Technical drawing

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Drafter at work Drafter at work.jpg
Drafter at work
Copying technical drawings in 1973 Bundesarchiv B 145 Bild-F038800-0010, Wolfsburg, VW Autowerk.jpg
Copying technical drawings in 1973

Technical drawing, drafting or drawing, is the act and discipline of composing drawings that visually communicate how something functions or is constructed.

Contents

Technical drawing is essential for communicating ideas in industry and engineering. To make the drawings easier to understand, people use familiar symbols, perspectives, units of measurement, notation systems, visual styles, and page layout. Together, such conventions constitute a visual language and help to ensure that the drawing is unambiguous and relatively easy to understand. Many of the symbols and principles of technical drawing are codified in an international standard called ISO 128.

The need for precise 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]

A drafter, draftsperson, or draughtsman is a person who makes a drawing (technical or expressive). A professional drafter who makes technical drawings is sometimes called a drafting technician.

Methods

Sketching

Sketch for a government building Architekturskizze Verwaltungsgebaude Biel.jpg
Sketch for a government building

A sketch is a quickly executed, freehand drawing that is usually not intended as a finished work. In general, sketching 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 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 means of communication in aiding design collaboration. This tool helps architects to abstract attributes of hypothetical provisional design solutions and summarize their complex patterns, thereby enhancing the design process. [2]

Manual or by instrument

A drafting table Zeichenmaschine.jpg
A drafting table
Old-fashioned technical drawing instruments Technical drawing instruments 1.jpg
Old-fashioned technical drawing instruments
Stencils for lettering technical drawings to DIN standards Stencils01.jpg
Stencils for lettering technical drawings to DIN standards

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 by moving the T-square and running a pencil or technical pen along the T-square's edge. The T-square is used 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 are equipped with a drafting machine that is supported 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. [3]

The drafter uses several technical drawing tools to draw curves and circles. Primary among these are the compasses, used for drawing arcs and circles, and the French curve, for drawing curves. 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 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 his 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 quickly. These machines often included the ability to change the angle, hence removing the need for the triangles.

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 shop personnel (such as a machinist), skilled drafters (and/or designers) usually accomplish the task, and are always in demand to some degree.

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").

An example of a drawing drafted in AutoCAD Construction drawing autocad.jpg
An example of a drawing drafted in AutoCAD

2D CAD systems such as AutoCAD or MicroStation 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 user 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-section views. 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. Whereas 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.

View of a CAD model of a four-cylinder inline crankshaft with pistons Cad crank.jpg
View of a CAD model of a four-cylinder inline crankshaft with pistons

A 3D CAD system (such as KeyCreator, Autodesk Inventor, or SolidWorks) first produces the geometry of the part; the technical drawing comes from user defined views of that geometry. Any orthographic, projected or sectioned view is 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 modelled, 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 (electrical, electronic, pneumatic, hydraulic, etc.) have industry recognized symbols to represent common components.

BS and ISO produce standards to show recommended practices but it is up to individuals to produce the drawings to a standard. 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.

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.

Applications

Architecture

To plan a renovation, this architect takes measurements he will later enter into his computer-aided design system. Architect Anthony Murphy working on a kitchen renovation project in New Jersey.jpg
To plan a renovation, this architect takes measurements he will later enter into his computer-aided design system.

The art and design that goes into making buildings is known as architecture. To communicate all aspects of the shape or design, detail drawings are used. In this field, the term plan is often used when referring to the full section view of these drawings as viewed from three feet above finished floor to show the locations of doorways, windows, stairwells, etc. [4] Architectural drawings describe and document an architect's design. [5]

Engineering

Engineering can be a very broad term. It stems from the Latin ingenerare, meaning "to create". [6] 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 drawing of a machine tool part DIN 69893 hsk 63a drawing.png
Engineering drawing of a machine tool part

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.

Software engineering

Software engineering practitioners make use of diagrams for designing software. Formal standards and modelling languages such as Unified Modelling Language (UML) exist but most diagramming happens using informal ad hoc diagrams that illustrate a conceptual model. [7]

Practitioners reported that diagramming helped with analysing requirements, [7] :539 design, refactoring, documentation, onboarding, communication with stake holders. [8] :560 Diagrams are often transient or redrawn as required. Redrawn diagrams can act as a form of shared understanding in a team. [8] :561

Technical illustration

Illustration of a drum set Drum set.svg
Illustration of a drum set

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". [9]

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 terms 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". [10]

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". [9]

Cutaway drawing

Cutaway drawing of the Nash 600, an American car of the 1940s 1942 Nash Ambassador X-ray.jpg
Cutaway drawing of the Nash 600, an American car of the 1940s

A cutaway drawing is a technical illustration, in which part of the surface of a three-dimensional model is removed in order to show some of the model's interior in relation to its exterior.

