2 Welding Print Reading Copyright Goodheart-Willcox Co., Inc. May not be reproduced or posted to a publicly accessible website. Evolution of Making Prints Before the development of computer-aided design (CAD) systems, a high-quality original draw- ing had to be created. The original drawings needed dense and uniform lines for good reproductions. Manual drawing or drafting was an important skill used to create these drawings from ideas developed by engineers and technicians. However, manual drafting was time-consuming and editing required redrawing. Now, drawings are most typically created using the tools of a computer-aided design (CAD) system. A CAD system is a combination of hardware and software that allows drawings to be drawn, viewed, and output (printed or plotted) electronically. CAD software programs pro- vide drawing, editing, and dimensioning commands and other functions for use in developing original drawings. Manual drawing techniques are sometimes also used. However, the process is slower and less accu- rate than using a CAD system, and the quality of the drawing is dependent upon the drafter’s technique. CAD Systems The growth in the computer field has had a direct and significant impact on the drafting field. The CAD system allows the designer to modify and manipulate the original drawing quickly. Instead of paper and pencil, the changes are made on a computer screen and saved on the storage media of the computer. The saved drawings may be transmitted electronically or retrieved and made into paper prints, Figure 1-2. CAD systems can be used to produce simple part drawings, but the modern CAD system is used to produce a complex three-dimensional model of a part or assembly. The drafter is able to design the part and then view it from all sides. Assemblies can be viewed to see if all of the parts fit together properly, or the CAD system can be used to test the assembly for strength and proper operation. In some design phases, drawings of CAD models are used in the production of prototypes for testing and evaluation purposes. CAD drawing data is also used by machine tools and for quality inspection in automated manufacturing applications. In computer-aided manufacturing (CAM), machining systems use information from drawings to produce parts and assemblies. In this process, data from a CAD drawing is calculated by the system in order to determine the movement and operation of tools. To ensure quality, inspection of the part compares actual dimensions with the CAD drawing data. Printers and Plotters As computers become less expensive, so do the output devices attached to them. Personal computer packages are commonly purchased with a printer. In addition, the price of printers and plotters continues to drop as computers advance. Printers and plotters pro- duce drawings that have dense lines and other features. Sometimes, printing or plotting multiple copies is the easiest and least expensive way to reproduce drawings. However, in situations where dozens of prints must be made, using one of the printmaking processes is best. Ink jet printers are inexpensive devices that produce good quality output. Most are small enough to fit on a desktop, Figure 1-3. Many ink jet printers can print colors. Laser printers work on the electrostatic process. These printers typically produce a very high-quality Figure 1-1. Drawings are used to communicate design of complex products and structures. A—Thrill rides at amusement parks are fabricated using welding processes. B—Complex steel structures, such as this building, are welded rather than riveted. A B