3. Printing equipment
It mainly includes strict control of printing pressure, printing tension, printing speed, drying temperature and other process conditions.
(1) Grasp the printing pressure. The printing pressure is too large, the ink is easy to spread, the bar lines of the bar code are easy to become rough, and even the stencil is crushed; the printing pressure is too small, the ink transfer amount is insufficient, and the bar code strips are easily thinned or narrowed or even defective. Therefore, appropriate printing pressure should be set according to different printing methods, ink properties, and ink absorbing properties of the substrate materials.
(2) tension control. The tension should be adjusted according to the type of substrate material and its stretching rate. For example, plastic films such as PE and CPP, which have high elasticity rate, should have a small tension value to prevent deformation of the bar code due to film stretching; for paper or PET, OPP For a plastic film with a small stretch rate, the tension can be appropriately large. In addition, the winding tension should not be too large to prevent the barcode from being deformed or the backside from being dirty.
(3) The printing speed should be matched with the drying speed of the ink and the viscosity of the ink.
(4) The temperature of the drying oven cannot be too high, otherwise it will easily cause shrinkage and deformation of the substrate material (especially the PE film), thus affecting the reading of the bar code. Therefore, when setting the temperature of the drying oven, factors such as the printing speed, the printing tension, the type of substrate material, and the size of the printing pattern must be taken into consideration.
4. Environmental temperature and humidity area
The change of temperature and humidity in the printing shop has a certain influence on the properties of the substrate materials (especially paper) and the ink. The temperature and humidity of the environment has the greatest influence on the performance of the ink, which is the drying speed. In general, the higher the temperature, the faster the drying. In addition, the temperature and humidity will also affect the moisture content and printability of the paper. Therefore, in order to ensure the consistency of the bar code printing, the printing shop should try to maintain a constant temperature and humidity to reduce the incidence of printing failures. Generally, the temperature in the printing shop should generally be controlled between 20°C and 28°C, and the relative humidity should be controlled between 55% and 60%.
Sixth, some problems that should pay attention to in the composite processing
It should be noted that the post-printing process will also have a certain impact on the bar code on printed matter and printed matter, such as die-cutting, lamination, lamination, or bagging. In particular, the color of the surface of printed matter after the composite processing will be Certain changes will likely affect the reading of barcodes. The following mainly talk about the impact of composite processing on the bar code and preventive measures.
First of all, to properly select the appropriate adhesive, the type of adhesive must match the type of composite substrate, and also consider the end use of the composite packaging, such as composite aluminum foil, use aluminum foil adhesive; when cooking food packaging bags composite Use high-temperature cooking type adhesives. The color of the adhesive should be as colorless or light as possible, otherwise it will also affect the print contrast of the bar code. In addition, it is required that the adhesive itself has good adhesive fastness and high peel strength, otherwise it will affect the composite strength and composite quality of the package.
Secondly, in the compounding process, attention should also be paid to the tension control of the substrate. Generally speaking, the first substrate is mostly low-extensive BOPP, PETP, or OPA, and most of the second substrate is highly extensible and heated. Deformable LDPE, CPP and other materials. If the tension of the two substrates is not coordinated, especially if the second substrate has a too high tension, the film will be stretched, and after the compounding, it will easily cause contraction and curling. In severe cases, it will cause wrinkles, “tunneling†and other phenomena, resulting in Bar code distortion.
Third, it is necessary to strictly control the compounding temperature and the drying temperature, which cannot be too high, otherwise the film material will produce tensile deformation, which affects the accuracy and readability of the bar code.
Fourth, when the compounding pressure is moderate, the pressure is too high, the substrate may have a calendered deformation, the pressure is too small, there may be less tight fit, poor composite fastness, and even small bubbles. To control the amount of glue, and to ensure adequate plastic coating, all of these may affect the final quality of the bar code.
Seven, bar code detection
Bar code detection is an effective means to supervise the quality of bar codes. The bar code detector is a quality control tool that can not only read the bar code but also measure and evaluate the bar code reading performance in all aspects. After reading a bar code, the detector compares the quality of the read bar code with a previously set standard and finally determines whether the bar code meets the standard. At present, there are mainly two methods for detecting barcodes:
1. Traditional method. Visually measure the appearance of the bar code, and measure the PCS value of the bar code and the dimensional deviation of the bar space with the detection device. If the bar, empty size deviation is within the specified range, and the PCS value is above the specified value, the bar code is judged as " Pass, otherwise it is judged as "Fail". The disadvantage of this detection method is that it does not fit the bar code reality.
2. American standard detection method. The American Standard Test Method is based on the bar code quality standards established by the American National Standards Institute (ANSI) as a reference to evaluate bar code product quality. The method divides the bar code into A according to the bar code PCS value, ECMIN value (minimum edge contrast), DECODABLE (decoding), SC value (bar empty contrast), DECODABILITY decoding capability, DEFECT (defective) and other parameters. Grades B, C, D, E, and F are five quality grades. Grade A is the best, Grade D is the worst, and Grade F is the unqualified. For the printing industry, the default behavior is to require the barcode to be above grade C. The quality level. With the development of bar code technology, the American standard detection method has been widely used. This method has also been adopted in the bar code detection standards published by the European Committee for Standardization (CEN) and the International Organization for Standardization (ISO). It is only based on specific conditions. It slightly made some changes.
In short, the bar code printing process is more complex and involves many processes such as design, plate making, printing, and post-processing. Therefore, in the production process, we must strictly control the technology and quality of each process, and gradually accumulate experience. Explore better solutions to further improve the bar code printing quality.