Engineering Drawing 2b3w2g
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Engineering drawing From Wikipedia, the free encyclopedia
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Technical drawings An engineering drawing, a type of technical drawing, is created within the technical drawing discipline, and used to fully and clearly define requirements for engineered items.
Contents [hide] •
1 Overview
•
2 Engineering drawings: common features ○
2.1 Line styles and types
○
2.2 Multiple views and projections
2.2.1 Orthographic projection
2.2.2 Auxiliary projection
2.2.3 Isometric projection
2.2.4 Oblique projection
2.2.5 Perspective
2.2.6 Section Views
○
2.3 Scale
○
2.4 Showing dimensions
○
2.5 Sizes of drawings
○
2.6 Technical lettering
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3 Example of an engineering drawing
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4 See also
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5 References
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6 Further reading
•
7 External links
[edit] Overview
Technical drawing of a certification listing for a firestop system Engineering drawings are usually created in accordance with standardized conventions for layout, nomenclature, interpretation, appearance (such as typefaces and line styles), size, etc. One such standardized convention is called GD&T. Each field in the Fields of engineering will have its own set of requirements for the producing drawings in line weight, symbols, and technical jargon. Some fields of engineering have no GD&T requirements. The purpose of such a drawing is to accurately and unambiguously capture all the geometric features of a product or a component. The end goal of an engineering drawing is to convey all the required information that will allow a manufacturer to produce that component. Engineering drawings used to be created by hand using tools such as pencils, ink, straightedges, T-squares, French curves, triangles, rulers, scales, and erasers. Today they are usually done electronically with computer-aided design (CAD). The drawings are still often referred to as "blueprints" or "bluelines", although those are anachronistic from a literal perspective, since most copies of engineering drawings that were formerly made using a chemical-printing process that yielded graphics on blue-colored paper or, alternatively, of blue-lines on white paper, have been superseded by more modern reproduction processes that yield black or multicolour lines on white paper. The more generic term "print" is now in common usage in the U.S. to mean any paper copy of an engineering drawing.
The process of producing engineering drawings, and the skill of producing them, is often referred to as technical drawing or drafting, although technical drawings are also required for disciplines that would not ordinarily be thought of as parts of engineering.
[edit] Engineering drawings: common features Drawings convey the following critical information: •
Geometry – the shape of the object; represented as views; how the object will look when it is viewed from various angles, such as front, top, side, etc.
•
Dimensions – the size of the object is captured in accepted units.
•
tolerances – the allowable variations for each dimension.
•
Material – represents what the item is made of.
•
Finish – specifies the surface quality of the item, functional or cosmetic. For example, a mass-marketed product usually requires a much higher surface quality than, say, a component that goes inside industrial machinery.
[edit] Line styles and types
Standard engineering drawing line types A variety of line styles graphically represent physical objects. Types of lines include the following: •
visible – are continuous lines used to depict edges directly visible from a particular angle.
•
hidden – are short-dashed lines that may be used to represent edges that are not directly visible.
•
center – are alternately long- and short-dashed lines that may be used to represent the axes of circular features.
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cutting plane – are thin, medium-dashed lines, or thick alternately long- and double shortdashed that may be used to define sections for section views.
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section – are thin lines in a pattern (pattern determined by the material being "cut" or "sectioned") used to indicate surfaces in section views resulting from "cutting." Section lines are commonly referred to as "cross-hatching."
•
phantom - (not shown) are alternately long- and double short-dashed thin lines used to represent a feature or component that is not part of the specified part or assembly. E.g. billet ends that may be used for testing, or the machined product that is the focus of a tooling drawing.
Lines can also be classified by a letter classification in which each line is given a letter. •
Type A lines show the outline of the feature of an object. They are the thickest lines on a drawing and done with a pencil softer than HB.
•
Type B lines are dimension lines and are used for dimensioning, projecting, extending, or leaders. A harder pencil should be used, such as a 2H.
•
Type C lines are used for breaks when the whole object is not shown. They are freehand drawn and only for short breaks. 2H pencil
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Type D lines are similar to Type C, except they are zigzagged and only for longer breaks. 2H pencil
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Type E lines indicate hidden outlines of internal features of an object. They are dotted lines. 2H pencil
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Type F lines are Type F[typo] lines, except they are used for drawings in electrotechnology. 2H pencil
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Type G lines are used for centre lines. They are dotted lines, but a long line of 10– 20 mm, then a gap, then a small line of 2 mm. 2H pencil
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Type H lines are the same as Type G, except that every second long line is thicker. They indicate the cutting plane of an object. 2H pencil
•
Type K lines indicate the alternate positions of an object and the line taken by that object. They are drawn with a long line of 10–20 mm, then a small gap, then a small line of 2 mm, then a gap, then another small line. 2H pencil.
[edit] Multiple views and projections
Image of a part represented in First Angle Projection
Symbols used to define whether a projection is either Third Angle (right) or First Angle (left).
Isometric view of the object shown in the engineering drawing below. Main article: Graphical projection In most cases, a single view is not sufficient to show all necessary features, and several views are used. Types of views include the following: [edit] Orthographic projection The orthographic projection shows the object as it looks from the front, right, left, top, bottom, or back, and are typically positioned relative to each other according to the rules of either first-angle or third-angle projection. •
First angle projection is the ISO standard and is primarily used in Europe. The 3D object is projected into 2D "paper" space as if you were looking at an X-ray of the object: the top view is under the front view, the right view is at the left of the front view.
•
Third angle projection is primarily used in the United States and Canada, where it is the default projection system according to British Standard BS 8888 and ASME standard ASME Y14.3M, the left view is placed on the left and the top view on the top.
Not all views are necessarily used, and determination of what surface constitutes the front, back, top and bottom varies depending on the projection used. [edit] Auxiliary projection An auxiliary view is an orthographic view that is projected into any plane other than one of the six principal views.[1] These views are typically used when an object contains some sort of inclined plane. Using the auxiliary view allows for that inclined plane (and any other significant features) to be projected in their true size and shape. The true size and shape of any feature in an engineering drawing can only be known when the Line of Sight (LOS) is perpendicular to the plane being referenced. [edit] Isometric projection The isometric projection show the object from angles in which the scales along each axis of the object are equal. Isometric projection corresponds to rotation of the object by ± 45° about the vertical axis, followed by rotation of approximately ± 35.264° [= arcsin(tan(30°))] about the horizontal axis starting from an orthographic projection view. "Isometric" comes from the Greek for "same measure". One of the things that makes isometric drawings so attractive is the ease with which 60 degree angles can be constructed with only a com and straightedge. Isometric projection is a type of axonometric projection. The other two types of axonometric projection are: •
Dimetric projection
•
Trimetric projection
[edit] Oblique projection An oblique projection is a simple type of graphical projection used for producing pictorial, two-dimensional images of three-dimensional objects: •
it projects an image by intersecting parallel rays (projectors)
•
from the three-dimensional source object with the drawing surface (projection plan).
In both oblique projection and orthographic projection, parallel lines of the source object produce parallel lines in the projected image. [edit] Perspective
Perspective is an approximate representation on a flat surface, of an image as it is perceived by the eye. The two most characteristic features of perspective are that objects are drawn: •
Smaller as their distance from the observer increases
•
Foreshortened: the size of an object's dimensions along the line of sight are relatively shorter than dimensions across the line of sight.
[edit] Section Views Projected views (either Auxiliary or Orthographic) which show a cross section of the source object along the specified cut plane. These views are commonly used to show internal features with more clarity than may be available using regular projections or hidden lines. In assembly drawings, hardware components (e.g. nuts, screws, washers) are typically not sectioned.
[edit] Scale Main articles: Architect's scale, Engineer's scale, and Metric scale Plans are usually "scale drawings", meaning that the plans are drawn at specific ratio relative to the actual size of the place or object. Various scales may be used for different drawings in a set. For example, a floor plan may be drawn at 1:50 (1:48 or 1/4"=1'-0") whereas a detailed view may be drawn at 1:25 (1:24 or 1/2"=1'-0"). Site plans are often drawn at 1:200 or 1:100.
