Mechanical design is a rigorous and highly practical profession. As engineering language in the field of engineering design, engineering drawings need to meet the essential requirements of clear and complete expression. At the same time, the readers of the drawings are also required to fully comprehend and understand them. So, how can we achieve clear reading of engineering drawings?
In this blog, we will talk about engineering drawings, exploring its various types, standardization, symbols and components.
What is a Engineering Drawing?
An engineering drawing is a subcategory of technical drawing that is used to convey information about an object including shape, structure, dimensions, tolerances, accuracy and other requirements needed to manufacture a product.
Types of Engineering Drawings
Assembly drawings illustrate how multiple components fit together to form a complete product or system. They showcase the relationships between parts, their spatial arrangement, and assembly sequences. These drawings provide crucial insights into the overall design and help ensure proper fit and functionality.
Schematic Diagrams Drawing:
Schematic diagrams present a simplified representation of a system or process using symbols, lines, and labels. They focus on conveying the functional relationships and connections between components without detailing their physical appearance. Schematic diagrams are commonly used in electrical, electronic, and hydraulic systems.
Principle Diagrams Drawing:
Principle diagrams, also known as block diagrams, provide a high-level overview of a complex system by breaking it down into interconnected blocks or modules. These diagrams emphasize the flow of signals, energy, or information between major components, aiding in understanding the system’s fundamental structure and interactions.
Part drawings, also referred to as detailed drawings, depict individual components in great detail. They include precise dimensions, tolerances, material specifications, surface finishes, and manufacturing notes. Part drawings serve as the basis for production, guiding machinists and manufacturers in creating accurate and functional parts.
Main Components of an Engineering Drawing
A title block is a designated area located on an engineering drawing, typically in the lower right-hand corner, that contains crucial administrative and descriptive information. This information includes:
- Title and Drawing Number: The title indicates the nature of the drawing, while the drawing number uniquely identifies it within a project or organization.
- Revision Information: Details any revisions or changes made to the drawing, including revision letters, dates, and descriptions.
- Author and Approvals: Names of the drafter, checker, and approving personnel involved in the drawing’s creation and review.
- Date: The date when the drawing was created, revised, or approved.
- Scale: Indicates the scale at which the drawing was created and the relationship between the drawing and the actual size of the object.
- Units: Specifies the measurement units used in the drawing, such as inches, millimeters, or meters.
- Company Information: Includes the name, logo, and contact information of the organization responsible for the drawing.
The border of an engineering drawing encompasses the entire drawing area and is used to provide additional context and references. It contains information like:
- Project Information: Identifies the project or product the drawing pertains to, often including project names, codes, or descriptions.
- Sheet Information: Indicates the sheet number within the set of drawings, total number of sheets, and any cross-references to related sheets.
- Drawing Notes and Instructions: Provides any specific notes, instructions, or disclaimers relevant to the drawing.
- Material and Finish Specifications: Lists the materials used in the design and any required surface finishes or coatings.
- Geometric Tolerances: Presents tolerances and dimensional specifications that ensure the accuracy and quality of the design.
- Bill of Materials (BOM): May include a summarized list of parts and components shown on the drawing.
- Orthographic Views: These views present the object as a series of two-dimensional projections from different viewpoints. They include front, top, right-side, left-side, bottom, and rear views. Orthographic views provide a complete picture of the object’s dimensions and proportions.
Regionally, the views are a little different. Compare the US and ISO layouts by taking a look at this image. Drawing layouts in ISO and the United States are in direct opposition to one another. The one on the left is known as a first-angle projection, on the right is known as third-angle projection
- Isometric Views: Isometric views represent the object in a three-dimensional perspective, where all three axes are equally foreshortened. They provide a more intuitive understanding of the object’s shape and spatial relationships.
- Sectional Views: Sectional views show a cutaway portion of the object, revealing its internal features. These views are essential for conveying details that may not be visible in standard views.
- Detail Views: Detail views focus on a specific area or feature of the object, providing an enlarged and magnified view for accurate representation and dimensioning.
