Plasma Spray
There are two types of plasma spray materials used in anilox processing.
- Metallics, which are applied to the base material to help with bonding and protecting. These can be applied with HVOF process or wire
- Ceramics, of which the most widely used in the industry is chrome oxide. Chrome oxide is sold in different sizes and shapes. Hardness of the ceramic is based on application and engraving temperature
Anilox Engraving Formations
There are two different classes of engraving formations: closed and open. Closed-cell engraving will be completely surrounded with walls. This allows for a controlled amount of material release, based on the segregation. This type is most commonly used in the printing industry, so I will start there.
Closed Cell
All photos courtesy of Interflex Laser Engravers
The most commonly engraved closed-cell formation is the 60-degree hexagonal engraving. It is easy to recognize as the cells form a beehive-type shape. This has been proven to be the most-efficient cell configuration for most printing applications; as a result, it is the most widely used cell in the industry. The 60-degree hexagonal is a proven shape and should be the first considered in most printing applications.
There have been a few modifications made to this configuration, developed to help with the shortcomings that can come with the 60-degree hexagonal shape.
The elongated cell was developed to provide the ability to increase volume, but still keep the LPI high enough to work with finer plates. Instead of increasing the depth of the cell—which will lead to reducing its efficiency—the cell is instead elongated to allow for it to remain shallow. The shallower the cell, the more efficient it will be. The engraving angle will change based on the amount of elongation.
The stepped hex configuration is also a variation of the 60-degree hexagonal cell. It has elongation and is stepped in the vertical plane. This has been shown to help increase the efficiency of the elongation and improve density on some white applications.
Open Cell
Open-cell configurations are identifiable by a trough or channel that contains no walls. This allows for more release and can help when using large particles or viscous materials. The open-cell formation is used mainly with coating applications but has found some activity in printing applications. These engravings are the tri-helical and channel-type engravings.
There is also an open-cell configuration—reverse engraving. This engraving has no walls, just center pins. It is used for viscous materials and/or when you are in need of very heavy coat weights.
LPI & Volumes
Once you have found the correct cell configuration, you next need to look at screen count and volumes. Screen counts are identified by either LPI (lines per inch) or LCM (lines per centimeter). These will be determined by application, plate LPI and dot size.
Volumes are identified by either BCM (billion cubic microns per square inch) or cm3m2 (cubic centimeters per square meter). This is the amount of material that will be delivered to the printing plate.
It is important to take the depth of engraving into consideration when you are looking for a linescreen and volume. The higher the linescreen, the smaller the opening of the cell. This means if you want to have a larger volume, you will need to go deeper. The deeper the engraving, the less efficient that cell becomes. I always recommend to keep the cell as large as possible to meet the specifications of your plate and as shallow as possible to meet your volume needs. This allows for longer run life before cleaning and will also make cleaning much easier.
The volume card above contains a list of screen counts in LPI and a range of normal BCM to high BCM ranges.
Finished Product
Once you have successfully completed the project, you will need to be able to do it at a large scale. Ownership for this falls under the category “all.” As the printer, you will need to document everything that was done to achieve your goal. As a supplier, you need to maintain the products you supply to ensure continued success. Printers and suppliers will need to work together to make sure the pieces continue to fit together properly.
As an anilox supplier, my responsibilities would be the following:
- Supply a consistent anilox roll/sleeve to my customer
- Audit the inventory on an annual basis
- Train personnel on handling my product
Supply a consistent anilox requires a lot of work behind the scenes. Examples:
- Documentation of the testing of your plasma spray powders
- Independent lab testing of spray materials sent out on a monthly basis
- Independent calibration of spray equipment on an annual basis
- Documentation of engraving specifics for each anilox
- Volume readings based on electronic and liquid measurements
- Calibrating electronic measuring devices on a continual basis
- Servicing and documentation of the lasers on a continual basis
- Continual training of personnel
Anilox Audits & Training
It is important that you have an annual audit to see the condition of your anilox inventory. It is also a good way to make sure that you don’t have any issues with cleanliness, wear or damage. One key to a successful audit is to make sure you have the rolls cleaned. Measuring dirty rolls will not give you an accurate assessment of your inventory. Instead, it will provide bad data that could cause you to remake a roll that is just dirty.
Training is also important to maintaining the finished product. If you are mishandling or damaging the key pieces of the puzzle, it will not fit together. Interflex Laser Engravers offers an Anilox 101 program that can be set up for anilox sleeves and rolls. It is a PowerPoint presentation that takes, on average, about an hour. It covers the “dos and don’ts” on handling the anilox, as well as some issues that we have seen happening around the industry. Your anilox supplier should offer a similar program.
In the case of engraving, training can be personalized to your location. A supplier can come in and discuss the issues that you know of, look over the process and identify an issue that you may not know exists.
Training with other vendor types is also an option. For example: Interflex Laser Engravers has conducted training classes with ink suppliers and doctor blade vendors. This training helps vendor partners understand the issues that are occurring, so they can collaborate on a fix. It also lets the press team know that vendors are working together to solve problems.
Vision Fulfilled
In the printing industry today, there are a lot of questions and confusion. Think about the moment when you first open up that puzzle box: a daunting task awaits—there are 500 pieces jumbled up in front of you. The first thing I do is find the border pieces. In this case, your suppliers are your border pieces. They can help you set the limits of their products. They give you a guideline to stay within. Once this is completed, the correct suppliers can help you fill in the other pieces until your vision is complete.
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