[edit] Showing dimensions The required sizes of features are conveyed through use of dimensions. Distances may be indicated with either of two standardized forms of dimension: linear and ordinate. •
With linear dimensions, two parallel lines, called "extension lines," spaced at the distance between two features, are shown at each of the features. A line perpendicular to the extension lines, called a "dimension line," with arrows at its endpoints, is shown between, and terminating at, the extension lines. The distance is indicated numerically at the midpoint of the dimension line, either adjacent to it, or in a gap provided for it.
•
With ordinate dimensions, one horizontal and one vertical extension line establish an origin for the entire view. The origin is identified with zeroes placed at the ends of these extension lines. Distances along the x- and y-axes to other features are specified using other extension lines, with the distances indicated numerically at their ends.
Sizes of circular features are indicated using either diametral or radial dimensions. Radial dimensions use an "R" followed by the value for the radius; Diametral dimensions use a circle with forward-leaning diagonal line through it, called the diameter symbol, followed by the value for the diameter. A radially-aligned line with arrowhead pointing to the circular feature, called a leader, is used in conjunction with both diametral and radial dimensions. All types of dimensions are typically composed of two parts: the nominal value, which is the "ideal" size of the feature, and the tolerance, which specifies the amount that the value may vary above and below the nominal. •
Geometric dimensioning and tolerancing is a method of specifying the functional geometry of an object.
[edit] Sizes of drawings Main article: Paper size Sizes of drawings typically comply with either of two different standards, ISO (World Standard) or ANSI/ASME Y14 (American), according to the following tables:
ISO paper sizes ISO A Drawing Sizes (mm) A4 210 X 297 A3 297 X 420 A2 420 X 594 A1 594 X 841 841 X A0 1189 ANSI/ASME Drawing Sizes (inches) A 8.5" X 11" B 11" X 17" C 17" X 22" D 22" X 34" E 34" X 44" Other U.S. Drawing Sizes D1 24" X 36" E1 30" X 42" The metric drawing sizes correspond to international paper sizes. These developed further refinements in the second half of the twentieth century, when photocopying became cheap. Engineering drawings could be readily doubled (or halved) in size and put on the next larger (or, respectively, smaller) size of paper with no waste of space. And the metric technical pens were chosen in sizes so that one could add detail or drafting changes with a pen width changing by approximately a factor of the square root of 2. A full set of pens would have the following nib sizes: 0.13, 0.18, 0.25, 0.35, 0.5, 0.7, 1.0, 1.5, and 2.0 mm. However, the International Organization for Standardization (ISO) called for four pen widths and set a
colour code for each: 0.25 (white), 0.35 (yellow), 0.5 (brown), 0.7 (blue); these nibs produced lines that related to various text character heights and the ISO paper sizes. All ISO paper sizes have the same aspect ratio, one to the square root of 2, meaning that a document designed for any given size can be enlarged or reduced to any other size and will fit perfectly. Given this ease of changing sizes, it is of course common to copy or print a given document on different sizes of paper, especially within a series, e.g. a drawing on A3 may be enlarged to A2 or reduced to A4. The U.S. customary "A-size" corresponds to "letter" size, and "B-size" corresponds to "ledger" or "tabloid" size. There were also once British paper sizes, which went by names rather than alphanumeric designations. American National Standards Institute (ANSI) Y14.2, Y14.3, and Y14.5 are standards that are commonly used in the U.S.
[edit] Technical lettering Technical lettering is the process of forming letters, numerals, and other characters in technical drawing. It is used to describe, or provide detailed specifications for, an object. With the goals of legibility and uniformity, styles are standardized and lettering ability has little relationship to normal writing ability. Engineering drawings use a Gothic sans-serif script, formed by a series of short strokes. Lower case letters are rare in most drawings of machines.
[edit] Example of an engineering drawing
Example mechanical drawing Here is an example of an engineering drawing (an isometric view of the same object is shown above). The different line types are colored for clarity. •
Black = object line and hatching
•
Red = hidden line
•
Blue = center line of piece or opening
•
Magenta = phantom line or cutting plane line
Sectional views are indicated by the direction of arrows, as in the example above.
[edit] See also •
Architectural drawing
•
Engineering drawing symbols
•
CAD standards
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Geometric tolerance
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ISO 128 Technical drawings – General principles of
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Descriptive geometry
•
Document management system
presentation •
Patent drawing
•
Specification (technical standard)
[edit] References 1. ^ Bertoline, Gary R. Introduction to Graphics Communications for Engineers (4th Ed.). New York, NY. 2009
This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (September 2009)
[edit] Further reading •
Basant Agrawal and C M Agrawal (2008). Engineering Drawing. Tata McGraw Hill, New Delhi. [1]
•
Paige Davis, Karen Renee Juneau (2000). Engineering Drawing
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David A. Madsen, Karen Schertz, (2001) Engineering Drawing & Design. Delmar Thomson Learning. [2]
•
Cecil Howard Jensen, Jay D. Helsel, Donald D. Voisinet Computer-aided engineering drawing using AutoCAD.
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Warren Jacob Luzadder (1959). Fundamentals of engineering drawing for technical students and professional.
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M.A. Parker, F. Pickup (1990) Engineering Drawing with Worked Examples.
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Colin H. Simmons, Dennis E. Maguire Manual of engineering drawing. Elsevier.
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Cecil Howard Jensen (2001). Interpreting Engineering Drawings.
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B. Leighton Wellman (1948). Technical Discriptive Geometry. McGraw-Hill Book Company, Inc.
[edit] External links Wikimedia Commons has media related to: Construction drawings •
Examples of cubes drawn in different projections
•
Animated presentation of drawing systems used in technical drawing (Flash animation) [hide]v · d · eVisualization of technical information
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Chart · Computer graphics · Diagram · Graph of a function · Engineering drawing · Ideogram · Information graphics · Map · Image types Photograph · Pictogram · Plot · Statistical graphics · Table · Technical drawings · Technical illustration Jacques Bertin · Stuart Card · Thomas A. DeFanti · Michael Friendly · Nigel Holmes · Alan MacEachren · Jock D. Mackinlay · Michael Maltz · Bruce H. McCormick · Charles Joseph Minard · Otto Neurath · William Experts Playfair · Clifford A. Pickover · Arthur H. Robinson · Lawrence J. Rosenblum · Adolphe Quetelet · George G. Robertson · Ben Shneiderman · Edward Tufte Cartography · Computer graphics · Graph drawing · Graphic design · Related Imaging science · Information science · Mental visualisation · topics Neuroimaging · Scientific modelling · Spatial analysis · Visual analytics · Visual perception Retrieved from "http://en.wikipedia.org/wiki/Engineering_drawing" Categories: Engineering | Technical drawing | Infographics Hidden categories: Articles needing additional references from September 2009 | All articles needing additional references Personal tools
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Technical drawing From Wikipedia, the free encyclopedia
Jump to: navigation, search
Drafter at work.
Copying technical drawings in 1973
Technical drawing, also known as drafting or draughting, is the act and discipline of composing plans that visually communicate how something functions or is to be constructed. A drafter, draftsperson, or draughtsman is a person who makes a drawing (technical or otherwise). A professional drafter who makes technical drawings is sometimes called a drafting technician. People who communicate with technical drawings may use technical standards that define practical symbols, perspectives, units of measurement, notation systems, visual styles, or layout conventions. These enable a drafter to communicate more concisely by using a commonly-understood convention. Together, such conventions constitute a visual language, and help to ensure that the drawing is unambiguous and relatively easy to understand. This need for unambiguous communication in the preparation of a functional document distinguishes technical drawing from the expressive drawing of the visual arts. Artistic drawings are subjectively interpreted; their meanings are multiply determined. Technical drawings are understood to have one intended meaning.[1]
Contents [hide] •
•
•
1 Methods ○
1.1 Sketching
○
1.2 Manual or by instrument
○
1.3 Computer aided design
2 Applications for technical drawing ○
2.1 Architecture
○
2.2 Engineering
3 Related fields ○
•
3.1 Technical illustrations
4 Technical drawings (the document) ○
○
○
4.1 Types of technical drawings
4.1.1 Two-dimensional representation
4.1.2 Three-dimensional representation
4.2 Views
4.2.1 Multiview
4.2.2 Section
4.2.3 Auxiliary
4.2.4 Pattern
4.2.5 Exploded
4.3 Standards and conventions
○
4.3.1 Basic drafting paper sizes
4.4 Patents
○
4.5 Sets of technical drawings
4.5.1 Working drawings
4.5.2 Assembly drawings
•
5 See also
•
6 References
•
7 Further reading
•
8 External links
[edit] Methods
Sketch for a government building.
