Starting from ink quality to avoid knife line failure

In gravure printing, knife lines are one of the most common failures. Cutting line failures often result in poor product quality or even scrapping. Knife line, also known as knife wire, ink mark, etc., refers to the blank part of the layout of the ink is not scraped clean and transferred to the substrate on the formation of ink marks. The knife line can be divided into two types: regular knife line and irregular knife line. There are various forms of knife line failures, and there are many factors that cause knife line failures, including ink, substrate, environment, equipment, and technology. For gravure plastic film printing, knife lines are a common failure that is hard to avoid. Therefore, for the gravure printing of plastics and other flexible packaging, it is necessary to fully understand the cause of the knife line, analyze the actual situation of the failure in the printing operation, and propose and take the measures for the remedy to eliminate the treatment, and strive to prevent knife line failure as much as possible.

The production of the knife line has a great relationship with the quality of the ink. When a good quality ink is printed, there will be fewer failures of the knife line, and the failure phenomenon will be relatively slight. The ink with poor quality will also be prone to knife line failure, and the failure phenomenon will be much more serious. The viscosity of the ink, the surfactant, the fineness of the ink, the drying speed, etc., may all result in the generation of knife lines.

Viscosity of ink

The production of the knife line has a direct relationship with the viscosity of the ink. In general, the higher the viscosity of the ink in printing production, the more likely the knife line failure occurs during printing. Therefore, proper reduction of the viscosity of the printing ink facilitates the scraping of the printing ink by the doctor blade, thereby preventing the knife line.

The knife line failure caused by the high viscosity of the ink is mainly presented in two types on the printed matter. One is that the knife line is in the form of a fine flowing wire, and generally it will not be dragged too long but intermittently appears on the printed product. The starting point of the microfluidic knife line is mostly close to the printed pattern, and the starting point of the knife line is generally more thick than the end. If it is not observed in actual production, this micro group of streamlined knife line can be easily ignore. However, this streamlined knife line is often the root cause of quality accidents and must therefore be taken seriously. There are many ways to solve this kind of streamlined knife line failure, but it is also necessary to choose the best processing method according to the actual situation. The specific methods of prevention and control are as follows: (1) Pick a light at the knife line. In general, this tiny streamlined knife line will be improved. This kind of operation is generally completed in the operation of the machine, which requires that it must be completed by skilled operators, so as to avoid unnecessary losses. 2 Because the knife line is related to the viscosity and fluidity of the ink, the basic method of eliminating the knife line is to add a suitable amount of solvent to the ink in order to reduce the viscosity of the ink, increase the flow of the ink, decrease the viscosity of the ink and the flow of the ink. After the increase, the tiny streamlined knife lines are generally eliminated.

Another type of knife line caused by the high viscosity of the ink is the starting point of the printed pattern, but the knife lines are concentrated, relatively rough, and appear regularly in the same position of the print, often continuing to the next color. The knife line is easy to find. The reason for this is that due to the high viscosity of the ink, poor transfer of the printing plate's Internet point, and the destruction of the ink's internal additives due to changes in the ambient temperature, especially when the temperature is too high, a thin layer of dry solids forms on the surface of the ink. , Long time the ink layer accumulated between the plate and the squeegee lifts the squeegee upwards to produce such a line. The solution to such a knife line is: 1 Adjust the squeegee angle. Under normal circumstances, the angle between the squeegee and the plate is 60 degrees, but sometimes the angle between the blade and the plate can be increased to 65 degrees. Left and right, the pressure of the squeegee blade will increase accordingly, and the effect of scraping will increase accordingly. However, it should be noted that the angle of the squeegee should not be increased too much. At the same time, the pressure of the squeegee should not be too high, otherwise it will easily cause damage to the plate cylinder and affect the service life. 2 Add an appropriate amount of additive or solvent to the high viscosity ink to reduce the viscosity of the ink and increase the fluidity of the ink. When adding the solvent, the ink should be stirred with the direction of the solvent. 3 Add a stirring roller to the ink tank. As the plate cylinder rotates, the stirring roller rotates accordingly to prevent the ink surface from being crusted. This is also a way to prevent the knife line from being produced. With the rapid development of printing presses, the medium and high speed machines have now been equipped with a recirculating ink refilling device. This is also a method for reducing the skin surface crust, which has a great effect on reducing the probability of the knife line. All the above solutions can be used in conjunction with each other. Under normal circumstances, through the above-mentioned solutions, the concentration and thickness of the knife lines will be completely or largely contained.

Surfactant

. In the production process of ink, a certain amount of surfactant is generally added; after the plate cylinder is chrome-plated, it has certain adsorption due to the porosity of the metal, if the surfactant in the ink is too much or the plate cylinder has too much adsorption High, in the printing process, the active material will be more firmly adhered to the plate cylinder, making it difficult to completely scrape the blade, which will form a knife line in the printing. This knife line mainly presents meteors or microfilaments. After the knife line appears, wipe the plate and scraper in time, the knife line will disappear temporarily, but due to the problem of the surfactant in the ink, the knife line will appear again quickly, although there is a certain rule but it is not completely repeated. In this case, you can first clean the plate cylinder, remove the active material that has adhered to the plate cylinder, and then add a special surface active agent in the ink, which will achieve more obvious results. If you add a slowing agent before printing, you can play a preventive role.

