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Engineering Drawing. Introduction to Graphics Communication By: Dr Hamid Ullah Khan Niazi. Lecture Outline. Introduction Standard for drawing sheet Media Alphabet of lines Scale Next class. Introduction.
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Engineering Drawing Introduction to Graphics Communication By: Dr Hamid Ullah Khan Niazi
Lecture Outline • Introduction • Standard for drawing sheet • Media • Alphabet of lines • Scale • Next class
Introduction • Engineers: People who use technical means to solve problems. They design products, systems, devices, and structures to improve our living conditions • Technical Drawings: a clear, precise language used in the design process for communicating, solving problems, quickly and accurately visualizing objects, and conducting analyses • A graphical representation of objects and structures is done using freehand, mechanical, or computer methods
HISTORY • The earliest known technical drawing was created about 4000 BC. The first written evidence of technical drawings dates to 30 BC. • In 1876, the blueprinting machine was developed. • From about 1750, when Gaspard Monge developed descriptive geometry practices/ • By about 1900, most drawings were created using first-angle projection. Starting in the late nineteenth century, most companies in the United States switched to third-angle projection. Third-angle projection is considered a more logical or natural positioning of views.
Media • Media: surfaces upon which an engineer or technologist communicates graphical information. Different types include: • Tracing paper (a thin, translucent paper used for detail drawings) • Vellum (tracing paper chemically treated to improve translucency) • Polyester film (transparent, waterproof, and difficult to tear, “Mylar”) • The American National Standard Institute (ANSI) has established standard sheet sizes and title blocks for media used in technical drawings
Types of line Long Break Lines • Long, thin lines. • Used to show that the middle section of an object has been removed so it can be drawn on a smaller piece of paper. Short Break Lines • Thick wavy line. • Used to break the edge or surface of a part for clarity of a hidden surface.
ASME Y14 standards • The following are ASME Y14 standards that are basic engineering drawing standards: • ASME Y14.1, Decimal Inch Drawing Sheet Size and Format • ASME Y14.1M, Metric Drawing Sheet Size and Format • ASME Y14.2, Line Conventions and Lettering • ASME Y14.3, Orthographic and Pictorial Views • ASME Y14.5, Dimensioning and Tolerances • ASME Y14.24, Types and Applications of Engineering Drawings • ASME Y14.34, Associated Lists • ASME Y14.35M, Revision of Engineering Drawings and Associated Documents • ASME Y14.36M, Surface Texture Symboles • ASME Y14.38, Abbreviations and Acronyms for Use on Drawings and Related Documents • ASME Y14.41, Digital Product Definition Data Practices • ASME Y14.100, Engineering Drawing Practices • All other ASME Y14 standards are considered specialty types of standards and contain additional requirements or make exceptions to the basic standards as required to support a process or type of drawing.
Phantom Line Phantom Lines • Thin lines made up of long dashes alternating with pairs of short dashes.
Break Line A break line saves drawing space by eliminating unnecessary length.
Introduction (con’t) • 92% of the design process is graphical • The remaining 8% is mathematics and written communication Breakdown of Engineer’s time Who uses engineering graphics?
Introduction (con’t) • Practice Exercise 1.1 • Attempt to describe the part shown in this figure verbally to the person seatednext to you Fig. 1.89 • How easy is it to describe a part such as this without the use of graphics?
Drawing Tools (con’t) The use of drafting tools
Alphabet of Lines • Pencil Grades • Line Weight Remember that Accuracy, Neatness, and Speed count in technical drawing
Next Lecture • Purchase drafting tools needed for manual drafting portion of class if you have not done so • Read the topics on Lines and lettering