Machinery's Handbook, 31st Edition
1390 TOTAL INDICATOR READING Total Indicator Reading (TIR).— Total indicator reading is used as a measure of the range of machine tool error. TIR is particularly useful for describing the error in a ma- chine tool spindle, referred to as runout. As shown in Fig. 9, there are two types of runout: axial and radial, which can be measured with a dial indicator. Axial runout refers to the wobble of a spindle and is measured at the spindle face. Radial runout is the range of move- ment of the spindle centerline and is measured on the side of the spindle or quill.
Measuring radial runout
Measuring axial runout
Axial runout
Radial runout
Fig. 9.
CAD/CAM CAD in engineering means computer-aided design using a computer graphics sys- tem to develop mechanical, electrical/electronic, and architectural designs. A second D (CADD) is sometimes added for computer-aided drafting and design to indicate use of a computerized drafting or drawing program. CAD technology is the foundation for a wide variety of engineering, design, drafting, analysis, and manufacturing activities. Often a set of drawings initially developed in the design phase of a project is also used for analyz- ing and optimizing the design, creating mechanical drawings of parts and assemblies and for generating NC/CNC part programs that control machining operations. Formerly, after a component had been designed with CAD, the design was passed to a part programmer, who developed a program for machining the components, either manu- ally or directly on a computer (graphic) screen, but the process often required redefining and reentering part geometry. This procedure is often regarded as the CAM part of CAD/ CAM, although CAM (for computer-aided manufacturing) has a much broader meaning and involves the computer in many other manufacturing activities, such as factory simula- tion and planning analyses. Improvements in the speed and capability of computers, oper- ating systems, and programs have simplified the process of integrating the manufacturing process and passing drawings (revised, modified, and translated, as necessary) through the design, analysis, simulation, and manufacturing stages. A CAD drawing is a graphic representation of part geometry data stored in a drawing database file. The drawing database generally contains the complete list of entity (line, arc, etc.) and coordinate information required to build the item drawn. This may include additional information required to define solid surfaces and other model characteristics. Types of CAD Drawings.— The simplest CAD drawings are two-dimensional (2D) and conform to normal engineering drafting practice showing orthographic (front, top, and side views, for example), exploded, isometric, or other views of a component. Depending on the complexity of the part and machining requirements, 2D drawings are often suf- ficient for use in developing NC/CNC part programs.
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