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". [11]

Technical drawings

Types

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.

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.

Three-dimensional representation

In a three-dimensional representation, also referred to as a pictorial, all three dimensions of an object are visible.

Views

Multiview

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.

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.

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.

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. [12]

Exploded

Exploded-view drawing of a gear pump Gear pump exploded.svg
Exploded-view drawing of a gear pump

An exploded-view drawing is a technical drawing of an object that shows the relationship or order of assembly of the various parts. [13] 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 relative distances away from their original locations.

An exploded view drawing (EVD) can show the intended assembly of mechanical or other parts. In mechanical systems, the component closest to the center is usually assembled first or is the main part inside which the other parts are assembled. The EVD can also help to represent the disassembly of parts, where those on the outside are normally removed first. [14]

Standards and conventions

Basic drafting paper sizes

There have been many standard sizes of paper at different times and in different countries, but today most of the world uses the international standard (A4 and its siblings). North America uses its own sizes.

Patent drawing

The Wright brothers' patent drawings for their aeroplane (1908) Wright brothers patent plans 1908.jpg
The Wright brothers' patent drawings for their aeroplane (1908)

The applicant for a patent will be required by law to furnish a drawing of the invention if or when the nature of the case requires a drawing to understand the invention with the job. 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. [13]

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. [13]

Sets of technical drawings

Working drawings for production

Working drawings are the set of technical drawings used during the manufacturing phase of a product. [15] In architecture, these include civil drawings, architectural drawings, structural drawings, mechanical systems drawings, electrical drawings, and plumbing drawings.

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. [16] In a technical service manual, this type of drawing may be referred to as an exploded view drawing or diagram. These parts may be used in engineering.

As-fitted drawings

Also called As-Built drawings or As-made drawings. As-fitted drawings represent a record of the completed works, literally 'as fitted'. These are based upon the working drawings and updated to reflect any changes or alterations undertaken during construction or manufacture. [17]

See also

Related Research Articles

<span class="mw-page-title-main">Computer-aided design</span> Constructing a product by means of computer

Computer-Aided Design (CAD) is the use of computers to aid in the creation, modification, analysis, or optimization of a design. This software is used to increase the productivity of the designer, improve the quality of design, improve communications through documentation, and to create a database for manufacturing. Designs made through CAD software help protect products and inventions when used in patent applications. CAD output is often in the form of electronic files for print, machining, or other manufacturing operations. The terms computer-aided drafting (CAD) and computer-aided design and drafting (CADD) are also used.

A view is a sight or prospect or the ability to see or be seen from a particular place.

<span class="mw-page-title-main">Isometric projection</span> Method for visually representing three-dimensional objects

Isometric projection is a method for visually representing three-dimensional objects in two dimensions in technical and engineering drawings. It is an axonometric projection in which the three coordinate axes appear equally foreshortened and the angle between any two of them is 120 degrees.

<span class="mw-page-title-main">Engineering drawing</span> Type of technical drawing used to define requirements for engineered items

An engineering drawing is a type of technical drawing that is used to convey information about an object. A common use is to specify the geometry necessary for the construction of a component and is called a detail drawing. Usually, a number of drawings are necessary to completely specify even a simple component. The drawings are linked together by a master drawing or assembly drawing which gives the drawing numbers of the subsequent detailed components, quantities required, construction materials and possibly 3D images that can be used to locate individual items. Although mostly consisting of pictographic representations, abbreviations and symbols are used for brevity and additional textual explanations may also be provided to convey the necessary information.

<span class="mw-page-title-main">Orthographic projection</span> Means of projecting three-dimensional objects in two dimensions

Orthographic projection is a means of representing three-dimensional objects in two dimensions. Orthographic projection is a form of parallel projection in which all the projection lines are orthogonal to the projection plane, resulting in every plane of the scene appearing in affine transformation on the viewing surface. The obverse of an orthographic projection is an oblique projection, which is a parallel projection in which the projection lines are not orthogonal to the projection plane.

<span class="mw-page-title-main">3D projection</span> Design technique

A 3D projection is a design technique used to display a three-dimensional (3D) object on a two-dimensional (2D) surface. These projections rely on visual perspective and aspect analysis to project a complex object for viewing capability on a simpler plane.