[edit] Sketching A sketch is a quickly executed freehand drawing that is not intended as a finished work. In general, a sketch is a quick way to record an idea for later use. Architect's sketches primarily serve as a way to try out different ideas and establish a composition before undertaking a more finished work, especially when the finished work is expensive and time consuming. Architectural sketches, for example, are a kind of diagrams.[2] These sketches, like metaphors, are used by architects as a mean of communication in aiding design collaboration. This tool helps architects to abstract attributes of hypothetical provisional design solutions and summarize their complex patterns, hereby enhancing the design process.[2]
[edit] Manual or by instrument
A drafting table.
Technical drawing instruments.
Stencils for correct technical lettering. The basic drafting procedure is to place a piece of paper (or other material) on a smooth surface with right-angle corners and straight sides—typically a drawing board. A sliding straightedge known as a T-square is then placed on one of the sides, allowing it to be slid across the side of the table, and over the surface of the paper. "Parallel lines" can be drawn simply by moving the T-square and running a pencil or technical pen along the T-square's edge, but more typically the T-square is used as a tool to hold other devices such as set squares or triangles. In this case the drafter places one or more triangles of known angles on the T-square—which is itself at right angles to the edge of the table—and can then draw lines at any chosen angle to others on the page. Modern drafting tables (which have by now largely been replaced by CAD workstations) come equipped with a drafting machine that is ed on both sides of the table to slide over a large piece of paper. Because it is secured on both sides, lines drawn along the edge are guaranteed to be parallel. In addition, the drafter uses several tools to draw curves and circles. Primary among these are the comes, used for drawing simple arcs and circles, and the French curve, typically a piece of plastic with complex curves on it. A spline is a rubber coated articulated metal that can be manually bent to most curves. Drafting templates assist the drafter with creating recurring objects in a drawing without having to reproduce the object from scratch every time. This is especially useful when using
common symbols; i.e. in the context of stagecraft, a lighting designer will typically draw from the USITT standard library of lighting fixture symbols to indicate the position of a common fixture across multiple positions. Templates are sold commercially by a number of vendors, usually customized to a specific task, but it is also not uncommon for a drafter to create their own templates. This basic drafting system requires an accurate table and constant attention to the positioning of the tools. A common error is to allow the triangles to push the top of the T-square down slightly, thereby throwing off all angles. Even tasks as simple as drawing two angled lines meeting at a point require a number of moves of the T-square and triangles, and in general drafting can be a time consuming process. A solution to these problems was the introduction of the mechanical "drafting machine", an application of the pantograph (sometimes referred to incorrectly as a "pentagraph" in these situations) which allowed the drafter to have an accurate right angle at any point on the page quite quickly. These machines often included the ability to change the angle, thereby removing the need for the triangles as well. In addition to the mastery of the mechanics of drawing lines, arcs and circles (and text) onto a piece of paper—with respect to the detailing of physical objects—the drafting effort requires a thorough understanding of geometry, trigonometry and spatial comprehension, and in all cases demands precision and accuracy, and attention to detail of high order. Although drafting is sometimes accomplished by a project engineer, architect—or even by shop personnel such as a machinist—skilled drafters (and/or designers) usually accomplish the task and are always in demand to some level.
An oblique view of a four-cylinder inline crankshaft with pistons.
[edit] Computer aided design Main article: Computer-aided design Today, the mechanics of the drafting task have largely been automated and accelerated through the use of computer-aided design systems (CAD). There are two types of computer-aided design systems used for the production of technical drawings" two dimensions ("2D") and three dimensions ("3D"). 2D CAD systems such as AutoCAD replace the paper drawing discipline. The lines, circles, arcs and curves are created within the software. It is down to the technical drawing skill of the to produce the drawing. There is still much scope for error in the drawing when producing first and third angle orthographic projections, auxiliary projections and cross sections. A 2D CAD system is merely an electronic drawing board. Its greatest strength over direct to paper technical drawing is in the making of revisions. Where as in a conventional
hand drawn technical drawing, if a mistake is found, or a modification is required, a new drawing must be made from scratch. The 2D CAD system allows a copy of the original to be modified, saving considerable time. 2D CAD systems can be used to create plans for large projects such as buildings and aircraft but provide no way to check the various components will fit together. 3D CAD systems such as Autodesk Inventor or SolidWorks first produce the geometry of the part, the technical drawing comes from defined views of the part. Any orthographic, projected and section views are created by the software. There is no scope for error in the production of these views. The main scope for error comes in setting the parameter of first or third angle projection, and displaying the relevant symbol on the technical drawing. 3D CAD allows individual parts to be assembled together to represent the final product. Buildings, Aircraft, ships and cars are modeled, assembled and checked in 3D before technical drawings are released for manufacture. Both 2D and 3D CAD systems can be used to produce technical drawings for any discipline. The various disciplines; electical, electronic, pneumatic, fluidic, etc., have industry recognised symbols to represent common components. BS and ISO produce standards to show recommended practices but it is up to individuals to produce the drawings. There is no definitive standard for layout or style. The only standard across engineering workshop drawings is in the creation of orthographic projections and cross section views. Drafting can represent two dimensions ("2D") and three dimensions ("3D") although the representation itself is always created in 2D (cf. Architectural model). Drafting is the integral communication of technical or engineering drawings and is the industrial arts sub-discipline that underlies all involved technical endeavors. In representing complex, three-dimensional objects in two-dimensional drawings, the objects can be described by at least one view plus material thickness note, 2, 3 or as many views and sections that are required to show all features of object.
[edit] Applications for technical drawing [edit] Architecture Main article: Architectural drawing The art and design that goes into making buildings is known as architecture. To communicate all aspects of the design, detailed drawings are used. In this field, the term plan is often used when referring to the full section view of these drawings.[3] Architectural drawings describe and document an architect's design.[4]
Engineering drawing of a Machine tool part.
[edit] Engineering Main article: Engineering drawing
See also: Mechanical engineering Engineering can be a very broad term. It stems from the Latin ingenerare, meaning "to create".[5] Because this could apply to everything that humans create, it is given a narrower definition in the context of technical drawing. Engineering drawings generally deal with mechanical engineered items, such as manufactured parts and equipment. Engineering drawings are usually created in accordance with standardized conventions for layout, nomenclature, interpretation, appearance (such as typefaces and line styles), size, etc. Its purpose is to accurately and unambiguously capture all the geometric features of a product or a component. The end goal of an engineering drawing is to convey all the required information that will allow a manufacturer to produce that component.
Wright brothers Patent drawing, 1908.
[edit] Related fields
Illustration of a drum set.
[edit] Technical illustrations Technical illustration is the use of illustration to visually communicate information of a technical nature. Technical illustrations can be component technical drawings or diagrams. The aim of technical illustration is "to generate expressive images that effectively convey certain information via the visual channel to the human observer".[6] The main purpose of technical illustration is to describe or explain these items to a more or less nontechnical audience. The visual image should be accurate in of dimensions and proportions, and should provide "an overall impression of what an object is or does, to enhance the viewer’s interest and understanding".[7] According to Viola (2005) "illustrative techniques are often designed in a way that even a person with no technical understanding clearly understands the piece of art. The use of varying line widths to emphasize mass, proximity, and scale helped to make a simple line
drawing more understandable to the lay person. Cross hatching, stippling, and other low abstraction techniques gave greater depth and dimension to the subject matter".[6]
Cutaway drawing of a Nash 600. A cutaway drawing is a technical illustration, in which surface elements a three-dimensional model are selectively removed, to make internal features visible, but without sacrificing the outer context entirely. The purpose of a cutaway drawing is to "allow the viewer to have a look into an otherwise solid opaque object. Instead of letting the inner object shine through the surrounding surface, parts of outside object are simply removed. This produces a visual appearance as if someone had cutout a piece of the object or sliced it into parts. Cutaway illustrations avoid ambiguities with respect to spatial ordering, provide a sharp contrast between foreground and background objects, and facilitate a good understanding of spatial ordering".[8]
[edit] Technical drawings (the document) [edit] Types of technical drawings The two types of technical drawings are based on graphical projection.[1] This is used to create an image of a three-dimensional object onto a two-dimensional surface. [edit] Two-dimensional representation Two-dimensional representation uses orthographic projection to create an image where only two of the three dimensions of the object are seen. [edit] Three-dimensional representation In three-dimensional representation, also referred to as pictorials, all three dimensions, of the three dimensions of an object, are visible.
