistent ink layer (see Image 3)
Pinholing, a common print defect in flexographic and gravure printing processes, is represented by an incomplete ink film comprised of small holes. These are caused by the ink’s failure to wet the entire surface of the substrate. In printer’s terms: “Your overall is not over all.”
There are actually two types of pinholing: chemical and mechanical. I am going to cover mechanical, as this is the one that can be attributed to the anilox roll. Keep in mind that pinholing can be caused by plates, inks and drying techniques.
Here are some of the recommendations to cure mechanical pinholing:
- Increasing volume: Pinholing can be caused by insufficient ink amounts being applied to the substrate. If you are using a substrate that absorbs the ink, you will need to accommodate for that loss by increasing the amount of ink supplied
- Channel engraving: The open cell structure can allow for better release, leading to an even and smooth layer of ink that will dry without voids
- Changing engraving angle: Changing the angle from a standard 60 degree to a 30 degree can make the ink layer smoother and allow for even transfer
- Stepped hex: The stepped pattern can help the material lay down smoother with an even transfer of ink
We are commonly asked to help with a specific issue related to ultraviolet (UV) inks. Anyone who has ever been involved with UV inks knows the issue: How do you prevent spitting?
Spitting is caused when the UV ink gets on the wrong side of the doctor blade. This builds up until it is released and ends up places it does not need to be. There has been a lot of discussion about why this happens. We know that although the anilox roll, doctor blade, chamber pressure, temperature and speed have an effect on spitting, the UV ink itself is the main contributor. The advantages that make UV ink so attractive also make it difficult to work with. Here are some recommendations for this issue:
- Changing engraving angle: Getting away from the 60 degree engraving angle seems to help decrease spitting. We have primarily used a 30 degree engraving but have also used others. I believe the better efficiency of the 60 degree angle has an adverse effect on spitting, as it allows the ink to build up faster on the back of the blade
- UV flex engraving: This is an Interflex Laser Engravers term for a 30 degree, elongated, stepped hex. This has been shown to greatly reduce the issue (see Image 4)
Interflex Laser Engravers believes each customer’s issue or request for improvement should be handled as a unique situation. What works for one does not always work for another. There are many variables that can make each case unique. Process, environment, substrate, procedures, housekeeping and maintenance all will play a role. The recommendations provided in this article should be discussed with your anilox engraver.
About the Author: Mickey Bower is the technical manager at Interflex Laser Engravers. He has more than 30 years of experience in the printing industry: a decade of service at Southern Graphic Systems Inc in Louisville, KY from 1986 to 1996, and 22 years at Interflex Laser Engravers from 1996 to present.