Engineering drawing
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. These drawings are linked together by a "master drawing." This "master drawing" is more commonly known as an assembly drawing. The assembly drawing 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.
The process of producing engineering drawings is often referred to as technical drawing or drafting. Drawings typically contain multiple views of a component, although additional scratch views may be added of details for further explanation. Only the information that is a requirement is typically specified. Key information such as dimensions is usually only specified in one place on a drawing, avoiding redundancy and the possibility of inconsistency. Suitable tolerances are given for critical dimensions to allow the component to be manufactured and function. More detailed production drawings may be produced based on the information given in an engineering drawing. Drawings have an information box or title block containing who drew the drawing, who approved it, units of dimensions, meaning of views, the title of the drawing and the drawing number.
History
As a necessary means for visually conveying ideas, technical drawing has been in one form or another a part of human history since antiquity. The use of these early drawings was to express architectural and engineering concepts for large cultural structures: the temples, monuments, and public infrastructure. Basic forms of technical drawing were used by the Egyptians and Mesopotamians to create highly detailed irrigation systems, pyramids, and other such sophisticated structures. But their methods were, comparatively easy, yet needed a great deal of skill and accuracy. Even in their primitive form, they gave the construction a drawing for structures that would stand the test of time.The discipline of technical drawing has further evolved in ancient Greece and ancient Rome. Vitruvius and other engineers and architects used drawings as a medium for the transmission of construction techniques, and the illustration of the basic principles of balance and proportion in architecture. Early examples of what would lead to more formal technical drawing practices included the drawings and geometric calculations used to construct aqueducts, bridges, and fortresses. Technical drawings also figured in the 12th-century design of cathedrals and castles, albeit such drawings were more typically produced by artisans and stonemasons, not formally trained engineers.
The Renaissance was a period of great success for technical drawing. These inventive artists and inventors were starting to use sophisticated methods of visual representation within their work as well as a methodical adherence to accuracy. His notebooks contained drawings of mechanical devices anatomical studies, and engineering projects that demonstrated his advanced understanding of form, function, and proportion, as elucidated by his notebooks. Perhaps he was the first of the pioneers who combined the arts with engineering ability to produce technical drawings at once imaginative and instructive. It was an important foundation for future developments in technical drawing work.
As the Industrial Revolution took hold, modern engineering drawing took shape with the emergence of strictly specified conventions like drawing in orthographic projection, exploding, and standard scales. Part of the movement towards standardization was somewhat triggered by the development of engineering education and uniform drawing techniques in France. During the same period, the French mathematician Gaspard Monge developed descriptive geometry, a means of representing three-dimensional objects in two-dimensional space, and contributed to technical drawing in a major way. His work set the ground for orthographic projection which is one of the core techniques to be used in technical drawing today. Monge's methods were disseminated initially as a military secret, then far and wide, and his methods shaped the future of engineering education, and also the engineering practice.
Further contributions to the craft of technical drawing were made by pioneers like Marc Isambard Brunel. L. T. C. Rolt's biography of Isambard Kingdom Brunel, to whom Marc contributed in 1799 with his detailed drawings of block-making machinery, testified to the developing nature of British engineering methods. By applying what we now call mechanical drawing techniques to depict three-dimensional machinery on a two-dimensional plane more efficient manufacturing processes as well as greater precision were enabled. These innovations were essential as the world began to move toward mechanized production, and complex engineering projects, such as bridges, railways, and ships, required highly detailed and accurate technical representations to succeed.
This increasing need for a degree of precision in technical drawings during the 19th century was a direct result of the Industrial Revolution. In this era, we have seen the development of large-scale engineering projects such as railways, steam engines, and iron structures which require a heightened degree of accuracy and standardization. New conventions and symbols were created by engineers; the use of which became standardized throughout industries, so that any person who could read a technical drawing could know the specifications of a component or structure. The standardization process helped engineer practices to become standardized, making it easier for engineers, manufacturers, and builders to work together.
In the 20th century, technical drawing underwent yet another transformation with the introduction of drafting tools such as the T-square, compasses, and protractors. These tools helped drafters achieve the high degree of precision necessary for increasingly complex projects, such as skyscrapers, airplanes, and automobiles. The establishment of standards such as the American National Standards Institute and International Organization for Standardization further formalized technical drawing conventions, ensuring consistency in engineering practices around the world.
Today, technical drawing has largely transitioned from manual drafting to computer-aided design. CAD software has revolutionized the way technical drawings are created, allowing for faster, more precise, and easily modifiable drawings. Engineers can now visualize designs in three dimensions, simulate performance, and make adjustments before any physical prototype is built. This digital transformation has not only increased efficiency but also broadened the possibilities for innovation, enabling engineers to tackle challenges that were previously unimaginable.
However, despite the advent of digital tools, the fundamental principles of technical drawing remain rooted in its history. Precision, clarity, and the ability to convey complex information visually are still at the core of technical drawing. The conventions established over centuries—from orthographic projection to the use of scale and dimension lines—continue to be essential in modern engineering and architectural practice. The evolution of technical drawing is a testament to human ingenuity, demonstrating how the ability to convey complex ideas visually has been pivotal in the advancement of civilization.
Standardization and disambiguation
Engineering drawings specify the requirements of a component or assembly which can be complicated. Standards provide rules for their specification and interpretation. Standardization also aids internationalization, because people from different countries who speak different languages can read the same engineering drawing, and interpret it the same way.One major set of engineering drawing standards is ASME Y14.5 and Y14.5M. These apply widely in the United States, although is now also important. In 2018, ASME AED-1 was created to develop advanced practices unique to aerospace and other industries and supplement to Y14.5 Standards.
In 2011, a new revision of was published containing the Invocation Principle. This states that, "Once a portion of the ISO geometric product specification system is invoked in a mechanical engineering product documentation, the entire ISO GPS system is invoked." It also goes on to state that marking a drawing "Tolerancing ISO 8015" is optional. The implication of this is that any drawing using ISO symbols can only be interpreted to ISO GPS rules. The only way not to invoke the ISO GPS system is to invoke a national or other standard. Britain, BS 8888 has undergone important updates in the 2010s.
Media
For centuries, until the 1970s, all engineering drawing was done manually by using pencil and pen on paper or other substrate. Since the advent of computer-aided design, engineering drawing has been done more and more in the electronic medium with each passing decade. Today most engineering drawing is done with CAD, but pencil and paper have not entirely disappeared.Some of the tools of manual drafting include pencils, pens and their ink, straightedges, T-squares, French curves, triangles, rulers, protractors, dividers, compasses, scales, erasers, and tacks or push pins. And of course the tools also include drawing boards or tables. The English idiom "to go back to the drawing board", which is a figurative phrase meaning to rethink something altogether, was inspired by the literal act of discovering design errors during production and returning to a drawing board to revise the engineering drawing. Drafting machines are devices that aid manual drafting by combining drawing boards, straightedges, pantographs, and other tools into one integrated drawing environment. CAD provides their virtual equivalents.
Producing drawings usually involves creating an original that is then reproduced, generating multiple copies to be distributed to the shop floor, vendors, company archives, and so on. The classic reproduction methods involved blue and white appearances, which is why engineering drawings were long called, and even today are still often called, "blueprints" or "bluelines", even though those terms are anachronistic from a literal perspective, since most copies of engineering drawings today are made by more modern methods that yield black or multicolour lines on white paper. The more generic term "print" is now in common usage in the US to mean any paper copy of an engineering drawing. In the case of CAD drawings, the original is the CAD file, and the printouts of that file are the "prints".