- Auxiliary Views: Auxiliary views are used to display inclined or non-orthogonal surfaces that cannot be accurately represented in standard views. They provide a true shape and size depiction of these surfaces.
Dimensioning and Tolerancing:
Engineering drawings include various types of dimensions to convey different aspects of the object. These include:
- Linear Dimensions: Represent the lengths of edges, lines, or distances between features. Linear dimensions are commonly expressed in units like millimeters, inches, or centimeters.
- Angular Dimensions: Specify the angle between two lines or surfaces. Angular dimensions are denoted in degrees, minutes, and seconds.
- Radial Dimensions: Indicate the radius of circular features, such as holes or fillets. Radial dimensions are essential for ensuring proper fit and clearance.
- Diametric Dimensions: Convey the diameter of circular features, typically for holes or cylinders.
- Ordinate Dimensions: Reference a common baseline or origin point to specify the locations of features. This method is particularly useful for complex shapes.
Tolerances define the acceptable range of variation for dimensions, ensuring that parts fit together and function as intended. Types of tolerances include:
- Unilateral Tolerance: Specifies a limit in one direction from the nominal dimension.
- Bilateral Tolerance: Specifies limits in both directions from the nominal dimension.
- Limit Dimensioning: Provides both the upper and lower limits for a dimension.
- Geometric Dimensioning and Tolerancing (GD&T): A system of symbols and annotations that communicate more complex tolerances and relationships between features.
GD&T Symbols serve as a concise and universally understood means of conveying information on engineering drawings. Some common categories of symbols include:
|Straightness – a condition where a surface element or axis is a straight line.|
|Flatness – a condition where a surface has all elements lying in a single plane.|
|Roundness – describes a condition where the surface of a revolution (cylinder, cone, sphere) intersects any plane at all points.|
|Cylindricity – describes a condition of a rotating surface where all points of the surface are equidistant from a common axis of rotation.|
|Profile of a Line – a condition that allows the variation of a profile along a line element, either unilaterally or bilaterally.|
|Profile of a Surface – a condition that allows the variation of a profile along a line element, either unilaterally or bilaterally, on the upper surface.|
|Inclination – refers to a surface, axis, or centerline that deviates from a specified angle relative to a reference plane or axis.|
|Perpendicularity – a condition of a surface, axis, or line that is 90 degrees to a reference plane or axis.|
|Parallelism – a condition of a surface, line, or axis where all points are equidistant from a reference plane or axis.|
|Position Tolerance – defines a feature of size in an area that allows different true (theoretically exact) locations.|
|Concentricity – describes a condition where two or more features of a part, at any combination, have a common axis of rotation.|
|Symmetry – a condition where one or more features are symmetrically disposed about a center plane of symmetry.|
How to Create an Engineering Drawing
There are two primary methods for creating engineering drawings: manual drafting and computer-aided drafting (CAD).
Manual drawing involves using tools such as drawing boards, paper, rulers, calipers, and round gauges. This method is often employed in university courses to foster spatial imagination and conceptual skills, which are vital for nurturing creative thinking in students.
On the other hand, computer drawing, commonly implemented through CAD software, is better suited for modern manufacturing practices. In contemporary CNC machining centers equipped with computer numerical control (CNC) systems, data and information can be directly extracted from digital files to generate machining programs, significantly saving time and effort. Additionally, computer-based drawing simplifies the modification of designs, allowing for various versions to be stored and eliminating the labor-intensive process of manual drawing.
While 3D models are also applicable in machining processes, engineering drawings remain essential for conveying crucial details such as materials, tolerances, special requirements, and more. Our recommendation often leans toward using a combination of 3D models and engineering drawings to effectively communicate design specifications.
Engineering drawing is not merely a static representation. At KUSLA, our team of skilled engineers and machinists is proficient in analyzing every facet of engineering drawings, providing prompt Design for Manufacturability (DFM) feedback to guarantee the finest machined components. Take the next step by uploading your CAD files and receiving a quote today!