Flexographic printing parameter control

Mike Huey of Harper Graphic Solutions listed several uses of ribbon anilox rollers in flexo printing.

Ribbon anilox roll has been used by printers for many years. Its role is reflected in many aspects, such as determining the ink volume of four-color printing, determining the optimal number of mesh lines and mesh volume of anilox roll for spot color printing and combination printing. , determine a reasonable anilox roller inventory. These are the most common applications of ribbon anilox rolls, and their use is now beyond the above range and extends to other areas.

For example, it is used on some occasions to determine the hardness of the plate, the density of the double-sided tape, and the ink supply system used. Using belt anilox rollers can also determine the specific parameters of each process to ensure daily print quality, these are very good methods.

Flexographic printing is both an art and a science. However, in actual production and processing, we need to optimize the technological process in order to obtain maximum profits. As we all know, the anilox roller is a very critical component in flexographic printing and is called the "heart" of flexographic printing. In this article, I would like to introduce some of the common and unusual uses of ribbon anilox rolls. No matter which market area you belong to, I hope to help your company reduce production costs and increase profits through this article.

Determine the optimal amount of ink for line drawings, gradation printing, and line image synthesis

Plan ahead:

We all know that in order to ensure the stability of daily printing operations, we must determine various parameters, and strive to adopt the best way to ensure the quality of printing. Use of belt anilox rollers is very easy to implement. But first we should call the relevant personnel, suppliers of printing plates, inks, sticker tapes and anilox rollers. Of course, printers must participate, printers should let the press operators and their supervisors, and a manager People and project managers are involved. This meeting should determine the anilox parameters used, the hardness of various plates, and the type of ink and double-sided tape. All the variables that need to be tested should be enumerated, confirm the test plan and collect relevant data.

One thing to keep in mind is that the ultimate goal is to determine the minimum amount of ink required for line art, four-color level drafts, and complex manuscripts to achieve the required field density, and to expand the reproduction range of the tone. This means that in order to achieve the smoothest, thinnest, and most stable solid density, a variety of hardness plates and tapes are required.

Test log:

The printing of any work is the same. Prepress preparation is to ensure that all materials are in place before the trial begins. The approved test list should ensure the accuracy of each step, just like the routine print jobs, list the parameters to be tested, the proofs to be saved, etc. in the order of the test time. Printing presses, ink, tension, temperature, and all other control parameters should be printed in peacetime. If the usual ink viscosity is 24s (#2 Zahn cup), the test can not be 28s. Print quality standards are also the same as printing jobs at peacetime. Normally, there are control bands at both ends of the anilox roller. The control belt means that the width of both ends of the anilox roller has the same number of screen lines and the volume of the net pocket. It can print simple inspection items at both ends of the printing material to check if the axial pressure of the anilox roller is balanced. Once it is determined that the pressure setting has reached normal operating conditions, all equipment operating parameters can be recorded and the printed sample can be labelled/coded for future inspection and testing. Specific test parameters, such as labeled samples and recorded printing conditions, are critical to the success of the test. Sample proofs, parameter tests, and charts are shown below:

The density obtained under the condition of 800 lpi mesh and 1.9 bcm cell volume is closest to the requirement. Although the dot enlargement was slightly larger than the 900 lpi and 1.7 bcm anilox at this time, we still decided to use an 800 lpi, 1.9 bcm anilox roll, because the dot gain could be solved by compensation. After the trial is completed, the participating parties should discuss and determine the specific criteria, ie, the conditions necessary to achieve the desired result. The printing conditions for each type of work should include ink, anilox, printing plates, and double-sided tape. It may be that we often participate in or implement this type of experiment. In fact, the key is to list all the data and determine the final cost/benefit ratio. It depends on your core business, customer needs and expectations, and then decide what kind of tapes, plates, inks, etc. to use to meet the business requirements of both parties.