[edit] Views [edit] Multiview Main article: Multiview orthographic projection Multiview is a type of orthographic projection. There are two conventions for using multiview, first-angle and third-angle. In both cases, the front or main side of the object is the same. First-angle is drawing the object sides based on where they land. Example, looking at the front side, rotate the object 90 degrees to the right. What is seen will be drawn to the right of the front side. Third-angle is drawing the object sides based on where they are. Example, looking at the front side, rotate the object 90 degrees to the right. What is seen is actually the left side of the object and will be drawn to the left of the front side [edit] Section While multiview relates to external surfaces of an object, section views show an imaginary plane cut through an object. This is often useful to show voids in an object.
[edit] Auxiliary Auxiliary views utilize an additional projection plane other than the common planes in a multiview. Since the features of an object need to show the true shape and size of the object, the projection plane must be parallel to the object surface. Therefore, any surface that is not in line with the three major axis needs its own projection plane to show the features correctly. [edit] Pattern Patterns, sometimes called developments, show the size and shape of a flat piece of material needed for later bending or folding into a three dimensional shape.[9]
Gear pump exploded view. [edit] Exploded An exploded view drawing is a technical drawing of an object that shows the relationship or order of assembly of the various parts.[10] It shows the components of an object slightly separated by distance, or suspended in surrounding space in the case of a three-dimensional exploded diagram. An object is represented as if there had been a small controlled explosion emanating from the middle of the object, causing the object's parts to be separated an equal distance away from their original locations. An exploded view drawing (EVD) can show the intended assembly of mechanical or other parts. In mechanical systems usually the component closest to the center is assembled first, or is the main part in which the other parts get assembled. This drawing can also help to represent disassembly of parts, where the parts on the outside normally get removed first.[11]
[edit] Standards and conventions [edit] Basic drafting paper sizes Main article: Paper size There have been many standard sizes of paper at different times and in different countries, but today there are two widespread systems in use: the international standard (A4 and its siblings) and the North American sizes.
• ISO "A series" used in most of the world
• North American paper sizes
[edit] Patents Main article: Patent drawing The applicant for a patent will be required by law to furnish a drawing of the invention whenever the nature of the case requires a drawing to understand the invention. This drawing must be filed with the application. This includes practically all inventions except compositions of matter or processes, but a drawing may also be useful in the case of many processes.[10] The drawing must show every feature of the invention specified in the claims, and is required by the patent office rules to be in a particular form. The Office specifies the size of the sheet on which the drawing is made, the type of paper, the margins, and other details relating to the making of the drawing. The reason for specifying the standards in detail is that the drawings are printed and published in a uniform style when the patent issues, and the drawings must also be such that they can be readily understood by persons using the patent descriptions.[10]
[edit] Sets of technical drawings [edit] Working drawings Working drawings are the set of technical drawings used during the manufacturing phase of a product.[12] In architecture, these typically include civil drawings, architectural drawings, structural drawings, mechanical systems drawings, electrical drawings, and plumbing drawings. [edit] Assembly drawings Assembly drawings show how different parts go together, identify those parts by number, and have a parts list, often referred to as a bill of materials.[13]
[edit] See also •
Architectural drawing
•
Engineering drawing
•
ISO 128 Technical drawings—General principles of presentation
•
Plan (drawing)
•
Shop drawing
•
Technical communication
•
Technical lettering
•
Specification (technical standard)
[edit] References
1. ^ a b Goetsch, David L.; Chalk, William S.; Nelson, John A. (2000). Technical Drawing. Delmar Technical Graphics Series (Fourth ed.). Albany: Delmar Learning. p. 3. ISBN 9780766805316. OCLC 39756434. 2. ^ a b Richard Boland and Fred Collopy (2004). Managing as deg. Stanford University Press, 2004. ISBN 0804746745, p.69. 3. ^ Jefferis, Alan; Madsen, David (2005), Architectural Drafting and Design (5th ed.), Clifton Park, NY: Delmar Cengage Learning, ISBN 1401867154 4. ^ Goetsch et al. (2000) p. 792 5. ^ Lieu, Dennis K; Sorby, Sheryl (2009), Visualization, Modeling, and Graphics for Engineering Design (1st ed.), Clifton Park, NY: Delmar Cengage Learning, ISBN 1401842496 , p. 1-2 6. ^ a b Ivan Viola and Meister E. Gröller (2005). "Smart Visibility in Visualization". In: Computational Aesthetics in Graphics, Visualization and Imaging. L. Neumann et al. (Ed.) 7. ^ www.industriegrafik.com The Role of the Technical Illustrator in Industry webarticle, Last modified: Juni 15, 2002. Accessed 15 February 2009. 8. ^ J. Diepstraten, D. Weiskopf & T. Ertl (2003). "Interactive Cutaway Illustrations". in: Eurographics 2003. P. Brunet and D. Fellner (ed). Vol 22 (2003), Nr 3. 9. ^ Goetsch et al. (2000), p. 341 10.^ a b c United States Patent and Trademark Office (2005), General Information Concerning Patents § 1.84 Standards for drawings (Revised January 2005). Accessed 13 February 2009. 11.^ Michael E. Brumbach, Jeffrey A. Clade (2003). Industrial Maintenance. Cengage Learning, 2003 ISBN 0766826953, p.65 12.^ Ralph W. Liebing (1999). Architectural working drawings. John Wiley and Sons, 1999. ISBN 0471348767. 13.^ Goetsch et al. (2000), p. 613
[edit] Further reading •
Peter J. Booker (1963). A History of Engineering Drawing. London: Northgate.
•
Franz Maria Feldhaus (1963). The History of Technical Drawing
•
Wolfgang Lefèvre ed. (2004). Picturing Machines 1400-1700 : How technical drawings shaped early engineering practice. MIT Press, 2004. ISBN 0262122693
[edit] External links Wikimedia Commons has media related to: Technical drawing •
Historical technical diagrams and drawings at NASA.
•
A history of CAD [hide]v · d · eVisualization of technical information Fields
Biological data visualization · Chemical imaging · Crime mapping · Data visualization · Educational visualization · Flow visualization · Geovisualization · Information visualization · Mathematical visualization · Medical imaging · Molecular graphics · Product
visualization · Scientific visualization · Software visualization · Technical drawing · Visual culture · Volume visualization Chart · Computer graphics · Diagram · Graph of a function · Engineering drawing · Ideogram · Information graphics · Map · Photograph · Image types Pictogram · Plot · Statistical graphics · Table · Technical drawings · Technical illustration Jacques Bertin · Stuart Card · Thomas A. DeFanti · Michael Friendly · Nigel Holmes · Alan MacEachren · Jock D. Mackinlay · Michael Maltz · Bruce H. McCormick · Charles Joseph Minard · Otto Neurath · William Experts Playfair · Clifford A. Pickover · Arthur H. Robinson · Lawrence J. Rosenblum · Adolphe Quetelet · George G. Robertson · Ben Shneiderman · Edward Tufte Cartography · Computer graphics · Graph drawing · Graphic design · Related Imaging science · Information science · Mental visualisation · topics Neuroimaging · Scientific modelling · Spatial analysis · Visual analytics · Visual perception Retrieved from "http://en.wikipedia.org/wiki/Technical_drawing" Categories: Architecture occupations | Engineering occupations | Infographics | Technical drawing | Drawings Hidden categories: Use dmy dates from September 2010 Personal tools
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Technical drawings An engineering drawing, a type of technical drawing, is created within the technical drawing discipline, and used to fully and clearly define requirements for engineered items.
