Print Quality Will Be Compromised Without Carefully Using Small Scraper

Pressure

Factors affecting the pressure of the printing press doctor blade include the pressure of the cylinder, the type of blade (hard or soft), and the angle at which the doctor blade intersects with the printing plate. The larger the angle, the greater the pressure. Excessive pressure will reduce the ink transfer rate and cause more wear on the printing plate and the blade. Insufficient pressure, on the other hand, can lead to dirty plates or doctor blade lines.

Sharpness of the Blade

The sharpness of the blade depends on whether it is a new blade, the angle of the blade edge during sharpening, and the model of sandpaper (or oilstone) used. The ideal sharpness of the blade should effectively scrape off the ink without producing blade marks. Overly sharp doctor blades tend to leave blade marks and also wear out the printing plates.

Distance Between Doctor Blade and Printing Plate

Reducing the distance between the printing press doctor blade and the printing plate helps to increase the ink transfer rate but can also lead to dirty plates. Conversely, increasing the distance can effectively prevent dirty plates and some fine line marks but will reduce the ink transfer rate.

Flatness of the Blade

The flatness or warping of the blade mainly depends on the installation method. It may also be related to foreign objects sticking to the blade seat groove, or on the blade or liner. Poor flatness of the blade may cause water droplet marks on the edges of the printing surface or occasional intermittent line marks. Some people think that these phenomena are due to rough ink or poor ink flow, but in reality, an uneven blade can also cause these issues.

Movement of the Doctor Blade

The left-right movement of the printing press doctor blade plays an important role in reducing doctor blade lines, increasing the utilization rate of the blade, and reducing wear on the plate. If the printing press doctor blade does not move properly, measures should be taken to improve it.

When line marks appear during printing, it can damage the plate, and the doctor blade may not be sharp. Another reason could be foreign objects sticking to the back of the blade edge. The solution is to move the doctor blade up and down or front and back to shake off the foreign object. If this does not work, it may be necessary to stop the machine to clean the doctor blade.