Technical drawing, also known as
drafting or
draughting, is the act and
disciplineAn academic discipline, or field of study, is a branch of knowledge that is taught and researched at the college or university level. Disciplines are defined , and recognized by the academic journals in which research is published, and the learned societies and academic departments or faculties to...
of composing plans that
visually communicateVisual communication as the name suggests is communication through visual aid and is described as the conveyance of ideas and information in forms that can be read or looked upon...
how something functions or has to be constructed.
Drafting is the language of industry.
A
drafter,
draftsperson, or
draughtsman is a person who makes a
drawingDrawing is a form of visual art that makes use of any number of drawing instruments to mark a two-dimensional medium. Common instruments include graphite pencils, pen and ink, inked brushes, wax color pencils, crayons, charcoal, chalk, pastels, markers, styluses, and various metals .An artist who...
(technical or otherwise). A professional drafter who makes technical drawings is sometimes called a
drafting technician.
People who communicate with technical drawings, (those who design and those who are tradespeople), may use technical standards that define practical symbols,
perspectivesPerspective in the graphic arts, such as drawing, is an approximate representation, on a flat surface , of an image as it is seen by the eye...
,
units of measurementA unit of measurement is a definite magnitude of a physical quantity, defined and adopted by convention and/or by law, that is used as a standard for measurement of the same physical quantity. Any other value of the physical quantity can be expressed as a simple multiple of the unit of...
, notation systems, visual styles, or layout conventions. These enable a drafter to communicate more concisely by using a commonly-understood
conventionA convention is a set of agreed, stipulated or generally accepted standards, norms, social norms or criteria, often taking the form of a custom....
. Together, such conventions constitute a
visual languageA visual language is a system of communication using visual elements. Speech as a means of communication cannot strictly be separated from the whole of human communicative activity which includes the visual and the term 'language' in relation to vision is an extension of its use to describe the...
, 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 artsThe visual arts are art forms that create works which are primarily visual in nature, such as ceramics, drawing, painting, sculpture, printmaking, design, crafts, and often modern visual arts and architecture...
. Artistic drawings are subjectively interpreted; their meanings are multiply determined. Technical drawings are understood to have one intended meaning.
Methods
Sketching
A
sketchA sketch is a rapidly executed freehand drawing that is not usually intended as a finished work...
is a quickly executed freehand drawing that is 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 undertaking a more finished work, especially when the finished work is expensive and time consuming.
Architectural sketches, for example, are a kind of
diagramA diagram is a two-dimensional geometric symbolic representation of information according to some visualization technique. Sometimes, the technique uses a three-dimensional visualization which is then projected onto the two-dimensional surface...
s. These sketches, like
metaphorA metaphor is a literary figure of speech that uses an image, story or tangible thing to represent a less tangible thing or some intangible quality or idea; e.g., "Her eyes were glistening jewels." Metaphor may also be used for any rhetorical figures of speech that achieve their effects via...
s, 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.
Manual or by instrument
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 boardA drawing board is, in its antique form, a kind of multipurpose desk which can be used for any kind of drawing, writing or impromptu sketching on a large sheet of paper or for reading a large format book or other oversized document or for drafting precise technical illustrations...
. A sliding
straightedgeA straightedge is a tool with an edge free from curves, or straight, used for transcribing straight lines, or checking the straightness of lines...
known as a
T-squareA T-square is a technical drawing instrument used by draftsmen primarily as a guide for drawing horizontal lines on a drafting table. It may also guide a triangle to draw vertical or diagonal lines. Its name comes from the general shape of the instrument where the horizontal member of the T slides...
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 penA technical pen is a specialized instrument used by an engineer, architect, or drafter to make lines of constant width for architectural, engineering, or technical drawings. It has been also generally called "rapidograph", although that particular name is officially a trademarked line of products...
along the T-square's edge, but more typically the T-square is used as a tool to hold other devices such as
set squareA set square or triangle is an object used in engineering and technical drawing, with the aim of providing a straightedge at a right angle or other particular planar angle to a baseline....
s 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 machineA drafting machine is a very useful tool in technical drawing, consisting of a pair of scales mounted to form a right angle on an articulated protractor head that allows an angular rotation....
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.
In addition, the drafter uses several tools to draw curves and circles. Primary among these are the
compassesA compass or pair of compasses is a technical drawing instrument that can be used for inscribing circles or arcs. As dividers, they can also be used as a tool to measure distances, in particular on maps...
, used for drawing simple arcs and circles, and the
French curveA French curve is a template made out of metal, wood or plastic composed of many different curves. It is used in manual drafting to draw smooth curves of varying radii....
, typically a piece of plastic with complex curves on it. A
splineA spline or the more modern term flexible curve consists of a long strip fixed in position at a number of points that relaxes to form and hold a smooth curve passing through those points for the purpose of transferring that curve to another material....
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
stagecraftStagecraft is a generic term referring to the technical aspects of theatrical, film, and video production. It includes, but is not limited to, constructing and rigging scenery, hanging and focusing of lighting, design and procurement of costumes, makeup, procurement of props, stage management, and...
