page_title: Technical drawing
section_title: Computer aided design
hierarchical_section_title: Technical drawing / Methods / Computer aided design
caption_attribution_description: English: Solid model assembly created in en:NX (Unigraphics).
context_page_description: Technical drawing, drafting or drawing, is the act and discipline of composing drawings that visually communicate how something functions or is constructed.
  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.
  A drafter, draftsperson, or draughtsman is a person who makes a drawing. A professional drafter who makes technical drawings is sometimes called a drafting technician.
context_section_description: 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 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.
  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 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 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.
caption: View of a CAD model of a four-cylinder inline crankshaft with pistons
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