Contents [hide] •
1 Overview
•
2 Engineering drawings: common features ○
2.1 Line styles and types
○
2.2 Multiple views and projections
2.2.1 Orthographic projection
2.2.2 Auxiliary projection
2.2.3 Isometric projection
2.2.4 Oblique projection
2.2.5 Perspective
2.2.6 Section Views
○
2.3 Scale
○
2.4 Showing dimensions
○
2.5 Sizes of drawings
○
2.6 Technical lettering
•
3 Example of an engineering drawing
•
4 See also
•
5 References
•
6 Further reading
•
7 External links
[edit] Overview
Technical drawing of a certification listing for a firestop system Engineering drawings are usually created in accordance with standardized conventions for layout, nomenclature, interpretation, appearance (such as typefaces and line styles), size, etc. One such standardized convention is called GD&T. Each field in the Fields of engineering will have its own set of requirements for the producing drawings in line weight, symbols, and technical jargon. Some fields of engineering have no GD&T requirements. The purpose of such a drawing is to accurately and unambiguously capture all the geometric features of a product or a component. The end goal of an engineering drawing is to convey all the required information that will allow a manufacturer to produce that component. Engineering drawings used to be created by hand using tools such as pencils, ink, straightedges, T-squares, French curves, triangles, rulers, scales, and erasers. Today they are usually done electronically with computer-aided design (CAD). The drawings are still often referred to as "blueprints" or "bluelines", although those are anachronistic from a literal perspective, since most copies of engineering drawings that were formerly made using a chemical-printing process that yielded graphics on blue-colored paper or, alternatively, of blue-lines on white paper, have been superseded by more modern reproduction processes that yield black or multicolour lines on white paper. The more generic term "print" is now in common usage in the U.S. to mean any paper copy of an engineering drawing.
The process of producing engineering drawings, and the skill of producing them, is often referred to as technical drawing or drafting, although technical drawings are also required for disciplines that would not ordinarily be thought of as parts of engineering.
[edit] Engineering drawings: common features Drawings convey the following critical information: •
Geometry – the shape of the object; represented as views; how the object will look when it is viewed from various angles, such as front, top, side, etc.
•
Dimensions – the size of the object is captured in accepted units.
•
tolerances – the allowable variations for each dimension.
•
Material – represents what the item is made of.
•
Finish – specifies the surface quality of the item, functional or cosmetic. For example, a mass-marketed product usually requires a much higher surface quality than, say, a component that goes inside industrial machinery.
[edit] Line styles and types
Standard engineering drawing line types A variety of line styles graphically represent physical objects. Types of lines include the following: •
visible – are continuous lines used to depict edges directly visible from a particular angle.
•
hidden – are short-dashed lines that may be used to represent edges that are not directly visible.
•
center – are alternately long- and short-dashed lines that may be used to represent the axes of circular features.
•
cutting plane – are thin, medium-dashed lines, or thick alternately long- and double shortdashed that may be used to define sections for section views.
•
section – are thin lines in a pattern (pattern determined by the material being "cut" or "sectioned") used to indicate surfaces in section views resulting from "cutting." Section lines are commonly referred to as "cross-hatching."
•
phantom - (not shown) are alternately long- and double short-dashed thin lines used to represent a feature or component that is not part of the specified part or assembly. E.g. billet ends that may be used for testing, or the machined product that is the focus of a tooling drawing.
Lines can also be classified by a letter classification in which each line is given a letter. •
Type A lines show the outline of the feature of an object. They are the thickest lines on a drawing and done with a pencil softer than HB.
•
Type B lines are dimension lines and are used for dimensioning, projecting, extending, or leaders. A harder pencil should be used, such as a 2H.
•
Type C lines are used for breaks when the whole object is not shown. They are freehand drawn and only for short breaks. 2H pencil
•
Type D lines are similar to Type C, except they are zigzagged and only for longer breaks. 2H pencil
•
Type E lines indicate hidden outlines of internal features of an object. They are dotted lines. 2H pencil
•
Type F lines are Type F[typo] lines, except they are used for drawings in electrotechnology. 2H pencil
•
Type G lines are used for centre lines. They are dotted lines, but a long line of 10– 20 mm, then a gap, then a small line of 2 mm. 2H pencil
•
Type H lines are the same as Type G, except that every second long line is thicker. They indicate the cutting plane of an object. 2H pencil
•
Type K lines indicate the alternate positions of an object and the line taken by that object. They are drawn with a long line of 10–20 mm, then a small gap, then a small line of 2 mm, then a gap, then another small line. 2H pencil.
[edit] Multiple views and projections
Image of a part represented in First Angle Projection
Symbols used to define whether a projection is either Third Angle (right) or First Angle (left).
Isometric view of the object shown in the engineering drawing below. Main article: Graphical projection In most cases, a single view is not sufficient to show all necessary features, and several views are used. Types of views include the following: [edit] Orthographic projection The orthographic projection shows the object as it looks from the front, right, left, top, bottom, or back, and are typically positioned relative to each other according to the rules of either first-angle or third-angle projection. •
First angle projection is the ISO standard and is primarily used in Europe. The 3D object is projected into 2D "paper" space as if you were looking at an X-ray of the object: the top view is under the front view, the right view is at the left of the front view.
•
Third angle projection is primarily used in the United States and Canada, where it is the default projection system according to British Standard BS 8888 and ASME standard ASME Y14.3M, the left view is placed on the left and the top view on the top.
Not all views are necessarily used, and determination of what surface constitutes the front, back, top and bottom varies depending on the projection used. [edit] Auxiliary projection An auxiliary view is an orthographic view that is projected into any plane other than one of the six principal views.[1] These views are typically used when an object contains some sort of inclined plane. Using the auxiliary view allows for that inclined plane (and any other significant features) to be projected in their true size and shape. The true size and shape of any feature in an engineering drawing can only be known when the Line of Sight (LOS) is perpendicular to the plane being referenced. [edit] Isometric projection The isometric projection show the object from angles in which the scales along each axis of the object are equal. Isometric projection corresponds to rotation of the object by ± 45° about the vertical axis, followed by rotation of approximately ± 35.264° [= arcsin(tan(30°))] about the horizontal axis starting from an orthographic projection view. "Isometric" comes from the Greek for "same measure". One of the things that makes isometric drawings so attractive is the ease with which 60 degree angles can be constructed with only a com and straightedge. Isometric projection is a type of axonometric projection. The other two types of axonometric projection are: •
Dimetric projection
•
Trimetric projection
[edit] Oblique projection An oblique projection is a simple type of graphical projection used for producing pictorial, two-dimensional images of three-dimensional objects: •
it projects an image by intersecting parallel rays (projectors)
•
from the three-dimensional source object with the drawing surface (projection plan).
In both oblique projection and orthographic projection, parallel lines of the source object produce parallel lines in the projected image. [edit] Perspective
Perspective is an approximate representation on a flat surface, of an image as it is perceived by the eye. The two most characteristic features of perspective are that objects are drawn: •
Smaller as their distance from the observer increases
•
Foreshortened: the size of an object's dimensions along the line of sight are relatively shorter than dimensions across the line of sight.
[edit] Section Views Projected views (either Auxiliary or Orthographic) which show a cross section of the source object along the specified cut plane. These views are commonly used to show internal features with more clarity than may be available using regular projections or hidden lines. In assembly drawings, hardware components (e.g. nuts, screws, washers) are typically not sectioned.
[edit] Scale Main articles: Architect's scale, Engineer's scale, and Metric scale Plans are usually "scale drawings", meaning that the plans are drawn at specific ratio relative to the actual size of the place or object. Various scales may be used for different drawings in a set. For example, a floor plan may be drawn at 1:50 (1:48 or 1/4"=1'-0") whereas a detailed view may be drawn at 1:25 (1:24 or 1/2"=1'-0"). Site plans are often drawn at 1:200 or 1:100.
[edit] Showing dimensions The required sizes of features are conveyed through use of dimensions. Distances may be indicated with either of two standardized forms of dimension: linear and ordinate. •
With linear dimensions, two parallel lines, called "extension lines," spaced at the distance between two features, are shown at each of the features. A line perpendicular to the extension lines, called a "dimension line," with arrows at its endpoints, is shown between, and terminating at, the extension lines. The distance is indicated numerically at the midpoint of the dimension line, either adjacent to it, or in a gap provided for it.
