Misunderstanding of flexographic plate making of t

2022-08-15
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One of the misunderstandings of corrugated box flexographic plate making:

the selection of plate materials is blind

many plate making enterprises do not consider the actual situation of the printing plant, such as loading and unloading weights, removing the upper cover, unplugging and plugging cables, opening the side door to check the model of the printing machine, the thickness of the plate pasting tape, the type of ink used, etc., blindly follow the crowd. Taking the printing plate used for corrugated box as an example, many customers only know the famous TDR plate of DuPont

tdr is a widely used corrugated printing plate with excellent plate making performance, but its resolution is not as high as that of a batch of thin plates such as EXL/UXL. When printing E-type corrugated and images up to 120 lines/inch, thin plates such as EXL/UXL should be used instead, and sponge pads should be added, so as to obtain high resolution. At the same time, with the increase of the hardness of the plate, it can also reduce the dot expansion, so that the printing products can achieve excellent results

Myth 2:

the pre press system configuration is unreasonable

because the special software for flexo printing is relatively expensive, which is not affordable for ordinary small and medium-sized plate making companies, at present, only a few overseas companies in China can afford it, while the vast majority of plate making manufacturers have carried out localization according to local conditions. Generally speaking, most small-scale plate makers use platform scanners and digital cameras as input devices, and modify the PC or apple G3 used by computers, plus phototypesetters and film processors as output devices

due to the limitation of the size of the plate, many domestic manufacturers copy the configuration of offset plate making, and even adopt lagging technologies such as print output and photography, so that the domestic corrugated box flexographic printing technology has been in a low-level state according to the development status of the actual friction and wear testing machine. It is only used as a substitute for the hand carved rubber plate, and has not yet entered the era of color corrugated box printing. Compared with its foreign counterparts, We are nearly 10-15 years behind

myth 3:

using offset film as the final output film

it is true that offset film has a series of advantages, such as convenient procurement, economy, timely supply and so on, and the process conditions are relatively mature. However, offset film has a fatal weakness: the surface is too smooth

the photosensitive resin flexographic plate will release a certain amount of oxygen during the photopolymerization reaction (the physical and chemical mechanism belongs to the scope of the patent, and will not be disclosed). Only the frosted film can smoothly guide these oxygen out, so that the film and the plate still maintain equal contact, and accurately transfer the image. On the contrary, the surface of offset film is bright and clean, and oxygen cannot be exported smoothly, resulting in a larger gap between film and plate, resulting in image deformation, text thickening, blurring and other faults. Some plate making operators use talcum powder to alleviate these problems to a certain extent, but at the same time, it also leads to a decrease in light transmittance and an increase in the cloudiness of the negative

myth 4:

there are defects in the design of plate making machine

some domestic plate making machine manufacturers, in order to compete for price, make rough products at low prices. Their typical practice is to copy the circuit design of fluorescent lamps and use low-cost domestic ordinary UV lamps. Since the circuit of the fluorescent lamp is directly started by the starter, the flicker generated after the lamp is started is bound to cause uneven back exposure of plates with high back exposure requirements and short back exposure time, such as EXL/TDR, resulting in uneven photosensitivity of the base material. This custom report: click the "custom report" button, and the sample plate will get a base with wavy surface after washing

the correct way is to choose high-quality UV light sources, such as pH ilips' VA R series lamps equipped with high-quality ballasts and starters, and add a filament voltage of about 5 volts at both ends of the filament (very important). In this way, the filament can be kept in a red hot state. When exposed, just turn on the power supply of the main circuit, and the lamp can be started in an instant to achieve a uniform exposure

the radiation energy of pH ilips lamp tube with this connection method can reach more than 160mw/cm2, while that of ordinary lamp tube is only 40mW/cm2, and the radiation energy difference is 4 times, which means that under the same exposure, the efficiency difference is 4 times

myth 5:

misunderstanding exposure tolerance

according to the internationally recognized standards of FTA, the exposure tolerance is specified as follows:

tolerance = deadline formation time

1. For corrugated box printing plate (more than 2.84mm), it refers to the exposure time formed from 3% point on 34L/cm printing plate to the time when the depth of 0.8mm wide negative line is reduced to 0.1mm

2. For thin plates (less than 2.84mm), it refers to the exposure time from the 2% point on the 48l/cm printing plate to the time when the depth of the 0.8mm wide negative line decreases to 0.1mm deep

the greater the tolerance, the less sensitive it is to the change of exposure time. Before the dot formation, the negative line of some inferior plates has been filled, and the exposure tolerance is negative, that is, the dot and negative line effects cannot be exposed on the same printing plate at the same time

some plate makers excessively require the depth of the plate relief, making the base too thin, so that the main exposure time is too long and the depth of the negative line is lost

myth 6:

don't pay attention to keeping the plate making solvent fresh

every time you wash the plate, you should add an appropriate amount of fresh plate washing solvent to keep the photosensitive resin in the solvent not too much

never add the old solvent that has not been distilled as fresh solvent to the pipeline of fresh solvent. Otherwise, it seems to save costs, but considering the downtime and paper waste caused by printing plate problems and accelerating the damage of plate making machine, it is not worth the loss. There was once an example of a plate making machine worth more than 100000 US dollars. Due to the long-term lack of fresh solvent supply, many faults such as brush caking, spray blocking, poor internal circulation of the machine and so on, almost caused the plate making machine to be scrapped. It had to be repaired by the French engineer of the original factory, so as to avoid more losses

ensuring a certain amount of fresh solvent supply can not only reduce the stickiness and swelling of plates, but also improve the speed of plate washing, which is also conducive to extending the service life of plate washing machine and improving the quality of plate washing

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