, 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
pantographA pantograph is a mechanical linkage connected in a special manner based on parallelograms so that the movement of one pen, in tracing an image, produces identical movements in a second pen...
(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
machinistA machinist is a person who uses machine tools to make or modify parts, primarily metal parts, a process known as machining. This is accomplished by using machine tools to cut away excess material much as a woodcarver cuts away excess wood to produce his work. In addition to metal, the parts may...
—skilled drafters (and/or designers) usually accomplish the task and are always in demand to some level.
Computer aided design
Today, the mechanics of the drafting task have largely been automated and accelerated through the use of
computer-aided designComputer-aided design , also known as computer-aided design and drafting , is the use of computer technology for the process of design and design-documentation. Computer Aided Drafting describes the process of drafting with a computer...
systems (CAD).
There are two types of computer-aided design systems used for the production
of technical drawings"
two dimensions2D computer graphics is the computer-based generation of digital images—mostly from two-dimensional models and by techniques specific to them...
("2D") and
three dimensions3D computer graphics are graphics that use a three-dimensional representation of geometric data that is stored in the computer for the purposes of performing calculations and rendering 2D images...
("3D").
2D CAD systems such as
AutoCADAutoCAD is a software application for computer-aided design and drafting in both 2D and 3D. It is developed and sold by Autodesk, Inc. First released in December 1982, AutoCAD was one of the first CAD programs to run on personal computers, notably the IBM PC...
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 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 InventorAutodesk Inventor, developed by U.S.-based software company Autodesk, is 3D mechanical solid modeling design software for creating 3D digital prototypes used in the design, visualization and simulation of products...
or
SolidWorksSolidWorks is a 3D mechanical CAD program that runs on Microsoft Windows and is being developed by Dassault Systèmes SolidWorks Corp., a subsidiary of Dassault Systèmes, S. A. . SolidWorks is currently used by over 1.3 million engineers and designers at more than 130,000 companies worldwide...
first produce the geometry of the part, the technical drawing comes from user 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; electrical, electronic, pneumatic, hydraulic, 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 dimensions2D computer graphics is the computer-based generation of digital images—mostly from two-dimensional models and by techniques specific to them...
("2D") and
three dimensions3D computer graphics are graphics that use a three-dimensional representation of geometric data that is stored in the computer for the purposes of performing calculations and rendering 2D images...
("3D") although the representation itself is always created in 2D (cf.
Architectural modelAn architectural model is a type of a scale model, tangible representation of a structure built to study aspects of an architectural design or to communicate design ideas to clients, committees, and the general public...
). Drafting is the integral communication of technical or engineering drawings and is the
industrial artsIndustrial Arts is an umbrella term originally conceived in the late 19th century to describe educational programs which featured fabrication of objects in wood and/or metal using a variety of hand, power, or machine tools...
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.
Architecture
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. Architectural drawings describe and document an architect's design.
Engineering
Engineering can be a very broad term. It stems from the Latin
ingenerare, meaning "to create". 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
typefaceIn typography, a typeface is the artistic representation or interpretation of characters; it is the way the type looks. Each type is designed and there are thousands of different typefaces in existence, with new ones being developed constantly....
s 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.
Related fields
Technical illustrations
Technical illustrationTechnical Illustration is the use of illustration to visually communicate information of a technical nature. Technical illustrations can be components of technical drawings or diagrams...
is the use of
illustrationAn illustration is a displayed visualization form presented as a drawing, painting, photograph or other work of art that is created to elucidate or dictate sensual information by providing a visual representation graphically.- Early history :The earliest forms of illustration were prehistoric...
to visually communicate information of a technical nature. Technical illustrations can be component technical drawings or
diagramA diagram is a two-dimensional geometric symbolic representation of information according to some visualization technique. Sometimes, the technique uses a three-dimensional visualization which is then projected onto the two-dimensional surface...
s. The aim of technical illustration is "to generate expressive
imageAn image is an artifact, for example a two-dimensional picture, that has a similar appearance to some subject—usually a physical object or a person.-Characteristics:...
s that effectively convey certain
informationInformation in its most restricted technical sense is a message or collection of messages that consists of an ordered sequence of symbols, or it is the meaning that can be interpreted from such a message or collection of messages. Information can be recorded or transmitted. It can be recorded as...
via the visual channel to the human observer".
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".
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".
A cutaway drawing is a technical illustration, in which
surfaceIn mathematics, specifically in topology, a surface is a two-dimensional topological manifold. The most familiar examples are those that arise as the boundaries of solid objects in ordinary three-dimensional Euclidean space R3 — for example, the surface of a ball...
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".
Types of technical drawings
The two types of technical drawings are based on
graphical projectionGraphical projection is a protocol by which an image of a three-dimensional object is projected onto a planar surface without the aid of mathematical calculation, used in technical drawing.- Overview :...
. 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 projectionOrthographic projection is a means of representing a three-dimensional object in two dimensions. It is a form of parallel projection, where 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...
to create an image where only two of the three dimensions of the object are seen.
Three-dimensional representation
In three-dimensional representation, also referred to as pictorials, all three dimensions, of the three dimensions of an object, are visible.
