4 Welding Print Reading Copyright Goodheart-Willcox Co., Inc. May not be reproduced or posted to a publicly accessible website. image. Many laser printers are capable of printing large size drawings while maintaining a high-quality image, Figure 1-4. Color laser printers are common. Plotters are most commonly used to make paper drawings from CAD work. There are two types. Ink jet plotters are similar to ink jet printers, except they are used for large-format prints. Pen plotters use pens to reproduce object lines. These devices duplicate the motion that a human hand might make while draw- ing. In other words, they draw lines instead of print- ing “dots” on the page. Pen plotters produce high-quality work, but they are fairly slow. Both ink jet and pen plotters are capable of color output. Older Methods for Reproduction Tracings were commonly made by manual draft- ing when prints were needed. The first step in making a tracing is to draw the part on a translucent (some- what see-through) material. Many types of this mate- rial are available in sheet or roll form. Many drafters made original drawings on the tracing material that would be used to produce the copies. For more complex jobs, the layout was usu- ally “traced” from the original drawing. This is where the term tracing comes from. Tracings and original drawings require a substantial amount of storage space. CAD drawing files are stored using electronic storage methods, which helps improve efficiency. What Is a Print? A print is a reproduction, or duplicate, of an original drawing. Basically, a print consists of the fol- lowing elements: ❍ Lines—show part surfaces and points of machining ❍ Dimensions—give the size of the part ❍ Notes—provide information not given by lines and dimensions ❍ Specifications—special notes for standards, type materials, or specific processes to be used ❍ Views—normally front, side, and top of part When several sets of prints are needed, the origi- nal drawings are reproduced or duplicated. The repro- duction method must be quick and cost-effective. It must produce accurate prints and not destroy the original drawings. Why Are Prints Used? It would be very expensive and impractical to draw a set of plans for each worker who needed them. It is also impractical to replace original drawings when they wear out or become damaged during nor- mal shop use. Instead, reproduction techniques are used to make accurate copies of the original drawings quickly and inexpensively. These copies are usually white prints or bluelines (dark lines on a light back- ground). In the shop, they are known as prints, draw- ings, or blueprints, Figure 1-5. Figure 1-5. Prints are most commonly a white print, or dark lines on a light background. The term “blueprint” is commonly used when referring to all types of prints regardless of color of lines or background. A true blueprint is a print with white lines on a blue background. Reproduction Techniques After an original drawing is completed, it may then be reproduced. As discussed earlier, tracing was one of the first methods to reproduce prints. However, now prints from CAD drawings and models are gen- erated electronically by computer. Drawings can also be reproduced by using xerography or making micro- film from drawings. Older printmaking processes employ a chemical reaction to produce prints. Xerography (Electrostatic) Process Xerography (pronounced ze-rog-ra-fee) is a printmaking process that uses an electrostatic charge to duplicate an original, Figure 1-6. Xerography pro- cess is commonly called electrostatic process. This process is based on the scientific principle that like electrical charges repel and unlike charges attract, Figure 1-7. The electrostatic process exactly duplicates the original. The copy can be enlarged or reduced in size from the original if needed. Unlike older processes, the original drawing does not have to be on translu- cent material.