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Flexo printing sleeve is hollow, and the mandrel has been fixed on the printing machine. The mandrel using the sleeve is different from the general version of the roller (although they are all metal, it looks quite similar), the mandrel used by the sleeve must have an inflation function, so it is called an air shaft (also known as an air support shaft, Inflatable core, air cylinder or air mandrel). There will be several vent holes on the air shaft, and compressed air will come out of these holes.
flexo printing sleeve is composed of a multi-layer structure. Decomposed further into:
1. Sleeve core 2. Cushion material 3. Foam material 4. Polyurethane surface coating
This is the basis of sleeve molding, generally fiberglass material with fibers. The inner diameter of the sleeve core should be consistent with the outer diameter of the air shaft. When the air shaft is not inflated, the mounting sleeve should not be installed on the air shaft.
When loading and unloading the sleeve, the air shaft is first inflated. Compressed air will rush out of the small hole on the air shaft, which will slightly expand the sleeve core (only a few wires) and can push the sleeve into place. The sleeve core must have a certain ductility, otherwise there is no way to open it. After installation, the compressed air will be closed. If the sleeve core can be restored immediately, it will be tightly attached to the air shaft. Therefore, the sleeve core should also have good resilience, otherwise, after frequent expansion and contraction, once the resilience is lost, the sleeve cannot be fixed on the air shaft. The sleeve will rotate at high speed on the air shaft without slipping, so the sleeve core must also have sufficient fit.
It is generally an elastic pad with compression-recovery properties. The cushioning material plays two roles. One is that when the compressed air expands the inner core, the cushioning material provides the sleeve core support. The other is when printing, the printing plate will be under pressure, and this pressure will also be transmitted to flexo printing sleeve. At this time, the pad can provide a certain cushioning capacity of the sleeve
As the main structure of the sleeve, the foam material plays a role of filling. The characteristic of the foam material is that it has a certain rigidity but a low density, so it is light in weight. This will not make the sleeve too heavy. We must find a balance between rigidity and weight (generally, the higher the density, the better the rigidity, but the weight will be heavier, and the cost is relatively high), otherwise the sleeve is either too heavy or easily deformed.
Generally, it is polyurethane, which covers the foam layer to stabilize the outer diameter, prevent scratches, and reduce residual glue. Generally, the surface coating line will be used as a reference for placement. The material of the surface coating is very important. It is necessary to avoid deformation of the sleeve, the surface grinding effect is good (no pits, knife marks), and it is also scratch-resistant (because the tape is often cut with a blade). To make the tape stick (otherwise it will be warped) is not too strong (otherwise it is easy to leave residual glue when tearing the tape).
In simple terms, a repeating perimeter requires a set of sleeves (a few color groups are a few). The calculation of the outer diameter of flexo printing sleeve is very simple:
Repeating circumference = (Sleeve outer diameter + Plate thickness X 2 + Tape thickness X 2) X Circumference
Therefore, pay special attention to that the thickness of the printing plate and tape cannot be changed arbitrarily, otherwise the original sleeve setting will be destroyed.
The outer diameter of the sleeve can be arbitrarily customized according to the needs of the repeated circumference, and there is generally no limit. However, the larger the repetition circumference, the larger the outer diameter of the sleeve, that is, the greater the wall thickness of the sleeve (ie (outer diameter of sleeve-outer diameter of air shaft) / 2), the heavier the weight. The sleeves of some wide-width machines with large circumference can weigh tens or even hundreds of kilograms, which is obviously not suitable. At this time, you need the assistance of the "crossing sleeve"
A repeating perimeter requires a "set" of sleeves. For example, an eight-color machine requires eight, which is not the most correct concept. JCTPRINT recommends that it should be configured according to the actual situation. Some repetitive perimeters may be used frequently. If there is only one set, it must be unloaded and re-applied before printing again, which is obviously a waste of time. Some manufacturers will prepare two or more sets of sleeves of the same size, which can also be used as a backup for accidental damage. Some orders have special specifications, little repeatability, and simple colors, so there is no need to order sleeves of the same color set.
Generally, a pressure of 6 to 8 Pa is required, but this refers to the pressure measured on the air shaft. Many cases of unsmooth sleeve loading and unloading are related to insufficient compressed air pressure. Even if the pressure of the air compressor reaches the standard, it may be that the pressure at the end of the air shaft is simply insufficient due to too long pipes or too many shared pipes. In addition, the flow rate of compressed air is also very important. The amount of gas used when the sleeve is loaded and unloaded is large. If the flow rate of the compressed air supply is insufficient, the pressure will soon drop, and natural loading and unloading will also have problems.
The sleeve should be kept clean at all times. The dirt on the surface of the sleeve will affect the mounting plate. The dirt on the inner wall of the sleeve will affect the loading and unloading. The dirt on the side of the sleeve may fall into the inner wall, surface, substrate or ink. . The cleaning of the sleeve should avoid the use of solvents that are too corrosive, which will greatly damage the polyurethane layer. If it penetrates into the inner wall, it may cause erosion and lead to delamination, and the sleeve must be scrapped.
The sleeve should be stored upright at ordinary times, do not lie flat on the ground, and do not stack, otherwise the sleeve is easily deformed. High temperature, high humidity, and solvents are all detrimental to the life of the sleeve, and these harmful conditions should be excluded as much as possible.
JCTPRINT also recommends that you choose our flexo plate roller instead of the plate sleeve, on the one hand can guarantee your printing effect, on the other hand, save your cost.