Ink fineness

The occurrence of knife line failure is closely related to the thickness of ink particles. In general, the finer the ink, the better the quality of the printed matter and the corresponding reduction in the probability of a cut. At the same time, the finer the ink particles, the better the hiding power. However, it is not that the smaller the fineness of the ink, the better, and the fineness of the ink can also cause other printing problems. In gravure or other printing, there are strict requirements on the grain size of the ink. Generally, the thickness of the ink particle is required to be moderate. Generally, the ink fineness is about 15 μm. Foreign matter mixed in the ink, or additives in the ink precipitated with temperature changes, the aggregation of the pigment, etc., can produce coarse particles of foreign matter, making the ink particles rough. Most of the foreign matter is carried by the film. Due to the static electricity of the plastic film substrate, the adsorbed dust and the additives in the plastic film precipitate out into the ink. These are the main reasons for the appearance of foreign matter. When using high-hardness pigments, knife lines may be generated even after grinding: red and blue inks are easier to cut, because red and blue pigments are hardest to grind, and it is difficult to ensure that they have a suitable grain size. In addition, knife lines also appear when using hydrophilic pigments. The fineness of the ink does not meet the requirements. The coarse particles will lift the blade and create a knife line. In addition, the rough ink particles have a great damage effect on the doctor blade and the printing plate. Through careful observation of the failure of the cutting line caused by the unsatisfactory ink fineness, it is found that the ink line is not suitable for the cutting line caused by the fineness of the ink grain. The directions are not the same. The main manifestations are three forms: (1) The knife lines appearing on the prints are irregular and vary in thickness. Such a knife line extends from the printed pattern portion to the unpatterned portion, the knife line is long, and along with the left and right swing of the squeegee, the knife line also moves, sometimes one, two, sometimes even many. For the elimination of this knife line, the position of the squeegee can be adjusted up and down properly. When adjusting the test printing, attention should be paid to observe the phenomenon of shades of five colors in the printed matter, and it is necessary to ensure that the printing color is normal. Because the squeegee is easily adjusted up and down, the color difference phenomenon of the printed matter can easily occur, especially when the printing plate surface is shallow, which must be noticed. 2 The direction of the knife line on the print is very regular. This cutting line appears on the printed pattern portion on the same plate, and is in the same position. With the squeegee's left and right swing, there is basically no major change, because the coarse particles in the ink lift up the scraper, and the left and right swing of the scraper cannot drive it. If it appears in the middle color, the next color ink will These knife lines are filled, ie the next color of ink hue appears at the knife line. 3 Printed cuts appeared on the last color. When printing on plastic film, it usually appears on the white plate. Such one, two or more cutting lines will run through the entire print. If viewed from the front of the print, the knife line is not rough, and it is not easy to find it. From the back of the print, one can see that the trajectory of the knife line always runs through, forming one, two or more long marks. There is no doubt when compounding, especially in the composite aluminized film, it will be more clearly seen in a large area of ​​white. At the same time, the third kind of knife line occurs mostly in the white version, because the white ink contains titanium dioxide, and the thickness of titanium dioxide is very important. In addition, in the development of ink, grinding is not in place is the root cause of this failure phenomenon. For the knife line caused by ink fineness, no matter which type of knife line, the solution is to stop printing, filter the ink, filter the used ink and then print it on the machine, which has a good effect on preventing the knife line. Filters are different because of different manufacturers. Some manufacturers even use silk stockings to filter and receive certain results. According to the practical experience of some manufacturers, the use of a 140 mesh metal screen is ideal.

Ink drying speed

The ink drying speed is too fast, so that the ink is dried excessively, the friction force between the plate cylinder and the blade is relatively increased, and the blade is difficult to scrape the ink of the plate surface. When the drying is too slow, the trace amount of ink attached to the non-graphic portion of the platen roller will be transferred to the substrate to form the platen, resulting in the occurrence of knife lines during printing. Therefore, pay attention to debugging control the drying speed of the ink.

Silicone Wine Glass DISHWASHER SAFE & FREEZABLE, the flexible rubber glass has a temperature range of -46°F to 460°F (-40°C to 230°C) so they won't melt or crack like other plastic cups


SILICONE WINE GLASS LIGHTWEIGHT TRAVELING WINE GLASS is easily collapsible for on-the-go drinking


SILICONE WINE GLASS BPA FREE FOOD-GRADE SILICONE means the eco-friendly wine cup is stain-resistant


SILICONE WINE GLASS PERFECT FOR camping, beach, tailgating, boating, pool parties, and barbecues


SILICOEN WINE GLASS SQUISHY TUMBLER easily holds red and white wine, beer, soda, water or your favorite cocktail


SILICONE WINE GLASS Details:


Material: FDA standard silicone

Color: any pantone color

Size: XL:84.5 X 103mm L:76X92.5mm M:67X82mm

Volume:XL:11.2ounces 8.5ounces 7ounces



Silicone Wine Glass

Silicone Wine Glass,Wholesale Wine Glasses,Customized Wine Glasses,Novelty Wine Glasses

Shenzhen Feiaoda Technology Co.,Ltd , http://www.flysilicone.com