<span class="mw-page-title-main">Axonometric projection</span> Type of orthographic projection

Axonometric projection is a type of orthographic projection used for creating a pictorial drawing of an object, where the object is rotated around one or more of its axes to reveal multiple sides.

<span class="mw-page-title-main">Descriptive geometry</span> Branch of geometry which allows the representation of three-dimensional objects in two dimensions

Descriptive geometry is the branch of geometry which allows the representation of three-dimensional objects in two dimensions by using a specific set of procedures. The resulting techniques are important for engineering, architecture, design and in art. The theoretical basis for descriptive geometry is provided by planar geometric projections. The earliest known publication on the technique was "Underweysung der Messung mit dem Zirckel und Richtscheyt", published in Linien, Nuremberg: 1525, by Albrecht Dürer. Italian architect Guarino Guarini was also a pioneer of projective and descriptive geometry, as is clear from his Placita Philosophica (1665), Euclides Adauctus (1671) and Architettura Civile, anticipating the work of Gaspard Monge (1746–1818), who is usually credited with the invention of descriptive geometry. Gaspard Monge is usually considered the "father of descriptive geometry" due to his developments in geometric problem solving. His first discoveries were in 1765 while he was working as a draftsman for military fortifications, although his findings were published later on.

<span class="mw-page-title-main">Oblique projection</span> Type of technical drawing

Oblique projection is a simple type of technical drawing of graphical projection used for producing two-dimensional (2D) images of three-dimensional (3D) objects.

<span class="mw-page-title-main">Floor plan</span> Architectural diagram showing interior layout of a building

In architecture and building engineering, a floor plan is a technical drawing to scale, showing a view from above, of the relationships between rooms, spaces, traffic patterns, and other physical features at one level of a structure.

<span class="mw-page-title-main">Parallel projection</span> Projection of a 3D object onto a plane via parallel rays

In three-dimensional geometry, a parallel projection is a projection of an object in three-dimensional space onto a fixed plane, known as the projection plane or image plane, where the rays, known as lines of sight or projection lines, are parallel to each other. It is a basic tool in descriptive geometry. The projection is called orthographic if the rays are perpendicular (orthogonal) to the image plane, and oblique or skew if they are not.

<span class="mw-page-title-main">Exploded-view drawing</span> Type of technical diagram

An exploded-view drawing is a diagram, picture, schematic or technical drawing of an object, that shows the relationship or order of assembly of various parts.

<span class="mw-page-title-main">Plan (drawing)</span>

Plans are a set of drawings or two-dimensional diagrams used to describe a place or object, or to communicate building or fabrication instructions. Usually plans are drawn or printed on paper, but they can take the form of a digital file.

<span class="mw-page-title-main">Claris CAD</span>

Claris CAD was a two-dimensional computer-aided design program for Apple Inc. Macintosh.

<span class="mw-page-title-main">Drafter</span> Person who makes technical drawings

A drafter is an engineering technician who makes detailed technical drawings or plans for machinery, buildings, electronics, infrastructure, sections, etc. Drafters use computer software and manual sketches to convert the designs, plans, and layouts of engineers and architects into a set of technical drawings. Drafters operate as the supporting developers and sketch engineering designs and drawings from preliminary design concepts.

<span class="mw-page-title-main">Multiview orthographic projection</span>

In technical drawing and computer graphics, a multiview projection is a technique of illustration by which a standardized series of orthographic two-dimensional pictures are constructed to represent the form of a three-dimensional object. Up to six pictures of an object are produced, with each projection plane parallel to one of the coordinate axes of the object. The views are positioned relative to each other according to either of two schemes: first-angle or third-angle projection. In each, the appearances of views may be thought of as being projected onto planes that form a six-sided box around the object. Although six different sides can be drawn, usually three views of a drawing give enough information to make a three-dimensional object.

<span class="mw-page-title-main">Architectural drawing</span> Technical drawing of a building (or building project)

An architectural drawing or architect's drawing is a technical drawing of a building that falls within the definition of architecture. Architectural drawings are used by architects and others for a number of purposes: to develop a design idea into a coherent proposal, to communicate ideas and concepts, to convince clients of the merits of a design, to assist a building contractor to construct it based on design intent, as a record of the design and planned development, or to make a record of a building that already exists.

ISO 128 is an international standard (ISO), about the general principles of presentation in technical drawings, specifically the graphical representation of objects on technical drawings.

