When it comes to flexography, “committed” is being bound to the process and devoted to the steps that make the process successful.
Without commitment, you will not achieve the desired results consistently. While today’s technology gives you much more capability, it still takes the craft to realize the potential of your printing process.
Furthermore, there are many steps to optimizing your process, but none are worth the time it takes to perform, if you do not follow up with a level of commitment befitting your desire to improve those processes.
Craft and commitment go hand-in-hand for the printer. A shared commitment must also reach from the top of upper management to every position within the company. You would think that would always be the case, since management has requested the improvements, but then there is the obstacle of communication.
All photos courtesy of Harper Corporation of America
Critical Objectives
Typical goals are improved quality and consistency. Both usually come from the improvements in communication and methods of taking measurements throughout the process. Reduced downtime and the frequency of rework as well as reduction in raw material waste is to be expected.
Part of the problem here seems to be a lack of communication; no one has conveyed to management that there will be an initial investment of time and capital to carry out the project. Sometimes this revelation alone will scuttle a project. It is not by accident that Flexographic Image Reproduction Specifications & Tolerances (FIRST) 6.0, published by FTA, starts with a chapter on communication.
Clear communication is vital all through the process, even in the planning stages. Goals should be clearly stated, and specifications agreed on to prevent discrepancies later. There should be a timeline established that includes the steps to be taken and who is responsible for each.
When dealing with various vendors and clients, small things like not designating an agreed-upon file format can slow the design or prepress workflow. The same goes for color management or pigment selection. What is accepted as a common practice in one trade may not be the benchmark in another.
One obstacle to staying committed is the fact that this whole process can lead to making changes to the way things are done or raw materials are used. It is a given that humans normally resist changes in their routines.
Optimization
It can be disheartening for converters to realize that current production capabilities are not where they had hoped. The initial measurements from the optimization run may indicate that some mechanical improvements (capital outlay) will need to be made. If everyone that is going to be involved is included in the planning stage, things will go much smoother.
Internally, this includes press operators, assistants, ink and prepress departments, and a level of management that will approve testing and press time. All outside vendors that will supply any part or service to the project must be included. While your vendors are all together and involved in the planning stage, it is important to listen to them and take advantage of their expertise. Obviously, they want to provide you with their products, but they also have a wealth of knowledge that is there for the asking. Once you get everyone committed and communicating, then you get engagement.
The print optimization will focus on the mechanical and physical performance of the press, the components being used and how each is utilized. This will include substrate, plates, mounting tapes, doctor blades, anilox rolls, inks, print cylinders or sleeves, plate processing systems, plate mounting, etc.
Fingerprinting
Practicing regular, thorough preventative maintenance should also be a routine occurrence at your plant. Performing a total press cleaning does not sound sexy, but it is necessary for an accurate fingerprint. It will also help with repeatability and consistency.
The press should be capable of reproducing the same level of performance and results every day. New presses are likely able to perform at the peak of their performance level. Unless tests are performed routinely and compared to the original capabilities, the wear and tear of day-to-day usage will slowly change the efficiency of the machine. You want to address any issues that hinder the press’ potential. Keep in mind:
- Worn plate cylinder gears, even on servo-controlled presses, can alter the image and process dots. Check to be sure gears are clean and free from signs of wear, like sharpened teeth
- Plate cylinder and anilox rolls should have the bearings checked, as worn bearings can affect impression settings or allow bounce
- Print stations should be checked to ensure all are in alignment and parallel. This goes for nip, drive and idler rollers as well
- Rolls that are out of alignment can cause loose edges on the web, wrinkling and poor register
- Make sure all tension controls are functioning properly
- Dryers need to be checked to establish that airflow is at the proper levels and to make sure the exhaust flow is greater than the intake to prevent excess air current around the plates, causing dirty print and reduced solid ink densities
During your preventative maintenance routine, it would also be a great time to have your anilox supplier conduct a proper anilox roll audit. Since anilox rolls are considered by most to be the heart of the flexographic process, knowing their condition can help you determine if they can perform as expected, not only at that snapshot in time, but in future production runs as well.
If the press cannot repeat regular production, stop the process until it can reproduce acceptable print on a regular basis. Many of these preparations and corrections go overlooked during normal production because the press is perceived as running good product most of the time, and therefore must be in good order.
Recent studies show narrow web presses are “down” as much as 35 percent of the time. Unless that downtime is recorded, it can be very difficult to determine what is mechanical failure versus process failure that stops production.
Some of your goals for the optimization will likely be internal process improvement objectives. Some may come from having to match other prints, a given customer item, gravure or offset prints, or other sources or files.
Process parameters that should be tested are process colors, spot colors, gray balance patches, wet trapping, tonal scales and vignettes. The mechanical parameters will most likely include impression/slur targets, register targets and solid ink density patches. Depending on your goals, the list may include more.
Planning, communication and documentation are key elements to the successful characterization. One other often-overlooked element of the fingerprint is testing to the point of failure. If the press proofs of the test patterns you have chosen to run do not have some areas where there is failure to print equal to the artwork, then you have not tested to, and therefore do not know, your limits.
For example, you currently print down to a 5 percent dot, if you only test to a 5 percent dot area, you may not realize you can print down to a 3 percent dot without any loss in print quality. As small as they may seem, it is these little improvements that will lead you to the optimized promise land of high-quality flexography.
During the fingerprint, if no parameter changes came from the optimization, the press should be equipped with clean anilox rolls, new doctor blades, and fresh inks that are to specification. Plates should have been made with no curve applied in prepress.
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