•
With ordinate dimensions, one horizontal and one vertical extension line establish an origin for the entire view. The origin is identified with zeroes placed at the ends of these extension lines. Distances along the x- and y-axes to other features are specified using other extension lines, with the distances indicated numerically at their ends.
Sizes of circular features are indicated using either diametral or radial dimensions. Radial dimensions use an "R" followed by the value for the radius; Diametral dimensions use a circle with forward-leaning diagonal line through it, called the diameter symbol, followed by the value for the diameter. A radially-aligned line with arrowhead pointing to the circular feature, called a leader, is used in conjunction with both diametral and radial dimensions. All types of dimensions are typically composed of two parts: the nominal value, which is the "ideal" size of the feature, and the tolerance, which specifies the amount that the value may vary above and below the nominal. •
Geometric dimensioning and tolerancing is a method of specifying the functional geometry of an object.
[edit] Sizes of drawings Main article: Paper size Sizes of drawings typically comply with either of two different standards, ISO (World Standard) or ANSI/ASME Y14 (American), according to the following tables:
ISO paper sizes ISO A Drawing Sizes (mm) A4 210 X 297 A3 297 X 420 A2 420 X 594 A1 594 X 841 841 X A0 1189 ANSI/ASME Drawing Sizes (inches) A 8.5" X 11" B 11" X 17" C 17" X 22" D 22" X 34" E 34" X 44" Other U.S. Drawing Sizes D1 24" X 36" E1 30" X 42" The metric drawing sizes correspond to international paper sizes. These developed further refinements in the second half of the twentieth century, when photocopying became cheap. Engineering drawings could be readily doubled (or halved) in size and put on the next larger (or, respectively, smaller) size of paper with no waste of space. And the metric technical pens were chosen in sizes so that one could add detail or drafting changes with a pen width changing by approximately a factor of the square root of 2. A full set of pens would have the following nib sizes: 0.13, 0.18, 0.25, 0.35, 0.5, 0.7, 1.0, 1.5, and 2.0 mm. However, the International Organization for Standardization (ISO) called for four pen widths and set a
colour code for each: 0.25 (white), 0.35 (yellow), 0.5 (brown), 0.7 (blue); these nibs produced lines that related to various text character heights and the ISO paper sizes. All ISO paper sizes have the same aspect ratio, one to the square root of 2, meaning that a document designed for any given size can be enlarged or reduced to any other size and will fit perfectly. Given this ease of changing sizes, it is of course common to copy or print a given document on different sizes of paper, especially within a series, e.g. a drawing on A3 may be enlarged to A2 or reduced to A4. The U.S. customary "A-size" corresponds to "letter" size, and "B-size" corresponds to "ledger" or "tabloid" size. There were also once British paper sizes, which went by names rather than alphanumeric designations. American National Standards Institute (ANSI) Y14.2, Y14.3, and Y14.5 are standards that are commonly used in the U.S.
[edit] Technical lettering Technical lettering is the process of forming letters, numerals, and other characters in technical drawing. It is used to describe, or provide detailed specifications for, an object. With the goals of legibility and uniformity, styles are standardized and lettering ability has little relationship to normal writing ability. Engineering drawings use a Gothic sans-serif script, formed by a series of short strokes. Lower case letters are rare in most drawings of machines.
[edit] Example of an engineering drawing
Example mechanical drawing Here is an example of an engineering drawing (an isometric view of the same object is shown above). The different line types are colored for clarity. •
Black = object line and hatching
•
Red = hidden line
•
Blue = center line of piece or opening
•
Magenta = phantom line or cutting plane line
Sectional views are indicated by the direction of arrows, as in the example above.
[edit] See also •
Architectural drawing
•
Engineering drawing symbols
•
CAD standards
•
Geometric tolerance
•
ISO 128 Technical drawings – General principles of
•
Descriptive geometry
•
Document management system
presentation •
Patent drawing
•
Specification (technical standard)
[edit] References 1. ^ Bertoline, Gary R. Introduction to Graphics Communications for Engineers (4th Ed.). New York, NY. 2009
This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (September 2009)
[edit] Further reading •
Basant Agrawal and C M Agrawal (2008). Engineering Drawing. Tata McGraw Hill, New Delhi. [1]
•
Paige Davis, Karen Renee Juneau (2000). Engineering Drawing
•
David A. Madsen, Karen Schertz, (2001) Engineering Drawing & Design. Delmar Thomson Learning. [2]
•
Cecil Howard Jensen, Jay D. Helsel, Donald D. Voisinet Computer-aided engineering drawing using AutoCAD.
•
Warren Jacob Luzadder (1959). Fundamentals of engineering drawing for technical students and professional.
•
M.A. Parker, F. Pickup (1990) Engineering Drawing with Worked Examples.
•
Colin H. Simmons, Dennis E. Maguire Manual of engineering drawing. Elsevier.
•
Cecil Howard Jensen (2001). Interpreting Engineering Drawings.
•
B. Leighton Wellman (1948). Technical Discriptive Geometry. McGraw-Hill Book Company, Inc.
[edit] External links Wikimedia Commons has media related to: Construction drawings •
Examples of cubes drawn in different projections
•
Animated presentation of drawing systems used in technical drawing (Flash animation) [hide]v · d · eVisualization of technical information
Fields
Biological data visualization · Chemical imaging · Crime mapping · Data visualization · Educational visualization · Flow visualization · Geovisualization · Information visualization · Mathematical visualization · Medical imaging · Molecular graphics · Product visualization · Scientific visualization · Software visualization · Technical drawing · Visual culture · Volume visualization
Chart · Computer graphics · Diagram · Graph of a function · Engineering drawing · Ideogram · Information graphics · Map · Image types Photograph · Pictogram · Plot · Statistical graphics · Table · Technical drawings · Technical illustration Jacques Bertin · Stuart Card · Thomas A. DeFanti · Michael Friendly · Nigel Holmes · Alan MacEachren · Jock D. Mackinlay · Michael Maltz · Bruce H. McCormick · Charles Joseph Minard · Otto Neurath · William Experts Playfair · Clifford A. Pickover · Arthur H. Robinson · Lawrence J. Rosenblum · Adolphe Quetelet · George G. Robertson · Ben Shneiderman · Edward Tufte Cartography · Computer graphics · Graph drawing · Graphic design · Related Imaging science · Information science · Mental visualisation · topics Neuroimaging · Scientific modelling · Spatial analysis · Visual analytics · Visual perception Retrieved from "http://en.wikipedia.org/wiki/Engineering_drawing" Categories: Engineering | Technical drawing | Infographics Hidden categories: Articles needing additional references from September 2009 | All articles needing additional references Personal tools
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Technical drawing From Wikipedia, the free encyclopedia
Jump to: navigation, search
Drafter at work.
Copying technical drawings in 1973
Technical drawing, also known as drafting or draughting, is the act and discipline of composing plans that visually communicate how something functions or is to be constructed. A drafter, draftsperson, or draughtsman is a person who makes a drawing (technical or otherwise). A professional drafter who makes technical drawings is sometimes called a drafting technician. People who communicate with technical drawings may use technical standards that define practical symbols, perspectives, units of measurement, notation systems, visual styles, or layout conventions. These enable a drafter to communicate more concisely by using a commonly-understood convention. Together, such conventions constitute a visual language, and help to ensure that the drawing is unambiguous and relatively easy to understand. This need for unambiguous communication in the preparation of a functional document distinguishes technical drawing from the expressive drawing of the visual arts. Artistic drawings are subjectively interpreted; their meanings are multiply determined. Technical drawings are understood to have one intended meaning.[1]
Contents [hide] •
•
•
1 Methods ○
1.1 Sketching
○
1.2 Manual or by instrument
○
1.3 Computer aided design
2 Applications for technical drawing ○
2.1 Architecture
○
2.2 Engineering
3 Related fields ○
•
3.1 Technical illustrations
4 Technical drawings (the document) ○
○
○
4.1 Types of technical drawings
4.1.1 Two-dimensional representation
4.1.2 Three-dimensional representation
4.2 Views
4.2.1 Multiview
4.2.2 Section
4.2.3 Auxiliary
4.2.4 Pattern
4.2.5 Exploded
4.3 Standards and conventions
○
4.3.1 Basic drafting paper sizes
4.4 Patents
○
4.5 Sets of technical drawings
4.5.1 Working drawings
4.5.2 Assembly drawings
•
5 See also
•
6 References
•
7 Further reading
•
8 External links
[edit] Methods
Sketch for a government building.