<span class="mw-page-title-main">Mechanical systems drawing</span>

Mechanical systems drawing is a type of technical drawing that shows information about heating, ventilating, air conditioning and transportation around the building. It is a powerful tool that helps analyze complex systems. These drawings are often a set of detailed drawings used for construction projects; it is a requirement for all HVAC work. They are based on the floor and reflected ceiling plans of the architect. After the mechanical drawings are complete, they become part of the construction drawings, which is then used to apply for a building permit. They are also used to determine the price of the project.

<span class="mw-page-title-main">Axonometry</span> The process of projecting a three-dimensional object onto a two-dimmensional plane

Axonometry is a graphical procedure belonging to descriptive geometry that generates a planar image of a three-dimensional object. The term "axonometry" means "to measure along axes", and indicates that the dimensions and scaling of the coordinate axes play a crucial role. The result of an axonometric procedure is a uniformly-scaled parallel projection of the object. In general, the resulting parallel projection is oblique ; but in special cases the result is orthographic, which in this context is called an orthogonal axonometry.

References

  1. 1 2 Goetsch, David L.; Chalk, William S.; Nelson, John A. (2000). Technical Drawing. Delmar Technical Graphics Series (Fourth ed.). Albany: Delmar Learning. p. 3. ISBN   978-0-7668-0531-6. OCLC   39756434.
  2. 1 2 Richard Boland and Fred Collopy (2004). Managing as designing. Stanford University Press, 2004. ISBN   0-8047-4674-5, p.69.
  3. Bhatt, N.D. Machine Drawing. Charotar Publication.
  4. Jefferis, Alan; Madsen, David (2005), Architectural Drafting and Design (5th ed.), Clifton Park, NY: Delmar Cengage Learning, ISBN   1-4018-6715-4
  5. Goetsch et al. (2000) p. 792
  6. Lieu, Dennis K; Sorby, Sheryl (2009), Visualization, Modeling, and Graphics for Engineering Design (1st ed.), Clifton Park, NY: Delmar Cengage Learning, ISBN   978-1-4018-4249-9, pp. 1–2
  7. 1 2 Baltes, Sebastian; Diehl, Stephan (11 November 2014). "Sketches and diagrams in practice". Proceedings of the 22nd ACM SIGSOFT International Symposium on Foundations of Software Engineering. FSE 2014. Hong Kong, China: Association for Computing Machinery. pp. 530–541. arXiv: 1706.09172 . doi:10.1145/2635868.2635891. ISBN   978-1-4503-3056-5. S2CID   2436333.
  8. 1 2 Cherubini, Mauro; Venolia, Gina; DeLine, Rob; Ko, Amy J. (29 April 2007), "Let's go to the whiteboard: How and why software developers use drawings", Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, New York, NY, US: Association for Computing Machinery, pp. 557–566, doi:10.1145/1240624.1240714, ISBN   978-1-59593-593-9, S2CID   6604218 , retrieved 8 September 2021
  9. 1 2 Ivan Viola and Meister E. Gröller (2005). "Smart Visibility in Visualization". In: Computational Aesthetics in Graphics, Visualization and Imaging. L. Neumann et al. (Ed.)
  10. "The Role of the Technical Illustrator in Industry". industriegrafik.com. 15 June 2002. Archived from the original on 14 August 2009. Retrieved 15 February 2009.
  11. Diepstraten, J.; Weiskopf, D.; Ertl, T. (2003). "Interactive Cutaway Illustrations" (PDF). vis.uni-stuttgart.de. Archived from the original (PDF) on 16 December 2005. in Brunet, P.; Fellner, D. (eds.). "Eurographics 2003". Eurographics. The Eurographics Association and Blackwell Publishers. 22 (3).
  12. Goetsch et al. (2000), p. 341
  13. 1 2 3 "General Information Concerning Patents § 1.84 Standards for drawings". USPTO.gov . January 2005. Archived from the original on 30 January 2009. Retrieved 13 February 2009.
  14. Michael E. Brumbach, Jeffrey A. Clade (2003). Industrial Maintenance. Cengage Learning, 2003 ISBN   0-7668-2695-3, p.65
  15. Ralph W. Liebing (1999). Architectural working drawings. John Wiley and Sons, 1999. ISBN   0-471-34876-7.
  16. Goetsch et al. (2000), p. 613
  17. "as-built drawings". BusinessDictionary.com. 26 December 2017. Archived from the original on 3 December 2017. Retrieved 1 January 2018.

Further reading