In offset printing, the paper reel is unwound at a very high speed, and the paper web is transferred from the paper reel through the printing unit to the folder. Steel rollers are installed along the web of the rope, which stabilize the web by stretching it to give it some tension. For a paper web to pass through its path at high speed and be correctly printed, it must be dense, but it must not break. In most modern offset offset machines, photocell sensors are installed along the web path to ensure network continuity throughout the printing process. These sensors provide a constant feedback signal to control the machine. When the signal is interrupted, the machine stops to avoid rolling paper in the rollers and rotating cylinders, which may damage the machine.
During printing, there are cases when the web breaks. This disables the printing process because the machine stops. The remains of the machines lead to high waste and low efficiency and productivity. Each time you start, the original prints must be canceled before getting a quality print. Ultimately, the quality will depend on speed fluctuations due to stops and starts. To increase efficiency, minimize waste, improve quality and increase productivity, shutdowns should be minimized to the maximum. Web breaks are one of the main causes of stop lists in offset printing on the Internet. The following are the 5 main causes of breaks in web offset printing;
Coil Defects
Some paper drums have manufacturing defects, such as due to roundness, poor winding, bad joints, foreign objects, gluing inside or on the sides of the drum, due to a weakened coil rod. In most cases, such defects will lead to pauses during operation. The drum may also be damaged due to poor handling, storage, or transportation. Poor storage can also affect the condition of the coil, either making it too dry or too wet, which affects its performance on the press. Poor quality paper will also break when stressed. Therefore, coil defects and paper quality are the main causes of interruptions in web offset printing.
Fork error
Another important reason for a break in web offset printing is a malfunction on the drum rack. The coil stand is designed to apply only the correct voltage on the coil, as required by the spokesperson. Using pneumatic and electronic controls, the tension rollers tighten the tension on the drum and in the canvas to pull it out of the drum rack into the print unit and into the folder. An error in electronic or pneumatic control or when calibrating the tension rollers will result in too much tension or low voltage. This will pause and the car will stop. Due to a fault, the drum rack may not move from one coil to another, which automatically leads to a break in the network. Thus, the state of the coil rack can cause interruptions in web offset printing.
Poor tension control
During the printing operation, the pressman adjusts the web tension settings according to the printing and paper conditions. Depending on his judgment, he may further increase or decrease the tension of the paper on the main control console. On this console, the pressman can manipulate the tension of the paper on the drum rack, after the printing device or in a folder on the center screen with the touch of a button. If it increases or decreases the voltage too much, the network will break and the machine will stop. Poor tension control is another important cause of a break in web offset printing.
Bad ink and water balance
Lithographic offset printing of relations on the principle that water and oil do not mix. Simply put, inks, which are an oily and moisturizing solution that is based on water, are applied to the surface of the printing form. The image areas of the plate are oleophilic and will attract oil ink and repel moisturizing solution, while areas without an image plate are hydrophilic and will attract moisturizing solution and repel oil ink. The balance between the moisturizing solution and the inks used is crucial for obtaining quality printing. If too much water is applied, excess water will be absorbed by the paper. Water-soaked paper breaks easily under tension. Excessive use of water during printing occurs before the main cause of a fracture in web offset printing.
Bad splicing pattern
Paper drums come in different sizes. Sizes and sizes vary depending on the paper mills. Different manufacturers produce paper reels depending on customer and market requirements. Depending on the number of copies to be released, multiple drums may be required. When one coil is consumed, the coil stand will automatically switch to the new drum to avoid stopping the press. In order for this change to occur smoothly and at high speed, it is necessary to create splicing. The net from the expiring drum will be inserted into the new spool, which will then continue to unwind and be loaded into the printing unit for production. In order for this switching and insertion to be successful, the template layout must be correct. The rubber and splice indicator should be in the correct position. A poorly made picture will end in a pause, because the insert will not be accurate or strong to withstand the tension on the paper. Here bad splitting patterns are the main causes of interruptions in web offset printing.
