6 Welding Print Reading Copyright Goodheart-Willcox Co., Inc. May not be reproduced or posted to a publicly accessible website. Large-format engineering copiers can quickly reproduce from original drawings. Some computer networks are connected to imaging systems. These systems receive drawing information from electronic files created with CAD software or special graphics software. The imaging system is able to prepare the printing materials and control the size and resolution of the reproduction. Full-color copies can be made on color copiers. This is an important capability in CAD drafting, because color may be used on final prints to identify items such as welds, wires, piping, or other materials. The Microfilm Process The microfilm process was originally designed to reduce storage facilities and to protect prints from loss. With this technique, the original drawing is reduced by photographic means to negative form. Finished negatives can be stored in roll form or on cards, Figure 1-8. Cards or film are easier to store than full-size drawings. To produce a working print, the microfilm image is retrieved from the files and printed on photographic paper. to use this process, a tracing of the drawing must first be made on translucent material. This material is usu- ally tracing paper or film. A diazo print is made by placing the tracing in contact with light-sensitive paper or film and expos- ing them to light. Light cannot penetrate the opaque pencil or ink lines drawn on the tracing. Exposure takes place when light strikes the light-sensitive coat- ing of the print paper. The print paper is developed after exposure by passing it through ammonia vapors. Where the lines prevent the light from striking the paper, blue lines develop on the print. Blueprints The blueprint process is the oldest of the tech- niques used to duplicate drawings. A blueprint has white lines on a blue background. This process is similar to the diazo process. First, a tracing is made. However, the print must be devel- oped, “fixed” in a chemical solution, washed, and then dried. The blueprint process is not used much any- more. Many times, the term “blueprint” is used to refer to any print. Figure 1-9. For diazo process prints, the original drawing is placed with light-sensitive paper into the machine. The two sheets are exposed to light, and ammonia vapors develop the exposed image. Completed print Developer rolls Tracing is returned to operator Tracing Sensitized paper Light source Exposed print Figure 1-8. Microfilmed drawings can be stored on cards. The drawings can be enlarged and printed later. Older Printmaking Processes There are two older traditional printmaking pro- cesses—the diazo process and the blueprint process. As CAD drafting becomes more prevalent, more prints are generated electronically. This has caused a decline in the use of diazo and blueprint processes. However, you should be familiar with these processes. Diazo Process The diazo process is a copying technique for making direct positive prints, Figure 1-9. Positive prints are dark lines on a white background. The cop- ies are produced quickly and inexpensively. In order