10 Minutes For You To Fully Deconstruct The Offset Press

Date:May 30, 2018

Offset printing is a kind of indirect printing method in which the ink on the upper part of the plate is transferred to the surface of the substrate via an intermediate carrier, a rubber (rubber) roller, based on the principle of oil and water incompatibility. The degree of mastery of in offset printing operations not only reflects the proficiency of the operators in each specific operation, but also represents the operator's printing knowledge, ability and experience.

    The status quo and development trend of offset press

The level of imported sheet-fed offset presses has taken a big step forward in the 1990s. mainly reflects in:

1) The printing speed increased to 15,000 sheets/hour.

2) As the level of automatic control increases, the pre-adjustment time before printing is greatly shortened. The original pre-adjustment time is generally about 2 hours, but now can be reduced to 15 minutes;

3) The degree of automation has been greatly improved. The entire printing press operation and operating system can be fully automated from paper handling to printing.

The future development trend of printing presses is still the integration of machine, electricity, light and sound, and ultimately achieve full automation.

Classification of sheetfed offset presses

1, according to purpose classification. Can be divided into offset printing press paper, proofing offset printing press, offset printing press and so on.

2, according to the number of printing color classification. Can be divided into monochrome, two-color, four-color, five-color offset press and so on.

3, according to the size of paper size. Can be divided into souvenir sheets, full sheets, open, four open, eight open offset press and so on.

4, according to the situation of printing the printing surface classification. Can be divided into single-sided printing and double-sided printing offset press.

Offset printing machine

3.1 The composition of the offset press The offset press consists of three parts: paper feeding, printing, and paper collection. The drive mechanism drives the coordinated movement of each part.

The basic composition of the offset press and the name of each part

1). Paper feeding part: Its function is to pile up the paper for printing, and separate and transport it to the printing part. It is mainly composed of paper separation, paper-feeding station, paper conveying, automatic control mechanism, and gas system.

2), printing part: Its function is to print on the substrate, mainly consists of positioning, wetting, inking and imprinting device.

3) The paper delivery part: Its function is to collect and accumulate the papers printed by Mainly by the collection of paper chain, paper, paper stacking mechanism and anti-fouling dusting device and other components.

Offset machine name

1), the paper feeding end: the entrance end of the paper.

2) The delivery end: the exit end of the paper.

3) Operation side: refers to the side on which the machine operates. There is a main operation panel and the like, usually on the left side from the sheet feeding end toward the delivery end.

4) Drive side: The side opposite to the operating side. There are transmission motors, transmission gears and so on.

Offset operation panel

Offset presses are equipped with operation panels. The buttons (buttons) on the operation panel vary depending on the manufacturer, model, and degree of automation. However, the basic function keys are generally the same as described below.

The operation panel is generally divided into a main operation panel and a sub-operation panel.

5.1. Main operation panel: The main control device that concentrates the press buttons of the whole machine and is set at the side of the operation paper feeding table. Mainly include: bells, forward and reverse jogging, operation, operation stop, paper feeding, paper feeding, paper feed pump, paper delivery air pump, pressurization, stop (lock) and other keys.

5.2. Sub-operation panel: There are multiple, set in different locations.

(1) Paper feeding position: It is mainly used to control the lifting and lowering of the paper feeding table. There are paper stacks and paper stacks.

(2) Each group of printing cylinders: one for the left and one for the next, and one for the paper-feeding platen. It is mainly used for disassembling plates and blankets and controlling water supply and ink supply. Bells, forward and reverse jog, stop (lock), ink open, ink stop, water open, water stop and other buttons.

(3) The delivery site: It is mainly used to control the lifting and lowering of the delivery section of the delivery section, as well as the operation of emergency stop and stop of the paper feeding, and timely control of the production process. There is a stop (lock) machine, electric bell, positive and negative jogging, paper feeding, operation stop, delivery air pump, paper stack up, down, count switch, fault detection lamp and so on.

Offset safety device

In order to prevent accidents and ensure the safety of operators and machines, offset presses are generally equipped with appropriate safety devices. The following are commonly used:

6.1.Protective covers: Sealing covers are installed on the outside of the wall panels on both the operating surface and the transmission surface; in the chain drive, belt transmission parts, the front of the delivery position, plate cylinders and blanket cylinders, water rollers and ink rollers There is a protective cover between each other. The main role is to protect the safety of the operator; to ensure the accuracy of the machine drive and lubrication; prevent foreign body intrusion.

6.2, "stop lock" switch: In the offset press main and auxiliary operating panel, generally have a "stop lock" switch for operators to use when necessary. After the lock is stopped, all the keys except the “bell” will not work. At this time, the machine will not start even if the “bell” is pressed. After unlocking the lock, press the "bell" first to start the machine normally. Heidelberg electromechanical bell and jog are two.

6.3, safety bar: set between the plate cylinder and rubber roller, its role is to protect the safety of operators, once the operator inadvertently wipe cloth, clothing and fingers, etc. rolled into the machine, move the clockwise safety bar, can cut off the power , stop the machine from turning. In addition, there is also a safety bar at the front gauge of the front edge of the paper sheet to prevent accidents caused by multiple sheets of paper and foreign matter on the paper entering the drum.

6.4, paper stack lifting safety protection device: the paper feed table and the delivery table are equipped with a limit switch to control stacking paper lift, control the paper stack in the required range.

6.5. Empty and double sheet detectors: The empty sheet detector is set at the front gauge to detect if the sheets are empty, skewed and not in place. The two-sheet controller is set on the take-up roller (or tape reel) of the feeder to prevent double sheets from entering the print unit.

When a sheet-fed, sheet-fed, or double sheet-fed sheet failure occurs, the empty-sheet or double-sheet controller immediately sends a signal, and the interlock mechanism acts to stop the sheet feeding, the drum is separated from pressure, and the ink roller and the plate cylinder leave. The water fountain roller stops rotating, the ink transfer roller and the roller disengage, the counter stops counting, and the main motor falls to a series of chain reactions such as low speed.

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