The Types of Engineering Drawings
Some organisations, like NASA, have a knowledgeable and experienced engineering team who must adhere to strict engineering standards, including those that apply to engineering drawing.
Whether it is a bridge, a space shuttle or a washing machine, the device or structure was first an idea and an engineer developed engineering drawings to help that idea become a reality. The function, complexity and type of creation all relate to different types of engineering drawings.
Assembly drawings depict how two or more components join together by showing the components in a variety of angles. Assembly drawings must use orthographic projection of views and show the components in a manner that represents true dimensions, preventing the possibility of perspective skewing the understanding of the drawing.
Assembly drawings include a list of the required parts and may also incorporate a list of required materials and supplies to complete assembly. Roy Mech, a website based out of the United Kingdom, explains the standards for assembly drawings and states that "separate items will be identified with leader lines to balloons which include the item reference number linking to the parts list." The same drawing style is present in NASA's "Engineering Drawn Standards Manual."
According to NASA, a detail drawing is a type of engineering drawing that "shows all the information necessary for fabricating an item, including the material from which it is made and those finishes, protective coatings, and processes required to fabricate the end product."
This style of engineering drawing focuses on detail and, because of this, each drawing depicts only one component of the overall structure. A drawing of this scale may be quite large and require more than one sheet of paper.
Detail drawings may not be necessary when components of the larger structure already exist and consist of proprietary designs. In these instances, designers may request technical data from the item manufacturer.
According to NASA, modification drawings illustrate changes to an already created engineering drawing. Engineers may create these drawings to alter the structure to better suit its usage or because of safety regulations of the government. All modification drawings originate from an existing engineering drawing and illustrate precise changes to the process or product.
The type of drawing is recognisable because it displays the words "Modification Drawing" above the title block on the page. NASA also defines this style of engineering drawing as a "Make From Drawing."
NASA defines a matched-set engineering drawing as one that depicts two or more components that, because of their nature, both require replacement when either component becomes faulty or unusable. These drawings are a type of assembly drawing. They show the matching characteristics of the components involved.
Matched or mated components in an engineering drawing display serial numbers to indicate their matched status. The drawings themselves display the text "Maintain and Furnish Only As A Matched Set" to differentiate matched-set drawings for other assembly drawings.
Fabrication drawings are a subcategory of detail drawings. These mechanical engineering drawings portray the fabrication of an item or component and may be an assembly drawing. Fabrication drawings include instructions for welding components together, when applicable. This type of drawing includes a list of all items and supplies required to complete the fabrication. Items in the list
According to Roy Mech, a "fabrication drawing sometimes only includes the fabrication details," while the final machining details are shown on a separate drawing. Unlike an assembly drawing, the fabrication drawing does not indicate components that can later be disassembled.