Three Major Causes of Producing Bars in Offset Offset Printing

Due to the collision and impact of the plate cylinder and the impression cylinder during the transition from the working surface, the cams, connecting rods and other mechanisms will vibrate under inertia, and the outer circle of the cylinder will no longer be uniformly rolled at constant speed. Therefore, slight slippage occurs between the ink roller and the plate, between the plate cylinder and the blanket cylinder, between the blanket cylinder and the impression cylinder, and the ink and ink balance is damaged, and the ink layer is affected due to the breakdown of the ink layer. The thickness causes the dots to increase or decrease, and a bar appears parallel to the axis of the drum. The higher the speed of operation of the machine, the more serious the phenomenon of bars.

1. Design aspects

The arrangement position of the drum is not reasonable, and the commutation of the tandem roller is not performed when the roller is empty and the wall plate and the drum are deformed due to insufficient strength and rigidity.

2. Accuracy

The assembly accuracy of gears, eccentric sleeves, and rollers is not high, which affects the smoothness of the mechanical movement.

3. Dynamic load

The impact of the dynamic load on the ink bars is that the rotating parts are unbalanced, the reciprocating motion of the mechanism generates vibration, and the cam mechanism accelerates to cause an impact. Associated with the producing factors of the bars are the embossing, uniform ink, wetted parts of the drum, bearings, roller gears, main transmission gears, roller roller gears, ink rollers, rubber rollers, water rollers, paper feed cams, Rack and machine chassis assembly and adjustment. The accuracy error of these parts formed during printing is expressed directly in the form of a bar, so the severity of the bar is also an overall evaluation of the accuracy of the offset press.