Ribbon anilox roller for white ink printing test

Above, we briefly discussed the most common uses of ribbon anilox rollers. Through the standardization of the printing process, printers can help improve the stability of print quality, reduce downtime, and minimize the impact of uncertainties. Printing white ink using a belt-shaped anilox roller is not as common as the above application, but experiments have proved that it is effective in determining the minimum ink layer thickness while reducing the cost of white ink, that is, the opacity requirement. As with the above experiments, we also need to open a team meeting to determine each parameter. The key to this experiment is to determine the appropriate volume of the cell, and the corresponding hardness of the plate and double-sided tape, in order to ensure a uniform, pinhole-free field. Based on years of experience, we know that the fewer pinholes, the more uniform the ink layer and the higher the opacity. I also know that many printers do not test opacity and can also reduce costs through other means. Why don't we use an anilox roller with 7bcm, 8bcm, or 9bcm nets to achieve the corresponding opacity? If we change the 9bcm anilox roller to 8.5bcm, it means we can save ink costs by 5.5%. After a simple mathematical calculation, you can understand the impact of profits within a year, because all inks and prices depend on the amount and type of ink. For long-term cost considerations, the use of ribbon anilox rolls and other anilox rolls for white ink testing is a good value.

Whether it is narrow-width printing or wide-format printing, white ink is the most commonly used printing ink, and it is also a relatively high cost component. Despite the different application scenarios, there is no doubt that if the processing is done properly, the production cost can be reduced, that is, the opacity required by the customer can be reduced and the white ink thickness can be reduced. The volume of the anilox roller pocket is not the only factor that determines the cost. Many relevant tests are still in progress or have passed tests, such as the use of different hardness of double-sided tape and printing plates to obtain the corresponding opacity. On a printed image, the opacity depends entirely on the size of the pinhole. If the number of pinholes is reduced, the opacity can be increased accordingly.

The key to reducing costs is to optimize the printing elements: double-sided tape, printing plates, and anilox parameters (line number, cell volume, and cell shape) to achieve the best ink release and spreading in a given area, thus avoiding Light passes through the ink layer. The following describes an anilox roller that uses the same number of screens, the same volume of the cell, and the shape of the cell, but the hardness of the plate and the double-sided tape are different, and finally a completely different opacity is obtained.

Ribbon anilox roller for coating test?

In one occasion, ribbon anilox rollers are rarely used, but there is a possibility that the company can greatly reduce coating costs. Compared to the past, the application of coating in flexographic printing has been significantly reduced. Nowadays, there are more applications for coating in specialty printing, such as coatings on the market that change color with temperature, safety coatings and special coatings for cell phone batteries.

In fact, almost all imaginable prints require paint. UV, waterborne, and solvent-based adhesives are used in almost every material. In simple terms, if you don't currently have a dedicated coating facility, I believe you will buy it soon.

In order for the material to achieve the desired function at the time of design, the amount of coating applied must reach a specific thickness.

Most paint manufacturers have a recommended range, which is the amount of coating needed for a particular application, and the key to the problem is to find the minimum amount of coating that meets customer requirements. For example, if the recommended amount of coating is 1.0-1.25 lbs./3000 square feet, we should design a roll to reach this range. Based on the relative performance of the coating, the cell volume of the anilox roll needed to reach this amount can be determined. Then, when we design an anilox roller, we can use an anilox roller that is slightly higher or lower than this value to test to determine the optimal coating amount for a specific application. Based on the test results, we can take some proofs to test the specific performance required by the customer to determine the “small” amount of coating required to meet customer requirements.

For example, an anilox roller of 4.5 bcm is too small and 5.5 bcm is slightly higher. A 5.0 bcm anilox roller should be the best choice. Using a 6.25-bcm anilox roller, the cost of the processor can be greatly reduced in terms of 1.25 pounds per ream of coating. Although the coating effect obtained with the 6.25-bcm anilox roller can reach the standard, why do you need to apply 20% more adhesive / coating? You should not think that saving 20% ​​of the adhesive is not worth paying attention to. This is a common example. To ensure coating performance, use an anilox roller to reduce the amount of coating. If other parameters in the actual printing change, the printer is responsible for monitoring, testing and recording the amount of coating to ensure that the reduction in the amount of coating does not cause quality problems and cause customer dissatisfaction.

Through the above introduction, we can see that the belt-shaped anilox roller is very versatile. It can be used to improve the quality of printing, standardize the printing process, and of course, the most important thing is to reduce costs and thus maintain competitiveness. The last thing to be reminded is that after the test is completed, the printer needs to take care of the ribbon anilox roller. My advice is to thoroughly clean it and store it in a safe place. Ribbon anilox rollers may be used frequently, such as new printing plates, inks, double-sided tapes, coatings, etc., on the market. We can use belt anilox rollers for testing and can also be used as quality control equipment to determine daily printing. When all material properties are stable. If some parameters are found to be different, you can re-check according to the data recorded during the test.