Structure composition of inner drum typesetting machine
It is mainly composed of semi-circular hollow drum, film conveying and cutting mechanism, laser and optical system, high-speed rotating central scanning head, slow-speed lateral moving mechanism and control circuit.
Features of inner drum typesetting machine
The inner drum typesetting machine has the dual advantages of continuous filming of the winch typesetting machine and high accuracy of the outer drum typesetting machine. Inner drum laser imagesetter usually selects visible red laser as light source. It has small volume, long life, easy to modulate, and it can be continuous or single sheet. The price of the inner drum typesetting machine is the most expensive.
Inner drum imagesetter is considered to be the best type of imagesetter structure, and almost all high-end imagesetters adopt this structure. This structure has the characteristics of high recording accuracy, large format, high degree of automation, easy operation and fast speed, but the price is more expensive than the first two types of imagesetter.
Working method of inner drum typesetting machine
The recording film is placed on the inner circumference of the drum. The drum and the film do not move and are scanned and recorded by the laser beam, so there is no error caused by unevenness of the film. The laser beam is located on the central axis of the drum, and the laser can rotate around the central axis, recording 1 line per revolution, while the laser moves 1 line in the axial direction. It can be seen that the recording beam of this structure has the same distance from any point of the film. Therefore, the light spot is not deformed, and the problem of reduced recording accuracy caused by unstable film transmission can be effectively avoided, which is why it has a very high repeat accuracy. On the other hand, since the roller does not move, the light beam is deflected by the rotation of the prism. The prism is very light and the rotational inertia is very small, so the rotation speed can be very high, making the recording speed very fast.
Structure composition of external drum typesetting machine
It is composed of a roller, a laser optical system platform, a platform horizontal movement mechanism, an upper and lower film mechanism, an upper and lower film box, a control circuit and a vacuum pump.
The working mode of the outer drum typesetting machine is similar to the working mode of the traditional electric extension machine. The recording film is attached to the outer circumference of the drum and rotates with the drum. Each rotation records a line, and the laser head moves horizontally and then records the next line. The advantages of this typesetting machine are that the recording accuracy and register accuracy are high, the structure is simple, the work is stable, and the recording format can be made large.
Features of the outer drum typesetting machine
The recording accuracy and registration accuracy are high, the output speed is fast, the structure is simple, the work is stable, and it is particularly suitable for large-format phototypesetting output. The structure of the outer drum typesetting machine is very suitable for direct plate-making machine. Multiple lasers can be used to speed up the exposure. Only a single film can be output. The gap between multiple laser beams requires high machining accuracy and is not easy to be uniform.
The disadvantage of the outer drum typesetting machine is that it is inconvenient to operate and has a low degree of automation. It usually requires manual loading and unloading. When loading and unloading manually, it needs to be operated in a dark room. The recording drum of the large-format imagesetter is large, requiring an air extraction system and a film fixing device, and the larger the recording drum, the greater the inertia when rotating, and the rotation speed is limited. The recording speed is lower, and the number of laser beams must be increased To increase the recording speed. Therefore, this type of imagesetter is currently rarely used.
However, the outer drum structure is very suitable for direct plate-making machine, because direct plate-making is a single plate, not a continuous piece, the plate size is fixed, and the direct plate can be operated in the bright room, which partially offsets its shortcomings, plus this The light path of this structure is short, easy to control, and the laser loss is small, you can use multiple lasers to speed up the exposure speed. In addition, the outer cylinder structure is simple in handling dust during plate making, and the plate-up method is the same as that of the printing press, so it can achieve high accuracy. With the improvement of design level, the degree of automation will also continue to improve, so it is considered to be the best direct plate-making machine structure.
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