[edit] Sketching A sketch is a quickly executed freehand drawing that is not intended as a finished work. In general, a sketch is a quick way to record an idea for later use. Architect's sketches primarily serve as a way to try out different ideas and establish a composition before undertaking a more finished work, especially when the finished work is expensive and time consuming. Architectural sketches, for example, are a kind of diagrams.[2] These sketches, like metaphors, are used by architects as a mean of communication in aiding design collaboration. This tool helps architects to abstract attributes of hypothetical provisional design solutions and summarize their complex patterns, hereby enhancing the design process.[2]
[edit] Manual or by instrument
A drafting table.
Technical drawing instruments.
Stencils for correct technical lettering. The basic drafting procedure is to place a piece of paper (or other material) on a smooth surface with right-angle corners and straight sides—typically a drawing board. A sliding straightedge known as a T-square is then placed on one of the sides, allowing it to be slid across the side of the table, and over the surface of the paper. "Parallel lines" can be drawn simply by moving the T-square and running a pencil or technical pen along the T-square's edge, but more typically the T-square is used as a tool to hold other devices such as set squares or triangles. In this case the drafter places one or more triangles of known angles on the T-square—which is itself at right angles to the edge of the table—and can then draw lines at any chosen angle to others on the page. Modern drafting tables (which have by now largely been replaced by CAD workstations) come equipped with a drafting machine that is ed on both sides of the table to slide over a large piece of paper. Because it is secured on both sides, lines drawn along the edge are guaranteed to be parallel. In addition, the drafter uses several tools to draw curves and circles. Primary among these are the comes, used for drawing simple arcs and circles, and the French curve, typically a piece of plastic with complex curves on it. A spline is a rubber coated articulated metal that can be manually bent to most curves. Drafting templates assist the drafter with creating recurring objects in a drawing without having to reproduce the object from scratch every time. This is especially useful when using
common symbols; i.e. in the context of stagecraft, a lighting designer will typically draw from the USITT standard library of lighting fixture symbols to indicate the position of a common fixture across multiple positions. Templates are sold commercially by a number of vendors, usually customized to a specific task, but it is also not uncommon for a drafter to create their own templates. This basic drafting system requires an accurate table and constant attention to the positioning of the tools. A common error is to allow the triangles to push the top of the T-square down slightly, thereby throwing off all angles. Even tasks as simple as drawing two angled lines meeting at a point require a number of moves of the T-square and triangles, and in general drafting can be a time consuming process. A solution to these problems was the introduction of the mechanical "drafting machine", an application of the pantograph (sometimes referred to incorrectly as a "pentagraph" in these situations) which allowed the drafter to have an accurate right angle at any point on the page quite quickly. These machines often included the ability to change the angle, thereby removing the need for the triangles as well. In addition to the mastery of the mechanics of drawing lines, arcs and circles (and text) onto a piece of paper—with respect to the detailing of physical objects—the drafting effort requires a thorough understanding of geometry, trigonometry and spatial comprehension, and in all cases demands precision and accuracy, and attention to detail of high order. Although drafting is sometimes accomplished by a project engineer, architect—or even by shop personnel such as a machinist—skilled drafters (and/or designers) usually accomplish the task and are always in demand to some level.
An oblique view of a four-cylinder inline crankshaft with pistons.
[edit] Computer aided design Main article: Computer-aided design Today, the mechanics of the drafting task have largely been automated and accelerated through the use of computer-aided design systems (CAD). There are two types of computer-aided design systems used for the production of technical drawings" two dimensions ("2D") and three dimensions ("3D"). 2D CAD systems such as AutoCAD replace the paper drawing discipline. The lines, circles, arcs and curves are created within the software. It is down to the technical drawing skill of the to produce the drawing. There is still much scope for error in the drawing when producing first and third angle orthographic projections, auxiliary projections and cross sections. A 2D CAD system is merely an electronic drawing board. Its greatest strength over direct to paper technical drawing is in the making of revisions. Where as in a conventional
hand drawn technical drawing, if a mistake is found, or a modification is required, a new drawing must be made from scratch. The 2D CAD system allows a copy of the original to be modified, saving considerable time. 2D CAD systems can be used to create plans for large projects such as buildings and aircraft but provide no way to check the various components will fit together. 3D CAD systems such as Autodesk Inventor or SolidWorks first produce the geometry of the part, the technical drawing comes from defined views of the part. Any orthographic, projected and section views are created by the software. There is no scope for error in the production of these views. The main scope for error comes in setting the parameter of first or third angle projection, and displaying the relevant symbol on the technical drawing. 3D CAD allows individual parts to be assembled together to represent the final product. Buildings, Aircraft, ships and cars are modeled, assembled and checked in 3D before technical drawings are released for manufacture. Both 2D and 3D CAD systems can be used to produce technical drawings for any discipline. The various disciplines; electical, electronic, pneumatic, fluidic, etc., have industry recognised symbols to represent common components. BS and ISO produce standards to show recommended practices but it is up to individuals to produce the drawings. There is no definitive standard for layout or style. The only standard across engineering workshop drawings is in the creation of orthographic projections and cross section views. Drafting can represent two dimensions ("2D") and three dimensions ("3D") although the representation itself is always created in 2D (cf. Architectural model). Drafting is the integral communication of technical or engineering drawings and is the industrial arts sub-discipline that underlies all involved technical endeavors. In representing complex, three-dimensional objects in two-dimensional drawings, the objects can be described by at least one view plus material thickness note, 2, 3 or as many views and sections that are required to show all features of object.
[edit] Applications for technical drawing [edit] Architecture Main article: Architectural drawing The art and design that goes into making buildings is known as architecture. To communicate all aspects of the design, detailed drawings are used. In this field, the term plan is often used when referring to the full section view of these drawings.[3] Architectural drawings describe and document an architect's design.[4]
Engineering drawing of a Machine tool part.
[edit] Engineering Main article: Engineering drawing
See also: Mechanical engineering Engineering can be a very broad term. It stems from the Latin ingenerare, meaning "to create".[5] Because this could apply to everything that humans create, it is given a narrower definition in the context of technical drawing. Engineering drawings generally deal with mechanical engineered items, such as manufactured parts and equipment. Engineering drawings are usually created in accordance with standardized conventions for layout, nomenclature, interpretation, appearance (such as typefaces and line styles), size, etc. Its purpose is to accurately and unambiguously capture all the geometric features of a product or a component. The end goal of an engineering drawing is to convey all the required information that will allow a manufacturer to produce that component.
Wright brothers Patent drawing, 1908.
[edit] Related fields
Illustration of a drum set.
[edit] Technical illustrations Technical illustration is the use of illustration to visually communicate information of a technical nature. Technical illustrations can be component technical drawings or diagrams. The aim of technical illustration is "to generate expressive images that effectively convey certain information via the visual channel to the human observer".[6] The main purpose of technical illustration is to describe or explain these items to a more or less nontechnical audience. The visual image should be accurate in of dimensions and proportions, and should provide "an overall impression of what an object is or does, to enhance the viewer’s interest and understanding".[7] According to Viola (2005) "illustrative techniques are often designed in a way that even a person with no technical understanding clearly understands the piece of art. The use of varying line widths to emphasize mass, proximity, and scale helped to make a simple line
drawing more understandable to the lay person. Cross hatching, stippling, and other low abstraction techniques gave greater depth and dimension to the subject matter".[6]
Cutaway drawing of a Nash 600. A cutaway drawing is a technical illustration, in which surface elements a three-dimensional model are selectively removed, to make internal features visible, but without sacrificing the outer context entirely. The purpose of a cutaway drawing is to "allow the viewer to have a look into an otherwise solid opaque object. Instead of letting the inner object shine through the surrounding surface, parts of outside object are simply removed. This produces a visual appearance as if someone had cutout a piece of the object or sliced it into parts. Cutaway illustrations avoid ambiguities with respect to spatial ordering, provide a sharp contrast between foreground and background objects, and facilitate a good understanding of spatial ordering".[8]
[edit] Technical drawings (the document) [edit] Types of technical drawings The two types of technical drawings are based on graphical projection.[1] This is used to create an image of a three-dimensional object onto a two-dimensional surface. [edit] Two-dimensional representation Two-dimensional representation uses orthographic projection to create an image where only two of the three dimensions of the object are seen. [edit] Three-dimensional representation In three-dimensional representation, also referred to as pictorials, all three dimensions, of the three dimensions of an object, are visible.
