In order to obtain consistent high quality and reduce waste of printed products, it is a good idea to control the ink color density, which often does not attract people's attention. Most people today rejoice on old, traditional methods of control—often measuring the viscosity of the ink (by means of the well-known flow cup measurement). In fact, ink viscosity measurement is not a standard and there are still problems. Whether it is solvent inks or water-based inks, coating oils or paints are affected by many variables that make the viscosity measurement inconsistent. The use of flow cups to measure viscosity, variable factors affecting viscosity control are: temperature changes, changes in flow measurement techniques and sensitivities, changes in flow cup conditions, changes in operator, changes in the amount of new solvent or diluent, and In the production process, new inks with different temperatures and different viscosities are added. Although there are many types of flow cups on the market, some are better or more accurate, but because of the many variables mentioned above, it is difficult to obtain satisfactory results if the ink viscosity is continuously measured on a printer using a flow cup. Viscosity vs. Ink Influencing the viscosity is an internal resistance to the liquid flow.We try to achieve the consistency and balance of the color in the printing process by measuring the viscosity of the ink.If the ink viscosity changes, it will affect the following aspects: 1, the ink drying time 2, Color intensity and consistency; 3. Keeping and coverage of the print mark; 4. Transferability of ink; 5. Consumption of ink and solvent; 6. Waste of material; 7. Production speed When the ink flows through the pumping system In fact, in addition to being limited by the additives and fluidity of the ink, the viscosity of the ink is also affected by the drying device, the ink pump, the friction of the ink roller, the temperature and evaporation inside the building, etc. But the main The effect often comes from the temperature change.The ideal viscosity of the ink varies depending on the type of print and the type of press, but there must be one A constant ink density is required to maintain a uniform color density in order to reduce waste and improve yield. Please note that maintaining the same viscosity at different temperatures will cause a change in color density. This practice is extremely inappropriate! Factors that affect viscosity If the human factor is also taken into account in the measurement, then the possibility of error is increased.For example, if the viscosity is measured in the Zahn cup No. 2 within three shifts, the error is ±2 seconds, which is equivalent to a 20-second measurement. There was a change of ±10%, which directly led to the production of unacceptable prints.In the late 1970s, Dr. K Schlacpfer mentioned in his UGRA report that a temperature fluctuation of 1 degree Celsius is approximately equal to 3% viscosity change. Means that when the boot temperature is 70 degrees Fahrenheit, after about three quarters of an hour, the temperature will rise to 79-90 degrees Fahrenheit, 9-10 degrees increase in temperature, it will make the solvent ink viscosity change 15%, water-based ink The change in viscosity is 5-7%, and this change was confirmed by William Chorvat of the Sun Chemical Company at the press workshop workshop of Louisville GTA in 1986. He said that a temperature fluctuation of 10 degrees Fahrenheit caused a 15% stickiness. Change, this change in viscosity will cost you more.At the GRI meeting, Mr. Paul Sternfko of Flint Ink stated in his report “The effect of temperature on the viscosity of inkâ€. “We often forget that viscosity is also very sensitive to changes in liquid temperature, and that the heat generated by the printing machine's friction will also cause the ink temperature to rise significantly. In the above figure, we can see the effect of changes in ink temperature on the viscosity and the color concentration. Therefore, we must use a concentration control device to maintain the ink's color density constantly. Because we have seen that using flow cups or common viscometers to control viscosity without some temperature compensation is incorrect and not feasible. It is not enough to measure viscosity without considering temperature. Therefore, we must rely on and use our technology to achieve precise color concentration control. Color Density Control In order to fully adjust the viscosity, temperature fluctuations must be continuously monitored by a system. This system converts temperature fluctuations into viscosity adjustments. Using a color depth control device to check and adjust the ink concentration while taking into account changes in the temperature of the ink, this ensures that the correct balance of ink components is maintained. The color density control device maintains the color depth constantly at a correct value. However, there are also disputes over temperature control. If you consider all the plumbing and energy losses on each ink reservoir, the cost of this control method is obviously not cheap, and it is not very practical for the packaging and printing industry. At the corrugated board printing exhibition in Paris in June 1994, people also considered viscosity control and color depth control as one of the most important factors related to the production of high-quality prints. Other factors such as:
â— Before printing, use a static web vacuum suction system to clean the web or sheet.
â— In addition to the color concentration control, it is also necessary to control the pH value.
â— Prepare the ink in the ink shop. By effectively using time, labor and materials, you can save money. In flexo printing and gravure printing, the ink color density control device can be effectively used for solvent inks, water-based inks, coating oils, waxes, and the like. Using the ink concentration automatic control device can save a lot of time, labor and materials, because the increase of one second time or temperature change with the flow cup measurement will increase the loss of ink pigments. If the automatic viscosity control device is used together with a temperature compensation or temperature control device, the consumption of ink, solvent and other materials can be reduced while maintaining the stability of the product quality. Which automatic control device to use, we should consider the following factors:
• Monitor the temperature change and adjust the viscosity accordingly. In this way, the actual viscosity control device becomes the color depth control device. The control device can be a combination of ink cooler/heater to maintain the exact same temperature, especially in very hot environments (eg above 95°F);
â— can accurately measure the viscosity;
â— It has nothing to do with the amount of ink on the ink fountain during operation;
â— Use a sealed circuit to prevent solvent evaporation;
â— It can quickly and easily exchange the ink on the printing unit;
â— No ink deposit on the control device;
â— Operational environment safety;
â— Little or no maintenance required;
â— Automatic cleaning of the device itself at the end of printing;
â— Easy to operate, not easy to malfunction;
â— It can be used with pH control device. There are still more advanced systems on the market that are controlled by electronic computers. They not only control the color density of the ink, but also control the pH (for aqueous inks), while also providing ink on the screen or on paper. The subtle changes and the various steps that the system maintains the ink color concentration at an optimal level. Using automatic ink color density control and temperature-compensated viscosity control, consistent print quality can be achieved, ink savings, waste reduction, time savings and improved production. Therefore, in order to achieve the above-mentioned goal, the printing factory should implement the control of the ink color concentration, and the best way is to install a proper automatic ink color concentration control system or a viscosity control device of the ink temperature adjustment system.
Translated from Flexo 1994.2
Anti climb fence is a type of security fence designed to prevent unauthorized access and climbing over the fence. These fences are commonly used in high-security areas such as prisons, military bases, and government facilities.
Anti-climb security fences are designed to prevent unauthorized access to a property or area by making it difficult for intruders to climb over the fence.
Anti-climb security fences are commonly used in high-security areas such as military bases, prisons, and government buildings. They are also used in commercial and residential properties to provide an added layer of security.