Anilox Audit
The first thing that needs to be asked is, “What is the current state of your anilox inventory?” If you were to walk your shop floor, chances are operators will have their own go-to anilox rollers. They will have a good gauge on their anilox performance, but this understanding must be taken to a higher level to meet pressroom needs. This could potentially be the originator of any color inconsistencies you might be experiencing during a color match. But how do we find out the condition of our anilox rollers? Two words—anilox audit!
Anilox audits are a great tool that will help you identify the three main components we have discussed, as well as the anilox condition, so you can understand better what you have and the role each anilox can best play in your production environment.
An audit will also help in identifying which anilox rollers are damaged. A damaged anilox will have many signs, and with the help of your anilox supplier, you can identify the sources of damage and eliminate them. Chipped edges, score lines, worn cell walls, broken cell walls—these are just a few that can be brought to light by an audit. There is nothing more frustrating for printers than to have an otherwise perfectly good engraving get needlessly damaged and render it useless.
- Chipped edges are usually caused by handling. Bringing an anilox in and out of press and hitting the press frame is a good example. Another way to get chipped edges is when moving a roller into storage, sliding the sleeve or roll to the back or bottom of a rack and making forceful contact. A doctor blade unit, sling guard or chamber not properly attached or inserted could also be a culprit. Additionally, corrosion can also loosen the bond between the ceramic and the base and allow the ceramic to flake away
- Score lines are a tricky defect because they may or may not show in print, and finding the source can be difficult without assistance. Sometimes they are not deep enough to see in the print but are readily identified visually. Sometimes they fall right in the print area and cause an undesired print quality. Identifying the sources of contamination that get in the ink and between the blade and anilox, causing the scoring, is a task with which your anilox supplier can help
- Worn cell walls will cause an ink color to print lighter than what came out of the ink department and should be taken out of rotation. Wear can come naturally from use, but you would also have to consider blade pressure, blade holding equipment and abrasive inks (see Figure 4). One of the most important functions of the anilox audit is to identify worn rolls and get them out of circulation without resorting to press trial and error
- Broken cell walls will cause an ink to print dark spots. If you have a 700 lpi anilox that has broken cell walls, those cells go from 700 to potentially 500 in those areas, meaning lost dot support and unwanted increases in volume where those spots are located. An operator could be chasing an issue for which he or she will not find an easy solution
Another way an audit will help is by identifying the linescreen and volume of those few anilox rollers that are not marked. We all have seen anilox rollers that are older and have had their identifying marks worn down and made illegible. This will also be helpful in identifying where the proofer roll in your ink department is printing.
When the audit is graded and returned to you, you will have an EDV value (echotopography digital volume) and a 3D image of every anilox that you can then review and determine which should be cleaned and returned to inventory, monitored in future use, and which ones should be removed and replaced (see Figure 5). EDV is the measured volume of bcm.
If you own anilox rollers that are scored, have chipped edges or are dinged, you may want to consider replacing those as well. These are factors that can cause print defects. If the doctor blade gets pulled back due to a chipped edge, it may look like a gear mark. A score line or ding can cause a void on a full reverse print on an anilox that otherwise matches the color perfectly. Those are just a few problems that could come about from damage that is visible. An anilox audit helps identify both issues that are visible or not visible to the naked eye. When the anilox base condition is salvageable, you have the option of remanufacturing those engravings as well.
Achieving the full potential of your anilox inventory starts with understanding the linescreen, volume and geometry, then partnering that knowledge with proper inventory management and the useful tools the anilox audit provides. Who would have thought that all this information could have come from an anilox audit?
Knowing the different components of an anilox, and how they play a role in your application, will help your workflow move smoothly out your shipping doors.
About the Author: Richard Hernandez is a sales/technical service representative – Western Region for Harper Corporation of America. He brings more than 24 years of extensive experience in the printing industry with six years in offset printing and 18-plus years in flexography. Within that time, he has gained extensive knowledge of Webtron, Nilpeter, Comco and Mark Andy Inc presses, as well as A.B. Dick and Heidelberg offset presses. Richard began his flexographic career at Los Angeles Label, which led to production lead and supervisory experience at The Label Co, and Paradigm Label in California. Prior to arriving at Harper, he was the print manager at Precision Label, which helped him excel in his color matching, team member training and mentoring, and troubleshooting skills. While there, he also assisted with the R&D and product development that helped drive the company into industry leading trends.