[edit] Views [edit] Multiview Main article: Multiview orthographic projection Multiview is a type of orthographic projection. There are two conventions for using multiview, first-angle and third-angle. In both cases, the front or main side of the object is the same. First-angle is drawing the object sides based on where they land. Example, looking at the front side, rotate the object 90 degrees to the right. What is seen will be drawn to the right of the front side. Third-angle is drawing the object sides based on where they are. Example, looking at the front side, rotate the object 90 degrees to the right. What is seen is actually the left side of the object and will be drawn to the left of the front side [edit] Section While multiview relates to external surfaces of an object, section views show an imaginary plane cut through an object. This is often useful to show voids in an object.
[edit] Auxiliary Auxiliary views utilize an additional projection plane other than the common planes in a multiview. Since the features of an object need to show the true shape and size of the object, the projection plane must be parallel to the object surface. Therefore, any surface that is not in line with the three major axis needs its own projection plane to show the features correctly. [edit] Pattern Patterns, sometimes called developments, show the size and shape of a flat piece of material needed for later bending or folding into a three dimensional shape.[9]
Gear pump exploded view. [edit] Exploded An exploded view drawing is a technical drawing of an object that shows the relationship or order of assembly of the various parts.[10] It shows the components of an object slightly separated by distance, or suspended in surrounding space in the case of a three-dimensional exploded diagram. An object is represented as if there had been a small controlled explosion emanating from the middle of the object, causing the object's parts to be separated an equal distance away from their original locations. An exploded view drawing (EVD) can show the intended assembly of mechanical or other parts. In mechanical systems usually the component closest to the center is assembled first, or is the main part in which the other parts get assembled. This drawing can also help to represent disassembly of parts, where the parts on the outside normally get removed first.[11]
[edit] Standards and conventions [edit] Basic drafting paper sizes Main article: Paper size There have been many standard sizes of paper at different times and in different countries, but today there are two widespread systems in use: the international standard (A4 and its siblings) and the North American sizes.
• ISO "A series" used in most of the world
• North American paper sizes
[edit] Patents Main article: Patent drawing The applicant for a patent will be required by law to furnish a drawing of the invention whenever the nature of the case requires a drawing to understand the invention. This drawing must be filed with the application. This includes practically all inventions except compositions of matter or processes, but a drawing may also be useful in the case of many processes.[10] The drawing must show every feature of the invention specified in the claims, and is required by the patent office rules to be in a particular form. The Office specifies the size of the sheet on which the drawing is made, the type of paper, the margins, and other details relating to the making of the drawing. The reason for specifying the standards in detail is that the drawings are printed and published in a uniform style when the patent issues, and the drawings must also be such that they can be readily understood by persons using the patent descriptions.[10]
[edit] Sets of technical drawings [edit] Working drawings Working drawings are the set of technical drawings used during the manufacturing phase of a product.[12] In architecture, these typically include civil drawings, architectural drawings, structural drawings, mechanical systems drawings, electrical drawings, and plumbing drawings. [edit] Assembly drawings Assembly drawings show how different parts go together, identify those parts by number, and have a parts list, often referred to as a bill of materials.[13]
[edit] See also •
Architectural drawing
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Engineering drawing
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ISO 128 Technical drawings—General principles of presentation
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Plan (drawing)
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Shop drawing
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Technical communication
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Technical lettering
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Specification (technical standard)
[edit] References
1. ^ a b Goetsch, David L.; Chalk, William S.; Nelson, John A. (2000). Technical Drawing. Delmar Technical Graphics Series (Fourth ed.). Albany: Delmar Learning. p. 3. ISBN 9780766805316. OCLC 39756434. 2. ^ a b Richard Boland and Fred Collopy (2004). Managing as deg. Stanford University Press, 2004. ISBN 0804746745, p.69. 3. ^ Jefferis, Alan; Madsen, David (2005), Architectural Drafting and Design (5th ed.), Clifton Park, NY: Delmar Cengage Learning, ISBN 1401867154 4. ^ Goetsch et al. (2000) p. 792 5. ^ Lieu, Dennis K; Sorby, Sheryl (2009), Visualization, Modeling, and Graphics for Engineering Design (1st ed.), Clifton Park, NY: Delmar Cengage Learning, ISBN 1401842496 , p. 1-2 6. ^ a b Ivan Viola and Meister E. Gröller (2005). "Smart Visibility in Visualization". In: Computational Aesthetics in Graphics, Visualization and Imaging. L. Neumann et al. (Ed.) 7. ^ www.industriegrafik.com The Role of the Technical Illustrator in Industry webarticle, Last modified: Juni 15, 2002. Accessed 15 February 2009. 8. ^ J. Diepstraten, D. Weiskopf & T. Ertl (2003). "Interactive Cutaway Illustrations". in: Eurographics 2003. P. Brunet and D. Fellner (ed). Vol 22 (2003), Nr 3. 9. ^ Goetsch et al. (2000), p. 341 10.^ a b c United States Patent and Trademark Office (2005), General Information Concerning Patents § 1.84 Standards for drawings (Revised January 2005). Accessed 13 February 2009. 11.^ Michael E. Brumbach, Jeffrey A. Clade (2003). Industrial Maintenance. Cengage Learning, 2003 ISBN 0766826953, p.65 12.^ Ralph W. Liebing (1999). Architectural working drawings. John Wiley and Sons, 1999. ISBN 0471348767. 13.^ Goetsch et al. (2000), p. 613
[edit] Further reading •
Peter J. Booker (1963). A History of Engineering Drawing. London: Northgate.
•
Franz Maria Feldhaus (1963). The History of Technical Drawing
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Wolfgang Lefèvre ed. (2004). Picturing Machines 1400-1700 : How technical drawings shaped early engineering practice. MIT Press, 2004. ISBN 0262122693
[edit] External links Wikimedia Commons has media related to: Technical drawing •
Historical technical diagrams and drawings at NASA.
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A history of CAD [hide]v · d · eVisualization of technical information Fields
Biological data visualization · Chemical imaging · Crime mapping · Data visualization · Educational visualization · Flow visualization · Geovisualization · Information visualization · Mathematical visualization · Medical imaging · Molecular graphics · Product
visualization · Scientific visualization · Software visualization · Technical drawing · Visual culture · Volume visualization Chart · Computer graphics · Diagram · Graph of a function · Engineering drawing · Ideogram · Information graphics · Map · Photograph · Image types Pictogram · Plot · Statistical graphics · Table · Technical drawings · Technical illustration Jacques Bertin · Stuart Card · Thomas A. DeFanti · Michael Friendly · Nigel Holmes · Alan MacEachren · Jock D. Mackinlay · Michael Maltz · Bruce H. McCormick · Charles Joseph Minard · Otto Neurath · William Experts Playfair · Clifford A. Pickover · Arthur H. Robinson · Lawrence J. Rosenblum · Adolphe Quetelet · George G. Robertson · Ben Shneiderman · Edward Tufte Cartography · Computer graphics · Graph drawing · Graphic design · Related Imaging science · Information science · Mental visualisation · topics Neuroimaging · Scientific modelling · Spatial analysis · Visual analytics · Visual perception Retrieved from "http://en.wikipedia.org/wiki/Technical_drawing" Categories: Architecture occupations | Engineering occupations | Infographics | Technical drawing | Drawings Hidden categories: Use dmy dates from September 2010 Personal tools
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