Safe Production | Step-by-Step Guide to Checking the Roller and Printing Plate

Roller Inspection

If it is an old plate that has been printed, just check whether the surface of the plate roller is damaged, exposed copper, rust spots, and chrome layer falling off, and promptly notify the plate making factory to take corresponding measures. As for newly made plates, not only should the surface of the plate roller be checked for scratches and bumps, but also the specifications of the plate roller and the graphic design of the plate should be checked to see if they meet production requirements, mainly considering the following aspects.

• Check whether the width and diameter of the plate roller are within the printing range of the existing printing machine. Generally, a plate roller with a diameter of 100-200mm is easier to print. If the diameter of the plate is too large, it is easy to cause dry plates at low speeds and ink throwing at high speeds. If the diameter of the plate is too small, it will reduce printing efficiency.

• Check whether the registration line and cutting line of the plate can meet the post-processing requirements, and also pay attention to whether the color of the pattern can be recognized by the sensor for cutting and bag making.

Plate Inspection

Inspection of Plate Cell Depth and Plate Quality

The depth of the plate cells on the photopolymer plate used in gravure printing is very important for the amount of ink transfer and the reproduction of tone. Before installing the plate roller on the printing machine, a detailed inspection of the plate cell depth must be performed. Plates with substandard cell depths can only be discarded and remade. The inspection of plate cell depth is generally done using a microscope roughness tester. The requirements for cell depth are generally 3-4μm for highlights and 40-50μm for shadows.

After confirming the accuracy of the plate cell depth inspection, the graphic part of the plate should be checked against the proofing sample, and the plate should be inspected for defects and dirt with a magnifying glass. If these defects are found, they can be repaired by engraving or welding; plates that cannot be repaired must be discarded and cannot be used. It is strictly forbidden to use plates with unqualified quality for printing.

Inspection of Plate Roller Diameter

When printing color prints with a multi-color gravure printing machine, the deviation in the diameter of the plate roller is one of the main reasons for inaccurate registration. Therefore, before printing, check the diameter of all plate rollers of the same printing machine and ensure that the diameter of the plate rollers in each unit meets the requirements. In general, the diameter of the plate rollers in each unit should be equal, but sometimes slight adjustments may be necessary. For example, considering that high molecular polymer materials such as plastic film will shrink in size after being heated, the diameter of the plate roller in the rear printing unit should be slightly smaller. Such adjustments, whether increasing or decreasing, are minuscule but can further improve registration accuracy.