Ink Viscosity Control System Application for CI Flexo Press
Viscosity control in central impression (CI) press is very important, Ink viscosity affects how well your ink is able to transfer over from the anilox to the plate, and from the plate onto the printing substrate. It affects how well your ink will dry on the substrate. In general, your press production speed, and the quality of your print is highly correlated to the ink viscosity. In Flexographic, having a suitable ink viscosity makes all the difference.
To control the ink viscosity methods are: Vibrational Viscometer, Falling Sphere Viscometer & Zhan cup.
Zhan cup is a cup-type viscosimeter that measures the viscosity of the ink by flowing a definite volume of ink through the cup. The time (seconds) required for the ink to flow through the cup defines the viscosity of the ink. The advantage of using a Zhan cup is that it is simple to use and requires no special skills. Zhan cup is convenient as it is small and lightweight, at the same time measurements could be done quickly. However, the disadvantage of the Zhan cup is its accuracy, even for an experienced operator. Zhan cup is used together with a stopwatch. The timing of starting and stopping the stopwatch can vary from operator to operator and from trial to trial. The measurement can easily differ by 2~3 seconds. Furthermore, during the printing operation, due to factors like temperature and humidity, the viscosity of the ink is likely to alter. This means that the operator will need to constantly re-measure the viscosity of the ink throughout the operation. At the same time, constantly readjusting the ink to achieve a constant viscosity.
Falling Sphere Viscometer drops a sphere with known density and dimension into the fluid sample and measures the time it takes for the sphere to fall to a specific point. Falling Sphere, like the Zhan cup are both flow-based system. Often the Falling Sphere methodologies are equipped with sensors to capture data digitally. When compared to the Zhan cup, the measurements from the Falling Sphere are much more accurate. However, the Falling Sphere does not provide a continuous measurement of the ink viscosity. The readings are done in segments. Therefore, depending on your accuracy requirement Falling Sphere may or may not be suitable for your process.
Vibrational Viscometer measures the damping of an oscillating electromechanical resonator immersed in the sample fluid. This technique is often used in the process to give continuous readings. Digital data are recorded continuously through sensors. Vibration Viscometer is the most accurate real-time measurement instrument of the 3 mentioned.
To get an accurate and continuous reading of the ink viscosity is only the first step. The purpose of an accurate and continuous reading is so that you can adjust to it in real-time. Many printing and converters are adopting the automatic ink viscosity control function to their operation. To automatically measure the ink viscosity in real-time, and most important of all, to make adjustments in real-time to maintain a stable viscosity throughout the printing operation.
The amount of labor, time and waste could be saved with the automatic ink viscosity control.
As the professional manufacture of central impression (C.I.) flexo press, we suggest customers to use an automatic ink viscosity control system to save time, save the cost of ink waste, and achieve the high-quality printing effect.
