Selection and management of anilox roller in flexographic printing
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With the development of flexographic printing, the application of anilox rolls has become more and more popular.
However, how to properly select the anilox roller, as well as the maintenance, cleaning and preservation of the anilox roller, has not been properly understood and mastered.
Anilox rolls have three main parameters, namely: number of lines per inch, cell angle and cell volume. These three parameters are noticed by both the user and the supplier when ordering or processing a new anilox roll. However, from the user's point of view, it is ok to accept the new anilox roller according to the above three parameters, but after a period of time, the state of the cell will definitely change, including the surface wear and scratch of the cell. Or the ink residue or debris in the cell is blocked, the ink capacity of the cell is reduced, and the ink also overflows from the worn hole wall, which causes the ink density of the corresponding ink zone to be inconsistent. Therefore, from the user's point of view, in addition to the above three parameters in the acceptance, it is necessary to pay attention to the fourth variable factor in the future, that is, the state change of the cell.
1. How to properly choose the anilox roller
It is often believed that thinning the thickness of the ink film layer can reduce the release of VOC (volatile matter), so it is recommended to use an anilox roller with a shallower cell. It is true that the ink layer will bring more VOC release afterwards. However, the thickness of the ink layer is mainly determined by the volume of the cell, and the depth and shape of the cell is only one aspect. For example, an anilox roll of 500 lines of shallow dish-like cells per inch and an anilox roll of 1000 lines of deeper and steeper cells per inch may have similar ink layers due to their respective cell volumes. Density may not be different. Therefore, the concept of anilox rolls that tend to use shallower cells is not suitable. The main considerations are: to ensure the best ink transfer and the best ink drying, the maximum LPI (number of lines per inch) is used. Get the best density.
The optimum choice of anilox rolls should start with the construction order for each print. This type of construction order shall provide all information, including the relevant parameters required for the printing press, after obtaining the signature agreed by the customer, according to the needs of each printing. Since the anilox rolls are often used interchangeably in the printing press, it is important to specify the number of lines per inch (LPI) and the volume of the cells (BCM) parameters of the anilox roll.
For example, a printing press uses a 600LPI, 1.8BCM anilox roll when printing a red plate in a printing unit. When printing in the next printing unit, the red version of the anilox roll is only 500LPI, 3BCM and 700LPI, 1.5BCM. Two kinds are available, then the anilox roller with the closest parameter, ie 700LPI, 1.5BCM anilox roller should be selected.
For new prints, there may be no historical archives. It is best to create a characteristic test record green, including using a standard set of plates and a specific set of ink levels to test the resulting ink density with different anilox rolls. The plate should contain certain real-world areas and various types of positive image and net images. It should also have measurable reading of quantitative ink transfer and dot enlargement, trapping and tonal range, etc., in order to be used as a parameter basis for the selection of anilox roller in adapting to different printings in the future.
In the case of unusual print jobs (new prints, new substrates, new ink systems, etc.), the existing anilox roll list may not be sufficient to provide the necessary parameters. At this time, the printer should consider ordering a set of composite anilox rolls. The so-called composite anilox roll has a variety of different mesh lines (LPI) and cell volume (BCM) ribbon combinations on the same anilox roll, so that you can see many different in one test. the result of. As for the width and quantity, depending on the design requirements, there is a so-called "standard" composite anilox roll supply, but more is customized according to the user's own requirements. In order to ensure the success and effectiveness of the test, the following points should be noted:
Test strips with different parameters should be kept at a sufficient distance to avoid overlapping or interference, and to make clear conclusions.
The width of each test strip should be sufficient to reflect the print effect to be observed.
The first and last test strips (ie, the ends) of the drum should be identical to see if the pressure across the test drum is uniform.
2. Classification management of stock anilox rolls
The inventory of anilox rolls in the printing plant grows with the development of the business. In order to effectively select the most suitable anilox rolls according to the requirements of different printings, it is necessary to list the stocking rolls.
If this list is only classified by LPI, only the number of lines of the anilox roll can be known, and the volume of the cell (BCM) cannot be known. The necessary parameters cannot be provided when selected. For example, the 800LPI anilox roller may be 1.0BCM, while others may be 1.8 or larger BCM. The amount of ink transferred by the printing is very different, so the inventory of the stock anilox roller is marked. In addition to the LPI of the anilox roll, the BCM parameters must also be recorded separately. In addition, due to the long period of use of the anilox roller and the maintenance, the surface of the anilox roll or the wall of the mesh or the blockage of the ink residue is also different, and the printing effect is also greatly different. Therefore, when preparing the inventory of anilox rolls, it should also be noted.
When ordering an anilox roll from a manufacturer, the user should clearly specify the processing parameters, including: number of lines per inch, cell volume, engraving angle, and unengraved sideband width (if extracted). In addition, since there is always a certain difference in the processing, the processing of the anilox roller is preferably ordered in batches even if the same LPI and BCM are processed.
3. Maintenance of the anilox roller
The correct maintenance of the anilox roller should be based on the confirmation of the current use of the anilox roller, including the state of the components on the press, such as gears, bearings, doctor blade systems, etc. This confirmation process can be combined with the daily maintenance of the machine. Or the process of troubleshooting is done at the same time. Carefully use some magnifying glasses to carefully observe the surface of the drum and the condition of the cells, as well as the relevant machine parts, and record them in words, for example:
Bearing wear and looseness of the anilox roll assembly result in uneven embossing in the direction of the roll, wear or damage to the teeth, inaccurate overprinting, repeated regular stripes on the roll, and damaged surface of the anilox roll. The cell volume of the relevant part changes, affecting the uniformity of the ink color of the printing sheet, and the operation of cleaning the anilox roller is inappropriate, insufficient or damages the anilox roller, affecting the ink color, streaking or ink leakage marks or stains.
If such defects are discovered during the printing preparation time, it will inevitably delay production and increase losses. Regular inspections and maintenance should be performed during routine equipment maintenance work.