Relief Printing Common Printing Failures

In the case of letterpress printing, failures that often occur include: back-scratching, ink penetration, flying ink, and static electricity. These failures affect the quality of the print and must be eliminated by taking appropriate measures.

(A) The back of the dirty

The ink printed on the substrate adheres to the back of another sheet, causing smudging. To prevent back-scratching, a dusting device is generally installed in the delivery department of the printing press to disperse fine-grained calcium carbonate between printed sheets. In addition, accelerating the drying of the ink, reducing the height of the press sheet, and placing a good ink-absorbing paper sheet between the printed sheets, etc., can suppress the dirtying phenomenon.

(b) Printout of ink

Offset of ink refers to the phenomenon that the front side of the printed sheet can be seen on the back side. To prevent the ink from passing through, you can choose a tight paper printing, can also increase the viscosity of the ink, and appropriately reduce the printing pressure.

(III) Flying ink

The tiny droplets of ink, scattered in the air, are called "flying ink", also called fogging, and are the most common failures of high-speed rotary letterpress printers. To slow down the "flying ink" phenomenon, we can increase the humidity in the printing shop and make the device conductive ink such as water-based ink.

(D) Static electricity

In the printing process, the paper is not easy to separate, the paper on the delivery table is uneven, or the paper on the delivery table is skewed and overprinting is not allowed, etc., which may be caused by static electricity. To eliminate static electricity from printing, a static eliminator is generally installed on the printing press to ionize the air in the vicinity of the printing press, thereby neutralizing positive and negative electrostatic charges on the paper. It is also possible to spray an appropriate amount of water mist in the vicinity of the printer or behind the impression cylinder to eliminate static electricity on the paper. In addition, increasing the humidity in the printing shop is conducive to the elimination of static electricity.

(5) Quality requirements for letterpress prints

Product quality means that the product meets certain uses and meets the needs of people. The use of printed matter is various, the variety is different, and the printing methods are different. According to the process and equipment of letterpress printing, the quality of printed matter should meet the following requirements

(1) Size Requirement The tolerance for the fine product open size is 0.5mm, and the general product is 1.0mm.

(2) pressure, ink printing pressure, ink average. Text imprinting, fine products are clear and complete, and general products have no significant lack of strokes.

(3) The average size of the printed pages requires that the average size of the fine products should be greater than 15/16, and that of the general products should be greater than 14/16.

(4) In the set of segment printing pages, the correct and reverse printing of each page is correct. The overprint error fine product is less than 1.5mm, and the general product is less than 2.5mm.

(5) Appearance of fine products, printed pages neat, unblemished version, nails, dirty marks, flawless pen breaks. For general products, the printed pages are neat, with no significant paste, studs, dirty marks, and no significant lack of strokes.