An offset printing press is a type of flat printing press. Before starting the machine, it is necessary to check the equipment, especially if it has not been used for a long time or if it belongs to someone else. The main areas to check are the joint between the cylinders and their gaps. Any debris should be promptly removed.
The ink fountain and ink rollers are also important areas to inspect. When replacing the ink, the ink box and all ink sticks must be cleaned with wash water.
Firstly, check if there is any debris in between the cylinders, and secondly, whether the ink rollers and ink knives are too tight. When the metal offset printing machine is running idle, the ink fountain should be opened. In addition, important components should also be checked for looseness.
Don't forget to check the oil level, especially on devices without oil pressure detection. Dangerous items on the feeding plate, ink route, cover of the receiving part, or foot pedal should be removed promptly.
Prior to starting the offset printing press, it is necessary to sound the bell to ensure that people around the machine are prepared in advance. If there are a lot of people, the ringing time should be longer, and it is necessary to observe the surroundings to ensure that there are no problems.
Prior to pressing the start button, one hand should be placed on the emergency stop lock switch. If there is an abnormality, the machine should be immediately stopped. Usually, when mounting the plate, rubber blanket or cleaning the drum surface, the machine should be idled first to ensure that there is enough lubricating oil on the surface of the bearings, gears, cams, chains, etc.
The problem of bubbles during offset printing is a common technological failure. The main reason for the bubble is that the peeling force between the ink on the rubber blanket and the metal plate is greater than the bonding force within the metal plate. The following are the common causes of bubbling during offset printing press.
The coating strength of the metal plate is poor, and the water content is too high.
The pressure of the offset printing press is too high, the speed is too fast, and there are too many colors in the sequence.
The ink viscosity is too high, the particles of gold and silver ink are coarse, the ink layer is thick for dark ink, the damping solution adjustment is not appropriate, the water and ink balance is not good, the plate is too sticky.
The offset printing press has been shut down for too long, and the ink has dried out.
The rubber blanket is aging and sticky.
The drying power of the offset printing press is too high.
Unusual printing conditions such as unwashed rubber blanket, recent washing or mounting of plates, excessive embossing temperature, or excessive pressure for gumming/folding.
The environment is too humid, and the metal plate absorbs water.