The term drawings refers to the depiction of details, assemblies, installations, or other types of graphical representations. Drafters, checkers, and other reviewers are responsible for the completeness, clarity, accuracy, conformance to standards, and functional appropriateness of engineering drawings.
Some examples of the types of qualities that need to be considered in the preparation and review of drawings are expansion, interchangeability , material, protective finish, service, strength, and tolerances.
Abbreviation used in drawings and drawing standards should conform to the drawing standards of the country or company. Among other drawing consideration are dimensions, geometric surface relationship, scale, tolerances, and symmetrical opposite parts.
Fabrication considerations include adhesives, casting, economy, machining lugs, processing clearance, puller feature, and torque value.
Functional drafting must aim to provide information in an economical manner. Drawing short cut are very useful but should be carefully evaluated before they are applied. The same principle applies to procedural shortcuts, which include streamlining approval requirements and using standard parts and design-standard information, and training program.
Other ways of controlling the cost of the project are to use detail assembly drawings (with care, however, because they can become complicated and confusing), to use simplified representations in drawings, and to use reproduction shortcuts and photodrawings.
A working drawing supplies information and instructions for the manufacture or construction of machines or structures. The two types of working drawings are the detail draining and the assembly drawing.
The detail drawing should include the shape description, size description, and specifications, along with the drawing number, scale method of projection, date, name of part, and drafter's name.
A typical drawing checklist will cover the following: dimensions, scale, tolerances, standards, surface texture, and material.
A detailer must understand materials, shop processes, and operations, and must also know how a part functions.
Multiple detail drawings are group on a large sheets, sometime according to the department in which the marts are made.
A clear record must be kept of drawing revisions; this record must be registered on the drawing in the form of change or revision table.
A drawing showing a product in its completed state is called an assembly drawing. Types of assembly drawings are design assembly drawings, installation assembly drawings, and assembly drawings for catalogs. An item list ( also call bill of material, or BOM) is an itemized list of all components shown on an assembly drawing or detail drawing.
Exploded assembly drawing are provided when people who are unskilled in reading engineering drawings are likely to be the users of the drawings; for example, exploded assembly drawings are use in the appliance repair industry.
Detail assembly drawings are often made for simple objects such as furniture, that have few parts and are not intricate in shape. In these drawings, all dimensions and information needed to construct and assemble the parts are given directly on the assembly drawing.
Subassembly drawings involve completely assembled components and individual parts.
Source : Engineering Drawing and Design ( Cecil Jensen et al.)