Every EA should have a basic understanding of the various functions of the Ozalid (fig. 3-62);therefore, in this section we will discuss printing and developing, as well as the operating principles of the cooling and exhaust system. Information is also given on machine operation, adjustments, and maintenance.

PRINTING SECTION. Figure 3-63 shows the principles of operation of the printing and

developing sections. Of particular interest at this point is the printing section. This section is divided into four basic units: light source, reflector assembly, printing cylinder, and feed belts.

During the reproduction process, the original and a piece of material, such as paper that has been sensitized (coated with a light, sensitive dye), are inserted into the machine. Sensitized material is placed with the emulsion side up on the feed-board, and the original is placed on top. Originals should be of a transparent or translucent nature with an opaque image on one side only. Feed belts carry this material around the revolving printing cylinder where the dye of the treated paper that is NOT covered by the opaque image of the original is desensitized by the ultraviolet light rays emitted from the mercury-vapor lamp. After exposure, the original and print are picked off of the printing cylinder by the pick-off assembly, and directed towards the developing section.

After pick-off, the guide roller directs the original and print between a printer and tracing separator belt. These belts cause the print and the original to be delivered to two separator tank assemblies where the original and print are separated from each other.

The process of separation is unique and is therefore worthy of further discussion. Critical to the operation of separation are perforations in the walls of the two separator tanks. During

Figure 3-63.-Principles of operation.

operation, air that is drawn through these holes causes a difference in pressure that causes the original to follow the tracing belt and the print to follow the printer belt. Thus, the original and print are separated and directed in different directions. The original moves out of the machine, and the print moves into the developing section where ammonia vapors develop those areas that were not desensitized. It should be noted that it is possible, should the need arise, to direct both the original and the print out of the machine before they go to the developing section. All that is necessary to accomplish this is to operate a lever. When the lever is operated, a group of fingers is extended. These fingers cause the print to be directed out of the machine, along with the original. One instance in which it is desirable to remove the print is when the sensitized paper is coated on both sides. In this instance, the second side will be exposed before any developing takes place.