Multiview
Multiview is a type of
orthographic projectionOrthographic projection is a means of representing a three-dimensional object in two dimensions. It is a form of parallel projection, where 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...
. 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.
Exploded
An exploded view drawing is a technical drawing of an object that shows the relationship or order of
assemblyManufacturing is the use of machines, tools and labor to produce goods for use or sale. The term may refer to a range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale...
of the various parts. It shows the components of an object slightly separated by distance, or suspended in surrounding space in the case of a three-
dimensionIn physics and mathematics, the dimension of a space or object is informally defined as the minimum number of coordinates needed to specify any point within it. Thus a line has a dimension of one because only one coordinate is needed to specify a point on it...
al exploded diagram. An object is represented as if there had been a small controlled
explosionAn explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. An explosion creates a shock wave. If the shock wave is a supersonic detonation, then the source of the blast is called a "high explosive"...
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 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.
Basic drafting paper sizes
There have been many standard sizes of
paperPaper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....
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.
Patents
The applicant for a
patentA patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....
will be required by
lawLaw is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...
to furnish a
drawingDrawing is a form of visual art that makes use of any number of drawing instruments to mark a two-dimensional medium. Common instruments include graphite pencils, pen and ink, inked brushes, wax color pencils, crayons, charcoal, chalk, pastels, markers, styluses, and various metals .An artist who...
of the
inventionAn invention is a novel composition, device, or process. An invention may be derived from a pre-existing model or idea, or it could be independently conceived, in which case it may be a radical breakthrough. In addition, there is cultural invention, which is an innovative set of useful social...
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
compositionComposition may refer to:* Composition , in which one assumes that a whole has a property solely because its various parts have that property* Compounding is also known as composition in linguistic literature* in computer science...
s of matter or
processIndustrial processes are procedures involving chemical or mechanical steps to aid in the manufacture of an item or items, usually carried out on a very large scale. Industrial processes are the key components of heavy industry....
es, but a drawing may also be useful in the case of many processes.
The drawing must show every feature of the invention specified in the claims, and is required by the
patent officeA patent office is a governmental or intergovernmental organization which controls the issue of patents. In other words, "patent offices are government bodies that may grant a patent or reject the patent application based on whether or not the application fulfils the requirements for...
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.
Working drawings
Working drawingA working drawing is a type of technical drawing, which is part of the documentation needed to build an engineering product or architecture. Typically in architecture these could include civil drawings, architectural drawings, structural drawings, mechanical drawings, electrical drawings, and...
s are the set of technical drawings used during the manufacturing phase of a product. In architecture, these typically include
civil drawingA civil drawing, or site drawing, is a type of technical drawing that shows information about grading, landscaping, or other site details....
s,
architectural drawingAn architectural drawing or architect's drawing is a technical drawing of a building that falls within the definition of architecture...
s,
structural drawingA structural drawing, a type of technical drawing, shows information about architectural foundations, roof, or other structural details....
s,
mechanical systems drawingMechanical systems drawing is a type of technical drawing that shows information about heating, ventilating, and air conditioning; it is a powerful tool that helps analyze a complex system. These drawings are often a set of detailed drawings used for construction projects; it is a requirement for...
s,
electrical drawingAn electrical drawing, is a type of technical drawing that shows information about power, lighting, and communication for an engineering or architectural project...
s, and
plumbing drawingA plumbing drawing, a type of technical drawing, shows the system of piping for fresh water going into the building and waste going out, both solid and liquid.- See also :* Architectural drawing* Electrical drawing* Engineering drawing...
s.
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.
See also
- Architectural drawing
An architectural drawing or architect's drawing is a technical drawing of a building that falls within the definition of architecture...
- Engineering drawing
An engineering drawing, a type of technical drawing, is used to fully and clearly define requirements for engineered items.Engineering drawing produces engineering drawings . More than just the drawing of pictures, it is also a language—a graphical language that communicates ideas and information...
- ISO 128
ISO 128 is an international standard , about the general principles of presentation in technical drawings, more specific the graphical representation of objects on technical drawings.- Overview :...
Technical drawings—General principles of presentation
- Linear scale
A linear scale, also called a bar scale, scale bar, graphic scale, or graphical scale, is a means of visually showing the scale of a map, nautical chart, engineering drawing, or architectural drawing....
- Plan (drawing)
- Shop drawing
A is a drawing or set of drawings produced by the contractor, supplier, manufacturer, subcontractor, or fabricator. Shop drawings are typically required for pre-fabricated components. Examples of these include: elevators, structural steel, trusses, pre-cast, windows, appliances, cabinets, air...
- Technical communication
Technical communication is a method of researching and creating information about technical processes or products directed to an audience through media. The information must be relevant to the intended audience. Technical communicators often work collaboratively to create products for various...
- 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...
- Specification (technical standard)
A specification is an explicit set of requirements to be satisfied by a material, product, or service. Should a material, product or service fail to meet one or more of the applicable specifications, it may be referred to as being out of specification;the abbreviation OOS may also be used...
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
External links