In this blog post, we’ll explore the basic concepts and importance of mechanical drafting—which every mechanical engineering student must master—as well as the relationship between manual drafting and CAD design.
What is the very first thing Tony Stark has to do when building the Iron Man suit in his cave? What is the very first thing freshmen learn when they enter the mechanical engineering department with excitement? It is mechanical drafting.
Mechanical drafting refers to the process of creating part drawings and assembly drawings using standardized methods. The reason it is taught first is not because it is easy, but because it is a fundamental skill that is absolutely essential not only during the four years of college but also in the industrial field after graduation. Among mechanical engineering students, some work in design, others in manufacturing, and still others in research on mechanical engineering theory. In the real industrial world, the fields that account for the largest share are design and manufacturing. Mechanical drafting can be described as the common language through which mechanical engineering students communicate with one another during the design and manufacturing processes. Designers must be able to accurately represent their designs in drawings, and manufacturers must read those drawings to create the actual products.
In the past, engineers drew blueprints by hand. Hand-drawn drafting requires the ability to draw various shapes using only a ruler and compass, and it is essential to strictly adhere to specific rules regarding the purpose of different line types and thicknesses, dimensioning methods, and the symbols used in drawings. Since mechanical drafting serves as a language in the mechanical engineering industry, these rules are of utmost importance. In South Korea, drafting is performed in accordance with Korean Industrial Standards (KS), which are established based on the International Organization for Standardization (ISO). Once you have thoroughly mastered these rules, you should be able to observe a real object and represent it in a drawing.
A projection drawing is a representation of an object on a plane that accurately depicts its visible appearance. Projection drawings include front views, top views, right-side views, left-side views, bottom views, and rear views; generally, front views, top views, and right-side views are used most frequently. A front view shows the object as seen from the front, while a top view shows it as seen from above. The standard procedure is to draw the front view first, followed by the right-side view and the top view. Projection drawings do not merely depict visible features with outline lines. If there is a cylindrical hollow space inside an object, hidden lines must be used to represent it.
A cross-sectional view depicts the cross-section that would appear if the object were cut open, rather than simply showing its visible appearance. In front and top views, hidden lines often need to be drawn as well; however, if there are too many hidden lines, the drawing becomes very complex. Cross-sectional views are used to solve this problem. Typical cross-sectional views include full-section views, single-side section views, and partial section views.
A full-section view is a method of depicting a cross-section by setting the cutting plane to pass through the entire object. In a full-section view, hidden lines are not shown, and the cut surfaces are represented by hatching. Hatching refers to the method of drawing diagonal lines in a specific direction to indicate cut surfaces. A single-side section view is used when an object is symmetrical vertically or horizontally. Because it utilizes the symmetrical structure, only a portion of the object is cut to show the cross-section, rather than cutting through the entire object. A partial cross-section is a method used to show the internal shape of a narrow section; the boundaries of the required area are marked with a thin solid line, and only that area is depicted as a cross-section. Cross-sectional drawings are a method for more accurately representing the internal structure of an object, and there are various other types, such as extracted cross-sections, rotational cross-sections, and rotational views.
Using computer software makes it much easier to draft the object you intend to create. “SOLIDWORKS” and “CATIA” are widely used as representative 3D CAD programs. The greatest advantage of these programs is their ability to support 3D design, though they also support 2D drafting. For example, when designing a mini car, rather than creating a single finished model all at once, each part is designed as a separate file and then assembled to complete the model.
Engineers who use CAD programs for drafting may find manual drafting cumbersome. This is because manual drafting requires a precise understanding of the rules; if even a single line is drawn incorrectly or specifications are applied incorrectly, the resulting product may differ from the designer’s intent. While using CAD can help reduce such errors, the process of learning the basic principles and rules of mechanical drafting through manual drafting remains crucial. A solid foundation in these basics is essential for producing more accurate and high-quality designs when using CAD software. Therefore, mechanical engineering students should thoroughly learn and practice manual drafting, which is the foundation of technical drafting.
